Search Results (29)

Porous asphalt concrete (PAC) is widely recognized for its excellent performance in drainage, noise reduction, and environmental protection due to its high interconnected porosity. However, challenges remain in relationships between mesoscopic void parameters and permeability performance. To reveal the influence mechanism of meso-structural parameters on the permeability performance of PAC, the X-ray CT scanning and computational fluid dynamics (CFD) simulation techniques were combined in this study. A PAC-13 mixture was selected and prepared with target porosities of 18%, 20%, and 25%. The three-dimensional meso-structure of the specimens was measured using a CT scanner with a resolution of 0.08 mm, and the void parameters were extracted using Image J v1.8.0 software. The mesoscopic parameters of PAC and its impact on permeability performance were analyzed. Moreover, a three-dimensional void model was reconstructed using Avizo 9.0 software. The seepage performance was analyzed using CFD simulation. The results show that the roundness, the ratio of long to short axes, and the equivalent diameter of the voids increase linearly with porosity from 18% to 25%. The void number distribution shows a Gaussian characteristic. The permeability coefficient of PAC mixtures gradually increases linearly with the increase in porosity from 18% to 25%. Good relationships can be found between mesoscopic distribution characteristics and the permeability coefficient, where the coefficients of determination are larger than 0.97. The surface seepage pressure is nearly ten times more than the bottom pressure. The influence depth of seepage pressure is deeper with the increase in porosity, while the seepage velocity increases with the increase in porosity. This study offers valuable insights into the functional design and performance optimization of PAC materials. Full article

This study evaluated the environmental sustainability of partially replacing natural aggregates with electric arc furnace (EAF) slag in concrete and porous asphalt mixtures. Both the Equilibrium Leaching Test (EN 12457-4) and the Dynamic Surface Leaching Test (DSLT, CEN/TS 16637-2) were applied to analyse the leaching behaviour of the asphalt mixtures. The results showed that the incorporation of EAF slag led to the release of chromium (Cr), molybdenum (Mo), and vanadium (V), while the type of bitumen affected the dissolved organic carbon (DOC) release. However, when compared to EAF slag leaching, asphalt mixtures exhibited significantly reduced leaching, particularly Cr (by 70%) and V (by 60%). These results indicate that metal leaching follows a diffusion-controlled release mechanism, showing higher concentrations for the porous asphalt compared to the asphalt concrete. The cumulative leaching values at 64 days reached 2.54 mg·m⁻² for Cr, 3.29 mg·m⁻² for Mo, and 28.67 mg·m⁻² for V, far from the limits set by the Dutch Soil Quality Decree (SQD) of 120, 144, and 320 mg·m⁻², respectively. Therefore, this study demonstrated that EAF slag is a viable alternative for sustainable road construction, reducing natural resource consumption and promoting the circular economy. Full article

In cold regions, the overlay effect often leads to pavement and subgrade distresses, severely compromising the functionality of roads and infrastructure. To address this issue, this study proposes a solution involving permeable pavements and roadbed structures. However, the application of permeable pavement materials in cold regions remains a significant challenge. Building on previous research, this paper introduces a novel pavement material with exceptional mechanical and temperature performance: terminal carboxylated nitrile rubber-modified epoxy asphalt. Specifically, the mechanical properties, viscosity, high-temperature rutting resistance, low-temperature cracking resistance, and modification mechanisms of five terminal carboxylated nitrile rubber-modified epoxy asphalt mixtures with varying terminal carboxylated nitrile rubber contents were investigated. Additionally, the high-temperature, low-temperature, and water stability properties of three types of porous asphalt concrete were compared. The results demonstrate that the incorporation of terminal carboxylated nitrile rubber significantly enhances the mechanical properties and low-temperature cracking resistance of the asphalt without altering the curing time. Although the high-temperature rutting resistance of the asphalt itself decreases, the high-temperature, low-temperature, and water stability properties of the porous asphalt concrete are improved. This improvement is attributed to the chemical reaction between terminal carboxylated nitrile rubber and epoxy resin, which generates a prepolymer containing new substances and forms a stable sea–island structure. This structure promotes a more homogeneous distribution of the asphalt matrix, thereby increasing the cohesive strength and toughness of the asphalt. Full article

