Road Base Research Articles

Mechanical Properties and Microscopic Mechanism of Steel Slag, Sodium Sulfate and Cement Stabilized Road Demolition Waste

When recycled aggregate (RA) from road demolition waste is used as a road base, its engineering performance tends to be poor and requires stabilization. Cement is the most commonly used stabilizer, but it is a high energy consuming product. Therefore, in this article, steel slag powder (SP) and sodium sulfate (SS) are used to replace part of cement to stabilize crushed stone (RCS). The effects of SP content, SS content and curing age on the mechanical properties and microstructure of cement stabilized aggregates were studied using unconfined compression, triaxial shear, Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR) and X-ray diffraction (XRD) tests. The results show that appropriate SP and SS adding improve the compressive strength of RCS, and the RCS strength reaches its maximum when the SP content was 10%. Moreover, the SS addition can further enhance the strength of cement+SP stabilized RA, a maximum strength was obtained when the SS content is 1.5%. The shear strength of specimen was enhanced by SP and SS its increasing its cohesion. SP promote the hydration reaction and fills the pores in the RCS specimen, while SS can stimulate SP to accelerate the SP hydration reaction in the SP stabilized RCS specimen, thus further improving the strength of the stabilized RA, and generating gels such as C-S-H gel, C-A-H gel, C-A-S-H gel in the cement stabilized RA with SP+SS powder.

Effect of ionic soil stabilizer on the properties of lime and fly ash stabilized iron tailings as pavement base

The large use of iron tailings is in urgent need given its huge emissions and pollution to environment. This paper sought to utilize a large quantity of iron tailings with fly ash and lime to prepare road base materials, and use ionic soil stabilizer (ISS) to improve its pavement performance. Different dosage ISS content of was added to the lime-fly ash stabilized iron tailing materials to improve the mechanical strength, frost resistance properties and decrease the dry shrinkage. The results show that the UCS of the specimen with 0.67 % ISS represents enhancement of 195.5 % compared to the control sample at 7 d. After undergoing 15 freeze-thaw cycles, the residual UCS ratio remains at 76.6 %, whereas the control sample exhibits signs of failure. Additionally, the dry shrinkage strain at 30 d was 66.3 % lower than that of the control sample without ISS. The mechanisms underlie that the adsorbed ISS onto iron tailings can reduce the repulsion between total fine particles by lowering the general zeta potential, thus decreasing the porosity of the road base materials. Besides, the ISS can hinder the phase transformation from ettringite (AFt) to monosulfoaluminate (AFm) and its hydrophobic groups can prevent the infiltration and migration of water. The findings reveal that ISS significantly enhances the pavement performance of the stabilized iron tailings, thereby presenting a novel approach for the incorporation of iron tailings in road construction endeavors.

The Use of Waste Materials Red Mud and Fly Ash as Road Embankment Fill

This study provides a comprehensive evaluation of red mud as a sustainable material for road base construction, particularly in combination with bottom ash. Red mud, a by-product of the Bayer process used in alumina extraction, is known for its high alkalinity and heavy metal content. For this reason, this waste material causes environmental challenges. Red mud sourced from the Eti Aluminum Factory in Seydişehir, Konya (Turkey), was stabilized with bottom ash. Then, these waste materials were tested through a number of experiments, such as in relation to their Atterberg limits, compaction characteristics, unconfined compressive strength (UCS), California bearing ratio (CBR), and microstructure through a scanning electron microscopy (SEM) analysis. The results highlight that the UCS of stabilized red mud samples significantly improved with the addition of bottom ash and longer curing periods. Specifically, the UCS values increased from 0.5 MPa to 2.5 MPa after 28 days of curing. Moreover, RM specimens stabilized with 25% bottom ash achieved a CBR value of 146.64% after 28 days, far exceeding Turkey’s road fill material requirement, which mandates a minimum unsoaked CBR value of 15%. These findings indicate that red mud stabilized with bottom ash not only meets but exceeds the structural requirements for road base materials. This approach provides a sustainable solution for the environmental management of red mud while contributing to infrastructure development. Through the recycling of these industrial by-products, this study presents a viable method to reduce waste and support economic and environmental sustainability in road construction projects.

