A series of direct shear tests were performed on cement-admixed silty clay to investigate the effect of cement content and nano-magnesia (MgO) on its shear strength properties. For each normal stress, shear strength increased with cement content. However, an obvious increment in shear strength was achieved when the cement content was adjusted from 13% to 17%. Both cohesion and friction angle of cemented soil increased with cement content, and exponential function was adopted to correlate both the factors with cement content. For cement content of 10% investigated in this study, the optimum nano-MgO content was 10‰, wherein the cohesion could reach the peak value. The microstructure of the mixture revealed that the structure of the mixture was compacted for the optimum nano-MgO content. However, micro-cracks were formed when the amount of nano-MgO exceeded its optimum content.

The construction industry is characterized by high energy consumption and high carbon emissions. With growing concern about climate change, environmental protection is becoming increasingly important. In this paper, the whole construction process of prefabricated floor slab (PFS) is divided into three stages: production, transportation, and construction stages. Carbon emissions are calculated based on the life cycle assessment (LCA) method. A case study of PFS construction in Shaoxing city, China, was examined, and the calculation results were compared and evaluated with the traditional construction methods, which showed that in the production stage, carbon emissions increased due to mechanical operations during the prefabrication process. In the transportation stage, carbon emissions also increased due to the heavier prefabricated components during the transportation process. During the on-site construction stage, carbon emissions considerably decreased due to the lower hoisting frequency and less on-site pouring.

In this study, the mechanical behaviour of nano magnesia–cement-reinforced seashore soft soil (NmC3S) was evaluated and characterised by the direct-shear testing of seashore soft soil (3S), cement reinforced seashore soft soil (C3S) and NmC3S. The comparison among these three types of soils indicates that NmC3S has greater shear strength and deformation modulus than C3S and 3S. The shear stress of both C3S and NmC3S increase significantly prior to a shear displacement of 1.0 mm, followed by a sharp decline before reaching the critical state. The failure displacement increases as the applied normal stress increases. NmC3S demonstrated greater friction angle than both C3S and 3S; however, the magnitude of its cohesion lies between that of C3S and 3S. Moreover, a mathematical model that describes the shear stress–displacement curve was proposed, which can effectively model the strain-hardening and strain-softening curves of these three types of clays. Finally, a generalised formula for capturing the stress–displacement behaviour of these three materials is presented with the explanations for the physical meaning of each parameter.