Enhancing Subgrade Efficiency with Industrial Ash & Geotextile Combinations for Economical Pavement Solutions

Abstract

The effectiveness of a pavement relies heavily on the characteristics of the soil subgrade, as it works as the foundation for the entire pavement structure. For that reason, subgrade has to hold sufficient stability under adverse climatic and loading conditions. This project mainly focuses on investigating the engineering properties of soil with varying compositions of geotextile sheets, industrial waste rice husk ash, and fly ash to further increase the bearing capacity of soil. The current study was organized in two phases. Initially, the impact of varying proportions of rice husk ash (RHA) (2.5%, 5%, 7.5%, and 10%), similarly for fly ash (5%, 10%, 15%, and 20%), and geotextile layers positioned at varying depths were examined independently to check their individual effects on soil stability. After that, to determine the ideal quantity that can be utilized for soil stabilization and improvement, the rice husk ash and fly ash are mixed along with the geotextile sheets as reinforcement with the soil sample. In our study, the proctor test is carried out on the samples of RHA and fly ash to find out their maximum dry density (MDD) and optimum moisture content (OMC). Then the samples of RHA and fly ash are together compacted to their MDD at the optimum moisture content, with or without reinforcement of geotextile sheets in the CBR mould. The prime focus of the research is to contribute the supporting outcomes to building guidelines for rural roads; thus, soaked and unsoaked CBR with light compaction methodology have been opted for. More than 50 samples have been tested. Geotextile sheets obtained from a reputed industrial outlet that match the size of the CBR mould are laid in separate preparations of different layers at various depths in the CBR mould. After each arrangement, the CBR values are assessed in the lab and compared with the CBR values of unmodified soil samples. At the end of our study, it was concluded that the soaked and unsoaked CBR values increased by up to 73.89% and 60.50%, respectively, when 15% fly ash, 5% RHA, and 80% soil were combined with various layers of geotextile sheets. The characteristics of the soil can be improved, and the thickness of the subgrade layer can be decreased by 25%, by interposing the geotextile sheets between the subgrade layers, resulting in a more affordable pavement. This means that the mixing of these materials with clayey sand soil is capable of improving their engineering properties, such as increasing their bearing capacity, reducing their plasticity, and enhancing their durability. MORTH has suggested wide use of geotextiles, but the need to incorporate their use along with industrial waste on Rural roads while following current MORD guidelines is still a pressing research topic. Research outcomes made it a great way to optimize the performance of clayey-sand soil for construction purposes.