Aggregate Source Effects on RCC Green Properties

Abstract

Interest in roller-compacted concrete (RCC) pavement has been increasing because of its low initial cost, construction efficiency, and ability to open to traffic early. Current RCC mixture design methods do not directly consider the aggregate source or optimal cement content. An experimental testing plan was developed to batch RCC mixtures with several aggregate sources, gradations, paste contents, and water-cement (w/c) ratios. Each aggregate blend was compacted in order to determine the intergranular volume of voids. The volume of cement paste was varied to underfill, equifill, and overfill the compacted aggregate voids. Green properties (green strength, green modulus, and softening modulus) were measured on the lab compacted specimens to assess the fresh RCC capacity, stability, and plasticity. Green and hardened properties were then related to the RCC mixture volumetric parameters. Green properties were sensitive to aggregate type and gradation, ratio of voids filled by paste, w/c ratio, and total paste content, which all affected the mixes adhesion and shear resistance. In most cases, high cement contents did not improve green or hardened properties. RCC mixtures containing crushed aggregates achieved maximum green strength and stability with underfilled voids, while RCC with rounded aggregates required overfilling the voids. Workability (Vebe time) measurements were not sensitive unless voids were overfilled and not highly sensitive to w/c ratio.