Hot and cold in-place recycling are two of the economical and well-known pavement rehabilitation strategies that can be used to recycle existing pavements. Two main limitations of hot in-place recycling (HIR) are high mixing and compaction temperatures, and a low percentage of using recycling materials in new mixtures. For cold in-place recycling (CIR), damaging the aggregate gradation of milled mixtures and low quality of final mixtures are major restrictions.
In this study, eco-friendly additives to be used for warm in-place recycling technology (WIR) are proposed. To make this mix, two WIR additives were developed to decrease the mixing and compaction temperature while increasing increase the RAP percentage in Warm in-place recycling (WIR) process.
In order to evaluate the products, the mixing and compaction temperatures of mixture were measured and the performance of three different mixture types with three different percentages of RAP were evaluated. The Superpave test was conducted to identify the optimum dosage of two WIR additives and for additive 1 and 2, 3.99% and 7.77% were identified as optimum dosages respectively. To verify this optimum dosage, the second group of Superpave tests were conducted on modified asphalt binder sample and the results had acceptable correlation with first set of rheological tests. The Multiple Stress Creep Recovery (MSCR) and Fourier Transform Infrared (FTIR) Spectroscopy tests were done on modified asphalt binder with WIR additives to better understand the effects of additives on recoverability, rutting resistance and aging mechanism of modified asphalt binder.
The performance properties of mixtures containing 30, 70 and 100 percent RAP material which modified with optimum percentage of two different additives were investigated. Hamburg Wheel Tracking test (HWT) was conducted to evaluate the moisture susceptibility and rutting performance of modified mixture. According to this test results, none of the modified mixtures with additives did not have the moisture susceptibility and rutting problems. Although, additive 2 made the mixture softer than additive 1, but it did not have a significant effect on rutting. Disc-Shaped Compacted Tension (DCT) test was considered to evaluate the fracture properties of mixture at low temperature. Test result showed that additive 2 was more effective in lowering the low-temperature cracking and modified mixtures containing 100% RAP material have acceptable fracture energy.