Date of Graduation
Statler College of Engineering and Mineral Resources
Civil and Environmental Engineering
Julio F Davalos
Self-consolidating concrete (SCC) is becoming a popular material in the concrete industry, due to ease of placement in congested reinforcement, reduced labor and equipment, nonsegregating character, and excellent surface finish. In spite of its several advantages, SCC is exceedingly sensitive to aggregate grading, size, admixtures, and filler contents. Though many studies have been conducted on rheological behavior of SCC, there is limited information on effects of aggregate size, grading, mineral admixture types, and fillers on durability, shrinkage and cracking properties.;In this study 17 SCC mixtures were initially developed using local aggregates, fly ash, slag, limestone fillers, commercial silica fume, viscosity-modifying admixtures (VMA), high-range water-reducing admixtures (HRWRA), shrinkage-reducing admixtures (SRA), and steel fibers. The mixtures were evaluated for slump-flow, visual stability, J-ring blocking test, L-box passing ability, and column static segregation. Comparisons of results with the concept of workability factors (representing fine fraction) and coarseness factor (representing coarse fraction) that were proposed for normal concrete, indicate that most of the rheological properties of SCC are strongly influenced by admixtures and fillers. Based on fresh properties and strength criteria, six best SCC were selected for in-depth study of strength development with time, free shrinkage, autogenous shrinkage, cracking potential, freeze-thaw, air-void parameters, and rapid chloride permeability.;Results show that compressive strength increased as water/powder ratio decreased and paste volume increased. The ACI prediction equation for limestone SCC underestimated the compressive strength with time. The shrinkage and cracking data showed that mixtures containing higher size of coarse aggregates (25 mm graded) had lower shrinkage and cracking potential compared to 12.5 mm graded aggregates. Autogenous shrinkage contributed significant portions of the total drying shrinkage measured. The data was calibrated for six existing models of shrinkage and finally a modified ACI based model was recommended for these SCC mixtures. SCC with coarse fractions of aggregate cracked later that those with finer fractions of aggregate. However, the inclusion of fibers and shrinkage reducing admixtures significantly reduced potential cracking, and SCC containing fibers improved the post-cracking behavior as well. Though the air-content of most SCC were higher than normal, the air-void parameters were within acceptable limits. This was confirmed by excellent resistance of SCC against freeze-thaw cycles and high durability factors obtained according to ASTM C 666 and C 215. Rapid chloride permeability values of SCC were adequate and close to regular HPC. Further studies on fracture parameters of hardened SCC are recommended. This should follow a full-scale implementation plan for specific structures and long-term monitoring.
Bhattacharya, Arka, "Effects of aggregate grading and admixtures/fillers on fresh and hardened properties of self-consolidating concrete" (2008). Graduate Theses, Dissertations, and Problem Reports. 4357.