Study on the Influence of Processed Rice Straw Ash as a Binder on Compressive Strength and Water Absorption of Alkali Activated Mortar

Abstract

Major concern today with cement production is its environmental issues. For the sustainable development the usage of cement is reduced day by day in the construction sector. The alkali activated binders (AAB) are eco-friendly and they do not cause any environmental effects which can be used as one of the alternatives to cement. AAB is a hardened cementitious paste made of industrial pozzolanas such as Fly Ash and GGBS, and alkaline solutions like sodium hydroxide and sodium silicate. Currently Fly Ash is the most commonly used AAB; but fly ash may become scarce because coal- fired power plants are declining due to the increasing popularity of renewable energy.
 Rice straw ash (RSA) is an agricultural waste which has the pozzolanic characteristics and contains about 70%-80% of amorphous silicon dioxide (SiO2) when burnt at 650c. Rice straw can be used as replacement of fly ash in Alkali Activated Mortar (AAM) by burning it at 650c and milling it for 10 minutes, 20 minutes and 30 minutes. The specimens are casted for Rice Straw based AAM and compressive strength and water absorption are studied for 7.5, 10, 16 molarity of NaOH and also RSA milled for 10,20 and 30 minutes and SEM EDX is studied for the hardened specimen at 28 days. 
 The RSA has significant positive effects on performance of AAM. The replacement of RSA by 20% has shown greater results and as the milling time of RSA is raised the surface area of RSA is increased which in turn resulted in improved strength and as the molarity of NaOH is increased the AAM at 3, 7, 28 and 56 days has the higher Compressive Strength and lower Water absorption.