Freeze-thaw Splitting Test Research Articles

Research on Recycling of Phosphorus Tailings Powder in Open-Graded Friction Course Asphalt Concrete

The reuse in high-value materials is one of the important resource utilization approaches of phosphorus tailings. At present, a mature technical system has been formed on the reuse of phosphorus slag in building materials, and silicon fertilizers in the extraction of yellow phosphorus. But there is a lack of research on the high-value reuse of phosphorus tailings. In order to make safe and effective utilization of phosphorus tailing resources, this research concentrated on how to solve easy agglomeration and difficult dispersion of phosphorus tailing micro-powder, when it was recycled in road asphalt. In the experimental procedure, phosphorus tailing micro-powder is treated in two methods. One method is to directly add it with different contents in asphalt to form a mortar. Dynamic shear tests were used to explore the effect of phosphorus tailing micro-powder on the high-temperature rheological properties of asphalt influence mechanism of material service behavior. The other method is to replace the mineral powder in asphalt mixture. The effect of phosphate tailing micro-powder on the water damage resistance in open-graded friction course (OGFC) asphalt mixtures was illustrated, based on the Marshall stability test and the freeze-thaw split test. The research results show that the performance indicators of the modified phosphorus tailing micro-powder meet the requirements for mineral powder in road engineering. Compared with standard OGFC asphalt mixtures, the residual stability of immersion and freeze-thaw splitting strength were improved when replace the mineral powder. The residual stability of immersion increased from 84.70% to 88.31%, and freeze-thaw splitting strength increased from 79.07% to 82.61%. The results indicate that phosphate tailing micro-powder has a certain positive effect on the water damage resistance. These performance improvements can be attributed to the larger specific surface area for phosphate tailing micro-powder than ordinary mineral powder, which can effectively adsorb asphalt and form structural asphalt. The research results are expected to support the large-scale reuse of phosphorus tailing powder in road engineering.

Analysis on factors affecting moisture stability of steel slag asphalt concrete using grey correlation method

The moisture sensitivity of steel slag asphalt concrete has been receiving close attention from the road construction industry. Although researchers have conducted numerous studies on the water damage resistance of steel slag asphalt concrete, the evaluations are inconsistent, and it is difficult to distinguish the weighting ratios of the factors influencing the moisture sensitivity of asphalt concrete in the current study. Based on the water immersion Marshall test, freeze-thaw splitting test, and Hamburg rutting test, this study tested the water stability of asphalt concrete prepared from steel slag by different processes, aiming to illustrate the influence of the preparation process of aggregates on the water sensitivity of asphalt concrete. The results showed that the water stability of asphalt concrete prepared from steel slag obtained by the roller method and the hot smothering method was better than that of limestone asphalt concrete, while the water stability of asphalt concrete prepared from steel slag was inferior to that of limestone concrete. Subsequently, the adhesion between the three steel slag and limestone respectively and asphalt was compared in the modified boiling method, and the surface morphology structure of the four aggregates was characterized by scanning electron microscopy (SEM), and the results showed that the adhesion between the aggregates and asphalt was consistent with the moisture sensitivity of asphalt concrete. Finally, the comprehensive analysis concluded that the main factors affecting the water stability of steel slag asphalt concrete were asphalt, aggregate, gradation, and particle size, in that order.

Key Performance Analysis of Emulsified Asphalt Cold Recycling Mixtures of the Middle Layer of Pavement Structure.

