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• Wax additives, except MS, improve the workability of bitumen. • Wax additives other than SL harden the bitumen and improve rutting resistance. • The chemical interaction between D wax and bitumen is more pronounced than other wax additives. • The effect of wax-based additives on the thermal behavior of bitumen is negligible. • The effect of wax-based additives on the mechanical properties of bituminous mixtures differs according to the type of aggregate used. Although the use of waxes in bitumen modification is not new, the effect of waxes on bitumen and bituminous mixture performance is still a complex subject of debate. This study was carried out to address this complexity and to comprehensively demonstrate the effect of wax-based additives on bitumen and bituminous mixtures. In this context, the systematic quantitative literature review (SQLR) method, which is more objective than the verbal approach, was adopted, and the results were systematically compared based on the numerical data obtained from the studies in the literature. The effect of waxes on the physical, rheological, chemical, and thermal properties of bitumen and the performance characteristics of bituminous mixtures have been evaluated in detail. [ABSTRACT FROM AUTHOR]

The increased population has accelerated pavement deterioration of and boosted production of residues, generating a constant environmental problem. One of the main problems of pavements is a failure to develop union between bituminous mastic ligand and aggregate. The following study evaluates the use of ash from cellulose incineration as a contribution filler to improve thermal susceptibility of pavements in different climatic zones. The applied methodology for dosage was based on volumetric criteria and state curves. The obtained results showed that reusing this residue in determined conditions (C v /C s  ≤ 1) offers lower wear loss to 35% of temperatures between −10 and 60 °C, due to the C v /C s  = 0.75 ratio that maximizes the cohesive properties of the mixture. Therefore, we showed that this type of industry residue can be reused without complication in zones of certain climatic criteria and that it provides improved properties to the asphalt mix compared to conventional mixes. [ABSTRACT FROM AUTHOR]

• Optimized compositions of mastic were recommended in the cool pavement. • Heat flux was transferred in a different way in the cenospheres and the graphite. • Bruggeman's model can be used to describe the thermal properties of mastic. • Spherical cenospheres contributed less to rutting resistance of mastic. The cool pavement with the function of oriented heat conduction was designed to improve its deformation resistance and decrease the heat island effect. Lots of research had been performed on the thermal properties of asphalt mixture in the cool pavement, but less of them focused on the mastic which played a vital role in the heat conduction. In this study, the normal filler, the cenospheres and the graphite were adopted to prepare the mastic samples. The normal filler was made of the limestone, and the cenospheres were obtained during coal-burning process in coal-fired power plants. The thermal conductivity analyzer was used to investigate the thermal properties of mastic. The scanning electron microscopy was employed to observe the morphological characteristics of different fillers. Dynamic shear rheometer was adopted to evaluate the rheological properties of the mastic as a function of temperature. Bruggeman's model and the finite element method were used to analyze the mechanism of thermal transmission of mastic. Based on the results, the mastic with the ratio of binder:normal filler:cenospheres = 1:0.5:0.5 by weight was recommended to be applied on the top layer of the cool pavement to improve its thermal insulation, and the one with the ratio of binder:graphite = 1:1 was recommended in its sub-layer to improve its thermal transmission and rutting resistance. [ABSTRACT FROM AUTHOR]

• Flame retardants are matched to the decomposition temperature range of each component. • Flame retardants show obvious suppressing action on thermal effects of each component. • Flame retardants suppress the dynamic release of harmful volatiles from components. • Suppressing mechanism of flame retardants on each component combustion is understood. • New formulation is proposed to develop efficient compound flame retardant for bitumen. Bitumen produces a lot of harmful gaseous products and heat at high temperature, endangering human health and ecological environments. To develop an efficient compound flame retardant (FR) for suppressing thermal decomposition and volatile release of bitumen, the suppressing effects of matched halogen-free FR for each bituminous component was first discussed, and then a compositional formulation was proposed to develop a new compound FR for bitumen, suppressing bituminous thermal decomposition and volatile release. Results indicated that the matched FR inhibited endothermic and exothermic reactions, lowered the thermal decomposition rate, and retarded the whole thermal decomposition progress of each component. Also, the dynamic release process of emitted volatiles from each component was suppressed by the selected FR. The release amount of main volatiles was decreased, but CO 2 and H 2 O were still main gaseous products from each bituminous component. Additionally, the superimposed and voidless barrier layer was generated owing to the synergic effects of matched FRs. It suppressed the volatilization and thermal decomposition of flammable volatiles, and hindered the heat transfer and oxygen supply, improving the thermal stability of each component. Added hydroxide FRs showed comprehensive effects of cooling, dilution, adsorption and neutralization, and the generated active oxide facilitated the intumescent layer of expandable graphite to be carbonized. The selected FR played flame retarding and smoke suppressing roles on thermal decomposition of each component. Finally, the compositional formulation of compound FR was proposed to develop a new compound FR for bituminous materials based on the suppression of matched FR on each bituminous component. The developed compound FR efficiently suppressed bituminous thermal decomposition, and lowered the release amount of harmful volatiles and heat when exposed to high temperature. [ABSTRACT FROM AUTHOR]

