This study investigates the potential of graphene-based additives to improve the mechanical properties of compacted soil mixtures in rammed-earth construction, contributing to the development of environmentally friendly building materials. Two distinct soils were selected, combined with sand at optimized ratios, and treated with varying concentrations of a graphene liquid solution and a graphene-based paste (0.001, 0.005, 0.01, 0.05, and 0.1 wt.% relative to the soil-sand proportion). The effects of these additives were analyzed using the modified Proctor compaction and unconfined compressive strength (UCS) tests, focusing on parameters such as optimum water content (OWC), maximum dry density (MDD), maximum strength (qu), and stiffness modulus (E). The results demonstrated that graphene's influence on compaction behavior and mechanical performance depends strongly on the soil composition, with minimal variation between additive types. In finer soil mixtures, graphene disrupted particle packing, increased water demand, and reduced strength. In silt-sandy mixtures, graphene's hydrophobicity and limited interaction with fines decreased water absorption and preserved density but likewise led to diminished strength. Conclusions from the experiments suggest a possible interaction between graphene, soil's finer fraction, and potentially the swelling and non-swelling clay minerals, providing insights into the complex interplay between soil properties.

To address environmental concerns related to cement-stabilized expansive soil and the safety risks of caustic-activated blast furnace slag, this study explores the use of lime-activated blast furnace slag as an alternative stabilizer in northern Hebei, China. The effects of slag dosage, curing time, and osmotic pressure on the expansion, osmotic properties, and strength of the improved soil were evaluated through free expansion rate, permeability coefficient, and unconfined compressive strength tests. Results show that adding slag-lime significantly reduces soil expansion. As slag content increases, the free expansion rate decreases exponentially. During the curing period of 3-7 days, expansion declines and stabilizes between 7-14 days. Similarly, the permeability coefficient permeability coefficient decreases with higher slag content, following a quadratic trend. Under osmotic pressures of 0.1-0.2 MPa, the permeability coefficient permeability coefficient increases but stabilizes between 0.2-0.4 MPa.Furthermore, slag-lime significantly enhances unconfined compressive strength, which increases linearly with slag content. The stress-strain curve follows a logistic function in the rising stage and a rational fractional equation in the descending stage.This study demonstrates that lime-activated blast furnace slag is a sustainable and effective alternative for stabilizing expansive soils while reducing dependence on cement.