Published: Jan 1992
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Aggregate quality has a central role in the performance of hot mix asphalt concrete (HMAC) mixtures. The availability of good quality aggregates is of concern in many countries including the U.S.A. One of the solutions to the aggregate depletion problem is to upgrade and improve the properties of the available abundance of marginal aggregates. This paper introduces a new aggregate upgrading technique for the use in HMAC mixtures. The proposed technique is referred to as “Cement Coating Technique” (CCT). The CCT addresses the surface texture of aggregate particles and improves the bond between the particle surface and the asphalt binder. The concept of the CCT is based on shielding the surface of the aggregate particles by a hydrated Portland cement film. The new cement coated aggregates can then be used in asphalt mixtures following the usual mix procedures. Asphalt concrete mixes made with cement coated aggregates are referred to as “CEMPHALT” mixtures. Cement content, water cement ratio and hydration time were found to be the three main parameters influencing the coating process. The optimum values of these parameters were determined. Performanceevaluation of CEMPHALT mixtures indicated significant improvements achieved in permanent deformation, fatigue and moisture damage resistance.
aggregates, asphalt, cement, upgrading, coating, pavement, rutting, fatigue, moisture damage, low quality aggregates
Associate Professor, University of Idaho, Moscow, ID