The leaching of excessive heavy metals (HMs) from lithium slag (LS) presents a significant challenge for its use in road engineering, necessitating the development of safe treatment methods. This study employed solidification/ stabilization (S/S) technology to develop a magnesium slag-lithium slag composite solidified material (MS-LS). The deformation and displacement characteristics of MS-LS during destruction were analyzed using digital image correlation (DIC). Various microscopic analytical techniques were used to analyze the stabilization mechanisms of MS-LS towards HMs. Results indicated that adding MS significantly improved the compressive strength and resistance to cracking of MS-LS. The minimum strength of the 8 %-MS group reached 2.7 MPa, meeting the strength requirements for subgrade stabilized soil in a first-class highway under heavy traffic load conditions. The development of strength is attributed to improved structural compactness from particle micro-gradation effects and the cementitious hardening action of C-S-H gel. HMs immobilization was achieved through directional adsorption at active sites within the calcium-rich mineral phase and interlayer adsorption within the C-S-H gel, complemented by a physical encapsulation mechanism that reduces HMs leaching. The immobilization rates of Be(II) and Pb(II) in the 8 %-MS group exceeded 95 %, demonstrating the effectiveness of MS in stabilizing these HMs in LS.

This study evaluates styrene butadiene rubber (SBR) and styrene acrylic latex (SA) as modifiers in cement-treated subbase materials (CTSB) to enhance mechanical properties and reduce cement usage sustainably. Optimal ratios for stabilizing sub-standard lateritic soils were identified, reducing water demand and increasing mechanical strength in polymer-modified cement pastes. A 10 % SA and a 15 % SBR as cement replacement by mass significantly improved bearing strength and strain capacities in CTSB, signifying enhanced flexibility and elasticity. Despite slight changes in compaction characteristics, the study identified 1.6 % SA and 2.4 % SBR as optimal binder (i.e., polymer-cement mixture) contents, compared to 3.3 % cement for conventional CTSB with similar unconfined compressive strength standards. SBR-enriched CTSB exhibited superior resilient modulus, indicating stronger inter-particle bonding. The integration of SA and SBR reduced capillary rise and enhanced moisture stability. This sustainable approach enhances pavement durability and reduces CO2 emissions by minimizing cement use. The findings emphasize the potential of polymer-modified CTSB for cost-effective and environmentally friendly road construction, offering significant implications for advancing pavement engineering materials and promoting eco-friendly practices within the industry.

In this study, geopolymer was adopted as an eco-friendly binding material to solidify waste drilling mud to fabricate geopolymer solidified waste drilling mud (GSWDM) as a pavement material in the subbase. Using precursor dosage, Na2SiO3 solution dosage, and slag powder (SP) dosage as parameters of mix proportion, the optimal mix proportions of GSWDM were determined through compressive strength tests. Based on a series of tests of unconfined compressive strength, splitting tensile strength, elastic modulus, and compressive resilient modulus, the effects of the SP percentage in the precursor and curing age on the mechanical properties of GSWDM were analyzed. The results indicated that all the mechanical properties of GSWDM were improved with the increasing SP percentage in the precursor. The 28-day unconfined compressive strength, splitting tensile strength, elastic modulus, and compressive resilient modulus of GSWDM were improved by 80.8%, 56.3%, 65.3%, and 76.72%, respectively, when the SP percentage in the precursor increased from 60% to 100%. A nonlinear increase in the mechanical properties of GSWDM was observed as the curing age increased, with a significant increase in the curing age from 7 days to 14 days and a slight increase in the curing age from 14 days to 28 days. Moreover, the microstructure of GSWDM was denser as the curing age and the SP percentage in the precursor grew. The results of this study verified that GSWDM can be used as construction material for road subbase.

