Moisture sensitivity and mechanical performance assessment of warm mix asphalt containing by-product steel slag

Abstract

Warm Mix Asphalt (WMA) has recently become an attractive alternative in pavement engineering due to its potential for significant reduction in energy consumption and carbon footprint of asphalt industry; however, concerns have been raised regarding durability of material and potential to moisture damage due to lower mixing and compaction temperatures. Furthermore, steel slag which is mostly disposed in landfills as waste material could be an appealing option as substitute of natural aggregates for asphalt concrete (AC) production because of its adequate affinity with asphalt binder. The aim of this study is therefore, to assess whether the integration of basic oxygen furnace (BOF) steel slag into Sasobit WMA technology would indicate satisfactory performance in terms of moisture susceptibility. This paper also examines if BOF slag WMA mixture can provide acceptable mechanical performance to be used as a more sustainable approach for pavement construction.To capture short-term moisture damage resistance of BOF slag WMA, specimens prepared with two Sasobit dosages were subjected to two different testing methods. Modified Lottman test and boiling water test using an image analysis technique were performed to compare moisture susceptibility and stripping resistance of BOF slag WMA and HMA (hot mix asphalt) samples with conventional mixtures. Dynamic creep test, Hamburg wheel-track device and resilient modulus test were then conducted on specimens to evaluate mechanical behavior of BOF slag WMA in comparison with BOF slag HMA and another type of WMA mixture prepared with natural aggregates.Findings showed that BOF slag WMA provided significant resistance to short-term moisture damage and therefore, could be considered as durable bituminous mixture when compared to conventional asphalt mixtures. Furthermore, BOF steel slag HMA/WMA exhibited superior mechanical behaviors compared to limestone HMA/WMA mixtures, implying that steel slag could be an effective alternative as pavement material.