Title:
Assessment of Chemical Durability of Pitchstone Fines in Portland Cement Blended Mortars
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Publication:
CIA
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Date:
2/14/2011
Abstract:
The use of supplementary cementitious materials (SCMs) as partial replacement of Portland cement (PC) is an effective way of reducing the consumption of PC. This investigation is aimed at assessing some chemical durability aspects of PC-SCM blended mortars containing pitchstone fines (PF) and fly ash (FA) at 20% and 40% replacement levels of PC. Hardened mortar cubes containing these two pozzolanic SCMs and a control mortar containing 100% PC were prepared and pre-aged in lime-saturated water for 28-days. These specimens were then immersed into 1M solution of sodium sulphate (Na2SO4) and their mass and pH recorded after 28-days and 56- days. Specimens were also immersed in deionised water as a control environment for comparison of mass change and pH. In the case of PF, data from 1M Na2SO4 immersion demonstrate increasing substitution rate provides lower mass gain. In contrast, increasing replacement rate of PC by FA in 1M Na2SO4 demonstrates higher mass gain comparable to 100% PC.