In the maintenance engineering of asphalt pavement, it is often encountered that both the surface and middle layers are damaged and need to be maintained. The cold in-place recycling technology can be used to simultaneously treat multi-layer diseases and reduce the waste of pavement materials. The cold in-place recycling mixture is rarely used for high layer of pavement structure in high-grade highway. In the supporting practical engineering, the emulsified asphalt cold in-place recycling mixtures were paved as the middle layer of pavement structure by the laying of an overlay. In order to comprehensively evaluate the material performances, coring samples were drilled after cold recycling pavement opening to traffic, and different performance tests were carried out based on the coring samples. The newly paved SMA mixtures were set as the control group. The high temperature stability of cold recycling mixture was analyzed by dynamic creep test and MMLS3 accelerated loading test. Then, the cracking resistance of cold recycling mixture was studied by semi-circular bending test. Finally, the effect of curing time on splitting strength of cold recycling mixture was measured, and the moisture susceptibility was analyzed by dry-wet splitting test and freeze-thaw splitting test. The test results showed that the high temperature stability of cold recycling mixture was worse than SMA mixture. For the cold recycling mixture, the deformation value at the early stage and deformation rate at the stable stage were larger than SMA mixture in the accelerated loading process, and shear failure at high temperature occurred earlier. The cracking resistance of cold recycling mixture was worse than SMA mixture because of the aging effect of the old asphalt and adverse influence of the added cement binder. The effect of curing time on splitting strength of cold recycling mixture was significant, and two stable periods of early strength were, respectively, reached after curing 3 days and 7 days. The indexes of moisture susceptibility, including dry-wet splitting strength ratio and freeze-thaw splitting strength ratio, were obviously lower than that of SMA mixture, and the test values not up to the standard requirement existed. For the emulsified asphalt cold in-place recycling mixture, the improvement of material performances should be focused on, especially the moisture susceptibility. In the research, the emulsified asphalt cold in-place recycling mixtures were acceptably used as the middle layer of maintenance pavement structure. The reliable discussions were summarized based on coring samples collected from real-life road sections. The case can provide guidance and reference for similar engineering applications.

Study on performance deterioration regularity of hot regenerated asphalt mixture under multiple aging factors

Several elements, including ultraviolet light, humidity, temperature, vehicle load, etc., have an impact on the asphalt pavement concurrently during the road service process, gradually diminishing the road’s service level. The self-created Life Cycle Analysis System (LCAS) was employed to simulate the cumulative effects of multiple aging components during the service process. The freeze–thaw splitting test, dynamic creep test, and notched semi-circular bending test were conducted after the hot recycled and the fresh asphalt mixtures were subjected to varying durations of simulated aging. The results indicate that initially, the road performance of the hot recycled asphalt mixture is comparable to the fresh asphalt mixture. However, the fresh asphalt mixture outperforms the hot recycled mixture in all but water stability over time. The attenuation degree of the flow number (FN) differs by 22.5% between the two kinds of mixtures, while the fracture energy differs by 53.3%. The performance of the hot recycled asphalt mixture degrades much more rapidly than that of the fresh asphalt mixture. The LCAS method can well simulate the actual service environment of asphalt pavement constructed with RAP materials and provide help for the performance evaluation of RAP pavement in road engineering and subsequent related research.

Moisture Damage Characterization of Rubber-Modified Asphalt Mixture Containing Waste Steel Slag under Multiple Freeze–Thaw Cycles

Recycling waste materials has become popular in the pavement industry because of its potential for significant environmental benefits, conservation of natural resources, and sustainability. This study investigated the feasibility of simultaneously recycling waste steel slag and tire rubber in bituminous pavements and analyze the moisture susceptibility of asphalt mixtures made of these solid wastes. The physical and chemical characteristics of the aggregates and the adhesive behavior of the aggregate–bitumen system were explored to determine their impact on moisture sensitivity. Accordingly, two different methods, freeze–thaw splitting test and fracture energy tests, were employed to assess the moisture stability of mixes in a multiple freeze–thaw environment. The microstructure of the interface between the aggregate and bitumen was investigated, and the long-term moisture damage process of the mixes was clarified and verified. The results indicate that the natural hyperalkalinity and porous structure of the steel slag have a favorable effect on the adhesion performance. Cohesive failure was found to be the primary mode of failure of loose asphalt mixtures in a multiple freeze–thaw environment. We tentatively propose that the adhesion energy loss is a secondary failure mode of the loose asphalt mixtures. The addition of 100% steel slag and asphalt rubber had the greatest impact on improving the long-term moisture resistance of the asphalt mixtures. The present work is beneficial for the practical application of waste tire rubber and steel slag in highway engineering.

