STRENGTH AND DURABILITY OF CONCRETES CONTAINING 50-PERCENT PORTLAND-CEMENT REPLACEMENT BY FLY-ASH AND OTHER MATERIALS

Results are presented from an investigation on the compressive strength and durability of concretes containing substitute materials at a 50% replacement level (by mass) of Portland cement. Seven fly ashes (sub-bituminous, bituminous, and lignitic), together with limestone and an inert material (silica flour), were used as replacement materials. Durability studies included freeze-thaw testing (ASTM C666A), scaling resistance (ASTM C672), and abrasion resistance (ASTM C944). The air void system was assessed using the modified point count method of ASTM C457. The results indicate that although concretes with a 50% replacement level of cementitious material did not perform as well as the control concretes with no replacement, such concretes were able to meet minimum durability requirements. As anticipated, air-entrainment is the overriding factor that allows concrete to meet freeze-thaw durability requirements. In the context of this study, compressive strength does not appear to be a significant factor in freeze-thaw durability. Additional results are discussed.