This review explores the efficacy of nanomaterials as sustainable alternatives to conventional subgrade soil stabilizers, driven by advancements in nanotechnology over the past two decades. It examines the impact of various nanoparticles on key soil engineering properties, including compaction, California Bearing Ratio (CBR), compressive and shear strength, and swelling-shrinking behaviour. The study also analyzes nanoparticle-soil interactions at micro and nano scales, highlighting their role as primary additives or secondary activators in enhancing soil strength and stiffness. Ecological and geo-environmental concerns associated with nanoparticle use are critically reviewed, alongside potential future research avenues. Findings indicate that nanoparticles significantly improve subgrade mechanical properties, reduce settlement, and absorb heavy metal pollution while maintaining pH balance. Their filling capacity and gel formation enhance bonds, adhesion, and friction angles, with effectiveness varying by nanoparticle type, dosage, and soil characteristics. This study offers valuable insights into eco-friendly nanoparticle applications in road engineering.

Biochar provides a sustainable carbon sequestration technology, an effective fertilizer in agriculture, a step forward for the profitable and safe disposal of bio-wastes, reduced carbon dioxide emissions and global warming, and a renewable energy source. Using biochar as a bitumen modifier in asphalt pavement construction is under active research. It can prove a sustainable and environmentally friendly alternative, provided it meets the efficiency, strength, and economy challenge. This review focused on the available literature on utilizing biochar as a bitumen modifier for the construction of asphaltic roads. The studies show that biochar's physical and chemical nature has helped project it as a promising bitumen modifier. The biochar, being porous and fibrous, provides a strong, stiff frame in the asphaltic mast and results in the enhancement of both stiffening point and viscosity. This, in turn, leads to a reduction in penetration or increased deformation resistance. This is perhaps the reason for the high performance of biochar-modified asphalt at high temperatures. The increase in viscosity of asphaltic masts was also observed due to biochar amendment, making asphalt more sensitive to temperature. The two important factors, the complex modulus and the rutting factor of the asphalt, were noticed to increase with the addition of 10% biochar. The biochar amendments of up to 20% increased fatigue resistance temperature by 4.6 degrees C. The improvement in the resistance to deformation at high temperatures, probably due to a reduction of phase angle due to adding biochar, is also seen as a significant function of biochar. However, biochar applicability in the field is mainly related to its cost efficiency and performance as a bitumen modifier for asphaltic pavements. So far as the cost economy is concerned, the mean price for biochar (as per available literature) was very high, from $2.65 to $0.09/kg for blended biochar. The price was as high as $3.29/kg in the Philippines to $0.08/kg in India and in the US to $13.48/kg, implying that the market price of biochar is variable worldwide and dependent mainly on the biochar feedstock, cost of labor/living of the area and land costs. On the other hand, its efficiency has not yet been satisfactory at low temperatures. The other noticeable limitations that need to be explored in further research are long-term effects on strength, rutting resistance, and ageing. Also, field studies to support the research and, more importantly, cost economy viz-a-viz other available modifiers need exploration.

The behaviour of unbound granular materials (UGMs) used in road construction is crucial in determining the longevity and performance of road pavement. Geotechnical analysis can assist engineers in selecting suitable materials and designing road pavements that meet industry standards. This paper presents the results of laboratory geotechnical tests conducted on unbound granular materials (UGMs) collected from three sites (Roses Gap, Rules East, and Polkemmet Road) in Horsham, Victoria, Australia. UGMs were investigated for their mechanical behaviour and suitability as subgrade materials for road pavements. The study utilised laboratory geotechnical tests, including particle size distribution (PSD), Atterberg limits, compaction (Proctor) test, unconfined compressive strength (UCS), California Bearing Ratio (CBR), and repeated load triaxial (RLT) tests, to evaluate the physical and mechanical properties of the UGM samples. The study indicates that UGM samples collected from different locations displayed variations in their geotechnical properties, such as particle size distribution, water absorption, and CBR strength. Roses Gap samples showed weak cohesion properties, and significant vertical displacements after repeated triaxial tests. However, among the samples in this site, samples with higher clay content (RG21) demonstrated the most promise in triaxial tests. Similarly, the Rules East samples were found to be suitable for low-traffic subgrades due to their satisfactory CBR and RLT testing results, albeit with little cohesion from clay content. Out of three locations, Polkemmet samples were identified as potential subgrade applications, with PR12 being the top recommendation overall. It satisfied PSD, CBR, and RLT test conditions due to acceptable particle size in the largest range, highest CBR strength value, and lowest permanent displacement. The study's findings provide useful information for the design of road pavements using these materials and the characterisation of rural materials around the Horsham region for future use in various other contexts.

Brazil stands out as one of the largest mineral producers in the world. However, this economically important activity also causes significant damage to the environment. The disposal of mining waste in dams gained great repercussions after the disasters in Mariana, in 2015, and Brumadinho, in 2019, that the need to find a new use for these materials arose. The main objective of the research was to evaluate the addition of iron ore waste to materials used in the base and sub -base layers of road pavements. The results of the mechanical tests demonstrated that it is technically feasible to introduce iron ore waste into the soil-cement mixtures used in the base and sub -base layers. It was found that a minimum of 6% cement in soil-cement mixtures for the base layer, and 5% and 4% for the sub -base layer, are sufficient for the addition of waste. This indicates that waste can be an excellent alternative to reduce cement consumption. This incorporation could reduce the consumption of natural resources, offer an alternative destination for mining waste and even reduce the costs of paving works. With this research, we seek an intelligent and sustainable solution to the impacts caused by mining tailings in Brazil.

The most important factor in increasing the efficiency of the development of forest tracts is the development and improvement of the transport and operational condition of the network of logging roads. Inert road construction materials, such as sand, crushed stone, crushed stone -sand mixture or gravel -sand mixture, are traditionally used for the construction of pavements for logging roads. However, in the areas with a shortage of these materials, the cost of road construction increases significantly. An alternative technology that can significantly reduce or completely eliminate the use of inert road construction materials is the stabilization of local soils for the construction of pavement structural layers. The soil stabilization technology consists in mixing them with binders and compacting them at the optimal moisture content of the mixture. In doing so, the resulting material acquires the desired strength and frost resistance. The most effective and common binder for soil stabilization is Portland cement. However, along with high strength properties and frost resistance, cement soils, due to their crystalline structure, have low crack resistance, which worsens transport and operational performance and shortens the service life of road pavements. One of the rational solutions for increasing the security of soil stabilization for the construction of road pavements is the installation of fiber cement soil layers. The object of this research is fiber cement soil for the construction of structural layers of road pavements for logging roads. The aim is to improve the physical and mechanical properties and frost resistance of soils stabilized with Portland cement with the addition of the material based on basalt fiber. Laboratory tests of compressive and tensile strength during splitting, as well as frost resistance of fiber cement soils of various compositions were carried out in accordance with GOST R 70452-2022. According to the data obtained, fiber cement soil has higher strength and frost resistance compared to cement soil. The fibers distributed throughout the cement -soil matrix effectively perceive external loads, providing high physical and mechanical indicators, and therefore crack and frost resistance of the material. The use of fiber cement soil for the construction of pavements for logging roads will increase the durability and reliability of their operation, as well as reduce the costs of construction and operation of road transport infrastructure of forest tracts.