Determination of engineering properties and sustainability of a sandy soil with slag and tire chips

There are various soil improvement techniques for soil types with poor engineering properties. Two techniques are commonly used in the geotechnical world due to the cost-effectiveness of these techniques; soil replacement and reinforcement. The soil replacement is achieved by proven sustainable materials that could be industry by-products or construction materials such as slags from steel manufacturing or tire chips. Tire chips, as microplastics, have been causing scarcity and impacts on environmental conditions. Researchers have begun to consider recycling these materials in several applications. This study explored the use of the slag at different particle sizes and the other techniques besides the replacement, such as reinforcement using geogrid. Also, the study investigated the use of tire chips representing microplastics to reduce environmental concerns and increase soil improvement at a low cost compared with strategic natural resources deployment. The experimental program includes slag-sand mixtures with 20 and 50 (1:1) percent slag and tire chips, including 0.05, 0.1, 0.2, 0.4, 1, and 2 percent, along with soil reinforcement using geogrid to investigate their influence on shear strength, dry unit weight, and soil density. Slag particle size in the sand was taken as (4.75 mm – 2.36 mm), (2 mm -1.18 mm), (0.85mm – 0.60mm – 0.425mm), and (0.25 mm – 0.15 mm -0.075 mm). The results revealed improved maximum dry unit weight obtained by Proctor compaction tests. This improvement occurred at slag-to-sand ratio of 1:1. The density of the slag-sand mixture obtained from sand cone tests provided better results than that of the sand. The results also showed that particle sizes (4.75 mm – 2.36 mm) and (0.25 mm – 0.15 mm -0.075 mm) of mixed 20% slag with sand provided better shear strength than other sizes, even those reinforced by geogrid. From the results, the geogrid in 20 percent slag-sand mixture with a particle size of (0.85 mm– 0.60 mm– 0.425 mm) slag provided higher shear strength than the other sizes reinforced with geogrid. Finally, the optimal percentile of tire chips that caused an enhancement in the maximum unit weight of the sand was revealed at 0.4 percent with a value of 1.735 g/cm³.