Soft Clay Modified with Municipal Solid Waste and Stabilized with Nano-MgO for Pavement Subgrade and Embankment Fill Applications

Abstract

Municipal solid waste (MSW) is the largest group of non-hazardous waste. Four percentages of MSW replacement (15 %, 25 %, 35 %, and 45 % by weight) were used for chemical modification of soft clay at 1, 14, and 28 days of curing. The MSW replacement at optimum (15 % and 25 %) to the clay enhanced unconfined compressive strength (UCS) and California bearing ratio (CBR) by 1.28 and 3.34 times, respectively. Also, the nanomagnesium (Nano-MgO) was used as an additive at small contents i.e., 0.25, 0.5, 0.75, and 1 % to improve the mechanical properties of MSW-soft clay blends. The optimum MSW replacement ratios with 1 % Nano-MgO significantly improves UCS and CBR of the soft clay when compared to clay stabilized with 1 % Nano-MgO. The UCS and CBR improvement mechanism was investigated via microstructural analysis of the MSW-soft clay stabilized with Nano-MgO. The improved structure of stabilized specimens was found to be due to flocculation, cation exchange, and cementation bond formation with brucite mineral. However, the X-ray diffraction tets results indicated the presence of the Palygorskite mineral in the specimen containing very high MSW replacement ratio, which retarded the Nano-MgO stabilization process. At optimum MSW replacement ratio (15 % and 25 %), Nano-MgO could effectively improve mechanical properties of soft clay for sustainable road construction.