Freeze-thaw Splitting Research Articles

Composition and Evaluation on Road Performance of SBS/PTW High-Viscosity-Modified Asphalt and Its Mixtures for Ultrathin Overlays

As a highway pavement maintenance technology, the road performance of the ultra-thin overlay depends heavily on the performance of asphalt cement. For the preparation of high-performance-modified asphalt suitable for ultrathin overlay, the reactive blending technology was used based on SBS modified asphalt and combined with a penetration test, softening point test, ductility test, dynamic viscosity test, and viscous toughness test to study the optimal blending ratio of high-viscosity modified asphalt. Further, the rolling thin-film oven test (RTFOT), dynamic shear rheological (DSR) test, and Brookfield viscosity test are used to evaluate the technical properties of SBS/PTW modified asphalt under the best mixing ratio. Finally, the SMA-13 asphalt mixture was prepared with SBS/PTW high-viscosity modified asphalt and evaluated through a rutting test, low-temperature bending test, immersion Marshall test, freeze-thaw splitting test, structural depth test (TD), and British pendulum number (BPN) test. These results showed that the best blending mass ratio of high-viscosity modified asphalt is 6% SBS + 4% solubilizer + 0.2% PTW + 0.2% nano-ZnO. All technical property indexes of the prepared SBS/PTW high-viscosity modified asphalt meet the requirements of an ultra-thin overlay binder. The dynamic viscosity at 60°C reaches 64204 Pa·s, and the viscosity and toughness are 25.4 N·m and 20.9 N·m, respectively. SBS/PTW high-viscosity modified asphalt under dynamic shear rheology (DSR) test is classified as PG88 at high temperature. The rutting factor changes the smallest before and after aging, and it has excellent anti-aging performance. Furthermore, the asphalt mixture prepared by SBS/PTW high-viscosity modified asphalt has excellent high and low-temperature performance, water stability, and skid resistance performance. All properties meet the requirements of the ultra-thin overlay. This study demonstrated that the SBS/PTW high-viscosity modified asphalt possessed high viscosity properties, which can be used in the ultra-thin overlay and other highly demanding working environments.

Properties of SBS/MCF-Modified Asphalts Mixtures Used for Ultra-Thin Overlays

In order to produce high-viscosity and high-toughness asphalt for ultra-thin overlays, the conventional asphalt cement was modified with high-content SBS and micro carbon fiber (MCF). The performances of the modified asphalt were studied by tests of penetration, softening point, ductility, kinematic viscosity, multiple stress creep recovery (MSCR), and by dynamic shear rheometer (DSR) and bending beam rheometer (BBR). Mixture properties were studied by tests of rutting, low-temperature bending, freeze–thaw splitting, four-point bending fatigue and dynamic modulus. The results reflect that the addition of MCF could enormously improve the high- and low-temperature properties, increase the viscosity of asphalt, and improve the toughness of asphalt. When SBS content was 6%, with the increase of MCF content, G*/sin δ and R values first increased and then decreased, and the Jnr value first decreased and then increased. When MCF content was 0.8%, the overall performance was best. Adding MCF into an asphalt mixture or increasing the content of SBS improved the rutting resistance, low-temperature crack resistance, water stability, and fatigue performance of the asphalt mixture. At the same temperature and frequency, there was little difference in phase angle between the 6%SBS + 0.8%MCF and 5%SBS + 0.0%MCF modified asphalt mixtures, and the dynamic modulus was slightly higher over the whole range. It can be concluded that the addition of SBS and MCF can enormously enhance the viscosity and toughness of asphalt. The viscosity of the 6%SBS + 0.8%MCF modified asphalt met the performance requirements of high-viscosity asphalt. When used for ultra-thin overlays, it had great road service performance and met the application requirements.