The substantial voids of porous pavement materials permit light and exhaust pollutants to infiltrate to a considerable depth. Consequently, utilizing porous mixtures as carriers for photocatalytic materials enables greater exposure to an environment conducive to the exhaust degradation reaction. This study employed porous asphalt mixtures and porous cement concrete as carriers for photocatalytic pavements. Various amounts of TiO₂ were incorporated as photocatalysts to produce eco-friendly pavement materials with exhaust degradation capability. Based on a self-developed apparatus and methodology, its exhaust degradation performance was evaluated under different preparation conditions and pavement structures. The influences of void ratio, photocatalyst dosage, pavement type, and pavement thickness on the exhaust degradation function were examined. The degradation rates of NO and CO among the four monitored pollutants were observed to follow a three-stage pattern of “slow–fast–steady”, while the degradation rates of NO₂ and HC followed a “fast–slow–steady” pattern. Increasing the void ratio and the photocatalyst dosage yielded similar effects on exhaust degradation efficacy, enhancing the degradation rate and reducing the time required to reach equilibrium. The increase in the void ratio of porous asphalt mixtures and porous cement concrete reduced the time required to reach equilibrium by an average of 4.4 and 2.3 min for the four pollutants monitored, respectively. Increasing the dosage of photocatalytic material by 2 kg/m³ increased NO degradation by an average of 1.5% and reduced the time required to reach equilibrium by an average of 0.8 min. The degradation rate of porous cement concrete in the first reaction stage was faster than that of porous asphalt mixtures, and the time required to reach equilibrium state increased by 2 min compared to that of porous asphalt mixture. And the impact of specimen thickness on exhaust degradation performance was minimal. Full article

The construction industry is a fundamental sector for the development of countries; however, it produces negative environmental impacts due to the demand for natural resources and the generation of construction and demolition waste (CDW). Therefore, the pursuit of solutions to recycle and reintegrate these wastes, which often accumulate in poorly regulated areas, becomes not only an environmental priority but also an opportunity to transform a problem into an advantage. Utilizing these residues contributes to reducing the pressure on natural resources, minimizes the environmental footprint of the construction sector, and promotes a more sustainable and responsible model that can serve as an example for future generations. The properties of recycled concrete aggregates (RCA) and recycled asphalt pavement (RAP) were determined in order to subsequently obtain the properties of different permeable recycled concrete (RPC) elaborated from a factorial design 2³ with these aggregates. The properties studied were workability, permeability, volumetric weight, compression uniaxial, and bending. Finally, they were studied and correlated with their matrix microstructure by means of TGA and SEM tests, which allowed determining the compounds contained in the various mixtures and their impact on physical–mechanical behavior. The results indicate that RCA and RAP are feasible alternatives for making porous pavements in pedestrian or light traffic areas when recycled aggregates of 3/4” size are included in their matrix, resulting in the optimum dosage of the M5 3/4” mix in this research, whose mechanical properties are: uniaxial compressive strength: 15.39 MPa; flexural strength: 3.12 MPa; permeability: 0.375 cm/s. Full article

The article presents the chemical composition of vermiculite ores from the Kulantau deposits and the atomic structure of vermiculite during dehydration, in 1-, 2- and 3-layer hydrated states. It has been shown that vermiculites from deposits in the Turkestan region have significant differences in mineralogical composition. Rational ways of using Kulantau vermiculite as an innovative modifying additive in bitumen compositions are considered, which are intended to improve the asphalt concrete mixture during its preparation. A slight increase in structuring resins is a result of the elevated content of high-molecular-weight asphaltenes in the modified bitumen, as indicated by the analysis of the provided spectra. In turn, the systematization or structuring of bitumen leads to an increase in the mixture density, accompanied by a simultaneous rise in internal friction coefficients, and resistance to loads (shear and impact), as well as an enhancement in compressive strength. The influence of the chemical composition of Kulantau vermiculite on the structure of bitumen compositions is characterized by high adsorption capacity and effectively absorbs products resulting from the oxidation of hydrocarbons. Vermiculite is characterized by high efficiency in the activation phase, large pore volume, and selectivity. The alteration of the bitumen’s group composition due to the selective diffusion of oils, as well as resins in the material, occurs as a result of the interaction between bitumen and a material characterized by a fine-porous structure and high specific surface area. This process modifies the properties of bituminous layers on the surface of particles and leads to the formation of robust bitumen films appearing on the grain surfaces. Thus, enhancing the longevity of coatings, improving the quality of binding bitumen, and reducing asphalt concrete coverings necessitate the use of vermiculite in creating modified bituminous compositions. Full article

