Capability of chained interlocking plastic beads in enhancing properties of dense bituminous macadam

Abstract

Typically, Dense Bituminous Macadam (DBM) layers on expressway flexible pavements tend to take up the flexural loading more than the top layers with binder and wearing courses. A lot of road failures associated with DBM are reflected as tensile cracks or typically know as Alligator cracks. In view of this mechanism of failure, a new thinking was foreseen in reinforcing the DBM layer with Chained Interlocking Plastic Beads (CIPB) to enhance the fatigue resistance of the layer. The CIPB in the DBM layer greatly reinforced and improved the interlocking mechanism within the pavement layer. The asphaltic binder with 60-70 penetration grade was used and the gradation for this DBM was selected in accordance with Lembaga Lebuhraya Malaysia (LLM) specification. CIPB of two diamond shaped beads are linked with 0.5 mm to 1.0 mm diameter strands. In this study, different percentages of CIPB were added into the bituminous mixture to determine the percentage of CIPB that would optimize the strength of DBM in term of resilient modulus, stability, and density. Several appropriate tests were conducted to determine the volumetric properties and stiffness modulus of the designed mixtures to determine the Optimum Asphalt Content (OAC). Based on the test results obtained, the CIPB did produce better interlocking mechanism within the mixture and greatly improved the stiffness and stability of the mixture. From this study it was observed that, with an adequate amount of CIPB, the performance of the DBM mixture improved the Marshall stability and resilient modulus. The study shows that the newly developed interlocking mechanism with CIPB has great potential to minimize tensile cracks that migrate to the top through the binder and wearing courses and thus extend the life of the pavement. Such long lasting effect may certainly reduce the road rehabilitation costs. The objectives of this study was to determine the Optimum Chained Interlocking Plastic Beads content in Dense Bituminous Macadam and to evaluate the capability of Chained Interlocking Plastic Beads in enhancing properties of Dense Bituminous Macadam.