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Quality Manual Part - II
Guidelines on
Quality Control & Quality Assurance of
Ready-Mixed Concrete
Quality Manual Part - II
Guidelines on
Quality Control & Quality Assurance of
Ready-Mixed Concrete
Published by Ready Mixed Concrete Manufacturers’ Association (RMCMA)
2008.
Contact:
B-5, Ground Floor, Neel Shantiniketan Co-op. Housing Society, Manipada Road,
Opp. Mumbai University,Kalina, Santacruz (E), Mumbai 400 098,
Tel.: 91-22-26654165, E-mail: info@rmcmaindia.org Web: rmcmaindia.org
Copyright © 2008 Ready Mixed Concrete Manufacturers’ Association (RMCMA)
B-5, Neel Shantiniketan CHS, Opp. Vidyanagari,
Manipada Road, Kalina, Santacruz (E), Mumbai 400 098.
All rights reserved. No part of this publication should be reproduced, copied and distributed in any form
or by any means or stored in a data base or retrieval system without the prior written permission of
RMCMA.
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CONTENTS
Sr. No.
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2
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4
5
6
7
8
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10
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14
15
Description
Page No.
Foreword
Preface
The Quality Team
Acknowledgement
Message from NRMCA U.S.A
Message from ERMCO BELGIUM
Section I: Guidelines
What is Quality?
What are QA and QC?
Complexities in providing Quality Concrete
Company Information and Quality Policy
Management Responsibility and Commitment
QA-QC Plan
Sources of Materials
Monitoring Quality of Ingredients
Cement
Supplementary cementitious materials
Chemical admixtures
Water
Aggregates
Sampling and Testing of Concrete
Process Control
Upkeep of production facility
Concrete mix design
Control Charts
Properties of Fresh Concrete
Workability
Density
Temperature
Properties of Hardened Concrete
Strength
Standard deviation
Acceptance criteria
Special QC techniques
Internal quality audit report
Cusum system
4
6
8
10
11
12
Key Personnel
43
14
14
15
16
16
16
18
19
20
23
25
26
29
31
32
34
35
36
37
39
40
41
42
42
Section II: Typical example
1
Introduction
45
2
Tables and graphs
46-61
3
Bureau of Indian Standards referred in Guidelines
62
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FOREWORD
During the past decade, the construction industry in India witnessed remarkable
growth, in which the ready-mixed concrete (RMC) industry can claim to be a proud
partner. Historically speaking, India missed the benefits of RMC technology for
decades. It was only in the early nineties that the industry was born, but growth really
commenced from the second half of the nineties. During the past few years, housing
and infrastructure have remained the major expansion areas. Faster speed and improved
quality of concrete have been the two major demands of these sectors. Ready-mixed
concrete was the right solution for this and it was heartening to see that the RMC
industry responded positively to these demands. The result was the rapid growth of the
RMC industry. This industry, which was initially confined to metropolitan cities, later
spread to the two-tier and three-tier cities, vindicating the fact that RMC was a right
solution for different markets. Currently, it is estimated that India produces around 2025 million m 3 of concrete annually from around 400-500 RMC facilities.
The growth of the RMC industry brought in its wake certain challenges, chief amongst
which was about the quality of concrete supplied by RMC plants. In this context, we
are happy that the RMC industry came forward and has tried to evolve a self-regulatory
framework for this. It is our pleasure to be associated with this exercise, spearheaded
by the Ready-Mixed Concrete Manufacturers’ Association (RMCMA). The exercise
involved in-depth study of the regulatory practices in different countries, choosing the
best international practices, aligning the regulatory framework with the provisions in
the current codes of the Bureau of Indian Standards, evolving a system of audit of
RMC facilities by external auditor, developing guidelines for the quality control and
quality assurance of the final product, etc. We were happy to be actively involved
during all these stages and could provide guidance to the RMCMA’s Quality SubCommittee from time to time. The Quality Scheme of RMCMA is contained in two
meticulously-prepared manuals, namely Quality Manuals Part I and II, which were
finalized after thorough discussion and revisions. While Quality Manual Part-I
incorporates an extensive Check List to be used for auditing RMC facility, procedures
of audit, etc., Quality Manual Part-II contains guidelines for QA & QC of concrete,
which are based on key provisions in different BIS codes. It is noteworthy that
conformity with the Quality Manual-Part I through annual external audit of RMC
facility is made mandatory for obtaining a RMCMA certification.
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It is heartening to note that the regulatory framework for quality is in place, the
Quality Manual Part I and II have been finalized and that audits of nearly 50 RMC
facilities located in different parts of the country have been successfully completed
by external auditors till October 2008. Improvements in quality have to be a
continuous process and hence the national Experts Committee would be reviewing the
performance of the present Quality Scheme from time to time and would incorporate
changes in its provisions, if necessary.
We are of the opinion that a good beginning has already been made and everyone
associated with construction needs to support this initiative from the RMC industry.
We trust that these documents will become the cornerstone of high-quality concrete
manufacturing. We are confident that alignment with these documents will ensure a
healthy growth of the RMC industry in India.
For and on Behalf of the National Experts Committee
Dr. A. Ramakrishna
(Advisor, Larsen & Toubro Ltd.)
Dr C. S. Viswanatha
(Managing Director, Torsteel Research Foundation in India, Bangalore)
Mr. Jose Kurian
(Chief Engineer, DT & TDC, New Delhi)
Dr A K Mullick
(Former Director General, National Council for Cement and Building Materials
(NCB), New Delhi)
Mr. A. K. Jain
(Technical Advisor, Grasim/ UltraTech Cement)
Mr. P L Bongirwar
(Former Dy. Managing Director, MSRDC, Mumbai)
Mr. C M Dordi
(Customer Support Group Head (West and Exports), Ambuja Cements)
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PREFACE
The first commercial ready-mixed concrete (RMC) facility in India was set up in Pune in 1992 and was
followed by establishment of similar facilities in Mumbai, Bangalore, Chennai, Delhi, etc. The growth of
the construction industry, particularly the rapid expansion of the housing and the infrastructure sectors,
placed heavy demand on speed as well as quality in concrete construction. This gave an impetus to the
growth of RMC industry, which took roots mainly in the urban and semi-urban areas of the country.
Exact data on the growth of RMC industry is not available; however, it is estimated that India produced
more than 25 million m3 of ready-mixed concrete in 2007-08 from around 400-500 RMC facilities and
the number has been growing continuously.
The spread of RMC facilities in urban India has brought in its wake certain challenges. Since RMC is not
a finished product and the quality of the final product is dependent upon a host of factors ― some of
which are beyond the control of the RMC producers― there is likelihood of a variation in the uniformity
and quality of the final product. Yet, the customer needs to be provided with some sort of quality
assurance about the concrete supplied. This highlighted the need of developing a framework of quality
for RMC.
The Ready Mixed Concrete Manufacturers’ Association (RMCMA), India, which was established in
March 2002 and has been striving hard to bring the Indian RMC industry at par with the industries in
advanced countries, has taken up this challenge. After an in-depth study of the prevailing quality systems
in different parts of world, mainly from the U.S.A.,U.K., Canada, the RMCMA decided to develop a selfregulatory framework for Quality of RMC. It formed a Sub-Committee on Quality, consisting of
experienced quality personnel from member companies. Further, a committee of National Experts was
also set up. The Quality Sub-Committee, which worked under the guidance of the National Experts
Committee and the Managing Committee of RMCMA, put in Herculean efforts to evolve Quality
Scheme for RMC in India.
The Quality Scheme has been developed in two parts and the details are contained in two manuals,
namely, “Quality Manual Part I and Part II”. Both manuals have been developed after extensive
deliberations in the Quality Sub-Committee and also in the joint meetings of the entire Quality Team.
The drafts of the Quality Manuals Part I and II were modified on several occasions.
The first part of the scheme essentially consists of an annual audit of RMC facility by an external auditor.
The audit is based on an extensive Check List included in Quality Manual Part I. While developing the
Check List, it was ensured that the provisions in the same meet most of the stipulations in the Indian
Standard on Ready Mixed Concrete, IS 49263 (second revision) and the other relevant codes on concrete
such as IS 4561, IS 91032 and many others. In fact, the requirements of the Check List, in some cases,
exceed those of the codes. Thus, RMCMA certification through the external audit would provide
assurance to the users that the production facilities of the certified plant conform to the requirements of
the IS code. Before the Check List was finalized, mock audits of number of RMC facilities were
conducted by selected members of the Quality Sub-Committee and the Check List provisions were
modified after gaining practical experience. Incidentally, the Quality Manual Part I also includes the
detailed procedure of audit, detailed procedure of audit, selection criteria of auditors, sample certificate,
selection criteria of auditors, sample certificate, etc. It may be Emphasized that successful completion of
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external annual audit is mandatory for obtaining RMCMA certification However, it needs to be pointed
out that availability of proper plant and equipment is only one of the factors — although a very vital one
— that controls quality of concrete. No claim is therefore made that certification of RMCMA will
necessarily assure delivery of high quality concrete. The RMCMA certificate should therefore be
accepted precisely for what it is — evidence that a certified production facility do possess capabilities to
produce quality concrete. The existence of these capabilities is likely to reduce the incidence of
deficiencies in the quality of final product.
The Quality Team seriously deliberated on the issue of product certification too. It was felt that quality of
the product involves contractual issues between the RMC producer and his/her clients. Further, different
member companies follow different quality practices and are in competition with each other on quality
parameters. The Quality Team therefore felt that product quality cannot be brought under certification at
the current stage; instead, it was decided that the RMCMA should develop a Guideline document on QA
and QC of Concrete for its member companies. The Quality Sub-Committee prepared the draft guidelines
which were deliberated in various meetings and several improvements were made based on the guidance
provided by the National Experts. It is recommended that each RMC facility should prepare its own QC
Manual II following the minimum benchmarks suggested in the guideline document. Such document,
which incidentally needs constant updating, would demonstrate RMC producer’s commitment to quality
concrete.
The external audits of RMC facilities of member companies commenced in March 2008 and we are
pleased to inform that till October 2008, more than 50 RMC facilities from different parts of the country
are successful in obtaining certification. The list of these facilities as well as the names of the auditors
who audited these facilities is available at www.rmcmaindia.org.
The Quality Team of RMCMA will continuously review the progress in the implementation of the
Quality Scheme. It would be open to constructive suggestions and based on the feedback from field,
would modify the provisions in the Quality Manual Part I and II, if found necessary.
The RMCMA has developed close ties with the National Ready Mixed Concrete Association (NRMCA),
U.S.A and the European Ready Mixed Concrete Organization (ERMCO). We are happy to inform that
these leading world organizations are supportive of the efforts being made by the RMCMA in developing
the quality scheme. We are pleased to enclose the messages of appreciation from these organizations.
The Quality Team of RMCMA strongly believes that the self-regulatory quality framework initiated by
the RMCMA would go a long way in improving the quality of concrete produced by RMC plants and
providing assurance to customers.
For and on Behalf of Quality Sub-Committee
(Vijay R. Kulkarni)
Convener,
Quality Sub-Committee, RMCMA
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THE QUALITY TEAM
National Experts Committee
•
•
•
•
•
•
•
Dr. A. Ramakrishna- Advisor, Larsen & Toubro Ltd.
Dr C. S. Viswanatha, Managing Director, Torsteel Research Foundation in India, Bangalore
Mr. Jose Kurian- Chief Engineer, DT & TDC, New Delhi
Dr A K Mullick, Former Director General, National Council for Cement and Building
Materials (NCB), New Delhi
Mr. A. K. Jain- Technical Advisor, Grasim/ UltraTech Cement
Mr. P L Bongirwar- Former Dy. Managing Director, MSRDC, Mumbai
Mr. C M Dordi- Customer Support Group Head (West and Exports), Ambuja Cements
RMCMA’s Sub-Committee on Quality
•
•
•
•
•
•
•
•
•
•
•
•
Vijay R. Kulkarni, Convener, Quality Sub-Committee, RMCMA
Mr. Rajiv Talwar, Head QA, ACC Concrete Ltd.
Dr. P. Dinakar, ACC Concrete Ltd (From inception till December 2007)
Mr. Harpal Singh Sehmi, ACC Concrete Ltd (From inception till June 2007)
Mr. Anuj Maheshwari- Head, Technical, Grasim Industries Ltd.