Performance of Bitumen Emulsion Mixtures utilized as Gravel Road Base incorporating Lateritic Clay Soil and Calcined Sugarcane Bagasse Ash Filler

Performance of Bitumen Emulsion Mixtures utilized as Gravel Road Base incorporating Lateritic Clay Soil and Calcined Sugarcane Bagasse Ash Filler

Blending phosphogypsum to mitigate radionuclide leaching for sustainable road base applications

Production of phosphoric acid generates a calcium sulfate byproduct known as phosphogypsum (PG). PG is not considered a suitable standalone road base material because of concerns such as strength and presence of radionuclides. This paper investigates the latter, specifically the influence of blending PG with common alkaline road base aggregates – limerock (LR) and recycled concrete aggregate (RCA) – on radionuclide leaching. Radionuclide leaching from several PG sources was assessed for gross alpha, gross beta, uranium, and combined radium (226 + 228). Solution pH affected Ra226 mobility, with minimum concentrations exhibited at a pH in the range of 6 to 8. Mobile Ra226 concentrations in RCA blends decreased compared to original PG; Ra226 mobility initially increased at low LR replacements but decreased with increasing mass of LR (50 %–75 %). The data suggest an additional mechanism beyond pH alone impacted Ra226 mobility from the blends, possibly the binding or substitution of radium by elevated concentrations of Ba, Sr, or Ca. Blending with RCA resulted in radionuclide concentrations below respective drinking water thresholds, mitigating leaching concern from PG-RCA road base blends. PG-LR blends can meet regulatory limits when incorporating appropriate PG sources, providing an avenue for PG-amended road base materials. The blending approach reduced Ra226 mobility from PG-amended base, accommodating more PG use, serving as an alternative scenario to end-of-life stacking.

The strength, reaction mechanism, sustainable potential of full solid waste alkali-activated cementitious materials using red mud and carbide slag

Alkali-activated cementitious material (AACM) is a green building material which effectively utilizes industrial solid wastes, such as red mud (RM), ground granulated blast furnace slag (GGBS). However, there are problems with using conventional alkali activators (NaOH, Na2SiO3), including strong corrosivity and high cost. In order to solve this problem, this study prepares full solid waste cementitious materials (FSWCM) by activating RM and GGBS using carbide slag (CS) instead of traditional alkali activator. Based on the response surface method (RSM), the effects of RM content, CS content and water-binder ratio on the performance of FSWCM were studied. The microstructure changes of FSWCM with different RM contents were analyzed by XRD, TG, FTIR and SEM-EDS. The results showed that the optimized content of RM and CS was 40 % and 20 % respectively, and the 28-d compressive strength reached 14.11 MPa, which met the requirements of road base materials. The regression model established by RSM had high accuracy and could accurately predict the performance response values. The alkaline environment created by CS-RM facilitated the decomposition of active components in GGBS, resulting in the formation of a considerable amount of C-(A)-S-H gel via polycondensation. With the increase of age, Na+ dissolved in RM replaced Ca2+ in C-A-S-H to form N-A-S-H gel. The hydration products N-A-S-H, C-(A)-S-H and CaCO3 were intertwined to form a stable and dense three-dimensional network structure, which provided excellent mechanical properties. Sustainability analysis shows that FSWCM has significant advantages in cost control and environmental friendliness compared with AACM.

