Utilization of Fly Ash and Rice Husk Ash as High Volume Replacement of Cement

Abstract

Utilization of fly ash and rice husk ash as high volume replacement of cement was evaluated by investigating the fresh and hardened properties of concrete. Mix proportions were prepared for cement replacement of 50 per cent and 70 per cent by fly ash, rice husk ash and the combination of these two. Control mix with no fly ash and rice husk ash was also prepared and tested. The dosage of super plasticizer was maintained at 2 per cent by weight of cement for all cases. Test results indicated that the compressive strength and density of control mixes was higher than mixes containing fly ash and rice husk ash as partial replacement of cement, however, setting time and water absorption of control mix was lower than mixes containing fly ash and rice husk ash as partial replacement of cement. Control mix performance was worst in case of acid attack tests. Test results also indicate that the mixes containing fly ash achieved higher compressive strength than mixes containing rice husk ash. The setting time was longer for the mix containing only fly ash than mix containing only rice husk ash as cement replacement. The water required to maintain the required slump was highest for mix containing rice husk ash. The fresh concrete density of the mixes containing fly ash was higher than that of mixes containing rice husk ash. In case of sulfuric acid, fly ash mixes performed better than and rice husk ash mixes, however, in case of hydrochloric acid the performance of rice husk ash was comparatively better than that of fly ash mixes. Water absorption for rice husk ash mixes was higher than of the fly ash mixes. It can be concluded that high volume replacement of cement by fly ash and rice husk ash is feasible. The performance of fly ash mixes compared to mixes containing rice husk ash was significantly better in all tests performed, except hydrochloric acid attack test.