Mr. S. G. Bhat, Manager QC, Lafarge Aggregate & Concrete Pvt. Ltd.
Mr. Hiren Joshi., QA-QC In-charge, Lafarge Aggregate & Concrete Pvt. Ltd.
Mr. S. D. Govilkar, Deputy General Manager(Technical), RMC Readymix (I)
Pvt. Ltd.
Mr. Girish Bonde, Head, Technical, RDC Concrete India Pvt. Ltd.
Mr. Bilal Baig, Manager, Quality, Godrej & Boyce Mfg. Co. Ltd.
Mr. Awadhoot Sawant- Dy. Manager RMC, Godrej & Boyce Mfg. Co. Ltd. (From inception
till Nov. 2007)
Mr. D. Mohan, Manager Technical, IJM Concrete Products Pvt. Ltd.
RMCMA’s Managing Committee
•
•
•
•
•
•
•
•
Mr. Ganesh Kaskar, President, RMCMA & Ex. Dir. and CEO, RMC Readymix (I) Pvt. Ltd.
Mr. Hans Fuchs, Vice-President, RMCMA and Managing Director, ACC Concrete Ltd.
Mr. Racy Sidhu, Vice-President, RMCMA and BU Manager-RMC, Lafarge Aggregate &
Concrete Pvt. Ltd.
Mr Vivek Agrawal, .Ex. President, Grasim Industries Ltd.
Mr. B K Shrikhande, Former Vice-President, ACC Concrete Ltd. ( from inception till
October 2007)
Mr. Sanjay Bahadur, Former Managing Director, ACC Concrete Ltd.
(from Nov. 2007 to June 2008)
Mr.Akash Gonge, Secretary, RMCMA, and General Manager (RMC), Godrej & Boyce Mfg.
Co. Ltd.
Mr S.R. Kumar, Immediate Past President, RMCMA ( from inception to August 2008)
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•
•
•
•
•
•
Mr Uday Shankar, Ex. Director, RDC Concrete India Pvt. Ltd.
Mr. R Krishnachander, Vice-President-Business Development, India Cements Ltd.
Mr. Balaji Moorthy, President-Marketing, Madras Cement Ltd.
Mr. Prakash Menon, General Manager, IJM Concrete Products Pvt. Ltd.
Mr. M A Mathew, Proprietor, MC Duramix
Mr. Vijay R. Kulkarni, Principal Consultant, RMCMA
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ACKNOWLEDGMENT
We are grateful to each member of the RMCMA’s Sub-Committee on Quality for carefully scrutinizing
different provisions in Quality Manual Part I and II. The provisions were thoroughly discussed in the
meetings of the Sub-Committee and several modifications were made after reaching broad consensus.
The help rendered by Sub-Committee members is highly appreciated and we are thankful to them for
their involvement and efforts.
We are also indebted to all members of the National Experts Committee and the Managing Committee of
RMCMA who have provided broad guidance on different aspects of the provisions in both manuals.
They not only carefully scrutinized the provisions in the Manuals but also helped the RMCMA in
finalizing its approach to the Quality Scheme by offering valuable suggestions. The RMCMA would like
to record its deep sense of gratitude towards the members of the Experts Committee for their valuable
guidance.
The Quality Team would also like to thank the National Ready Mixed Concrete Association (NRMCA),
U.S.A., particularly, Mr. Robert Garbini, President and Dr Colin Lobo, Senior Vice-President
(Engineering), for the help rendered in providing guidance on the quality practices followed by NRMCA.
We are also thankful to the European Ready Mixed Concrete Organization (ERMCO) for the support
rendered to us.
For and on Behalf of Quality Sub-Committee
(Vijay R. Kulkarni)
Convener,
Quality Sub-Committee, RMCMA
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Section I: Guidelines
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1. What is Quality?
1.1 The term quality has been defined differently by different experts. For example, Deming defines it
“Meeting the customers’ needs”; Juran says it is “Fitness for use”, whereas Crosby defines it as
“Conformance to requirements”. One more definition of quality can be “Satisfaction of stated and
implied needs”. Quality can have separate meaning. It can have subjective meaning, when it is used
to indicate elegance or luxury. Quality can be relative, when the term is used to indicate grade (e.g.
5-star hotel). It can have objective meaning when it is used to indicate a specific requirement or
fitness for purpose (e.g. M30/M40 grade of concrete).
1.2 The term quality has a much wider and an all-encompassing significance when applied to any multidimensional activities. In the context of construction industry, quality is the slated and implied needs
of the users/owners — who should be assured of the required serviceability and safety, without
undue maintenance — but also the slated and implied needs of the client/promoters who should be
assured of adequate returns on their investments. Quality in construction can be said to have been
achieved if it is completed without time and cost overruns, ensuring the required serviceability,
durability and safety, without undue maintenance.
2. What are QA and QC?
2.1 In the literature on quality, one would often notice the use of two terms, namely, quality control
(QC) and quality assurance (QA). In day-to-day practice, there is a tendency to use these terms
imprecisely. It would therefore be appropriate to have clarity about the exact meaning of these
terms..
2.2 Quality control (QC), sometimes called process control, is defined as “the operational techniques and
activities that are used to fulfill requirements of quality”. It is the sum total of activities performed
by the seller (producer) to make sure that a product meets contract specifications and requirements.
QC is often confused with control testing. The basic quality control concept, as promulgated by Prof.
Juran, is to “control the mass and not the piece”. The main problem about quality control is that it is
an “after event” operation, designed to prevent defective items from passing through the system.
What happens when a product fails? The consumer’s risk is that a bad batch may get accepted, while
the producer’s risk is that a good batch may be rejected. This gave rise to the concept of quality
assurance (QA).
2.4 Quality assurance (QA) can be defined as all those planned activities and systematic actions
necessary to provide adequate confidence that a product or service will satisfy the given contractspecific requirements. Quality assurance provides consistency and an assurance (in the form of
certified records) that the established QC procedures have been carried out in full. Thus, quality
control is part of quality assurance. Within an organization, quality assurance serves as a
management tool; in contractual situations, quality assurance serves to provide confidence in the
supplier.
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3. Complexities in providing Quality Concrete
3.1 As regards ready-mixed concrete (RMC), the problem of providing QA and QC becomes more
complex. This is because RMC is an unfinished product at the time of delivery. In its “as sold”
condition, the product is perishable and will not remain in plastic and unhardened condition beyond
a limited time. Construction materials like steel, aluminum, glass, etc are factory-produced finished
products and the producers are in a position to control its final quality before delivery. This is not the
case with ready-mixed concrete. The quality of finished concrete is affected by a host of factors such
as:
•
•
•
•
•
•
variability in the quality of the different ingredients such as cement, aggregates, sand, water
and mineral and chemical admixtures,
selection of ingredients which depends up on the end use and client’s requirements,
proportions of ingredients,
a variety of process parameters, affecting homogeneity of mixing and other properties,
conditions involving transportation, placement, finishing, curing and protection of concrete,
variation in external environmental conditions such as changes in temperature, humidity and
wind speed, which can adversely affect the properties of concrete.
3.2 The main quality parameters of concrete are its workability, homogeneity and compactibility at pour
site, 28-day compressive strength and long-term durability. Amongst these parameters, durability is
indirectly controlled by adopting certain code-specified limiting norms, e.g. minimum cementitious
content, maximum free water-binder ratio, minimum grade of concrete, etc (for example, Tables 3
and 5 of IS 456 2). The workability at pour site, which is usually measured in terms of slump, is
affected by numerous factors and the RMC producer has to take proper precautions to maintain the
desired values of slump at pour site, making use of his expertise and experience, especially when the
weather conditions are harsh and there could be bottlenecks in transportation, involving long delays.
The specified compressive strength of concrete cannot be verified at the time of sale, as an
overwhelming majority of the contracts are based on the 28-day strengths.
3.3 Thus, providing quality concrete on a consistent basis is indeed a complex job. With a view to tide
over this complexity, RMC producer needs to be committed to well-organized quality control and
quality assurance systems. This Guideline document along with the interrelated document (QC
Manual Part-I) provide necessary tools which can be used by RMC producers to produce quality
concrete on a consistent basis. It may be mentioned here that QC Manual Part-I contains a
comprehensive Check List, based on which audit of the production facility by external auditor
should be organized each year through the good offices of RMCMA. Such audit, which provides
assurance to the customers that the tools available with the RMC producer are capable of producing
quality concrete, is mandatory to obtain certification from RMCMA. Since product quality is
governed by contractual agreement between the producer and the client and each company follows
different system of controlling quality of its own products, it was felt that audit based on the
Guidelines suggested in the Part-II of this Manual would not be possible and hence not proposed.
Yet, it is strongly recommended that each RMC facility should prepare its own QC Manual
following the minimum benchmarks suggested in this document. Such document would demonstrate
RMC producer’s commitment to quality concrete.
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3.5 This Guideline document recommends a broad framework of QA and QC which is strongly
recommended for adoption by RMC producers. It is believed that adoption of the guidelines would
help RMC producers in establishing his own system that would provide assurance of his capabilities
in producing quality concrete on a consistent basis.
4. Company Information and Quality Policy
4.1 The Guideline provides an opportunity for each Company to describe its background, organizational
structure, its products and services, mission statement, quality policy, etc. Thus, when preparing its
own QC Manual, it I suggested that the following information may be incorporated in the same:
• brief history of the Company
• growth trends of the Company including some its recent initiatives
• geographical locations of its production facilities
• description of products and services
• any additional information that the Company may perceive to be beneficial
4.2 Many companies have well-defined “Mission” and “Vision”, embodied in Company statements. It
would be most appropriate to include such statements in the QC Manual. Further, many companies
have a clear-cut “Quality Policy”. In case such policy has already been evolved, the same should be
included in the QC Manual. In fact, incorporation such policy in the QC Manual would be welcomed
by customers.
5. Management Responsibility and Commitment
5.1 The production of concrete having consistent quality demands involvement and commitment from
all those connected with the production process, either directly or indirectly. Quality is not merely
the concern of the QC department; it is the concern of everyone involved in the process — the
marketing personnel who book orders and keep in touch with customers, the procurement personnel
who procure different ingredients of concrete as well as equipment, production personnel involved in
producing concrete as per the recipe agreed upon, and the QC team involved in testing, mix
proportioning, monitoring and analyzing test results. Implementation of quality system often leads to
reduction in the rate of failures, which can translate in to reduction in cost for the producer.
However, for this to happen, everyone needs to be committed to quality. In particular, what is
important is the commitment and willingness of the top management of the Company to maintain
product quality regardless of the competitive pressures. The responsibilities of management
personnel as well as their authorities should be clearly spelt out.
6. QA-QC Plan
6.1 This document suggests that each RMC production facility should establish its own QA-QC Plan, for
which these guidelines can serve as a basis. It is emphasized that the guidelines can be treated as
minimum benchmarks. Different RMC production facilities certainly have the freedom to excel
beyond the minimum benchmarks. In fact, if the publication of these benchmark guidelines results in
the emergence of a true competitive spirit amongst different RMC production facilities, and they
start competing with each other by excelling the given benchmarks, customers would be the final
beneficiary.
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6.2 It is suggested that the QC Plan should have the following elements:
o Management of the quality of ingredients:
o Sources/location of different materials
o Crucial tests and testing frequencies for different ingredients for monitoring their quality
o Process Control
o Inspection and checking of different components of plant and other equipment and their
frequency
o Concrete mix design: Data on laboratory and plant trials
o Sampling of concrete
o Properties of fresh concrete
o Data on slump, temperature, density,
o Properties of hardened concrete
o Data on compressive strengths of concrete at various ages; flexural strength (whenever
specified)
o Acceptance criteria
o Standard deviation
o Special QC techniques
o Internal quality audit
o Special techniques
o Key personnel:
o Data pertaining qualification, experience, and training of all personnel involved in
production, quality control, marketing, etc.
