Parameters for Good Site Concrete Production Management Practice in Nigeria

PARAMETERS FOR GOOD SITE CONCRETE PRODUCTION MANAGEMENT PRACTICE IN NIGERIA

Nwabueze Michael ANOSIKE

MATRICULATION NO: CUGP070178

BEING A PHD THESIS SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES (SPS) IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF THE DEGREE OF DOCTOR OF PHILOSOPHY (PHD) IN BUILDING TECHNOLOGY (CONSTRUCTION MANAGEMENT) OF THE DEPARTMENT OF BUILDING TECHNOLOGY, SCHOOL OF ENVIRONMENTAL SCIENCES, COLLEGE OF SCIENCE & TECHNOLOGY, COVENANT UNIVERSITY, OTA, NIGERIA.

July, 2011

i DEDICATION

I dedicate this work to my late father Mazi S. N. Anosike and my mother madam Beatrice N. Anosike (nee Udegbu).

ii CERTIFICATION OF SUPERVISORS This thesis titled “PARAMETERS FOR GOOD SITE CONCRETE PRODUCTION MANAGEMENT PRACTICE IN NIGERIA” by ANOSIKE, Michael Nwabueze meets the regulations governing the award of the degree of Doctor of Philosophy (Ph.D) in Construction Management of the Department of Building Technology, Covenant University, Ota, Nigeria, and it is approved for its literary presentation and contribution to knowledge.

------Prof Tim O. Mosaku Date Major Supervisor

------Prof. G.L.Oyekan Date University of Lagos Co-Supervisor

iii ACKNOWLEDGEMENT Prof. Timothy Olusoji Mosaku: My father, mentor and friend. Prof has been there all the way for me. The thesis title was provided by him not because the author lacked titles but because of his burning desire to contribute to the elimination of the menace of building collapse ravaging the construction Industry and the entire Nation in recent time. I met him all the way back at Ahmadu Bello University, Zaria as one of his students. Thank you Prof. Tim!! Prof. G.L. Oyekan: A father and friend. He also provided strategies and the types and number of laboratory tests required in this research. He actually calls me his son. And so relates with me as such. He not only impacted me academically within the period of this work, his fatherly prayers for me as a Pastor also contributed immensely to the success of this work. This work has also brought us together for life. Thank you Prof. My Wife - Favour Ihuoma Anosike (Nwogu), she encouraged me a lot because she believed in this academic pursuit, and to the children Enyioma and the twins – Chimzaram & Chimnomso. For their age they could not believe that their daddy was a student. We all did this work together because I remember how my wife always came with the children to encourage me every Saturdays and Sundays in the course of the laboratory experiments. Prof Timothy Chukwuemeke Mogbo: My father, mentor and friend. I met him way back as I entered his blossoming Quantity Surveying consultancy office in Kaduna to undertake my Industrial Training programme as a diploma student. He not only encouraged my academic pursuit but went a step further to secure admission for me to read B.Sc Building at the famous Ahmadu Bello University, Zaria. He did not stop there he still fired me up to acquire higher degrees in my profession. I am sure I have not disappointed him in that direction. Thank you Prof. for this kind of love on someone you never knew earlier!! Pastor Godfrey George (R.I.P): My spiritual father. He never doubted my abilities and so never stopped loving and encouraging me in this pursuit. His wife shares the same spirit too. He stood as my guarantor for this doctoral programme. But unfortunately, just like my father he never lived to share in the joy of this laurel with me to the end. Pastor Onwuatu Roy & Wife: They stood by me and my vision right at the beginning in counsel, encouragement and prayers. Surely their prayers and support to this endeavor had paid off.