One of the problems that limit the development of porous asphalt concrete (PAC) is that the pores become clogged, which leads to severe deterioration in its permeability performance. This paper focuses on PAC’s permeability characteristics under repeated cycles of clogging. First, sand (S), clay (C), and sand and clay mixtures (S + C) were used as clogging materials for repeated clogging tests. Then, the permeability coefficients in the initial state and after clogging were measured with an improved permeability device. Based upon porosity, maximum nominal particle size, and clogging materials, the paper analyzed the permeability regulation of PAC under repeated clogging conditions. In addition, we compared the restoration effects of vacuum cleaning, high-pressure cleaning, and surface cleaning with cleaning tests and proposed a response surface methodology prediction model. Finally, the particle size distribution of sensitive particles that cause different porosities in PAC clogging was explored. The results showed that the initial permeability coefficient and the permeability coefficient with PAC’s repeated clogging increased with the increase in the nominal maximum particle size and porosity. PAC clogged by sand has the greatest rate of reduction in the coefficient of permeability. In addition, we suggested that in PAC pavement maintenance work, water is first sprinkled to wet the road, then high-pressure cleaning used, and finally vacuum cleaning. The prediction model is reliable and the cleaning method has the most significant effect on the permeability coefficient. Further, the particle size distribution that caused PAC-13 and PAC-10 clogging ranged from 0.15 to 2.36 mm and 0.075 to 2.36 mm, respectively. Full article

Thermal conductivity is a fundamental material parameter involved in various infrastructure design guides around the world. This paper developed an innovative neural network (NN) aided homogenization approach for predicting the effective thermal conductivity of various composite construction materials. The 2-D meso-structures of dense graded asphalt mixture, porous asphalt mixture, and cement concrete were generated and divided into 2ⁿ × 2ⁿ square elements with specific thermal conductivity values. A two-layer feed-forward neural network with sigmoid hidden neurons and linear output neurons was built to predict the effective thermal conductivity of the 2 × 2 block. The Levenberg-Marquardt backpropagation algorithm was used to train the network. By repeatedly using the neural network, the effective thermal conductivities of 2-D meso-structures were calculated. The accuracy of the above NN aided homogenization approach was validated with experiment, and various factors affecting the effective thermal conductivity were analyzed. The analysis results show that the accuracy of the NN aided approach is acceptable with relative errors of 1.92~4.34% for the dense graded asphalt mixture, 1.10~6.85% for the porous asphalt mixture, and 1.13~3.14% for the cement concrete. The relative errors for all the materials are lower than 5% when the heterogeneous structures are divided into 512 × 512 elements. Ignoring the actual material meso-structures may lead to significant errors (134.01%) in predicting the effective thermal conductivity of materials with high heterogeneity such as porous asphalt mixture. While proper simplification is acceptable for dense construction composite materials. The effective thermal conductivity of composite cement-asphalt mixtures increases with higher saturation of grouted material. However, the improvement effect of the high-conductive cement paste on the composite cement-asphalt mixtures could be significantly reduced when the cement paste concentrates at the bottom of the mixture. Cracked aggregates and segregation of material components tend to decrease the effective thermal conductivity of construction materials. The NN aided homogenization approach presented in this paper is useful for selecting the effective thermal conductivity of construction materials. Full article

