Recent progress on flexible and stretchable piezoresistive strain sensors: From design to application

Nano-engineering cement binder using a hybrid of carbon nanotubes (CNTs) and graphene oxide (GO) combines the superior mechanical properties of CNTs and the good dispersibility and affinity of GO. Ultrasonication is a key process implemented in the dispersion of CNTs and GO. The present study characterizes the effect of ultrasonication on the dispersion and size of the GO/CNT particles by using an ultraviolet spectrophotometer and Zetasizer μV detector, respectively. The mechanical properties of GO/CNT-OPC pastes treated with different ultrasonication time and power levels were tested and their microstructure was investigated using scanning electron microscopy and mercury intrusion porosimetry. The results of this study not only reveal that differences in ultrasonication can cause the mechanical properties of the GO/CNT-OPC composite to vary by −11.7–78.8% but also show that the effect of the amount of ultrasonication energy can vary significantly when different ultrasonication time or power levels are adopted. The porosity of the composite is found to have a nonlinear correlation with the ultrasonication. The findings of this study can promote understanding of GO/CNT-OPC composites and help to guide the implementation of ultrasonication in the future.

Influence of ultrasonication on the dispersion and enhancing effect of graphene oxide–carbon nanotube hybrid nanoreinforcement in cementitious composite

Experimental study on performance of cement-based grouts admixed with fly ash, bentonite, superplasticizer and water glass

Proceedings of the eighteenth annual ACM-SIAM symposium on discrete algorithms

Improving the strength of weak soil using polyurethane grouts: A review

Grouting is a major method used to prevent water and mud inrush in tunnels and underground engineering. In this paper, the current situation of control and prevention of water and mud inrush is summarized and recent advances in relevant theories, grout/equipment, and critical techniques are introduced. The time-variant equations of grout viscosity at different volumetric ratios were obtained based on the constitutive relation of typical fast curing grouts. A large-scale dynamic grouting model testing system (4000 mm × 2000 mm × 5 mm) was developed, and the diffusions of cement and fast curing grouts in dynamic water grouting were investigated. The results reveal that the diffusions of cement grouts and fast curing grouts are U-shaped and asymmetric elliptical, respectively. A multi-parameter real-time monitoring system ( ϕ  = 1.5 m, h  = 1.2 m) was developed for the grouting process to study the diffusion and reinforcement mechanism of grouting in water-rich faulted zone. A high early strength cream-type reinforcing/plugging grout, a high permeability nano-scale silica gel grout, and a high-expansion filling grout were proposed for the control of water hazards in weak water-rich faulted zone rocks, water inrush in karst passages, and micro-crack water inrush, respectively. Complement technologies and equipment for industrial applications were also proposed. Additionally, a novel full-life periodic dynamic water grouting with the critical grouting borehole as the core was proposed. The key techniques for the control of water inrush in water-rich faulted zone, jointed fissures and karst passages, and micro-crack water inrush were developed.

Protection against water or mud inrush in tunnels by grouting: A review

Quick-setting grout has been widely used in sealing underground excavations to prevent water ingress. Cement and sodium silicate grout (C–S grout), a typical quick-setting slurry, is becoming increasingly more popular in fracture-sealing grouting operations in China because of its short gel time, high early strength and sufficient sealing efficiency. C–S grout contains a cement slurry and sodium silicate solution. During the process of mixing and pouring these two components into the rock fracture, the viscosity of the grout suspension varies over time, which has a considerable influence on the fracture grouting of the C–S slurry. In this study, analytical expressions were derived by implementing the mass conservation equation and radial grouting flow behavior and considering the time-varying slurry viscosity. These governing equations can be used to evaluate the propagation of C–S grout in a planar fracture. Also, the effects of the main factors on the penetration length were investigated, revealing that the rheology of the C–S grout is inherently related to the influence of other parameters, such as injection pressure, injection rate and fracture aperture width, on the fracture grouting. The validation of the proposed approach is examined by comparing the simulation results with the published experimental data. The simulated grouting pressure and pressure distribution in the grouted zone are consistent with experimental observations.

Rentai Liu

Papers

Protection against water or mud inrush in tunnels by grouting: A review

Experimental study on performance of cement-based grouts admixed with fly ash, bentonite, superplasticizer and water glass

Grouting rock fractures with cement and sodium silicate grout

Grouting mechanism of quick setting slurry in rock fissure with consideration of viscosity variation with space

Investigation on fundamental properties of microfine cement and cement-slag grouts