Surface Of Concrete Wall Research Articles

Segmentation of Concrete Cracks by Using Fractal Dimension and UHK-Net

Concrete wall surfaces are prone to cracking for a long time, which affects the stability of concrete structures and may even lead to collapse accidents. In view of this, it is necessary to recognize and distinguish the concrete cracks. Then, the stability of concrete will be known. In this paper, we propose a novel approach by fusing fractal dimension and UHK-Net deep learning network to conduct the semantic recognition of concrete cracks. We first use the local fractal dimensions to study the concrete cracking and roughly determine the location of concrete crack. Then, we use the U-Net Haar-like (UHK-Net) network to construct the crack segmentation network. Ultimately, the different types of concrete crack images are used to verify the advantage of the proposed method by comparing with FCN, U-Net, YOLO v5 network. Results show that the proposed method can not only characterize the dark crack images, but also distinguish small and fine crack images. The pixel accuracy (PA), mean pixel accuracy (MPA), and mean intersection over union (MIoU) of crack segmentation determined by the proposed method are all greater than 90%.

Numerical Investigation of Wind Erosion to the Grooved Concrete Wall Surface under a Wind‐Blown Sand Movement

Wind erosion to the grooved concrete wall surface under a wind‐blown sand movement was numerically studied. Particularly, the influencing factors that affect the wind erosion to the grooved concrete wall surface were systematically investigated by using the RNG k − ε turbulence model combined with the discrete phase model (DPM). It was found that, under a relatively low impact angle, the damage mechanism to the grooved wall surface is wind‐blown sand impact, and the erosion rates of the grooved wall surfaces are higher than those of the smooth wall surfaces. By contrast, under a relatively high impact angle, the damage mechanism to the grooved wall surface transfers to the microcutting effect, and the erosion rates show an opposite trend. The optimization rates between the erosion of grooved and smooth wall surfaces increase with increasing groove size or groove number. However, the damage mechanism to the grooved wall surface is hardly changed by expanding the groove area. The erosion rate distribution and the optimization rates of the groove wall surfaces are not significantly changed by adjusting the spacing between the grooves alone. When the groove shape changes from semicircular to rectangular, the erosion rate distribution is significantly changed, and the wear resistance of the changed grooved wall surface gets better.

Transforming thermal-radiative study of a climber green wall to innovative engineering design to enhance building-energy efficiency

The thermo-regulatory function of building-integrated climber vegetation has been verified. However, there is a need to increase in-situ observation studies on green walls installed on windowed building envelopes. This study presents results of instrumental monitoring of the thermal and radiative environment of a climber-green wall with windows to inspire a more energy-efficient green wall system design. This research is based in humid-subtropical Hong Kong, with reference to experimental controls (without vegetation cover) of a bare wall and a bare roof in sunny, cloudy and rainy weather in summer. The experimental results demonstrated lower short-wave reflectivity on green wall (0.13) than on control bare wall (0.30). Green wall received the thermal influence of long-wave terrestrial radiation as well as sky radiation. On sunny, cloudy and rainy days, the exterior concrete wall surface behind climber vegetation was cooler than control bare wall up to 6.6, 2.3 and 1.2 K respectively, and the posterior air gap shielded by the climbers was cooler than ambient air up to 2.2, 0.8 and 0.4 K. On sunny day, indoor wall surface and air of the green wall envelope were warmer at maximum by 1.4 and 1.3 K respectively, possibly contributed by the thermal bridge effect of the windows. On cloudy and rainy days, however, indoor surface and air experienced cooling by < 2.0 K. The evaluation of the thermal effects of windows on the indoor thermal regime led to the proposal of a rotatable green wall planter system, which could optimize daytime and nighttime thermal benefits by maximizing daytime shading-induced shielding against through-window insolation and nighttime radiative heat loss.

