Permeability Of Asphalt Mixtures Research Articles

Study on the pore blocking characteristics and cleaning methods of permeable asphalt mixtures based on accelerated clogging simulation experiments

Clogging in permeable asphalt pavements compromises their functional properties. Understanding clogging characteristics and developing appropriate maintenance methods is crucial. This study integrates indoor accelerated clogging simulations with Grey Relational Analysis to investigate the factors influencing clogging behavior. Computer tomography scanning and seepage model simulations are utilized to examine the distribution of clogging materials, seepage properties, and changes in pore parameters in permeable asphalt mixtures before and after clogging. Additionally, variable frequency vibration tests are conducted to evaluate the impact of vibration frequency on clog removal efficiency. Findings show that the cementation hardening effect of clay progressively seals pores, with sand particles of 0.15 mm diameter exerting the most significant influence on clogging. Wet-dry cycles lead to an accumulation of clay cementation, resulting in a 26.1 % and 72.4 % decrease in pore channel length and volume, respectively, at depths of 0–4.2 cm. The area within this depth range is most prone to clogging, increasing pore tortuosity. Seepage behavior is primarily determined by several main interconnected pores. Vibration test outcomes indicate that frequencies between 100 and 400 Hz are optimal for disrupting cementation blockages.

Investigation of Dynamic Viscoelastic Characteristics of Permeable Asphalt

In order to provide a basis for the structural analysis, design and maintenance of permeable asphalt pavements, and to promote their engineering promotion and application, this study investigated the dynamic viscoelastic properties of permeable asphalt mixtures (PAC-13) under complex stress states. A Simple Performance Tester (SPT) system was used to measure the dynamic modulus of the mix under complex stress states. The displacement factor and principal dynamic modulus curves were formed by fitting Sigmoidal functions and using 1stOpt (first optimization) software, the phase angle principal curves were further determined, and the dynamic modulus was predicted for the ambient phase (15–25 °C) using the Hirsch model. The results showed that the dynamic modulus of the mixtures decreases with an increasing temperature, and the maximum decrease in the dynamic modulus is 93% when the confining pressure is 100 kPa and the loading frequency is 10 Hz. The dynamic modulus increases with an increasing confining pressure and loading frequency, the maximum increase with an increasing confining pressure is 26.1% when the temperature is 25 °C and the loading frequency is 10 Hz, and the maximum increase with an increasing loading frequency is 411% when the temperature is 25 °C and the confining pressure is 100 Hz. The dynamic modulus has a strong frequency dependence at low temperatures, while it is stress-dependent at high temperatures. Meanwhile, based on the Hirsch model, a new modified prediction model was developed, which can well predict the dynamic modulus of permeable asphalt mixtures at room temperature.

Siltation behavior characterization and evaluation of permeable asphalt mixture based on computed tomography method

The pavement surface sediments are continuously transported into the pore structure of permeable pavement under hydraulic power, resulting in the loss of permeability function. Obtaining the siltation behavior of the permeable asphalt mixture is the key and foundation to achieving siltation prevention and control technology for permeable asphalt pavement. In this paper, a self-developed laboratory accelerated siltation test was designed, and X-ray diffraction (XRD), computed tomography (CT) experiments, intrinsic frequency tests were employed to explore the siltation behavior of permeable asphalt mixture. The test results reveal that the density of pavement surface sediments is approximately 15.2 g/m2 per day, and pavement surface rainwater contains 27.6% clay minerals, which exhibits induration consolidation property with dry-wet cycles. The blockage behavior caused by sand particles is 7.5% higher than that caused by clay. For the siltation contribution of permeable asphalt mixture, sand particles account for 81%, clay particles represent 7%, and the induration consolidation contributes 12% of the siltation. CT test results indicate that the lower 1/3 of permeable asphalt mixture is silted up with continuous adhesive deposition of clay. The dry-wet cycle is one of the key factors of hardening blockage, the hardening blockage primarily experiences three stages: stagnation and hardening, erosion and collapse, and deposition blockage. Intrinsic frequency test explores that the intrinsic frequency of permeable asphalt pavement is between 14,000 Hz and 15,000 Hz, and the intrinsic frequency of pavement surface sediment is 3968.83 Hz. The intrinsic frequency of pavement increases continuously with the transportation of surface sediment, and there is a good correlation between the siltation degree and intrinsic frequency of permeable asphalt mixture.