iv Dr Oginni and Dr Ede Anthony: Both are faculty staff, Dept. of Civil Engineering, Covenant University, Ota. They read my work at some point and provided ideas and strategies especially during the laboratory investigations. Dr Ede actually read the entire thesis. Ghana 2009 WABER Organizers: Prof. Wills Hughes, Dr. Sam Laryea, Dr Lieringer all were faculty staff of the Department of Construction Management and Engineering, University of Reading, England and resource persons when I presented mine research proposal to the academic audience at the British Council, Accra Ghana on the platform of the West African Built Environment Researchers (WABER). Prof. Echeme Johnbul was the Head of Department of Industrial Chemistry, Covenant University, Ota. Through him all our specimens were tested in the Industrial Dept. laboratory. Dr. Peter Edwards and Prof Raymond Nkado are members of the famous internet group, Cooperative Network for Building Researchers (CNBR). CNBR moderator, Dr. Edwards actually read through my work at the proposal level and provided me some part of the research methods. I also appreciate the contributions of the following faculty staff members Bldrs’ Amusan. L.M, Ogunde, A.O, Drs’ Owolabi and Lawal, Mrs Olaniyan and Mr J. Moses laboratory personnel Rev. Badmus (Civil), Mr Babalola B, Mr. Ogunbayo and Mr. K. Ajao (Bld Tech), Engr Akinyemi (Civil), Mr Falomo (Ind. Chem.). I appreciate the visionary leadership of Dr. David Oyedepo, the proprietor of the University and the Management team ably captained by the Vice-Chancelor, Prof. Aize Obayan who always acted promptly to any memo in respect to this study. My appreciation goes to all members of the Winners’ Satelite Fellowship (WSF) cells at Suite 25- Mr. Ben-Caleb & family, Dr & Mrs Lawal, Dr. Ovia and suite 24 (where I function by His Grace as the Cell Minister) members, Mr & Mrs Comrad, Dr Azuh & Family, etc. The support of my other family members – my mother, Nwigbe Beatrice (Nee Udebgu) and my siblings, Adanma, Okenwa, Ihunna & Mercy is appreciated. In summary, I thank the Lord God Almighty. Without Him this work couldn’t have been possible. To Him alone be all the Glory!!

v AUTHORIZATION TO COPY COVENANT UNIVERSITY, OTA, NIGERIA CENTRE FO LEARNING RESOURCES

POSTGRADUATE THESIS

AUTHORITY TO COPY

AUTHOR: ANOSIKE, Michael Nwabueze

TITLE: PARAMETERS FOR GOOD SITE CONCRETE PRODUCTION MANAGEMENT PRACTICE IN NIGERIA

DEGREE: Doctor of Philosophy (PhD), Construction Management

YEAR: 2011

I, ANOSIKE, Michael Nwabueze hereby authorize Centre for Learning Resources (CLR) to copy my thesis in part or whole in response to requests from individuals and or organizations for the purpose of private study or research.

…………………………….. ……………………….. Signature Date

vi TABLE OF CONTENTS

Content Page Title Page…………………………………………………………………………… i Dedication …………………………………………………………………………..ii Certification of Supervisors ………………………………………………………...iii Acknowledgement …………………………………………………………………iv Authorization to Copy ……………………………………………………………..vi Table of Contents ………………………………………………………………….vii List of Tables ………………………………………………………………………xiii List of Figures ………………………………………………………………………xv Abstract …………………………………………………………………………….xvi

CHAPTER ONE 1.0 General Introduction…………………………………………………………… 1 1.1 Background of the Study ………………………………………………………. 1 1.2 Statement of the Problem ………………………………………………………. 4 1.3 Justification of the Study ………………………………………………………. 5 1.4 Research Questions ……………………………………………………………. .6 1.5 Research Hypothesis and Testing ………………………………………………. 6 1.6 Aim of the Study…………………………………………………………………6 1.7 Objectives of the Study .…………………………………………………………6 1.8 Sample Population …. ………………………………………………...…………7 1.9 Scope of the Study ………………………………………………………………8 1.10 Limitations of the Study ……………………………………………………….9

CHAPTER TWO 2.0 Literature Review ………………………………………………………………..11 2.1 Review of Related Studies ………………………………………………………11 2.2 The Production and Management of Concrete ………………………………….15