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7. Sources of Materials
7.1 RMC supplier would prefer to have the same source for the materials used in day-to-day production.
This is because a change in the source of the material may affect its properties and hence would
warrant re-proportioning/redesigning of mixes, which is a time-consuming process. Therefore, RMC
supplier would always try to avoid frequent changes in the sources of materials. However, a variety
of factors such as shortage in the supply of materials, environmental restrictions on dredging and
mining, transportation bottlenecks, abnormal increase in the cost of material from a particular source,
etc. compel the RMC producer to make changes in the sources of input materials. Considering this, it
would be advisable to document the sources of all ingredients used in production. In case of any
quality problems, such documentation would be quite useful in tracking faulty materials sources, if
any. Table 1 suggests the format for such documentation.
Table 1: Sources of different materials, and their period of use
Material
Type/
Class
Source
Name of Supplier/
Factory/ brand
OPC
43 grade
53 grade
Cement
PPC
PSC
Other
Fly ash
Siliceous
Calcareous
Slag
Silica fume
Water
Ice
Fine aggregate
River sand
Manufactured sand
Coarse
aggregate
40-mm down
25-mm down
12.5-mm down
Quarry fines
W.R. Agent
H.R.W.R.A.
Retarder
Others
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Location
8
Monitoring Quality of Ingredients
8.1 Cement
8.1.1 RMC producers in India commonly use three types of cements, namely,
•
•
•
Ordinary Portland cement (OPC)
o 43 grade conforming to IS 81123
o 53 grade conforming to IS 122694
Portland Pozzolana Cement (PPC) conforming to IS 14895
Portland Slag Cement (PSC) conforming to IS 4556.
8.1.2 Although cement is a factory-produced material, there may be variation in the properties between
two consignments, even from the same factory. RMC producers usually prefer to have a long-term
understanding with a particular cement producer. However, at times, they are constrained to use
different brands from different manufacturers. Since the properties of the cement have close
bearing on the properties of concrete, it would be appropriate to document the key physical
properties of cement. Fortunately, most of the cement manufacturers do provide a test certificate on
the properties on a regular basis, enabling documentation of such properties. Some RMC producers
have facility for testing certain key physical properties of cement in their central laboratory. If such
a facility is in use or in case RMC producers get the cement samples tested from a third-party
laboratory, the results should be appropriately documented. Table 2 provides a format for such
documentation. The table also includes the minimum and maximum provisions from the relevant
Indian codes for the sake of immediate comparison.
Table 2: Selected physical properties of cement
Property
Date of testing
Type of cement
Fineness, m2/kg
Manufacturer I
Manufacturer II
Manufacturer III
PPC
Test
Provisions of
results*
IS 14895
OPC 53 grade
Provisions
Test
of IS
results*
122694
225 (min)
PSC
Test
Provisions of
results*
IS 4556
300 (min)
225 (min)
Min. compressive strength, MPa
3-day
16
27
16
7-day
22
37
22
28-day
33
53
33
Setting time, minute
Initial
30 (min)
30 (min)
30 (min)
Final
600 (max)
600 (max)
600 (max)
Soundness, mm
10 (max)
10 (max)
10 (max)
Loss on ignition, %
% of mineral admixture (fly ash
or slag) in PPC or PSC
4 (max)
15-35 %
fly ash
-
35-70 % slag
* Based on data from manufacturer’s certificate or in-house testing or testing done in a third-party lab.
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8.2
Supplementary Cementitious Materials
8.21
RMC producers generally use the following three types of supplementary cementitious materials
(SCMs):
•
•
•
8.22
Fly ash,
Ground granulated blast furnace slag (GGBS),
Condensed silica fume.
It is well known that SCMs, possessing either pozzolanic or latent hydraulic properties, improve a
host of properties of concrete, both in its fresh and hardened states. In particular, the use of these
materials improves the workability and helps concrete in achieving higher long-term strength gain
and improved durability leading to enhanced sustainability. However, these benefits would be
achieved only when it is ensured that the SCMs possess the requisite properties; otherwise, they
may just act as inert fillers. For RMC producer, the best way to ensure this is to verify as to
whether the physical and chemical properties of the SCM used conform to the code-specified
requirements.
While fly ash and condensed silica fume should respectively conform to IS 3812
153888, GGBS should conform to IS 12089 : 19879 and BS 6699.
8.2.1
(Part 1)7 and IS
Fly ash
8.2.1.1Fly ash or pulverized fuel ash (PFA) is a by-product from thermal power plants. Depending on the
type of coal used for burning, fly ash could either be of silicious variety (produced from bitimunous
coal and having CaO < 10%) or calcareous variety (produced from lignite coal and having CaO >
10%). While finely-divided silicious fly ash has pozzolanic nature, the calcareous fly ash has both
pozzolanic and hydraulic properties. However, not all fly ashes available from thermal power
plants can be suitable for use in concrete. If fly ash is obtained from the same source, there will not
be much variation in the chemical properties of fly ash; however the physical properties may vary
depending upon the collection and separation and grinding system used. The IS 38127 has
stipulated certain minimum physical and chemical requirements. RMC producer needs to ensure
that the fly ash received by him has supplementary cementitious properties. It would therefore be
appropriate if the fly ash supplier furnishes a test certificate along with each consignment.
8.2.1.2Before the source of the fly ash is fixed, it is essential that all the physical and chemical
requirements as given in IS 38127 are complied with. Once the source is fixed, only the physical
requirements of fly ash need to be monitored. Amongst the various physical requirements
mentioned in Table 3, the requirement of particles retained on 45 µ sieve can be assessed quickly by
wet sieving test. It would therefore be a good practice to carry out this test in the in-house
laboratory before each consignment is accepted. It is suggested that the remaining four physical
requirements, namely Blaine’s fineness, lime reactivity, 28-day compressive strength and
soundness, should be checked once in 3 months or with the change in source.
8.2.1.3With a view to control the consignment-to-consignment variation in the quality of fly ash, IS 38127
also specifies uniformity requirements. It specifies that individual values of tests at Sr. No. 1 to 3 in
Table 3 shall not vary more than 15% from average established from the tests on the 10 preceding
samples or of all samples if less than 10. RMC producer should ensure that the uniformity
requirements are strictly followed. The format given in Table 3 could be useful for this purpose.
- 20 -
Table 3: Physical requirements of fly ash conforming to IS 38127 and results of selected tests on samples
Sr.
No.
Property
IS
Requirements
Frequency of test
suggested by
RMCMA
1
Particles retained on 45 µ
sieve *
34% (max)
Each consignment
2
Blaine's fineness, m2/kg #
320 (min)
3-monthly/ change
of source
3
Lime reactivity, MPa#
4.5 (min)
3-monthly/ change
of source
4
28-day compressive strength,
MPa #
Not less than
80% of
control
3-monthly/ change
of source
5
Soundness, % #
0.8 (max)
3-monthly/ change
of source
Sample 1
Date
Sample 2
Test report
Date
Test report
* Test conducted on each consignment before acceptance
# Based on data furnished by supplier by conducting tests in a third-party lab.
8.2.2 Ground-granulated blast-furnace slag (GGBS)
8.2.2.1Ground-granulated blast-furnace slag possesses latent hydraulic properties. For the use of GGBS as
a mineral admixture in concrete, no Indian code is available. However, specification for granulated
slag for manufacture of Portland slag cement is available (IS 120899). It is therefore suggested that
while the physical requirements of GGBS could be in accordance with BS 6699, the chemical
requirements could be in line with the Indian code IS 120899. Some of the crucial properties as
specified in BS 6699 and IS 120899 are given in Table 4. RMC producer needs to ensure that the
supplier gives test certificate satisfying the requirements given in Table 4.
Table 4: Properties of GGBS conforming to BS 6699 and IS 120899 and results of selected
tests on samples
Property
BS
Requirements
Sample 1
Date
Blaine's fineness (as per BS 6691)
275 m2/kg (min)
Compressive strength, ( as per BS 6691)
7-day
28-day
12.0MPa
32.5 MPa
Initial setting time( as per BS 6691)
Not less than
IST of OPC
Soundness (Le-Chatellier expansion)
(as per BS 6691)
10 mm (max)
Glass content (as per IS 120899)
85 % (min.)
* Based on data furnished by supplier by conducting tests in a third-party lab.
- 21 -
Test
report*
Sample 2
Date
Test
report*
8.2.3
Condensed silica fume
8.2.3.1 Condensed silica fume, also known as micro silica, is a by-product of silicon and ferro-silicon
industry. It is an extremely fine material, having specific surface value greater than 15,000
m2/kg.The amorphous silica content should be more than 85%. It is a highly reactive pozzolana.
8.2.3.2 Silica fume should conform to the requirements of IS 153888, which specify the physical and
chemical properties. Table 5 gives some of these crucial properties. With a view to ensure supply
of good quality silica fume, RMC supplier needs to obtain test certificates from his supplier for
each lot of materials that he receives and document the results in the format given in Table 5.
Alternatively, it may be a good practice to send a random sample of silica fume to a third-party
laboratory and cross check the results obtained with those furnished by the supplier.
Table 5: Properties of condensed silica fume conforming to IS 153888 and results of selected
tests on samples
Property
IS 15388 8
Requirements
Sample 1
Date
Specific surface, m2/kg
15,000 (min)
SiO2 content
85% (min.)
Pozzolanic activity index
85% at 28 days
Moisture content
3% max.
LOI
6% max.
Test
report*
Sample 2
Date
Test
report*
* Based on data furnished by supplier by conducting tests in a third-party lab.
8.2.4 High reactivity metakaolin (HRM)
8.2.4.1Besides fly ash, GGBS and condensed silica fume, RMC producers can also use another SCMs,
namely high reactivity metakaolin (HRM). HRM is obtained by calcination and grinding of pure
or refined clay at a temperature between 650-850O C. IS 4562 permits the use of this material as
SCM. However, since no Indian standard is available on this material, it would be advisable to
refer to the relevant literature on the subject and get the approval of the client/consultant about the
quality of the material before use.
- 22 -
8.3
Chemical admixtures
8.3.1 Ready-mixed concrete needs to be transported over long distances and it needs to be workable to
enable proper placement, compaction and finishing. Therefore, use of chemical admixtures,
which modify a variety of properties of concrete in its fresh and hardened states, becomes vital. In
typical tropical weather conditions prevalent in most part of India, the commonly used admixtures
are plasticizers, superplasticiser, and retarders.
8.3.2 Before selecting any brand of admixture, laboratory tests are carried out by RMC producer to
establish compatibility of cement-plasticizer/superplasticiser system and also to determine the
optimum dosage of admixture, initial slump, extent of slump retention with time, and compressive
strengths at various ages as percent of control sample etc. Any adverse effects, e.g. abnormal
slump loss, excessive retardation, increased air content, bleeding, etc., observed during these trials
should be meticulously documented. Table 6 provides the format for documenting the results of
laboratory trials. Incidentally, close liaison with admixture manufacturer is essential during these
tests. Once the laboratory trials are over, plant trails may also be carried out. With this, the type of
admixture and dosage requirements for different mixes can be frozen. Slight changes in the
dosage are made by RMC producer, depending upon the conditions of placement, likely delay in
transportation, etc. In case there is any change in the sources of materials, the whole exercise of
laboratory trails needs to be repeated. In particular, when the source of cement is changed it may
be essential to carry out compatibility trails again. The chemical admixtures used should conform
to the requirements specified in IS 910310.
Cement-chemical admixture or cement-chemical-mineral admixture compatibility needs to be
resolved during the selection of chemical admixture. For this purpose, help can be sought from
chemical admixture manufacturer. RMC producer too can carry out certain compatibility tests
(Marsh cone or mini-slump cone test) in the plant laboratory and keep the records. The latter
would be useful in case certain compatibility problems are noticed.
- 23 -
Table 6: Results of initial laboratory trials* on chemical admixture
Property
Control
concrete
Concrete with admixture
Manufacturer Manufacturer Manufacturer
I
II
III
Adverse effects, if any,
observed during trials
Name of manufacturer
Name of brand
Generic type
Water content, % of control
sample
Slump
0 min
30 min
60 min
90 min
Setting time, minute
Initial
Final
Compressive strength, % of
control sample
1-day
3-day
7-day
28-day
Air content, % max over
control
Observations on cementadmixture compatibility, if any
* Laboratory trials can be conducted in plant lab or in a third-party lab (in case facilities are not available in-house)
8.3.3 Admixtures are supplied in large drums. For each batch of admixture the manufacturer needs to
provide certificate as per Para 10.1 and 10.2 of IS 910310, giving various properties of the
material. The RMC producer should ensure that the material supplied to him matches closely with
the one supplied during laboratory trails. It is quite likely that there is variation in the quality of
the material being supplied from time to time. To verify this, IS 4562 recommends that the
relative density of admixtures shall be checked for each batch and compared with the specified
value before acceptance. This practice should be followed.
