Portland limestone cement (PLC), also known as Type IL, is a blended hydraulic cement that contains 5–15 percent (by weight) limestone (either blended fines or interground with clinker) to reduce the clinker content.(1) ASTM International (ASTM) C595(2) and American Association of State Highway and Transportation Officials (AASHTO) M 240(3) provide specifications for PLC characteristics. With PLC’s recent adoption and expansion throughout the United States to replace ordinary portland cement (OPC), large-scale production of PLC is now widespread. More than half of the cement consumed in the United States is PLC rather than OPC(4), making PLC the most common type of cement in the United States.(5) While considerable research has been conducted on PLC, much of that work was performed using a few PLCs from different sources, which do not provide insight into the effect of variations in the characteristics of PLC on the performance of the final products, such as concrete mixtures. Considering the variability in performance of PLCs reported in field applications(6), the opportunity now exists for PLC products created at production scale from varying cement plants and with varying limestone contents to be characterized. Cements are typically distributed across State lines to supply projects. Therefore, understanding the range of characteristics and behaviors that different PLC products may exhibit is important to consistent concrete production. This TechNote aims to provide State highway agencies and contractors with information on the variability of PLC throughout the United States. A better understanding of variability in PLCs’ physical and chemical characteristics and its effect on PLC behavior can help enhance PLC performance in the field. This TechNote does not aim to compare PLC with OPC variability or performance and is intended to provide a general perspective on differences in PLC characteristics across the country. The discussion of Type IL cement variability in this document does not, in any way, suggest that there is no variability in Type Ⅰ/Ⅱ cement. Also, the changes in concrete performance resulting from variability in Type IL cement does not mean Type Ⅰ/Ⅱ cement variability does not cause similar changes in concrete performance. Figure 1 displays a graphical abstract of the document.
Hosseini et al. (Mon,) studied this question.