Assessing Source-to-Source Variability of Portland Limestone Cement vs. Portland Cement
The rapid adoption of ASTM C595/C595M Type IL portland‑limestone cement (PLC) in the United States has raised concerns regarding potential increases in concrete performance variability compared with traditional ASTM C150 portland cement (PC), particularly for slab‑on‑ground applications. This study evaluates whether source‑to‑source variability of PLC differs from that of PC using large laboratory‑controlled datasets for cement paste, mortar, and concrete representing more than 70 cement sources over a two‑year period. Variability was evaluated for compressive strength, setting time, air content, water demand, and bleeding behavior.

Results show no statistically significant differences in source‑to‑source variability between PC and PLC for strength, setting time, or air content. PLC mixtures exhibited slightly higher average water demand in some cases, driven primarily by differences in cement fineness rather than limestone content. PLCs showed lower average bleeding and greater variability between sources, also strongly linked to fineness. Overall, PLC does not exhibit greater inherent variability than PC, and cement source changes should continue to be managed using established mixture adjustment practices.

Speaker: Justin Dickey, Director of Technical Services, Cemex U.S

Justin Dickey is Director of Technical Services – Ready-Mix Concrete for Cemex USA. He holds a Master of Science in Technology from Texas State University and is a Doctoral student in the Infrastructure Materials Engineering program at the University of Texas at Austin. He was President of the ACI Student Chapter at Texas State University and was a Board Member of the ACI Central Texas Chapter. Justin is an NRMCA Certified Concrete Technologist Level IV and is a member of ASTM Committee C09 – Concrete and Aggregates.