Study on the Performance of Phase-Change Self-Regulating Permeable Asphalt Pavement

Under low-temperature conditions in winter, asphalt pavement is prone to cracking, icing and other distresses, which affect its safety and comfort. Therefore, by incorporating phase-change materials into asphalt and conducting relevant performance studies, the aim is to alleviate low-temperature distress and regulate road surface temperature and expand the application of phase-change materials in asphalt pavement. We mixed the selected phase-change materials with different dosages into the matrix asphalt to prepare phase-change temperature-regulating asphalt and tested the four basic indicators: road performance, latent heat characteristics, temperature-regulating performance, and rheological properties of phase-change asphalt and its mixture. The research results indicate that with the increase in phase-change material content, the penetration, softening point, ductility, and dynamic viscosity of phase-change high-viscosity asphalt gradually increase. Under the constant temperature test conditions of −2.5 °C and −5 °C, the surface icing speed of asphalt binder specimens mixed with phase-change materials is slower than that of specimens without phase-change materials. Adding phase-change materials can improve the high-temperature and low-temperature PG grading of high-viscosity asphalt, effectively improving its high-temperature rutting resistance and low-temperature cracking performance. According to the temperature regulation test results, phase-change temperature-regulating asphalt has a certain regulating effect on temperature under low-temperature conditions, which can slow down the cooling rate of asphalt, reduce the thermal conductivity of permeable asphalt mixture by more than 50%, increase the temperature regulation rate by more than 30%, and improve the ice-melting and snow-melting ability by more than 20%. Phase-change materials have almost no effect on the porosity of permeable asphalt mixtures and can effectively improve the water stability, low-temperature crack resistance, and antiflying performance of permeable asphalt mixtures. Their Marshall stability and rutting stability decrease, but still meet the requirements of the specifications. Applying phase-change materials to permeable asphalt pavement can automatically adjust the temperature of the pavement, reduce the cooling rate of the asphalt pavement during cooling, alleviate the problem of snow and ice accumulation on the asphalt pavement in winter, and thereby improve the performance of permeable asphalt pavement against freeze–thaw cycles.

Experimental Study on Water Damage Resistance of Permeable Asphalt Mixture Under Coupling Action of High Temperature and Rainwater

Experimental Study on Water Damage Resistance of Permeable Asphalt Mixture Under Coupling Action of High Temperature and Rainwater

Preparation, performance evaluation and de-icing longevity prediction of novel de-icing fiber permeable asphalt mixture

The complex and changeable service conditions require pavements with greater functional diversity and environmental adaptability. In this paper, the de-icing fiber permeable asphalt mixture (DFPM) that satisfied the multiple service requirements of rapid drainage and ice melting in various seasons was proposed. Various performance characterization tests were utilized to evaluate the permeability and de-icing properties and the pavement performance of the mixtures with different contents of de-icing agents and fibers. Meanwhile, the high temperature dynamic water scouring experiment was designed to predict the effective de-icing life. The results show that adding de-icing agents and fibers slightly affects the water permeability of the mixtures. The incorporation of de-icing agents is beneficial to the high temperature performance yet detrimental to the low temperature behavior and water stability, while the incorporation of fibers compensates for the negative effect; the de-icing performance of the mixture correlates positively with the amounts of de-icing agents and correlates negligibly with the fiber incorporation. DFPM with 0.3% fibers and 5% de-icing agent shows superiority in performance and cost and is recommended for practical applications. Therefore, building a composite functional asphalt pavement with excellent performance appears feasible while creating a pavement micro-ecology by applying de-icing fibers permeable asphalt mixtures.

Research on morphology and distribution characteristics of clogging particles in permeable asphalt mixture

The deposition of clogged particles inside permeable asphalt mixture can cause the failure of its permeability. The morphology and distribution of particles are important factors affecting particle deposition. Therefore, the clogging mechanism of permeable asphalt mixture can be further clarified by studying the morphology and distribution characteristics of clogging particles. Five types of permeable asphalt mixtures with different gradations were prepared, and clogging tests were conducted under constant head control mode. Digital microscopy and image processing technology were used to analyze the shape characteristics of deposited and outflow particles. Combined with computer tomography technology, the distribution law of clogging particles along the depth direction of the specimens was analyzed. The results showed that during the clogging process, the mass change of outflow particles varied depending on the size of the clogging particles. The shape index and angularity range of the outflow particles are small, and when the particle size is small, the shape of the outflow particles is greatly influenced by the shape index and angularity of the original particles. When the filling degree of fine aggregate in the permeable asphalt mixture was high, particles with strong rolling ability would become outflow particles. The shape of particles and the filling degree of fine aggregate are important factors affecting the permeability performance of permeable asphalt mixtures. This study provides a reference for a deeper understanding of the clogging mechanism of permeable asphalt mixtures.

