Steel Slag Asphalt Mixture Research Articles

Research on microwave heating performance of modified steel slag asphalt mixture

Aiming at the change law of the flexural and tensile strength of the modified steel slag asphalt mixture during microwave heating, the results of this paper are as follows: the microwave heating process can achieve the recovery of the flexural and tensile properties of the modified steel slag asphalt mixture. The number of point bending failure tests continues to increase, and the recovery rate of bending and tensile properties of beams made of modified steel slag asphalt mixture will slowly decrease until the test piece is completely destroyed. The flexural and tensile strength of beams made by microwave heating asphalt mixture cannot be fully recovered, but different asphalt mixtures have different recovery effects. Compared with the ordinary basalt asphalt mixture, the steel slag asphalt mixture before modification has the same bending and tensile repair effect after microwave heating, while the modified steel slag asphalt mixture has the first bending and tensile repair effect after microwave heating increased by 23%.

Improved microwave heating uniformity and self-healing properties of steel slag asphalt containing ferrite filler

As a preventive maintenance approach, microwave self-healing is an effective method to repair small pavement cracks at early stage and reduce maintenance costs. However, the difference in microwave absorption ability of asphalt pavement engenders the common problem of uneven heating. This study aims to evaluate the feasibility of applying ferrite to replace partial limestone filler in order to enhance the microwave heating uniformity and self-healing properties of steel slag asphalt mixtures. The morphological features and microwave absorption properties of ferrite were firstly characterized. The addition of ferrite content was estimated via rheological tests including Bending Beam Rheometer and Dynamic Shear Rheometer. Finally, the semi-circular bending and thermal analysis tests were performed to determine the optimal ferrite content. Results demonstrated that ferrite displayed excellent microwave absorption properties; nevertheless, excessive use of ferrite may weaken the rheological behavior of asphalt mortar at low temperatures. Moreover, the addition of ferrite can significantly promote the microwave heating uniformity and heating efficiency level of specimens, while slightly increase the self-healing ratio. Overall, replacing 20% limestone filler with ferrite in volume is a promising solution to properly enhance a uniform microwave heating of steel slag asphalt mixtures.

Investigation of Permanent Deformation Behavior of Steel Slag Asphalt Mixture under Indoor Simulation

Previous studies have indicated that steel slag can be used as a substitute for natural aggregates in asphalt mixture, while little attention has been paid to systematic investigation of the influences of various external environmental factors on deformation resistance of steel slag asphalt mixture. In order to understand the service behavior of steel slag asphalt mixture, its permanent deformation under different condition was investigated based on an indoor simulation test. The chemical composition, microscopic structure, surface texture, and volume stability of steel slag were firstly characterized. The uniaxial repeated loading test and standard wheel‐tracking test were applied to evaluate the effect of temperature, stress levels, and water damage on the permanent deformation of AC‐16 and AC‐20 steel slag asphalt mixtures. The results indicate that a higher content of alkaline oxide and high‐grade texture index existing in steel slag contribute to its strong absorptivity and adhesion of asphalt. The steel slag demonstrates fine volume stability due to its lower free‐CaO (f‐CaO) content, autoclave chalked ratio, and immersion expansion ratio. The permanent deformation of steel slag asphalt mixtures increases rapidly under higher stress and temperatures in contrast to lower increment at lower stress and temperatures. Asphalt mixtures at higher stress and higher temperatures and water condition exhibit larger rutting deformation and inferior rutting resistance. AC‐16 steel slag asphalt mixture has superior resistance to permanent deformation than AC‐20 asphalt mixture. Rutting factors show different degrees of impact in a decreasing order of temperature, water damage, and stress levels. The findings have significant implications for providing a theoretical basis for reusing steel slag in pavement construction and facilitating engineering application of steel slag asphalt mixture.

