Enhancing Dynamic Shear Resistance and Efficient Micro-Void Reduction of Expansive Soil Using Activated Nano-Desilicated Fly Ash

Abstract Excessive swelling and high compressibility of soil have posed countless challenges such as poor dynamic shear strength for engineers dealing with cyclic loading in pavement structure. To address this challenge, the durability and mechanical properties of the investigated subgrade were treated with 10%, 20%, and 30% of activated nano-disilicate fly ash (NDFA) to the dry mass of the subgrade soil. A series of swelling pressure tests, One-dimensional compression tests, and dynamic triaxial (DT) tests were conducted on the samples fabricated using altered moisture content. The findings demonstrated that the swelling pressure and compressibility of the NDFA-treated specimens significantly decreased to an average of 15.3% and 18.4% respectively upon 20% inclusion of NDFA beyond which the swelling stress and compressibility values further decreased signifying the impact of NDFA on the expansive subgrade. The consolidation results also revealed that the treated soil’s consolidation parameters greatly decreased compared to the untreated soil with a high void ratio and compression index ( $${C}_{c}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>C</mml:mi> <mml:mi>c</mml:mi> </mml:msub> </mml:math> ). The dynamic shear resistance of the subgrade soil increased by 36% upon the addition of 10% NDFA content compared to the untreated soil which portrayed a very low resistance against dynamic shear modulus ( $${G}_{max}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>G</mml:mi> <mml:mrow> <mml:mi>max</mml:mi> </mml:mrow> </mml:msub> </mml:math> ) with a corresponding high damping ratio. The investigation revealed a strong correlation between $${C}_{c}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>C</mml:mi> <mml:mi>c</mml:mi> </mml:msub> </mml:math> and dynamic shear modulus which is closely correlated to a coefficient determination of 0.99 due to the parameter’s dependency on porosity, particle shape, and stiffness.