vii 2.3 Concrete Materials (COM) ………………………………………………………16 2.3.1 Portland Cement (PC) ………………………………………………………..22 2.3.2 Aggregates …………………………………………………………………...33 2.3.3 Water for the Works ………………………………………………………..47 2.3.4 Admixture and Additives …………………………………………………..52 2. 4 Fresh Concrete ………………………………………………………………. 56 2.5 Advantages of Concrete ……………………………………………………. 58 2.6 Types of Concrete ……………………………………………………………59 2.6.1 Conventional Concrete ……………………………………………………….59 2.6.2 In-situ Concrete ………………………………………………………………59 2.6.3 Unconventional Concrete …………………………………………………..61 2.6.4 Ready-Mixed Concrete …………………………………………………….61 2.6.5 Light Weight Concrete (LWC) …………………………………………….62 2.6.6 Light Weight Aggregate (LWA) Concrete …………………………………65 2.6.7 Aerated LWC ……………………………………………………………….66 2.6.8 Foamed Concrete ……………………………………………………………67 2.6.9 No-Fines Concrete …………………………………………………………..67 2.7 Production of Concrete …………………………………………………….69 2.7.1 Specifying Concrete ………………………………………………………….69 2.7.2 Concrete Mix Ratio …………………………………………………………..73 2.7.3 Batching Concrete ……………………………………………………………73 2.7.4 Mixing Concrete ……………………………………………………………75 2.7.5 Handling (Transporting) In-Situ Concrete …………………………………78 2.7.6 Placing Fresh Concrete ……………………………………………………..85 2.7.7 Placing Concrete in Water ………………………………………………….86 2.8 Working of Concrete ……………………………………………………….86 2.8.1 Workability of Concrete ……………………………………………………...86 2.8.2 Factors Affecting Workability of Concrete ………………………………….87 2.8.3 Tests for Workability of Concrete ……………………………………………87 2.8.4 Compaction of Fresh Concrete ……………………………………………. 88 2.9 Development of Strength (Curing) of Fresh Concrete ……………………..90

viii 2.9.1 Methods of Curing Concrete ……………………………………………….91 2.9.2 Curing Concrete Slab ……………………………………………………….95 2.9.3 Curing Columns, Beams and Walls …………………………………………95 2.9.4 Setting and Hardening of Concrete …………………………………………96 2.9.5 Temperature Regulations in Curing Concrete ……………………………….97 2.10 Joints in Fresh Concrete …… …………………………………………… ..97 2.10.1 Types of Joints in Fresh concrete ……………………………………………98 2.11 Defects in Concrete ……………………………………………………….. 101 2.11.1 Causes of Defects …………………………………………………………...101 2.11.2 Types of Defects in Concrete ……………………………………………….101 2.11.3 Segregation of Concrete …………………………………………………….103 2.11.4 Bleeding of Fresh Concrete ………………………………………...... 105 2.12 Testing of Concrete …………………………………………………………105 2.12.1 Classification of Tests ………………………………………………………105 2.12.2 Preparation of Samples for Testing …………………………………………106 2.12.3 Curing of Concrete Specimen……………………………………………….106

CHAPTER THREE

3.0 ENSURING QUALITY IN CONCRETE PRODUCTION PRACTICE 3.1 Theory Formulations and Application for Site In-situ Concrete. ………….107 3.2 The Concept ………………………………………………………………..107 3.3 Tasks, Functions and Responsibilities ………………………………….….109 3.4 Technical Quality Control Requirements in Concrete Production ……………..110 3.4.1 Professional Regulatory Bodies and Quality Control ………………………110 3.4.2 Acts/Decrees for Construction Professionals ………………………………...111 3.4.3 The Client …………………………………………………………………….111 3.4.4 Architects …………………………………………………………………... 112 3.4.5 Engineers ……………………………………………………………………..112 3.4.6 Professional Builder …………………………………………………………..113 3.4.7 Quantity Surveyor …………………………………………………………… 113

ix 3.4.8 Design and Build-ability ………………………………………………………114 3.4.9 The National Building Code …………………………………………………..114 3.4.10 Materials Manufacturers and Quality Standards ………………………….....115 3.4.11 International Standards Organization (ISO) 9000 Series- Standard Organization of Nigeria (SON) –Nigeria Industrial Standards (NIS) ……. .115

