Proportioning manufactured sand in flowable concrete

Abstract

Manufactured sand has started to be used in concrete due to its availability and low cost. However, it has different shape properties, gradations, and mineralogy in comparison to the natural sand, and these differences can impact the performance of the concrete. This work quantifies the shape properties of manufactured sands and natural sands using sophisticated tests such as the AIMS II and more practical lab tests such as the Uncompacted Voids Content (ASTM C1257 -Method A). A correlation between these two measurements is presented. Next, concrete mixtures are proportioned with different amounts and gradations of manufactured sand at a variety of paste volumes, and their influence on the concrete workability is measured. Adjustments are also made to the Tarantula Curve Mixture Design tool to accommodate the different characteristics of manufactured sands in a concrete mixture for flowable concrete that must be finished. Further, this work investigates the impacts of manufactured sand on the pumping pressures. The workability and pumping pressure for three different manufactured sand sources and one natural sand are compared. Recommendations are made for the usage of manufactured sand in pumpable concrete mixtures. Also, the fine sand content and the combined uncompacted voids content of blended fine aggregates (natural sand and manufactured sand) are shown to be significant for concrete pumpability. Further, suggested changes are made to the fine sand content minimum limit on the Tarantula Curve to be 27% to keep pumping pressures manageable.