Study on the deterioration characteristics of limestone powder cement mortar under sulphate attack at different temperatures

Replacing some cement clinker with limestone powder can effectively reduce carbon emissions. However, there are certain differences in the sulfate resistance of limestone powder cement mortar under different temperature environments. This paper systematically investigates the macro-deterioration of limestone powder cement mortar under low (5 degrees C), normal (20 degrees C), high (40 degrees C) temperatures, and time-varying temperature conditions. At the same time, a variety of modern microscopic testing techniques were used to quantitatively characterize the microstructural evolution of limestone powder cement mortar at different temperatures, revealing the degradation process of sulfate attack under different conditions. The results indicate that thaumasite form of sulfate attack occurs at low temperatures, which seriously affects the mechanical properties of the specimens. Under normal temperatures, ettringite-type erosion and a small amount of thaumasite form of sulfate attack occur, and the macroscopic deterioration of the specimens is not significant. At high temperatures, mainly ettringite-type erosion occurs, leading to expansion cracks and peeling materials in block form. Under time-varying temperature conditions, ettringite-type erosion occurs in the early stages, gradually transitioning to thaumasite form of sulfate attack later, with specimens initially exhibiting expansion cracks and gradually becoming muddy as erosion progresses.