Assessment of Resilient Characteristics of Modified Asphalt Concrete

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Saad Issa Sarsam Sara Ali Jasim

Abstract

Asphalt concrete pavement is known to exhibit elastic behavior due to loading at cold weather and a combination of elastic, plastic and viscous behavior at hot climatic condition. However, the quality of the pavement can be assessed by its resilient characteristics (ability to retain its original shape after releasing the load). Distress of the pavement usually starts with micro cracking due to load repetition, while such cracks can heal by themselves in slow process under repeated loading, external or internal heating, and provision of rest period at ambient temperature. The aim of this work is to assess the resilient behavior of asphalt concrete after digestion of asphalt cement with polymer additives (SBS, LDPE, and rubber). Cylindrical Asphalt concrete specimens of 101.6 mm diameter and 127 mm height and beam specimens of 381.0 mm length, 76.2 mm width, and 76.2mm thickness have been prepared with optimum asphalt content requirement and with extra 0.5% asphalt above and below the optimum. Cylindrical specimens were tested under repeated compressive stress, while Beam specimens were tested under repeated flexure stress. The stress level for both testing techniques was 138 kPa at 25°C environment. The loading cycle was 0.1 second load application followed by 0.9 seconds of rest period. The test was conducted for 900 and 660 load repetitions for cylindrical and beam specimens respectively using the Pneumatic repeated load system (RPLS) to allow for the initiation of micro cracks. After the specified loading cycles, Specimens were withdrawn from the test chamber and stored in the oven for 120 minutes at 60 ° C to allow for micro crack healing, then were subjected to another loading and healing cycles. Permanent, total and resilient deformations were detected through LVDT. It was concluded that polymer additives and the micro crack healing cycles have positive impact on resilient modulus and deformation variables of asphalt concrete.

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