Experimental investigation on the performance of the asphalt mixture with ceramic fiber

Ceramic fiber (CF) as a kind of industrial waste is widely used for the sake of waste utilization and environmental protection. In this study, three kinds of industrial waste ceramic fibers, CF-A (NC1260 spinning CF), CF-B (NC1260 blowing CF), and CF-C (NC1430 spinning CF), were used to develop a ceramic fiber modified asphalt mixture (CFMAM) to meet the increasing demand for asphalt pavement construction. Firstly, the optimum asphalt content of the CFMAM was determined by the mix design with the 0.3%wt fiber content. Secondly, the high-temperature stability and low-temperature cracking resistance of CFMAM were evaluated by rutting test, beam bending test and splitting test, respectively. The results showed that the CF-A and CF-C had the same positive influences on the mechanical properties and pavement performance of asphalt mixture, while the CF-B exhibited fewer positive influences. Then, the moisture susceptibility performance was tested by immersed Marshall test and freeze-thaw splitting test. The CFMAM with CF-A showed better properties than that of CF-B, CF-C, and virgin asphalt binder. Finally, the scanning electron microscopy (SEM) experiment was conducted to analyze the adsorption effect of fiber on asphalt mortar and the reinforcement effect on the mixture. It was observed that the fiber and asphalt had good wettability and dispersibility in the mixture.

Overall feasibility assessment of polyester polyurethane concrete used as steel bridge deck pavement

Traditional pavement materials used in the orthotropic steel bridge deck suffer from various pavement distresses and thus reduce the service life of the steel bridge. Therefore, this study proposed a novel engineered material named polyester polyurethane concrete (PPUC) for the steel bridge deck pavement. Indoor laboratory experiments and numerical comparison analysis were conducted to comprehensively assess the feasibility of PPUC as the steel bridge deck pavement and ordinary Portland cement (OPC), guss asphalt concrete (GAC), asphalt mastic concrete (SMAC) and epoxy asphalt concrete (EAC) were used as references compared with PPUC. After the specimens of PPUC were prepared by mixing polyester polyurethane binder (PPUB) and aggregate with the binder-aggregate ratio of 15%, the specimens were subjected to compressive test, splitting tensile test, flexural tensile strength test, wheel tracking test, low-temperature cracking test, freeze-thaw splitting test, shear test and pull-out test. The mechanical performance comparison of different pavement structures with different materials was also analyzed using finite element analysis method. Results show that PPUC presents higher mechanical properties (compressive, tensile and flexural strength) compared to OPC, and it has good durability properties compared to SMAC, GAC, and EAC, such as high temperature stability, low temperature cracking resistance and water stability. In addition, PPUC has strong adhesive property with steel deck and does not change significantly with temperature changes. The finite element simulation results show that the maximum tensile strength and maximum compressive strength of PPUC in the single-layer structure are 0.51 MPa and 3.52 MPa respectively, which are much smaller than the experimental values and those of other materials. The maximum tensile strength and maximum shear strength of PPUC in the PPUC + SMAC composite structure are 0.232 MPa and 0.148 MPa respectively, which are also much smaller than the experimental values and those of other structures. The mechanical performance comparison results indicate that PPUC pavement structure can improve the overall stiffness of the steel bridge deck and protect the wear layer. These results support that the PPUC has a promising application for the steel bridge deck pavement.

Performance and assessment of modified cold recycled asphalt emulsion mixture

In this study, the comprehensive performance of cold mix asphalt (CMA) is evaluated by seven laboratory test methods, namely the Hveem cohesion test, water immersion splitting test, freeze–thaw splitting test, indirect tensile fatigue test, semi-circular bending (SCB) test, dynamic modulus test, and rutting test. The CMA is modified using the regenerant (RE), Buton rock asphalt (BRA), and styrene–butadiene rubber (SBR) latex. In addition, we have proposed an evaluation model based on the grey target theory to quantitatively assess the effects of the modification approaches. The results show that the CMA modified with 8% RE has the best comprehensive property. RE is a potential modifier and reduces the content of emulsified asphalt for CMA, which can significantly improve the cohesion, moisture susceptibility, dynamic mechanical properties, and durability of CMA. Additionally, the grey target theory is an effective method to evaluate the comprehensive performance of CMA quantitatively.