Conversion of Municipal Solid Waste Incineration Bottom Ash in Asphalt Pavements

Abstract Municipal waste incineration (MSWI) is a widely used method in solid waste treatment that can reduce the generation of landfill waste. Meanwhile, MSWI-bottom ash (BA) can be employed as a substitute for aggregates in asphalt mixtures. This study aims to assess the feasibility and influence of MSWI-BA substitution for natural limestone aggregates in asphalt mixtures to reduce garbage accumulation and save natural resources. Through conventional methods, the energy dispersive X-ray spectrometer, and scanning electron microscope experiments, the physical and chemical features of MSWI-BA and natural limestone aggregate were analyzed. A Marshall mix design determined the optimum asphalt content of asphalt mixtures with various MSWI-BA contents. The road performances of asphalt mixtures with different MSWI-BA contents were studied using rutting, low-temperature splitting, freeze–thaw splitting, and Marshall immersion tests. The experiment results show that adding MSWI-BA to asphalt mixtures would decrease water stability. High-temperature stability is excellent when adding 10 % MSWI-BA, and low-temperature crack resistance is best at 20 % MSWI-BA content. MSWI-BA could be recycled in the asphalt pavement, and 10 % is recommended.

Evaluation of engineering properties of Fiber-reinforced Usual-temperature Synthetic Pitch (USP) modified cold mix patching asphalt

As a common-used pothole repairing material, cold mix patching asphalt (CMA) has been widely used in practice. This article aims to develop a novel CMA with good overall performance and better environmental-friendliness. A few environmental-friendly ingredients, including a modifier named Usual-temperature Synthetic Pitch (USP), polyester-basalt composite fibers, a commercial anti-stripping agent, a commercial tackifier and biodiesel, were utilized for preparing Fiber-reinforced USP modified CMAs (FUAs). Laboratory tests, including workability assessment tests, Marshall stability tests, boiling water tests, rolling sieve cohesion tests, freeze-thaw splitting tests, wheel tracking tests and three-point bending tests, etc. were conducted to evaluate the workability, Marshall stability, adhesion, moisture susceptibility, rutting resistance, bending resistance and storage stability. Two mix designs of the cutback (termed as Scheme 1 and 2) with weight ratios of 100:6:18:0.3:0.6 and 100:6:20:0.4:0.8 for binder: USP: biodiesel: anti-stripping agent: tackifier were considered. Effect of fiber content (0.2%, 0.3%, 0.4% and 0.5% by aggregate weight) was also investigated considering an optimal polyester to basalt fiber weight ratio of 3:2. The results show that the optimal fiber content is 0.4%. The engineering properties of FUAs meet the construction requirements, and they also present good storage stability. Scheme 2-based cutback shows better workability, smaller penetration and better binder-aggregate adhesion than the Scheme 1-based cutback; consequently, the Scheme 2-based FUA presents advantages over Marshall stability, rutting resistance and bending resistance. Compared with Styrene-Butadiene-Styrene (SBS) modified CMAs, FUAs possess better overall performance and advantages over environmental conservation. The FUAs, therefore, have good application prospects in pavement repair.

Low-Temperature Performance of Asphalt Mixtures Modified by Microencapsulated Phase Change Materials with Various Graphene Contents

Microencapsulated phase change materials (PCMs) added to conventional ones can store excessive heat energy and reduce thermal stresses. In this study, melamine–formaldehyde resin phase change microencapsulated PCMs, with different contents of graphene (CG), were added to asphalt mixtures, in order to reduce their low-temperature cracking, induced by thermal stresses. Low-temperature and heat-conducting/storing performance of the obtained mixtures was examined via beam bending tests, semi-circular bending low-temperature performance tests, thermal conductivity tests and volume-specific heat capacity tests. Besides, the prepared asphalt mixtures’ water stability and high-temperature stability values were obtained via freeze-thaw splitting and wheel tracking tests. The low-temperature performance of PCM-modified asphalt mixtures was evaluated via their bending strain energy densities, with one of the PCM-modified asphalt mixtures, namely CGMFPCM3, synthesized by the authors, was 1.7 times higher than that of the common asphalt mixture. Although the dynamic stability of all three PCM-modified mixtures was deteriorated by 68, 50, and 20% compared to the common one, that of CGMFPCM3 still complied with the standard requirement. Thermal conductivity and volume-specific heat capacity of the asphalt mixture at 278.15 K was enhanced by 5 and 43%, respectively, after adding CGMFPCM3. It is recommended for reducing the temperature variation-induced cracking in the asphalt pavement. Thermal conductivity and volume-specific heat capacity can be used for evaluating the temperature-regulating performance of asphalt mixtures.

