Workability of Mass Concrete. Report 2. Supplemental Proportioning Parameters.

Abstract : This report presents the results of a research program examining the potential benefits of requiring minimum and maximum mortar contents for 37.5 mm (1-1/2 in.) nominal maximum size aggregate (NMSA) mass concrete and minimum and maximum paste-mortar ratios for 37.5 mm (1-1/2 in.) NMSA mass concrete. The purpose of the research program was to supplement existing guidance on proportioning mass concrete mixtures. Two 37.5 mm (1-1/2-in.) nominal maximum size (NMS) coarse aggregates were used. One was a crushed material consisting primarily of blocky particles. The other was a crushed material having more flat and elongated particles. All mixtures contained natural fine aggregate. The results indicate that a recommended minimum and maximum mortar content could be a useful guide to aid in proportioning workable mass concrete mixtures containing 37.5 mm (1-1/2-in.) NMS coarse aggregate. An approximate minimum and maximum mortar content was identified for mixtures containing favorably shaped coarse aggregate particles (primarily blocky with minimal flat and elongated) and for mixtures containing less favorably shaped coarse aggregate particles (higher percentage of flat and elongated). The paste-mortar ratio appears to be less useful. Recommendations are made to consider supplementing existing guidance on proportioning 37.5-mm (1-1/2-in.) NMSA mass concrete mixtures with minimum and maximum mortar contents.