Improve the Quality of Concrete, Improve the Quality of Construction
Quality measurement is not prevalent in the concrete industry and quality investment is not seen as potentially generating a positive return. Improving Concrete Quality examines how and why concrete quality should be measured, and includes instruction on developing specifications with the aim of improving concrete quality.
Reduce Concrete Variability: Reduce Costs and Increase Volume
The first part of the book considers the tangible and intangible benefits of improved quality. The later chapters explore concrete strength variability in detail. It provides a greater grasp of the variation in concrete, as well as a deeper understanding of how material variability affects concrete performance. The author discusses the components of variability (material, manufacturing, testing) and provides steps to measuring and reducing variability to improve the quality of concrete. The text also contains a chapter on data analysis for quality monitoring and test results.
Come Away with Practices and Tools That Can Be Applied Immediately:
- Provides techniques and how specifications can improve concrete quality
- Offers a clear understanding of the link between the materials (cement, SCM, aggregate, water, air), manufacturing, testing variability, and concrete quality
- Includes information on analyzing test data to improve quality
Improving Concrete Qualityquantifies the benefits of improved quality, and introduces novel ways of measuring concrete quality. This text is an ideal resource for quality personnel in the concrete industry. It also benefits architects, engineers, contractors, and researchers.
Table of Contents
How Good Is Your Quality?
Costs Due to Poor Quality
Why Is It So Important to Lower Standard Deviation?
Is It Worthwhile Not to Invest in Improved Quality under Certain Circumstances?
2010 NRMCA Quality Measurement and Bench Marking Survey
How Can a Concrete Producer Improve Quality?
Variation in Concrete Strength Due to Cement
Cement from a Given Source Varies between Shipments
How Should a Ready Mixed Concrete Producer Use ASTM C917?
Better Understand Concrete Variability and Lower It!
Problems and Optimize Mixture
How Should a Cement Producer Use ASTM C917?
Variation in Concrete Strength Due to Water and Air Content
Mixing Water Content Variation and Its Effect on Compressive
Air Content Variation and Its Effect on Strength Variation
Combined Effect of Water and Air Content Variation on
Sources of Water
Washwater in Truck Mixer Drum from Previous Load
Free Water from Aggregates
Water Added at Slump Rack
Water Added at Job Site
Variations in Mixing-Water
Effect of Mixing-Water
Plant Tests for Quality Assurance
Variation in Concrete Strength and Air Content Due to Fly Ash
Variability of Fly Ash Shipments from Given Source
Fly Ash Testing Required by ASTM C311 and C618
Suggested Producer Actions
Strength Activity Index
Summary of Suggested Producer Actions
Variation in Concrete Performance Due to Aggregates
Variability of Aggregate from Single Source
Aggregate Properties and Their Effect on Concrete Mixture
Proportioning and Performance
Relative Density and Absorption of Aggregate
Aggregate Moisture Content
Void Content in Coarse Aggregates
Void Content of Fine Aggregates
Material Finer than 75 μm (No 200)
Using Aggregate Test Results
Table 6.1 Test Results
Table 6.2 Test Results—Tests Conducted by the Aggregate
Table 6.2 Test Results—Tests conducted by Concrete Producer
Basic Statistical Parameters
Predictions Using a Normal Distribution
Types of Variation
Common Causes and Special Causes
Average and Range Charts
Moving Average and Moving Range Charts
Variation in Concrete Performance Due to Batching
ASTM C94 Scale Accuracy and Accuracy of Plant Batching
Two Issues with Batching
Variation of Batch Weights and Its Effects
Cementitious Weight Variation and Its Effect on Strength
How Can a Company Improve Batching Accuracy?
Yield Measurements—A Tool to Improve Batching Accuracy
Variation in Concrete Performance Due to Manufacturing
ASTM C94 Requirements for Uniformity of Concrete
Improving Uniformity of Concrete Produced in Truck Mixer
What Can a Company Do to Improve Uniformity of Concrete Produced in a Truck Mixer?
Variation in Concrete Performance Due to Temperature
Effect of Temperature on Setting Time
Effect of Temperature on Early-Age
Effect of Temperature on Mixing-Water
Variation in Concrete Performance Due to Delivery Time
Variation in Concrete Performance Due to Testing
A Measure of Testing Variability
Other Methods of Evaluating Testing
Other Property Measurements
Rate of Strength Gain
ACI Code and Specification Requirements Related to Concrete
Steps to Improve the Quality of Acceptance Testing
Incentives to Testing Technicians
Internal Concrete Testing
Why Test at the Plant When We Can Get Job-Site
Criteria for Plant Testing
Selection of Mixture Classes
Sampling and Types of Testing
Frequency of Testing
Using Job-Site Test Results for Improving Concrete Quality
Acceptance Test Results
Control Chart Limits
Monitoring S of Compressive Strength
Use of Control and CUSUM Charts to Analyze Project
Impact of Specifications on Concrete Quality
Allow Use of Standard Deviations Not Just over Designs
Move from Prescriptive to Performance-Based
Minimum Cementitious Content
Changes to Mixture Proportions after Submittal
Installer and Testing Agency Qualifications
Concrete Acceptance Testing
Current information on Material Properties
Impact of Concrete Quality on Sustainability
Target a Low Standard Deviation
Curing and Overall Testing Quality
Fewer Returned Concrete and Hardened Concrete Issues
Plant and Truck Mixer Maintenance
Batching Accuracy and Yield Measurements
Elements of a Quality Management System for a Concrete Producer
Why Should a Company Have a QMS?
What Are Elements of a QMS and How Does It Improve Quality?
Quality Objectives and Measurement
Field Testing Technicians
Truck Mixer Operators
Laboratory Testing Capabilities
Materials Management and Conformance
Specification Review, Mixture Development, Optimization
Receiving Orders and Record Keeping
Internal Testing at the Plant
Internal Testing at the Job Site
Quality Assurance Test Records
Nonconforming Acceptance Test Results
Returned Concrete and Washwater
Karthik Obla, Ph.D., P.E., FACI, is vice president, technical services, National Ready Mixed Concrete Association (NRMCA). He has over 20 years of experience in concrete materials technology and has interests in quality control/assurance, mixture optimization, specifications, use of recycled materials, durability, and new technology. He is a Fellow of the American Concrete Institute and a winner of ACI’s Young Professional Achievement Award. He has published over 75 technical articles in journals and has presented in several international conferences. He holds a Ph.D. in civil engineering from University of Michigan, Ann Arbor, and is a licensed professional engineer in the state of Maryland. He served as vice-president and president for the ACI San Antonio Chapter. Prior to joining NRMCA, he was technical manager at Boral Material Technologies.
"Extremely comprehensive and practical… The chapter on basic statistics is a must read to clear the concepts required to understand how to analyse data for monitoring quality. Apart from the process - be it regarding material or testing, the author has also covered capability building and training which forms a core part of the entire business."
—Indian Concrete Journal, December 2014
"Many concrete manufacturers neglect to quantify not only the cost of producing poor quality concrete, but the potential savings in the reduction of cementitious content by focusing on standard deviation and tightening controls, particularly with regards to slump control and moisture contents – this book identifies key areas that manufacturers can focus on to improve and realize these savings."
––Charl Marais, Aggregate Industries
"While there are many books on concrete technology, finding one that focuses strictly on improving concrete quality had been difficult until now. Improving Concrete Quality discusses how to improve performance, reduce time and costs, and lower the environmental footprint of concrete while also resulting in an overall improvement in the quality of concrete construction."
—The Concrete Producer, September 2014