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Volatile organic compound (VOC) emissions are becoming an increasingly significant issue because of the increasing demand for bitumen in road engineering. This study attempted to develop a type of fume-suppressed bitumen with good comprehensive performance. Initially, 1, 2, and 3% organic montmorillonite and 2, 3, and 4% waxy warm-mix agents were utilised to modify bitumen. Subsequently, the fume suppression and physical and construction performances of the modified bitumen were evaluated, and the modified bitumen with the best comprehensive performance was determined. On this basis, constant- and variable-temperature heating modes were designed to verify the fuel suppression performance of the modified bitumen thoroughly. Finally, the modification mechanism of modified bitumen was investigated via atomic force microscopy. The results indicate that the modifier had the greatest impact on the ductility of the modified bitumen in terms of its physical performance. Although waxy warm mixed agents increase VOC emissions, organic montmorillonite can inhibit this effect. The modified bitumen, composed of 2% organic montmorillonite and 2% waxy warm mix agent, has the best comprehensive performance, with a 40.6% emission reduction rate under constant temperature heating mode and 46.4–28% range from 200 ℃ to 120 ℃ under another mode. The waxy warm mix agents and organic montmorillonite-modified bitumen developed into continuous and dispersed phase systems, respectively, leading to variations in the modified bitumen's physical performance and VOC emission capacity. In contrast, the composite-modified bitumen exhibited a two-phase structure with the surface morphology of an 'egg tray'. This unique structure enhances the heating surface area and facilitates heat conduction, improving the bitumen performance during construction. [Display omitted] • Consideration was given to the VOC emission reduction effect caused by the decrease in viscosity of bitumen. • The efficacy of fume suppression asphalt was verified in two heating modes. • A fume suppression asphalt with commendable comprehensive performance was designed. [ABSTRACT FROM AUTHOR]

• The leaching-deterioration properties and leaching mechanism of cement mortar under wet-dry cycles were studied. • Reducing the water–cement ratio and and the addition of silica fume are conducive to mortar resistance to calcium corrosion under wet-dry cycles. • The shortening of the dry-wet cycle and the increase of soaking solution concentration aggravate the calcium dissolution of cement mortar. The dry–wet cycle in cement mortar is essential for accelerating ion transport; however, it results in an increase in severity of durability damage. Leaching damage is a primary-contributing factor that reduces durability. Studies on calcium corrosion degradation of cement-based materials and its inhibition process during dry–wet cycles are lacking. In this work, the frequency of dry–wet cycles, concentration of soaking liquid, reduction of water–cement ratio, and incorporation of silica fume on the corrosion deterioration of cement mortar were studied. Using NH 4 Cl solution as the corrosion medium, the variation in leaching depth, calcium-ion dissolution, compressive strength, flexural strength, phase composition, and microstructure was analyzed. The results showed that calcium dissolution occurs during dry–wet cycles, hence the mechanical properties of the cement mortar declines, and pore expansion occurs. With the shortening of the dry–wet cycles, leaching damage increased and the dissolution rate gradually deviated from Fick's law. Increasing the concentration of NH 4 Cl solution significantly increased the leaching depth of mortar and accelerated the reduction of the compressive flexural strength. Reducing the water–cement ratio or adding a proper amount of silica fume effectively inhibited the dissolution rate of cement mortar and the deterioration of compressive strength and flexural strength. The results of this study provide a new insight and deeper understanding of the leaching-degradation properties and mechanisms of cement-based materials during dry–wet cycles. Furthermore, the results may be used for the inhibition of cement-based material dissolution during dry–wet cycles. [ABSTRACT FROM AUTHOR]

[Display omitted] • The aging behavior of PPA/SBS modified bio-mixed asphalt was analyzed. • The effect of aging on chemical composition of PPA/SBS modified asphalt was investigated. • The PPA/SBS modified bio-mixed asphalt has batter elastic response. • The bio-asphalt has a certain positive effect on aging behaviour. This study investigates the performance of polyphosphoric acid/styrene–butadienestyrene (PPA/SBS)-modified bio-mixed asphalt after thermo-oxidative and ultraviolet (UV) aging, based on its high-temperature rheological properties and microscopic characteristics. The temperature sweep test results revealed that long-term thermo-oxidative aging significantly increased the dynamic shear moduli of the composite-modified asphalts, where the maximum increment in composite-modified asphalts reached to 425 %. However, the dynamic shear modulus of the composite-modified asphalt decreased owing to the degradation of aromatic aldehydes to fatty aldehydes after ultraviolet aging, leading to softer composite-modified asphalts. In addition, the multiple-stress creep recovery (MSCR) test revealed that the maximum increment in the recovery rate of composite modified asphalt reached to 37.4 %. Moreover, the increasing rate of J nr was significantly lower than that of the control asphalt after long-term aging, particularly at a stress level of 3.2 kPa. Finally, the microstructures of each asphalt sample before and after aging were observed using atomic force microscopy. The surface morphology of the composite modified asphalt after aging was relatively smoother, indicating that the molecular homogeneity of the aging residue of the composite-modified asphalt sample was better than that of the control asphalt sample. [ABSTRACT FROM AUTHOR]

