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The mechanical and thermal properties of roller compacted concrete pavement (RCCP) are considerably influenced by its aggregate. This study determined the optimum value of lightweight expanded clay aggregate (LECA) incorporation into the RCCP through the response surface methodology (RSM) with mechanical and thermal properties evaluation. LECA was replaced as coarse aggregate in different percentages of 25, 50, 75, and 100% (by volume) to develop lightweight and high-insulation capacity RCCP, which could be appropriate for cold climatic zones. Two different mixtures of RCCP with normal-weight aggregate comprising 12% and 15% cement were used as control mixtures. The results showed that incorporating LECA at any percentage in RCCP produced more workable concrete. The substitution of LECA in 25–100% decreased the density of RCCPs containing 12% and 15% cement about 8–24% and 7–23%, respectively, while the water absorption increased around 4–77% and 8–72%. The thermal conductivity of RCCPs decreased by increasing the LECA replacement as coarse aggregate. Also, the LECA replacement increment in RCCPs resulted in lower heat capacity values. Overall, it can be concluded that incorporating LECA in RCCP by around 37% as coarse aggregate would satisfy the standards in terms of fresh, mechanical, and thermal properties. [ABSTRACT FROM AUTHOR]

This paper aims to explore the performance and economy of asphalt mixture with waste tire rubber (WTR)/ethylene-vinyl acetate (EVA) compound-modified asphalt. In this paper, five kinds of WTR/EVA asphalt mixture were selected as research targets, 70# base asphalt mixture and 5% styrene–butadiene–styrene (SBS) asphalt mixture were compared. Laboratory test results showed that WTR and EVA could significantly improve the performance of the asphalt mixture. The rutting resistance and anti-ageing ability of 15%WTR + 4%EVA asphalt mixture were superior to the 5% SBS asphalt mixture, and the anti-cracking ability and water stability were extremely close between them. Furthermore, the analysis of variance results revealed that WTR and EVA had a significant effect on asphalt mixture performance, the effect of EVA was more obvious than WTR. According to the economy analysis, the application of WTR/EVA-modified asphalt could significantly reduce construction costs, the material cost of 15%WTR + 4%EVA asphalt mixture was about 9.3% lower than 5% SBS asphalt mixture. As summarised above, WTR/EVA compound-modified asphalt mixture was an economical and environmentally pavement construction material due to its superior performance and lower cost, and 15%WTR + 4%EVA was the optimal combination dosage for asphalt mixture. [ABSTRACT FROM AUTHOR]

In this research, nano- TiO2 and graphene composite were added to asphalt to enhance the performance of asphalt by synergistically improving the dispersion of each other. The physical properties of the modified asphalt were assessed using penetration, softening point, and ductility tests, and the rheological performance of the asphalt was studied using dynamic shear rheometric (DSR) and bending beam rheometric (BBR) tests. In addition, scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy, and nanoparticle size analyzer (DLS) were used for microscopic analysis of asphalt. The results demonstrated that the incorporation of nano- TiO2 and graphene in asphalt could improve the high-temperature properties and the aging resistance of base asphalt. In terms of low temperature performance, the composite of nano- TiO2 with graphene improves the negative effects of the single addition of nano- TiO2 or graphene. Microscopic analysis indicated that the dispersion of the nano- TiO2 and graphene in the asphalt synergistically was improved significantly. The optimum amount of 1% nano- TiO2 and 0.04% graphene is recommended for the composite. This study provides a basis for the diversified application and development of nanomaterial modified asphalt in the future. [ABSTRACT FROM AUTHOR]

High silicon dioxide content enables as a cement substitute. This study explored recycling RHA and RAP in cement stabilised macadam (CSM) to produce a pavement base material. Laboratory experiments covering strength, flexibility, shrinkage, and resistance to temperature variation were conducted on CSM with RAP (40% by weight of natural aggregates) and RHA at 0%, 20%, 40%, 60%, and 80% weight of cement. The results indicated that the compressive strength, resilient modulus, and tensile strength of CSM increased with curing time while the increasing rate and strength after curing decreased with the addition of RHA. The resistance to thermal changes, moisture loss, and the freeze-thaw cycle could be maintained by replacing 20 wt.% (or lower content) cement with RHA. These findings suggest that replacing 20 wt.% of cement with RHA and 40 wt.% of natural aggregates with RAP can generate qualified and environmental pavement base material. [ABSTRACT FROM AUTHOR]