Surface Deterioration Research Articles

Erosion‐Corrosion of Materials in Industrial Equipment: A Review

AbstractErosion‐corrosion (E−C) is one of the most intense forms of metal degradation observed whenever a static metallic material is in contact with dynamic liquid. Efficiency of industrial plant mainly depends upon the condition of various components of the equipment. Collective mechanism of corrosion and erosion results in severe surface deterioration with heavy material loss due to synergistic effect. Erosion‐corrosion is mainly observed in the pipelines used in oil and gas industries, petroleum industries, heat exchanges and mainly in marine equipment. Free flowing saline water, containing different grades of sand particles adversely affect marine equipment. Numerous reports are available discussing the impact of erosion‐corrosion in chemical industries. Single report documenting all types of prototypes, comparative study of erosion corrosion of various engineering materials and control techniques is highly limited. This review gives vivid account of various types of prototypes, comparative study of erosion‐corrosion of various engineering materials, various factors affecting tribology of system and control techniques is a systematic way. Application of corrosion inhibitors appears to be an effective method to reduce erosion‐corrosion. This review highlights the importance of understanding the mechanism of erosion‐corrosion in industrial equipment and provides a succinct overview of erosion‐corrosion synergism.

Characterization of Cementitious Materials Exposed to Freezing and Thawing in Combination with Deicing Salts Using 3D Scans

Surface deterioration of concrete subjected to freezing and thawing in combination with deicing salts is one of the most important factors determining the durability of concrete infrastructure in cold climates. The freeze–thaw deicing salt (FTDS) resistance of cementitious materials can be determined by the capillary suction of de‐icing chemicals and freeze–thaw (CDF) test. Specimens are subjected to repeated freeze–thaw cycles with simultaneous addition of deicing salt and the amount of material scaled off near the surface is determined. For concretes with adequate FTDS resistance, this test method works very well. However, specimens with unknown performance often experience increased edge scaling. This leads to a falsification of results and consequently to an underestimation of the actual freeze–thaw resistance. In materials research, however, concretes with high levels of surface deterioration are studied in order to investigate various factors of influence on the freeze–thaw resistance of concretes in a targeted manner. This article presents a novel methodology that delivers new information regarding surface deterioration of CDF samples using high‐resolution 3D scan data. Change of volume is used to support deterioration results of the standard CDF methodology. Increase of surface area is used to estimate change in roughness of samples.

Effect of chloride concentration on the corrosion resistance of pure Zn metal in a 0.0626 M H2SO4 solution

Abstract The aftermath of Cl− anion concentration reactions on the corrosion resistance of pure Zn metal in 0.0625 M H2SO4 was examined by potentiodynamic polarization, optical representations, scanning electron image analysis, energy dispersive X-ray (EDX) spectroscopy, open-circuit potential analysis, X-ray diffractometry, weight loss method and X-ray fluorescence. The results show that the degradation of Zn increased with an increase in the chloride concentration from 4.089 and 0.218 mm/year to 10.085 and 4.015 mm/year (polarization and weight loss). The corrosion potential at 0.0625 M H2SO4 to 0.0625 M H2SO4/0.5% NaCl concentration displayed minimal variation (−1.535 to −1.519 V), whereas a significant shift was observed for the plots at 0.0625 M H2SO4/1% NaCl and 0.0625 M H2SO4/2% NaCl (−1.384 and −0.932 V). The weight loss plot at all Cl− anion concentrations displayed an ordered decrease in the corrosion rate analogous to exposure times. The scanning electron microscopic images of Zn in 0.0625 M H2SO4/2% NaCl solution showed significant deterioration and corrosion pits. The image at 0.0625 M H2SO4 solution revealed limited localized and general surface deterioration, while the corresponding EDX data depict the presence of S. The Zn open-circuit potential plot from a 0.0625 M H2SO4 solution was relatively electropositive compared to the plot from a 0.0625 M H2SO4/2% NaCl solution. Both plots exhibited limited reactive-inert transition properties and attained relative thermodynamic equilibrium after 600 s of exposure with final corrosion potentials of −0.91 and −0.97 V at 7,200 s. Zn was the only crystallographic phase identified on its surface before corrosion, whereas ZnS, ZnFes, ZnMnS, ZnMnFeS, and ZnMg4 corrosion products were identified after corrosion.

