Road Pavement Research Articles

Geomechanical and Thermal Properties of Lateritic Gravels for the Design of Road Pavements in Tropical African Environments

Geomechanical and Thermal Properties of Lateritic Gravels for the Design of Road Pavements in Tropical African Environments

Accelerating Plastic Pollution Mitigation through Sustainable Urban Infrastructure Development

Plastic waste plagues both land and aquatic environments. The surface layer refers to the road pavement layer that comes into direct contact with a vehicle's wheel surface. The surface layer distributes wheel load far more evenly than the layer underneath. The surface layer design incorporates top-notch materials that can be used as additives to enhance the quality of the asphalt mixture. This study evaluates the asphalt mixture's durability using Marshall characteristics and Cantabria tests carried out in a lab setting. An ideal asphalt concentration of 5.25% is obtained. Low Density Polyethylene (LDPE) is added to the asphalt mixture at various contents, 0%, 2%, 4%, 6%, and 8%. The study's findings indicate that adding plastic waste to the asphalt mixture can enhance its performance. The two main mitigating actions are probably plastic prohibition laws and public awareness campaigns. To evaluate the possible environmental effects and resources utilized over the course of a plastic product's life span, researchers stress the importance of its life cycle assessment and circularity. Innovations are necessary to minimize, reuse, recycle, recover, and develop environmentally friendly plastic substitutes. By empowering and educating communities and citizens on how to reduce plastic pollution and use alternative plastic solutions, governments must enforce and promote collective action. This research must prioritize addressing plastic waste as a global issue.

Experimental research on fatigue behavior of concrete under acid rain corrosive environment

Concrete infrastructures such as high-speed railway bridges, road pavements, and airport runways in acid rain areas are severely affected by fatigue loading and environmental corrosion. To investigate the impact of acid rain corrosion on the fatigue resistance of concrete, 12 groups of concrete specimens were exposed to acid rain spray tests and then subjected to bending fatigue testing. These tests comparatively examined the impact of different stress levels and corrosion ages on the concrete's fatigue life, strain, and damage pattern. Additionally, the fatigue life reliability of the concrete was analyzed using the Weibull distribution theory and equations were developed to predict the fatigue life of the concrete under different probabilities of failure. The results indicate that both stress level and acid rain corrosion age significantly affect the ultimate strain and fatigue life of concrete. High stress levels combined with prolonged acid rain exposure severely degrade the fatigue performance of the concrete. The fatigue life of the concrete follows a Weibull distribution, and the P-S-N curves and fatigue life equations developed based on data from various failure probabilities show a high linear association with values larger than 0.9. These findings can serve as a reference for predicting the fatigue life of concrete in areas affected by acid rain.

Evaluation of the usability of trachydacitic aggregate in rigid pavements in terms of strength and durability

The research presented here investigates the usability of trachydacitic, an unexploited material that occurred in nature, as aggregate in the construction of concrete/rigid pavements under two different curing conditions. These curing conditions are specified as 28 days 20 ± 5 ˚C water curing and combined curing including 3 days 20 ± 5 ˚C water curing + 2 days dry oven curing at 200 ± 5 ˚C. Four different combinations of trachydacitic aggregated concrete as conventional concrete (CC) and high strength concrete (HSC), with steel fiber and fiberless, were produced at different cement and water contents. Mechanical (compressive and flexural strength), durability (freeze-thaw and sorptivity) and surface abrasion properties of studied concretes were tested for each curing condition. Additionally, SEM-EDX and XRD analyses were conducted to investigate the microstructural, elemental and mineralogical changes with curing. According to the test results, the highest compressive and flexural strength were obtained from the DLPB (Trachydacitic aggregated fibrous HSC) as 75,09 MPa and 10,09 MPa respectively after the combined curing process. Moreover, the combined curing process increased the resistance of concrete to freeze-thaw and water sorptivity, while reducing its resistance to Böhme abrasion. Microstructural investigations also revealed that HSCs have a denser structure compared to conventional concretes. As a result, it was determined that the powder form of trachydacitic aggregate, unlike its coarse form, can be used in HSC road pavement construction.

