Improved Geotechnical Behavior of an Expansive Soil Amended with Tire-Derived Aggregates Having Different Gradations

Amin Soltani,Abbas Taheri,An Deng,Brendan C O’Kelly

doi:10.3390/min10100923

Amin Soltani, Abbas Taheri + Show 2 more

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https://doi.org/10.3390/min10100923

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Abstract

This experimental laboratory study examines the potential use of tire-derived aggregate (TDA) products as an additive to alleviate the inferior geotechnical properties of a subgrade deposit of clay soil with high expansivity. A total of ten mix designs—the unamended soil and nine soil–TDA blends prepared at 5%, 10% and 20% TDA contents (by dry mass) using three different TDA gradations/sizes—were examined. The experiments included standard Proctor compaction, oedometer swell and unconfined compression tests. The TDA materials’ lower specific gravity, hydrophobic character and higher energy absorption capacity compared with the soil solids led to notable reductions in the soil compaction characteristics. The amendment of the soil with TDA resulted in notable decreases in the rate and magnitude of swelling—the observed reductions were in favor of higher TDA contents, with larger TDA particle size being a secondary factor. Further, for any given TDA size, the variations of strength and toughness with respect to TDA content exhibited rise–fall relationships, peaking at 5% TDA and then decreasing for higher TDA contents. The stiffness and ductility parameters, however, were found to monotonically decrease and increase with the TDA content, respectively. Finally, TDA contents of up to 10%, with gradations equivalent to those of medium and coarse sands, were found to reduce the soil’s swelling potential from high to moderate expansivity, while simultaneously improving its strength-related features, and thus can be deemed as optimum mix design choices from a geotechnical perspective.

Highlights

Clay soils are among the most common of all materials encountered in civil engineering operations.Most clays, are characterized as low-grade construction materials, as their intrinsic mechanical features impacted by high moisture susceptibility may present significant challenges for geotechnical engineering systems [1,2]
The main objectives of this study were to investigate the effects of tire-derived aggregate (TDA) content f T (i.e., TDA-to-soil dry mass ratio) and gradation, mean particle size D50 T, on the soil’s compactability, swelling potential and shear strength properties
The optimum TDA content was found to be 5% for TDA-C, and 10% for both TDA-M and TDA-F. These results indicate that the magnitude of reduction associated with the unconfined compressive strength (UCS) at f T > 5% for TDA-C and f T > 10% for both TDA-M and TDA-F

Summary

Introduction

Clay soils are among the most common of all materials encountered in civil engineering operations.Most clays, are characterized as low-grade construction materials, as their intrinsic mechanical features impacted by high moisture susceptibility (and plasticity) may present significant challenges for geotechnical engineering systems [1,2]. In South Australia, for instance, the presence of significant clay soil deposits, most of which possess notable fractions of 2:1 swelling-type smectite group minerals, has been reported to adversely affect the design and construction of road infrastructure [3] Such soils, which are commonly referred to as reactive or expansive soils, adsorb water in wet seasons and increase in volume (heave), in some cases by up to three times, and subsequently contract and settle during dry seasons. Minerals 2020, 10, 923 costly to repair and compromise road safety [1,4,5] To cope with such adversities, the geotechnical engineer can either complete the design within the limitations imposed by the low-grade clay soil (e.g., overdesigning the pavement system), or preferably, attempt to positively modify the soil’s undesirable properties by way of soil replacement and/or soil stabilization techniques. The former could involve complete removal of the bearing low-grade clay soil and its replacement with a suitable engineered fill, or substituting a portion of the low-grade clay soil with suitable quarried materials, such as sands and gravels, possessing desirable mechanical properties [6,7,8]

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