Pavement performance of previous pavement materials based on CAVF design

Based on the coarse aggregate void filling method (CAVF), four kinds of permeable asphalt mixtures (PAC) with target voids of 18%, 20%, 22%, and 25% respectively were designed, and their road performance was comprehensively evaluated by a series of laboratory tests, such as permeability tests, immersion Marshalls, freeze-thaw splitting, rutting, low-temperature bending, four-point fatigue bending, and so on. The experimental results show that the CAVF method is more accurate and PAC designed by the CAVF method has more connected voids and better pavement performance. The optimal design void ratio of the PAC is 22%.

Characterization of self-cleaning pavement coatings with catalytic-hydrophobic synergistic effects

The deterioration of the atmosphere around the road and the decrease in the cleanliness of the road surface due to fuel vehicle exhaust emissions, spilled transport goods, and vehicle wear deposition not only affect the experience of road users, but also threaten the health of the surrounding residents. Pavement coatings with self-cleaning functions can purify the atmosphere around the road and improve the cleanliness of the pavement. To provide raw material support for self-cleaning pavement coatings, hydrophobically modified TiO2 was prepared by Polytetrafluoroethylene (PTFE) coating method and epoxy resin modified silicone resin was prepared by the co-blending method. The optimal preparation scheme was selected to develop self-cleaning pavement coatings with catalytic-hydrophobic synergistic effects (SCPC). The exhaust gas degradation and hydrophobically cleaning performance of permeable asphalt mixture specimens with different SCPC spraying volumes were tested using self-developed evaluation methods. The experimental results show that modification of TiO2 with PTFE of 1.2 times its mass significantly increases the contact angle with little loss of photocatalytic performance. Under the best process and proportion, the epoxy resin and silicone resin are blended uniformly, and the mechanical properties can meet the demand of road use. The exhaust degradation and hydrophobically cleaning efficiency of SCPC are satisfactory when the spraying volume is greater than 500 g/m2. Moreover, the increase in spraying volume enhanced the hydrophobic cleaning ability. In addition, the SEM images show that the surface of SCPC presents a micron-level rough structure, which is conducive to enhancing the hydrophobic self-cleaning of SPSC. The permeability will inevitably be affected after SPSC is sprayed on the surface of permeable asphalt mixture, but when the spraying volume is less than 800 g/cm2, the attenuation rate of the permeability coefficient of the specimen is within 10%. The exhaust degradation and hydrophobic properties of the permeable asphalt mixture specimens with reasonable amounts of SPSC were tested after wear, and the attenuation was found to be very slight, indicating that the environmental performance of SPSC has good wear resistance.

Experimental Study of Permeable Asphalt Mixture Containing Reclaimed Asphalt Pavement

The current focus of research attention on reclaimed asphalt pavement (RAP) utilization is expanding the applications of RAP. This study aims to analyze the road performance of recycled permeable asphalt mixtures (RPAMs), which represents a novel direction for utilizing RAP. Firstly, the Marshall design method was used to carry out the material composition design of the RPAM with varying RAP contents (10%, 20%, and 30%). Subsequently, the performance of the RPAM with different RAP contents (10%, 20%, and 30%) and preheating temperatures (120 °C, 130 °C, 140 °C, 150 °C, and 160 °C) was tested with a permeable asphalt mixture containing 12% high-viscosity asphalt as the control group. The mixture’s performance included high-temperature stability, low-temperature crack resistance, water stability, anti-raveling performance, and dynamic mechanical properties. The results indicate that the higher the RAP content, the better the high-temperature performance of the RPAM, while the low-temperature performance, water stability, and anti-raveling performance deteriorate. At 30% RAP content, its pavement performance is comparable to that of the control group mixture. However, increasing RAP preheating temperature can improve low-temperature and water stability but may reduce high-temperature performance. The optimal RAP preheating temperature for pavement performance is between 140 and 150 °C. The dynamic modulus test showed that the higher the RAP content, the greater the dynamic modulus of the RPAM, leading to better high-temperature stability but reduced low-temperature crack resistance. The influence of RAP preheating temperature is the opposite. These test results demonstrate the feasibility of utilizing RAP for paving permeable asphalt pavement under controlled RAP content and preheating temperature conditions.