Performance Optimization Approach of Polymer-Modified Asphalt Mixtures with PET and PE Waste

Road infrastructure sustainability and pavement performance may be increased by using waste materials like polyethylene terephthalate (PET) and polyethylene waste (PE waste) in polymer-modified asphalt mixtures. As seen by a more pronounced rise in the softening point, which exceeds 110 °C with 8% PE waste, PET was found to improve the tensile strength, resistance to cracking, and thermal stability of asphalt mixes. PE waste also increases ductility up to 4% PE waste, beyond which the combination becomes more brittle, and dramatically decreases penetration, strengthening the asphalt’s resistance to deformation. Additionally, bitumen treated with PE waste is more workable than asphalt without PET, even though bitumen treated with PE waste had a viscosity of up to 4500 Pa. Complex shear modules decreased as the PE waste and PET content increased. PET, on the other hand, increases the binder’s overall stiffness, elasticity, and tensile strength. Nevertheless, when PET content rises, ductility steadily decreases. Previous studies concentrated on the effects of each component separately, and this paper fills this knowledge gap by investigating the combined effects of PET and PE waste. The results indicate that the highest compressive strength (7.5 MPa) was obtained with 6% PE + 2% PET, while the highest tensile strength (1.40 MPa) was achieved with a balanced mix of 4% PE waste + 4% PET. Additionally, the viscosity of asphalt is increased by PET and PE waste, enhancing its performance at high temperatures. These findings demonstrate how combining PET and PE waste improves the mechanical and thermal characteristics of asphalt, providing a balance between stiffness and flexibility, a crucial feature for durable road materials under a variety of circumstances.

Experimental Testing of Natural Fiber on Asphalt Mix Performance

The performance of road pavements in Indonesia pays great attention to durability and high safety for users, considering the high rate of traffic growth every year. Utilizing natural fibers which are abundant in Indonesia in a hot mixed asphalt is one solution. This can be an alternative to asphalt content which will protect the pavement from damage, especially the surface layers which experiences collapse due to traffic loads and changes in temperature 20-50 °C. The characterization study of natural fiber in asphalt pavement is critical point for accurate fiber mixing to increase the performance of asphalt as a road surface layer. The objective of this study is evaluation the characterization and performance of three natural fibers namely coconut fiber, rice straw and palm fiber in mixtures of asphalt penetration 60/70. In this study, a mixture of asphalt with natural fibers were produced with a length variation of 2-5 mm. Diameter varied from 0.1-0.7 mm. The variation of fiber size was conducted to determine its effect on the asphalt characteristics. The addition of 0.1%, 0.2%, 0.3%, 0.4% and 0.5% fibers into asphalt pen 60/70 mixture changed the characteristics of the asphalt with wet process mixing 500 rpm in temperature 110oC. The results of characteristic test demonstrate that tensile strength of natural fibers 2.34 – 217.3 N/mm2. The asphalt concrete containing with 0.2% - 0.3% natural fibers showed value of Marshall Stability, Marshall Quotient and Marshall Immersion is significant in of performance asphalt concrete and this method can improve the quality of asphalt mixture.

Utilizing Dual Polarized Array GPR System for Shallow Urban Road Pavement Foundation in Environmental Studies: A Case Study

Maintaining the integrity of urban road pavements is vital for public safety, transportation efficiency, and economic stability. However, aging infrastructure and limited budgets make it challenging to detect subsurface defects that can lead to pavement collapses. Traditional inspection methods are often inadequate for identifying such underground anomalies. Ground Penetrating Radar (GPR), especially dual-polarized array systems, offers a non-destructive, high-resolution solution for subsurface inspection. Despite its potential, effectively detecting and analyzing areas at risk of collapse in urban pavements remains a challenge. This study employed a dual-polarized array GPR system to inspect road pavements in London. The research involved comprehensive field testing, including data acquisition, signal processing, calibration, background noise removal, and 3D migration for enhanced imaging. Additionally, Short-Fourier Transform Spectrum (SFTS) analysis was applied to detect moisture-related anomalies. The results show that dual-polarized GPR systems effectively detect subsurface issues like voids, cracks, and moisture-induced weaknesses. The ability to capture data in multiple polarizations improves resolution and depth, enabling the identification of collapse-prone areas, particularly in regions with moisture infiltration. This study demonstrates the practical value of dual-polarized GPR technology in urban pavement inspection, offering a reliable tool for early detection of subsurface defects and contributing to the longevity and safety of road infrastructure.

