Deterioration of Cement Pastes Containing Limestone Powder with Different Fineness Exposed to Sulfate Environment at Low Temperature

摘要

Limestone filler and aggregates are used widely in cement production and concrete mixing nowadays, which could be connected with thaumasite formation, and lead to a lack of durability further in sulfate environment. This work deals with the deterioration of cement pastes containing 35% w/w limestone powder with different fineness immersed in MgSO_4 solution at 5°C±2°C for 15 weeks by. Erosion phases are discussed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD). Test results show that visual deterioration of three kinds of cement pastes containing 400-mesh, 800-mesh and 1250-mesh limestone powders has little distinction, and erosion phases are all compound of ettringite, thaumasite, gypsum and brucite. Limestone powders with fineness of 400-mesh could supply enough carbonate needed for thaumastie formation. Increase of limestone fineness further could not accelerate deterioration of cement paste during the external magnesium sulfate attack at low temperature.