Moisture is a significant problem in standard pavements, causing asphalt mixtures to deteriorate due to insufficient water permeability. This failure from moisture damage is often caused by precipitation accumulation or poor drainage, which allows water to weaken adhesion by seeping between the aggregates and the asphalt. The relationship between permeability and aggregate contact length is believed to be inverse. To effectively assess water permeability performance and moisture damage, an asphalt concrete design criterion was established using the Image Processing and Analysis System (IPAS) to determine aggregate contact lengths. The objective of this research was to use laboratory experiments in conjunction with IPAS to investigate air-void-controlled asphalt mixtures with various material properties and assess the correlation of water permeability with other factors. The results show that AC60/70, AC60/70+Carbon Black, and AC60/70+SBS combinations with coconut peat filler had the lowest permeability coefficient (k) among similar mixtures, with values of 0.056 × 10⁻⁵ cm/s, 0.010 × 10⁻⁵ cm/s, and 1.508 × 10⁻⁵ cm/s, respectively. Both the dense and porous gradations of the modified asphalt binder demonstrated positive linear relationships between TSR and permeability. This study found a strong linear relationship between TSR (tensile strength ratio) and k (permeability coefficient) in both dense and porous modified asphalt binder gradations, with R² values of 0.79 and 0.74, respectively. Additionally, we found that the number of contact points and contact length in the skeleton strongly influenced the mixes’ permeability, with a linear trend of 0.93 for both indices. Full article

This study investigates the effects of two waste materials from construction and industry, namely recycled concrete aggregate (RCA) and Type C fly ash, on the overall performance of a special type of pavement surface mixture, porous asphalt mixture. Mixtures of different combinations of RCA (for partial aggregate replacement) and fly ash (for filler replacement) were prepared in the laboratory and tested for a variety of pavement surface performance parameters, including air-void content, permeability, Marshall stability, indirect tensile strength, moisture susceptibility, Cantabro loss, macrotexture, and sound absorption. The analysis of the results showed that incorporating RCA or fly ash in a porous asphalt mixture slightly reduced the air-void content, permeability, and surface macrotexture of the mixture. A 10% replacement of granite aggregates with RCA in the porous asphalt mixtures led to a reduction in mixture stability, indirect tensile strength, resistance to raveling, and sound absorption. The further substitution of mineral filler with fly ash in the mixture, however, helped to offset the negative impact of RCA and brought the mechanical properties of the mixture with 10% RCA to levels comparable to those of the control mixture. Full article

Compounds with lower dynamic stiffness are a better solution from the tyre/road noise point of view. The article presents the constructed test stand for the evaluation of dynamic stiffness both in in situ and in laboratory conditions. As a result of the tests, it was found that poroelastic pavements have a much lower dynamic stiffness (from 138.3 to 143.0 dB re. 1 N/m) compared to the asphalt concrete pavement (150.3 dB re. 1 N/m). In the group of poroelastic pavements, lower dynamic stiffness is characteristic for pavements with a binder course of porous asphalt. The results of the research are a contribution to further work on the influence of the dynamic stiffness of the pavements on the tyre/road noise level. The conducted measurements and analysis of the results prove the usefulness of the proposed test stand for determining the dynamic stiffness of bituminous mixtures in laboratory and field conditions. This is confirmed by the coherence between the force and acceleration signals at the level of at least 0.96—which indicates a very good validation of the test results with a random error lower than ±5% with 90% confidence level. Full article

