Research on the Infrared Thermographic Detection of Concrete under Solar Heating

Dan Zheng,Haonan Cai,Shuaishuai Tan,Xinxin Li,Xianming Shi

doi:10.1155/2021/6692729

Dan Zheng, Haonan Cai + Show 3 more

Open Access

https://doi.org/10.1155/2021/6692729

Copy DOI

Abstract

Infrared thermography for detecting defects in concrete structures is closely related to the heat source and the optimized method of the thermal image. Due to the limitation of the irradiation area of the heat source, it is inefficient to detect the defects in large concrete structures. In this paper, sunlight was employed as a heat source to detect the defects with different sizes and depths in concrete, and the measured infrared images were processed and optimized by an enhancement algorithm. The experimental results showed that the defects in concrete could be rapidly identified under sunlight. The effect of environment, view angle, and boundary can be eliminated by image preprocessing, and the histogram equalization algorithm can increase the detection depth of the defects. The research results can also provide a reference for the infrared detection technology of concrete under the weak heat source.

Highlights

Nondestructive testing (NDT) of concrete is critical to evaluate the safety of structures, and infrared thermography (IRT) is one of the most important internal defect detection methods available
When the heating source is applied on the concrete, due to the poor thermal conductivity of the gas contained in the internal defects, energy could not pass through and accumulate on the top region of the defect, causing the surface temperature above the defect higher than the intact area. erefore, infrared thermography can be used to collect the surface temperature information and detect the internal defects in concrete [1, 2]. e variation of temperature in different parts of the concrete depends on the depth and size of the defects
Is unexpected phenomenon is caused by the working principle of the thermal imager. e brightness of the infrared image is directly proportional to the temperature. e thermal imager assigns the brightest color to the highest temperature and the darkest color to the lowest temperature

Summary

Introduction

Nondestructive testing (NDT) of concrete is critical to evaluate the safety of structures, and infrared thermography (IRT) is one of the most important internal defect detection methods available. E variation of temperature in different parts of the concrete depends on the depth and size of the defects. This method is not effective for detecting deep defects [3,4,5]. Maierhofer studied the influence of the size and depth of the cavity on the transient temperature curve under different heating times, realizing the locating of the internal defects in concrete [6]. Krishnendu compared the infrared inspection results of concrete under various heating methods and found that the high-resolution infrared images can be obtained by frequency modulation heating mode [10]

Methods

Results

Discussion

Conclusion