Preparation and Performance of Sulfate Resistance Cement-Based Material

Abstract

To discuss prevention of sulfate attack, especially thaumasite form of sulfate attack (TSA), sulfate resistance cement based material (SRM) were designed and prepared, and properties of which were investigated systematically. Micro-analytical techniques were introduced to identify erosion substances especially thaumasite, namely Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM) equipped with X-ray energy dispersive spectrometer(EDS). Results show that SRM have better sulfate resistance, as well as TSA resistance, when exposed to aggressive environment with 33800 ppm mass concentration of SO42- in magnesium sulfate solution at 5°C±2°C. When immersed in magnesium sulfate solution for 40 weeks, compressive strength and tensile strength of SRM are still higher than their initial, and those of control specimen are lower by 33.7%, 36.5% compared to its initial. Surface erosion substances of SRM named S1 are ettringite and gypsum, while those of control specimen are ettringite, gypsum, thaumasite and brucite.

Minerals in cement chemistry: A single-crystal neutron diffraction study of ettringite, Ca6Al2(SO4)3(OH)12·27H2O

“…The 3 main cement hydration products, i.e., calcium silicate or aluminate hydrates (the socalled C-S-H and C-A-H) and calcium hydroxide (portlandite Ca(OH)2), are decomposed as a result of both sulphate attack and carbonation: as C-S-H and C-A-H provide most of the binding strength, the formation of ettringite and thaumasite leads to weakening and disintegration of the cement matrix. This phenomenon is more pronounced in cement structures below ground (e.g., Hartshorn et al 1999;Bensted 1999;Hobbs and Taylor 2000;Santhanam et al 2001;Zhang et al 2009;Gatta et al 2012). The effect of carbonate ions on delayed ettringite formation was recently reported by Asamoto et al (2017).…”