Chloride and combined chemical attack of saline solutions on modified oil well cement pastes.

The effect of complex geothermal water composition in comparison with that of a single NaCl solution was studied on cement pastes prepared by partial substitution of cement with silica fume and metakaolin in different proportions. After 90 days of hydration in solutions or water, TGA, XRD, FTIR, ion chromatography, SEM, volume change, and compressive strength (CS) measurements were used to evaluate the impact of solutions on the systems. Higher Al³⁺ content in blended samples resulted in a greater ability to bind chlorides in Cl–AFm. A lower amount of free Cl⁻ restrained delayed ettringite formation. Less significant volume changes together with the formation of C–(A–)S–H phases promoted by both solutions led to lower porosities and higher CSs than those of referential paste. NaCl solution showed a bigger negative influence than the geothermal one.