Properties of MSFAC Long-Term Exposure to Sodium Sulfate Solution

Experiments were conducted to study sulfate attack on concrete made machine-made sand and fly ash (MSFAC). The cubes with dimensions of 100 mm were cast and immersed in sodium solution with sulfate-ion concentration of 50000mg/L and tested after exposed for 30, 90, 180, 270, 360 and 540 days. The powder samples were made by steps of drilling, cutting and grinding. The sulfate-ion contents of concrete at different depths were measured by the chemical titration method. The results show that the sulfate-ion content of concrete decreased with depth, the sulfate-ion entered concrete by diffusion, permeation and capillary absorption. The sulfate-ion content of concrete decreased with the increasing replacement of cement by fly ash, and also decreased with the increase of exposure time when 30% of cement is replaced by fly ash. There are some advantages of using fly ash for concrete with machine-made sand to resist sulfate attack.