EFFECTS OF ASH CONTENT AND CURING TIME ON COMPRESSIVE STRENGTH OF CEMENT PASTE WITH RICE HUSK ASH
Keywords:
Rice husk ash, Pozzolanic activity, Compressive strength, Blended cement pasteAbstract
This research investigates the effect of ash content and curing time on the compressive strength and microstructural development of cement pastes blended with rice husk ash(RHA). To explore the use of RHA obtained from a typical biomass power plant as a supplementary cementitious material, plain Type I ordinary Portland cement (OPC) paste and OPC pastes with 5 and 25 wt% RHA were cast and tested for compressive strength at 1, 7, and 28 days of curing. Scanning electron microscopy (SEM) study and thermogravimetric/differential thermal analysis (TG/DTA) were used to follow the microstructural development and the extent of hydration and pozzolanic reactions of the pastes, respectively. The compressive strengths of all pastes were found to increase with curing time. The OPC+5%RHA paste exhibited higher compressive strengths than the plain OPC paste only after 7 days of curing, while the OPC+25%RHA paste only showed lower compressive strengths than the plain OPC paste at all curing times. The higher compressive strength was supported by the greater growth and concentration of the ettringite needles in the SEM micrographs. The extents of cement hydration reaction and pozzolanic reaction in relation to strength development are discussed based on the Ca(OH)2 content from TG/DTA.
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