Investigation on the Effects of RAP Proportions on the Pavement Performance of Recycled Asphalt Mixtures

In-plant hot mix recycling technology has been widely used in maintenance and reconstruction due to its good recycling performance. However, the utilization rate of recycled asphalt pavement (RAP) is still only 10–25%, resulting in excessive accumulation and landfilling of RAP materials, which fails to promote the sustainable value of RAP in recycling. Therefore, this paper comprehensively explores the pavement performance of AC-20 ordinary asphalt recycled mixture and AC-13 modified asphalt recycled mixture with different proportions of RAP. The pavement performance test includes the dynamic modulus, rutting, dynamic creep, semicircular bending, and freeze-thaw splitting tests. The results show that, with the increase of RAP content, the mechanical properties and high-temperature properties of the two types of recycled asphalt mixtures are improved, the low temperature properties and moisture susceptibility properties are enhanced first and then weakened, and the best performance is reached when RAP content is 20 and 40%, respectively. According to the entire pavement performance test results, the influence of RAP content on AC-13 recycled modified asphalt mixtures is relatively smaller than that of AC-20 normal recycled asphalt mixtures. The addition of rejuvenator can improve the low-temperature performance and moisture susceptibility of recycled asphalt mixtures to a certain extent, especially for AC-20 ordinary recycled asphalt mixture. Consequently, it is suggested to use AC-13 recycled modified asphalt mixture in the upper layer of road; the RAP content can reach 20%, and rejuvenator can be used to improve its moisture susceptibility and low-temperature performance. AC-20 ordinary recycled asphalt mixture can be used in the middle surface layer, and the RAP content can reach 40%, or using AC-13 recycled modified asphalt mixture, the RAP content can reach 50%.

Evaluation of the adhesion property and moisture stability of rubber modified asphalt mixture incorporating waste steel slag

The present study was conducted to recycle waste tire rubber and steel slag (SS) in asphalt pavement and investigates the moisture stability of asphalt mixtures incorporating these solid wastes. To this end, two types of aggregates (SS and diabase), three kinds of SS content and multiple freeze–thaw cycles were considered and three kinds of adhesion assessment methods: pull-out test and surface free energy (SFE) method, and freeze–thaw splitting test were performed. Three corresponding adhesion evaluation indicators like adhesion strength, SFE characteristics, and tensile strength ratio were obtained and six energy parameters were introduced to characterize moisture susceptibility of asphalt mixture. To explore the relations between the SFE parameters and the adhesion evaluation indicators, a grey correlation analysis method was adopted. Asphalt mixtures with high consumption of SS obtained a better moisture resistance because SS has a superior adhesion strength and higher SFE components than diabase aggregate. Stripping energy increase was found to be the main failure mode of the asphalt rubber-SS aggregate system. SFE method provides a comprehensive and accurate evaluation of adhesion property of loose asphalt rubber–SS aggregate system and moisture stability of compacted asphalt mixtures.

Effects of different types of acid rain on water stability of asphalt pavement

As is known to all, China is one of the countries with more acid rain in the world, and acid rain is mainly distributed in the southern humid climate area of China. However, the construction of semi-flexible asphalt pavement exposed to acid rain environment is a very realistic problem. In order to clarify the influence of different types of acid rain on the water stability of semi-flexible pavement, sulfuric acid type acid rain, nitric acid type acid rain and mixed type acid rain were prepared in this paper, and the semi-flexible specimens were soaked periodically. The water stability of semi-flexible pavement under different types of acid rain corrosion was evaluated macroscopically by standard Marshall test, immersion Marshall test, freeze-thaw splitting test and vacuum saturation test. It was concluded that the Marshall stability, immersion Marshall residual stability, freeze-thaw splitting strength ratio and vacuum saturation residual stability of semi-flexible pavement under different types of acid rain showed different degrees of decline.The reasons for the decline of water stability of semi-flexible pavement under different types of acid rain corrosion were analyzed by scanning electron microscopy and infrared spectroscopy. It was concluded that the acidification condition of rainwater was the main reason for the decrease of ductility, viscosity and plasticity of petroleum asphalt, which affected the binding force between petroleum asphalt and limestone aggregate, and ultimately led to the decline of water stability of semi-flexible pavement.Based on the molecular dynamics theory, the molecular dynamics model of acid rain corrosion asphalt mixture is established. According to the sensitivity of acid components to the main components of semi-flexible asphalt mixture, the asphalt, oil, resin and calcium carbonate with the most content in semi-flexible asphalt mixture are selected to simulate and study. The changes of bonding energy and diffusion coefficient of asphalt mixture under different types of acid rain are calculated and analyzed. It is concluded that sulfuric acid acid rain has the greatest influence on the water stability of semi-flexible specimens, followed by mixed acid rain, and the influence of nitric acid rain is relatively small.

