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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]

The influence of rice husk ash (RHA) as an alternative active filler on the mechanical properties of bitumen emulsion-based recycled asphalt specimens in high- and low-temperature domains was investigated. The experimental methodology was comprised of static indirect tensile and wheel-tracking testing, as well as scanning electron microscopy using secondary electrons and energy dispersive X-ray spectroscopy. The results showed that the increase in the mass fraction of RHA gradually improved the water sensitivity and the high-temperature performance of specimens, but also negatively affected their low-temperature performance. The mass fraction of RHA above 1.5%, resulted in a tensile strength ratio after freeze–thaw and immersion of more than 80%, and in the dynamic stability in rutting test above 4500 mm−1, but also the low-temperature indirect tensile strength below 2.0 MPa. Considering the relevant regulations, the mass fraction of RHA should be in the range of 1–1.5%. [ABSTRACT FROM AUTHOR]

In recent years, nanoparticles have been introduced into warm-mix-modified asphalt to improve asphalt performance after sustaining ultraviolet (UV) aging, yet the evaluation of aging performance is often a descriptive characterization of rheological properties. This study extends rheological characterization with viscoelastic mechanical modeling to evaluate resistance to UV aging using Sasobit and SBS compound-modified binder blended with nano-titanium dioxide (TiO2). The extended method comprises characterizations using several rheological properties and a viscoelastic mechanical model, named the 2S2P1D model, on modified asphalt after 3 days, 6 days and 9 days of ultraviolet (UV) aging. The rheological properties of the UV-aged binders were tested at high and medium temperatures in terms of viscosity, complex modulus, phase angle and fatigue factor. Rheological test results showed that nanoparticles generally had no apparent effect on the complex modulus of aged binders regardless of UV aging times. However, the aged binder with nanoparticles showed better fatigue resistance than aged binders without nanoparticles after 3 days of UV aging. As an extension, the black space diagram and 2S2P1D model were used to investigate the viscoelastic properties of these aged binders. The k and h values, as important model parameters, were almost the same and less than one for all UV-aged binders. All investigated aged asphalt binders showed characteristics of a viscoelastic solid in terms of the master curves of the complex modulus and phase angle, and the master curves of the phase angle for all UV-aged binders did not meet the time–temperature equivalence. Moreover, these observations from the 2S2P1D model revealed that aging durations did not affect the viscoelastic mechanical characteristics of warm mix asphalt in this study. The method adopted in this study may promote a comprehensive evaluation of asphalt properties after UV aging, especially considering the viscoelastic mechanical performance. [ABSTRACT FROM AUTHOR]

In order to further explore the performance of mixture with waste tire rubber (WTR) and amorphous poly alpha olefin (APAO) modified asphalt, the 12%WTR+4%APAO and 15%WTR+4%APAO modified asphalt mixtures were selected as research objectives. The asphalt mixtures with matrix asphalt, WTR modified asphalt, and SBS modified asphalt were prepared for comparative analysis. Through the mixture design, the optimum asphalt-aggregate ratio of five asphalt mixtures was determined respectively. The volumetric parameters and resilient modulus were studied. The laboratory performances were studied by standard Marshall stability test, wheel tracking test, immersion Marshall test, freeze–thaw splitting test, indirect tensile strength test, indirect tensile fatigue test, and Marshall stability after long-term aging test. Compared with the other three asphalt mixtures, the results showed that the 12% WTR+4%APAO modified asphalt mixture had the highest Marshall stability and high-temperature performance. While the 15% WTR+4%APAO modified asphalt mixture had better permanent deformation resistance at high temperatures, moisture stability, aging resistance, and relatively good fatigue performance. The statistical hypothesis test results also confirmed that WTR/APAO modified asphalt has a significant effect on mechanical properties. Based on the results of various performance, the 15% WTR+4% APAO was the optimal content for asphalt mixture. [ABSTRACT FROM AUTHOR]