The behaviour of different cement pastes in various sulphate solutions

Abstract

<span style="font-size:11.0pt;line-height:115%; font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;mso-fareast-font-family:="" "times="" new="" roman";mso-fareast-theme-font:minor-fareast;mso-hansi-theme-font:="" minor-latin;mso-bidi-font-family:arial;mso-ansi-language:en-us;mso-fareast-language:="" en-us;mso-bidi-language:ar-sa"="">Ordinary portland, sulphate resisting and pozzolanic cement (made from 80% portland cement and fired clay) pastes were immersed in 5% solution of (NH₄)₂SO₄, MgSO₄ and Na₂SO₄ up to one year. The sulphate attack was followed by determining the compressive strength of the hardened pastes, the amount of penetrated sulphate and free lime. The penetrated sulphate content and its relation with lime as well as the resulting <i style="mso-bidi-font-style: normal">p</i>H and hydration products have a deleterious effect on the stability of CSH and hence the strength of the hardened pastes. (NH₄)₂SO₄ has the highest aggressive action on cement pastes whereas pozzolanic cement pastes show the highest resistivity to sulphate attack.</span>