THE DETERIORATION OF ADMIXTURE CONCRETE IN A SULPHATE ENVIRONMENT

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 (H f ) 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 H f 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 H f 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.