Portland cement paste performance when inert limestone filler is added as clinker replacement

Marginal information is available in the literature regarding the performance of Portland cement–based pastes when reducing clinker content with inert limestone fillers (ILSF) when the replacement is > 15%. In this research, six different blended Portland cements (BPCs) from two different brands were evaluated, all with loss of ignition (LOI) values ranging between 2% and 18%, estimating ILSF contents between 5% and 35%. The characterization of these BPCs was conducted through laboratory tests aimed at performance forecasting in the absence of their component proportions due to trademark secrecy. These tests included determining BPCs' fineness (or Blaine number, F), density (ρ), and LOI. Then, paste characterization was performed, including water content for paste normal consistency, initial and final setting times, determination of the luminosity coordinate *L from hardened paste specimens, and mortar compressive strength at 28 days. It was concluded that one way to overcome the misinformation about the composition of BPCs (clinker, pozzolans, or ILSF contents) is to obtain the LOI parameter, as it will help forecast the performance of new BPC formulations.