Automatic Detection of Concrete Spalling Using Piecewise Linear Stochastic Gradient Descent Logistic Regression and Image Texture Analysis

Recognition of spalling on surface of concrete wall is crucial in building condition survey. Early detection of this form of defect can help to develop cost‐effective rehabilitation methods for maintenance agencies. This study develops a method for automatic detection of spalled areas. The proposed approach includes image texture computation for image feature extraction and a piecewise linear stochastic gradient descent logistic regression (PL‐SGDLR) used for pattern recognition. Image texture obtained from statistical properties of color channels, gray‐level cooccurrence matrix, and gray‐level run lengths is used as features to characterize surface condition of concrete wall. Based on these extracted features, PL‐SGDLR is employed to categorize image samples into two classes of “nonspall” (negative class) and “spall” (positive class). Notably, PL‐SGDLR is an extension of the standard logistic regression within which a linear decision surface is replaced by a piecewise linear one. This improvement can enhance the capability of logistic regression in dealing with spall detection as a complex pattern classification problem. Experiments with 1240 collected image samples show that PL‐SGDLR can help to deliver a good detection accuracy (classification accuracy rate = 90.24%). To ease the model implementation, the PL‐SGDLR program has been developed and compiled in MATLAB and Visual C# .NET. Thus, the proposed PL‐SGDLR can be an effective tool for maintenance agencies during periodic survey of buildings.

Metaheuristic Optimized Edge Detection for Recognition of Concrete Wall Cracks: A Comparative Study on the Performances of Roberts, Prewitt, Canny, and Sobel Algorithms

Crack detection is a crucial task in the periodic survey of high‐rise buildings and infrastructure. Manual survey is notorious for low productivity. This study is aimed at establishing an image processing‐based method for detecting cracks on concrete wall surfaces in an automatic manner. The Roberts, Prewitt, Canny, and Sobel algorithms are employed as the edge detection methods for revealing the crack textures appearing in concrete walls. The median filtering and object cleaning operations are used to enhance the image and facilitate the crack recognition outcome. Since the edge detectors, the median filter, and the object cleaning operation all require the appropriate selection of tuning parameters, this study relies on the differential flower pollination algorithm as a metaheuristic to optimize the image processing‐based crack detection model. Experimental results point out that the newly constructed approach that employs the Prewitt algorithm can achieve a good prediction outcome with classification accuracy rate = 89.95% and area under the curve = 0.90. Therefore, the proposed metaheuristic optimized image processing approach can be a promising alternative for automatic recognition of cracks on the concrete wall surface.

Grasping Claws of Bionic Climbing Robot for Rough Wall Surface: Modeling and Analysis

Aiming at the inspection of rough stone and concrete wall surfaces, a grasping module of cross-arranged claw is designed. It can attach onto rough wall surfaces by hooking or grasping walls. First, based on the interaction mechanism of hooks and rough wall surfaces, the hook structures in claw tips are developed. Then, the size of the hook tip is calculated and the failure mode is analyzed. The effectiveness and reliability of the mechanism are verified through simulation and finite element analysis. Afterwards, the prototype of the grasping module of claw is established to carry out grasping experiment on vibrating walls. Finally, the experimental results demonstrate that the proposed cross-arranged claw is able to stably grasp static wall surfaces and perform well in grasping vibrating walls, with certain anti-rollover capability. This research lays a foundation for future researches on wall climbing robots with vibrating rough wall surfaces.

