Date of Award

Spring 5-3-2024

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Civil Engineering

Advisor

Luis Zambrano Cruzatty

Second Committee Member

Aaron Gallant

Third Committee Member

Bill Davids

Abstract

Soil Carbonation presents an approach for chemically stabilizing subgrade materials, inducing cementation within the soil matrix by generation of a calcium carbonate binder. Unlike conventional methods, which rely solely on additives, soil carbonation introduces carbon dioxide gas to trigger a reaction, precipitating carbonate minerals that enhance the soil’s strength and stiffness. A notable advantage of this method is carbon sequestration, reducing significantly the carbon footprint compared to traditional techniques reliant on chemical additives, which makes it a sustainable stabilization alternative. Reaction kinetics and gas mobility largely dictate the rate of carbonation and binder formation within the soil matrix. In this investigation, non-plastic silt samples mixed with varying amounts of hydrated lime with different saturations underwent carbonation at different times. Employing an instrumentation setup capable of real-time monitoring, including pressure, flow, temperature, and shear wave velocity measurements. Results indicate that carbonation levels are higher at lower lime concentrations but diminish as lime content increases. Pressure distribution during carbonation follows a linear trend, correlating with temperature fluctuations resulting from the exothermic reaction.

Analyzing carbon dioxide flow through lime-treated soils poses significant challenges due to the complex interplay of physicochemical reactions, coupled 2D and 3D flow regimes, and evolving soil conditions (e.g., saturation, void ratio). To address these challenges and facilitate potential implementation schemes, a numerical framework is proposed. This framework utilizes mass conservation principles and the advection-diffusion equation to simulate gas flow, reaction kinetics, and binder formation rates within the porous media. The governing partial differential equations are solved using the finite element method, and the predicted spatial and temporal variations in binder content are compared with observations from 1D carbonation experiments involving lime-mixed silt. The findings affirm that the proposed numerical formulation captures the intricate interplay of gas flow and reaction kinetics, offering valuable insights for predicting soil carbonation.

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