Performance evaluation and lifetime prediction of steel slag coarse aggregate concrete under sulfate attack

The durability of steel slag coarse aggregate concrete limits the application of steel slag in construction engineering. This study carried out the erosion test, material mechanics test, and microscopic test of steel slag coarse aggregate concrete under the action of different mass fractions of sulfate solution to investigate the effect law and mechanism of steel slag coarse aggregate on sulfate erosion resistance of concrete. The deterioration laws of performance indexes such as compressive strength, mass change, and relative dynamic elastic modulus of steel slag coarse aggregate concrete under sulfate erosion were investigated. X-ray diffraction (XRD) and Scanning electron microscope (SEM) were used to examine the erosion products and microstructure changes of samples before and after sulfate erosion, and the GM (1, 1) model of grey theory was used to forecast the service life of steel slag coarse aggregate concrete under various conditions. The results demonstrate that utilizing steel slag instead of coarse aggregate to prepare concrete may significantly alleviate the damage caused by the attack of sulfate solutions. And in 15% sulfate erosion environment, the maximum compressive strength increase rate of 20.7% was obtained when the steel slag substitution rate was 60%. Microscopic study reveals that the active components (such as dicalcium silicate (C2S) and tricalcium silicate (C3S)) in steel slag can promote the production of hydrated calcium silicate gel in concrete, improving the strength and durability of the material. To a certain extent, the addition of steel slag can improve the sulfate resistance of concrete. The prediction results of the GM (1, 1) model show that the service lifetime of concrete with 60% steel slag coarse aggregate substitution rate under sulfate solution erosion is better than that of the other three groups, and the predicted results are compatible with the experimental results.