Monitoring Micro Crack Healing Phenomena in Recycled Asphalt Concrete

Abstract

Asphalt concrete usually practices cracking and distress during its service life. However, recycling process as well as crack healing phenomena can enhance the physical properties and extend the pavement service life. This investigation is concerned with monitoring the microcrack healing of recycled asphalt concrete through its influence on deformation measurement under three testing techniques, repeated (compressive, tensile and shear stresses). Reclaimed asphalt concrete mixture was recycled with [carbon black-asphalt] and [Styrene Butadiene Rubber (SBR)-asphalt] rejuvenators. Specimens have been tested with the aid of the pneumatic repeated load system (PRLS). The repeated loading of the three testing techniques was terminated after 1000 load repetitions, and the specimens could heal by external heating at 60°C for 120 minutes. Specimens were returned to the (PRLS) and subjected to another run of repeated stresses application after healing. It was concluded that the deformation increases after recycling process while it declines after microcrack healing regardless of the testing technique adopted. The deformation declines by (31.8, 5.8 and 19)%, (43 ,49 and 24 )% and (44 ,10 and 13 )% under three level of repeated compressive stresses of (0.068, 0.138, and 0.206) MPa at (40 °C) after healing cycle for reclaimed and recycled mixture with (carbon black-asphalt) and (SBR-asphalt) respectively when compared with permanent deformation before the healing cycle. The permanent deformation under repeated punching shear and indirect tensile stresses declines after microcrack healing by (32, 26 and 25.7) % and (73, 78.7 and 78.2) % for reclaimed, recycled with (carbon black-asphalt) and recycled with (SBR-asphalt) mixtures respectively.