8.3.4 In addition to this, IS 910310 specifies four more uniformity tests to be carried out on admixtures,
Table 7. It may be advisable to get these tests carried out by an independent laboratory and the
values so obtained may be compared with those furnished by the manufacturer. IS 910310 does
not specify the frequency at which the testing for uniformity can be done. The guideline
document however suggests the frequency for the tests as mentioned in Table 7. A record of the
test results shall be kept as per the format suggested in this Table.
- 24 -
Table 7: Uniformity requirement of admixtures conforming to IS 910310 and results of selected tests on
samples
Sr.
No.
Uniformity test
Requirements as per IS 910310
1
Relative density
Within 0.02 of the value stated by the
manufacturer
2
Dry mat. content of
admixture
Liquid
0.95 T ≤ DMC ≤ 1.05 T where, T =
Manufacturer’s stated value in % by mass
DMC= Test result in % by mass
Solid
3
Ash content
0.95 T ≤ AC ≤ 1.05 T
Suggested
frequency
Sample 1
Date
Test
report
Sample 2
Date
Test
report
Every batch/
consignment
Each new batch
before acceptance
-
where, AC= Test result in % by mass
4
Chloride ion content
Within 10 % of the value or within 0.2 %,
whichever is greater as stated by the
manufacturer
Each new batch
before acceptance
5
pH
6 (min.)
Each new batch
Note: While the test at Sr. No. 1 can be done on each batch/consignment of admixture, the remaining tests mentioned at Sr.No. 2 to 5 can be
done in a third-party lab by the supplier and results furnished to RMC producer.
8.4
8.4.1
Water
Water used for mixing shall be potable in nature and free from oils, acids, alkalis, salts, sugar,
organic materials or any other substances that may be deleterious to steel or the concrete.
Permissible limits of impurities in water are specified in IS 4562 (Table 8). Mixing and curing
by sea water is not recommended because of the presence of harmful salts in sea water.
Table 8: Permissible limits for solids and results of tests on samples of fresh and recycled water
Sr.
No.
Solids
Permissible
limits as
specified in IS
4562, max., mg/l
1
Sulphates as SO3
400
2
3
Chlorides as Cl
Reinforced
concrete
pH
500
Not less than 6
4
Organic
200
5
Inorganic
3000
6
Suspended matter
2000
Fresh water
Sample 1
Sample 2
Date
Test
Date
Test
report
report
Recycled water
Sample 1
Sample 2
Date
Test
Date
Test
report
report
Note: While the tests mentioned at Sr. No. 1, 2 and 3 can be done quickly at plant with the help of a ready-made kit, the remaining tests (Sr.
No. 4, 5 and 6) can be done in a third-party lab at the frequency suggested in IS 49261
- 25 -
8.4.2
IS 49261 specifies different testing frequencies for mains water and non-mains water. For mains
water, the code specifies that testing should initially be done weekly, till six results are obtained,
after which testing can be done at three-month interval. For non-mains water, once the source is
found satisfactory, testing frequency should be on annual-basis, provided that the chloride ion
content does not exceed 0.01%; if the value exceeds this limit, the interval of testing shall be
reduced to three-monthly interval.
8.4.3
The use of recycled wash water needs to be encouraged from sustainability perspective.
However, RMC producer needs to ensure that concrete having satisfying performance is
produced with recycled water and that the permissible limits of total chloride and sulphate
contents are not exceeded. Incidentally, the test on sulphate and chloride contents and pH can be
conducted quickly with the help of a ready-made kit. Other tests (organic, inorganic matter and
suspended matter) can be done in a third-party lab at the frequencies suggested in IS 49261.
8.4.4
It is suggested that documentation of test results on water should be as given in Table 8.
8.5
Aggregates
8.5.1
Aggregates, which occupy nearly 70-80% volume of concrete, need to be strong, clean, and
durable. RMC producer needs large volumes of aggregates on a daily basis. Quite often, he has
to depend upon more than one source of aggregates. Before selecting these sources, it is
essential to conduct all routine tests on aggregates as specified in IS 38311 for ensuring quality.
In addition, certain important properties of aggregates need to be monitored on a continuous
basis. IS 49261 suggests testing frequency for different tests on aggregates in Annex B.
8.5.2
The basic properties of aggregate related to its mineralogical composition such as crushing
value, impact value, abrasion value, soundness, potential alkali-aggregate reactivity, etc will not
change much if the aggregate source is the same. Before selecting the source, all these properties
are verified. RMC producers should maintain a record of such properties of aggregates obtained
from different sources by getting the tests conducted in third-party lab at frequencies suggested
in IS 49261. Table 9 suggests a format for such documentation.
8.5.3
Quite often, variations are likely in certain other properties such as particle size distribution,
moisture content, silt content, water absorption, etc, which are related to techniques used in
aggregate processing and external factors. Drawing on the experience and practice followed by
some of the leading RMC producers, Table 10 suggests certain frequency of testing for these
properties of aggregates. It can be seen from this table that some of the suggested frequencies
are stricter when compared with those stipulated in IS 49261. All these properties of aggregates
have direct bearing on some crucial properties of concrete, justifying strict frequency of testing.
- 26 -
Table 9: Physical properties of aggregates
Frequency of
testing as per IS
49261(Low test
rate)
Permissible limits, if any, as
specified in IS 38311
Impact value
As specified
Los Angle’s
abrasion value
Yearly/ Source
change
- Not more than 30 for
wearing surfaces
- Not more than 45 for nonwearing surfaces
- Not more than 30 for
wearing surfaces
- Not more than 50 for nonwearing surfaces
Soundness
Yearly/ Source
change
Six monthly
Property
Chloride content
Potential AAR
Sample 1*
Sample2*
Date
Date
Test
report
Test report
5 Yearly/
Source change
* Based on tests conducted in-house or in a third-party lab.
Table10: Additional physical properties of aggregates
Property
Gradation
Test
frequency
suggested by
IS 49261
Monthly
Moisture content
Silt content for
fine aggregates
Test frequency
suggested by
Guideline
Sample 1*
Date
Test
result
Sample 2*
Date
Test result
Weekly or source
change
Daily twice (three
times in monsoon)
Monthly
Water absorption
3 monthly
Particle density,
3 monthly
Each lot
Once in month; or
source change
3 monthly
Bulk density
6 monthly
6 monthly
Flakiness
6 monthly
6 monthly
Chloride content
6 monthly
6 monthly
* Based on tests conducted at plant lab.
8.5.4 Control on aggregate gradation: It is well known that aggregate grading has an impact on
workability, strength and some other properties of concrete. Since RMC producers are constrained
to depend upon more than one source of aggregates there is likelihood of a variation in the particle
size distribution. The variation would especially be more pronounced in the particle size
distribution of river sand. The Guideline therefore recommends weekly check on grading.
- 27 -
Table 11: Particle size distribution of all-in-aggregates and limits specified in IS 38311
IS sieve size
Cumulative % passing for
20 mm
10
River sand
mm
Cumulative %
Crusher
IS 38311 limit
passing for allin-aggregate
fines
Proportion of aggregate in the mix, %
36.00
12.00
31.00
21.00
40 mm
100
100
20mm
95
100
4.75 mm
30
50
600 µ
10
35
150 µ
0
6
8.5.4.1 With a view to verify the extent of variation in particle size distribution, it may be appropriate to
carry out the sieve analysis test weekly and record the data of cumulative percentage passing for
all-in-aggregates used for the main concrete mixes (for example, M20, M25, M30, M35, M40
etc.) supplied from the plant. The readings may be compared with those of the all-in-aggregate
grading limits stipulated by IS 38311. Table 11 shows a typical format for recording the results
of sieve analysis. Documentation of such data would be useful in tracking any large variation. If
such a variation is evident, suitable corrections may be introduced in the proportions of different
aggregate fractions and simultaneously the suppliers may be alerted to rectify supply.
8.5.5
Moisture content: Considerable variation is usually observed in the moisture content of river
sand and crushed fines. Such variation in moisture would affect the water-binder ratio and hence
strength, if appropriate corrections are not made from time to time in the water content of the
mix. This would be possible if these properties are monitored regularly in accordance with the
frequency of testing suggested in these guidelines. It is suggested that moisture content in fine
aggregates and crushed fines should be monitored two times in a day, and the frequency may be
increased to three times in monsoon. Once the moisture contents are known, appropriate
correction may then be made in the water-binder ratio. It is essential to keep records of the data
on moisture content, possibly in the form of an Excel table or a run chart
8.5.6
Silt content: The Guideline recommends that silt content in fine aggregates should be assessed for
each lot of supply. River sand is particularly prone to have silt beyond permissible limits. Lots
having excessive silt content should be rejected. Control on silt content is essential as an
excessive proportion of the same may adversely affect the workability and strength of concrete.
It is essential to keep records of the data on silt content. Again, this could be in the form of an
Excel table or a run chart.
- 28 -
9. Sampling and testing of concrete
9.1 Incorrect sampling would adversely affect the results of testing; hence, extreme care should be taken
in sampling. It is imperative that the sample of concrete taken from delivery vehicle is
‘representative’. The point and time of sampling shall be at discharge from the supplier’s delivery
vehicle or from mixer to the site or when delivered into the purchaser’s vehicle. As per Annex C of IS
49261, on reaching the point of placement, the truck should re-mix its contents and allow at least the
first one third of a m3 to be discharged before any samples are allowed to be taken. Four incremental
3
samples from the remainder of the load should be then taken, avoiding the last m of concrete. Then
the composite sample should be thoroughly re-mixed either in a mixing tray or in the sampling
bucket and the required testing should commence only after this. A typical sample report is shown in
Table 12. The report provides the time history, sampling location, truck and ticket Nos, etc. The
properties of concrete in its fresh state such as slump, unit weight as well as number of cubes made
should be recorded. Although filling slump cone and preparing test cubes are fairly simple
procedures, the operator needs to follow the procedures meticulously. It is observed that errors in the
procedures often adversely affect the test results. It is therefore essential to record the name and
signature of the person involved in conducting the tests. The operators involved in carrying out these
tests should be trained supervisor, Incidentally, a record of other parameters such as ambient
temperature, concrete temperature can also be made in the report.
Table 12: Typical sample report of fresh concrete
Name
of
Company:
____________________
_____________________________________
Location: ______________________________
Name of client/project: __________________
Time history
Date: _________________
Truck No.: ______________
Ticket No.____________
Total quantity:________m3
Sampled at:
•
Time batched: ___________
•
End of chute □
•
Time arrival at job site: _______
•
End of pump hose □
•
Time discharged: _________
•
Others □
•
Time sampled: _______
•
Time tested: _______
Ambient temperature: ________0C
No. of cubes made: __________
Concrete temperature: ________0 C
Cubes stored at: _____________
Slump:_________mm
Cube prepared by: Mr.____________
Unit weight: ___________kg/m3
Name of authorized person: Mr.___________
Signature: ____________________
- 29 -
9.2 IS 49261 suggests that sampling may be carried out jointly by the purchaser and the supplier with its
frequency mutually agreed upon. The code further states that unless otherwise agreed between the
parties involved, the minimum testing frequency to be applied by the producer in absence of
recognized ready-mixed concrete industry method of production control, should be one sample for
every 50 m3 of production or every 50 batches, whichever is the greater frequency. Table 13
recommends the frequency of sampling for different tests such as slump, compressive strength,
density, temperature, etc. Air-entrained concrete is rarely specified in India; however, in case it is
supplied, it would be essential to test air content of concrete. In many contracts, the frequency of
sampling is stipulated. If the stipulated frequencies are different than what has been shown in Table
13, the former should govern. The size of the sample should generally be not less than 0.035 m3
when it is to be used for strength test. Smaller samples can be taken if used for routine slump tests.
Table 13: Frequency of sampling
QC Test on concrete
Frequency
Slump
•
Minimum of one sample for each 50m3 or
every 50 batches
Compressive strength
•
Density
•
Minimum of one sample (3 test cubes) for
each 50m3 or every 50 batches for test at 28
days.
