Replacing fly ash with limestone dust in hybrid cements

This study explored the effect of adding 10% of finely ground limestone dust to alkaline hybrid cements. A series of binders was prepared with 20-30% OPC (CEM I 52.5R) and fly ash in the presence or absence of a chemical activator (5% Na2SO4). The rate of heat release was determined by isothermal conduction calorimetry. Setting times and 3 d, 28 d and 90 d compressive strength were likewise found. The reaction products were characterised by XRD, DTA/TG and BSEM/EDX. The inclusion of 10% of limestone in the hybrid cements to replace the fly ash improved compressive strength and hastened hydration. The 28 d pastes containing 30% OPC, 10% limestone, 55% FA and 5% Na2SO4 developed compressive strength above 45 MPa. (C) 2020 Elsevier Ltd. All rights reserved.