Development of Statistical Models for Mixture Design of High-Volume Fly Ash Self-Consolidating Concrete

摘要

Self-consolidating concrete (SCC) in the fresh state is known for its excellent deformability, high resistance to segregation, and use, without applying vibration, in congested reinforced concrete structures characterized by difficult casting conditions. Such concrete can be obtained by incorporating either mineral admixtures such as fly ash (FA) or viscosity-modifying admixtures (VMA). The use of VMA has proved very effective in stabilizing the rheology of SCC, and recent researches are focused on the development of new, cheaper VMAs compared with currently available, costly commercial ones. Research to produce an economical SCC with desired properties was conducted over the last few years with the use of FA. In the present study, 21 statistically balanced concrete mixtures were investigated to minimize the use of high-range water-reducing admixtures (HRWRA) and to optimize the use of fly ash in SCC. The minimum use of HRWRA and optimum use of FA were desired in this study. Four independent variables such as total binder content (350 to 450 kg/m~3), percentage of FA as cement replacement (30 to 60% by mass), percentage of HRWRA (0.1 to 0.6% by solid mass), and water-binder ratio w/b (0.33 to 0.45) were used for the design of SCC mixtures. The fresh concrete properties were determined from slump flow, V-funnel flow, filling capacity, bleeding, air content, and segregation tests. The mechanical properties and durability characteristics of SCC such as compressive strength, freezing-and-thawing resistance, rapid chloride permeability, surface scaling resistance, and drying shrinkage were determined to evaluate the performance of SCC. Four statistical models to predict the slump flow, 1- and 28-day compressive strength, and the rapid chloride permeability of SCC were developed and their performances were validated. The models can be used as economical tools for the optimized design of FA SCC mixtures with desired properties in practical applications.