۱- Introduction

۲- Materials and Testing

۳- Testing

۴- Results and discussion

۵- Conclusions

References

Abstract

Recycled Concrete Aggregate (RCA) is considered to be a potential substitute for natural aggregates in asphalt mixtures. Despite some contradictory results achieved by researchers, it is believed that RCA treatment can improve quality of recycled asphalt mixes considerably. In this research, a two-stage treatment was applied on coarse RCA materials in order to improve their properties. The treatment was consisted of first soaking RCAs in Hydrochloric Acid (HCl); second impregnating the treated RCAs into Calcium Metasilicate (CM). The pores of RCAs were filled with CM particles. Substituting virgin aggregates with different amounts of coarse RCA materials into HMA resulted in increased tensile properties of mixes as tested in indirect tensile fatigue test (ITFT). The treatments resulted in reduced moisture sensitivity of mixes. The improvements were mostly attributed to the reduced water absorption of RCA materials. Moreover, morphological characteristics of the treated coarse RCA materials were determined using Scanning Electron Microscopy (SEM) photography.

Introduction

Over the past decades, the growing amounts of Construction and Demolition Waste materials (CDW) have been a great concern for the environmental protection agencies [1]. Unlike the proper actions of recycling these materials and also re-using in different applications, the general trend is to use virgin mineral aggregates for constructing roads and other civil engineering projects. This trend will certainly have adverse effects on the environment [2]. However, lack of adequate landfill areas for damping CDW materials, and the detrimental environmental issues have conducted highway agencies to perform research works so that to find alternative solutions for recycling CDW materials [3]. In fact, road construction projects, that require huge amounts of aggregates are proper sites for using these recycled materials [4]. Production of mineral aggregates in quarries, not only have negative impacts on the environment, but it results in emission of large amounts of CO2 gases during the processing phases [5].