Rubber powder–polymer combined stabilization of South Australian expansive soils

Abstract

This study examines the combined capacity of rubber powder inclusion and polymer treatment in solving the swelling problem of South Australian expansive soils. The rubber powder was incorporated into the soil at three different rubber contents (by weight) of 10%, 20% and 30%. The preliminary testing phase consisted of a series of consistency limits and free swell ratio tests, the results of which were analyzed to arrive at the optimum polymer concentration. The main test program included standard Proctor compaction, oedometer swell–compression, soil reactivity (shrink–swell index), cyclic wetting and drying, crack intensity, and micro-structure analysis by means of the scanning electron microscopy (SEM) technique. The improvement in swelling potential and swelling pressure was dependent on the rubber content, with polymer–treated mixtures holding a notable advantage over similar untreated cases. A similar dependency was also observed for the crack intensity factor and the shrink–swell index. The beneficial effects of rubber inclusion were compromised under the cyclic wetting and drying condition. However, this influence was eliminated where the rubber powder was paired with the polymer agent. A rubber inclusion of 20%, preferably paired with 0.2 g/l polymer, was suggested to effectively stabilize South Australian expansive soils.

Consistency limits and compaction characteristics of clay soils containing rubber waste

“…Moreover, a series of cavity-like micro-cracks are distributed along the rubber's surface (see Figure 1(c)), thus making for a rough surface texture. Such surface features may potentially promote adhesion and/or induce interfacial friction between the rubber particles and the soil grains, thereby altering the soil fabric into a coherent matrix of enhanced mechanical performance (Soltani et al, 2018b). The physical properties and chemical composition of GR, as supplied by the manufacturer, are provided in Table 2.…”

“…As a consequence of rubber particles floating in water, standard procedures outlined in ASTM D854-14 (ASTM, 2014) for measuring the specific gravity of solids were not applicable. Therefore, the specific gravity for various GRC blends was estimated by the following theoretical relationship (Soltani et al, 2018b) 1:…”

“…The consistency limits, the liquid limit in particular, can be employed to infer the development of soil fabric (Kim and Palomino, 2009;Soltani et al, 2018b;Wroth and Wood, 1978). A decrease in the liquid limit, as is the case with GRC blends (see Figure 4), implies that a face-to-face aggregated (or dispersed) fabric dominates the GRC matrix (Mitchell and Soga, 2005).…”

“…swell-shrink capacity), which can facilitate the production and placement of sustainable earth fills such as road and railway embankments (e.g. Cabalar et al, 2014;Cetin et al, 2006;Özkul and Baykal, 2007;Perez et al, 2017;Signes et al, 2016;Soltani et al, 2018bSoltani et al, , 2018cSrivastava et al, 2014;Trouzine et al, 2012;Wang et al, 2018;Tiwari, 2017a, 2017b). When placed in a flowable condition, the rubber-soil blend outperforms conventional soil backfills by enabling the placement of particles into any irregular or inaccessible space without significant compaction efforts (ACI R229 (ACI, 2013)).…”

Swelling behaviour of expansive soils randomly mixed with recycled geobeads inclusion

“…Thus, the overlying structure found on expansive soil poses great distress and severe damages [7]. Therefore, these soils require modifications, which necessitate engineering solutions to meet design criteria for prior application [8,9].…”