• Date palm fibers are durable at bituminous mixture manufacturing temperature. • Fiber addition induced a slight bitumen toughness at service life temperature. • Fiber addition led to complex modulus norm increase at service life temperature. • Date palm fibers significantly decreased binder drainage phenomenon of SMA mixture. • Date palm fibers play the role of reinforcement inside the bituminous matrix. This paper investigated the contribution of plant fibers recovered from date palm waste to modify bitumen properties. Palm fibers were characterized to determine their chemical composition, structure, mass loss by heating and tensile strength and the properties of the bitumen-fiber mixtures were evaluated before and after aging using consistency (penetration, Ring and Ball softening point), rheological and thermal tests. The experiments were completed with binder drainage tests on asphalt mixtures to assess the ability for palm fibers to retain bitumen. The results pointed out that the addition of until 6 wt% fibers to neat bitumen conferred a slightly greater consistency, an increase in viscosity by 50% and complex modulus norm by 40% at service life temperatures, before and after aging. These last trends allow to predict the behavior of the asphalt mixtures towards permanent deformations. Thermal analysis on the different mixtures showed that the addition of fibers induced the increase in bitumen crystallinity. The existence of a semi-crystalline fiber network in the bitumen matrix improves the physico-mechanical characteristics of bitumen. The binder drainage tests performed on asphalt mixtures highlighted bitumen absorption by the fibers; this could be correlated to their microstructure and roughness. The results found in this study are encouraging for a potential use of date palm fibers at asphalt mixture scale. [ABSTRACT FROM AUTHOR]

• The graphene addition increased stiffness at high temperature without excessively stiffening at low temperature. • Graphene addition increased recovery but not comparable to that of polymer modified bitumen. • Thermal conductivity of bitumen increased with graphene addition. • Optimum addition of graphene considering rheological improvements is 1.0 to 1.5%. Rutting in bituminous mixture is one of the most studied research problems in pavements. The increased axle loads and higher temperature form favorable condition for rutting. Efforts have been made to improve rutting resistance of bituminous mixtures using various methodologies. However, with ever increasing global temperature due to climate change, bituminous materials should be modified to adapt for such changes over the long run. One of the methodologies includes use of conductive fillers to modify bitumen. In this study, graphene was used as conductive filler for modifying bitumen to investigate the augmentation in rheological and thermal properties. Two viscosity graded bitumen (VG30 and VG40) were modified with 0.5, 1.0, 1.5, and 2.0% of graphene by weight of bitumen. The control and graphene modified bitumen were subjected to softening point test, storage stability test, frequency sweep, multiple stress creep recovery (MSCR) test, and thermal conductivity test. The isochronal curves indicated reduction in loss factor and phase angle, while increase in complex shear modulus in graphene modified bitumen compared to control binder. The difference in rheological properties between control and modified bitumen were found to be higher at higher testing temperatures. Transition from rubbery state to glassy state was observed at high temperature and high frequency loading, where decrease in phase angle and loss factor was seen. The creep-recovery curves showed higher recovery in graphene modified bitumen at different stress levels, while control bitumen depicted negative recovery with increase in stress levels. The isochronal and MSCR test indicated that an optimum level of graphene was between 1.0 and 1.5% by weight of bitumen, which can be attributed to homogeneous dispersion. Thermal conductivity of bitumen increased with the dosage of graphene as higher number of particles will increase the conducting potential. Overall the results indicated graphene addition in bitumen improved rheological and thermal properties with the potential of reducing rutting in mixtures. [ABSTRACT FROM AUTHOR]