Early-age residual stress and stress relaxation of high-performance concrete containing fly ash

Abstract

High-performance concrete (HPC) is widely used. However, HPC with a low water-to-binder ratio generally experiences rather high autogenous shrinkage. If restrained, autogenous shrinkage can result in the development of residual tensile stresses that may be sufficient to cause cracking at an early age. Fly ash (FA) has been utilised as a mineral admixture to reduce shrinkage and improve the durability of HPC. Although shrinkage development and early-age cracking resistance of HPC under restraint have been investigated, research on the stress relaxation of HPC with FA by ring tests is limited. Restrained ring tests on the cracking resistance of HPC using FA as 0, 20, 35 and 50% by weight replacements of cement were conducted. The test results showed that: free shrinkage decreased with an increase in FA replacement ratio; the actual strain in the steel ring decreased with increasing FA replacement; the residual stress of the concrete ring decreased with increasing FA replacement; the ratio of maximum residual stress to time-dependent splitting tensile strength decreased with an increase in FA replacement; the relaxed stress was almost constant when the FA replacement ratio increased from 0 to 20%, and decreased when the FA replacement ratio increased from 20% to 35% and 50%; and the cracking potential based on stress rate decreased when the FA replacement ratio increased from 0 to 20% and 35%, and increased when the FA replacement ratio increased from 35% to 50%.