Case Study: Use of Geopolymers to Evaluate the Swell-Shrink Behavior of Native Clay in North Texas

Sustainability Benefits Assessment of Metakaolin-Based Geopolymer Treatment of High Plasticity Clay

“…Expansive soils are present all over the world and are ubiquitous in the south-western United States [3][4][5][6]. Millions of dollars are spent each year in the United States alone to fix damages caused to infrastructures by expansive soils [3,[7][8][9][10]. As such it is important to improve swelling and shrinkage characteristics of expansive soils before proceeding with infrastructure development.…”

“…where, M is the alkali metal cation (such as Na, K, or Ca), n is the degree of polycondensation, z is the silicon to aluminum (Si:Al) ratio (usually 1, 2, or 3), and w is the molar water amount. Geopolymers are formed in a high pH environment through an alkali-activated polycondensation reaction comprising of five stages-dissolution, speciation equilibrium, gelation, reorganization, and polymerization and hardening [10,24,32]. The synthesis of geopolymers requires an aluminosilicate-rich source (metakaolin, fly ash), an alkali-metal cation source (such as NaOH, KOH, or Ca(OH) 2 ), an additional source of silica (as needed), and water.…”

“…The gelation of different aluminosilicate species and characteristics of their respective geopolymer formations are dependent on various factors such as concentration of reactive species in solution, raw material type and quality, water content, curing conditions, and time [29,34,35]. Recent studies have shown that metakaolin-based geopolymers significantly improved the strength and volume-change properties of expansive soils [10,33,36,37]. The focus of this study is to assess the sustainability benefits of the metakaolin-based geopolymer used by the authors to successfully treat a high plasticity expansive clayey soil [10,33].…”

“…Recent studies have shown that metakaolin-based geopolymers significantly improved the strength and volume-change properties of expansive soils [10,33,36,37]. The focus of this study is to assess the sustainability benefits of the metakaolin-based geopolymer used by the authors to successfully treat a high plasticity expansive clayey soil [10,33]. The sustainability benefits of the metakaolin-based geopolymer in this study were evaluated based on the sustainability framework developed at University of Texas at Arlington, which utilizes a weighted multi-criterial evaluation based on resource consumption, environmental impact, and socio-economic impact [18].…”