Detection of Concrete Cover of Reinforcements in Reinforced Concrete Wall by Microwave Thermography with Transmission Approach

Abstract

Concrete cover has an important role in reinforced concrete (RC) structures because it protects reinforcement bars from the bad effects of weather, fire, and bad environmental conditions that cause the corrosion of the reinforcements. Although it is an essential parameter to be considered for structural health monitoring (SHM), its detection by infrared thermography, especially in the heating phase, has not been accessed yet. The detailed analysis and discussions of physical phenomena, known as diffraction and interference, affecting the thermograms during the detection of the steel bars by microwave thermography have given an essential key for resolving this issue. The present paper proposes an innovative methodology with microwave thermography for determining the concrete cover thickness of one-layer reinforcements (12 mm in diameter and regularly placed at 10 cm) in an RC wall (1 m × 1m × 6.5 cm). By using the transmission approach with five angles of microwave antenna direction (0°, 15°, 30°, 45°, and 60°) and the Snell–Descartes law and linear law, the proposed methodology leads us to deduce the approximate value of the concrete cover thickness (37.74 mm), which is close to the real value (38 mm), as well as the spacing of the steel bars and dielectric constant of the concrete. The detection of the concrete cover thickness is another new remarkable achievement of infrared thermography methods.

Defect Detection in CFRP Concrete Reinforcement Using the Microwave Infrared Thermography (MIRT) Method—A Numerical Modeling and Experimental Approach

“…Microwave heating has been widely employed in the literature for various purposes related to concrete structures, including expediting the curing process, decontaminating cement, and facilitating the drilling or melting of concrete [24][25][26][27]. In this proposal, microwaves are suggested as a potential energy source for infrared thermography [28][29][30][31][32][33][34]. The primary benefit of utilizing microwave heating lies in its volumetric nature.…”

A Comparative Analysis of the Magnetization Methods Used in the Magnetic Nondestructive Testing of Reinforced Concrete Structures

“…Moreover, the method required heating and cooling-down phases, which makes it time-consuming. Therefore, it is not commonly used in practice [6,30,[45][46][47][48][49][50]; 3.…”

Investigation of Carbon Fiber Reinforced Polymer Concrete Reinforcement Ageing Using Microwave Infrared Thermography Method

“…An additional advantageous aspect of this approach is its non-invasive characteristic, which is particularly valuable in situations when direct entry to the object under investigation is not possible and assessment from a distance is required. In the microwave infrared thermography (MIRT) method, the heating ratio of this alternative energy source is influenced by both thermal and electrical properties, specifically the dielectric constant [38,45]. In the case of conductive materials such as CFRP, microwave heating is limited by a shallower depth of penetration.…”