Performance and overall evaluation of nano-alumina-modified asphalt mixture

Abstract The performance of asphalt mixture affects the service of pavement. Nano-alumina was employed as asphalt mixture modification to improve pavement performances. Properties of asphalt mixtures including high-temperature properties, low-temperature properties, water stability properties, and fatigue properties were investigated through rutting tests, dynamic creep tests, low-temperature bending tests, indirect tensile tests, Marshall stability tests, freeze-thaw splitting tests, and indirect tensile fatigue tests. Considering the various performance of nano-alumina-modified asphalt mixture, the optimization decision was made based on 21 sets of performance data, and the optimal dosage of nano-alumina was further clarified. The results demonstrate that nano-alumina improved all properties of asphalt mixtures, except for low-temperature properties. The decision revealed that the performance of the modified asphalt mixture was the most balanced when the content of nano-alumina is 9%. When the optimal dosage of nano-alumina was 9%, the dynamic stability of the asphalt mixture at 60°C was increased by 34.2%, the cumulative permanent strain was reduced by 36.5–49.5%, the water stability performance was improved by 8.3–19.5%, and the fatigue performance was improved by 3.8–7.2%. However, the low-temperature flexural tensile strain was reduced by 2.1% but still meets the specification requirements. Nano-alumina can be used to modify asphalt pavement materials in high-temperature and rainy areas.

Optimization of surface free energy parameters for asphalt binder-aggregate system based on RBF neural network model

Asphalt pavement is subject to water damage frequently, which reduces the level of service that it provides and contributes to many road diseases. The surface free energy (SFE) theory has proven to be a trustworthy approach to assess water damage in asphalt mixtures. The goal of this investigation was to optimize the SFE parameters of asphalt binder-aggregate systems using an RBF neural network model. In this research, the SFE parameters of asphalt binder-aggregate systems were calculated firstly. Then, the modified boiling water test and the immersion Marshall test, as well as the freeze–thaw splitting test were then used to assess the asphalt mixtures’ adhesive properties and water stability. Thereafter, the comprehensive analysis method of entropy weight was used to conduct a thorough evaluation of the asphalt mixtures’ resistance to water damage. Next, the comprehensive evaluation index, Wi, of the asphalt mixtures’ resistance to water damage was used as the output layer of the RBF neural network model to optimize the SFE parameters. Finally, the feasibility of the optimized the SFE parameters using RBF neural network model was verified by establishing the connection between the optimized SFE parameters and the asphalt mixtures’ resistance to water damage by the entropy weight comprehensive analysis method. The results showed that among the SFE parameters of asphalt binder-aggregate systems optimized using the RBF neural network model, the Lewis base component and the Lifshitz nonpolar component of the aggregate played a dominant role in the ability to resist water damage, followed by the VDW adhesion work and the VDW de-bonding work formed by van der Waals forces. Furthermore, the asphalt binder-aggregate system composed of limestone had the best adhesion properties among all aggregates.

Comprehensive Performances of Hybrid-Modified Asphalt Mixtures with Nano-ZnO and Styrene-Butadiene-Styrene (SBS) Modifiers

An effort was made to improve the separation issue of styrene-butadiene-styrene modifiers in styrene-butadiene-styrene-modified asphalt binders and to further enhance their performance by adding nano-ZnO to the styrene-butadiene-styrene-modified asphalt binder to prepare compound modified binder. First, the optimum nano-ZnO dosage was determined based on conventional tests, i.e., penetration, ring and ball softening point, and ductility at a fixed styrene-butadiene-styrene dosage; then, dynamic shear rheometer, bending beam rheometer, and fluorescence microscopy tests were conducted to evaluate the properties of the nano-ZnO/styrene-butadiene-styrene hybrid-modified asphalt binders. Finally, the rutting test, trabecular bending test, submerged Marshall test, and the freeze-thaw splitting test was conducted to evaluate the properties of the asphalt mixtures produced with the hybrid-modified binders. The main results showed that: the optimum nano-ZnO dosage, which was 4% by weight to the asphalt binder, and an improvement of the separation issue of the styrene-butadiene-styrene, and the flexural tensile strength and the maximum bending tensile strain of the hybrid-modified asphalt mixtures increased by 13.4% and 16.4%, respectively. In addition, the residual stability and the tensile strength ratio also increased by 4.3% and 4.8%, respectively, compared to the styrene-butadiene-styrene-modified asphalt mixtures. In conclusion, nano-ZnO improves the low-temperature and water stability performances of the styrene-butadiene-styrene-modified asphalt mixture.

