The use of CRM-modified asphalt mixtures in Korea: Evaluation of high and ambient temperature performance

The asphalt mixtures modified with crumb rubber modifier (CRM) were evaluated to estimate the deformation resistance at a high service temperature, fatigue resistance and tensile strength at ambient temperatures. As a mean to address the early-life failures of the mixtures observed from a number of pavements in Korea, the study also investigated the moisture susceptibility after freezing-and-thawing (F/T) treatment by indirect tensile strength (ITS) test. A series of CRM-modified asphalt mixtures (CRM mixtures) were prepared by dry process as well as wet process using the CRM contents of 8%, 10% and 12% by weight of total binder, respectively. The test results showed that fatigue resistances of CRM mixtures were significantly improved, compared with the normal mixture (control) without CRM, but the moisture resistance after F/T treatment was found to be very poor. The poor performance of the CRM mixtures in terms of moisture sensitivity appears to explain the early-life failures experienced in Korea. The study then examined the effectiveness of hydrated lime (HL) in improving the concerned performance since the HL is a well-known moisture resistance additive for conventional asphalt mixtures. The test results showed that CRM-mixtures containing the HL had marked improvement in moisture sensitivity.