In addition to stresses from dynamic loading, concrete pavements in cold climatic areas are often attacked by freeze-thaw cycling. The interface transition zone (ITZ) is the first section to deteriorate. To study the micro-structure changes of ITZ under the coupling function of fatigue load and freeze-thaw cycling, an indoor-accelerated coupling test was designed. The results show that the coupling effect accelerates the deterioration rate and increases the complexity of micro-crack structures with more pores including crack nucleation. Moreover, the coupling effect significantly reduces impermeability. DOD is the main factor that accelerates the speed of permeability attenuation of concrete. [ABSTRACT FROM AUTHOR]

• The mechanical properties of BA/PPA/SBS composite modified asphalt were studied. • The chemical composition of composite modified asphalt was analyzed. • The interaction mechanism between BA, PPA, SBS, and petroleum asphalt was discussed. To promote the application of environmentally-friendly and sustainable bio-asphalt (BA) in road engineering, polyphosphoric acid (PPA) and styrene–butadienestyrene (SBS) were used to prepare BA/PPA/SBS composite modified asphalt. The mechanical properties of composite modified asphalt and the interaction mechanism of each modifier were investigated through conventional property, rheological property, infrared spectroscopy, fluorescence microscopy test, and gravimetry analysis for SARAs fractions. The conventional property test results show that PPA and BA improve the storage stability of SBS modified asphalt, and the composite modified asphalt with lower SBS content still has excellent performance. The rheological property test results show that the decrease of SBS content has negative effect on the rheological property of asphalt. But in general, the composite modified asphalt has good high-temperature deformation resistance. The IR-spectra of BA before and after reacting with PPA indicates that the chemical composition of the BA in this study was mainly sugar alcohols, and the esterification reaction occurred during reaction with PPA. By comparing the fluorescence images, it was found that the BA significantly improve the dispersion and compatibility of SBS particles in asphalt. The SARAs fractions analysis shows that the composite modified asphalts have higher content of asphaltenes and aromatics. [ABSTRACT FROM AUTHOR]

• Asphalt mixtures contained ATH and MMT were evaluated by CONE test. • Road performance of the ATH/MMT asphalt mixtures was investigated. • ATH/MMT composites show good flame retardant and smoke suppression properties in asphalt mixture. Alumina trihydrate (ATH) and organic montmorillonite (MMT) were used to improve the flame retardancy and smoke suppression properties of highway tunnel asphalt mixture. A series of laboratory tests were conducted on asphalt mixtures to evaluate the effects of ATH/MMT composites on their combustion properties and road performance. Cone calorimeter test results indicate that ATH/MMT delays the ignition time of the asphalt mixture and reduce the total and peak heat release rate of asphalt mixture, thus significantly improving the flame retardancy and smoke suppression properties. The road performance test results show that ATH/MMT additionally improves the deformation resistance, moisture damage resistance, fatigue life and temperature segregation resistance of the asphalt mixture. Although the low- temperature crack resistance of the asphalt mixture is slightly reduced, it still satisfies road performance requirements. [ABSTRACT FROM AUTHOR]

• A new equipment for dynamic flame retardant performance of asphalt materials was designed. • Effect of ATH/OMMT on flame-retardant and smoke-suppression properties of asphalt was studied. • The synergistic flame retardant mechanism of ATH/OMMT composite modified asphalt was revealed. To investigate the flame-retardant performance and mechanism of aluminum hydroxide–organic montmorillonite(ATH/OMMT) composite modified asphalt, the limiting oxygen index test(LOI) and scanning electron microscopy(SEM) were used. In addition, new dynamic flame-retardant test equipment for asphalt was designed. The results show that the ATH/OMMT composite modified asphalt has excellent flame-retardant performance. The dynamic combustion characteristics of asphalt were divided into four stages. ATH/OMMT can delay ignition time, increase ignition temperature, and reduce heat release during combustion. Both ATH and OMMT work together to improve the strength and compactness of the composite modified asphalt carbon layer, thereby improving its flame-retardant properties. [ABSTRACT FROM AUTHOR]