Freeze-thaw impacts on geocell-stabilized bases considering effects of water supply and compaction

Although Novel Polymeric Alloy (NPA) geocells have been applied to stabilize road bases against the freeze-thaw (F-T) damage in practice, the relevant research lags the application. A scarcity of research has been reported to comprehensively evaluate the benefits of geocell stabilization in enhancing the F-T performance of bases. This study aims to investigate quantitatively the F-T performance of geocell-stabilized bases, focusing on two influencing factors-i.e., water supply and degree of compaction in the bases. A series of model-scale experimental tests (19 tests) was conducted using an upgraded customized apparatus. The results showed that the inclusion of geocells was beneficial for reducing frost heave and thaw settlement as well as mechanical properties (i.e., stiffness and ultimate bearing capacity) of road bases. The benefit of geocells was more remarkable for the well compacted bases than for the poorly compacted bases. The benefit was more pronounced in the open system than in the closed system.

Mechanical properties and microscopic mechanism of solid waste based binder solidified stone waste

The stone waste generated by stone industry occupy land resources, cause safety hazards and need to be efficiently resourcefully utilized. In this study, the CGF solid waste based binder (abbreviated as CGF) with calcium carbide residue (CCR), ground granulated blast furnace slag (GGBS), and fly ash (FA) as components was developed to solidify the stone waste. Through “treating waste with waste”, the resource utilization of solid waste was realized. The mechanical properties and reaction mechanism of CGF solidified stone waste were investigated through unconfined compressive strength (UCS), XRD, and SEM–EDS tests. The results show that CGF has the better solidify effect on stone waste, and its strength meets the requirements of the road base material standards. Compared to cement, the CGF solidified stone waste existed higher UCS at both 7 and 28 d of curing. The UCS of CGF solidified stone waste reaches 2.93 and 4.42 MPa under curing of 7 and 28 d at 5% binder content, which is 1.61 and 1.37 times higher that of P.O. 42.5 cement. Furthermore, the primary mineral-based stone wastes will not react with the binder, and the CGF generates gelling products such as C-S–H C-A-H, and C-A-S–H through alkali-activated reactions between the components of CGF. These gelling products enhance the UCS of solidified stone wastes through cementing and filling effects. The findings provide a feasible approach with low-carbon emission and low-cost for resourceful utilization of stone wastes.

Road Site Inspection and Measures to Avoid Further Deformation

Strength and stability of the roadbed and engineering structures in permafrost conditions and deep seasonal freezing of soils always remain complex scientific, technical and technological problem in construction and reconstruction of roads in northern regions. Particularly important is the spread of subgrade subsidence during construction and further operation and maintenance of roads in these regions. The road destruction is mostly caused by both global warming and geological and hydrogeological conditions.To prevent the deformation development, it is necessary to provide a number of special engineering measures to prevent thawing of permafrost soils or strengthen supra-permafrost layers of foundations. The purpose of the work is to study methods for eliminating deformation of the road bed in permafrost and choosing the main method for eliminating subsidence of the road.The article discusses several ways to solve the problem of eliminating subsidence on of the federal highway. Options for reconstruction of the roadbed are considered. These are different methods of thermal stabilization, i.e., horizontal (sloping) thermal stabilization system with inclined thermal stabilizers, temporary vertical thermal stabilizers for pre-construction freezing of foundation soils, and hybrid thermal stabilization system (horizontal and vertical thermal stabilizer in one product). A method is proposed for stabilizing the road base by installing soil-cement piles. The main advantages of and disadvantages the methods are noted and cost assessment is made. A conclusion is drawn on the effectiveness of different methods to restore the subgrade structure in order to ensure the road base stability. The main method is elimination of subsidence by stabilizing the road base with installation of soil-cement piles.

Durability Performance of CGF Stone Waste Road Base Materials under Dry-Wet and Freeze-Thaw Cycles.