A Facile and Green Microwave‐Assisted Strategy to Induce Surface Properties on Complex‐Shape Polymeric 3D Printed Structures

AbstractLight‐ induced polymeric 3D printing is becoming a well‐established fabrication method, showing manifold advantages such as control of the local chemistry of the manufactured devices. It can be considered a green technology, since the parts are produced when needed and with minimum amount of materials. In this work 3D printing is combined with another green technology, microwave‐assisted reaction, to fabricate objects of complex geometry with controllable surface properties, exploiting the presence of remaining functional groups on the surface of 3D printed specimens. In this context, surface functionalization with different amines is studied, optimizing formulations, reaction times, and avoiding surface deterioration. Then, two different applications are investigated. MW‐functionalized filter‐type structures have been tested against Staphylococcus aureus bacteria, showing high bactericidal activity on the surface along all areas of the complex‐shaped structure. Second, a fluidic chip composed of three separated channels is 3D printed, filled with different amine‐reactive dyes (dansyl and eosine derivatives), and made to react simultaneously. Complete and independent functionalization of the surface of the three channels is achieved only after 2 min of irradiation. This study demonstrates that light induced 3D printing and microwave‐induced chemistry can be used together effectively, and used to produce functional devices.

Corrosion mitigation on orthodontic wire made of SS 18/8 alloy using esomeprazole tablet (Esiloc-40 mg) in artificial saliva

The corrosion inhibition of orthodontic wire made of SS 18/8 alloy in artificial saliva, with and without the presence of tablet esomeprazole − 40 mg has been investigated by electrochemical analysis. Polarisation study indicates that in the presence of the mentioned tablet, polarisation resistance (Rp) value increases and corrosion current (Icorr) decreases. That is, the corrosion resistance of SS 18/8 alloy in artificial saliva increases. AC impedance spectroscopy reveals that charge transfer resistance value (Rct) value increases and double layer capacitance value (Cdl) decreases. The open circuit potential (OCP) values for the inhibited system are more negative than that of the uninhibited blank system. The vibration peaks obtained from the FTIR spectra indicates the presence of functional group in esomeprazole pill and these characteristic peaks are slightly shifted in the analyzed scratched film from the surface of the orthodontic wire after immersion. AFM micrograph image of the polished specimen sample immersed in artificial saliva (AS) with esomeprazole tablet solution shows lesser degree of surface deterioration than those for SS 18/8 specimen immersed only in artificial saliva. From the present work, it is reported that people clipped with orthodontic wire made of SS 18/8 alloy need not worry about orthodontic corrosion for taking esomeprazole tablet for the treatment of gastro esophageal reflux disease and other medicinal purpose.

Abrasion Characteristics of Exposed Aggregate Concrete Pavements under Surface Deterioration

This study compares the abrasion characteristics of concrete pavements with exposed aggregates and transverse tining textures under surface deterioration conditions. Deicer scaling resistance tests and dressing wheel abrasion tests were conducted to simulate surface deterioration under environmental and wheel loading conditions, respectively. Dressing wheel abrasion tests showed that the abrasion depths in concrete with 8 mm and 10 mm exposed aggregate textures were 43% and 36% lower, respectively, than those with transverse tining surface textures. After 40 cycles of the deicer scaling resistance test, the abrasion depth in the tining surface textured concrete did not satisfy the abrasion criterion of concrete pavements. Therefore, the long-term durability of the exposed aggregate texture can be ensured against abrasion and surface deterioration resistance during the pavement service life.

Analysis of Building Accessibility Using Inertial and Optical Sensors.