Analysis on the Properties of Modified Steel Slag Asphalt Mixture

steel slag property reform is the main form of comprehensive utilization of industrial waste resources. Therefore, this paper combines the theory of steel slag surface modification technology, focusing on the expansion characteristics, aggregate effect and other aspects, to explore the performance of modified steel slag asphalt mixture, in order to achieve clear technical points, to achieve the purpose of comprehensive development and application of social resources.

Effect of Dry–Wet and Freeze–Thaw Repeated Cycles on Water Resistance of Steel Slag Asphalt Mixture

As an attractive substitute of natural aggregate for asphalt mixture, steel slag raises many concerns on the water resistance of steel slag asphalt mixture in frozen and wet areas, due to the special interaction between steel slag and asphalt. This study aims to investigate the deterioration process of water resistance for asphalt mixture with different steel slag contents in dry–wet and freeze–thaw cycles environments. The Marshall immersion test and indirect tensile test were conducted, and the residual stability and tensile strength ratio (TSR) were measured to characterize the water resistance of the steel slag asphalt mixture. Furthermore, dry–wet and freeze–thaw repeated cycling conditions were designed to simulate the effect of actual environments on the long-term water resistance of asphalt pavement. Finally, the microstructures of the aggregate–asphalt interface area were observed, and the enhancement mechanism of the steel slag replacement in asphalt mixture was revealed. Results show that steel slag asphalt mixture exhibits significant resistance to water damage. With the increase in dry–wet or freeze–thaw repeated cycles, the water resistance of steel slag asphalt mixture rapidly deteriorates first and then tends to be stable, and there is a limit state of water damage. In dry–wet repeated cycles condition, the asphalt mixture with 50% steel slag content has a better water resistance, while the asphalt mixture with 100% steel slag content has a better water resistance under freeze–thaw repeated cycles condition. The interface phase structure of steel slag asphalt mixture is stable and dense, where the asphalt mortar evenly and tightly wraps the steel slag and forms a certain penetration depth. The enhancement mechanism of steel slag with asphalt mainly includes the physical anchoring effect and the chemical adhesion effect.

Design and prospect of new pavement materials for smart road

Considering the development of conventional engineering materials, the research on new modern materials and the increasing demand for road infrastructure construction, significant changes regarding both the road fundamental properties and functional positioning have been taking place at an increasing pace. The roads have evolved from early structures meeting basic traffic needs to important assets with well-defined economic and environmental characteristics. Since the beginning of the 21st century, the need for smart and safe travel has steadily created new requirements for road infrastructure. The rapid development of material science and interdisciplinary research has provided viable and technical support for the design and construction of various types of new pavements, thus promoting the continuous expansion within the research field of pavement materials. Therefore, this research introduces and analyzes the technical principles, design, development, and challenges related to new pavement materials characterized by self-capture energy, self-luminescence, self-regulation, and self-healing functions, providing a reference for the future research direction. The main objective of piezoelectric self-powering pavement is to design the structure and optimize the performance of self-powering devices, and apply this technique in road engineering. A series of studies on mechanical modeling, laboratory verification and engineering application of self-powering devices show that the energy harvesting effect of embedded piezoelectric self-powering devices made of block or multilayer piezoelectric materials is considerable, and the piezoelectric self-powering pavement has a broad prospect. Thermoelectric pavement is a new type of pavement, which uses the Seebeck effect of thermoelectric materials to collect excess energy of asphalt pavement and realize green conversion of pavement energy. Meanwhile, it can effectively reduce the temperature of pavement and prolong the service life of road. The composition includes three main parts: Thermoelectric conversion device, hot end and cold end. A new type of thermoelectric asphalt pavement structure is studied in this paper. Results indicate that the power generation 0.564 V of single specimen has good application potential via monitoring the generation voltage of thermoelectric pavement in different seasons. The research of self-luminous pavement mainly focuses on the design and optimization of pavement luminescent materials. The self-luminous paste materials are prepared by adding long afterglow rare earth luminescent powder and glass beads reflective powder into cement materials. The luminescence properties are characterized by afterglow decay time and fluorescence chromatography. The optimum range of particle size of self-luminous pavement materials and reflective powder is determined, which can provide reference for the further research. As for the self-regulation pavement material, the thermogravimetric and differential scanning calorimetry tests are conducted to study the thermal stability and phase transition characteristics of PEG. The results show that PEG has excellent thermal stability; the average molecular weight ranging from 4000 to 10000 of PEG have relatively high phase change heat storage capacity and similar phase change temperature. Based on asphalt properties, the optimum average molecular weight for asphalt pavements can be further decided. Conductive asphalt mixtures are used in this study to investigate the self-healing properties under microwave irradiation. The microstructure and element distribution of steel slag are characterized through scanning electron microscope. The healing level and the optimum content of steel slag are evaluated according to the recovery strength level of steel slag asphalt mixture and the surface temperature distribution of specimen under microwave radiation. Results show that steel slag is an excellent microwave absorbing material, which can effectively improve the healing level of the mixture, meanwhile, there is an optimal addition amount of the steel slag. The significance of innovative material design is not only related to expanding the pavement functions, but also to bolstering the structural technology design concepts of modern road engineering as well as to offering new technologies for the related industry sector.

