The deterioration of admixture concrete in a sulphate environment

Abstract

The deterioration mechanism of concrete with mineral admixtures subjected to drying-wetting cycles in a 10 % sodium sulphate solution was studied. Plain concrete without fly ash addition, concrete with 10 %, 20 % and 30 % fly ash addition, and a concrete with 20 % fly ash and 30 % slag addition were used. Through the experiment, the weight loss, the relative dynamic modulus of elastically (RDME), the compressive strength loss and the damage layer thickness (Hf ) of the concrete were measured. Furthermore, scanning electron microscopy, X-ray diffraction and thermal analysis were used to investigate the corrosion products of the concrete. The test results show that the ultrasonic velocity in the damage layer decreases and the Hf of the concrete increases as the corrosion time grows, indicating that the deterioration degree of the concrete increases. There is a significant relationship between the RDME and the Hf after 210 d. The deterioration degree of the concrete decreases with an increase in the fly ash content. However, the sulphate resistance property of the concrete significantly decreases with 30 % fly ash content. When mixed with 20 % fly ash and 30 % slag, the sulphate resistance property of the concrete is the best.