The inclusive use of urban spaces necessitates detailed knowledge of the accessibility of public buildings or places where educational, health or administrative services are provided. Despite the improvements already made in many cities regarding architectural work, further changes to public buildings and other spaces, such as old buildings or areas of historical importance, are still required. To study this problem, we developed a model based on photogrammetric techniques and the use of inertial and optical sensors. The model allowed us to perform a detailed analysis of urban routes in the surroundings of an administrative building, by means of mathematical analysis of pedestrian routes. It was applied to the specific case of people with reduced mobility and included analysis of the building accessibility as well as detection of suitable transit routes, deterioration of the road surfaces and the presence of architectural obstacles on the route.

Empirical Study of Surface Deterioration Analysis Based on Random Fields for Reinforced Concrete Structures in Marine Environment.

Corrosion-induced deterioration of the in-service marine reinforced concrete (RC) structures may result in unsatisfactory serviceability or insufficient safety. Surface deterioration analysis based on random fields can provide information regarding the future development of the surface damage of the in-service RC members, but its accuracy needs to be verified in order to broaden its applications in durability assessment. This paper performs an empirical study to verify the accuracy of the surface deterioration analysis based on random fields. The batch-casting effect is considered to establish the "step-shaped" random fields for stochastic parameters in order to better coordinate their actual spatial distributions. Inspection data from a 23-year-old high-pile wharf is obtained and analyzed in this study. The simulation results of the RC panel members' surface deterioration are compared with the in-situ inspection results with respect to the steel cross-section loss, cracking proportion, maximum crack width, and surface damage grades. It shows that the simulation results coordinate well with the inspection results. On this basis, four maintenance options are established and compared in terms of the total amounts of RC panel members needing restoration and the total economic costs. It provides a comparative tool to aid the owners in selecting the optimal maintenance action given the inspection results, to minimize the lifecycle cost and guarantee the sufficient serviceability and safety of the structures.

NSF (Nylon Synthetic Fiber) Effectiveness in Stabilizing Weak Subgrade Soil: An Experimental Investigation

Improvement in subgrade soil has always been an area of concern for highway and geotechnical engineers. Weak subgrade soil results in a greater thickness of the pavement layer, which increases the cost of pavement construction. It further leads to large deformations, which in turn cause continuous deterioration of the paved surface. To solve this problem, various engineering solutions and soil improvement mechanisms were previously proposed. This study was designed to investigate the stabilization of weak subgrade soil with nylon synthetic fiber (NSF) in a compromising combination. Previously, some investigations used a lower fiber content with a higher fiber length, whereas others used a lower fiber length with a higher fiber content. However, this investigation was uniquely designed to stabilize weak subgrade soil with the consideration of appropriate fiber length (10 mm and 20 mm) and content (0.5%, 1%, 1.5%, and 2.5%). The engineering properties of the soil, the effect of NSF on weak subgrade soil, various fiber content and aspect ratios, and the optimum content and critical fiber aspect ratio were investigated in a laboratory. The effect of fibers on compaction, CBR values, and CBR swell values has also been studied. Laboratory results on the modified compaction tests showed that maximum dry density (MDD) was increased with the increment of fiber content, whereas optimum moisture content (OMC) remained constant. The soaked CBR and CBR swell values of natural soil were 1.80% and 8.95%, respectively. Due to reinforcement, the percentage increase in soaked CBR value at the optimum NSF content is 265.3, 310.0, 282.8, and 342.2 for aspect ratios of 33.33, 66.67, 25, and 50, respectively, with reference to natural soil. Also, the percentage decrease in swelling is 34.7, 52.75, 43.55, and 36.9, respectively. Moreover, the CBR value increases with the increase in aspect ratio by keeping the diameter constant and decreases with the increase in aspect ratio by keeping the length constant. It was also observed that increasing the length and diameter of NSF further increased the CBR value of reinforced soil. This increment was substantial at a fiber content of 1.5% for an aspect ratio of 50 (length = 20 mm, diameter = 0.4 mm). There was also a decrease in the CBR swelling value with an increase in fiber content. Finally, this investigation concluded that the use of NSF is a solution to weak soils with regard to moisture and performance problems.

