SUSTAINABLE USE OF WASTE CRUSHED ROCK DUST AS FILLER MATERIAL IN CONCRETE: PERFORMANCE AT ELEVATED TEMPERATURESN. Venkata Sairam Kumar and K.S. Sai Ram
Worldwide, cement and concrete production is not an environmental friendly process and consumes natural resources and also responsible for the emission of carbon dioxide. In India, it is estimated that out of 125 million tones of crushed stone aggregate produced every year, 17.8 million tones is crushed rock dust (CRD) which is presently used for land filling causing environmental problems such as loss of fertility of soil. The properties of concrete with CRD as partial replacement of cement are not studied till date. This experimental study presents the effect of partial replacement of cement by crushed rock dust (CRD) as filler material in concrete when subjected to elevated temperatures. Ordinary Portland cement (OPC) is partially replaced with CRD in five percentages 0%-control concrete: (CC), 10% (CR1), 20% (CR2), 30% (CR3) and 40% (CR4)) by weight. The CC and CRD concrete specimens are subjected to elevated temperatures of 200 oC to 800 oC for 2 hours using an electrically controlled furnace. Ultrasonic pulse velocity (UPV), Mass loss, compressive strength, surface cracking and color change are evaluated at elevated temperatures. Additionally, the micro-structural properties of CC and CRD concrete at ambient and at elevated temperatures is analyzed using scanning electron microscope (SEM). At ambient temperature, the test results of concrete with CRD up to 30% showed enhanced UPV values and compressive strength than CC. No visible cracks are observed on CC and CRD concrete surface exposed up to 400 oC. UPV values obtained at elevated temperatures with CC and CRD concretes are in good agreement with mass loss and compressive strength values. The results signify that the partial replacement of cement up to 20% with CRD showed the best performance than CC at elevated temperatures and are supported by SEM analysis. The partial replacement of cement up to 20% by CRD reduces cement usage and thereby mitigating global warming.
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