Additional sample for early age (3, 7 days)
strength test, as mutually agreed
As agreed with customer
Temperature/Air content
•
As agreed with customer
•
9.3 Slump and compressive strength of concrete are two critical parameters to judge concrete’s quality.
Carrying out slump test and preparation of compression test specimens are fairly simple procedures;
however trained operators are needed to ensure that correct procedures are followed. As regards
strength test, it is important to follow standard procedures described in IS 119912 and IS 51613
meticulously for making, curing and testing cube specimens. Any deviation from the procedures may
adversely affect the final results, highlighting the need to employ trained operators for conducting the
tests. Test cubes which are made from fresh concrete are very sensitive to method of handling and
storage conditions during the fist few hours. The test specimens shall be stored in moist air of at least
90% humidity and at a temperature of 27 ± 2OC for 24 hours from the time of addition of water to dry
ingredients. The specimens shall then be marked and removed from moulds and submerged in fresh
and clean water, the temperature of which shall be maintained at 27 ± 2OC. It is essential to employ
trained operators for ensuring that adequate precautions are taken during sampling and testing of
specimens.
- 30 -
10.
Process Control
10.1
In addition to ensuring appropriate quality of the input materials in accordance with the guidelines
described above, it is essential to exercise strict control on the production process. This can be done
in two ways; firstly by ascertaining that the plant and equipment used are in good operational
conditions and secondly by ensuring that sufficient efforts are taken in carrying out design of each
of the concrete mixes to be supplied, following well established methods/norms.
10.2
Upkeep of production facility
10.2.1 RMCMA certification through a third-party audit certainly provides guarantee to the user that the
certified production facility possesses capabilities to produce quality concrete. This certificate is
however based on the commitment provided by the producer that he would adequately maintain the
production facility in accordance with the provisions of RMCMA Check List (QC Manual Part-I).
The producer can demonstrate this by carrying out routine maintenance of storage, handling,
batching, mixing and transporting equipment as well as through regular calibration of weighing
equipment at desired frequency and keeping a proper record of the same. Based on the practices
followed by some of the leading RMC producers, Table 14 gives the suggested frequencies of
maintenance/calibration checks for different components of plant and equipment. It may be
mentioned that the frequencies suggested in this Table are either similar or stricter than those
prescribed in IS 49261.
Table 14: Production control: Suggested frequencies of inspection, maintainance/calibration
Items
Cementitious
materials
Aggregate stockpile
Conveyor belts and
rollers
Central mixer
Trucks
Scale calibration for
all weighing and
measuring
equipment
Water meters
Admixture
dispensers
Gear boxes and oil
baths
Check for
Visual Inspection for
weather-tightness and
leaks
Visual Inspection for
segregation and
contamination
Visual Inspection for
wear and alignment
Visual Inspection of
blades and built up
Visual Inspection of
blades and built up
1.Mechanical/knife
edge systems
Frequency
prescribed
by IS 49261
Frequency
prescribed
by
RMCMA
Weekly
Weekly
-
Daily
Weekly
Weekly
Weekly
Daily
Weekly
Weekly
2 monthly
Monthly
2.Electrical/ load cell
systems
Calibration
Calibration
3 monthly
Monthly
Monthly
Monthly
Monthly
Monthly
Oil change
Quarterly
Quarterly
- 31 -
Plant inspection
Date
Operator
name
and sign
Date
Operator
name and
sign
Observation
of operator, if
any
10.2.1
It is essential that proper records of routine maintenance and calibration are kept by RMC
producer. The records need to be updated on a regular basis. With a view to ensure
accountability, it would be a good practice to include the name and dated signature of person
carrying out inspection and calibration (see Table 14).
10.3
Concrete mix design
10.3.1
In India, a majority of concrete supplied by RMC producers would fall in the category of
‘designed mixes’. Most of the clients specify their requirements of workability and strength
along with the requirement of pumping or otherwise. A responsible RMC producer usually
ensures that the code-specified durability requirements (in terms of minimum cement content,
maximum free water-cement ratio, etc.) are met with. Sometimes, durability requirements and
the allowable maximum size of aggregate are specified by certain clients. Based on these
requirements, the RMC producer carries out mix design in his (or third-party) laboratory,
involving casting and testing trial concrete mixes and optimizing the mix proportions. It is quite
likely that the RMC producer has supplied mixes with similar design earlier, in which case the
producer can furnish actual field data. The details of the finalized mixes are furnished to the
client, who is required to approve the same before supply can commence.
10.3.2
It is suggested that the details of the designed mixes should be maintained in a standard format
as given in Table 15. These details should be furnished to the client on demand. The format is
adopted from Annex D of IS 49261, which has been slightly modified to suit the requirement of
these Guidelines. Besides the contents of cement and mineral additives, and free water-cement
ratio, the Table also contains information on slump at pour site as well as certain additional
desirable information. Separate data sheet may be kept for separate clients and for separate sites
of the same client or different clients.
10.3.3
While the RMC producer is free to adopt any rational method of designing concrete mixes, it
would be a good practice to adhere to the various code-specified requirements, especially those
related to durability of concrete (minimum cementitious content, maximum free water-binder
ratio, etc.).
- 32 -
Table 15: Concrete mix design information
Name of RMC Producer: _____________________________________________________
Name of Client/Contractor:___________________________________________________
Site: ____________________________________________________________________
Mix code
Characteristic strength, N/mm2
Target strength, N/mm2
Minimum cement content, kg/m3 (if specified)
Mineral additives, kg/m3
•
Pulverized fuel ash
•
Slag
•
Silica fume
•
Others (mention type)
Cement type and grade
Nominal maximum aggregate size, mm
Maximum free water-binder ratio
Aggregate/cement ratio
Target workability at plant, (Slump, mm)
Target workability at site, (Slump, mm)
Maximum temperature of concrete at the time of
placing
Class of sulphate resistance
( if applicable)
Exposure condition ( if applicable)
Class of finish ( if applicable)
Mix application
Method of placing
Any other requirements (if applicable)
Laboratory compressive strength, MPa
7-day
28-day
Source: Adapted from IS 49261
- 33 -
11.0 Control Charts
11.1 There is an inherent variability in the properties of various concrete ingredients, in the production
process and the testing procedures. Although RMC producers take maximum possible care to
minimize variability, the same cannot be avoided. It is however important to quantify the
variability and also to identify as to whether it can be attributed to the materials, the production
process or the test methods. The variability could be due to “chance” causes or “assignable” causes.
While chance causes can be attributed to the normal variability of the process, assignable causes
can be eliminated or minimized, thereby reducing the overall variability.
11.2 Control charts can be useful in detecting and monitoring the variability. Such charts can also be
useful in distinguishing chance causes from assignable causes and therefore, they can be used to
decrease variability by eliminating the latter. The charts can also form a permanent record of
quality. Additionally the charts can also be used as a basis for changing specification limits, if
found essential.
11.3 The guidelines strongly recommend use of control charts to monitor QA and QC of concrete.
- 34 -
12.0 Properties of Fresh Concrete
12.1
Workability of concrete
12.1.1 Workability is a broad term which encompasses a range of properties of fresh concrete such as
consistency (fluidity), mobility (ability of concrete to move around the reinforcement and in
restricted areas), compactibility, finishibility and pumpability (for pumped concrete). Evaluating
workability is therefore not easy in view the composite nature of the property. The degree of
workability varies depending upon the type of construction and method of placing, compacting
and finishing. The IS 4562 provides guidance on the range of workability requirements for
different placing conditions and applications (Table 16). Consistency of fresh concrete is
considered to be a close indication of its workability and slump test has been the most widely
used test for ascertaining consistency and hence workability. However, the IS 4562 suggests that
slump test is preferable only for slumps varying from 25 mm to 150mm. For applications
requiring very low slumps (lower than 25mm), the code recommends use of compacting factor
test. Similarly, for applications requiring very high slumps (higher than 150mm) it recommends
use of flow table test. For a majority of concrete supplied by RMC producers, slump test is the
most commonly-used test.
Table 16: Degree of workability for different working conditions
Placing conditions
Degree of workability
Slump, mm
Blinding concrete;
Shallow sections;
Pavement using pavers
Very low
Use compacting factor test as per
IS:119912
Mass concrete; lightly reinforced sections
in slabs, beams, walls, columns; floors;
hand placed pavements; canal linings; strip
footings.
Low
25-75
Heavily reinforced sections in slabs,
columns, beams, walls; slip-form work;
pumped concrete
Medium
50-100
75-100
Trench fill;
In-situ piling
High
100-150
Tremie concrete
Very High
Use determination of flow test as per
IS: 910310
Source: IS 4562
12.1.2 The IS 49261 specifies the following tolerance limits of workability as criteria for acceptance:
•
Slump: ± 25 mm or ± 1/3rd of the specified value whichever is less
•
Compacting factor:
•
± 0.03 for specified value ≥ 0.9;
± 0.04 for specified value ≤ 0.9 ≥ 0.8
± 0.05 for specified value ≤ 0.8
Flow test: Acceptance criteria to be established between the supplier and purchaser.
12.1.3 The test for workability needs to be performed upon discharge from producer’s delivery vehicle
on site or upon discharge into the purchaser’s vehicle. On some occasions, lack of preparedness
on the part of purchaser at construction site may result in delay of placement. RMC producer will
- 35 -
be respon
nsible for maaintaining the slump withhin the perm
missible rangge for a periood of 30 minnutes,
starting frrom arrival of
o transit miixers at job site.
s
Howeveer, after 30 minutes,
m
thee IS 49261 cllearly
states thatt the responssibility for deelay passes on
o the purchhaser.
12.1.44 Slump tesst is somewhhat a crude measure off workabilityy; yet it is quick
q
and heence remainns the
much speecified and accepted method.
m
Slum
mp of conccrete is quitte sensitive to a variety of
environmental and otther factors such
s
as conccrete temperrature, ambiient temperaature, surfacee rate
of evaporration, channges in gradding, batch mass diffeerences, adm
mixture dosaage, presencce of
mineral admixtures or
o otherwise,, variation inn air contennt, variation in testing, etc.
e It wouldd be a
good pracctice to recoord the valuees of slump in Microsofft Excel form
mat and draaw a run chaart. A
typical ex
xample is shhown in Figg 1. Such graphs
g
wouldd be useful in ascertainning the levvel of
control ex
xercised by RMC
R
produccer in controolling the varriation in woorkability.
Fig 1 Typical variiation in the slump of a pumpable
p
mix (specified value:
v
100 mm)
m
12.2
Density of
o concrete
12.2.1 The plasttic density (unit
(
weight)) of convenntional norm
mal-weight concrete variies from 2250 to
2450 kg/m
m3. It variess dependingg upon the variation
v
in the density of differentt ingredientss, the
amount of entrapped and entrainned air (if aiir-entrainingg agents are used), the maximum
m
siize of
aggregatee and water and cemennt contents in the mix. Increasingg the aggreggate volumee and
reducing the
t cement paste
p
would increase the density of concrete.
c
me. The voluume of freshh concrete caan be
12.2.22. Ready miixed concrette is measureed on the baasis of volum
determineed by dividing the total weight of all
a batched materials byy the averagge unit weigght or
12
plastic deensity of cooncrete deteermined in accordancee with IS 1199
1
. Som
metimes, theere is
likelihood
d of a discreepancy in the concrete ordered
o
and that actuallyy supplied. There
T
couldd be a
variety off reasons foor this discrrepancy. Theese include wastage annd spillage of
o concrete, over
excavation, miscalcullations in forrm volume, deflection or
o distortionss of forms, settlement
s
oof wet
mixes, losss of entrainned air, etc. Such
S
differennce can be reconciled iff plastic denssity of concrrete is
monitored
d regularly.
12.2.3 While carrrying out mix
m design, thhe plastic deensity of designed mix is measuredd and talliedd with
the theoreetical densitty. Howeverr, since there is a likelihood of a change
c
in thhe plastic deensity
owing to minor adjustments thatt the RMC producer is required to carry out in
i the produuction
process, itt would be a good practice to measuure the plastiic density att regular inteerval so as ennsure
- 36 -
that the qu
uantities suppplied matchh orders. Thee plastic dennsity measurrement can be
b done by ffilling
a containeer of knownn volume wiith fully com
mpacted concrete and takking the maass of concreete in
that volum
me by folloowing proceddures detailed in IS 119912. In casse a weigh bridge facility is
available at the plannt, it would be a good practice too weigh trannsit mixers before and after
delivery.