• Effect of OMMT on flame-retardant and smoke-suppression properties of asphalt was studied. • An equipment was designed to characterize the dynamic flame-retardant property of asphalt materials. • The flame-retardant mechanism of OMMT modified asphalt was also investigated. • The flame-retardant and smoke-suppression mechanism model of OMMT modified asphalt was established. To investigate the performance and mechanism of flame retardance and smoke suppression of organic montmorillonite (OMMT) modified asphalt, limiting oxygen index (LOI) and dynamic flame-retardant performance tests were performed. The pyrolysis characteristics of modified asphalt were analyzed using thermalgravimetric-Fourier transform infrared (TG-FTIR) analysis. The results show that the OMMT particle size has little effect on modified-asphalt performance. OMMT increases the ignition time and ignition temperature, and it reduces heat release during combustion. OMMT also significantly inhibits smoke emission during pyrolysis and combustion of modified asphalt. Finally, a flame-retardant and smoke-suppression mechanism model of OMMT-modified asphalt was established. [ABSTRACT FROM AUTHOR]

• The effect of thermal aging on the mechanical properties of ACRMA was evaluated. • The reaction mechanism of ACRMA before and after aging was investigated. • Microwave activation of crumb rubber improved the anti-aging properties of asphalt. The anti-aging properties and related mechanism of microwave-activated crumb rubber-modified asphalt (ACRMA) were evaluated in this study. Physical and rheological tests were conducted on ACRMA before and after simulated thermal aging, and several microcosmic tests were performed to analyze the aging mechanism. The stiffness, plasticity, and viscoelasticity of ACRMA were less affected by aging than crumb rubber-modified asphalt (CRMA). After aging, ACRMA exhibited better high-temperature performance and permanent deformation resistance than CRMA. The thermal aging process of ACRMA was analyzed, and the anti-aging mechanism model was established. The anti-aging performance of ACRMA was better than that of CRMA. [ABSTRACT FROM AUTHOR]

• Effect of ATH and OMMT on flame retardancy properties of asphalt was studied. • VOCs emission properties of asphalt mixture in mixing process was investigated. • The thermal stability and dynamic volatiles release properties of the asphalt binders were analyzed. • Effect of ATH/OMMT composites on engineering performances was evaluated. The objective of this study was to evaluate the flame retardancy and emission properties of asphalt binders containing ATH and OMMT. Limit oxygen index test was performed to evaluate the flame retardancy of each asphalt binder. Volatile organic compound (VOC) emission properties of the asphalt mixture in the mixing process were investigated using a designed test method. Thermogravimetry and Fourier transform infrared spectroscopy were used to evaluate the thermal stability and volatile-release properties of the asphalt binders. The results indicated that both ATH and OMMT effectively suppress the VOC release of the modified asphalt. The flame retardancy and VOC-emission properties of the OMMT/ATH modified asphalt were significantly improved. The addition of ATH/OMMT delayed the thermal decomposition and exhibited good thermal-insulation performance, reducing the heat release during asphalt combustion. Additionally, The ATH/OMMT compounds prevented the breakage of molecular chains in the asphalt, promoting the charring of the asphalt during combustion. According to the engineering-property tests of modified asphalt mixtures, the ATH/OMMT significantly improved the high-temperature performance of the asphalt mixture. However, it slightly reduced the thermal-cracking resistance and moisture susceptibility of the asphalt mixture. [ABSTRACT FROM AUTHOR]

