Effect of pretreatment on reclaimed asphalt pavement aggregates for minimizing the impact of leachate on cement hydration

Many efforts have been made in recent years to justify the use of reclaimed asphalt pavement (RAP) aggregates in concrete. All previous efforts appear to unanimously report a reduction in concrete performance with varying proportions of RAP usage. The poor performance of RAP aggregates in concrete is attributed mainly to a larger, more porous interfacial transition zone (ITZ) and the cohesive failure of the asphalt. This study hypothesizes that the detrimental impact on the ITZ is attributable to organic compounds leached from the asphalt coating in the high pH pore solution. This study proves the presence of organic compounds in the pore solution and demonstrates that the leachates impair cement hydration. This study also attempted to pretreat the RAP in a sodium hydroxide (NaOH) solution to pre-leach the organic compounds. The pretreatment demonstrated that organic compounds were leached and that NaOH modified the asphalt surface chemistry. However, only a marginal improvement in compressive strength was observed by completing a pretreatment.