12.2.44 Many RM
MC produceers prefer too measure thhe densities of cubes (hhardened cooncrete denssities)
before tessting them for
fo compresssive strengthh. This can simply
s
be doone by findinng the volum
me of
cubes by water displaacement metthod and divviding the mass
m
of cubess in air by thhis volume. F
Fig 2
shows a ty
ypical variattion in the cube
c
densitiees taken from
m the recordds of a RMC
C facility. Inn case
certain cu
ube compresssive strengthhs show low values, it would
w
be advisable to cheeck the density of
the corressponding cuube sampless; if the dennsities of thhe cubes aree lower thaan the theoretical
density, th
he low valuees could be attributed
a
too operator’s sampling
s
errrors.
Fig 2 Typical variiation in densities of cubees
12.3
Temperatture of conccrete
12.3.1 In most parts of Indiaa, tropical weeather prevaails, necessitating adoption of adequate precautioonary
w hot weeather concreeting practicces. Absencee of adequaate measuress may
measures associated with
lead to raapid loss off workabilitty, acceleratted stiffeninng of concreete, poor coompactibilityy and
finishibiliity, and craccking of conncrete owingg to plastic and/or therm
mal shrinkagge. The lattter, at
times, becomes a pooint of disppute betweenn RMC prooducer and contractor/cclients. To aavoid
adverse effects
e
of hoot weather, both
b
RMC producer annd the contrractor need to take adequate
precaution
nary measurres. While the
t RMC prroducer needs to designn a mix havving low heeat of
hydration, contractor needs to takke a number of well-estaablished preccautions in placing,
p
finishing
and curin
ng of concrette. As far ass RMC prodducer is conncerned, he needs
n
to dessign the conncrete
mix using
g a combinaation of OPC
C and supplementary ceementitious materials orr blended ceement
for reduciing the heatt of hydratioon. In additiion, the agggregate stockkpiles in thee plant shouuld be
covered to
o avoid direect exposuree to sun and water shoulld be sprinkkled on the stockpile
s
to bring
down the temperaturee. Some RM
MC producerrs use chilleed water or ice flakes too bring dow
wn the
temperatu
ure of mixingg water during hot summ
mer months. Many consuultants/cliennts stipulate uupper
limit on th
he temperatuure of concreete at pour. During
D
hot weather
w
condditions, it is always adviisable
- 37 -
to keep the temperature of concrete low. This guideline recommends 350C as the upper limit of
temperature of concrete at pour.
12.3.2 It would a good practice to monitor and record both the ambient and concrete temperatures during
pour. The recording of temperatures could be in the form of a run chart (see Fig 3). Such chart
would give quick idea about the extent of variation of pour temperature and would be useful in
the evaluation of the possible reasons for plastic shrinkage and/or thermal shrinkage cracking, if
such cracking is witnessed. Such records would also be providing assurance to customers about
the producer’s ability to control concrete temperature.
Fig 3 Variation in temperature of fresh concrete
12.4
Air content of fresh concrete
12.4.1 In most parts of India, freeze-thaw conditions do not prevail; therefore it is not necessary to use
air-entrained concrete. However, in certain places in northern and north-eastern part of India, if it
becomes essential to use air-entrained concrete to counter the effects of freeze-thaw conditions, it
would be essential to measure and monitor the air content in concrete.
- 38 -
13
Propertties of Hard
dened Conccrete
13.1
Strengtth of concreete
13.1.1
Strength
h of concretee is used as a basis for acceptance
a
inn civil enginneering conttracts. It is bboth a
structuraal attribute and
a a measurre of develoopment of hyydration. In a large majoority of conttracts,
compresssive strengthh of the cubes made, curred and testeed at 28 dayss in accordannce with IS 51613
is the siingle most acceptance
a
p
parameter.
T
This
is becauuse testing of
o strength is relatively easy.
Furtherm
more, many properties of
o concrete such
s
as elasttic modulus, flexural strrength, sheaar and
bond strrengths, caan be deduceed from com
mpressive strrength, afterr appropriatee correlationns are
establish
hed.
13.1.22 While th
he strength of
o concrete at
a 28 days haas emerged as
a a basis for contract sppecificationss, it is
too long
g for RMC producer
p
to wait for takking action to
t rectify prroduction prroblems. It iis too
long also for contraactors and sppecifiers to wait
w for taking decisionss for removiing forms orr preg concrete, or
o to continue with furtheer constructiion.
stressing
13.1.3
To overrcome this, use
u is madee of the relaationship bettween early--age and 28-day strengtths to
allow reemedial actioon to be taken quickly. For example, RMC prooducers and contractors often
use 7-daay, 3-day or even 1-day strength as a tool to esttimate the liikely later-agge strengths. It is
howeverr important to establishh the relationnship between early-agee and 28-daay strengths for a
particulaar cementitioous and aggrregate combiination in usse, and to moonitor the rellationship.
13.1.44
A typicaal chart depicting the variation
v
in 7-day
7
and 28-day
2
strenggths is show
wn in Fig 4. The
chart sh
hows that thee actual 28--day strengthhs of concreete samples are more thhan the speccified
strength of 25 MPa. Documentaation of com
mpressive streength data inn such a form
mat gives a good
idea abo
out the variattion in strenggth values att a glance.
Fig 4 Typical variattion of 7-day and
a 28-day strrengths of M225 concrete
- 39 -
13.2
Standard deviation
13.2.1
For the effective implementation of QA-QC programme, two main tasks before any RMC
producer are: avoidance of failures and attainment of low variability in the test results. While
every RMC producer would like to keep a reasonable margin of safety to avoid failures, he
would also like to have the margin to be as low as possible, so as to achieve economy in
production. For designed mixes, the target mean strength is kept higher than the specified
strength by a certain design margin as given below:
Target strength = specified strength + k s (design margin)
where,
k = a constant which depends upon the proportion of results permitted to be below
specified strength
s = standard deviation.
In most of the contract specifications in India, the permissible percentage below which no
results are expected to lie is generally taken as 5 %. The k value derived mathematically from
statistical tables for 5% failure rate is 1.64. While designing concrete mixes, when no initial data
is available, code-specified values of standard deviation — which are dependent on the degree
of control at site as well as the grade of concrete — are taken in calculations (Table 8 of IS
4562). When more than 30 strength test results are obtained, the actual standard deviation is
calculated for each mix and compared with the assumed values. Higher standard deviation
indicates lower levels of controls. The stricter the QA-QC at the plant, lower will be standard
deviations.
13.2.2
13.2.3
Thus, monitoring and controlling the variation in standard deviation of compressive strength of
concrete mixes could be a crucial parameter in the QA-QC of concrete. The Guideline therefore
suggests that standard deviation of major concrete mixes supplied by the RMC facility should be
evaluated and monitored on a regular basis. However, the standard deviation should be
calculated for a minimum of 30 results.
13.2.4 The standard deviation of M20, M30 and M40 concrete mixes from a RMC facility for three
consecutive months is shown in Fig 5.
Standard deviation, MPa
M25
M30
M40
6
4
2
0
June
July
Month
Aug
Fig 5 Actual standard deviation of major mixes from a typical RMC facility
- 40 -
13.3
Acceptan
nce criteria for compreessive strenggth
13.3.1 The IS 456
4 2 providees guidance on the acceptance criterria. Accordiing to the coode, the conncrete
shall be deemed to comply withh strength reequirements when both the followinng conditionns are
met:
•
the mean strength determined from any grroup of four non-overlappping conseccutive
tests coomplies withh the approprriate limits of
o column 2 in Table 17;;
Tablee 17: Characcteristic comp
pressive stren
ngth compliaance requirem
ment
Speccified grade
M 15
o above
or
Mean of the grroup of 4 non-ooverlapping conssecutive
test results, N//mm2
≥ fck + 0.825 x established stanndard deviation (rounded
off to nearest 0.5
0 N/mm2)
Or
mm2, whichever is
i greater
≥ fck + 3 N/m
In
ndividual results,
s, N/mm2
≥ ( fck – 3) N/mm2
Sourcee: Table 11 of IS
S 4562 (amendmeent 3 of August 2007)
2
13.3.22
Typical variation inn the 28-dayy strength ass well as thhe mean valuues of a grooup of four nonoverlapp
ping consecuutive test reesults can beetter be monnitored withh the help off an Excel-bbased
chart an
nd the same can serve as
a record. A typical charrt is shown in Fig 6. Frrom this graaph it
would be easy to im
mmediately iddentify any shortcoming
s
g in the test results.
r
For example,in
e
F
Fig 6,
no single test result falls below the limit of ( fck – 3) (22 MPa). Thus, it can be cooncluded thaat the
30 test results fulfills the acceptaance criteriaa set by IS 45562.
Fig 6 Variation off 28-day stren
ngth of concrete along with
w the variaation in the mean
m
Of 4 non-overlapp
n
ping consecu
utive test resu
ults.
13.3.3
It would
d be a goodd practice to feed the 288-day comprressive strenngth data in Excel sheeet and
prepare charts similaar to those inn Fig 6 for thhe importantt concrete mixes
m
supplieed by the plaant.
- 41 -
14.0
Special QC Techniques
In addition to whatever has been recommended above, RMC producers are free to adopt special
quality control techniques in their day-to-day work. In fact, one should welcome and encourage
such efforts on the part of RMC producers. Some such techniques include: internal audit, Cusum
technique, failure analysis.
14.1
Internal quality audits report
14.1.1
Many leading RMC producers have developed rigorous internal quality norms and follow well
defined practices to monitor and control quality of input and output materials. In some of these
companies, there is a systematic procedure of reporting quality parameters within the
organization. Quite often, these reports may contain some cost-sensitive information. It is
suggested that after filtering out commercially-sensitive information, the remaining information
may be incorporated in the quality document and the same may be shared with the customers.
14.2
Cusum technique
14.2.1
The “Cusum” technique which was developed in 1960s, was applied to RMC in the 1970s. It
became a widely-used technique in RMC in the UK and many other countries. The British
Standard, BS 5703, published a guide on the technique in 1980 and the Quality Scheme for
Ready Mixed Concrete (QSRMC), UK, adopted it in 1984.
14.2.2 The essential principle is that differences between results and their target values are calculated
and added cumulatively to form a cumulative sum (cusum). When this cusum is plotted
graphically against the sequence of results, a visual presentation of trends relative to the target
level is produced.
14.2.3 The Cusum system can be used for monitoring trends in mean strength, standard deviation and
the relationship between early-age and 28-day strengths. It assists in detection of changes in
these properties and indicates when action should be taken to increase the probability of meeting
the specification or to reduce the materials cost.
14.2.4
There are following three types of cusum systems:
• Cusum M – Mean strength
Keeps track of the difference between the target mean strength and the estimated mean
strength (on the basis of the 7 day result)
• Cusum R – Range
Keeps track of the range of values of the mean strength and monitors the standard
deviation.
• Cusum C – Correlation
Keeps track of the differences between the estimated mean strength and the achieved
mean strength at 28th day.
14.2.5
Some leading RMC producers have developed their own variant of the cusum system. Certain
other producers use standard software packages based on cusum principles. It is recommended
that some of the crucial data on monitoring cusum, which is not price-sensitive, may be included
in the QC document for building confidence amongst customers.
- 42 -
15.
Key Personnel
15.1.1 The success of any QA-QC system would be dependent upon the abilities of key personnel in the
production facility — in particular, their level of knowledge in concrete technology, managerial
ability, length of experience and training undergone. It would be a good practice to include the
names and other details of key plant personnel in the QC document. Besides educational
qualifications, the extent of experience in RMC sphere may also be included. Further, any recent
in-house or external training undergone by the plant personnel should also be incorporated in the
document. Table 18 suggests a format for such documentation.
Table 18: Names, designation and experience of key plant personnel
Sr.
no.
1
Name of
personnel
ABC
Designation
Educational qualification
Experience
Training
Plant-in-charge
BE(Civil),
Dip. in Business
management
-3 years in RMC field
- 2 years in
construction
2
XYZ
Production-incharge
Dip. in Civil Engg.
