Performance evaluation of silty soil reinforced with glass fiber and cement kiln dust for subgrade applications

Abstract

In this study, the use of glass fiber and cement kiln dust (CKD) as stabilizing agents for a typical silty soil is investigated. Fibers with three lengths (12 mm, 18 mm and 24 mm) were added as percentages of soil’s dry weight (0.3%, 0.6%, 0.9%, and 1.2%), the cement kiln dust (CKD) was added in three percentages by dry weight of soil (7%, 14% and 21%). The subgrade strength was evaluated in terms of laboratory California bearing ratio (CBR) tests in soaked and unsoaked environment to simulate both dry and inundated conditions for field applications. Chemical and microstructural changes were monitored with Fourier transform infrared spectroscopy (FTIR) and integrated FESEM-EDAX analysis respectively. IITPAVE software was used to compute actual strains on pavement layers and determine the optimum thickness of the pavement sections for untreated and treated subgrade. In comparison to the untreated soil, the overall pavement thickness reduced by approximately 44% when designed on improved subgrade. The cost reduction, using the improved subgrade material was approximately 37.5%. Because the actual strains were significantly lesser than the permissible values, the structural performance of the pavement designed on improved subgrade was enhanced against subgrade rutting and fatigue cracking. The optimum CKD–fiber combination was found to be 14% CKD and 0.6% fiber. The laboratory test results indicated that the proposed ground improvement technique can be effective for subgrade improvement of low-volume roads and also serve as a sustainable disposal solution of CKD.