Pozzolanic reaction and strength activity index of dolomite powder incorporated cement mortar

Abstract

Assessment of pozzolanic activity of an alternative material is a key parameter for its application as a cementitious material. This study has been conducted to check the scope of dolomite powder in its native and calcined state as a substitute for cement for sustainable construction practices. Dolomite is a variety of limestone consisting of calcium carbonate and magnesium carbonate in predominant compositions. The chemical composition of dolomite powder is determined using X-ray florescence (XRF) technique. XRF test results showed the presence of 31.08 % of Calcium Oxide and 21.3 % of Magnesium Oxide as major compounds in dolomite powder. Frattini and Strength Activity Index (SAI) tests have been conducted to analyze the pozzolanic activity of dolomite powder. Frattini test determines the consumptions of hydroxyl ion (OH–) and calcium ion (Ca+2), which are plotted in the solubility curve to decide the pozzolanic behavior of a material. The test on dolomite powder in its native state resulted in no pozzolanic activity, while in the calcined form, pozzolanic activity was observed. This behaviour was due to the activation of quick lime after the calcination process. The strength Activity Index (SAI) test is conducted to compare the compressive strength of nominal and modified mixes at 7 and 28 days. The dolomite powder in its native state satisfied the Strength Activity Index (SAI) criteria at 7 and 28 days owing to its ultra-fine particle size. The SAI test observations were on the higher side in the calcined state as both – ultra-fine particle size and quick lime contributed to the strength of the mix.