EFFECTS OF AGGREGATE BLENDS ON THE PROPERTIES OF PORTLAND CEMENT CONCRETE PAVEMENTS. INTERIM REPORT

Although recent studies have shown that pavement performance does vary by aggregate type, current portland cement concrete pavement design tools do not fully incorporate aggregate properties into the design process. Aggregate characteristics shown to affect pavement performance include strength, thermal properties, and shrinkage properties. The objective of this study was to investigate the material properties of crushed limestone and siliceous river gravel, two aggregates predominantly used in current pavement construction, and to determine a relationship between the properties of single-aggregate concrete and concrete made with predetermined blends of limestone and gravel. This report continues the work of Project 422/1244, which way limited to single-aggregate concretes. Additional models were developed to predict concrete properties of blended aggregate concrete for use in the design tools, CRCP and JRCP, described in previous 422/1244 reports. A computer program, CHEM2, was developed, which allows the pavement designer to estimate the material properties of concrete from an inexpensive chemical test. CHEM2 also predicts the properties of blended aggregates so that the user can determine the necessary blending ratio to control such troublesome properties as thermal coefficient of expansion and drying shrinkage.