Effects of Fly Ash on Early-Age Properties and Cracking of Concrete

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Title: Effects of Fly Ash on Early-Age Properties and Cracking of Concrete

Author(s): Inamullah Khan, Arnaud Castel, and Raymond Ian Gilbert

Publication: Materials Journal

Volume: 114

Issue: 04

Appears on pages(s): 673-681

Keywords: cracking age; fly ash; shrinkage; tensile creep

Date: 7/1/2017

Abstract:
This paper focuses on the effects of fly ash on early-age mechanical and viscoelastic properties of concrete and on early-age cracking. Fly ash is a supplementary cementitious material that is mainly used to increase the durability of concrete. The effect on shrinkage-induced cracking of replacing some ordinary portland cement (OPC) with fly ash has not been studied previously. Material properties such as compressive strength, indirect tensile strength, and elastic modulus were measured with different percentage replacements of OPC with fly ash. Tensile creep and drying shrinkage were also measured on two types of specimens by using two different experimental techniques. The cracking age of plain concrete was observed by using a restrained ring test. Results revealed that the strength evolution of fly-ash-blended concrete is lower than the corresponding OPC concrete and the age at which restrained shrinkage cracking first occurs is also reduced. Slightly higher tensile creep coefficients were observed for fly-ash-blended concrete compared to OPC concrete, but drying shrinkage was not altered to any great extent.