In order to study the effects of recycled aggregate with different particle gradations and different contents on the mechanical properties of cement soil modified by nano-MgO, unconfined compressive strength and scanning electron microscope (SEM) tests were carried out. The cement content was fixed at 15% and the nano-MgO content was 1.5%. The effects of two ages, three recycled aggregate contents, and three recycled aggregate particle gradations were considered. The test results show that the unconfined compressive strength of natural graded (RA), recycled coarse aggregate (SRA), and recycled fine aggregate (TRA) reached the maximum when the content of recycled aggregate was 20%, and the unconfined compressive strength of SRA was higher than that of TRA and RA. The residual strength of RA and SRA samples first increased and then decreased with the increase in recycled aggregate content, and the residual strength of TRA samples increased gradually with the increase in recycled aggregate content. The variation law of peak strain and peak strength of the three particle graded samples was consistent, and the variation law of brittle failure degree was highly consistent with that of residual strength. When the recycled aggregate content of RA, SRA, and TRA samples was 20%, the deformation resistance and stiffness of the samples were the best. In addition, SRA samples showed the best deformation resistance, followed by TRA samples and, finally, RA samples. The smaller the porosity of the sample, the tighter the sample structure and the stronger the bearing capacity of SRA. The unconfined compressive strength of the WPRA sample was represented by an exponentially negative power function of the porosity.

In recent years, expanded polystyrene (EPS) lightweight soil has been widely used as subgrade in soft soil areas because of its light weight and environmental protection. This study aimed to investigate the dynamic characteristics of sodium silicate modified lime and fly ash treated EPS lightweight soil (SLS) under cyclic loading. The effects of EPS particles on the dynamic elastic modulus (Ed) and damping ratio (λ) of SLS were determined through dynamic triaxial tests at various confining pressures (σ3), amplitudes, and cycle times. Mathematical models of the Ed of the SLS, cycle times, and σ3 were established. The results revealed that the EPS particle content played a decisive role in the Ed and λ of the SLS. The Ed of the SLS decreased with an increase in the EPS particle content (EC). The Ed decreased by 60% in the 1–1.5% range of the EC. The existing forms of lime fly ash soil and EPS particles in the SLS changed from parallel to series. With an increase in σ3 and amplitude, the Ed of the SLS gradually decreased, the λ generally decreased, and the λ variation range was within 0.5%. With an increase in the number of cycles, the Ed of the SLS decreased. The Ed value and the number of cycles satisfied the power function relationship. Additionally, it can be found from the test results that 0.5% to 1% was the best EPS content for SLS in this work. In addition, the dynamic elastic modulus prediction model established in this study can better describe the varying trend of the dynamic elastic modulus of SLS under different σ3 values and load cycles, thereby providing a theoretical reference for the application of SLS in practical road engineering.

The treatment of wastewater by adsorption is a good alternative technique and attracts extensive attention worldwide due to its versatility, scalability, and low operational costs. In this work, a Fe3O4 nanospheres/carbon core–shell structure is fabricated by combination of a template method and calcination. The morphology and crystal structure of the synthesized composite are characterized by transmission electron microscopy, X-ray powder diffraction, Fourier transform infrared spectrometer, and from nitrogen adsorption–desorption isotherms, confirming that the carbon layer with a porous structure is successfully loaded onto the surface of the face-centered cubic Fe3O4 nanospheres to form a core–shell structure. The adsorption performance of the Fe3O4 nanospheres/carbon core–shell structure is investigated by studying the effects of the initial pH value of the solution, the contact time, the initial concentration of the pollutants, the adsorption temperature, and the amount of adsorbent. The Fe3O4 nanospheres/carbon core–shell structure effectively removes heavy metal Chromium(VI) and a reactive light yellow dye. The results of batch experiments show that the removal efficiencies of heavy metal Chromium(VI) and the reactive light yellow dye are close to 100% under optimized conditions. The good adsorption performance of the Fe3O4 nanospheres/carbon core–shell structure toward various types of pollutants suggests a potential application in wastewater treatment.