Geopolymers have attracted wide attention as effective soil stabilisers, presenting significant potential for several geotechnical engineering applications. These binders offer environmental benefits by utilising abandoned aluminosilicate industrial by-products, such as fly ash and slag, through mixing with an alkaline solution. In addition, they also decrease dependency on conventional Ordinary Portland Cement (OPC), which is identified with substantial artificial greenhouse gas emissions and high energy consumption during manufacture. However, the practical utilisation of geopolymers for the stabilisation of road materials is hindered by the intricate preparation process, which necessitates precise control over the proportions of the ingredients to achieve the required mechanical properties. This complexity becomes more pronounced when compared to the relatively simple method of using conventional cement, which requires fewer safety precautions while mixing with soil. This study investigates the development of a One-Part Geopolymer (OPG) powder, specifically formulated for the stabilisation of a Crushed Rock Base (CRB) material used for road construction. The optimal blend of OPG powder, comprising fly ash, slag and sodium metasilicate, is identified by assessing the monotonic and dynamic mechanical performances of the treated CRB compacted at the optimum moisture content using Unconfined Compressive Strength (UCS) and Repeated Load Triaxial (RLT) tests. The results of the study indicate that enhancing the strength performance of the OPG-treated CRB requires the calibration of the sodium oxide (Na2O) content in the alkaline activator with the total binder. It was also found that increasing the OPG content from 1% to 3% significantly enhances both the uniaxial strength and resilient modulus of the treated CRB, while simultaneously reducing the permanent deformation. Notably, the CRB specimens stabilised with 2% OPG exhibit mechanical properties comparable to those of bound Portland cemented materials.

Nowadays, more and more attention is being paid to environmental issues due to the development of road transportation, particularly the construction of arterial roads. Despite the existence of diverse methods to determine convenient criteria for their assessment, determining the projects with the least harmful effects on the environment and ranking them for purposes of budget allocation and prioritization are remarkably important. The case is more highlighted in regions where roads go through diverse areas with different climatic and geographical distributions. In the present study, a new method consisting of two phases was proposed to determine the optimal coefficient of environmental parameters in road construction parameters. In the first phase, the Genetic Optimization Algorithm was implemented to determine convenient coefficients for the relevant parameters. During this stage, similar coefficients were clustered together. In the second phase, an environmental index for various projects was determined based on the obtained results, and the proposed projects were ranked based on that. According to the results obtained concerning environmental parameters during the pre-implementation stage, polluting water resources was the most influential parameter, with a coefficient determined at 3.59. Moreover, the most significant parameter during the implementation was noise pollution, with a coefficient of 5.89, while damaging the ecosystem was the most significant one during the stage of land use change (5.25). Furthermore, soil pollution was the most remarkable parameter during the stage of maintenance (5.81), while damaging the local climate pollution was the most important one during the stage of road implementation (5.67). The above findings can be helpful for researchers in road construction projects.

In order to reduce the storage cost and avoid environmental hazards of feldspar powder waste from lithium extraction byproducts, this work investigated the feasibility of ordinary silicate cement-stabilized feldspar powder-lateritic clay (FP-LC) composite as road construction material. Firstly, preliminary mix design of the new material was conducted to determine the optimum moisture content and maximum dry density. Subsequently, the effects of ratio of FP to LC on the mechanical properties of the composite were investigated through unconfined compressive strength (UCS), California bearing ratio (CBR) and shear strength tests. Finally, the strength formation mechanism of the FP-LC mixture was analyzed in combination with SEM and XRD testing. The results indicate that the UCS after 14 d curing, CBR and cohesive strength of FP simply stabilized by 6 % cement is 0.95 MPa, 87.3 % and 140.64 kPa, respectively, which can meet the requirements for subgrade materials. The addition of LC significantly improves the mechanical properties of the composite. The mass ratio of 40 % FP to 60 % LC results in the optimal UCS after 14 d curing, CBR and cohesive strength with 1.6 MPa, 164.1 % and 250.16 kPa, respectively, which makes it applicable as subbase materials for medium-light traffic levels. The particle closest packing analysis and SEM and XRD characterization demonstrated that the enhancement of UCS, CBR and shear strength comes from compact arrangement of FP and LC particles and the bonding effect of cement hydration products between them. This work proposes an eco-friendly and sustainable utilization approach of feldspar powder from lithium extraction byproducts as road construction material, which are important to overcome the challenges of both waste management and resource shortage for new energy and highway industries, respectively.

This study has focused on the dam sediments and marble waste reuse as subgrade materials for road construction, with the overarching goals of reducing greenhouse gas emissions and conserving natural resources. Different mixtures were prepared based on sediments and marble waste, and treated with hydraulic binders. The first mixture consisted solely of raw sediment, while the second mixture combined 50 % dredged sediments with 50 % marble waste. Additionally, this mixture was treated with 1 % aerial hydrated lime and hydraulic road binder to enhance its properties. The experimental study focused on assessing both the short-term and long-term mechanical properties of the prepared mixtures. Results highlighted that the mixtures containing dam sediments and marble waste were highly suitable for road subgrade construction. These mixtures satisfied the criteria for trafficability (UCS), wetting resistance (UCSI), freezing resistance (ITS), and overall mechanical strength. Furthermore, a comprehensive analysis of the mixtures' microstructure and their environmental impact was conducted. A significant relationship was observed between CaO/SiO2 ratio and the mechanical properties of the treated mix. The research contributes to the growing body of knowledge regarding sustainable construction practices by highlighting the viability of utilizing dredged sediments and marble waste as valuable resources in road subgrade construction. The study showed that recovering 20 % of sediment and marble waste to replace natural materials would reduce energy consumption and greenhouse gas emissions by at least 40 % and 28 % respectively.

Introduction.The use of bitumen microdispersed emulsion as a resource-saving method for road surface construction is a popular trend in the development of innovative nanostructures. The technological use of petroleum bitumen as a binder for road materials requires a reduction in rheological viscosity. This can be achieved through synergistic developments that involve the use of various additives and modifiers. Methods and materials. The composition of bitumen microheterogeneous emulsions includes: bitumen-containing raw materials (up to 70-80% of mass); water with hardness up to 6 mg-eq/l (from 20 to 30%); emulsifiers (up to 3%) and other components. For large-tonnage production of water- bitumen emulsions, a colloid mill is the most technologically advanced equipment. Results. Water-bitumen emulsions are formed as a result of two competing processes: crushing (dispersion) and coalescence (merging) of microdroplets of the bitumen dispersed phase.The microheterogeneous bitumen phase is distributed in the aqueous dispersion medium in the form of microdroplets ranging in size from 1 to 10 mu m (the main share is made up of bitumen microdroplets with a diameter of 2-4.5 mu m). The synergetic durable microstructure of asphalt concrete road surfaces, which is formed by supplementing interaction in the boundary layers of the bitumen binder with the surface of the mineral component, is determined by the dominant interaction of complementary factors. Discussion. The synergetic approach to extending the service life of asphalt concrete road surfaces by using bitumen microdispersed emulsions holds promise for interpreting their evolution. The road construction industry of the Russian Federation at the beginning of the 21st century is characterized by a large-scale revision of regulatory documents, regulating the requirements for the construction and operation of highways. Conclusion.The optimal solution to the current problems of intensive construction and reconstruction of Russian highways is the improvement of technological characteristics of road surfaces by adding bitumen microdispersed emulsions to the composition. In complementary strengthening of weak soils of the road surface of high-speed highways, the use of water-bitumen microdispersed emulsions is also recommended.