Investigation on flow resistance of fluid in permeable asphalt mixture

Flow resistance distribution of fluid is the basis of comprehensively grasping the permeability of permeable asphalt mixture. This study aimed to investigate the flow resistance of fluid in permeable asphalt mixture. Considering the influence of anisotropy of permeable asphalt mixture, the vertical and transverse permeability tests of five types of permeable asphalt mixture were carried out using multidirectional permeability test instrument developed by our research group. The fitting equation of permeability was determined by comparing Darcy's law with Forchheimer equation. Moreover, the flow resistance is usually considered as an effective parameter to reveal the structural permeability. The connective void content of permeable asphalt mixture is important to calculate flow resistance. Accordingly, it is necessary to obtain the transverse and vertical connective voids of the asphalt mixture considering the influence of anisotropy. Therefore, a program for calculating the multi-directional connective void content was developed based on the theory of projection reconstruction. On this basis, a pore throat model was applied to reveal the variation of flow resistance of asphalt mixture. The results show that the weight of inertia resistance and viscous resistance is different in various seepage velocities. The viscous resistance is dominant when the fluid flow velocity is less than 0.0087 m/s under experimental conditions, and the inertial resistance is dominant when the fluid flow velocity is greater than 0.0087 m/s. The viscous resistance and inertia resistance of fluid are affected by the anisotropy and structure type of permeable asphalt mixture. When the vertical void content decreases by 3.3%, the corresponding viscous and inertial resistance increase by 7.92 kPa/m and 0.84 kPa/m, respectively. For the transverse void, the viscous and inertial resistance increase by 3.19 kPa/m and 2.02 kPa/m respectively as the content decreases by 3.5%. The influence of void structure of permeable asphalt mixtures on fluid flow is revealed from a microscopic perspective, which can be used to guide the optimization design of gradation of permeable asphalt mixtures.

Effect of temperature and water conditioning on noise and skid resistance of dense-graded, open-graded and gap-graded asphalt mixes

With the rapid development of the transportation industry, permeable asphalt pavement has become widely used in the construction of expressways and urban roads due to its safety, comfort, and environmental protection characteristics. However, water-temperature coupling can damage the mechanical properties of permeable asphalt mixtures. The use of high-viscosity modified asphalt can improve the water damage resistance of the mixture to a certain extent, resulting in better mechanical properties. This paper focuses on the preparation of PAC-13 mixture specimens using high-viscosity modified asphalt and the study of its noise reduction and anti-skidding properties under water-temperature coupling. SMA-13 and AC-13 are used for comparative research. The influence of water-temperature coupling on the functional characteristics of permeable asphalt mixture is analyzed through standing wave tube test and pendulum test. The results show that PAC-13 exhibits better noise reduction and anti-skidding characteristics than SMA-13 and AC-13. As the temperature increases, the skid resistance of asphalt mixtures weakens, but the noise reduction properties are less affected. Furthermore, the noise reduction and anti-skidding properties of the three mixtures are significantly damaged by the action of water, with PAC-13 being the most affected. Nevertheless, PAC-13 still exhibits the best noise reduction and anti-skidding properties.

Preparation and Performance Evaluation of Deicing Permeable Asphalt Mixture

This article aims to propose an asphalt mixture with deicing and permeable functions to address the dilemma of excessive stormwater runoff during summer and ice accumulation in winter for pavement in southwest China. A peeling test and ice melting test were first conducted to select one powder and one granular anti-icing additive for better deicing performance. Then the effects of anti-icing additive contents on deicing and pavement performance of deicing permeable mixtures were investigated to select the best content. Additionally, the effect of immersion treatment on the pavement performance of deicing permeable mixture was analyzed. The results showed that the rise in additives content would help to improve deicing performance, as expected, regardless of additive type. The optimal content of the powder additive was reached by replacing 80% of the mineral powder, and the optimal mass ratio of granular type was 5% of the mixture. The addition of additives weakened the low-temperature performance and water-stability performance of the permeable mixture, whereas a high-temperature performance was observed when granular additive was adopted. The pavement performance of the mixture with granular additive was better than the mixture with powder additive under different immersion treatments. Overall, the granular anti-icing additive is recommended for use in a permeable mixture. This research is helpful and may provide guidance for the design of deicing permeable asphalt mixtures.