Intertwined synergistic abiotic and biotic degradation of polypropylene pellets in marine mesocosms

The accumulation of plastic waste in the oceans has caused growing concern for its effects on marine life. The interactions of plastics with environmental factors have been linked to fragmentation to micro- and nanoparticles with different properties and consequences, but the mechanism of fragmentation has not been fully understood yet. In this work, we investigate the combined effect of marine communities and ultraviolet (UV) radiation towards the degradation of virgin and artificially weathered polypropylene (PP) pellets after a long-term incubation period in marine mesocosms. The surface chemical alterations and deterioration of the polymer, in conjunction with the attachment and evolution of marine bacterial communities, the development of biofilm and exopolymeric substances (EPS), as well as the colloidal properties (zeta-potential and hydrodynamic diameter) of the mesocosms were studied. The surface area of both types of pellets decreased over time, despite no concrete weight change being observed. Cell growth, EPS production and colloid particle size were correlated to the loss of area. Therefore, we propose that surface area could be effectively monitored, instead of weight loss, as an alternative indicator of polymer degradation in biodegradation experiments. Changes in the chemical structure of the polymer, in addition to the evolution of the biological factors, implied that a complex degradation process alternated between two phases: an abiotic phase, when UV irradiation contributes to the deterioration of the polymer surface layers and a biotic phase, when marine communities degrade the weathered polymer surface to reveal the underlying layer of virgin polymer. Finally, microscopic particles, produced as a result of the decrease in pellet area, promoted the aggregation of colloidal particles. The role and impacts of these colloidal particles in marine ecosystems are yet as unidentified as that of micro- and nano-sized plastic particles and call for further investigation.

Effects of natural weathering on aged wood from historic wooden building: diagnosis of the oxidative degradation

Historic wooden buildings located outdoors are exposed to natural weathering conditions for extended periods of time, causing deterioration of wood properties by sunlight, oxygen, and other environmental factors. Current diagnostic procedures are limited to macroscopic inspection. In this interdisciplinary study, several aged samples from Yingxian Wooden Pagoda (ca. 1056 AD) were analyzed. Their micro-morphology and changes in chemical composition were investigated using less invasive multi-chemical techniques. The aim is to elucidate the oxidative degradation and its deterioration mechanism of the wood, which is essential in identifying the key factors responsible for natural weathering and devising strategies to counteract the surface deterioration. All aged wood samples had varying degrees of decay and lignin content was decreased in most of them. The high ratio of oxygen/carbon elements evidenced the occurrence of chemical reactions. In particular, the increasing ratio of oxygenated carbon/unoxygenated carbon indicates potential oxidation reactions. Overall, for the aged wood of historic wood building under warm-dry natural conditions, their deterioration occurred through the oxidative degradation of lignin. These unique results are useful in developing effective repair and restoration measures to conserve wooden components in historic buildings.

High-speed milling of hardened steel under minimal quantity lubrication with liquid nitrogen

Minimal quantity lubrication (MQL) can effectively reduce tool wear and improve surface quality in the high-speed milling of hardened steel, but MQL still suffers from poor cooling effect and oil-film failure at high cutting temperature. Compared with MQL, the cryogenic liquid nitrogen (LN2) or LN2 + MQL method with a highly strong cooling ability can further improve the processing conditions of the high-speed milling of hardened steel. However, the knowledge about the characteristics and mechanisms of the high-speed milling of hardened steel under the cryogenic LN2 and LN2 + MQL cooling is scarce. Thus, high-speed milling of hardened steel under cryogenic LN2 and LN2 + MQL cooling was studied in this paper. The machining characteristics were analyzed, and the machining mechanisms of cooling lubrication, tool wear, and surface deterioration layer formation were discussed. The experimental results show that the tool life of LN2 + MQL is remarkably longer than that of MQL, and high surface quality can be maintained at a long cutting distance. In the high-speed milling of hardened steel under the LN2 and LN2 + MQL modes, adhesion has little effect on tool wear, abrasion and chipping/flaking are the main tool wear mechanisms, and chipping/flaking is the main mechanism of tool breakage. MQL reduces the cutting interface friction using oil-film boundary lubrication, LN2 quickly removes the cutting interface heat using a strong cooling and heat transferability, and LN2 + MQL combines the advantages of both cooling and lubrication. Compared with MQL, the surface hardness of the plastic deformation layer of the LN2 and LN2 + MQL modes is considerably increased, whereas the thickness is smaller, and the strong low-temperature cooling is the main reason for this difference. The increase in tool wear will promote the cutting temperature and material slip deformation, increase the depth of high stress and strain zone and eventually increase the thickness of the plastic deformation surface layer in the LN2 and LN2 + MQL modes. In the two modes of LN2 and LN2 + MQL, there are no oxidation, nitridation, secondary quench hardening, and phase transformation in the surface layer. Severe dislocation strengthening caused by severe plastic deformation of the surface layer is the main hardening mechanism of the workpiece surface layer.

