Self-Consolidating Concrete (SCC) and High-Volume Fly Ash Concrete (HVFAC)for Infrastructure Elements: Implementation. Report C, Implementation of HVFAConcrete from Laboratory Studies into Bridge Application

This study was performed to examine the effects of cement replaced by high volumes of Class C fly-ash on durability characteristics of concrete up to 120 days. Specifically, this study investigates possibility of amending American Society for Testing and Materials (ASTM) to allow High Volume Fly-ash (HVFA) concrete to cure until later ages prior to testing instead of 28 days. Five mix designs were compared with varying fly-ash percentages from 0 to 70% (by total cementitious mass). No other additives were present in any of the five mix designs. Water to-cementitious ratio (w/cm) and total cementitious material remained constant as 0.40 and 750 pounds per cubic yard respectively. Both plastic concrete and hardened concrete properties were examined. The replacement of cement by fly-ash resulted in the concrete exhibiting adequate 28 day strength, stiffer moduli, lower chloride permeability, improved resistance to freezing and thawing, and improved abrasion resistance at 50% fly-ash replacement when compared to a baseline mix. At 70% fly-ash replacement, the concrete never reached equivalent properties to the other mixes. As the age and compressive strength of all mixes increased, so did the abrasion resistance and durability factor. Accelerated curing at 100°F (37.8°C), 130°F (54.4°C), and 160°F (71.1°C) proved to be detrimental to the concrete at all fly-ash levels, with higher temperatures causing increased damage. An increase in compressive strength was seen in the first few days prior to a decrease in compressive strength.