QUANTITATIVE-DETERMINATION OF CALCIUM HYDROXIDE IN THE PRESENCE OF CALCIUM SILICATE HYDRATES - COMPARISON BETWEEN CHEMICAL-EXTRACTION AND THERMAL-ANALYSIS

Methods most usually employed in calcium hydroxide determination are solvent extraction, followed by chemical titration, and thermal analysis. A comparison between chemical analysis based upon Franke method and thermal analysis shows that the latter gives results systematically lower than the former. However, the order of magnitude of the differences is too large to be explained by the hypothesis of an extraction of part of the lime bounded in calcium silicate hydrates (CSH) phases. This suggests that the difference between chemical and thermal methods may be ascribed to a partial reaction of calcium hydroxide with CSH during the heating of the sample in a temperature range preceding the thermal decomposition of Ca(OH)//2. The aim of the work reported in this paper is to verify such hypotheses. Study materials, methods and results are discussed.