Research on the Impact of Recycled Asphalt Mixture on Road Performance Based on New Thermal Recycling

Different binder content to RAP Regeneration SBS modified asphalt mixture for road performance to SBS modified asphalt (I-D type) as an index, determine the optimum dose of new heat regenerating agent and different RAP regeneration, and prepared different recycled asphalt, which have differences in RAP content. The performance of recycled asphalt mixture with different RAP content was evaluated by freeze-thaw splitting test. Rut test and Low temperature trabecular bending test. The correlation between RAP content and pavement performance was analyzed by grey system correlation analysis method. According to the experimental verification results, it can be known that increasing the content of RAP material can improve the high-temperature performance of reclaimed asphalt, but will result in a qualitative decrease in low-temperature performance and water temperature, but the above-mentioned performance can reach the required level, Shows that new heat regenerators play a role in the road performance of RAP materials, and for the RAP material utilization ratio of more than 50%, as for the gray correlation analysis, it can be found that there is a close correlation between the low-temperature performance of recycled asphalt mixture and the content of RAP material. The low temperature cracking resistance of asphalt mixtures will change significantly due to the slight changes in RAP materials.

Mechanical behaviors of asphalt mixtures modified with European rock bitumen and waste cooking oil

The use of modifiers as an effective solution to improve the performance of asphalt pavement has been gaining popularity in recent years. The objective of this research was to investigate the effect of compound modification of asphalt using European rock bitumen (ERB) and waste cooking oil (WCO) on the macroscopic mechanical properties of asphalt mixtures. WCO can effectively improve the low-temperature performance of the compound-modified asphalt, and ERB can make up for the adverse effects of waste cooking oil on high-temperature performance. The experimental plan considered asphalt mixture AC-13 with four ERB/WCO modified asphalt combinations (18% ERB + 0% WCO, 2% WCO + 18% ERB, 4% WCO + 18% ERB and 4% WCO + 12% ERB) and Marshall test, rutting test, indirect tensile strength test at low temperature, freeze-thaw splitting test, and the long-term aged test, were conducted to evaluate the properties of the asphalt mixture in the work. The modified asphalt (18% ERB + 0%WCO, 2%WCO + 18%ERB, 4%WCO + 18%ERB, and 4%WCO + 12%ERB), could effectively improve the high-temperature stability, water stability, low-temperature stability, and aging resistance of the asphalt mixture. According to the overall behavior, 4%WCO + 18%ERB was the best combination.

Mechanism of Polyurethane Binder Curing Reaction and Evaluation of Polyurethane Mixture Properties

This study focuses on analyzing the curing reaction mechanism of polyurethane (PU) binders and comprehensively evaluating the PU mixture’s properties. The former was investigated by conducting a Fourier transform infrared spectroscopy (FTIR) test on PU binders with different curing times. The volume change characteristics, construction operation time, and strength formation law were clarified through the splitting tensile test of PU mixtures under different environmental conditions. The optimal PU mixture stacking time and curing time under different environmental conditions were determined. The properties of the PU mixture and asphalt mixture were evaluated and compared through a rutting test, low-temperature bending test, freeze–thaw splitting test, and four-point bending fatigue test. The results show that the physical and chemical curing of the PU binder occurred within the first 24 h of curing, and the reaction speed gradually accelerated to form a polyurea structure 24 h later. It is recommended to stack the PU mixture for 4 h before compaction and to cure it for 2 days before opening under the conditions of 50% humidity and 15–40 °C surrounding temperature. The PU mixture shows better temperature stability and fatigue resistance than the asphalt mixture, and the splitting tensile strength of the PU mixture before and after the freeze–thaw splitting test is also higher. It is clear that the PU mixture is a green road building material with good performance.

