MECHANICAL PERFORMANCE OF GUAR GUM-STABILISED SOIL FROM THE YAMUNA BASIN

Abstract

Weak alluvial subgrades in the Yamuna floodplain, Delhi, represent a persistent geotechnical challenge for infrastructure development in one of India’s most rapidly urbanising regions. Conventional stabilisation approaches, while technically effective, rely heavily on cement and lime and carry substantial environmental penalties arising from energy-intensive production processes and significant carbon dioxide emissions. The present investigation evaluates guar gum, as an eco-friendly alternative for stabilising alluvial soil retrieved from the Yamuna Basin. Specimens were treated at dosage levels of 1.0% and 1.5% guar gum by dry soil weight and subjected to Standard Proctor compaction, Unconfined Compressive Strength (UCS) and California Bearing Ratio (CBR) testing following curing periods of 3, 7, and 21 days. Microstructural characterisation was carried out using Scanning Electron Microscopy (SEM) to elucidate the physical bonding mechanisms underlying observed macroscale performance improvements. Additionally, a theoretical carbon emission analysis was performed to quantify the environmental advantage of biopolymer stabilisation relative to conventional cement based ground improvement. Compaction behaviour proved resilient to biopolymer addition, with maximum dry density and optimum moisture content remaining essentially unchanged across both dosage levels, confirming that guar gum-treated subgrades can be constructed to the same field specification as untreated fill. UCS results revealed a consistent, curing-dependent strength trajectory: the 1.0% dosage achieved the highest peak strength of approximately 4.80 kPa at 21 days, representing a 136% improvement over the untreated baseline of 2.03 kPa. CBR testing demonstrated a complementary dosage-response, with the 1.5% treatment achieving a 90% improvement in load resistance at 21 days under confined loading conditions. SEM analysis confirmed a hierarchical bonding structure operating simultaneously at sub-micron, micron, and aggregate length scales, providing the microstructural basis for observed macroscale performance gains. The theoretical carbon emission analysis indicates that guar gum stabilisation at the 1.0% dosage produces approximately 3 to 6 kg CO₂ per cubic metre of treated soil, representing a reduction of 90 to 95% relative to conventional cement stabilisation, which generates an estimated 72 to 115 kg CO₂ per cubic metre. These findings collectively establish guar gum as a technically sound and environmentally responsible approach to ground improvement for collapsible Yamuna Basin soil, with direct applicability to pavement subgrade and low-to-moderate load-bearing foundation contexts in ecologically sensitive floodplain environments.