Utilization of steel slags to produce thermal conductive asphalt concretes for snow melting pavements

This study focuses on the thermal conductivity of steel slag asphalt mixtures. The initial aim of this study was to verify the feasibility of adding steel slag to asphalt mixtures as a thermal aggregate to increase the thermal conductivity for electrical-thermal snow melting. The thermal conductivity of different rock aggregates and steel slags were firstly tested, before the surface temperatures of different-sized particles of the target steel slag was measured. In addition, the thermal conductivity and engineering performances of asphalt mixtures with different steel slags contents were measured. Experiment results indicate that diabase and hot-stuffy steel slag possesses higher thermal conductivity, and that particles of sizes 9.5–13.2, 1.18–2.36 and 0.3–0.6 mm are the most effective sizes. The thermal conductivities of the asphalt mixtures firstly increased, before decreasing with increasing steel slag replacement, and the thermal conductivity reached a peak for a steel slag volume replacement of 6%. All of the steel slag asphalt mixtures meet the required engineering performance, and the steel slag asphalt mixtures played a positive role in the snow melting process on an electrical-thermal pavement system, compared with ordinary asphalt mixtures.

The Interfacial Adhesion Performance and Mechanism of a Modified Asphalt-Steel Slag Aggregate.

The interfacial adhesion between asphalt and steel slag aggregate is a decisive factor in the formation of an asphalt–steel slag mixture and significantly affects the quality stability of steel slag–asphalt mixtures. In this study, the adhesion between an asphalt and steel slag aggregate, the interfacial microstructure, the adsorption and desorption characteristics, and chemical reactions were, respectively, explored by a PosiTestAT–A adhesion puller, a scanning electron microscope, a net adsorption test, an infrared spectrometer, and a dynamic shear rheometer. The mechanism of adhesion between the asphalt and steel slag aggregate was analyzed from the perspectives of physical adsorption and chemical reactions. The results showed that different factors had different effects on the adhesion of asphalt–steel slag aggregate interface. The freeze–thaw cycle and steel slag aggregate particle size had significant effects on interfacial adhesion, while the asphalt heating temperature, water bath time, and stirring time had relatively weak effects on interfacial adhesion. Compared to a limestone aggregate, the steel slag–asphalt mixture had greater adhesion and better adhesion performance because the pits and textures on the surface of the steel slag aggregate produced a skeleton–like effect that strengthened the phase strength of the asphalt–slag aggregate interface, thereby improving the adhesion and increasing the physical adsorption between the asphalt and steel slag aggregate. In addition, due to the N–H stretching vibrations of the amines and amides, as well as SiO–H stretching vibrations, a chemical reaction occurred between the asphalt and steel slag aggregate, thus improving the adhesion performance between the asphalt and steel slag. Based on the shape of the adsorption isotherm, it was determined that the adsorption type was multi–molecular layer adsorption, indicating that the adhesion between the asphalt and steel slag mainly involved physical adsorption.

