Mechanical behaviour and permeability of expansive soils mixed with scrap tire rubbers subjected to freeze-thaw cycles

Abstract

Due to the extensive generation of scrap tires around the world, the application of such waste materials has been considered as an environmentally friendly and cost-effective solution. In geotechnical and geo-environmental engineering, sub-productions derived from scrap tires have been effectively reused to modify the problematic expansive soils. However, no further evaluation has been explored on its performance under freeze-thaw weathering. To fill this gap, this paper presents an attempt to investigate the effect of freeze-thaw cycles on volume change, mechanical behaviour and permeability of expansive soils mixed with scrap tire rubbers. Scrap tire rubber in the form of crumb rubber powder was mixed with natural expansive soils with the percent by weight of 0%, 1%, 3%, 6%, 10%, 15% and 25%. All the laboratory tests were performed on expansive soil-rubber mixtures after 0, 1, 2, 3, 6, 10 and 15 freeze-thaw cycles. The volume change, stress-strain response, unconfined compression strength, resilient modulus, strain at failure as well as permeability coefficient of the expansive soil-rubber mixtures have been discussed. The results show that cyclic freeze-thaw has a significant degradation of mechanical and hydraulic performance of expansive soil-rubber mixtures. Small amount of rubber addition (CR = 1– 3%) will make soil less sensitive to swelling-shrinkage, thereby increasing strength/stiffness and reducing permeability. Under freeze-thaw weathering, CR = 10% plays a critical role in the transformation behaviours of stress-strain response, failure pattern and ductility with rubber content. Besides, independent of freeze-thaw cycles, the relations between resilient modulus and unconfined compression strength can be well expressed by a quadratic function. Increasing freeze-thaw cycles significantly increases the void ratio of parent soil matrix, thus leading to the increase in permeability. Additional research is encouraged to explore an effective method to prevent the freeze-thaw triggered performance deterioration of rubber modified expansive soils in practical projects.