Economical Concrete Mix Design Utilizing Blended Cements, Performance-Based Specifications, and Pay Factors.

摘要

This report showcases several new approaches of using materials science and structural mechanics to accomplish sustainable design of concrete materials. The topics addressed include blended cements, fiber-reinforced concrete (FRC), internal curing with lightweight aggregate, and statistical process control (SPC). Materials, methodologies, and test methods to enhance the performance and durability of concrete are addressed. Properties of pozzolans, blended cements, fly ashes, and other materials, along with proposed categories of highperformance concrete (HPC) mixtures using high-volume fly ash are briefly described. Early-age cracking and drying shrinkage are addressed in detail, as they both reduce load-carrying capacity and accelerate deterioration, resulting in increased maintenance costs and reduced service life. New developments in HPC materials using FRC are proposed, and it is shown that considerable cost savings can be realized by using fiber concrete mixtures. Internal curing techniques as a means of improving the quality of concrete using pre-soaked lightweight aggregate as an internal water supply were studied. The superior results of internally cured samples with lightweight aggregates, especially sintered bottom ash, indicate a great potential for using them in hot-weather concreting or when external curing is not possible. A new method for statistical data processing of concrete strength data also is presented. Technical tools were developed to improve performance-based specifications and statistical process control methods using cumulative sum (CUSUM) and exponentially weighted moving average (EWMA). Both of these approaches allow for process control and quality control (QC) monitoring of the materials. This report concludes with specifications for quality assurance (QA) and introduces quality measures as criteria for reducing the costs.