The disposal of stone waste derived from the stone industry is a worldwide problem. The shortage of landfills, as well as transport costs and environmental pollution, pose a crucial problem. Additionally, as a substitute for cement that has high carbon emissions, energy consumption, and pollution, the disposal of stone wastes by utilizing solid waste-based binders as road base materials can achieve the goal of "waste for waste". However, the mechanical properties and deterioration mechanism of solid waste-based binder solidified stone waste as a road base material under complex environments remains incompletely understood. This paper reveals the durability performance of CGF all-solid waste binder (consisting of calcium carbide residue, ground granulated blast furnace slag, and fly ash) solidified stone waste through the macro and micro properties under dry-wet and freeze-thaw cycling conditions. The results showed that the dry-wet and freeze-thaw cycles have similar patterns of impacts on the CGF and cement stone waste road base materials, i.e., the stress-strain curves and damage forms were similar in exhibiting the strain-softening type, and the unconfined compressive strengths all decreased with the number of cycles and then tended to stabilize. However, the influence of dry-wet and freeze-thaw cycles on the deterioration degree was significantly different; CGF showed excellent resistance to dry-wet cycles, whereas cement was superior in freeze-thaw resistance. The deterioration grade of CGF and cement ranged from 36.15 to 47.72% and 39.38 to 47.64%, respectively, after 12 dry-wet cycles, whereas it ranged from 57.91 to 64.48% and 36.61 to 40.00% after 12 freeze-thaw cycles, respectively. The combined use of MIP and SEM confirmed that the deterioration was due to the increase in the porosity and cracks induced by dry-wet and freeze-thaw cycles, which in turn enhanced the deterioration phenomenon. This can be ascribed to the fact that small pores occupy the largest proportion and contribute to the deterioration process, and the deterioration caused by dry-wet cycles is associated with the formation of large pores through the connection of small pores, while the freeze-thaw damage is due to the increase in medium pores that are more susceptible to water intrusion. The findings provide theoretical instruction and technical support for utilizing solid waste-based binders for solidified stone waste in road base engineering.

A Sustainable Reinforcement Method for Recycled Road Subgrade Demolition Waste as Road Bases Using Waterborne Polyurethane and Fiber

A Sustainable Reinforcement Method for Recycled Road Subgrade Demolition Waste as Road Bases Using Waterborne Polyurethane and Fiber

An overview of the angular geomorphic lock – an anti-rutting model for sustainable road infrastructure

Sustainable road infrastructure is largely dependent on the resilience of the road foundation to withstand dynamic stresses. From Empirical to Mechanistic Empirical Pavement Design Guidelines (MEPDG), the use of unbound granular materials (UGMs) has been specified for road foundation bases for flexible roads. Rutting is a common road failure from these designs. MEPDG includes climate change factors that essentially invalidate the empirical approach. However, both design approaches still rely on the anisotropic particle interlock of UGM upon compaction, notwithstanding traditional or intelligent compaction technology. The anisotropic character of compacted UGM only exhibits vertical stiffness with the highest shear stress located in the mid layer. This makes the interface between the surface of the compacted subgrade and the bottom of the compacted subbase incompatible. Consequently, the stiffness of the UGM is satisfactory for static loads, but when these become dynamic, the inter-granular transmission of these stresses creates a new challenge, non-linearity of stress and the ensuing propensity for stress rotation. A model subbase of a road foundation was modified acknowledging the natural angle of repose of UGM. The ribbed saw tooth structure with an inherent composite anisotropic character seemed to offer significant stiffness. A three-point shear stress localisation (3-PSSL) was experimentally created with three stress levels identified within the subbase and a fourth stress level in the base. This geomorphic lock is possible by the use of an angular geo-lock compactor (AGL). Added stiffness in the road foundation should avert rutting, thereby increasing resilience and sustainability of road infrastructure, and ultimately stimulating socio-economic development. World Intellectual Property Organisation (WIPO) has documented this ongoing research as patent No. WO 2021/048590 A1 awaiting entry into The National Phase. This is Work in Progress, where particle intra-lock may invalidate particle interlock.