Influence of salt dissolution on durable performance of asphalt and Self-ice-melting asphalt mixture

At present, research on the influence of salt dissolution on pavement performance of self-ice-melting asphalt mixture is scarce. Based on laboratory research, this study aims to investigate the influence of salt dissolution on the durable performance of asphalt and self-ice-melting asphalt mixture. Firstly, SBS modified asphalt binder containing Mafilon (MFL) and self-ice-melting asphalt mixture (SMA-13) containing MFL and rubber particles (RP) were subjected to dry-wet cycles for different cycles. Then the influence of salt dissolution on the properties of asphalt and its mechanism were studied by physical properties test, scanning electron microscopy (SEM) test, energy dispersive spectrometer (EDS) test and Fourier transform infrared spectroscopy (FTIR) test. Finally, the influence of salt dissolution degree on long-term pavement performance of asphalt mixture was evaluated by freeze–thaw splitting test, rutting test, and trabecular bending test. The experimental results showed that with the increase in the number of dry-wet cycles, the penetration and ductility of asphalt decrease, while the softening point increases. The greater the content of MFL and the increasing number of dry-wet cycles, the greater the variation is. The effect of salt dissolution on asphalt properties can be attributed to salt aging and physical effect, without chemical reactions occurring. In addition, the road performance test of asphalt mixture indicated that the decrease of water stability, high-temperature performance, and low-temperature performance of self-ice-melting asphalt mixture increases firstly and then tends to be gentle as the increase of salt dissolution. What’s more, the water stability is deeply influenced by salt dissolution.

Investigation of Long-Term Performance and Deicing Longevity Prediction of Self-Ice-Melting Asphalt Pavement.

Based on laboratory tests, the objective of this study is to assess long-term road performance and to predict deicing longevity of self-ice-melting asphalt pavements containing salt-storage materials. Dry–wet cycles and freeze–thaw cycles were used to treat the specimens at different durations. The long-term road performance of self-ice-melting asphalt mixtures was evaluated by freeze–thaw splitting tests, high-temperature rutting tests, and low-temperature beam bending tests. In addition, the influences of coefficients of void ratio, temperature, vehicle load, crack, and Mafilon (MFL) content on salt precipitation were quantified by conductivity tests, and single consumption of snow and ice melt was quantified by total dissolved solids (TDS) tests. The results show that the long-term water stability, long-term high-temperature stability, and long-term low-temperature crack resistance of self-ice-melting asphalt pavements tended to decrease as the number of dry–wet cycles and freeze–thaw cycles increased. Freeze–thaw cycles exerted deeper influences on the deterioration of road performance than dry–wet cycles, especially on water stability. With increased void ratio and temperature, salt precipitation was accelerated by 1.1 times and 1.5~1.8 times, respectively. Under vehicle loads and cracks, salt precipitation was accelerated by 1.5 times and 1.65 times, respectively. With decreased MFL content, salt precipitation slowed down by 0.54 times. Finally, based on the proportion of each factor relative to the whole life cycle of the pavement, a dicing longevity prediction model was established considering the above factors.

Effect of Hot Mixing Duration on Blending, Performance, and Environmental Impact of Central Plant Recycled Asphalt Mixture

When using a high concentration of reclaimed asphalt pavement (RAP) in a recycled hot-mix asphalt mixture (RHMA), the degree of blending of the reclaimed asphalt binder significantly affects the performance of the RHMA. Hence, it is essential to know the degree of blending of the RAP and its effect on the performance and the environmental impact of RHMA in order to determine the optimal mixing duration. To this end, the dispersion of reclaimed asphalt was observed using artificial RAP and the image analysis method, and the blending of reclaimed asphalt in RHMA with different mixing durations was also evaluated using physical properties tests, a rheometer test, a Fourier-transform infrared spectroscopy (FTIR) test, a gel permeation chromatography (GPC) test, and an atomic force microscope (AFM) test. The performance of RHMA with the different mixing durations in the plant and in the laboratory was tested using a Marshall stability test, rutting resistance test, freeze–thaw splitting test, and low-temperature bending beam test. In addition, the environmental impact of RHMA at different mixing durations was evaluated, and the optimal mixing duration was determined. The results showed that the mixing duration had a significant influence on the dispersion and blending of reclaimed asphalt in RHMA. The longer the mixing duration was, the higher the dispersion and the degree of blending of the reclaimed asphalt in the RHMA were. With the increase in the mixing duration, the properties, chemical composition, and micromorphology of the blended asphalt binder tended to become similar to those of reclaimed asphalt. The performance of RHMA was improved with the increase in mixing duration; however, the energy consumption and CO2 emissions for the RHMA increase significantly with the increase in mixing time. The recommended optimal mixing durations in the mixing plant and in the laboratory were found to be 60 s and 90 s, respectively, considering the environmental impact, the RHMA production efficiency, and the performance of the RHMA.