Comparative analysis of volume change behavior of expansive road subgrades stabilized with waste paper sludge

Expansive soils have a high tendency for volume change in case of fluctuations in moisture content, potentially causing significant damage to light structures, particularly road pavements. This paper investigates the influence of waste paper sludge (\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:WPS$$\\end{document}) as an alternative sustainable stabilizer on the volume change behavior of expansive road subgrade soils of different origins. For this purpose, \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:WPS$$\\end{document} was added to the expansive soils at ratios of 3%, 6%, 9%, 12%, and 15% by dry weight of the soils. A series of Atterberg’s limit, swelling, shrinkage, compaction, and consolidation tests were performed on pure soils and soil specimens with \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:WPS$$\\end{document} to attain a comprehensive understanding of the role that \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:WPS$$\\end{document} plays in the volume change behavior of expansive soils. The experimental test results showed that the addition of \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:WPS\\:$$\\end{document} led to a considerable decrease in the plasticity and swell-shrink potentials of subgrade soils. The consolidation settlement of expansive road subgrades was also reduced to some extent with \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:WPS$$\\end{document}. Moreover, the statistical analysis of the test data indicated a significant relationship among different swelling-shrinkage parameters. The experimental results presented here suggest that the \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:WPS$$\\end{document} may be a cost-effective, environmentally friendly, and sustainable stabilizer to reduce the volume change sensitivity of expansive road subgrade soils.

Machine Learning Applications in Road Pavement Management: A Review, Challenges and Future Directions

Machine Learning Applications in Road Pavement Management: A Review, Challenges and Future Directions

Chemical structure analysis of chitosan-modified road bitumen after de-icing salt treatment

Asphalt pavements are constantly exposed to many destructive environmental factors including de-icing salts. The problem of the negative effect of salt ions on the performance and consequently the durability of road pavements occurs mainly in temperate climates and regions directly neighboring saline water areas. The salt ions react chemically with the bitumen components, which consequently changes their electronic structure and results in a weakening of the intermolecular interactions occurring between them. Therefore, this study focused primarily on an investigation into the potential for inhibiting the destructive erosion process of bitumen by its modification with chitosan. Studies involving changes in the acidity of the eroding solution as well as chemical and surface properties of the eroded bitumen were carried out for three different salts (NaCl, MgCl2, CaCl2) at varying concentrations, i.e. 5%, 10%, 15% (w/w) after 7 and 28 days of erosion process. Main findings demonstrate that chitosan prevents negative changes in the bitumen physico-chemical properties occurring during the salt erosion process. This effect is especially visible for the bitumen eroded with a solution of MgCl2 and CaCl2. For these salts, chitosan biopolymer reduces the introduction of Cl− ions into the bitumen-building hydrocarbon structures and formation of C–Cl bonds, which is demonstrated by a reduction in the pH changes of the eroding solutions. In addition, chitosan biopolymer inhibits leaching of organic matter from the bitumen, prevents C = O groups formation and reduces the negative effects of de-icing salts on the cohesion energy of the bitumen.

Geosynthetic-stabilized aggregate: quantitative modulus evaluation via Bender Element

Geosynthetics, mainly geogrids and geotextiles, are commonly used to mechanically stabilize unbound aggregate layers in paved road applications. They provide lateral restraint to aggregates to initially increase the layer modulus during construction and minimize its time-dependent decrease under vehicular traffic loading. Different types of geosynthetics may provide different improvement mechanisms and stiffness enhancement levels. Quantitative evaluation of various stabilization geosynthetics is presented herein to compare modulus improvement trends and help incorporate geosynthetic benefits into state-of-the-art mechanistic-empirical (M-E) pavement design procedures. Five geogrids (three extruded, one woven, and one welded) and two geotextiles (one woven and one nonwoven) were studied with a dense graded aggregate in laboratory triaxial testing. Geosynthetics were placed at specimen mid-height and three pairs of Bender Element (BE) sensors were placed at various heights above the geosynthetic to collect shear waves and quantify the degree of mechanical stabilization during resilient modulus testing. While resilient moduli did not distinguish effectiveness of different geosynthetics, shear wave measurements could clearly show local stiffness increases achieved with geosynthetic inclusions. Meanwhile, trends observed in shear modulus profiles at various distances from the geosynthetic, when compared to that of control specimen, properly established the modulus enhancement level achieved in mechanical stabilization with geosynthetics.