Mechanical and Microstructural Analysis of Treated Tuff with Metakaolin Geopolymer Cement for Road Base layers Applications

Traditional road bases materials such as natural gravel and crushed stone are environmentally damaging, and there is a growing need for sustainable and eco-friendly alternatives. One such alternative is using geopolymer cement and tuff as aggregate materials. Geopolymer cement is an innovative and environmentally-friendly alternative to traditional Portland cement, and using locally-sourced tuff as an aggregate material can further reduce the environmental impact of road construction. This article discusses the importance of sustainable road construction practices, particularly in the use of eco-friendly materials for road base layers. It focuses on the treatment of tuff with alkali-activated metakaolin as the geopolymer precursor activated with a mixture of sodium hydroxide and sodium silicate. The effectiveness of treating tuff with metakaolin geopolymer cement is evaluated using several parameters, including dry density, California Bearing Ratio (CBR), shear strength, and microstructure analysis. These evaluations are performed with different NaOH dosages (8, 10, and 12 moles) to determine the optimal molarity for enhancing the material's performance.

Durability of geopolymer cementitious materials synergistically stimulated by Ca2+ and Na+

Fewer studies related to the durability of multi-source solid waste geopolymer cementitious materials and the massive accumulation of industrial solid waste are urgent problems to be solved in practice in Inner Mongolia, China. In this paper, blast furnace slag (BFS), fly ash (FA), and calcium carbide slag (CCS) are used as the main raw materials to prepare geopolymer cementitious materials (BFCG) with Calcium Carbide Slag as the Ca-source alkali activator and NaOH as the Na-source alkali activator, considering their durability properties. By assessing the indicators of mechanical performance, engineering performance, and the synergistic mechanism of Ca2+ and Na+ in multi-source solid waste geopolymer, four sets of BFCG ratio optimization schemes are selected. XRD, FT-TR, SEM-EDS, and other testing methods are used to analyze its freeze–thaw resistance and acid–alkali-salt corrosion resistance. The following conclusions are drawn: the BFCG prepared under the synergistic excitation of Ca2+ and Na+ has better resistance to freezing and thawing, as well as acid-alkali-salt corrosion, both of which are in accordance with the standard specifications for road construction in China. After the freeze–thaw cycles, BFCG still has more three-dimensional network-like silica-aluminate structures, a compact micromorphology, and small pores. Its strength loss rate is 0.56 %–15.56 %, the mass loss rate is 0.19 %–1.26 %, and the relative dynamic modulus is 79.56 %–100.25 %. In a NaOH environment, the crystal type of BFCG did not change significantly, and the resistivity coefficients are 115.78 %–143.54 %. In a Na2SO4 environment, the decalcification or dealumination of C-A-S-H gel leads to the formation of a gel rich in silicon, magnesium, and aluminum phases, with a corrosion resistance coefficient of 101.8 %–119.96 %. In a HCl environment, HCl erosion inhibits the growth of hydration product crystals, with corrosion resistance coefficients ranging from 73.83 % to 97.24 %. BFCG-D has the best resistance to freezing and thawing as well as acid and alkali corrosion. BFCG-D has the best resistance to freezing and thawing as well as acid and alkali corrosion. These studies show that BFCG offers a promising solution for improving the durability of road base materials and reducing industrial solid waste.

Mechanical properties and repairing mechanism of recycled cement stabilized macadam for road base based on microbial induced carbonate precipitation technology