Thermal stress analysis of concrete wall of LNG tank during construction period

As the demand for energy growing rapidly these years, liquefied natural gas (LNG) has become one of the significant parts of the energy source for its high calorific value and performances, as well as the ease of transport and storage. Hence, increasing number of LNG tank has been constructed. The outer wall of LNG tank is usually made by reinforced concrete and the thermal induced cracking may occur during construction period because of the heat of hydration and concrete shrinkage. The finite element (FE) method was adopted in this paper to study the temperature and thermal stress distribution on the concrete wall of a 160,000 m3 LNG tank. The detailed FE model was first established and mesh convergence analysis was conducted to determine the suitable element size. The heat transfer analysis was conducted to obtain the temperature field on the concrete wall, based on which the incremental method was adopted to calculate the thermal stress. The thermal induced cracks distribution was then obtained by comparing the first principle tensile stress with the ultimate tensile stress of concrete. It was found that the cracks in vertical direction appeared at the concrete wall surface and the cracks in circumferential direction appeared at the buttress column surface. In addition, the major influence factors on the thermal stress were also investigated and the construction season and quality showed significantly effect on the thermal stress.

Experiment for Attaching Force of a Suction Fan on Various Concrete Wall Surfaces

In order to measure attaching performance of the suction fan against a concrete wall, test apparatus measuring suction force of the fan was developed. Using this test apparatus, four types of concrete wall specimens were tested to measure the attaching force. The test apparatus consisted of a fan motor, a pneumatic cylinder, a load cell, and sensors for vacuum pressure and a rotating speed of the fan. Vertical wall surface of concrete material were manufactured to four different shapes that is flat, step, rib and embossing type. When the fan is rotating in the fan-housing which is fixed by metal frame, the wall specimen is moved near to fan-housing edge by the pneumatic cylinder. And the specimen may be attached to fan-housing edge by suction force of the fan, and the wall specimen is reversely moved away from the fan-housing edge by the pneumatic cylinder. Then suction force of the fan was measured using a load cell. And the suction force was measured depending on specimen types and varying the rotation speed of the fan. Test result shows that the fan speed is proportional to the suction force, and interestingly, suction force is almost independent from the specimen shapes. The maximum suction force was equally measured with 231.9 N on the step and embossing type surface with 1,800 rpm.

Evaluation for activities of component of Cyclotron-Based Epithermal Neutron Source (C-BENS) and the surface of concrete wall in irradiation room

The workers employed in BNCT must enter the irradiation room just after an irradiation under the condition of remaining activities. To reduce the radiation exposure for the workers, it is important to identify the origins of the activities. In this research, the activities induced on the concrete wall surface were evaluated using MCNP-5 and the measurement results of thermal neutron distribution. Furthermore, the radioisotopes produced in the moderator were identified with a High Purity Germanium detector. It was found that the activities of the wall were mainly caused by (46)Sc, (60)Co and (152)Eu, and that (24)Na and (56)Mn were mainly produced in the moderator.

A Study on the Thermal Performance of the Living Wall System

PP-29-190 Background/Aims: This study aimed at framing alternative urban planning scenarios reflecting urban planning factors, performing urban climate simulation, and evaluating low energy characteristics from the viewpoint of urban temperature and energy savings. Methods: Monitoring thermometer of artificial ground greening to confirm its mitigation effect of plant evapotranspiration was carried out. Results: According to result of monitoring that, in case of green roof, surface of Grass was lower 2.37°C than surface of concrete and surface of Sedum was lower 3.57°C than surface of concrete in September. In case of green wall, surface of grass was lower 4.78°C than surface of concrete wall, surface of ivy was lower 2.55°C than surface of concrete wall in September. Therefore, it was found that green roof and green wall could have effect on mitigation of microclimate. Conclusion: The best results were recorded from the grass and Sedum surface presenting highest mitigation effect and lowest daily temperature deviation. From this monitoring, it was confirmed that artificial ground green can do its role of temperature mitigation as green does. Environmental Exposure and Health

Accelerated testing of biological stain growth on external concrete walls. Part 1: Development of the growth tests

The development of biological stains has a great influence on the durability of building materials. For common concrete structures, the main and most rapid disorder linked with this development is aesthetic. In recent years, architects have been increasingly using formwork surfaces for external walls, so the search for aesthetic quality and durability has become as important as the search for mechanical quality and durability. Hence, there is a demand from industry for the qualification of concrete wall surface behaviour toward biological growths. This paper aims to itemize the various biological stains affecting concrete and to put forward two accelerated tests for the growth of algae, the organisms responsible for the first visible stains. These tests enable a wall surface to be qualified with respect to biological stains.

