Coarse Aggregate and Self-Consolidating Concrete Passing Ability

This paper examines the effect of aggregate content and gradation on self consolidating concrete (SCC) passing ability. Passing ability is defined as an SCC mixture’s ability to flow through narrow spaces without segregating or blocking. The mixtures tested ranged over two uniform aggregate sizes, two aggregate contents, two different mixture design philosophies, and a gradated aggregate mixture. Passing ability tests, slump flow tests, horizontal flow tests, and stereology tests were performed on these mixtures. Stereology is a statistical counting technique used primarily by natural scientists and concrete researchers have used sterolog to describe bubble size and distribution in concrete. A vertical flow box was developed by McBride to determine the passing ability of the various mixtures. Various bar spacings are tested. From the results of this study, it seems that two stereology parameters can be correlated to the minimum bar spacing that will allow SCC to pass. These parameters are the ratio of maximum aggregate size to mean aggregate free distance and the ratio of maximum aggregate size to mean aggregate random spacing.