Sustainable and Environment-Friendly Utilization of Sludge and Eggshell in Soil Subgrade Stabilization

Abstract

Subgrade stabilization of soil is an essential component for the construction of highways and pavements. However, significant quantity of soil stabilizers such as cement or sand or heavy rollers have been previously used to improve the strength of the soil. The utilization of traditional soil stabilization techniques may raise environmental concerns as well as require extensive resources. This abundant utilization of resources can be reduced by considering geotechnical management through efficient soil stabilization. Therefore, current research focuses on the effectiveness of eco-friendly additives (sludge and eggshell powder) at different percentages i.e., 2%, 4%, and 6%, by weight of clayey soil for subgrade stabilization. The soil sample was collected from Nandipur, Punjab, Pakistan. The results indicated that the maximum strength (California bearing ratio and unconfined compressive strength) of soil was achieved when 4% by weight of soil modifier was added. For the same weight percent of modifiers, the soil type changed from clayey (A-7-6) to silty soil (A-4) which is graded as poor to the fair category in the AASHTO classification system. Moreover, the group index of soil also decreased from 34 to 12, which means relatively less thick subgrade will be required hence, less compaction effort will be needed. Moreover, Artificial Neural Network was used to develop correlation between California bearing ratio (10, 30 and 56 blows) and other soil parameters for better prediction of soil properties after the addition of modifiers. Current study also evaluates the economic and environmental benefits of soil modifiers which resulted in reduction of approximately 17.42 million PKR and 71,282 Kg carbon dioxide emissions for two lane highway pavement with dimensions (500m x12m x 0.2m) and 1649.9 Kg/m3 dry density of soil. This research will help develop sustainable, eco-friendly infrastructure and promote energy-efficient construction.

Subgrade stabilization of soil is an essential component for the construction of highways and pavements. However, significant quantity of soil stabilizers such as cement or sand or heavy rollers have been previously used to improve the strength of the soil. The utilization of traditional soil stabilization techniques may raise environmental concerns as well as require extensive resources. This abundant utilization of resources can be reduced by considering geotechnical management through efficient soil stabilization. Therefore, current research focuses on the effectiveness of eco-friendly additives (sludge and eggshell powder) at different percentages i.e., 2%, 4%, and 6%, by weight of clayey soil for subgrade stabilization. The soil sample was collected from Nandipur, Punjab, Pakistan. The results indicated that the maximum strength (California bearing ratio and unconfined compressive strength) of soil was achieved when 4% by weight of soil modifier was added. For the same weight percent of modifiers, the soil type changed from clayey (A-7-6) to silty soil (A-4) which is graded as poor to the fair category in the AASHTO classification system. Moreover, the group index of soil also decreased from 34 to 12, which means relatively less thick subgrade will be required hence, less compaction effort will be needed. Moreover, Artificial Neural Network was used to develop correlation between California bearing ratio (10, 30 and 56 blows) and other soil parameters for better prediction of soil properties after the addition of modifiers. Current study also evaluates the economic and environmental benefits of soil modifiers which resulted in reduction of approximately 17.42 million PKR and 71,282 Kg carbon dioxide emissions for two lane highway pavement with dimensions (500m x12m x 0.2m) and 1649.9 Kg/m3 dry density of soil. This research will help develop sustainable, eco-friendly infrastructure and promote energy-efficient construction.