Study on Recycling of Steel Slags Used as Coarse and Fine Aggregates in Induction Healing Asphalt Concretes.

Steel slag, a by-product of steelmaking, imposes lots of negative impacts on the environment. For alleviating negative impacts, more and more experiments have been carried out to explore the application possibility of steel slag. The purpose of this study is to explore the feasibility of steel slag being applied in induction healing asphalt concretes to replace coarse and fine aggregate. Surface texture and pore sizes of steel slag were firstly tested, and then steel slag and basalt asphalt mixtures modified with steel fibers were prepared. Moisture susceptibility, dynamic stability, mechanical property, thermal property, induction heating speed, natural cooling speed and healing property of the asphalt mixtures were evaluated. Results showed that steel slags had more obvious holes in the surface while the surface area is much larger than that of basalt. Furthermore, steel fibers and steel slag both have dynamic stability, and steel fibers contribute to increased moisture resistance while steel slag is not. Steel slag asphalt concrete showed better mechanical property and better capacity to store heating. Steel slag asphalt mixtures had a similar heating speed to basalt asphalt mixtures but a significantly slower cooling rate. Finally, the induction healing test and CT scanning test demonstrated that steel slag asphalt mixtures had a similar healing ability to basalt asphalt mixtures. It can be concluded that steel slags have the potential to replace the natural aggregates to be applied in induction heating self-healing asphalt concretes.

Study of the long-term water stability of asphalt mixtures containing steel slag aggregate

This article aims to elucidate the long-term water stability of a steel slag asphalt mixture. Both chemical composition and physical morphology of the steel slag were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), the Vickers hardness test and mercury injection testing. Methods of testing wet-dry (W–D) cycles and freeze-thaw (F–T) cycles were designed, and corresponding indices were proposed. The immersion rutting test was conducted to explore the variation in rutting depth, and consequently, the long-term dynamic water coefficient Kl was proposed to analyze the resistance to dynamic water flushing. A regression model was used to analyze the relationship between steel slag content and long-term water stability. Finally, the long-term corrosion characteristics of the steel slag asphalt mixture were analyzed by SEM. The results show that the addition of steel slag can improve the long-term water stability of the asphalt mixture. The water stability of the steel slag asphalt mixture declines with increasing W–D and F–T cycles. The degradation trend becomes gentle after 6 W–D cycles. The attenuation of the water stability of the mixture slows after 15 F–T cycles. The long-term water stability of the steel slag asphalt mixture was evaluated by comparing the residual stability after 6 W–D cycles (MS6) and the tensile strength ratio (TSR) of the steel slag asphalt mixture after 15 F–T cycles (TSR15). The Kl value of the steel slag asphalt mixture first increases and then decreases with increasing steel slag content, and the best effect in terms of long-term dynamic water corrosion resistance is observed for a 30% steel slag asphalt mixture. The SEM results show that, for steel slag asphalt mixture water damage, the steel slag hydrates and produces microcracking on the surface.

Properties of a Steel Slag-Permeable Asphalt Mixture and the Reaction of the Steel Slag-Asphalt Interface.