- 7 years in RMC
field
3
MNR
QC In-charge
BE (Civil)
2 years in RMC field
3 years in customer
service
1 year site engineer
4
VBS
Supervisor
B Sc
5 years of lab
experience
- Distinction in CGLI
Part II examination in
2007
- In-house training in
management 2006
-Credit in CGLI Part-I
examination
- In-house training in
safety and maintenance
in 2007
- NCB training in
concrete technology in
2005
- In-house training in
QA-QC
- Certificate course
from recognized
institution
- In-house training
- 43 -
Section II
Typical Example
Sample QA-QC Document
(Needs periodic updating)
- 44 -
Introduction
This I of the Guidelines presents QA-QC document of a typical RMC production facility. The
document is based on the discussion in of the Guidelines and is in the form of a tabular and graphical
report. It is recommended that each RMC facility should have its own QA-QC document, prepared
with the help of its own data. The tables and graphs included in this section can serve as a guide to
prepare such document. As pointed out in the Preface, this document lays down the basic framework
which includes minimum necessary benchmarks. Each RMC facility is free to follow its own format
and framework; however, the minimum benchmarks included in this document must be followed.
Freedom is also available to the RMC producer to excel over the minimum benchmarks suggested
here.
One of the most important aspects of the document is that it cannot be a static or one-time document.
It needs to be continuously updated. The best way to do this is to keep the records and test results in
Microsoft Word or Excel format and update the records periodically (preferably daily) as more and
more data become available. Thus, a customer can be presented with the latest data at any moment.
What is also important is the fact that some of the tables and graphs in the report can serve as a handy
tool for the Company management to judge the performance of a particular facility.
As mentioned in of this document, it would be appropriate to include the following information by
each Company in its QC Manual.
•
Information about the history of the Company, its network and management
•
Quality policy of the Company
•
Management responsibility and commitment
•
Any other information that the Company thinks relevant for this document.
- 45 -
S-1 Sources of Ingredients
Table S-1: Sources of different ingredients of concrete
Material
Type/
Class
Source
Name of supplier /
Factory / brand
OPC
Location
ABC
DEF
GHI
XXX
YYY
XXX
ABC
-
XXX
-
Slag
-
-
Silica fume
-
-
ABC
XXX
-
-
Fine aggregate
River sand
Man. sand
Quarry A
-
-
Coarse
aggregate
40-mm down
25-mm down
12.5-mm down
Quarry B
Quarry B
XXX
XXX
Quarry fines
Quarry B
X XX
W.R. Agent
ABC
XXX
H.R.W.R.A.
XYZ
YYY
Retarder
-
-
Others
-
-
43 grade
53 grade
Cement
PPC
PSC
Other
Fly ash
Siliceous
Calcareous
Water
Ice
- 46 -
S-2 Monitoring Quality of Ingredients
S-2.1 Cements
Table S-2.1: Selected properties of cement*
Property
Manufacturer I
Manufacturer II
Manufacturer III
Date of testing
Oct. 15, 2007
Oct. 22, 2007
Oct. 29, 2007
Type of cement
PPC
OPC 53 grade
PSC
Provisions
of IS 1489:
(Part I)5
Test results
Provisions
of IS
122694
Test results
Provisions
of IS 4556
Test
results
300 (min)
416.20
225 (min)
306.00
225 (min)
388
3-day
16
39.17
27
41.00
16
28.19
7-day
22
48.36
37
49.00
22
39.59
28-day
33
68.74
53
59.00
33
59.14
Initial
30 (min)
130
30 (min)
135
30 (min)
118
Final
600 (max)
210
600 (max)
185
600 (max)
178
Soundness, mm
10 (max)
1.00
10 (max)
1.00
10 (max)
0.37
1.65
4 (max)
2.08
22 %
fly ash
-
Nil
Fineness, m2/kg
Compressive strength, MPa
Setting time, minutes.
Loss on ignition, %
% of mineral admixture (fly ash or slag) in
PPC or PSC
15-35 %
fly ash
1.35
35-70 %
slag
* Results based on the test certificate provided by cement manufacturers.
S-2.2 Fly ash
Table S-2.2: Physical requirements of fly ash conforming to IS 38127 and results of selected tests
on samples
Sr.No.
Property
IS 38127 Requirements
Sample 1
Sample 2
Date
Test
report
Date
Oct. 10
12.70#
Oct. 22
Test
report
17.00#
1
Particles retained on 45 µ sieve
34% (max)
2
Blaine's fineness
320 m2/kg (min)
Oct. 10
416*
Oct. 22
425*
3
Lime reactivity
4.5 MPa (min)
Oct. 10
6.80*
Oct. 22
6.40*
4
28-day compressive strength
Not less than 80% of control
Oct. 10
44.40*
Oct. 22
46.20*
5
Soundness
0.8 % (max)
Oct. 10
0.50*
Oct. 22
0.50*
# Results based on test done at plant
* Results based on manufacturer’s certificate
- 47 -
50%
slag
S-2.3 Ground granulated blast furnace slag
Table S-2.3: Properties of GGBS conforming to BS 6699 and IS 120899 and results* of
selected tests on samples
Property
BS 6699 / IS
12089
Requirements
Results of tests*
Date
Test report
275 m2/kg (min)
Feb. 6
385
Mar 23
373
12.0 MPa
32.5 MPa
Feb. 6
36.15
46.45
Mar 23
35.55
43.50
Initial setting time
Not less than
IST of OPC
Feb. 6
211 min
Mar 23
223 min
Soundness (Le-Chatellier expansion)
10mm (max)
Feb. 6
0.00
Mar 23
0.00
Glass content
67% (min.)
Feb. 6
93
Mar 23
98
Blaine's fineness
Compressive strength,
7-day
28-day
Date
Test report
* Results based on the test certificate provided by cement manufacturer.
S-2.4 Condensed silica fume
Table S-2.4: Properties of condensed silica fume conforming to IS 153888 and results* of
selected tests on samples
Property
IS 153888
Requirements
Results of tests*
Date
Test report
Date
Test report
Specific surface, m2/kg
15,000 (min)
Aug 31
18,000
Sept. 15
17,500
SiO2 content, %
85% (min.)
Aug 31
90
Sept. 15
87
Pozzolanic activity index
85% at 28 days
Aug 31
-
Sept. 15
-
Moisture content
3% max.
Aug 31
negligible
Sept. 15
negligible
LOI
6% max.
Aug 31
4.6
Sept. 15
4.2
* Results based on the test certificate provided by manufacturer.
- 48 -
S-2.5 Chemical admixtures
Table S-2.5.1: Results of initial laboratory trials on Chemical admixture
Property
Control
concrete
Concrete with admixture
Manufacturer Manufacturer Manufacturer
I
II
III
Name of Manufacturer
-
XXX
YYY
ZZZ
Name of brand
-
AAA
BBB
CCC
Generic type
-
HRWRA
HRWRA
HRWRA
Water content, % of
control sample
-
12
16
14
Adverse effects, if any,
observed during trials
Slump
0 min
40
140
160
140
30 min
0
120
145
120
60 min
0
120
110
120
90 min
0
-
-
-
Compressive strength, % of
control sample
1-day
-
-
-
-
3-day
18.28
17.77
18.88
17.37
7-day
22.93
21.87
23.14
20.88
28-day
35.11
36.02
37.12
34.12
Not tested
Not tested
Not tested
Not tested
-
No
incompatibility
problems
noticed
No
incompatibility
problems
noticed
No
incompatibility
problems
noticed
Air content, % max over
control
Sample from
Manufacturer III produced
strengths lower than the
control strengths at 3, 7 and
28 days. This sample was
therefore rejected. The 3
and 7 day strength for
sample of Manufacturer I
were lower than the control.
This sample was also
rejected. Sample from
Manufacturer II was found
suitable.
Observations on cementadmixture compatibility
Dosage of 1 % by weight of
cementitious material was
selected based on
manufacturer’s
recommendation; no
adverse effects noticed.
Control mix details:
PPC: 380 kg; Aggregates: 651 kg (20 mm), 351 kg (10 mm), 421 kg (CRF), sand: 421 kg, water: 254 lit.
- 49 -
Table S-2.5.2: Uniformity requirement of admixtures conforming to IS 910310 and results of selected tests on
samples
Uniformity test
Requirements as per IS 91038
Suggested
frequency
Relative density
Within 0.02 of the value stated by the
manufacturer
Dry mat. content
of admixture
0.95 T ≤ DMC ≤ 1.05 T
where, T = Manufacturer’s stated
value in % by mass
DMC= Test result in % by mass
Test values at the
time of
acceptance
Test values during use
Sample 1
Sample 2
Date
Test
report
Date
Test
report
For every drum
before use
1.25
Aug
07
1.24#
Aug
08
1.266#
Each new batch
before
acceptance
48.0
-
48.29*
(0.6%)
-
48.84
(1.75%)
-
-
-
-
-
-
-
0.004*
-
0.091*
-
7.05*
-
7.89*
Ash content
0.95 T ≤ AC ≤ 1.05 T
Chloride ion
content
Within 10 % of the value or within
0.2 %, whichever is greater as stated
by the manufacturer
Each new batch
before
acceptance
pH
6 (min.)
Each new batch
where, AC= Test result in % by mass
7.26
* Results based on manufacturer’s certificate..
# Results based test conducted at plant.
S-2.6 Water
Table S-2.6: Permissible limits for solids in water and results of tests on samples of fresh and recycled water
Solids
Permissible
limits as
specified in IS
4562, max.,
mg/l
Sulphates as SO3 #
Chlorides as Cl
Fresh water
Sample 1
Date
Sample 1
Sample 2
Test
report
Test
report
Date
Date
Recycled water
Sample 2
Test
report
Date
Test
report
400
Mar 9
70
June 8
950
Mar 9
200
June 8
200
Mar 9
124
June 8
2800
Mar 9
450
June 8
490
#
•
Plain
concrete
2000
•
R.C.
500
pH
2800
124
450
Not less than 6
Mar 9
6.8
June 8
7.4
Mar 9
Suspended matter*
2000
Mar 9
1500
June 8
223
Mar 9
Organic*
200
Mar 9
145
June 8
66
Mar 9
N.A.
June 8
N.A.
Inorganic*
3000
Mar 9
2500
June 8
5800
Mar 9
N.A.
June 8
N.A.
2
6.9
490
June 8
8.1
June 8
Note: The underlined values being higher than those specified in IS 456 , the consignment from which Sample 2 was taken was rejected.
* Results based on manufacturer’s certificate..
# Results based test conducted at plant.
- 50 -
S-2.7
7 Aggregate
es
Tab
ble S-2.7.1: Physical
P
prop
perties of agggregates
Prooperty
Frequency of
o
testing as peer IS
49261(Low test
t
rate)
Im
mpact value
As specifiied
Permisssible limits, if an
ny, as
specifiedd in IS 38311
Samplle 1
T report*
Test
D
Date
- Not moore than 30 for wearing
w
surfacess
- Not moore than 45 for non-wearing
n
surfacess
- Not moore than 30 for wearing
w
surfacess
- Not moore than 50 for non-wearing
n
surfacess
-
20.7%
-
25.6%
Los Angeles
abrrasion value
Yearly/ Souurce
change
Souundness
Yearly/ Souurce
change
-
8.5%
(MgSO4)
Six monthhly
-
Negligible
5 Yearlyy/
Source chaange
-
Innocuous
Chhloride content
Pottential AAR
* Based on tests condu
ucted in third-parrty lab.
