Experimental results of diffusion coefficient of sulfate ions in cement type 10 and class G

Abstract

This paper presents the results of lab experiments done with cement samples in sulfate environment. About 350 samples of cement type 10 and class G were prepared and placed into three temperatures conditions (30, 55, and 75 °C) and three sulfate concentrations (3,000; 6,000; and 30,000 ppmW) for periods of 2, 4, 6, 8, and 10 months. Sulfur concentration (profile) was measured using the scanning electron microscope; SEM. Diffusion coefficient was calculated by matching lab profiles with curves obtained from a Mathlab code created for this purpose. Apart from obtaining the values for diffusion coefficient for sulfate, another main finding was the relationship of sulfate concentration and temperature. At certain threshold temperature, the effects of sulfate diffusion on cement deterioration were more pronounced. The results show that the diffusion coefficient for SO4 was in the order of 3.0×10−12 m2/s to 4.2×10−12 m2/s with small differences in cement type 10 and class G. Also it was noticed that samples exposed at temperature equals to 55 °C, and sulfate concentration equals to 6,000 ppmW had more significant changes when compared to the results obtained from tests conducted at the all other experimental conditions.