Steel slag is an industrial solid waste with the largest output in the world. It has the characteristics of wear resistance, good particle shape, large porosity, etc. At the same time, it has good adhesion characteristics with asphalt. If steel slag is used in asphalt pavement, it not only solves the problem of insufficient quality aggregates in asphalt concrete, but can also give full play to the high hardness and high wear resistance of steel slag to improve the performance of asphalt pavement. In this study, a steel slag aggregate was mixed with road petroleum asphalt to prepare a permeable steel slag–asphalt mixture, which was then compared with the permeable limestone–asphalt mixture. According to the Technical Regulations for Permeable Asphalt Pavement (CJJT 190-2012), the permeability, water stability, and Marshall stability of the prepared asphalt mixtures were tested and analyzed. In addition, the high-temperature stability and expansibility were analyzed according to the Experimental Regulations for Highway Engineering Asphalt and Asphalt Mixture (JTG E20-2011). The chemical composition of the steel slag was tested and analyzed by X-ray fluorescence spectrometer (XRF). The mineral composition of the steel slag was tested and analyzed by X-ray diffractometer (XRD). The asphalt was analyzed by Fourier transform infrared spectroscopy (FTIR). The results show that the steel slag asphalt permeable mixture had good permeability, water stability, and Marshall stability, as well as good high-temperature stability and a low expansion rate. The main mineral composition was ferroferric oxide, the RO phase (RO phase is a broad solid solution formed by melting FeO, MgO, and other divalent metal oxides such as MnO), dicalcium silicate, and tricalcium silicate. In the main chemical composition of steel slag, there was no chemical reaction between aluminum oxide, calcium oxide, silicon dioxide, and asphalt, while ferric oxide chemically reacted with asphalt and formed new organosilicon compounds. The main mineral composition of the steel slag (i.e., triiron tetroxide, dicalcium silicate, and tricalcium silicate) reacted chemically with the asphalt and produced new substances. There was no chemical reaction between the RO phase and asphalt.

Study on Preparation and Performance of Steel Slag Asphalt Mixture Based on Steel Slag Aggregate

The comprehensive utilization of steel slag has always been a worldwide problem. Under the background of vigorous development of highways in China, the application technology of steel slag in asphalt concrete will make the steel slag resources hopefully get a large number of reasonable utilization. Based on the application of steel slag in asphalt concrete, the basic physical and chemical properties of different types of steel slag were investigated. The blast furnace slag was used as the aggregate to prepare the asphalt mixture. The mixture was tested by research and test. The uniaxial compression test and the indirect tensile test were used to evaluate the low temperature crack resistance and fatigue resistance. The test results show that the surface texture of steel slag is rough and the embedding effect is good, which is beneficial to enhance the adhesion with asphalt and improve the shear resistance. The steel slag asphalt mixture has good low temperature deformation ability and small expansion ratio, which can be paved to meet the driving conditions. Required asphalt concrete pavement.

Nano-clay and styrene-butadiene-styrene modified bitumen for improvement of rutting performance in asphalt mixtures containing steel slag aggregates

Nanoparticles have exhibited a promising potential in enhancing the bituminous materials’ performance. As a cost-effective material, hot mix asphalt (HMA) has been employed in pavement structure for a long time. Their viscoelasticity however results in various modes of failure under different temperature profiles and loading stress. Rutting of asphalt pavements is considered as the most prominent distress factor under almost all climate conditions. Moreover, steel slag has been employed for improvement of asphalt mixture properties as it exhibits excellent physical features. In this content the aim of the present research is to analyze improving effects of nano clay and styrene-butadiene-styrene (SBS) on the rutting resistance of modified steel slag asphalt mixture (SSAM). Various tests were employed to investigate the asphalt binder properties and the rheological characteristics of modified bitumen among which penetration grade, softening point, ductility and dynamic shear rheometer (DSR) can be mentioned. Marshal Test was applied to examine the optimum bitumen content in conventional and modified asphalt mixture. The rutting resistance against was then evaluated through two tests: repeated load axial (RLA) test and wheel track test. The results indicated respective improvement of toughness and viscosity by an average of 25% and 101% upon addition of nano-polymer which enhanced the bitumen rheological characteristics while reducing the penetration grade. The asphalt rutting resistance and rutting depth exhibited some improvements as well.