The utilization of recycled coarse aggregate derived from construction and demolition waste (CDW) in the construction of road cement stabilized macadam base could effectively alleviate the shortage of natural sand and aggregate resources. To explore the repairing effect of microbial induced carbonate precipitation (MICP) on recycled cement stabilized macadam (RCSM), the physical, mechanical, and microscopic properties of recycled concrete aggregate under different precipitation precursor concentrations were researched in this paper. The mechanical properties of RCSM with varying contents of recycled concrete aggregate were analyzed before and after repairing. Based on scanning electron microscopy (SEM) and mercury intrusion porosimeter (MIP) tests, the microstructure and pore structure parameters of recycled concrete aggregate were explored, and the repair mechanism of MICP on RCSM was revealed via the performance analysis of recycled concrete aggregate and RCSM. The results show that MICP could effectively reduce the water absorption of recycled concrete aggregates, while simultaneously enhancing its apparent density and crushing resistance. In a certain range, the higher the concentration of the precipitation precursor, the better the repairing effect on the performances of recycled concrete aggregates. However, while the concentration of urea or calcium source concentration exceeding 1.0 mol/L, the activity of urease would start to be inhibited. The unconfined compressive strength of RCSM after MICP repairing could be increased by 22.7 % with a maximum extent compared with that before repair, while the maximum increase of indirect tension strength and flexural tensile strength was 15 % and 8.2 %, respectively. The biological CaCO3 generated by MICP reaction could fill the micro-cracks and pores of the recycled concrete aggregate efficaciously. Besides, it could also optimize the pore parameters and pore size distribution parameters, and enhance the adhesive strength of interfacial transition zone (ITZ) between cement and recycled concrete aggregates, which could improve the mechanical properties of RCSM.

Blending as a strategy for using phosphogypsum in granular road base: physical performance and implications

The use of phosphogypsum (PG) as a construction material continues to gain considerable attention worldwide. In the United States(US), the specific use of PG as a road base material has received renewed interest on a federal level. Previous work investigated the use of road base, either PG alone or stabilized with cementitious materials. This study investigated the physical characteristics of compacted PG sources and novel blends with traditional base aggregates compared to industry and state requirements. Specimens were created by blending up to 50% PG from five gypstacks in Florida, US with limerock (LR) and recycled concrete aggregate (RCA). The LBR for PG-LR and PG-RCA blends surpassed bearing strength (LBR) requirements and ranged from 102 to 130% and 155–210% at 50:50 ratios, and increased by 2–60% with decreasing PG content from 50 to 30%. The data suggest success of PG-amended granular base reported here relies largely on the strength of the original aggregate.

Consequential life cycle assessment of demolition waste management in Germany

ContextBulk mineral waste materials such as construction and demolition waste are Germany’s largest waste stream. Despite the availability of high-quality recycling pathways such as road base layers, waste concrete is predominantly recycled into lower-quality recycling pathways like earthworks or unbound road construction. This is due to low demand for recycled aggregates in road base layers and frost protection layers, especially in public procurement.PurposeThis study assesses the environmental consequences of increasing high-quality recycling of waste concrete in the near future to provide decision support for public procurement in Germany. The focus lies on climate change due to its importance for decision-makers. However, 17 other impact categories were assessed to avoid problem shifting.MethodsLife cycle assessment (LCA) is applied with background data from ecoinvent 3.9.1. Impact assessment was conducted at midpoint level using IPCC 2021 and ReCiPe Midpoint (H). Foreground data were taken from literature and expert interviews. In line with the goal of this LCA, a consequential modeling approach was followed to account for changes in the material flow system. Substitution creates a cascade effect previously omitted in consequential LCA studies, in which lower quality recycling materials replace higher quality recycling materials in their respective utilization pathways.Results and discussionIncreasing the high-quality recycling of waste concrete into road base layers causes a reduction in environmental impacts for all 18 impact categories, as it replaces natural aggregate and avoids backfilling of mixed mineral waste and excavated earth through substitution effects. Transport distances and ferrous metal recovery were identified as hot spots. Sensitivity analyses show that only transport is a significant issue.ConclusionIncreasing the high-quality recycling of waste concrete in Germany is recommended in terms of environmental impacts. Lower-quality recycling is environmentally feasible only in cases where the avoided transport distances for natural aggregates and backfilling are significantly lower than the additional transport distances for high-quality recycling.