3.4.12 Occupational Health & Safety Act ………………………………………... 117 3.4.13 Consumer Protection Council (CPC) ……………………………………….118 3.4.14 National Housing Policy ……………………………………………………119 3.4.15 ILO – Nigeria Labour Act and Factories Act ……………………………...119 3.4.16 Workmen’s Compensation Act/Nigeria Social Insurance Trust Fund) ……120 3.4.17 Federal Environmental Protection Agency (FEPA) and NESREA ………..121 3.5 Managerial QC Requirements in Concrete Production …………………….121 3.5.1 Quality Management Systems ……………………………………………...121 3.5.2 Manpower Resource and Management ……………………………………..123 3.5.3 Classification of Manpower ………………………………………………...123 3.5.4 Manpower Planning ………………………………………………………...124 3.5.5 Personnel Management ……………………………………………………. 125 3.5.6 Manpower Requirement in the Production of Concrete ……………….125 3.6 Organization’s Staff Training ………………………………………………. 127 3.7 Objectives of Personnel Training ……………………………………………128 3.8 Relationship between Education and Training ………………………………129 3.9 Production Capabilities ………………………………………………………130 3.10 Workmanship ………………………………………………………………..130

CHAPTER FOUR 4.0 DATA COLLECTION AND EXPERIMENTATIONS 4.1 Data Sourcing and Research Methods ………….……………………………….132 4.1.1 Secondary Data ………………………………………………………………. 132 4.1.2 Primary Data …………………………………………………………………..133 4.1.3 Data Collection Techniques Adopted …………………………………………133

x 4.1.4 Sampling and laboratory Experimentations ……………………………………134 4.2 Presentation of Results of Experiments Conducted …………………………..137 4.2.1 Test NO.1 (Specimens 1-3) – Compressive Strength (CS)…………………..137 4.2.2 Test NO.4 (Specimen 4) Test for Presence of Deleterious Substances ……...142 4.2.3 Test NO 5 (Specimen 5)- Purity of Water for Works …………..……………145 4.2.4 Test NO.6 (Sample 6) Particle Size Distribution (Grading) …………………147 4.2.5 Test NO.7 (Sample 7) Specific Gravity Tests ………………………………. 167 4.2.6 Test NO.8 (Sample 8) Soundness of Cement Test …………………………. .169

CHAPTER FIVE 5.0 DISCUSSIONS AND FINDINGS …………………………………………….171 5.1 Presentations, Analysis and Interpretation of Results …………………………..171 5.2 Research Findings ……………………………………………………………….171 5.2.1 Work Study on Concrete Production Practices on Sampled Sites ……………171 5.2.2 Batching of Concrete ………………………………………………………….172 5.2.3 Aggregates Dump Sites ……………………………………………………….172 5.2.4 Cement Storage ………………………………………………………………. 172 5.2.5 Compaction of Concrete ………………………………………………………172 5.2.6 Working and Finishing of Concrete …………………………………………..173 5.2.7 Water for the Works …………………………………………………………..173 5.2.8 Curing of Fresh In-Situ Concrete ……………………………………………..173 5.3 Discussion of Laboratory Results …………………………………………...173 5.3.1 Compressive Strength Tests (A,B&C) ………………………………………173 5.3.2 Deleterious Substances Test …………………………………………………175 5.3.3 Specific Gravity Test ……………………………………………………….. 175 5.3.4 Soundness and Setting Time Tests on Cement ………………………………175 5.3.5 Particle Size Distribution Test ……………………………………………….175 5.3.6 Water Purity Test …………………………………………………………….176 5.4 Validating Research Questions ………………………………………………177 5.5 Validating Research Hypothesis ……………………………………………..179

xi 5.5.1 Testing Research Hypothesis ………………………………………………...179 5.5.2 Fundamentals of Quality Control Chart Instrument …………………………180 5.5.3 Application of Control Charts ………………………………………………..181 5.5.4 ANOVA One-Way T-Test …………………………………………………...188

CHAPTER SIX 6.0 CONCLUSIONS, SUMMARY AND RECOMMENDATIONS 6.1 Summary of the Study …………………………………………………….. 202 6.2 Conclusions of the Study …………………………………………………...204 6.3 Recommendations of the Study …………………………………………… 205 6.4 Developed Concrete Production and Management Practice Tools………….205 6.4.1 Developed Site Concrete Production Check-list …………………………... 205 6.4.2 Developed Site Concrete Production and Management System Models ….. 206 6.5 Research Contribution to Knowledge ………………………………………..211 6.6 Suggestion for Further Studies … …………………………………………...211 BIBLIOGRAPHY …………………………………………………… 212 REFERENCES ……………………………………………………….215

