Mechanical properties of concrete containing recycled asphalt pavements

TLDR

Recycled asphalt pavement (RAP) is commonly used in hot‑mix asphalt but its potential as aggregate replacement in Portland cement concrete has been little studied. The present study evaluates the mechanical properties of Portland cement concrete made with real RAP materials. The authors cast 17 concrete mixes in which coarse and fine RAP replaced equal amounts of virgin aggregate, added silica fume and a high‑range water‑reducing agent, and measured compressive and split tensile strengths, modulus of elasticity, and toughness index. Increasing RAP content systematically reduced strengths and elastic modulus while raising toughness, and although the high‑range water‑reducing agent mitigated these losses, silica fume had no beneficial effect.

Abstract

Recycled asphalt pavement (RAP) is the removed and/or reprocessed pavement material containing asphalt and aggregate. The use of RAP in asphalt pavement has become common practice in the construction of new, and reconstruction of old, hot-mix asphalt (HMA) pavements. However, little research has been done to examine the potential of incorporating RAP into Portland cement concrete (PCC) to replace virgin aggregate. In a previous study by the first two of the current authors, laboratory-prepared RAP was used to investigate the potential use of RAP in PCC. The present study focused on the evaluation of mechanical properties of PCC made with real RAP materials through laboratory experiments. Two types of RAP materials (coarse and fine RAP) were used to replace an equal amount of virgin coarse and/or fine aggregate. Silica fume and high-range water-reducing agent (HRWRA) were also added into concrete mixtures to minimise the strength loss resulting from the incorporation of RAP. A total of 17 concrete batches were cast and evaluated for compressive and split tensile strengths, static compressive modulus of elasticity and toughness index. Test results indicated that there was a systematic reduction in the strengths and elastic modulus as well as an increase in the toughness index with the increase in RAP content. While the addition of HRWRA into the matrix improved the mechanical properties of concretes containing RAP, addition of silica fume did not.