Research on low-temperature performance of steel slag/polyester fiber permeable asphalt mixture

In order to improve the low-temperature crack resistance of the permeable asphalt mixture, five steel slags with equal volumes of substitution rates (0%, 25%, 50%, 75%, 100%) were used to replace the limestone coarse aggregate above 2.36 mm. At the same time, six types of polyester fibers (0%, 0.30%, 0.35%, 0.40%, 0.45%, 0.50% by the weight of the mixture) were selected to prepare permeable asphalt mixture samples. The ultrasonic non-destructive testing test, semi-circular bending (SCB) test and scanning electron microscope (SEM) test were carried out to study the cracking performance of steel slag/polyester fiber asphalt mixture at low temperature (0 °C, −10 °C, −20 °C). Ultrasonic non-destructive testing shows that by appropriately increasing the number of compactions (85 times), the aggregate embedding effect of G50X0.45 permeable asphalt mixture can be increased, and the compactness of the mixture can be improved. SCB test results suggest that the critical load for cracking of steel slag/polyester fiber permeable asphalt mixture first increased and then decreased with the decrease of temperature, reaching the maximum at −10 °C; At 50% steel slag replacement rate and 0.45% polyester fiber content, the ultimate tensile stress and ultimate tensile strain of the asphalt mixture were the largest, showing the optimal low-temperature crack resistance. The SEM test results indicate that adding steel slag enhances the embedding and squeezing effect between the internal aggregates of the mixture, the physical and chemical adsorption between the steel slag and the asphalt forms an asphalt orientation layer, which enhances the cohesion of the mixture. The incorporation of polyester fiber weaves a three-dimensional structure network inside the mixture, which firmly locks the coarse and fine aggregates together, greatly improves the density of the mixture, reduces the freeness of the asphalt, and thus improves low-temperature crack resistance of steel slag/polyester fiber asphalt mixture.

Permeable Asphalt Hydraulic Conductivity and Particulate Matter Separation With XRT

Permeable asphalt (PA) is a composite material with an open graded mix design that provides a pore structure facilitating stormwater infiltration. PA is often constructed as a wearing course for permeable pavements and on impervious pavements to reduce aquaplaning and noise. The pore structure of PA functions as a filter promoting particulate matter (PM) separation. The infiltrating flow characteristics are predominately dependent on pore diameter and pore interconnectivity. X-Ray microTomography (XRT) has successfully estimated these parameters that are otherwise difficult to obtain through conventional gravimetric methods. Pore structure parameters allow modeling of hydraulic conductivity (k) and filtration mechanisms; required to examine the material behavior for infiltration and PM separation. In this study, pore structure parameters were determined through XTR for three PA mixture designs. Additionally, the Kozeny-Kovàv model was implemented to estimate k. PM separation was evaluated using a pore-to-PM diameter categorical model. This filtration mechanism model was validated with data from a rainfall simulator. The filtration model provided a good correlation between measured and modeled data. The identification of filtration mechanisms and k facilitate the design and evaluation of permeable pavement systems as a best management practice (BMP) for runoff volume and peak flow as well as PM and PM-partitioned chemical separation.

Presentation of Predictive Models for Two-objective Optimization of Moisture and Fatigue Damages Caused by Deicers in Asphalt Mixtures

Abstract The best way to deal with the freezing of the road surfaces is to use deicers, especially in cold areas. The presence of moisture causes various stresses in the pavement and reduces the strength of mixtures. Using anti-stripping agents can decrease the moisture sensitivity of asphalt mixtures. Researchers have evaluated the impact of different deicers on the moisture sensitivity of asphalt mixtures. However, fewer studies have been conducted on the effect of these materials on fatigue failure and thermodynamic parameters of asphalt mixtures. Moreover, fewer studies have been performed to find the exact optimum amount of additives for maximizing the two objectives of tensile strength ratio (TSR) and fatigue life ratio (NFR) concurrently in moisture and fatigue damages. So in this research, the moisture sensitivity and fatigue failure of asphalt mixtures under the influence of different deicers, including calcium magnesium acetate (CMA), potassium acetate (PA), and sodium chloride (NaCl), were investigated using nanohydrated lime (NHL) as an anti-stripping agent. The surface free energy (SFE) of materials and the permeability of asphalt mixtures were examined, and a boiling water test was applied. Finally, the prediction models of multivariate regression (MVR), group method of data handling (GMDH), and genetic programming (GP) were provided to obtain optimum additive percentage with two objectives of TSR and NFR. The results showed that GP had a higher R-value than the 2 other methods such that the R-value of GP for TSR and NFR was 98.8 % and 99.8 %, respectively. The optimization results showed that 1.17 %, 1.34 %, 0.87 %, 1.21 %, and 1.06 % NHL, respectively, were the best optimum values to maximize the TSR and NFR simultaneously in all samples and samples saturated in water, CMA, NaCl, and PA solutions.

