Quantitative Infrared Thermography to Evaluate the Humidification of Lightweight Concrete

Self Cite

Infrared thermography (IRT) is a technique increasingly used in building inspection. If in many applications it is sufficient to analyze the thermal patterns, others exist in which the exact determination of the surface temperature is a fundamental aspect. In these circumstances, the emissivity of the surfaces assumes special relevance, being probably the most important property in the definition of the boundary conditions. However, information on the uncertainty involved in its measurement, as well as the conditions that influence it, is scarce. This article presents an innovative contribution both to the characterization of the emissivity of various construction materials, and to the discussion of emissivity measurement procedures and the attendant uncertainty. In this sense, three experimental campaigns were carried out: T.I, preliminary tests to assess the initial conditions required for an accurate IRT measurement of the emissivity (reference tape and position of the camera); T.II, assessment of the emissivity of nine different building materials, in dry conditions, using the emissometer and the IRT and black tape methods; and T.III, assessment of the emissivity of three materials during the drying process. The results confirmed that emissivity is a crucial parameter for the accurate measurement of surface temperature. Emissivity measurements carried out with IRT (black tape method) and with the emissometer returned meaningful differences when compared with the values available in the literature. This disagreement led to surface temperature differences of up to 7 °C (emissometer versus reference values). This research also highlighted that the moisture content of the materials influences the emissivity values, with fluctuations that can be greater than 10%, and that the effect of moisture is visible even for low values of moisture content.

Section: Resultsmentioning

confidence: 99%

Emissivity of Building Materials for Infrared Measurements

Barreira

Almeida

Simões

2021

Self Cite

“…Tukey in 1977 [ 26 ]. The boxplot method is widely used in the scientific literature as descriptive statistics for graphically depicting groups of data through their quartiles [ 27 ]. This plotting method is based on drawing a box from the first quartile (Q1) to the third quartile (Q3), a central mark indicating the median, and extending lines indicating variability outside the interquartile range (IQR), computed as the distance between the third and first quartile (IQR = Q3 − Q1), a value that represents 50% of the distributed data.…”

Section: Methodsmentioning

confidence: 99%

Suboptimal Omnidirectional Wheel Design and Implementation

Palacín

Martínez

Rubies

et al. 2021

The optimal design of an omnidirectional wheel is usually focused on the minimization of the gap between the free rollers of the wheel in order to minimize contact discontinuities with the floor in order to minimize the generation of vibrations. However, in practice, a fast, tall, and heavy-weighted mobile robot using optimal omnidirectional wheels may also need a suspension system in order to reduce the presence of vibrations and oscillations in the upper part of the mobile robot. This paper empirically evaluates whether a heavy-weighted omnidirectional mobile robot can take advantage of its passive suspension system in order to also use non-optimal or suboptimal omnidirectional wheels with a non-optimized inner gap. The main comparative advantages of the proposed suboptimal omnidirectional wheel are its low manufacturing cost and the possibility of taking advantage of the gap to operate outdoors. The experimental part of this paper compares the vibrations generated by the motion system of a versatile mobile robot using optimal and suboptimal omnidirectional wheels. The final conclusion is that a suboptimal wheel with a large gap produces comparable on-board vibration patterns while maintaining the traction and increasing the grip on non-perfect planar surfaces.

“…Specifically, the parameter Evaporative Thermal Index (ETI) is calculated for each final candidate in order to establish different levels of moisture severity. The ETI was proposed by Tavukçuoğlu and Grinzato [ 65 ] and Grinzato et al [ 66 ], and it is defined as the estimation of the evaporation rate on the superficial moisture area, allowing the calculation of the critical moisture content of materials without considering the distribution of moisture inside the surface [ 27 ]. Therefore, the ETI parameter allows the identification of the most severe areas of superficial moisture and the establishment of different levels of deterioration on the zones affected.…”

Section: Methodsmentioning

confidence: 99%

“…Recent IRT papers describing specific studies (not reviews) include the work by Barreira et al [ 27 ], where the partial humidification of a lightweight concrete specimen is quantitatively evaluated through a thermal image sequence and by the application of a pre-processing step for data reduction, followed by a data processing step consisting of the application of different statistical and numerical methods. Furthermore, the automatic detection and delimitation of moisture areas affecting the surface is performed by analysing the temperature distribution of the thermal images acquired from several internal white plaster walls and on a concrete building façade [ 28 ].…”

Section: Introductionmentioning

confidence: 99%

IRT and GPR Techniques for Moisture Detection and Characterisation in Buildings

Garrido

Solla

Lagüela

et al. 2020

The integrity, comfort, and energy demand of a building can be negatively affected by the presence of moisture in its walls. Therefore, it is essential to identify and characterise this building pathology with the most appropriate technologies to perform the required prevention and maintenance tasks. This paper proposes the joint application of InfraRed Thermography (IRT) and Ground-Penetrating Radar (GPR) for the detection and classification of moisture in interior walls of a building according to its severity level. The IRT method is based on the study of the temperature distribution of the thermal images acquired without an application of artificial thermal excitation for the detection of superficial moisture (less than 15 mm deep in plaster with passive IRT). Additionally, in order to characterise the level of moisture severity, the Evaporative Thermal Index (ETI) was obtained for each of the moisture areas. As for GPR, with measuring capacity from 10 mm up to 30 cm depth with a 2300 MHz antenna, several algorithms were developed based on the amplitude and spectrum of the received signals for the detection and classification of moisture through the inner layers of the wall. In this work, the complementarity of both methods has proven to be an effective approach to investigate both superficial and internal moisture and their severity. Specifically, IRT allowed estimating superficial water movement, whereas GPR allowed detecting points of internal water accumulation. Thus, through the combination of both techniques, it was possible to provide an interpretation of the water displacement from the exterior surface to the interior surface of the wall, and to give a relative depth of water inside the wall. Therefore, it was concluded that more information and greater reliability can be gained by using complementary IRT-GPR, showing the benefits of combining both techniques in the building sector.