This study investigates the effects of two waste materials from construction and industry, namely recycled concrete aggregate (RCA) and Type C fly ash, on the overall performance of a special type of pavement surface mixture, porous asphalt mixture. Mixtures of different combinations of RCA (for partial aggregate replacement) and fly ash (for filler replacement) were prepared in the laboratory and tested for a variety of pavement surface performance parameters, including air-void content, permeability, Marshall stability, indirect tensile strength, moisture susceptibility, Cantabro loss, macrotexture, and sound absorption. The analysis of the results showed that incorporating RCA or fly ash in a porous asphalt mixture slightly reduced the air-void content, permeability, and surface macrotexture of the mixture. A 10% replacement of granite aggregates with RCA in the porous asphalt mixtures led to a reduction in mixture stability, indirect tensile strength, resistance to raveling, and sound absorption. The further substitution of mineral filler with fly ash in the mixture, however, helped to offset the negative impact of RCA and brought the mechanical properties of the mixture with 10% RCA to levels comparable to those of the control mixture.

The average content of reclaimed asphalt pavement (RAP) materials in asphalt mixtures for new pavements is around 22% in the current paving practices in the United States. Increasing this content has significant economic and environmental benefits. This study explored the approach of producing asphalt mixtures with 100% RAP materials by adding a small percentage of epoxy asphalt. Specimens of 100% RAP mixtures with low contents of epoxy asphalt were fabricated and evaluated in the laboratory for their properties related to pavement performance, including Marshall stability and flow, indirect tensile strength, resistance to moisture damage, resistance to fatigue damage, and fracture resistance. The results showed that the specimens made of 100% RAP materials selected in this study without a new binder or rejuvenator had low workability and high Marshall stability and indirect tensile strength but poor resistance to moisture damage and fatigue damage. A low percentage (0.5 to 2%) of epoxy asphalt significantly improved the resistance to moisture and fatigue damage of the 100% RAP mixture, and this improvement increased with the epoxy asphalt content. The fracture resistance of the 100% RAP mixture was also significantly improved by a low dosage of epoxy asphalt at a low temperature (8 °C), but the improvement was less significant at a moderate temperature of 25 °C.

In order to improve the sustainability of road pavements, transportation agencies should consider designing pavements with recycled materials such as reclaimed epoxy asphalt pavement. Epoxy asphalt has recently attracted significant attention from the pavement community as a superior-performing binder that can help achieve long-lasting pavements. The recyclability of a proven long-life pavement material, such as epoxy asphalt, has now become one concern in promoting the use of epoxy asphalt binder in road pavements. Due to its thermosetting nature, the usual process of reclaiming asphalt pavement cannot be performed on epoxy asphalt pavement. Recent studies have investigated utilizing reclaimed epoxy asphalt materials in asphalt mixtures as black rock. In light of this, examining the use of reclaimed epoxy materials in cement-concrete mixes is important. The use of reclaimed epoxy asphalt materials in pavement construction is expected to gain more popularity and become a new sustainable construction option in various sustainable pavement applications in the near future. The main objective of this study is to investigate the effects of incorporating 100% reclaimed epoxy asphalt (hereinafter referred to as “epoxy RAP”) and reclaimed diluted epoxy asphalt materials (hereinafter referred to as “diluted epoxy RAP”) into cement-concrete mixes on the performance of the mixtures. The study also examined the effects of replacing cement with 5% silica fume on the performance of reclaimed mixtures. Five different mixtures were fabricated and tested in terms of density, void content, permeability, and compressive strength. Results of the density test revealed that replacing 100% natural aggregates with epoxy RAP and diluted epoxy RAP materials reduced density by an average of 10%. However, void content was found to increase with the incorporation of epoxy RAP, even when replacing Portland cement with silica fume. Regarding permeability, mixtures containing 100% epoxy RAP and diluted epoxy RAP materials have significantly higher permeability values compared with the natural mix value. However, adding 5% silica fume significantly reduced the permeability. Compressive test results indicated that substituting 100% of aggregates with epoxy RAP or diluted epoxy RAP materials would reduce compressive strength by 55% on average. Furthermore, adding silica fume to reclaimed mixes was found to have no apparent effect on compressive strength.

This study investigates the substitution of conventional aggregate with a Florida washed shell in open-graded asphalt mixtures and evaluates the optimal substitution percentage in aggregate gradations of various nominal maximum aggregate sizes (NMASs) (i.e., 4.75, 9.5, and 12.5 mm). Laboratory experiments were performed on open-graded asphalt mixture specimens with the coarse aggregate of sizes between 2.36 and 12.5 mm being replaced by the Florida washed shell at various percentages (0, 15, 30, 45, and 100%). Specimen properties relevant to the performance of open-graded asphalt mixtures in the field were tested, evaluated, and compared. Specifically, a Marshall stability test, Cantabro test, indirect tensile strength test, air void content test, and permeability test were conducted to evaluate the strength, resistance to raveling, cracking resistance, void content, and permeability of open-graded asphalt mixtures. The results show that there is no significant difference in the Marshall stability and indirect tensile strength when the coarse aggregates are replaced with Florida washed shell. This study also found that the optimum percentages of Florida washed shell in open-graded asphalt mixture were 15, 30, and 45% for 12.5, 9.5, and 4.75 mm NMAS gradations, respectively.