Probability-based surface deterioration assessment of bridge pylon and state updating using inspected crack length distribution

This study presents a probability-based surface deterioration evaluation framework to evaluate the cracking damage of bridge pylons subjected to repetitive thermal stresses caused by daily temperature variations. First, a temperature prediction model for massive concrete bridge members was utilized, incorporating the effects of convection and radiation. Subsequently, the thermal loads applied to the bridge pylon were computed using the finite element (FE) method. A modified linear elastic fracture mechanics (LEFM) crack model combined with random field theory for predicting crack propagation in concrete was employed. A probability-based surface damage grade method for a bridge pylon was proposed. Moreover, the deterioration state evaluation was updated by incorporating Bayesian inference, which involved using in situ inspection results (i.e. spatial distribution associated with surface crack lengths). The methodology was implemented using an illustrative example that considers a bridge pylon. The results provide useful information for aiding decision-making strategies concerning the maintenance and repair of massive concrete bridge components.

Influence of Surface Roughness, Nanostructure, and Wetting on Bacterial Adhesion.

Bacterial fouling is a persistent problem causing the deterioration and failure of functional surfaces for industrial equipment/components; numerous human, animal, and plant infections/diseases; and energy waste due to the inefficiencies at internal and external geometries of transport systems. This work gains new insights into the effect of surface roughness on bacterial fouling by systematically studying bacterial adhesion on model hydrophobic (methyl-terminated) surfaces with roughness scales spanning from ∼2 nm to ∼390 nm. Additionally, a surface energy integration framework is developed to elucidate the role of surface roughness on the energetics of bacteria and substrate interactions. For a given bacteria type and surface chemistry; the extent of bacterial fouling was found to demonstrate up to a 75-fold variation with surface roughness. For the cases showing hydrophobic wetting behavior, both increased effective surface area with increasing roughness and decreased activation energy with increased surface roughness was concluded to enhance the extent of bacterial adhesion. For the cases of superhydrophobic surfaces, the combination of factors including (i) the surpassing of Laplace pressure force of interstitial air over bacterial adhesive force, (ii) the reduced effective substrate area for bacteria wall due to air gaps to have direct/solid contact, and (iii) the reduction of attractive van der Waals force that holds adhering bacteria on the substrate were summarized to weaken the bacterial adhesion. Overall, this study is significant in the context of designing antifouling coatings and systems as well as explaining variations in bacterial contamination and biofilm formation processes on functional surfaces.

Modelling and analysis of the micro-milling of micro-dimpled structures with copying method on glow discharge polymer (GDP)

The surface with micro-dimpled structures on the target ball is helpful for improving nuclear fusion efficiency in inertial confinement fusion. Micro ball-end milling with copying method can provide a simple and effective option in machining micro dimples with high surface finish and geometry (dimension and shape) accuracy. In this paper, based on the established geometric error model, the influence of geometric errors and structural parameters of the machine tool on the dimple dimension and shape was first studied. Next, a model expressing the trajectory of cutting edge for simulating dimple geometry generated by ball-end milling was built. The model was used to analyze the effect of the spindle attitude, tool run-out and deflection deformation on the dimple dimension and shape. Micro ball-end milling tests were carried out, and the dimension, shape and cross-section profile of simulated and milled dimples were compared. A good correspondence between the simulated and milled dimple was observed, the largest error is 6.87%. Finally, from surface morphologies and surface roughness of the milled dimples, it was found that spindle attitude, axial feed rate are the main factors affecting the surface quality of micro dimple machined using micro ball-end milling with copying method. In particular, the axial feed rate need being optimized, reducing the effect of cutting edge quality and avoiding the deterioration of dimple surface and contour caused by a high feed rate. This research is of great significance for fabricating micro-dimpled functional surfaces by surface texturing based on milling methods.

