Performance of Portland Limestone Cements

Portland limestone cements (PLCs) have recently been approved as a part of the ASTM C595/AASHTO M240 specifications. These cements are designed to enable more sustainable concrete production by replacing up to 15% of the clinker with interground limestone particles. The PLCs represent a potential method to reduce the carbon dioxide embodied in built infrastructure and extend the life of limestone quarries. This paper presents a comparison of the performance of three commercially available PLCs meeting the ASTM C595/AASHTO M240 specifications and three ordinary portland cements (OPCs) made from the same cement clinkers. An additional OPC was blended with limestone that had two mean particle sizes. One OPC and PLC were used with a Class C fly ash. Each of these cementitious systems was used to produce typical concrete paving mixtures with the performance of these materials being quantified through a series of standardized tests. The results of the study show that the mechanical properties of PLCs have negligible changes as they relate to design practices and implementation. The early-age volume changes of a PLC ground to levels consistent with achieving similar 28-day strengths were shown to be similar to that of the corresponding OPC, whereas PLCs that were ground significantly finer might lead to increased early-age shrinkage. The transport properties show behavior that is +/- 30% of the conventional OPC, whereas the results for PLC systems containing fly ash show a synergistic effect with improved performance. The overall results of this study show that PLCs conforming to ASTM C595/AASHTO M240 could achieve similar performance as the OPC they would replace.