S-2.7
7.1 Aggrega
ate gradatio
on
Tab
ble S-2.7.1.1: Cumulative
C
% passing for aggregates
a
useed for M 25 mix
m with IS 383311 limits
(Agggregate proportion: 20mm: 10m
mm: river sand: crushed
c
sand = 36:12:31:21)
3
I sieve,
IS
mm
IS 383111 limits
C
Cumulative
perccent passing
20 mm
10 mm
River
sand
Crushed
sand
All-inaggregates
Lower limit
Upper limit
40
36.00
12.00
31.00
21.00
100.00
100.00
100.00
20
30.10
12.00
31.00
21.00
94.00
95.00
100.00
4.775
0.11
1.27
23.16
19.80
44.00
30.00
50.00
0.660
0.00
0.00
4.50
6.20
11.00
10.00
35.00
0.115
0.00
0.00
0.47
2.90
3.00
0.00
6.00
Fig S-2.7.1.1
S
All-in
n-aggregate grrading curve for
f aggregatess used for M 25
2
11
mix with
w upper an
nd lower limitss as per IS 3833 (graphical representatioon of Table S-22.7.1.1)
- 51 -
Table S-2.7.1.2: Cu
umulative % passing
p
for agggregates used for M 40 mix with IS 38311 limits
(Aggreegate proportion : 20mm: 10mm
m: river sand: crrushed sand = 411:13:32:14)
IS sieeve,
mm
m
IS 38311 lim
mits
Cum
mulative percent passing
20 mm
10 mm
River sand
Crushed
C
s
sand
All-inA
agggregates
Loower limit
Uppper limit
40
41.00
13.00
32.00
1
14.00
100.00
1000.00
1000.00
20
34.28
13.00
32.00
1
14.00
93.00
955.00
1000.00
4.75
0.12
1.38
23.90
1
13.20
39.00
300.00
50.00
0.60
0.00
0.00
4.64
4
4.97
10.00
100.00
35.00
0.15
0.00
0.00
0.48
1
1.93
2.00
0.000
6.00
Fig S--2.7.1.2 All-in--aggregate graading curve foor aggregates used
u
for M 400
1
11
mix with
w upper and
d lower limits as per IS 383 (graphical representation
r
n of Table S-2..7.1.2)
A
ph
hysical propeerties of aggrregates
Tablee S-2.7.1.3: Additional
Properrty
Gradattion
Test
frequency
suggested
by IS 49261
Test frequency suggested
by Guideline
Monthly
Weekly or sourrce change
See Tables S-2.7
7.1.1 and S-2.7.1.2
Daily twice (thrree times in
monsoon)
See graph shown in Fig S-2.7.2
See graph shown in Fig S-2.7.3
Moistuure content
D
Date
Silt conntent for fine
aggreggates
Monthly
Each lot
Water absorption, %
3 monthly
3 monthly; or soource
change
Bulk density,
d
kg/m3
(Uncom
mpacted)
Bulk density,
d
kg/m3
(Comppacted)
Flakineess index, %
3 monthly
6 monthly
6 monthly
S
Sample
1*
3 monthly; or soource
change
3 monthly; or soource
change
3 monthly; or soource
change
- 52 -
Test ressults
M1
M2
Sandd
CRF
O
Oct.15
2.4
1.6
3.15
3.9
O
Oct.15
1492
1468
18588
1580
O
Oct.15
1615
1590
19100
1690
O
Oct.15
8.59
7.76
-
-
S-2.7
7.2 Moisture
e content
Fig S-2.7.2 Variattion in moistu
ure content of
o fine and cooarse aggreggates and cru
ushed sand
2.7.3 Silt conten
nt
Fig 2..7.3 Variation in silt conttent of river sand
s
as percent by volum
me
- 53 -
S-3 Sampling and testing of concrete
Table S-3: Typical sample report of fresh concrete
Name of Company: X Y Z
Location: Mumbai
Date: September 28, 2007
Truck No.: MH 1111
Name of client/project: A B C
Ticket No.: X Y Z 1111
Total quantity: 25 m3
Time history
•
Sampled at:
•
Time batched: 15.30 hour
End of chute □
•
Time arrival at job site: 16.45 hour
•
End of pump hose □ √
•
Time discharged: 17.00 hour
•
Others □
•
Time sampled: 17.05 hour
•
Time tested: 17.10 (slump)
Ambient temperature: 300C
No. of cubes made: 04
Concrete temperature: 320 C
Cubes stored at: _____________
Slump: 120 mm
Cube prepared by: Mr. A B C
Unit weight: 2475 kg/m3
Name of authorized person: Mr XYZ
Signature: Signed by X Y Z
- 54 -
S-4 Process Control
S-4.1 Inspection report of production facilities
Table S-4.1: Production control
Items
Check for
Frequency
prescribed
by IS 49261
Frequency
prescribed
by
RMCMA
Plant inspection
Date
Operator
name
and sign
Date
Operator
name
and sign
Observation
of operator, if
any
Cementitious
materials
Visual Inspection for
weather-tightness and
leaks
Weekly
Weekly
Oct 22
XYZ
Oct 29
XYZ
okay
Aggregate
stockpile
Visual Inspection for
segregation and
contamination
-
Daily
Oct 22
ABC
Oct 22
ABC
Slight
contamination of 20
and 10 mm
sizes due to
over supply;
rectifications
carried out
Conveyor belts
and rollers
Visual Inspection for
wear and alignment
Weekly
Weekly
Oct 22
XYZ
Oct 29
XYZ
okay
Central mixer
Visual Inspection of
blades and built up
Weekly
Daily
Oct 22
XYZ
Oct 23
XYZ
okay
Trucks
Visual Inspection of
blades and built up
Weekly
Weekly
Oct 22
XYZ
Oct 29
XYZ
No
appreciable
built up for all
6 vehicles in
use
Scale calibration
for all weighing
and measuring
equipment
1.Mechanical/knife
edge systems
2 monthly
Monthly
-
-
-
-
-
2.Electrical/ load cell
systems
3 monthly
Monthly
Oct 22
ABC
Nov22
ABC
okay
Water
meters
Calibration
Monthly
Monthly
Oct 22
ABC
Nov22
ABC
okay
Admixture
dispensers
Calibration
Monthly
Monthly
Oct 22
ABC
Nov22
ABC
okay
Gear boxes and
oil baths
Oil change
Quarterly
Quarterly
Oct 22
XYZ
Jan 22
XYZ
okay
- 55 -
S-4.2 Concrete Mix Design
Table S-4.2: Concrete mix design information
Name of RMC Producer: X Y Z
Name of Client/Contractor: A B C
Site: IJKL, Mumbai
Mix code
XXX
YYY
ZZZ
AAA
Characteristic strength, N/mm2
25
30
40
60
Minimum cement content, kg/m3 (if specified)
365
430
450
450
-
-
100
-
50
40
-
Cement type and grade
PPC
PPC
OPC- 53
OPC- 53
Nominal maximum aggregate size, mm
20
20
20
20
Maximum free water-binder ratio
0.46
0.37
0.40
0.30
Target workability at plant, (Slump, mm)
120
140
140
140
Target workability at site, (Slump, mm)
100
100
100
120
Maximum temperature of concrete at the time of placing
32
32
32
30
Class of sulphate resistance ( if applicable)
-
-
-
-
Exposure condition ( if applicable)
severe
severe
severe
severe
Class of finish ( if applicable)
-
-
-
-
Method of placing
Pumping
Pumping
Pumping
Pumping
Any other requirements
Nil
Nil
Nil
Nil
-
-
34.30
-
20.30
23.75
37.70
52.50
30.0
35.00
50.70
66.70
-
-
-
-
Mineral additives, kg/m3
•
•
•
•
Pulverized fuel ash
Slag
Silica fume
Others (mention type)
Mix application
Laboratory compressive strength of concrete, MPa
5-day
7-day
28-day
3
Quantity, m
Source: Format of Table adapted from IS 49261
- 56 -
S-5 Properties
P
of
o Fresh Co
oncrete
S-5.1
1 Workabilitty of concre
ete
Fig S--5.1.1 Typical variation in th
he slump of M30
M and M40 mixes
m
(specified value: 100 mm)
Fig S--5.1.2 Typical variation in slump of M25 mix (specified
d slump: 50 mm)
m
S-5.2
2 Density off concrete
Fig S--5.2 Typical va
ariation in cub
be density of M25,
M
M30 and
d M40 concrette mixes
- 57 -
S-6 Properties
P
of
o Hardeneed Concretee
S-6.1
1 Strength of
o concrete
Fig S-6.1.1 Typicall variation of 7-day
7
and 28-day strengths of M30 concrrete using OPC
C+ fly ash
7
and 28-d
day strengths of M40 concreete using OPC
C+ fly ash
Fig S--6.1.2 Typical variation of 7-day
S-6.2
2 Standard deviation
d
Tablee S-6.2.Month-wise stand
dard deviatioon of 28-day strengths
s
of M25,
M
M30 an
nd M40 mixees
Month
h
M25
M30
No. of
Standard
results
deviation,
MPA
M40
No. of resu
ults
Standdard
o results
No. of
S
Standard
Plant
deviattion,
d
deviation,
standard
MP
PA
MPA
deviation
June 077
34
4.66
32
4.88
46
3.95
4.47
July 077
34
4.47
39
4.16
32
4.00
4.15
Aug. 07
31
4.65
35
3.995
33
3.83
4.25
- 58 -
Standard deviation, MPa
June
July
August
5
4
3
2
M25
M30
M40
Plant
Grade of concrete
Fig S-6.2. Month-wise variation of standard deviation of 28-day strengths of
M25, M30 and M40 mixes (graphical representation of Table S-6.2)
S-6.3 Acceptance criteria for compressive strength
28-day strength
Av. of con. 4
fck-3
fck+3
Comp. strength, MPa
50
40
30
20
10
0
1
3
5
7
9
11 13 15 17 19 21 23 25 27 29
No of samples
Fig S-6.3.1 Variation of 28-day strength of concrete along with the variation in the mean of 4
non-overlapping consecutive test results for M30 concrete
- 59 -
28-day strength
Av. of con. 4
fck-3
fck+3
Comp. strength, MPa
60
50
40
30
20
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
No of samples
Fig S-6.3.2 Variation of 28-day strength of concrete along with the variation in the mean of 4
non-overlapping consecutive test results for M40 concrete
- 60 -
7. Key Personnel
Table S-7.1: Names, designation and experience of key plant personnel
Sr.
no.
1
Name of
personnel
ABC
Designation
Educational qualification
Experience
Training
Plant-in-charge
BE(Civil),
Dip. in Business
management
-3 years in RMC field
- 2 years in
construction
2
XYZ
Production-incharge
Dip. in Civil Engg.
- 7 years in RMC
field
3
MNR
QC In-charge
BE (Civil)
2 years in RMC field
3 years in customer
service
1 year site engineer
4
VBS
Supervisor
B Sc
5 years of lab
experience
- Distinction in CGLI
Part II examination in
2007
- In-house training in
management 2006
-Credit in CGLI Part-I
examination
- In-house training in
safety and maintenance
in 2007
- NCB training in
concrete technology in
2005
- In-house training in
QA-QC
- Certificate course
from recognized
institution
- In-house training
- 61 -
Bureau of Indian Standards referred in Guidelines
1.
IS 4926: 2003, Ready-Mixed Concrete- Code of Practice (Second Revision), p. 18.
2.
IS 456 : 2000, Plain and Reinforced Concrete- Code of Practice ( Third Revision) ( Reaffirmed 2005), p. 100.
3.
IS 8112:1989, Specification for 43 grade Portland cement (First Revision), (Reaffirmed 2005), p. 7.
4.
IS 12269 : 1987, Specification for 53 grade ordinary Portland cement, ( Reaffirmed 2004), p.11.
5.
IS 1489 : Part : 1991, Specification for Portland pozzolana cement, Part 1, Fly-ash based (Third Revision)
(reaffirmed 2005), p. 7.
6.
IS 455 : 1989, Specification for Portland slag cement (Fourth Revision) ( Reaffirmed 2005 ), p. 7.
7.
IS 3812 : Part 2 : 2003, Pulverised Fuel Ash-Specification, Part 2 : For Use as a Admixture in Cement Mortar and
Concrete, ( Second Revision ) p. 7.
8.
IS 15388 : 2003, Silica Fume- Specification, p.7.
9.
IS 12089 : 1987, Specification for Granulated Slag for Manufacture of Portland Slag Cement, , (reaffirmed 2004),
p.9.
10. IS 9103: 1999, Concrete Admixtures: Specifications (First revision), (Reaffirmed 2004), p.14.
11. IS 383 : 1970, Specification for Coarse and Fine Aggregates from Natural Sources for Concrete, (Second
Revision), ( Reaffirmed 2007), p. 19.
12. IS 1199 : 1959, Methods of Sampling and Analysis of Concrete, (Reaffirmed 2004), p.44.
13. IS 516: 1959, Method of Test for Strength of Concrete, (Reaffirmed 2004), p. 24.
- 62 -