ALKALI SILICA REACTION OF CONCRETE DISSERTATION

Abstract

Concrete is the most widely used construction material in our country due to its various advantages over other building materials, but durability in concrete is a crucial issue. Due to various reasons, its durability gets affected, and the Alkali silica reaction is one. Alkali silica reaction is a deleterious reaction that produces a gel across the aggregate boundary and has hygroscopicity property. The gel gets expand upon the absorption of moisture from the surrounding environment and exerts pressure on the surrounding concrete. This expansion is not a problem if expanded gel fills the cavity present in concrete, but the volume produced is more than the volume of pores present in concrete. It exerts pressure on surrounded concrete, and if exerted pressure is larger than the tensile capacity of concrete, it produces microcracks. These microcracks produced by ASR lead to a decrement in mechanical properties like Compressive strength, Modulus of Elasticity, Flexural strength and passage for chemical ingress and corrode the reinforcement. By adding Supplementary Cementous material, ASR can reduce up to a certain extent. Because of Modelling of Alkali Silica Reaction, we can predict the chemical reaction kinetics of ASR and mechanical effects thus the long-term behaviour of structures suffering from ASR and reproduce it beforehand. There are many approaches of modelling in field of ASR but main focus of this study is on theoretical or analytical approach of modelling. In this study analytical model for kinetics of the alkali silica reaction is presented. Effect of various constituent of ASR on expanded gel are observed. Importance of moisture content is confirmed from the study. This study confirms that when alkalis are in smaller magnitude than silica, this results in less amount of harmful Expanded alkali silicate gel formation. Generation of this gel also adversely affected by concentration of the water content, smaller moisture content leads to less generation of expanded alkali silicate gel.