Structural Performance of Self-Cementitious Fly Ash Concretes with Glass Aggregates

Alternative concretes are needed to reduce the significant environmental impact of ordinary portland cement concrete construction. This paper reports findings from a study that evaluated the structural performance of environmentally friendly concretes made with self-cementitious fly ashes as the sole binders and pulverized reused glass as the aggregate. Such an evaluation is essential to moving these new concretes out of the laboratory and into general structural applications. Six reinforced beams (two each of three designs) were tested using three fly ash binders and a conventional concrete control mix (total of 24 beams). The beams were configured to evaluate the performance of the concretes under three different failure mechanisms: (1) tension-controlled failure, in which the concrete crushes after the longitudinal steel yields; (2) compression-controlled failure, in which the concrete crushes before yielding of the longitudinal steel; and (3) shear-controlled failure, in which the concrete cracks in the absence of shear reinforcement. Results from these beam tests were compared with conventional concrete control specimens and standard capacity predictions. The fly ash/glass tension-controlled specimens behaved similar to the conventional concrete specimens. In the compression-controlled and shear-controlled beams, the conventional concrete outperformed the fly ash/glass concrete. With respect to the applicability of standard capacity equations to fly ash/glass aggregate concretes, observed beam capacities either closely approached or exceeded predicted capacities; although, it was determined that some empirical factors should be adjusted to account for noted differences in observed stress-strain responses.