Geotechnical Assessment of Selected Lateritic Soils in Southwest Nigeria for Road Construction and Development of Artificial Neural Network Mathematical Based Model for Prediction of the California Bearing Ratio

Investigation of the geotechnical characteristics of eighteen different lateritic soils within southwest Nigeria was carried out to determine their suitability for road construction. To achieve this goal, the lateritic soils samples were subjected to different laboratory tests, including specific gravity, Atterberg limits, grain size analysis, California bearing ratio, and compaction, in accordance with the ASTM standard procedure. The results of the tests showed that the specific gravity varied between 2.55 and 2.81; the linear shrinkage varied between 6.68% and 10.98%; the liquid limit varied between 37.17% and 56.93%; the plastic limit ranged from 19.47% to 37.14%; the plasticity index ranged from 3.81% to 30.29%; the fine sand content ranged from 37.07% to 62..93%; the fines content ranged from 36.4% to 60.9%; the maximum dry density ranged from 1747 kg/m3 to 2056 kg/m3 ; the optimum moisture content ranges from 10.94% to 20.51%; the un-soaked California bearing ratio ranged from 14.7% to 45.6%; and the soaked California bearing ratio ranged from 10% to 31%. Based on these results, all the studied soils can be used as road subgrade, while none except Loc.5/S1 is suitable for road subbase. However, none of the soils meets up with the requirement for road base course. The suitability of laterite for the construction of road depends largely on the California bearing ratio. However, laboratory tests for determining the California bearing ratio is tedious, time consuming and costly. As a result of this difficulty, there is a need to develop soft computing models to predict laterite California bearing ratio from index properties with cheap and simple tests. Thus, the experimental datasets of the eighteen studied lateritic soils were used to create and train artificial neural network (ANN) models to predict California bearing ratio from liquid limits, plasticity index, linear shrinkage, fine sand content and fines content. The proposed ANN models were compared with the multiple linear regression models proposed in this study and various regression based models suggested in the literature via statistical analyses. Based on the model comparison, the proposed ANN models outperformed the rest of the models; they presented the highest R 2 and the lowest RMSE, MAPE and MAE values. Thus, the ANN models are validated. To enhance the practical application of the proposed ANN models, they were transformed into simple mathematical equations, which gave the same predictions as the direct ANN models. Thus, they can be used for practical purposes.

Pavement Performance of Fine-Grained Soil Stabilized by Fly Ash and Granulated Blast Furnace Slag-Based Geopolymer as Road Base Course Material

Pavement Performance of Fine-Grained Soil Stabilized by Fly Ash and Granulated Blast Furnace Slag-Based Geopolymer as Road Base Course Material

Compaction behaviour of a sandy road base contaminated with microplastics from vehicle tires

AbstractDisintegrated tire particles can easily be transferred into the road bases because of the abrasion of vehicle tires on roads. The fragmented tire particles that have a grain size of smaller than 5 mm can be expressed as microplastics. In order to simulate the tire chip microplastic concentration in a sandy road base and assess the effect of microplastics on the compaction degree of the road base, standard Proctor compaction tests were performed on 0.05%, 0.1%, 0.2%, 0.4%, 1%, 2%, 4% and 8% tire chip microplastics‐amended sandy soil by dry mass. Results showed that maximum dry unit weight (ɣdmax) of the sand increased from 16.04 to 16.99 kN/m3 as the tire chip microplastic concentration increased up to 0.4%. Further increase in the microplastic concentration resulted in a decrease in ɣdmax. Contrarily, optimum water content (wopt) decreased from 15.9 to 12.5% as a result of the tire chip microplastic addition up to a concentration of 0.4%. An additional increase in the microplastic concentration led to an increase in wopt. By considering these results, a concentration of 0.4% tire chip microplastics was found to be the optimum amount that enhanced the degree of compaction. Besides contributing to the stabilization of a sandy road base, tire chip microplastics can also be assessed in terms of environmental protection. These microplastics are forced to be stacked in the sand because of compaction. As a result, they cannot easily be transferred to water resources or agricultural products that may threaten human health and cause environmental contamination.