Abstract
The purpose of this study was to investigate availability of rice straw ash as concrete admixture, by analyzing properties of mortars using rice straw ash with replacement ratio in comparison with plain mortar. In order to measure amount of $SiO_2$ of rice straw ash, XRF(X-ray fluorescence) analysis was tested. Also to evaluate properties of mortars using rice straw ash, mortar flow, cement setting time, compressive strength was tested and micro-structure of rice straw ash was observed using SEM(scanning electron microscope). The results of experimentation are as follow. As a result of XRF analysis, the higher firing temperature of rice straw, the higher amount of $SiO_2$. Through observation of SEM, it is found that grain shape of rice straw ash has round form and dense structure while grain shape of rice husk ash has angular form and porous structure. Flow of mortars using rice straw ash measured 190~220mm and using rice straw ash tend to increase mortar flow with replacement ratio. When using rice straw ash, cement setting time was delayed up to 1 hour in initial setting time and was delayed up to 1 hour 30 minutes in final setting time. In mortar compressive strength test results, effect of strength increase was presented clearly. Compared to plain mortar, compressive strength of mortar using rice straw ash measured level of 105~116%. From the results, it seems that using rice straw ash as concrete admixture is available.