Feasibility of Stabilized Pond Ash as a Sustainable Pavement Material: Preconstruction and Post-Construction Analysis

Abstract The effect of geopolymer additive on the hydromechanical properties of pond ash (PA) was assessed with reference to conventional stabilizers like lime and cement. The mix ratios of these additives varied from 3% to 15% by dry weight of PA. Laboratory results showed that the PA-additive mixes achieved higher maximum dry density at lower optimum moisture content. Key engineering properties such as unconfined compression strength (UCS), indirect tensile strength, and California bearing ratio of the stabilized PA were enhanced with an increase in the additive content and curing durations. However, the hydraulic conductivity and compressibility index were reduced. Conspicuously, the 28-day stabilized PA with 15% geopolymer showed the best performance with higher UCS (11.21 MPa), lower hydraulic conductivity ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mrow> <mml:mn>6.35</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mn>10</mml:mn> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>8</mml:mn> </mml:mrow> </mml:msup> <mml:mtext> </mml:mtext> <mml:mi mathvariant="normal">m</mml:mi> <mml:mo stretchy="false">/</mml:mo> <mml:mi mathvariant="normal">s</mml:mi> </mml:mrow> </mml:math> ), and lower compressibility index (0.00036). These engineering properties are mainly due to the formation of calcium and sodium-based phases (C─ A─ S─ H, N─ A─ S─ H, and C─ S─ H) in geopolymer-stabilized PA. Stabilized PA with 9% geopolymer satisfied the 7-day UCS of cementitious base (CB) in flexible pavements. The 3% geopolymer and 15% cement attained the strength requirements of the cementitious subbase (CSB). Performance analysis under traffic loading confirmed the suitability of stabilized PA as CB and CSB in flexible pavements, with a significant reduction in pavement thickness at optimal additive dosage. Further, the geopolymer-stabilized PA has lower embodied energy and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>CO</mml:mi> <mml:mn>2</mml:mn> </mml:msub> </mml:mrow> </mml:math> emission per unit volume and unit strength gain.