Laboratory evaluation of the flexural properties of membrane reinforced asphalt systems

Road pavements are multi-layered structures that should be able to withstand traffic and climatic loading without deforming or cracking excessively. In this sense, bituminous membranes can be successfully used as reinforcement systems in asphalt layers in order to improve road pavement performance against cracking. In particular, composite materials coupling selected membranes with grids and/or fabrics should be able to combine improved tensile properties of grids/fabrics with stress relieving and waterproofing effects of membranes. The present research had the objective of evaluating the effectiveness of asphalt system reinforcement using three membranes, developed to satisfy different needs in pavement construction and rehabilitation. The experimental program allowed the assessment of the flexural properties of reinforced systems in terms of complex modulus and fatigue resistance. To achieve this aim, dynamic four-point bending tests were carried out on double-layered reinforced samples prepared in the laboratory with both plain and polymer modified asphalt mixes. In particular, one tested reinforcing product consisted of an elastomeric membrane characterized by enhanced rheological properties designed to accomplish the function of a Stress Absorbing Membrane Interlayer. The other two reinforcements were obtained by combining membranes with selected fiberglass fabric or grid in order to provide further structural contribution against fatigue. An unreinforced reference system was also investigated for comparison purposes. The experimental results showed a noticeably enhanced fatigue resistance of reinforced systems, particularly in the case of membranes coupled with fabric/grid, even if a reduction in flexural stiffness occurred, mainly due to a lower interface bond strength.