Incorporating 3D image analysis and response surface method to evaluate the effects of moisture damage on reinforced asphalt mixtures using glass and polypropylene fibers

Abstract

• Incorporation of up to a certain amount of combined fibers can beneficially enhance load bearing capacity and reduce the proportion of broken aggregate. • Fibers can increase the total fracture energy (particularly post-peak G f ) and consequently reduce the fragility index by obstructing crack propagation. • Integration of fibers can improve mixtures' moisture susceptibility and reduce the negative effects of moisture damage. • The destructive impact of an increase in temperature is more dominant compared to the number of freeze and thaw cycles. • The combination of the response surface method and image analysis techniques exhibited a great capability to detect and quantify adhesion and cohesion failures. This paper evaluates the performance of fiber-reinforced mixtures subjected to moisture damage. Response Surface Method was used to design an experimental matrix based on the central composite design. The amounts of fibers, number of freeze and thaw cycles, and testing temperatures were considered as factors, while maximum load, stiffness, indirect tensile strength, CT index , fragility index, broken aggregate, and adhesion failure were regarded as the responses. Indirect tensile strength test and 3D image analysis were conducted to characterize mixtures’ fracture properties and moisture susceptibility, respectively. The results show that temperature exhibits the highest influence on mixtures’ mechanical properties as well as adhesion and cohesion failures. An increase in the number of freeze and thaw cycles deteriorated the mixtures’ performance. Although higher beneficial impacts of glass fiber were reported earlier, this study proved that the performance of the mixtures prepared with combined fibers is comparable with the previous study. This finding brings forth the advantage in cost reduction of reinforced mixtures production due to the replacement of part of the glass fiber with polypropylene fiber. In addition, it was found that a combination of utilized fibers up to approximately 0.2% by weight of aggregates exhibited beneficial impacts on load bearing capacity, indirect tensile strength, and proportion of broken aggregate while exceeding this amount was not favorable which was correlated to the jeopardizing of cohesion level between mixtures constituents. Moreover, it was observed that fibers slightly reduced the fragility index by obstructing crack propagation. It was finally concluded that a higher amount of fibers enhanced mixtures' moisture resistance and diminish the negative effects of freeze and thaw cycles.