Expansion inhibition of steel slag in asphalt mixture by a surface water isolation structure

To inhibit volume expansion of steel slag and improve pavement performance of steel slag asphalt mixture, a surface water isolation structure was proposed by employing three surface treatment approaches. Properties of the surface modified steel slag were tested including water absorption, expansion ratio, crush value and adhesion. X-ray diffraction, X-ray fluorescence and scanning electron microscope were used to analyse the physical and chemical properties of steel slag. Results showed that three approaches could reduce the volume expansion of the surface modified steel slags at a certain extent, and the silicone waterproof agent had the best treatment effect, with expansion ratio reduced by 34%. Subsequently, three asphalt mixtures (surface modified steel slag, original steel slag and basalt) were prepared. Rutting test, low-temperature bending test, mixture immersion expansion test, Marshall test and freeze–thaw split test were achieved to determine their pavement performances. Compared with control groups, the high-temperature performance and water stability of the asphalt mixture composed of surface modified steel slag had significant enhancement. The dynamic stability increased by 20% and the 72 h mixture expansion ratio decreased by 44%. This surface water isolation structure is valuable for inhibiting the volume expansion of steel slag and improving the performances of steel slag asphalt mixture.

Healing Performance of Granite and Steel Slag Asphalt Mixtures Modified with Steel Wool Fibers

This paper evaluates the induction healing performance of granite and steel slag asphalt mixtures modified with Steel Wool Fibers (SWF). A computerized tomography scan (CT-scan) was conducted to analyze microstructure and distribution of steel wool fibers in the mixture. Thermal conductivity was examined and heating rate was investigated with induction heating system. The healing performance was investigated by crack-heal cycles with three-point bending test. Dynamic modulus and repeated indirect tensile test were carried out to characterize the mechanical properties of asphalt mixtures modified with SWF. The results showed that the conductive properties and induction heating rate of asphalt mixture was enhanced by adding steel wool fibers and steel slag. The microanalysis results showed the agglomeration and uneven distribution of fibers in the mixtures when the mixed conductive additives exceed a certain dosage. It was found that heating rate of steel slag mixture was higher than that of granite mixture; however, its healing performance was slightly lower because of the cracking of weak steel slag. Finally, the mechanical test results demonstrated that the rutting resistance of asphalt mixtures was enhanced by adding steel wool fibers.

Evaluation of Steel Slag Powder as Filler in Hot-Mix Asphalt Mixtures

Abstract Steel slag has been used as an aggregate for asphalt mixtures for many years, but its excessive volume expansion has limited its wide applicability. With the development of steel-making technology, a considerable amount of steel slag powder (SSP) was produced in Shanghai. The objective of this article is to evaluate the feasibility of using SSP as a filler in hot-mix asphalt mixtures (HMAs), with the aim to eliminate the volume expansion of steel slag asphalt mixture while retaining good pavement performance. First, a common AC-13 mixture was designed with limestone aggregate and mineral filler. Then, 25, 50, 75, and 100 % of the limestone mineral filler in the AC-13 was replaced by SSP, according to the volume ratio, respectively. The asphalt content was kept constant in this process. Then the volume expansion property, rutting resistance property, low temperature property, moisture property, and failure property of the asphalt mixtures were checked. According to the test results, the AC-13 that used SSP exhibited negligible volume expansion, while other properties were better than those of the common AC-13, especially the rutting resistance and moisture properties. The test results also showed that the higher the replacement ratio of SSP, the greater the effect on the properties of the asphalt mixtures. Finally, it was concluded that SSP could replace mineral filler in asphalt concrete (AC) with better pavement performances and acceptable volume expansion.

