Effects of maximum aggregate grain size and gradation on roller compacted concrete pavements

Roller compacted concrete (RCC) pavements, which stand out as an alternative to conventional concrete and asphalt pavements, are increasingly preferred because of their high strength, fast construction, and low cost advantages. The properties of aggregates directly affect the performance in roller compacted concrete mixtures. In particular, the maximum aggregate particle size (Dmax) and gradation play a determining influence on the mixture's density, compressibility, and mechanical strength. This study aimed to investigate the effects of maximum aggregate particle size and gradation on the mechanical performance of roller compacted concrete pavement mixtures. Within this scope, roller compacted concrete pavement mixtures were produced using three Dmax (12.5, 19, and 25 mm) and three different cement dosages (300, 350, and 400 kg). Tests for physical properties on mixtures were conducted using unit weight and ultrasonic pulse velocity (UPV) tests, while tests for mechanical properties were conducted using compressive strength, flexural strength, and splitting tensile strength tests. Increasing the Dmax to 25 mm significantly improved the compressive and flexural strength of the mixtures. However, the splitting tensile strength increased up to 19 mm and showed a slight decrease when reaching 25 mm. The increase in cement content consistently improved all mechanical properties. Overall, the use of well-graded coarse aggregates with Dmax in the range of 19–25 mm was found to improve the mechanical properties and compressibility of roller compacted concrete mixtures.