Study of Rheological Properties of Carbon Nanotube-Reinforced Ultrafine Cement Grouting Materials

In this study, three different diameters of multi-walled carbon nanotubes (MWCNTs) dispersed by polyvinyl pyrrolidone (PVP) were used to reinforce superfine cement grouting materials. The effect of MWCNTs and polyvinyl pyrrolidone (PVP) on the rheological properties of grouting material were accordingly studied. It was found that the yield stress (τ0) and plastic viscosity (η) were slightly decreased when PVP content was low and increased when the PVP content increased. The effect of MWCNT diameter on τ0 was not found to be clear but was more significant on η. The smaller MWCNT diameter was, the more quickly η increase. It was also found that the thixotropic ring area was increased as the MWCNTs content increased. The addition of PVP and MWCNTs caused an increase in the number of entanglement points in different scales, which was the main reason for the viscosity and thixotropy increase. Therefore, the rheological properties of superfine cement grouting material should be adjusted when MWCNTs were added as a reinforcing component. Due to the wrapping of PVP on cement particles which isolates the contacting part between the water and the cement particles, it slows down the cement's hydration rate thus slows down the fluidity loss of the slurry.

High-Fluidization, Early Strength Cement Grouting Material Enhanced by Nano-SiO2: Formula and Mechanisms

Cement grouting material is one of the most important materials in civil construction at present, for seepage prevention, rapid repair, and reinforcement. To achieve the ever-increasing functional requirements of civil infrastructures, cement grouting materials must have the specific performance of high fluidization, early strength, and low shrinkage. In recent years, nanomaterials have been widely used to improve the engineering performance of cement grouting materials. However, the mechanisms of nanomaterials in grouting materials are not clear. Hence, a high-fluidization, early strength cement grouting material, enhanced by nano-SiO2, is developed via the orthogonal experimental method in this study. The mechanisms of nano-SiO2 on the microstructure and hydration products of the HCGA, in the case of different curing ages and nano-SiO2 contents, are analyzed through scanning electron microscopy tests, X-ray diffraction tests, differential scanning calorimetry tests, and Fourier transform infrared spectroscopy tests.

Research on Grouting Materials for Underground Construction Projects

The engineering practice shows that the application of grouting technology to treat underground engineering has strong applicability and is one of the most commonly used technical means at present. Based on the underground engineering, this paper introduces the research achievements of grouting materials in recent years, including cement-based grouting materials, mixed grouting materials, anti-scouring grouting materials, and ultra-fine cement grouting materials. Current demand of grouting materials in underground engineering, there exists large dosage of cement, high content, high cost, serious environmental pollution problems, such as looking for alternatives or mixed with other raw materials for preparation of cementation material become the development trend, compared with the cement grouting material, chemical grouting material with higher performance, but in smaller projects within the scope of application. How to reduce the production cost of chemical grouting materials, simplify the production process, overcome the existing toxicity, reduce environmental pollution and improve the durability of solidified body has become the bottleneck of its popularization and application. Some achievements have been made in the modification of cement or chemical materials by nanometer components, but there is still a long way to go before the large-scale application of grouting engineering.

EXPERIMENTAL STUDY ON THE MECHANICAL AND DEFORMATION PROPERTIES OF PIPE AND SOIL IN RECTANGULAR PIPE JACKING CONSTRUCTION WITH CONTROLLABLE CEMENT GROUTING TECHNOLOGY

Based on the utility tunnel project of Chengbei Road in Suzhou, the experimental study on the mechanical and deformation properties of pipe and soil in rectangular pipe jacking construction with controllable cement grouting drag reduction technology is carried out. Based on the monitoring and analysis of pipe and soil stress and deformation of pipe joints during pipe jacking, the relevant theoretical model is established and the finite element simulation is carried out to experimentally study and compare the stress and deformation of pipe and soil in rectangular pipe jacking construction with controllable cement grouting drag reduction technology. The results show that the controllable cement grouting drag reduction technology has a significant effect on the pipe and soil stress in rectangular pipe jacking, which reduces pipe-soil interaction forces effectively, and improves the overall safety of pipe jacking construction.

Technologies for the formation of soil-cement massifs when developing underground space in reclaimed lands and artificial islands

In order to harden or increase the soil impermeability formed when constructing hydraulic territories, injection cement-grouting technology can be effectively applied. Its obvious advantages include environmental safety, manufacturability, durability, and economic attractiveness. The soil conditions of artificial territories are characterized by extreme uniformity, which necessitates the use of various technical solutions for their hardening. The experience of applying various soil injection cement-grouting technologies that provide the specified efficiency of the design decisions made has been analyzed in the report.