The sound absorption of a road pavement depends not only on geometric and volumetric factors but also on pore shape factors. In turn, pore shape factors mainly refer to thermal and viscous factors (i.e., thermal and viscous effects that usually occur inside porous materials). Despite the presence of a number of studies and researches, there is a lack of information about how to predict or estimate pore shape factors. This greatly affects mixture design, where a physical-based or correlation-based link between volumetrics and acoustics is vital and plays an important role also during quality assurance and quality control (QA/QC) procedures. Based on the above, the objective of this study is to link mixture volumetrics and pore shape factors. In particular, 10 samples of a porous asphalt concrete were tested in order to estimate their thickness, air voids content (vacuum-sealing method, ASTM D6857/D6857M), sound absorption coefficient (Kundt’s tube, ISO 10354-2), airflow resistivity (ISO 9053-2), and permeability (ASTM PS 129). Subsequently, two models (herein called STIN and JCAL) were used to derive both volumetrics and pore shape factors from the estimated parameters listed above, and statistical analysis was carried out to define correlations among the parameters and models performance. Results confirm the complexity of the tasks and point out that estimates of the pore shape factors can be derived based on mixture volumetrics. Results can benefit researchers (in acoustic and pavement mixtures) and practitioners involved in mix design and pavement acceptance processes. Full article

The high pavement temperature plays an important role in the development of urban heat island (UHI) in summer. The objective of this study was to develop water retentive and thermal resistant cement concrete (WTCC) to enhance the pavement cooling effects. The WTCC was prepared by combining a water retentive material and a high aluminum refractory aggregate (RA) with porous cement concrete (PCC). Water retention capacity test, fluidity test, and compressive strength test were used to determine the composition ratio of the water retentive material. Mechanical performance and cooling effects of WTCC were evaluated by compressive and flexural strength tests and temperature monitoring test. The mass ratios of fly ash, silica fume, cement, and water in the water retentive material were determined as 65:35:15:63.9. The compressive strength and the flexural strength of WTCC after 28 days curing were 30.4 MPa and 4.6 MPa, respectively. Compared with stone mastic asphalt (SMA) mixture, PCC, and water retentive cement concrete (WCC), surface temperature of WTCC decreased by 11.4 °C, 5.5 °C, and 4.1 °C, respectively, and the internal temperatures of WTCC decreased by 10.3 °C, 6.1 °C, and 4.6 °C, respectively. The water retentive material has benefits of strength improvements and temperature reduction for WTCC. Based on the results, WTCC proved to have superior cooling effects and the potential to efficiently mitigate the UHI effects and be used in medium traffic roads. Full article

Microwave heating has been shown to be an effective method of heating asphalt concrete and in turn healing the damage. As such, microwave heating holds great potential in rapid (1–3 min) and effective damage healing, resulting in improvement in the service life, safety, and sustainability of asphalt pavement. This study focused on the microwave healing effect on porous asphalt concrete. Steel wool fibres were incorporated into porous asphalt to improve the microwave heating efficiency, and the optimum microwave heating time was determined. Afterwards, the microwave healing efficiency was evaluated using a semi–circular bending and healing programme. The results show that the microwave healing effect is largely determined by the steel fibre content and the mix design of the porous asphalt concrete.. Besides, the uneven heating effect of microwave contributes to an unstable damage recovery in the asphalt mixture, which makes it less efficient than induction heating. However, microwaves exhibited the ability to penetrate further into the depth of the test specimen and heat beneath the surface, indicating deeper damage recovery prospects. Full article

The carbon footprints of asphalt mixtures with increasing reclaimed asphalt pavement (RAP) content were estimated using a life-cycle assessment methodology. Three asphalt mixtures with different applications and technical requirements, namely porous asphalt (PA), stone mastic asphalt (SMA), and asphalt concrete (AC), were included. The technology leaps needed to achieve asphalt mixtures containing up to 93% RAP were modelled. Mixtures containing up to 57% RAP were hot-mix asphalts (175 °C), while mixtures containing more RAP were produced at 135 °C and 105 °C. The energy requirements and their respective carbon footprints were calculated based on the heat capacity of the aggregates, RAP, and other bituminous materials. Furthermore, the effects of changing the country’s electricity mix were also evaluated. A potential carbon footprint reduction of between 55% and 64% was found for one tonne of asphalt containing 93% RAP and produced at 105 °C compared to the 0% RAP mixture produced at 175 °C. Considering the uncertainty of this technology at its early stage of development, the reduction could be as low as 45% or as high as 79%. Changing the electricity mix to one that is likely to be implemented until 2030 in the Netherlands further reduces the footprint by 10%. Full article