Study on the Optimum Steel Slag Content of SMA-13 Asphalt Mixes Based on Road Performance

To reduce the use of aggregates such as limestone and basalt, this paper used steel slag to replace some of the limestone aggregates in the production of SMA-13 asphalt mixes. The optimum content of steel slag in the SMA-13 asphalt mixes was investigated, and the performance of these mixes was evaluated. Five SMA-13 asphalt mixes with varying steel slag content (0%, 25%, 50%, 75%, and 100%) were designed and prepared experimentally. The high-temperature stability, low-temperature crack resistance, water stability, dynamic modulus, shear resistance, and volumetric stability of the mixes were investigated using the wheel tracking, Hamburg wheel tracking, three-point bending, freeze–thaw splitting, dynamic modulus, uniaxial penetration, and asphalt mix expansion tests. The results showed that compared to normal SMA-13 asphalt mixes, the high-temperature stability, water stability, and shear resistance of the SMA-13 asphalt mixes increased and then decreased as the steel slag content increased. All three performance indicators peaked at 75% steel slag content, and the dynamic stability, freeze–thaw splitting ratio, and uniaxial penetration strength increased by 90.48%, 7.39%, and 88.08%, respectively; however, the maximum bending tensile strain, which represents the low-temperature crack resistance of the asphalt mix, decreased by 5.98%. The dynamic modulus of the SMA-13 asphalt mixes increased with increasing steel slag content, but the volume expansion at a 75% steel slag content was 0.446% higher than at a 0% steel slag content. Based on the experimental results, the optimum content of steel slag for SMA-13 asphalt mixes was determined to be 75%.

Effect of Rejuvenators on the Workability and Performances of Reclaimed Asphalt Mixtures.

The use of rejuvenators has enhanced the workability of asphalt mixtures containing the reclaimed asphalt pavement (RAP). This conclusion is based on the determination of viscosity of asphalt binders, while not validated from reclaimed asphalt mixtures. In this study, the effect of two rejuvenators (ordinary and emulsified rejuvenator) on the workability of reclaimed asphalt mixtures was evaluated by measuring the mixing torque and determining the air void content of reclaimed mixtures. In addition, their effects on the performances of reclaimed mixture were studied via the three indexes tests, rutting test and freeze-thaw splitting tests. The experimental results show that mixing torque and air void content of reclaimed mixtures with the emulsified rejuvenator is 4% and 6% lower than that with the ordinary rejuvenator, respectively. This indicates that improvement of the workability of reclaimed mixtures can be achieved by using an emulsified rejuvenator, but not by an ordinary rejuvenator. That is also the reason that at least 20% greater high-temperature stability is found for reclaimed mixtures by using the emulsified rejuvenator than using the ordinary rejuvenator. In addition, reclaimed mixtures with the emulsified rejuvenator show similar moisture susceptibility to that with the ordinary rejuvenator. This study provides a feasible method to assess the workability effect of rejuvenators on reclaimed mixtures directly and recommends the use of an emulsified rejuvenator to improve the workability and high-temperature stability of reclaimed mixtures.