Crop-raiding by wildlife and cropland abandonment as feedback from nature-based solutions: lessons from case studies in China and Nepal

Abstract Conservation efforts under the nature-based solutions (NbS) framework aim at better management of ecosystems and improvement of human well-being. Policies targeting forest-based livelihoods align well with the NbS principles, but their social-ecological outcomes are often confounded by complex human-environment interactions. In this study, we identify one major feedback effect of the ecosystem dynamic on people’s livelihoods based on datasets collected from two study areas in China and Nepal. Our methodology integrates satellite remote sensing, household surveys, and statistical models to investigate households’ cropland abandonment decisions under the influence of crop-raiding by wildlife. Results show that cropland parcels that have experienced crop-raiding are more likely to be abandoned in the following years. The more damage the crops have suffered on a given parcel, the more likely it is that the parcel will be abandoned. Parcels in proximity to natural forests, farther away from the house location, and with poorer access to paved roads bear a higher risk of being abandoned. These effects are robust and consistent after controlling for multiple parcel features and household characteristics at different levels and using the dataset from each study area separately. We conclude that policymakers need to consider this undesirable feedback of the ecological system to the livelihoods of local people to better achieve co-benefits for ecosystems and human society.

Exploration of Bituminous Materials Using 2D Electrical Resistivity Imaging, Kurdistan Region, NE Iraq

Solid bituminous materials are widely spread in the Iraqi Kurdistan Region, they are filled so many locations, such as fracture zones, fault planes, and bedding planes. These materials can be used in several industries like pavement road, roofing, bituminous paint and waterproof, etc. The study aims to find an economical quantity of these materials by using 2D resistivity imaging in three locations that are different in geology and tectonic settings. These locations are Alla Syaw, Mera De, and Nasalih villages. The data are collected using Syscal R1 plus resistivity meter, for the sake of following up horizontal and vertical extension of these materials Wenner-Schlumberger array is used with 72 electrodes and a spacing interval of 5 m. Three profiles were conducted for each location, which have lengths equal to 360 m. The data processing was carried out by using the RES2DINV, and the smoothness was performed using finite difference forward modeling. The results show that all the bituminous materials are detected in shallow depths and only in the sandstone layers of the Tanjero, Gercus, and Injana formations filling the fracture zones and fault planes. This is also attributed to the more brittle behavior of the sandstone layer than other layers of these formations which deforms easily by applying external stresses. In the Tanjero Formation bituminous body is detected at a depth of about 10 m, which has an extension of more than 50 m from profile-1 to profile-2 (this is a lateral extension). The average width and height of the body are about 8m and 20 m, so it forms an approximate total volume equal to 8000 m3. The study concludes that the preliminary estimation of the total volume of the detected bituminous bodies is about 20000 m3, which has great importance as raw material for different industries. The bituminous material has a high resistivity value in most of the profiles reaching more than 200 ohm.m.

Calculation of the Number of Roller Passes When Strengthening Roads Using Recycled Asphalt Granulate

