Rheological and strength properties of fly ash incorporated rapid hardening cement mix

Abstract

Rapid Hardening Portland Cement (RHPC) is used in sites where high initial strength is required and or at instances where removal of formwork is to be done at an early stage. It is widely used in the manufacture of concrete bricks and in mining plants. The main issue regarding RHPC is its high heat of hydration. Addition of Fly Ash can be taken as one of the solutions for this problem. This project investigates in reducing the heat of hydration of RHPC using fly ash. For determining the most optimum cement-fly ash mixture, compressive strength of each mixture with varying fly ash composition was obtained. The cubes were cast with 15%, 25% and 35% of both Class-F and Class-C fly ash. As a result of consistency test, water cement ratio for each mixture was found and used for the proper casting of the cubes. The influence of fly ash on the, mechanical properties (compressive strength) and rheological (yield stress and plastic viscosity) properties of rapid hardening cement as well as the chemical interaction between fly ash and rapid hardening cement were systematically investigated. As a result, the mixture with 25% Class-F showed the maximum compressive strength. It is also observed that yield stress and plastic viscosity changes with fly ash percentage and type.