Effect of Mechanical and Chemical Activation of Fly Ash on the Properties of Fly Ash Bricks

Abstract

Fly ash (FA) is a byproduct generated from the power plants, whose disposal is becoming the biggest threat to the environment. The reactivity of FA lies upon various factors, most important of which are mineralogical and chemical composition of FA, curing temperature and activation process used. The activation process includes mechanical activation and chemical activation. Hence, in this investigation effort has been given to analyze the properties of brick prepared with mechanically/chemically activated FA which can replace the use of cement in the brick manufacturing units. To proceed with, three types of activation processes are considered as variable i.e. (1) mechanical activation, (2) chemical activation with lime and (3) chemical activation with solution of Sodium hydroxide (NaOH) and Sodium silicate (Na2SiO3). The FA is activated with these activation processes individually or in combination of them to prepare 18 numbers of mixes. For each mix, ten numbers of brick samples were prepared to test their compressive strength and water absorption properties. After considering the variables it is observed that, due to increase in mechanical activation of FA the compressive strength of bricks increases and simultaneously the percentage of water absorption decreases. At the same time, for chemical activation with lime, the strength increased with increase in lime content up to 10% and reduces thereafter. Further, for chemical activation by NaOH and Na2SiO3 the strength of brick was inversely proportional to the molarity of NaOH but in case of water absorption, concentration of chemical is directly proportional to the water absorption capacity of brick. Hence, the mix activated with maximum mechanical activation, 10% lime and 8 molar NaOH solution achieved highest strength i.e. 78.66 kg/cm2 and lowest water absorption value of 9.2% by weight.KeywordsFly ash brickChemical activationMechanical activationCompressive strengthWater absorption