Comparisons of Natural and Enhanced Asphalt Mixtures Containing Recycled Cement-Stabilized Macadam as Aggregates

Abstract

The recycling of cement-stabilized macadam (CSM) is beneficial from the effective utilization of resources and the viewpoint of environmental preservation. For the effective utilization of CSM, it is useful to use CSM as recycled aggregates for hot-mix asphalt (HMA) productions as aggregates. In order to make this technology feasible, mixture design, chemical and physical properties, and durability of recycled aggregate hot-mix asphalt (RAHMA) should be engaged in the processing of demolished CSM. The objective of this study is to develop one RAHMA by recycling the base layer of semirigid pavements, and to assess the performance of natural and methanesiliconic acid sodium salt solution (MASS) enhanced RAHMA. Initial laboratory results find that the MASS treatments were beneficial to the performance of RAHMA; however, moisture resistance was found to be unsatisfactory. To improve moisture resistance, cement and hydrated lime fillers were applied in this study. The combined 1.75% by weight cement/ hydrated lime (1:1) was found to perform the best of the cases utilizing improved moisture resistance of RAHMA. Also, all of the residue Marshall stability ratio (MS0) and the splitting tensile strength ratio (TSR) were found to meet specifications. However, although the unaging and short-term aging performance of RAHMA were successful, all of the moisture resistance indicators of long-term aged RAHMA fell below standard rirements. Therefore, the long-term performance of the proposed RAHMA rires further improvement and study. While the particular use for RAHMA needs improvement concerning moisture durability, the enhancement methods mentioned in this study should be considered in the application of recycling CSM in hot-mix asphalt productions.