xii LIST OF TABLES

TABLE TITLE PAGE Table 1.1: Statistics of Building Collapse in Some States in Nigeria ……………….4 Table 2.1: Composition of Oxide in PC ……………………………………………25 Table 2.2: Principal Compounds in PC …………………………………………….26 Table 2.3: Recommended Composition of Standard Sand ………………………..28 Table 2.4: Recommended Compressive Strength of Cement ……………………..30 Table 2.5: Percentage passing of different sizes of aggregates ……………………35 Table 2.6: Grading Requirements for Coarse and Fine Aggre ASTM C33 ……….36 Table 2.7: Grading Requirements for Coarse and Fine Aggre ASTM C637 ……...37 Table 2.8 Proportion by Weight of Coarse to Fine Aggregate ……………………38 Table 2.9: Grading Zones of the Fine Aggregates ……………………...... 39 Table 2.10: Specific Gravity of Cement and Aggregates …………………………41 Table 2.11: Limits of Deleterious Substances in Aggregates ……………………..45 Table 2.12: Groups of LWC ……………………………………………………….63 Table 2.13: Physical Properties of LWA ………………………………………… 65 Table 2.14 Typical Data for 10mm-20mm No-Fines Concrete ……………………68 Table 2.15 Estimated Quantities of Materials required /m3 of Concrete …………..71 Table 2.16 Estimated Materials required for Concreting 1m2 of Surface ………….72 Table 2.17 Batch Volume of Materials for various Mixes …………………………74 Table 2.18 Sizes of Farma ………………………………………………………….74 Table 2.19 Volume of Various Gauge Boxes ……………………………………...75 Table 2.20 Recommended Concrete Mixing Time …………………………………77 Table 2.21 Recommended Slump of various Types of Works - ACI 211–1–91 …...88 Table 2.22 Results Showing How Concrete Becomes Stronger in Age ……………96 Table 2.23 Summary of Defects Developed in Concrete during Construction ……103 Table 3.1 Influencing Factors of Quality of a Product …………………………...116 Table 4.1 Mean Values of Compr. Strength of Unwashed Aggregates. ………… 138 Table 4.2 Mean Values of Compr. Strength of Unwashed Aggregates …………...141 Table 4.3 Mean Values of Compr. Str. Pilot Lab. Tests …………………………...142 Table 4.4: Deleterious Substances Test Results …………………………………...144

xiii Table 4.5 Recommended National Water Standard ………………………………….147 Table 4.6 Particle Size Distribution Test Result …………………………………...... 148 Table 4. 7 Particle Size Distribution Test Results ……………………………………150 Table 4.8 Particle Size Distribution Test Results… ………………...... 152 Table 4.9 Particle Size Distribution Test Results of Unwashed Specimen…….…....154 Table 4.10 Particle Size Distribution Test Results Unwashed Specimen…………….156 Table 4.11: Particle Size Distribution Test Results Unwashed Stone Specimen ……159 Table 4.12: Particle Size Distribution Test Results Unwashed Specimen H ….…...... 161 Table 4.13 Particle Size Distribution Test Results Washed Specimen E …...…….....163 Table 4.14: Particle Size Distribution Test Results Unwashed Specimen J .………..165 Table 4.15: Specific Gravity of Unwashed Aggregates ……………………………..168 Table 4.16: Specific Gravity of Washed Aggregates …………………………...... 169 Table 5.1 Relationship Btwn Compr. Stre. Test Results of 3 Specimens …………..174 Table 5.2: Data Presentation Format ………………………………………………..180 Table 5.3: ANOVA Test Result Mix 1:2:4 Unwashed Specimen A………………..188 Table 5.4: ANOVA Test Result Mix 1:3:6 Unwashed Specimen F………………...189 Table 5.5: ANOVA Test Result Mix 1:3:6 Unwashed Specimen S ………………..190 Table 5.6: Chi-Sq Test 1:2:4 Mix Specimens A& A ………………………………191 Table 5.7: Chi-Sq Test Mix Washed and Unwashed Specimens C & A ……………193 Table 5.8: Chi-Sq Test 1:3:6 Mix Washed and Unwashed Specimens F & B ………195 Table 5.9: Paired T-Test 1:2:4 Mix Washed and Unwashed Specimens A & A……..197 Table 5.10: Paired T-Test 1:2:4 Mix Washed and Unwashed Specimens …………..199 Table 5.11: Paired T-Test 1:3:6 Mix Washed and Unwashed Specimens ………..200

