Performance of Concrete Containing Water-Hyacinth Ash (WHA) as Cement Replacement: Resistance to Elevated Temperature and Seawater Exposures

The current research aims at determining the resistance of concrete mixtures containing the ashes resulting from the water-hyacinth plants [1] as a cement replacement to elevated temperature and to seawater. Two types of water-hyacinth ashes (WHA); burnt in open air and burnt in a closed oven at 600°C for 30 minutes were used as partial replacement materials of ordinary portland cement in concrete mixtures with percentages of up to 15% (by weight of cement). The concrete mixtures were designed with three coarse aggregates types; gravel, dolomite, and basalt. To study the resistance to high temperatures, the specimens were exposed to different elevated temperatures of 200, 400, and 600°C and compared to 25°C as a reference. To investigate the resistance to seawater, three curing regimes were followed; curing in laboratory atmosphere (25°C and 50% relative humidity), immersing in seawater during the entire curing period of one month, and subjecting to drying-wet cycles composed of one-day at laboratory atmosphere and one-day in seawater for a total period of one month before testing. The concrete mixes containing WHA were compared with plain concretes and others proportioned with 10% silica fume. The results revealed significant effect of WHA percentages, coarse aggregates types, and curing methods on the concrete strength. With up to 10% cement replacement with WHA, there was no reduction in strength relative to the reference. The optimal replacement value was around 5%.