Abstract
This study examines the potential use of sodium alginate (SA) biopolymer as an environmentally sustainable agent for the stabilization of rubberized soil blends prepared using a high plasticity clay soil and tire-derived ground rubber (GR). The experimental program consisted of uniaxial compression and scanning electron microscopy (SEM) tests; the former was performed on three soil-GR blends (with GR-to-soil mass ratios of 0%, 5% and 10%) compacted (and cured for 1, 4, 7 and 14 d) employing distilled water and three SA solutions—prepared at SA-to-water (mass-to-volume) dosage ratios of 5, 10 and 15 g/L—as the compaction liquid. For any given GR content, the greater the SA dosage and/or the longer the curing duration, the higher the uniaxial compressive strength (UCS), with only minor added benefits beyond seven days of curing. This behavior was attributed to the formation and propagation of so-called “cationic bridges” (developed as a result of a “Ca2+/Mg2+ ⟷ Na+ cation exchange/substitution” process among the clay and SA components) between adjacent clay surfaces over time, inducing flocculation of the clay particles. This clay amending mechanism was further verified by means of representative SEM images. Finally, the addition of (and content increase in) GR—which translates to partially replacing the soil clay content with GR particles and hence reducing the number of available attraction sites for the SA molecules to form additional cationic bridges—was found to moderately offset the efficiency of SA treatment.
Highlights
The rapid economic development of modern societies has resulted in a dramatic rise in waste generation
Recent research involving the addition of recycled ELT-based products—mainly in the form of granulates, referred to as ground rubber (GR)—to low-grade clay soils has shown that the compacted soil-GR blend demonstrates excellent properties in terms of diminishing the soil’s swell–shrink volume change capacity, as well as its desiccation-induced cracking potential [6,7,8,9,10,11,12,13,14,15]
The experimental program consisted of uniaxial compression and scanning electron microscopy (SEM) tests; the former was performed on three different soil-GR blends compacted using distilled water and three different sodium alginate (SA) solutions—prepared at three different SA-to-water dosage ratios of 5, 10 and 15 g/L—as the compaction liquid
Summary
The rapid economic development of modern societies has resulted in a dramatic rise in waste generation. In terms of shear strength and bearing capacity, the addition of GR, at low GR-to-soil mass ratios (mainly less than 10%), has been found to produce relatively small improvements; soil-GR composites prepared with higher GR contents have been reported to create serious strength and stiffness concerns, and are generally not considered as high-performance geomaterials [6,9,11,13,21,22,23,24,25,26] For those projects where the strength and stiffness of the composite geomaterial are primary concerns, the compacted soil-GR blend requires stabilization. In view of the limited literature on employing SA in ground improvement practice, this experimental study investigates the application of an SA-based biopolymer as an environmentally sustainable agent for the stabilization of soil-GR blends (prepared using a high plasticity clay soil). The fundamental principles of soil chemistry, along with typical SEM images, were employed to identify and discuss the soil–SA and soil-GR–SA amending mechanisms
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