This research evaluates the performance of fly ash concrete designed for highway pavements containing three different types of aggregate gradations. The classifications are called gap-graded, dense-graded, and optimum-graded aggregates in this study. A total of seven concrete mixtures were cast for the research. The control concrete mixture is the one used by the North Dakota Department of Transportation (NDDOT) to construct their highway pavements. It contains cementitious material of 594 lb/yd3 (334.2 kg/m3) of concrete with fly ash replacement amount of 30% for the Portland cement. The mixture is designed for 1-1 ?¢ in. (25-38 mm) of slump, and 6% air content. Three concrete mixtures were cast using the gap-graded aggregates including the control mixture; the other two mixtures contained no air entrainment and 4% air content respectively. Similarly three concrete mixtures were cast using dense-graded aggregates and contained no air entrainment, 4%, and 6% air contents. One concrete mixture was cast using optimum-graded aggregates with 6% air content. Compressive strength of the control mixture was found and all the mixtures were designed for this compressive strength, and 1-1?¢ in. (25-38 mm) slump. All concrete mixtures used 30% fly ash replacement of Portland cement. In this study various ASTM/AASHTO tests such as compressive and flexural strength; specific gravity, absorption, and voids; rapid chloride ion permeability; resistance of concrete to rapid freeze and thaw; and microscopical determination of air-void system were conducted to find the strength and durability characteristics of the concrete mixtures. The beneficial effects of dense-graded aggregates are shown on the durability of concrete highway pavements.
Abstract