| 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. |