Mechanism and prediction of material abrasion in high-velocity sediment-laden flow

The wall surface of material is prone to silt abrasion by high-velocity sediment-laden flow. The silt abrasion is different form cavitation erosion. In this article, the characteristics of silt abrasion were discussed. The mechanism of silt abrasion was analyzed and the formation and development of ripple shape on wall surface of material were explained thereafter. Based on turbulence theory and test data, some formulas were derived for predicting the abrasion rate of concrete wall surface in high-velocity sediment-laden flow. The calculated results show good agreement with the experimental data.

Enhancements in surface quality of concrete through use of controlled permeability formwork liners

This report presents results of a study to compare the performance of concrete wall surfaces cast against controlled permeability formwork (CPF) liners with that of concrete surfaces cast against conventional impermeable plywood formwork Two formwork liners were used, namely 'Zemdrain', a proprietary spun-bonded formwork liner manufactured by Dupont, and 'Lotrak FL', a woven geotextile manufactured by Don &amp; Low. A variety of test methods were used to assess performance, including surface hardness, initial surface adsorption, sorptivity, depth of carbonation, chloride penetration and freeze–thaw resistance. In addition, the quality of the surface finish was assessed visually. Two concrete mixes and two different curing regimes were tested. The variation in surface quality of concrete with depth from the top of the pour was also examined. Results demonstrate that surface qualities of concrete can be markedly improved by use of CPF liners. The two liners produced identical enhancements in surface quality. They differed in one aspect of performance only, as cement particles were able to travel through the Lotrak fabric and to bond to the backing plywood, necessitating cleaning of the plywood after each cast. This problem did not arise with Zemdrain. Effectiveness of CPF liners was slightly greater for the lower grade mix and slightly lower close to the top of a pour. It is also observed that measured enhancements in performance may be strongly influenced by test duration.

Causes of Poor Sealant Performance in Soil-Gas-Resistant Foundations

Sealants for radon-resistant foundation construction must seal the gap between concrete sections. Modern sealants have such low permeability that seal performance depends only on the permeability of the material that contacts the sealant. The surface permeability of concrete walls and floors was measured by a specially designed permeameter, which measures the airflow induced by a pressure difference across a temporary test seal applied to the surface. The permeability of bulk concrete is about 10−16 m2. Areas free of the surface defects had surface permeability ranging from 10−14 to 10−16 m2. However, surface defects are common on concrete wall surfaces, which increase the permeability to > 10−12 m2, too high for standard seal designs to be adequate as the only method of soil gas and radon exclusion. Radon-resistant seals require either extended contact widths or mechanical removal of the surface layer and defects.

The susceptibility of a mosquito species (Culex pipiens quinquefasclatus) to the insecticides, malathion, DDT and UBMT in the Sudan savanna zone of Nigeria

The susceptibility of adult females of Culex pipiens quinquefasciatus to malathion, dichlorodiphenyl trichloroethane (DDT), and 1 – (- dimethylaminobenzylidene) – 3 -methylthiotriazene (DBMT) was assessed by residual application using the World Health Organisation’s (WHO) standard susceptibility test method on the Main Campus, Ahmadu Bello University, Zaria. Also the susceptibility and contact bioassay studies were carried out on the larvae of this species for malathion and DBMT. The results obtained indicate that DBMT has insecticidal property on both larval and adult C.p. quinquefasciatus. Of the three insecticides tested, malathion was the most effective at high concentration while DBMT was the most effective at low concentration. C.p. quinquefasciatus has high resistance to DDT. The larvae were more susceptible to malathion than DBMT, the latter being poorly larvicidal. The results of the residual application test on a concrete wall surface indicate that malathion is much more stable than DBMT.