Monitoring of sulphate attack on hardened cement paste studied by synchrotron XRD

• The temporal sulphate transport in cement matrices was analyzed based on SyXRD.
• The concentration dependence of damage mechanisms was discussed.
• Cement matrices containing blends show higher resistance against sulphate attack.

The complex matter of external sulphate attack on cement-based construction materials is still not completely understood. The concentration of sulphate is a crucial factor for the formation of secondary phases and phase transitions of cement hydrates due to sulphate ingress into the microstructure. The sulphate attack on building materials for high and low sulphate concentrations was monitored by laboratory experiments. Hardened cement paste consisting of ordinary Portland cement (CEM I) were exposed to aqueous solutions of sodium sulphate for 18 months. Three sample compositions were used for this research, including different supplementary cementitious materials (SCM). The phase composition was determined for different time spans by high resolution synchrotron X-ray diffraction. Cross sections of exposed cement prisms were investigated as a representation of the microstructural profile. Based on the data, a temporal and spatial determination of the stages of the sulphate attack and the deterioration course was possible. Cement matrices blended with slag showed the highest resistance against sulphate attack.

SYNOPSIS TOC. Cement prisms consisting of ordinary Portland cement partially replaced by supplementary cementitious materials were exposed to solutions of different Na2SO4-concentrations for 18 months. Phase composition was monitored by high resolution synchrotron XRD. Cross sections of the prisms represent microstructural profile. Temporal and spatial determination of deterioration course was possible.Figure optionsDownload as PowerPoint slide