The Properties of Micro Carbon Fiber Composite Modified High-Viscosity Asphalts and Mixtures.

In order to produce a high-viscosity asphalt and mixtures that can be used for ultra-thin overlays, high contents of Styrene–butadiene–styrene (SBS, 5%, 6%, 7%), styrene butadiene rubber (SBR, 1%, 2%, 3%) and micro carbon fiber (MCF, 0.8%) were used to modify conventional asphalt to prepare high-viscosity modified asphalt suitable for this purpose. The performance of the modified asphalts was evaluated by conventional index, kinematic viscosity, dynamic shear rheological test (DSR), multiple stress creep recovery test (MSCR), and bending beam rheometer test (BBR). The road performance of the modified asphalt mixtures was evaluated by high-temperature rutting, low-temperature bending, freeze-thaw splitting, fatigue, speckle, anti-skid, and water seepage tests. The results show that increasing the content of SBS can improve the high-temperature deformation resistance, low-temperature failure strain, kinematic viscosity, and viscosity toughness of modified asphalt, and the optimum content of SBS was 6%. SBR can improve the high-temperature performance, kinematic viscosity, and water damage resistance of modified asphalt, and the optimum dosage was 2%. Compared with 5% SBS-modified asphalt mixture, the dynamic stability, low-temperature failure strain, and freeze-thaw splitting strength ratio of 6% SBS + 0.8% MCF composite-modified asphalt mixture were increased by 48.7%, 24.7%, and 5.2% respectively. Compared with the 5% SBS-modified asphalt, the same characteristics of the 2% SBR + 5% SBS + 0.8% MCF composite-modified asphalt increased by 127.1%, 13.5%, and 5.5%, respectively. Compared with 5% SBS-modified asphalt, the fatigue performance of 6% SBS + 0.8% MCF-modified asphalt was improved by 32.2%. The kinematic viscosity of 6% SBS + 0.8% MCF and 5% SBS + 0.8% MCF + 2% SBR modified asphalt met the performance requirements of high-viscosity asphalt and had excellent road performance. It can be applied to ultra-thin overlays to optimize its adhesion with the original pavement.

An Active Anti-Aging Technology for Asphalt Mixture

For aged asphalt, as the content of light component gets smaller with the passing of time, the performance of the asphalt mixture would degrade accordingly. This study aims to develop an anti-aging material that can supplement light component to asphalt pavement during its service process, thereby suppressing the aging of asphalt and prolong the service life of the road surface. At first, this study carried out four-component separation test to measure the loss mass of light component; then in the experiment, the oil shale wastes were impregnated in light component to determine its adsorption capacity to the light component. After that, according to the loss of asphalt light component after long-term aging and the adsorption ratio of anti-aging materials with different particle sizes for light component, the amount of anti-aging material to be added was determined; moreover, via rutting test, beam bending test, and freeze-thaw splitting test, the high-temperature stability, low-temperature crack resistance, and water stability of the asphalt mixture modified by the proposed anti-aging material had been verified, and the results proved that the proposed anti-aging material can well suppress the aging of asphalt mixture.

Performance analysis of graphene modified asphalt and pavement performance of SMA mixture.

The graphene modified asphalt used in this study was prepared based on a highway project in Gansu Province. In this paper, the high temperature rutting resistance, low temperature cracking resistance, and water stability of SMA-13 asphalt mixture with asphalt (AH-70), SBS modified asphalt and graphene rubber composite modified asphalt were tested and analyzed comparatively by the rutting test, Schellenberg binder drainage test, Cantabro test, freeze-thaw splitting test, and beam bending test. The results showed that the graphene modifier improved the asphalt’s ductility and softening point significantly, and 0.4g graphene content was the threshold and its corresponding mixture performance index. In the other tests under the same conditions, the high temperature and water stability of SMA-13 mixtures of graphene rubber modified asphalt were the best, followed by SBS modified asphalt mixture, and matrix asphalt mixture. Compared with wood fiber, graphene modifier had no significant effect on SMA-13 mixtures’ low temperature performance. The use of graphene modifiers can enhance the adhesion between asphalt and aggregate and its asphalt has good consistency and viscosity. When compared with matrix asphalt and SBS modified SMA-13 mixtures, the water and high temperature stability of graphene modified asphalt mixture is better.

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.

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.