Evaluation of the Zycotherm Effect on the Moisture Susceptibility of Warm-Mix Asphalt Containing Crumb rubber

One of the important benefits of using warm-mix asphalt is to reduce the asphalt production temperature, but this is also generating a pavement problem such as a higher moisture potential, due to the lower production temperatures, all moisture in the aggregate does not evaporate, subsequently. The purpose of this study is to evaluate the effect of zycotherm on the moisture susceptibility reduction in warm-mix asphalt. In addition, waste crumb rubber was used as a substitute for fine-aggregates. In total, 9 mixtures were made of 0.1%, 0.15% and 0.2% of zirconium, 10% and 20% of waste crumb rubber, and their combination with bitumen, 70/60 grading and silica aggregate. To evaluate the moisture susceptibility, boiling water tests, indirect tensile test (ITS) and the resilient modulus test were used. Boiling water test results show that the increase in zycotherm improves the moisture susceptibility, but due to the low density of crumb rubber, the crumb rubber hasn’t significant effect on the final result of boiling water test. Based on the results of ITS test and the TSR, a model was generated to predict TSR. According to this model, the minimum required percentage of zycotherm with the replacement of 10% and 20% of crumb rubber, is equal to 0.128% and 0.149%, respectively. According to the experimental results, the addition of a zycotherm increases the Mr, while the substitution of the waste crumb rubber causes a slight increase. Additionally, based on the Mr ratio (RMR), all mixtures have a proper performance against moisture damage.