Study on anti-aged durability of HMA based on inherent and improved performance

PurposeThe purpose of this study is to compare and analyze the anti-aging durability of asphalt and asphalt mixture under the conditions of inherent and improved performance. The research contents include: the mechanical properties (dynamic stability, bending strain, freeze-thaw splitting tensile strength ratio (TSR)) of different modified asphalt mixtures were tested by using the best modified asphalt.Design/methodology/approachThe anti-aging durability of different modified asphalt was analyzed by using the results of macro tests such as penetration and softening point as evaluation indexes. Meanwhile, the change of the asphalt colloid instability index (Ic) in the aging process was used as the evaluation index to verify the results of the macroscopic test, and the best modified asphalt was obtained. On this basis, the composition of different modified asphalt mixtures was designed by using the best modified asphalt. Meanwhile, water stability was used as evaluation indexes to study the anti-aging durability of different modified asphalt mixtures.FindingsThe results show that styrene-butadiene-styrene (SBS) modified asphalt has better aging resistance. Due to the special storage time, the performance of rubber asphalt is also the best. Meanwhile, in terms of modified asphalt mixture, its high temperature performance and durability of anti-aging is as follows: 4% SBS /16% rubber modified asphalt mixture (IV) > 4% SBS modified asphalt mixture (II) > asphalt mixture (90#) (I) > 16% rubber modified asphalt mixture (III). The low temperature performance and durability of anti-aging is as follows: Ⅱ > IV > Ⅰ > Ⅲ. The water stability performance and durability of anti-aging is as follows: IV > Ⅲ > Ⅱ > Ⅰ.Originality/valueThe research results have important theoretical and guiding significance for exploring the change of intrinsic properties and improved properties of asphalt and asphalt mixture in the aging process and revealing the anti-aging mechanism of different modified asphalt mixtures.

Laboratory Evaluation on the Road Performance of Diatomite Modified Porous Asphalt Mixture

Porous asphalt mixture (PAM) is an indispensable pavement material for the construction of sponge city with low-cost and environment friendly characteristics, which conducive to replenishing urban groundwater and alleviating the heat island effect. The main purpose of this article is to explore the change of road performance and water permeability of PAM under different diatomite dosage, and determine the optimal amount of diatomite content. First, the volume characteristics of diatomite permeable asphalt mixture (D-PAM) were measured by Darcy’s law, the void of D-PAM decreased slightly according to the test results. Furthermore, based on the water damage Marshall test and freeze-thaw splitting test, the water stability of D-PAM increases significantly with the increase of diatomite content. At last, the low-temperature anti-cracking performance and ductility of D-PAM were carried out based on the acoustic emission (AE) detector and the Low temperature universal mechanics testing machine. According to the experimental results, it is recommended that the content of diatomite is 10%.

Study on the effect of phase change energy storage material on the performance of asphalt mixture

Aiming at the high and low temperature diseases of asphalt pavement, in order to improve the environmental adaptability of asphalt pavement, the road phase change temperature-regulating composite material (DTC) was selected to prepare phase change asphalt mixture, and the pavement performance of phase change asphalt mixture was studied by indoor temperature rise and drop test, rut test, immersion Marshall test, freeze-thaw splitting test and low temperature bending test. The results show that DTC reduces the rate of rise and drop during the indoor heating process. DTC can effectively absorb heat for 140min at 40°C and can effectively release heat for 80min at -18°C. With the increase of DTC content, the dynamic stability, residual stability and splitting strength ratio of phase change asphalt mixture show a trend of decrease, while the low temperature failure strain shows a trend of first increase and then decrease.

Quantitative assessment and mechanism analysis of modification approaches for cold recycled mixtures with asphalt emulsion

Cold recycled mixtures with asphalt emulsion (CRMEs) are environmentally friendly and cost-effective materials widely used in asphalt pavement maintenance and rehabilitation (M&R). However, CRMEs exhibit lower mechanical performance and durability than hot-mix asphalt. This study aims to evaluate the effects of different modification approaches on the mechanical properties and durability of CRMEs. To this end, four optimal additives, including the rejuvenation agent (RA), basalt fibres (BFs), styrene–butadiene rubber (SBR) latex, and Buton rock asphalt (BRA), were added to CRMEs during the mixing procedure. Comprehensive laboratory tests including immersion splitting and freeze–thaw splitting tests, high-temperature rutting tests, low-temperature semi-circle bending tests, and indirect tensile fatigue tests were conducted to evaluate the mechanical properties of the modified CRMEs. In addition, the radar chart method was performed to quantitatively assess the effects of the multiple modification approaches. To investigate the influence mechanisms, microscopic features of the modified CRMEs, such as the compactness of the mortar and bonding sufficiency of the interface, were detected by scanning electron microscopy. The results showed that the addition of RA, SBR latex, and BRA can improve the comprehensive performance of the modified CRMEs. Among these additives, RA had the most significant effect, followed by BRA. These findings aid in selecting modifiers to improve the performance and durability of CRMEs in practical engineering applications.