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%.

Permeability of Asphalt Mixtures with Bailey and Conventional Aggregate Gradations

Highly permeable asphalt mixtures are prone to moisture damage leading to reduction in pavement service life. This study correlates dense-graded asphalt mixture’s air voids with its permeability. As permeability initiates due to significant interconnectivity of air voids, the relation between total air voids (TAVs) and connected air voids (CAVs) requires a critical review. Permeability of laboratory-compacted asphalt specimens was measured in the laboratory using four different permeameters. Conventional and Baily methods were utilized to develop aggregate gradations for asphalt mixtures. Different testing techniques were also used to ascertain the amount of CAVs, as aggregate gradation affects the airvoids significantly. An equation, based upon Darcy’s law, while assuming equilibrium of inflow/outflow of water to and from asphalt sample was proposed to determine the CAVs in the asphalt mix. The digital images of asphalt specimens were captured, and digital computed tomography (CT) technique was employed using ImageJ software for validation of the CAVs estimated from the relationship. It was observed that air voids, especially CAVs, and type of aggregate gradation have significant effects on permeability of asphalt mixture. The Baily modified mixes exhibited lower permeability. The permeability also increased with an increase in nominal maximum aggregate size. The interconnected pores, determined with the help of digital CT technique, validate the values of air voids estimated from the proposed relationship.

Evaluation of Siltation Degree of Permeable Asphalt Pavement and Detection of Noise Reduction Degree

This study mainly uses PFC (particle follow code) to simulate the void characteristics of permeable asphalt mixture, and uses these to simulate the silting process. Then, a tire drop test was used to evaluate the noise reduction performance of permeable asphalt concrete. Finally, a self-made ring rutting test machine was used to simulate the silting process. Through experiments, the following conclusions were obtained: 1. The critical size of the sludge particle size is 0.3 mm–0.6 mm. 2. The quality of the water-permeable asphalt concrete specimens increased by 13% before and after silting, and the porosity of the specimens finally decreased from about 20% to about 8%. The water-permeable function only retained less than 20% of the original, and the water-permeable function was basically lost. 3. By measuring the road noise detection, it was found that the road noise is directly proportional to the degree of blockage of the permeable road. Compared with the original road with a perfect permeable function, the road noise of the completely blocked road increased by about 4 decibels. This study reveals the silting process of permeable asphalt mixture and the key particle size of the silt, which is of great significance for the detection, cleaning and maintenance of permeable asphalt pavements.

Performance Enhancement of Permeable Asphalt Mixtures With Recycled Aggregate for Concrete Pavement Application

The incorporation of recycled concrete aggregate (RCA) in permeable asphalt mixtures (PAM) is an efficient method of utilizing construction demolished waste. It not only conforms to the trend of building sponge cities, but also alleviates the problem of overexploitation of natural aggregate resources. As the performance of PAM containing recycled aggregate is not comparable to natural aggregate, modification treatments and hybrid fibers addition are adopted as two enhancement methods to improve the performance of PAM with RAC in this study. It is found that replacing natural aggregate with recycled aggregate increases the optimum asphalt content but decreases the residual stability. The optimum asphalt content is increased by 45% when the RCA ratio is 100%, whereas applying silicone resin can gives a 16.2% decrease in the optimum asphalt content. Enhancing RCA with silicone resin can increase the water stability to be comparable with natural aggregate. Moreover, with modification treatment using calcium hydroxide solution, the mechanical strength of PAM is enhanced to even higher than that only with natural coarse aggregate mixture. Improvements in both mechanical strength and water stability are also achieved by strengthening recycled aggregate with cement slurry, although the performance is less effective than using silicone resin. With the increase in the content of RCA, the permeability coefficients of PAM first decrease and then exhibit an increasing trend. The results indicate that the PAM with RCA and modification treatments can perform satisfactorily as a pavement material in practice. Applying probable modification, PAM incorporating RCA meets the criteria for use in concrete pavement applications.