Investigation of using steel slag in hot mix asphalt for the surface course of flexible pavements

The rapid development of heavy industry in Vietnam leads to the establishments of steel industry. Steel slag, a by-product of steelwork industry, under Vietnamese’s law, was considered as a deleterious solid waste which needed to be processed and landfilled. However, this has changed recently, and steel slag is now seen as a normal or non-deleterious solid waste, and has been studied for reuse in the construction industry. In this study, steel slag was used, as a replacement for mineral aggregate, in hot mix asphalt. Two hot mix asphalt mixtures with an equivalent nominal aggregate size of 12.5 (C12.5) and 19 mm (C19) were produced using steel slag. In addition, one conventional hot mix asphalt mixture of C19 was produced using mineral aggregate for comparison purpose. Investigation in laboratory condition and trial sections was carried out on Marshall tests, surface roughness, skid resistance, and modulus of the pavement before and after applying a new surface course of hot mix asphalt. The study showed that all steel slag asphalt mixtures passed the Marshall stability and flow test requirements. The skid resistance of steel slag hot mix asphalt mixtures for the surface course satisfied the Vietnamese specification for asphalt. Moreover, the pavement sections with the surface course of steel slag hot mix asphalt showed a considerable higher modulus than that of the conventional one. Only the roughness of the surface course paved with C19 did not pass the requirement of the specification.

Research on the Mechanical, Thermal, Induction Heating and Healing Properties of Steel Slag/Steel Fibers Composite Asphalt Mixture

In this paper, steel slag/steel fiber composite asphalt mixture were prepared. The effects of the addition of steel slag and/or steel fibers on the mechanical, thermal, induction heating and healing properties of asphalt mixture were investigated. The results showed that adding steel slag and/or steel fibers improves the water stability, particle loss resistance and fracture energy of asphalt mixtures. The addition of steel fibers increased the thermal conductivity and thermal diffusion of the asphalt mixture, and steel slag showed a reverse effect. Steel slag asphalt mixture cooled more slowly than steel fiber asphalt mixture, which is beneficial to crack healing of asphalt mixture. The composite of steel fibers and steel slag can enhance the induction heating speed, heating homogeneity and thus enhance the induction healing ratio of asphalt mixture. It is concluded that steel slag/steel fibers composite asphalt mixture achieves good mechanical and induction healing properties.

Snow and ice melting properties of self-healing asphalt mixtures with induction heating and microwave heating

In this paper, the snow and ice melting properties of self-healing asphalt mixtures with induction heating and microwave heating were investigated. The self-healing performance of the mixtures during ice melting process was measured with cyclic three-point bending test as well. The results indicated that the snow and ice melting performance of self-healing asphalt mixtures with appropriate heating techniques was remarkable. The average melting velocity of ice melting was improved from less than 1 g/min (previous researches) to more than 10 g/min, while the average snow melting velocity of steel fiber modified asphalt mixture and steel slag asphalt mixture with microwave heating could reach 53.9 g/min and 48.5 g/min respectively. The water from melted ice/snow played a major role in the melting process of snow with microwave heating. However, the moisture from melted ice/snow on the surfaces of crack prevented the thermal healing of asphalt mixtures. It is recommended that another heating process after the melting process should be applied to promote the healing of cracks as well as to prevent the melted snow and ice water on the pavement from freezing.

Self-healing performance of asphalt mixtures through heating fibers or aggregate

In this paper, two different designs of self-healing asphalt mixtures were promoted, the asphalt mixtures were healed through heating fibers or aggregate respectively. Induction heating and microwave heating were applied respectively to provide healing atmospheres. The thermal conductivity and temperature raising tests were conducted to measure the heating performance of those two self-healing asphalt mixtures. Infrared images were used to demonstrate the temperature field of asphalt specimens during heating. Cyclic fracture-healing test with three-point bending method was recorded to investigate the healing performance of the designed asphalt mixtures.It is concluded that asphalt mixtures containing steel fibers or steel slags could be healed with appropriate heating methods. It is also indicated that the healing performance of samples with microwave heating was a little better than the healing performance of steel fiber modified asphalt mixture with induction heating. The steel slag asphalt mixture showed a better performance of healing with the microwave as the temperature distribution was more uniform. Furthermore, the locally overheating and temperature uneven distribution remained to be big problems in the self-healing performance of asphalt mixtures in practical application.