Research on Real-Time Monitoring of Strain Behavior of Concrete under Freezing-Thawing Cycle by White Light Interferometer

Haifeng Lv,Xuefeng Zhao,Xianglong Kong,Changsen Sun,Jie Ren,Zhengyang Song

doi:10.1155/2022/8049092

Abstract

To study the degenerative process of concrete subjected to freezing-thawing (F-T) cycles in real-time, the strain behavior of concrete cylinder was monitored by a fiber optic F-T testing method based on the white light interferometer (WLI) technique. The principle of the WLI technique was described in detail and the design of the fiber optic testing method. Two mixed proportions of concrete immersed in 3.5% NaCl solution were tested in a freeze-thaw testing machine. The theory and method of temperature compensation were stated in detail. The results indicated that the variation of strain decreases in the cooling stage and increases in the heating stage in a F-T cycle. The residual strain was generated in the test.

Highlights

In cold regions, F-T cycling is one of the main reasons for degradation of concrete materials because of the pore water.e change of dimensional and internal stress will be caused during the F-T cycles, which can result in degeneration and failure of concrete structures [1, 2].Nowadays, the loss of weight and relative dynamic modulus of elasticity are the most popularly used to evaluate the F-T resistance of concrete [3,4,5]
Bishnoi [22] embedded the strain gauges in concrete to measure the inner strain, and the results demonstrated that the inner strain increases with the progress of deterioration
Concrete specimens with 0.55 and 0.35 water-cement ratios (W/C), which were immersed in 3.5% NaCl solution, were tested in a temperature chamber to simulate the F-T environment and chloride salt attack. e theory and method of temperature compensation were stated in detail, and the strain behavior of T-specimen was monitored and studied during the F-T cycles

Summary

Introduction

F-T cycling is one of the main reasons for degradation of concrete materials because of the pore water. Other indicators are used to evaluate the degradation of concrete subjected to F-T cycles, such as dimensional change [6] and strength [7, 8] These indicators differ in the testing methods and evaluation criteria. The nondestructive testing methods are introduced to assess degeneration of materials, which are the fundamental transverse frequencies [17]and acoustic emission [18, 19] None of these methods could achieve real-time monitoring the damage evolution of concrete during freezing-thawing cycles. In this study, based on the WLI technology, a real-time monitoring method was proposed, and the strain behavior of concrete cylinder was monitored during the F-T cycles. The mechanism of F-T degeneration was analyzed from the perspective of strain

The Principal of WLI

Experimental Methodology

Experimental Results

Conclusions