A More Realistic Study on the Mechanical Properties of CFRC Composite Grouting Material under a Long-Term Water Immersion Process

Yao Xiao,Jianlin Li,Eleyas Assefa,Huafeng Deng

doi:10.1155/2019/2736481

Abstract

The long-term effect of water immersion on the mechanical properties of CFRC composite grouting materials was studied by using five different carbon fiber contents (0, 0.25%, 0.50%, 0.75%, and 1.00%). The direct shear and long-term immersion tests were performed based on the specified and optimum values of carbon fiber content, respectively. The results showed the following: (1) the application of carbon fiber significantly improved the shear resistance of CRFC composite grouting material by using “reinforcing” and “anchoring” actions. The shear strength of the specimen was increasing by 5.66%∼43.41% when the carbon fiber content increased from 0.25% to 1.00%. After a comprehensive analysis, the optimum carbon fiber content was found to be 0.75%. (2) The degradation in the compressive and tensile strength of CRFC composite specimens exhibited a consistent trend (i.e., a steep gradient was gradually followed by a gentle slope) under a long-term water immersion process. About 90% of the total degradation in the compressive and tensile strength has occurred in 90 immersion days (i.e., 16.05% and 18.45%, respectively). In comparison, the degradation in the tensile strength (20.05%) was slightly higher than the compressive strength (18.16%). (3) Under the long-term water immersion process: the properties of the specimens were gradually deteriorating, the carbon fibers were gradually reaching a fatigue stage, and the bonding properties of carbon fiber was decreasing, which resulted in a reduction in the compressive and tensile strength. The uniaxial compression failure mode changed from brittle to ductile, and the development of local failure was very noticeable. Based on the findings of this paper, groundwater has a significant impact on the mechanical properties of grouted rock mass such as dam foundations and abutments. Therefore, the degradation in the grouting materials has to be considered in practical cases.

Highlights

Carbon fiber-reinforced cement (CFRC) composite material refers to a new composite material with cement as the substrate and carbon fiber as the reinforcement
E shear loading device is shown in Figure 3(b). e specimens were mounted on the testing device with a seating load and tested under different normal loads (0.5, 1.0, 1.5, 2.0, and 2.5 MPa). en, the shear load was applied at a controlled rate of deformation until residual strength was established. e uniaxial compression and splitting tensile tests have been conducted by using the RMT-150C rock mechanics test system (Figure 4(a)). e loading devices used for the uniaxial compression and split tensile strength tests are shown in Figures 4(b) and 4(c), respectively
Relative to the 0 carbon fiber content, the shear strength increased by 5.66%∼20.16%, 12.86%∼30.23%, 18.26%∼38.76%, and 22.64%∼43.41%, while the carbon fiber content increased from 0.25% to 1.00% at different normal stress levels

Summary

Introduction

Carbon fiber-reinforced cement (CFRC) composite material refers to a new composite material with cement as the substrate and carbon fiber as the reinforcement. It can prevent or delay the occurrence and expansion of deformation and failure of cement-based solids during the loading process, improve the mechanical properties such as flexural, tensile, antifreezing, and antiseepage, and achieve the strengthening and toughening effect of fiber materials [3,4,5,6]. It has very few negative impacts on the environment. Xiong et al [7], Hai et al [8], and Yu et al [9] performed uniaxial compression and tensile tests on composites with different carbon fiber

Methods

Results

Conclusion