Department of Civil Engineering
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Item Lime stabilization of sulfate-rich soil using quarry fines as a sustainable co-admixture(Springer, 2025-05) Chakraborty, SayantanThe engineering properties of the underlying soil govern the durability and performance of civil engineering infrastructures. Chemical stabilization using lime is adopted widely to treat problematic clayey soils that do not possess acceptable engineering properties. However, the presence of sulfate salts is often counterproductive due to ettringite formation. Precompaction mellowing or the addition of amorphous silica-rich co-admixtures like fly ash or ground granulated blast furnace slag are widely used to mitigate ettringite-induced heaving. This research study investigates the potential of utilizing a crystalline silica-rich sustainable co-admixture derived from quarry dust to improve the engineering properties of sulfate-rich soil with kaolinite as the predominant clay mineral. Unconfined compressive strength tests, with and without capillary soaking, and one-dimensional (1D) free swell tests were performed on specimens treated with lime alone and lime along with quarry fines after different curing periods to assess the extent of strength reduction and swelling characteristics after moisture exposure. Mineralogical and microstructural analyses using X-ray diffraction and scanning electron microscope imaging with energy-dispersive X-ray spectroscopy were used to investigate the potential causes of the observed changes in strength and volume change characteristics. Results indicate that lime, along with quarry fines, effectively stabilized the problematic sulfate-rich soil. The improvement in engineering properties was prominent at higher dosages of quarry fines and after prolonged curing time.Item Micro-mechanical analyses to understand the durability of chemically stabilized geomaterials against moisture-induced damage(ASCE, 2025) Chakraborty, SayantanChemical stabilization with calcium or Ca-based stabilizers, such as lime, has been used worldwide to enhance the engineering properties of problematic soils. Although lime treatment improves the mechanical properties of problematic soils, moisture intrusion is often detrimental to the stabilized layers. The extent of improvement and the durability of the lime-treated soils depend on several factors, including stabilizer dosage, curing period, and soil type. This research study was designed to investigate the influence of predominant clay minerals and stabilizer dosage on the durability and resiliency of lime-treated soils against moisture-induced damage. Two clayey sand groups bearing kaolinite and montmorillonite as the predominant clay minerals were treated with the Ca-based stabilizer as per existing recommended practice, and the strength and durability properties were studied after different curing periods. Besides engineering tests, mineralogical and microstructural analyses were also considered to identify the reasons responsible for the observed engineering behavior before and after moisture conditioning. Test results indicate that the extent of strength gained after lime treatment is less for soils with kaolinite as the predominant clay mineral than those containing montmorillonite. However, the percentage strength loss after capillary soaking was lower in lime-treated kaolinite-rich soils compared to that having montmorillonite when treated with optimum +2% lime dosage and cured for a longer time.Item Ground improvement studies on problematic soils: innovative materials with sustainable applications(Springer, 2024-10) Chakraborty, SayantanChemical stabilization of problematic sulfate-rich soils is a considerable cause of concern even to this day for geotechnical and transportation engineering practitioners. With the advent of innovative materials and technologies, researchers have tried to incorporate them into ground stabilization practices. However, the application of novel materials is often met with apprehension when the concept of long-term durability and sustainability of construction is weighed upon. The researchers at Texas A&M University have been studying innovative stabilization methods to address some of the prevailing problems of traditional stabilization methods. Application of metakaolin-based geopolymers and novel silica-based admixtures with Ca-based treatments to improve problematic soil properties is presented in this paper. Micro-mechanical behavior of the stabilized soils was investigated using both engineering and mineralogical studies. Engineering studies included strength, stiffness, moisture-susceptible durability, and free swell strain tests. Additionally, X-ray diffraction studies and scanning electron microscope imaging were performed to understand the microstructural behavior of the treated geomaterials. Sustainability benefits of the stabilizers were assessed using a unified framework, which subsumed the effects of embodied energy for production, environmental impacts, and socio-economic impacts of the treatment. The engineering and microstructural studies showed that the new stabilization methods provided more durable geomaterials as compared to traditional treatments. Sustainability assessments showed that new stabilization methods could be considered as a potential alternative if the production cost is significantly reduced. Overall, this keynote paper provides new insights into innovative stabilization methods, which may be of enormous benefit to geotechnical and transportation engineering practitioners.Item Optimization of sandstone processing waste, electric arc furnace slag, and fly ash-based ternary blended eco-friendly geopolymers(Springer, 2024-11) Bhunia, Dipendu; Chakraborty, Sayantan; Lahoti, MukundOver the years, ordinary Portland cement (OPC) has been used to meet growing demands of land and housing facilities arising out of population overburdens. It is well documented that OPCs, besides their outstanding qualities as building materials, are also significant contributors to global greenhouse gases (GHG). Consequently, recent years have noticed an emerging interest in the search for alternatives to Portland cement-based binders. Geopolymers are well-suited to serve this purpose owing to their superior attributes and low CO2 emissions compared to conventional cement. Still, the industrialization of geopolymers has not reached a meaningful value due to the prevailing fundamental barriers involving the requirement of corrosive environments and intensive heat-curing regimes in post-fabrication processes. The current study investigates the viability of using synergistic mixtures based on stone residues, pulverized ash, and steel slags in fabricating geopolymer composites cured at ambient temperature with reduced ingestion of alkalis. A comprehensive assessment of the engineering, mineralogical, and microstructural characteristics was performed in terms of setting times, physico-mechanical, durability, non-destructive, and analytical tests. Further, a scaled-down approach was utilized to evaluate the feasibility of the designed composites as construction entities. The incorporation of SW (10–40%) prolonged the setting periods (~ 150 min.) and abridged the engineering properties of the ternary pastes collectively by 127% due to silica coalescences. Besides, replacements of stone residues with FA (20–30%) and EAF (30–60%) improved the blend performance due to Ca and Al assimilations. All the developed composites satisfied the acclamations for OPC grade 33, CEM V class 32.5N, and OPC Type – I suggested by IS, EN, and ASTM standards, respectively, with matrices constituting CASH-CSH-NASH-(N,C)-A-S–H type gelation complexes identified by the X-ray, infrared, and electron imaging spectroscopic analysis. In addition, a cumulative deficit of about 60–90% was observed in energy and carbon footprints relative to OPCs, indicative of the binders’ sustainability traits.