Porous cement stabilized macadam has a good drainage property, but the loss of strength due to calcium leaching can significantly reduce its road performance. The effect of the dosage of fly ash, silica fume, and slag powder on the calcium leaching resistance of porous cement stabilized macadam base material was investigated using the accelerated leaching method with 4 mol/L ammonium chloride. The results show that calcium leaching occurs simultaneously at multiple contact points between the internal cement paste and the leaching solution, and the leaching depth has exceeded the average thickness of the layered cemented paste within 3d. The dissolution of CH crystals and the decalcification of C-S-H gel increase the porosity of cement and reduce the strength of the base material. Volcanic ash reaction of silica fume and fly ash as well as slag powder by alkali excitation and sulfate excitation will consume CH and generate low alkalinity C-S-H gel with better dissolution resistance, which can reduce calcium leaching and delay the loss of strength. The optimum dosages of fly ash, silica fume, and slag powder are 20%, 15%, and 30%, respectively, and their optimum dosages can be estimated on the assumption that the mineral admixtures completely consume CH. [Display omitted] • The calcium leaching mechanism of porous cement stabilized macadam was studied systematically. • The effects of fly ash, silica fume, and slag powder on calcium leaching properties were studied. • Fly ash, silica fume and slag powder can effectively inhibit calcium leaching, with silica fume being the most effective. • Provides a basically consistent optimal dosage of mineral admixtures from both test results and estimation. [ABSTRACT FROM AUTHOR]

Highlights • The effect of materials contents on pavement performance of cold recycled mixture were studied. • Optimal materials content combination was determined by multi-index weighted grey target method. • Fatigue Crack characteristic and resistance mechanism was revealed by SEM test. • Cement-emulsified asphalt mortar improved the microstructure and the interfacial deformation. Abstract To enhance the selection of material content for a cold recycled mixture of emulsified asphalt in hot and rainy areas, the effect of emulsified asphalt content, cement content and Reclaimed Asphalt Pavement (RAP) content on high temperature properties, moisture stability and the fatigue properties of cold recycled mixture were investigated. Based on multi-index weighted grey target theory, the performance of cold recycled mixture were analyzed and the material content were optimized. Then, the crack resistance mechanism of the cement-emulsified asphalt mortar was revealed via a scanning electron microscopy test. The results showed that emulsified asphalt content and cement content mainly affected the high temperature properties, while the effect of the RAP content on water stability was the most significant, and the fatigue performance was significantly affected by various factors under different the stress ratio. The proportions of 3.8% emulsified asphalt, 2% cement and 80% RAP were recommended by grey target optimization. Plentiful hydration products were found positioned in the interfacial crack between the asphalt and aggregate, enhancing the interfacial strength and improving the micro-interface deformation of the cold recycled mixture. [ABSTRACT FROM AUTHOR]

[Display omitted] • The micro modification mechanism of bio-asphalt/TLA modified asphalt are analyzed. • Bio-asphalt improves the low temperature performance of TLA modified asphalt. • The relationship between indexes of modified asphalt and mixture is established. Trinidad Lake Asphalt (TLA) modified asphalt has excellent high temperature performance, but its low temperature performance is poor, which limits its engineering application. But bio-asphalt presents relatively excellent low temperature performance. In this paper, TLA and Bio-asphalt were used as additives to prepare composite modified asphalt with excellent properties both at high and low temperatures. The micro modification mechanism of asphalt was studied by Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC). The macro mechanical behavior of asphalt binder was explored through routine physical property test and rheological property test. Finally, the mechanical properties of asphalt mixture were studied through the routine test of asphalt mixture, and the relationship between the macro and micro indexes of asphalt binder and the high and low temperature performance of asphalt mixture was established through grey correlation. The test shows that the mixing mode of TLA, bio-asphalt and base asphalt is physical blending. Modifiers affect the macro mechanical properties of asphalt by changing the distribution of asphalt components, the size of molecular weight, the interaction strength and arrangement of molecules. TLA improves the performance of asphalt binder at high temperature, but weakens the low-temperature performance. The low temperature performance of TLA modified asphalt was significantly improved by adding bio-asphalt at the cost of slightly reducing the high temperature performance. When the content of bio-asphalt is 9%–12%, the bio-asphalt/TLA modified asphalt and its mixture have better performance on high and low temperature properties than that of base asphalt. The micro indexes such as aromatic ring index and weight average molecular weight are good indicators of the high temperature performance of asphalt mixture. Creep rate (m), equivalent brittle point (T1.2) and stiffness modulus (S) can reflect the low-temperature performance of asphalt mixture. [ABSTRACT FROM AUTHOR]

