By virtue of the abundant oxygen-functional groups, ultra-high specific surface area and superior mechanical properties, graphene oxide (GO) has been proven as one of the outstanding candidates in cement composites. Compared with the traditional cement pastes, the GO-reinforced cement composites exhibit benefits in pore structure, mechanical properties, and durability. In addition, the abundant oxygen-containing functional groups on GO can promote the hydration rate of cement and combine with hydration products to fill the pores. To further improve the performance of GO-reinforced cement composites and promote the application of composites in practical engineering, it is necessary to comprehensively understand the reinforcing mechanisms of GO on cement composites. In this work, the enhancement mechanisms of GO to improve hydration, nucleation effects, mechanical strengthening mechanisms, antiseepage mechanisms and pore-filling effects of GO are systematically revealed. The optimal dosage range of GO mixing in the current study is calculated by considering the factors of mechanical property and microscopic characterization, but the economic cost also needs to be considered in future development studies. This review will promote the application of the more cost-effective and high-performance GO-reinforced cement composites in practical construction engineering.

The mechanical property of the pile-core–cement-soil interface is a crucial factor affecting the shaft capacity of the expanded stiffened deep-cement-mixing (ESDCM) pile. The research on the characteristics of the steel-pipe–cement-soil interface is very limited, and the conventional concrete–cement-soil interface research results cannot provide direct guidance for the engineering application of the steel-pipe–cement-soil combination pile. Hence, in this study, we employed a model pile with a steel-pipe–cement-soil combination. By using a confining pressure transfer test and an inner interface shear test, the influence of confining pressure on the inner interface and shear deformation of the inner interface were investigated. The results demonstrated that the lateral confining pressure has almost no effect on the inner interface due to the encapsulation of the soil-cement column. The interface shear experienced four stages: the steel pipe small deformation, which is the extra stage compared to the common concrete–cement-soil combination form; the whole pipe compression; the brittle failure; and the shear-slip stage. The peak shear stress at the interface is 194 kPa, and the corresponding pile core top displacement and core bottom displacement are 5.9 mm and 5.4 mm, respectively. The inner interface bond coefficient is only 0.052, indicating that even the smooth steel pipe can work closely with the cement-soil at a low bonding coefficient. Further optimization of the steel-pipe–cement-soil interface structure can be an essential means to improve the mechanical properties of the pile. When the upper load is transferred downward, it spreads around through the cement-soil, and as the load increases, the load that can finally be transferred to the deep part accounts for a relatively small amount, only about 7%. This work promotes the understanding of the interface mechanical properties of ESDCM piles and guides the application of an ESDCM pile with a steel core in practical engineering.

Fissures and holes widely exist in rock mechanics engineering, and, at present, their failure mechanisms under complex compress and shear stress states have not been well recognized. In our work, a fracture mark, ξ, is introduced, and the kernel function of the smoothed-particle hydrodynamics (SPH) is then re-written, thus realizing the fracture modelling of the rock media. Then, the numerical models containing the fissures and holes are established, and their progressive failure processes under the compress and shear stress states are simulated, with the results showing that: (1) the improved SPH method can reflect the dynamic crack propagation processes of the rock masses, and the numerical results are in good agreement with the previous experimental results. Meanwhile, the improved SPH method can get rid of the traditional mesh re-division problems, which can be well-applied to rock failure modeling; (2) the hole shapes, fissure angles, fissure lengths, fissure numbers, and confining pressure all have great impacts on the final failure modes and peak strengths of the model; and (3) in practical engineering, the rock masses are in the 3D stress state, therefore, developing a high performance 3D SPH program and applying it to engineering in practice will be of great significance.

In this study, surface treatment, using blended materials of nano-silica (NS) and magnesium potassium phosphate cement (MKPC) slurries containing four dosages of NS, was applied to recycled aggregate (RA) with distinct RA maintenance schemes to enhance the RA concrete (RAC) performance and control NS dosage for economy. The results imply that the NS + MKPC slurry can efficiently bolster the bonding with RA and the new interfacial transition zone (ITZ), contributing to a distinct enhancement of RAC’s macro-properties. Besides, the optimal NS dosage and RA maintenance scheme revealed by the simplified linear weighted sum optimization method were 3% and no pre-curing procedure, respectively. On the basis of the aforementioned optimal conditions, the modified RAC (C-3-N) achieved enhanced compressive strength by 40.75%, split tensile strength by 46.26%, and chloride ion penetration resistance by 65.93% in comparison with the untreated RAC0. Moreover, the advantages observed in C-3-N were attributed to the exceptional microstructural characteristics in both the NS + MKPC slurry and the new ITZ. This study establishes the potential to augment the efficacy of nanomaterials in reinforcing RAC and enhance the economic viability and practicability of RAC applications. Simultaneously, these advancements contribute to fostering sustainable development within the construction industry and yielding environmental benefits.