Statement of the problem. Work during the repair, overhaul and reconstruction of highways involves the destruction of old asphalt concrete pavement using the cold milling method. The resulting discrete material is used to strengthen roadsides, and if it is regenerated, it is used to construct base layers and lower layers of covering. The compaction of layers of road pavement is carried out with rollers, the efficiency of which depends on the properties of the resulting material, the power parameters of the rollers, and the technology of work, determined by the number of passes of the roller along one track. Analysis of the work showed that there are no substantiated recommendations for determining the number of roller passes taking into account the properties of the material being compacted. Establishing such dependencies makes it possible to clarify the composition of the compaction machine link when installing structural layers of road pavements while ensuring the required quality of work. Results. Analytical dependencies are presented for calculating the deformation modulus and rigidity of a layer of processed asphalt granulate under load, taking into account the thickness of the layer and the size of the fractions. The stresses under the rollers were determined for different types of rollers and their operating modes, taking into account the technical characteristics. The results of a study to determine the number of roller passes when installing a layer of recycled asphalt granulate are presented, taking into account the size of the fractions and the characteristics of the rollers used. Conclusions. It has been established that both the deformation modulus and the rigidity of the compacted layer can be taken as a criterion when choosing the parameters of the rollers and determining the number of passes of the roller along one track. Based on the results obtained, we can conclude that for a given value of the deformation modulus and the stiffness coefficient of the compacted layer of asphalt granulate, it is possible to determine the number of passes, the type of roller and its operating mode to ensure the required characteristics of the layer.

Potential application of by-products from the construction industry and waste from coconuts for concrete road paving blocks: physical and mechanical properties

ABSTRACT This paper analyzes concrete paving blocks (CPB) with mixed recycled aggregates from construction and demolition waste (CDW) as by-products and coconut fibres (CF) as waste, a novelty of these types of blocks, through physical and mechanical characterisation. Then, eighteen mixtures were used to produce rectangular CPB 20 cm × 10 cm × 8 cm (length × width × thickness): three without CDW and CF (with natural aggregate), six with CDW materials (3 replacing natural aggregate by weight in 50%, and other 3 in 75%), three with CF (adding a percentage of 0.1% by concrete weight), and six with CDW materials and CF. Tests, such as visual inspection, water absorption, voids, and compressive strength at 7 and 28 days, were done for blocks CPB with three water/cement ratios of 0.63, 0.73, and 0.83. The results showed that the mixes with different uses of CDW and CF behave better than the equivalent reference mixtures. Then, the study supports the CPB with CDW materials and CF can be used on light motorised trafficked road pavements.

Boundary Layer Modelling of Flow Acceleration and Energy Transfer Effects in Smart Pavement Design

The integration of remote technology into the construction industry has advanced the emergence of smart, self-learning infrastructure across all levels of land transportation design and development. However, energy harvesting capabilities for smart road ventilation purposes have not yet been fully researched as the world gravitates towards energy sustainability. This study thus presents a mathematical investigation of the self-draining design potentials of road pavements, leveraging on energy absorption and conversion to accelerate conductive and convective ventilation of these pavements during wet conditions, as a means of ensuring the skid resistance and safety of such pavements are not compromised. Applying numerical methods with the aid of commercial software code MATLAB®, the classical physics of fluid-surface interaction was used to model accelerated drainage of microflood off paved surfaces through methodical modification of the thickness of the boundary layer associated with the flow regime over the flat road surface. Results indicate significant influences of energy exchange, thermal, and viscous diffusivity on flow acceleration. Alterations in parameters such as the slip factor, thermally induced Brownian motion or phoretic characteristics of the fluid particles at the boundary induce accelerated flow at the surface of the pavement. The findings contribute to the advancement of smart infrastructure by offering practical insights into the potential benefits of integrating energy-harvesting technologies into road pavement systems. By optimizing flow acceleration mechanisms, smart pavements can play a crucial role in improving road safety and sustainability in urban environments.

Improvement of Mohr-Coulomb criterion for designing pavements of roads of low traffic intensity

Improvement of Mohr-Coulomb criterion for designing pavements of roads of low traffic intensity

Comparison of Rigid Pavement Planning Using PD T-14-2003 and NAASRA 1987 Methods in Industrial Areas