Characterization and microwave healing properties of different asphalt mixtures suffered freeze-thaw damage

Asphalt materials display the inherent ability to heal micro-cracks and the microwave heating technique can help accelerate this process thus promoting the creation of a durable asphalt pavement. The objective of this study is to investigate the difference in healing potential between two representative types of asphalt mixtures, namely dense asphalt concrete (AC-13) and open-graded friction course concrete (OGFC-13), suffered freeze-thaw (F-T) damage. In particular, OGFC concrete is especially susceptible to water damage due to its high percentage of air voids. The effect of gradation and F-T damage on the healing performance of asphalt mixtures is appraised by means of three-point bending test, freeze-thaw splitting test and X-ray computed tomography test. Results demonstrate that the gradation exerts a clear influence on the microwave healing behavior and microwave absorber content. In addition, the mechanical strength of mixtures characterized by F-T damage can be partially restored with microwave heating treatment: the healing efficiency of OGFC asphalt specimen after three cycle F-T cycles is still satisfactory. As probed with X-ray computed tomography, the proportion of micropores increases, while the amount of mesopores and macropores decrease after the microwave treatment. However, thermal heating technics are not suitable for further healing when the structural deformation of the OGFC sample occurs due to the F-T damaging process. The research outcomes can contribute to understand the microwave healing behavior for different asphalt mixture types and characterize the healing mechanism of mixtures suffered F-T damage.

Study on the effect of Acid Rain erosion on the Road performance of Steel Slag Asphalt mixture

in order to study the influence rules of acid rain erosion on the road performance of steel slag asphalt mixture, the artificial acid rain solution of pH=2 and distilled water of pH=7 were used to carry out periodic immersion erosion test on asphalt mixture with different amount of steel slag (0, 30%, 50%, 70%), then rutting test, low temperature bending test and freeze-thaw splitting test were carried out on the asphalt mixture eroded by acid rain. The results show that after soaking in acid rain solution, the high temperature stability, low temperature crack resistance and water stability of each steel slag asphalt mixture decrease, and the decreasing range increases with the increase of soaking period. The high temperature stability, low temperature crack resistance and water stability of steel slag asphalt mixture soaked in distilled water also decreased, but the decrease was small.

Design and Performance Investigation of Drainage Ultra-Thin Wearing Course Based on Diatomite-Supported Epoxy-Modified Asphalt Mixture

Abstract The high-performance epoxy resin–modified asphalt has been widely applied in the development of steel deck pavement and roads with heavy traffic. However, the poor compatibility between the epoxy resin and matrix asphalt has never been solved completely. In this study, epoxy resin was supported on diatomite with a large pore structure, so that epoxy resin was evenly dispersed into asphalt for improving the compatibility. The diatomite-supported epoxy-modified asphalt (DEA) binder was prepared and applied to the drainage ultra-thin wearing course mixture (DUWM). Six different DEA-DUWM were designed with a 2.36-mm sieve size, which was the key sieve size. The general asphalt content was calculated by the asphalt film thickness test. The optimal asphalt content was determined by the Cantabro test and the Schellenberg binder drainage test. The best curing time was determined by the Marshall test. Taking the Japanese epoxy resin–modified asphalt (TAF) as the comparison group, the high-temperature rutting test, low-temperature bending beam test, immersion Marshall test, freeze-thaw splitting test, immersion Cantabro test, water seepage test, surface friction coefficient test, and Manual sand laying test were carried out for DEA-DUWM and TAF-DUWM under the same gradations and test conditions. The results indicate that DEA-DUWM has excellent high-temperature rutting resistance; the maximum low-temperature bending strain is nearly 25 % less than that of TAF-DUWM, but the low-temperature cracking resistance can still meet the specification requirements of China. The addition of diatomite and the air void of the mixture have an effect on the low-temperature anticracking performance of DUWM, and DEA-DUWM has a remarkable high-temperature and low-temperature moisture resistance, drainage, and skid resistance. The air void of the mixture has a great influence on the freeze-thaw resistance of DUWM. The asphalt type has a marginal effect on the drainage and antiskid properties. It is suggested that the DUWM design’s target air void content should not be less than 17 %, and it can be improved properly in an area with heavy rainfall.