To foster the sustainability of green construction materials utilized in transport infrastructure and generally in soil stabilization for the same purpose, there have been continued efforts towards innovative results for consistent improvement of the mechanical properties of soils. Metakaolin (MK) has been in use as a supplementary material due to its pozzolanic properties. However, it has always produced a limit beyond which there is recorded decline in its ability to cement and strengthen soils in a stabilization protocol. In this research work, a new innovative cementitious material made from 1:1 NaCl + NaOH blend activator mixed with sawdust ash called Ashcrete (A) has been introduced. It is blended with MK in the lateritic soil stabilization procedure. Preliminary results showed that the lateritic soil (LS) has weak consistency with plasticity index above 17%, maximum dry density (MDD) of 1.77 g/cm3 and classified as A-7 soil on American Association State Highway and Transportation Officials (AASHTO) method. The MK and the Ashcrete (A) showed high compositions of aluminosilicates qualifying them as supplementary cements. The MK was used at the rate of 3, 6, and 9%, while the Ashcrete (A) was incorporated at the rate of 2, 4, 6, 8, and 10%. The results of the stabilization exercise showed that the California bearing ratio (CBR) and unconfined compressive strength (UCS) consistently increased with the addition of MK + A blend. This outcome was a shift from the previous work, which had used only MK and recorded 6% addition at which the MK-treated lateritic soil recorded its highest strength, and beyond this mark, there was a decline. The highest strength in this research work was recorded with the stabilization pattern of LS + 9%MK + 10A, which translates to that for a 200 g LS to be treated, 18 g of MK, and 20 g of A are needed to achieve the highest CBR and UCS recorded in this research paper. Finally, the recorded CBR (7-day soaked and unsoaked) and the UCS (7, 21, and 28 days) of the MK + A-treated LS fulfilled the requirements for the construction of a subgrade and subbase.

This paper is dedicated to examining the impact of fine particles, specifically stone dust (passing 600 microns), on the shear strength, friction angle, and dilation angle of a subbase mix. To assess these properties, a large-scale direct shear test employing a 300 mm x 300 mm x 230 mm box was conducted. The subbase mix consisted of well-graded aggregate with varying proportions of fines, ranging from 1 to 15% by mass of the mix. The direct shear test was performed at 49.03 kPa, 98.06 kPa, 147.10 kPa and 196.13 kPa of normal stress across different densities. The findings revealed that the inclusion of 15% fine particles in the mix led to an 18% reduction in the friction angle for the loose mix and a 10% reduction for the compacted mix. Notably, the friction angle of the subbase mix proved to be influenced by factors such as normal stress, density, void ratio, and stone dust content. In compacted subbase mixes, the friction angle was predominantly influenced by variations in the mix's void ratio. The average dilation angle was determined to be 7.73 degrees for the loose mix and 16.36 degrees for the compacted mix. The analysis indicated that alterations in the dilation angle were impacted by normal stress, density, and the mean grain size of the mix. Furthermore, statistical analysis underscored the significant influence of the proportion of stone dust particles on the peak shear stress of the subbase mix. These findings collectively contribute to a comprehensive understanding of how fine particles, specifically stone dust, affect crucial mechanical properties in subbase mixes.

The scarcity of natural resources, and energy demand/carbon footprints related to their processing and transportation, has led to the quest for alternate materials for road/pavement construction and other infrastructure development. On the other side, landfill mined soil like fraction (LMSF) forms significant proportion of mined legacy landfill waste that exists at different locations around the world; however, it has found limited applications. The present study explores the utilization of LMSF in development of novel asphalt road subbase layers for resilient road infrastructure. 30-60% of LMSF replacement has been studied, and findings based on gradation analysis, compaction tests and California bearing ratio (CBR) tests are quite encouraging. Most combinations of subbase layers studied exceed the design requirements for low volume roads in Indian scenario (rural and outer urban roads); while 30% LMSF in wet mix macadam satisfies the requirements of Indian and other international codes. The cost-benefit analysis shows significant saving in material cost due to utilization of LMSF in road subbase layer. The potential utilization of low cost and sustainable LMSF in asphalt road subbase layer would allow design of superior roads with CBR exceeding design values, resulting in better life cycle performance of road infrastructure with high resilience to fatigue effects, water inundation and overloading conditions.