As vital infrastructure, roads are a means of transportation access and function as a distribution route for goods and services. Road pavement plays a crucial role in highway construction, necessitating proper planning according to Indonesian standards and planning criteria to ensure smooth land transportation and provide comfort and safety for its users. This study aims to provide information on road conditions, drainage dimensions, and construction costs. Planning is crucial in every road construction design, particularly for rigid pavement, based on survey data collected from the road section. Numerous methods exist for calculating the design value of rigid pavement. We use the Pd T-14-2003 method and the NAASRA 1987 method (National Association of Australian State Road Authorities) to plan rigid pavement thickness in the industrial area of PT. Bukit Muria Jaya Kudus. The Pd T-14-2003 method yielded a JSKN of 4x107 and a CBR of 35% for the subgrade, resulting in a plate thickness of 150 mm. While the Naasra 1987 planning method achieved a JSKN of 6x107 and a CBR of 35% for the base soil, a plate thickness of 160 mm was obtained with a value of K = 80 kPa/mm. The reinforcement planning using the Pd T-14-2003 and Naasra 1987 methods involves longitudinal reinforcement D10 mm at a distance of 150 mm and transverse reinforcement D10 mm at 250 mm. The drainage dimensions at the cross-section location are width x height (1 m x 1 m), and the guard's height is 0.2 m.

Mechanical, Durability, and Microstructure Characterization of Pervious Concrete Incorporating Polypropylene Fibers and Fly Ash/Silica Fume

Pervious concrete, because of its high porosity, is a suitable material for reducing the effects of water precipitations and is primarily utilized in road pavements. In this study, the effects of binder-to-aggregate (B/A) ratios, as well as mineral admixtures with and without polypropylene fibers (PPFs) (0.2% by volume), including fly ash (FA) or silica fume (SF) (10% by substitution of cement), on the mechanical properties and durability of pervious concrete were experimentally observed. The experimental campaign included the following tests: permeability, porosity, compressive strength, splitting tensile strength, and flexural strength tests. The durability performance was evaluated by observing freeze–thaw cycles and abrasion resistance after 28 d curing. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermal analysis (TGA-DTA), and scanning electron microscopy (SEM) combined with energy dispersive spectroscopy (EDS) were employed to investigate the phase composition and microstructure. The results revealed that, for an assigned B/A ratio identified as optimal, the incorporation of mineral admixtures and fibers mutually compensated for their respective negative effects, resulting in the effective enhancement of both mechanical/microstructural characteristics and durability properties. In general, pervious concrete developed with fly ash or silica fume achieved higher compressive strength (>35 MPA) and permeability of 4 mm/s, whereas the binary combination of fly ash or silica fume with 0.2% PPFs yielded a flexural strength greater than 6 MPA and a permeability of 6 mm/s. Silica fume-based pervious concrete exhibited excellent performance in terms of freeze–thaw (F-T) cycling and abrasion resistance, followed by fiber-reinforced pervious concrete, except fly ash-based pervious concrete. Microstructural analysis showed that the inclusion of fly ash or silica fume reduced the harmful capillary pores and refined the pore enlargement caused by PPFs in the cement interface matrix through micro-filling and a pozzolanic reaction, leading to improved mechanical and durability characteristics of pervious concrete.

The long-term re-cementation of recycled concrete aggregate in road sub-base and its impacts on pavement performance

Recycled concrete aggregate (RCA) can be used as a pavement sub-base or base material, but the re-cementation of RCA raises concerns about its engineering properties and its impacts on pavement performance. This study investigated the long-term re-cementation phenomenon of RCA that has served for 13 years in road pavements, and the effects of this phenomenon on the RCA’s physical, chemical and mechanical properties. Subsequently, the study also examined the impacts of RCA re-cementation on pavement response and performance using a novel random modulus field technique. It was found that the RCA modulus rises roughly in a power law with the increase of service time, indicating a continuous re-cementation process of this material. The re-cemented RCA particle has a porosity of about 7.8 %, anticipated to be lower than that of new unbound RCA. The net-shaped structures were found near the air voids, which is caused by the newly generated cementation crystals in re-cementation. The new mortar has a lower hardness value than that of the ordinary concrete mortar, but the overall strength of the re-cemented RCA is comparable to that of the cement-treated base. In a pavement structure, re-cementation decreases asphalt layer strain and subgrade strain, helping lower the bottom-up cracking and permanent deformation. However, severe re-cementation increases the risk of reflective cracking. In addition, large-size re-cemented particles increase the variations of pavement responses and thus bring additional uncertainties to pavement performance predictions. To mitigate this concern, limiting the fine aggregate (<0.6 mm) content in RCA is an effective solution since this component is closely related to re-cementation.