[Display omitted] • MD simulation revealed anti-freezing mechanism of AFP-modified emulsified asphalt. • Microscopic properties of AFP-modified emulsified asphalt were observed. • Rheology and frost resistance of AFP-modified emulsified asphalt studied. • MD simulations were consistent with microscopic and freeze resistance test results. In this study, biological modification technology was utilized to improve the frost resistance of pavement. By adding biological antifreeze protein to asphalt-based materials, a biomodified emulsified asphalt layer with active antifreeze qualities was created. The mixing mode and its anti-freezing efficacy were investigated using molecular dynamics (MD) simulations. The anti-freezing protein (AFP) was embedded on the asphalt surface, and the structure was completed with asphalt application in two phases. After AFP was attached to the surface of the asphalt binder, the structure remained stable at low temperatures, inhibiting icing and producing a thermal hysteresis differential. Hydrogen bonding and Van der Waals forces influence ice molecule aggregation, and AFP can reduce their effect and induce ice crystal melting. Scanning electron microscopy (SEM) and fluorescence microscopy (FM) revealed that the AFP surface was uneven and anchored to the asphalt surface. The overall structure was complete, with a two-phase distribution that corresponded with the MD results. The anti-icing test results demonstrated that the AFP-modified emulsified asphalt coating effectively inhibited ice condensation and could change the ice crystal growth pattern. The rheological test results revealed that AFP had a slightly negative effect on the high-temperature deformation resistance of the asphalt binder. Environment friendly AFP-modified emulsified asphalt can significantly improve the anti-freezing characteristics of the pavement. [ABSTRACT FROM AUTHOR]

[Display omitted] • Bio-antifreeze protein is used to prepare pavement anti-freezing coating. • The anti-freezing performance of bio-AFP-modified emulsified asphalt coating was tested. • The road performance of bio-AFP-modified emulsified asphalt coating was tested. Natural organisms use their own biological antifreeze proteins (AFP) to cope with cold environments. Based on this natural phenomenon, we herein use biological AFP and asphalt-based materials to prepare road anti-icing coating materials and subsequently study its storage stability and anti-icing performance. The storage stability test, fluorescence microscope analysis, scanning electron microscope analysis, and infrared spectrum analysis demonstrated that when the AFP powder content was not more than 5%, it was evenly dispersed in the emulsified asphalt, had good stability, did not undergo a chemical reaction, and retained the molecular activity of AFP. Combined with the anti-icing, pull-out, and falling ball impact tests, the addition of biological AFP powder demonstrates obvious anti-icing performance; furthermore, with an increase in the powder content, the anti-icing effect is improved. The road performance test showed that the coating had good durability and spalling resistance. When the spraying amount of the coating on the asphalt pavement is ≤ 0.4 kg/m2, the BPN value and TD value meet the requirements of the specification. The application of a biological AFP-modified emulsified asphalt coating can significantly improve the anti-icing performance of roads and does not harm ecological environments. [ABSTRACT FROM AUTHOR]

• The mechanical properties of hybrid fiber-reinforced SAP modified concrete was studied. • The rule of shrinkage development of reinforced hybrid fiber-reinforced SAP modified concrete was investigated. • The fracture properties of hybrid fiber-reinforced SAP modified concrete were evaluated. • The mechanism of hybrid fiber-reinforced SAP modified concrete was analyzed. This study investigated the shrinkage and fracture properties of superabsorbent polymers (SAP)-modified concrete with and without hybrid fibers. For this purpose, uniaxial compressive, four-point bending, three-point bending, dry shrinkage and plastic cracking tests were carried out on specimens produced using hybrid fiber and SAP. In addition, microstructural analysis was performed using scanning electron microscopy (SEM) to reveal the underlying mechanisms increasing the toughness and cracking resistance of the hybrid fiber-reinforced SAP modified concrete. The results showed that the addition of the hybrid fiber compensated for the strength loss caused by the SAP and effectively increased the strength of the concrete. In addition, the fracture process of the hybrid fiber -reinforced SAP modified concrete exhibited a better toughness than that of SAP modified concrete. Compared with that of SAP modified concrete, the fracture energy was increased by 105.95%, and the total cracking area per unit area was reduced by 73.7%. The addition of both the hybrid fiber and SAP significantly reduced the shrinkage of the concrete, mainly by decreasing the shrinkage rate of the concrete and accelerating the time required for the concrete shrinkage to stabilize. In light of the SEM images, it was suggested that the SAP transported a portion of free water into the concrete and promoted the hydration reaction. The hybrid fiber improved the internal pore structure of the concrete and acted as a reinforcement in the concrete. In general, the SAP and hybrid fiber worked together to increase the toughness and cracking resistance of the concrete. [ABSTRACT FROM AUTHOR]