xiv LIST OF FIGURES

FIGURE TITLE PAGE

Figure 2.1: Constituents of Concrete ………………………………………………17 Figure 2.2: Classification of Artificial Cement …………………………………….19 Figure 2.3: Wet Process for PC Manufacture …………………...... 24 Figure 3.1: The Concept of Quality in Concrete Production and Management … 107 Figure 4.1: Particle Size Distribution of Fine Aggregate (Sample A) ……………149 Figure 4.2: Particle Size Distribution of Fine Aggregate (Sample B) ……………151 Figure 4.3: Particle Size Distribution of Fine Aggregate (Sample C) ……………153 Figure 4.4: Particle Size Distribution of Fine Aggregate (Sample D) ……………155 Figure 4.5: Particle Size Distribution of Fine Aggregate (Sample F) ……………157 Figure 4.6: Particle Size Distribution of Fine Aggregate (Sample A-F)………….159 Figure 4.7: Particle Size Distribution of Fine Aggregate (Sample G) ……………160 Figure 4.8: Particle Size Distribution of Fine Aggregate (Sample H) ……………162 Figure 4.9: Particle Size Distribution of Fine Aggregate (Sample E) ……………164 Figure 4.10: Particle Size Distribution of Fine Aggregate (Sample J) …………...166 Figure 5.1: Mix 1:2:4 Means of Crushing Value for Unwashed SampleA ………182 Figure 5.2: Mix 1:2:4 Range Mean Unwashed Samples …………………………183 Figure 5.3: Mix 1:3:6 Tabulated Means of Crushing Value Unwashed ………….184 Figure 5.4: Mix 1:3:6 Range of Crushing Value for Unwashed Samples ………...185 Figure 5.5: Mix 1:2:4 Mean of Curing Value for Unwashed Samples ……………186 Figure 5.6: Mix 1:2:4 Range of Curing Value for Unwashed Samples ………….187 Figure 5.7 Effective Human Resource Utilization Pattern ……………………….207 Figure 5.8: Cement Sourcing and Management Chart …………………………....208 Figure 5.9: Data Sourcing and Utilization Chart ………………………………….208 Figure 5.10: Plants/Equipment Sourcing and Utilization Chart …………………209 Figure 5.11: Sourcing and Utilization of Aggregates Chart ………………………210

xv ABSTRACT

The versatility in-use of concrete for buildings and other infrastructures of necessity made concrete an important element of construction. Yet failure of concrete occurs more frequently at construction stage even when it seemed that mix ratio and design load calculations are adequate. This therefore suggests a missing gap in specification and the production of good site concrete. Literature survey confirms poor quality of concrete and use of sub-standard materials of concrete in the production of concrete as among the factors contributing to structural concrete failure in building. This research investigated presence and effect of deleterious substances in materials of concrete on the quality of the concrete structure. To achieve this, observations of concrete practice among project sites were undertaken and specimens of materials for concrete works from sampled ‘on-going’ project sites were obtained and investigated in the laboratory for the presence of deleterious substances, aggregate particle size distribution, aggregates specific gravity and compressive strength. The study further sampled and tested specimens of Ordinary Portland Cement for soundness and quality and fitness test was also conducted on sampled specimens of Water for the Works. Results obtained revealed excessive content of chloride, co2, nitrates, sulphates known to be destructive to concrete, in large quantities in some of the materials tested. The findings further revealed that their presence reduced drastically the compressive strength of the concrete elements produced with them. Data from results obtained were further tested using SPSS 17.0 statistical tools, ‘ANOVA’, ‘Paired T-Test’, ‘Chi-Square’ and ‘Quality Control Charts’ to test and validate the research hypothesis. The graphical results obtained from the QCC test indicated a non-random pattern which contradicted aspects of the quality control chart rules. The means, frequencies and standard deviations obtained from the ANOVA, Chi-square and Paired T-test statistical tools tested were at variance to one another in all the cases tested, thus corroborating the stud postulation. The study developed concrete production model as well as concrete check-list to guide site operators and managers in the regular production and management of site concrete. Recommendations include that concrete designers must urgently incorporate in the contract documents specifications for the compulsory test of proposed concrete materials by contractors before and during site concrete productions as an additional requirement to the traditional specification of mix ratios and compressive strength tests.