Coastal regions often face challenges with the degradation of cementitious foundations that have endured prolonged exposure to corrosive ions and cyclic loading induced by environmental factors, such as typhoons, vehicular traffic vibrations, and the impact of waves. To address these issues, this study focused on incorporating Nano-magnesium oxide (Nano-MgO) into cemented soils to investigate its potential impact on the strength, durability, corrosion resistance, and corresponding microstructural evolution of cemented soils. Initially, unconfined compressive strength tests (UCS) were conducted on Nano-MgO-modified cemented soils subjected to different curing periods in freshwater and seawater environments. The findings revealed that the addition of 3% Nano-MgO effectively increased the compressive strength and corrosion resistance of the cemented soils. Subsequent dynamic cyclic loading tests demonstrated that Nano-modified cemented soils exhibited reduced energy loss (smaller hysteresis loop curve area) under cyclic loading, along with a significant improvement in the damping ratio and dynamic elastic modulus. Furthermore, employing an array of microscopic analyses, including nuclear magnetic resonance (NMR), X-ray diffraction (XRD), and scanning electron microscopy (SEM), revealed that the hydration byproducts of Nano-MgO, specifically Mg(OH)2 and magnesium silicate hydrates, demonstrated effective pore space occupation and enhanced interparticle bonding. This augmentation markedly heightened the corrosion resistance and durability of the cemented soil.

Silt is generally stabilized with industrial waste for subgrade filler material. However, problems such as high cost, poor water stability, and easy shrinkage hinder the use of industrial waste-stabilizing materials. Experiments are conducted to compare the effect of nano-silica (NS) and nano-MgO (NM) on the unconfined compressive strength (UCS) of silt. It is undertaken by stabilized silt with NM and NS in four different concentration grades of NM(S)-3, NM(S)-4, NM(S)-5, NM(S)-6 ( 0.3%, 0.4%, 0.5%, 0.6% by weight of silt). XRD, FT-IR, and SEM tests are carried out to discern the latent mechanisms so that the mineral composition and pore structure within the soil matrix can be explained. The results demonstrate that the increase in different grades of nano-MgO and nano-silica stabilized silt plays an important role in improving the mechanical properties of the silt. Nano-silica is more conducive to strength and water resistance enhancement due to the formation of ettringite and C-S-H gel. Nevertheless, a small amount of nano-MgO can better improve the water stability of stabilized silt in the early stage. Optimal results are obtained for silt treated with NS-5 (2% cement, 2% GGBS, 1% FA, 0.5% nano-silica) and NM-5 (2% cement, 2% GGBS, 1% FA, 0.5% nano-MgO). XRD, FT-IR, and SEM analysis of the samples show, respectively, that the amorphous (C-S-H) structure and the soil particles embedded in the cementitious matrix comprise the strength of the silt. Nano-MgO is mainly involved in carbonation and pozzolanic reactions. The cement hydration reaction and ettringite formation, which unite smaller particles to produce larger particles, are enhanced by the addition of SiO2. In summary, this paper recommends the use of nano-MgO to improve the early strength of stabilized silt, and the use of nano-silica to improve the long-term strength.

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.