Weighted Average Bridge Inspection Methodology (WABIM)

This article discusses developing a methodology based on visual inspection for quantifying bridge damage (WABIM). The proposed methodology was developed through the application of weighted averages and a case study. Many current visual inspection methodologies, manuals, or guides related to bridges only allow qualitative results to be determined. Consequently, a high degree of inefficiency and inaccuracy was identified in the results from traditional methodologies; since they have a subjective approach, the results merely depend on the observer. Therefore, a methodological proposal was generated that allowed qualitative results to be described quantitatively, increasing the objectivity of the analysis and the accuracy of bridge maintenance plans. Rating ranges are used with weighted averages for each pathology, applied directly to the structural elements of the bridges. The classification guidelines and pathologies of bridge structures are adapted according to the Manual for the Visual Inspection of Bridges and Pontoons of Invías, Colombia. The case study was developed on a bridge in the city of Pereira, Colombia, presenting more significant surface deterioration and equipment deterioration. The WABIM methodology identified that periodic maintenance is required and the intervention's emphasis.

Towards Embedded Electrochemical Sensors for On-Site Nitrite Detection by Gold Nanoparticles Modified Screen Printed Carbon Electrodes.

The transition of electrochemical sensors from lab-based measurements to real-time analysis requires special attention to different aspects in addition to the classical development of new sensing materials. Several critical challenges need to be addressed including a reproducible fabrication procedure, stability, lifetime, and development of cost-effective sensor electronics. In this paper, we address these aspects exemplarily for a nitrite sensor. An electrochemical sensor has been developed using one-step electrodeposited (Ed) gold nanoparticles (EdAu) for the detection of nitrite in water, which shows a low limit of detection of 0.38 µM and excellent analytical capabilities in groundwater. Experimental investigations with 10 realized sensors show a very high reproducibility enabling mass production. A comprehensive investigation of the sensor drift by calendar and cyclic aging was carried out for 160 cycles to assess the stability of the electrodes. Electrochemical impedance spectroscopy (EIS) shows significant changes with increasing aging inferring the deterioration of the electrode surface. To enable on-site measurements outside the laboratory, a compact and cost-effective wireless potentiostat combining cyclic and square wave voltammetry, and EIS capabilities has been designed and validated. The implemented methodology in this study builds a basis for the development of further on-site distributed electrochemical sensor networks.

The Role of Fluid Overpressure on the Fracture Slip Mechanism Based on Laboratory Tests That Stimulating Reservoir-Induced Seismicity

A critically stressed fracture will slide in response to the increase in fluid pressure inside the fracture while impounding, which will trigger induced seismicity. The mechanism of fluid overpressure is regarded as a significant factor in the reaction of the fracture slip after water diffusing. This study uses a shearing test with a cylinder of granite, with 100 mm height and 50 mm diameter, under the condition of hydraulic-mechanic (HM) coupling to figure out how fluid overpressure alters the mechanical behavior of the critically stressed fracture. The cyclic water pressurization simulates periodical impounding in the water reservoir. Results show that several slip events happen when water pressure continues to rise higher than the stable state. The change of roughness also indicates the deterioration of the fracture surface while sliding. According to the results, we conclude that the difference between inlet pressure and outlet pressure leads to an overpressure of the fracture, promoting a series of slips and induced seismicity. Hydraulic energy is introduced to explain the relationship between the input and output energy, which is also strong evidence to illustrate that fluid overpressure is a crucial mechanism in reservoir-induced seismicity.

Effect of bacterial resistant zwitterionic derivative incorporation on the physical properties of resin-modified glass ionomer luting cement

Biofilms induce microbial-mediated surface roughening and deterioration of cement. In this study, zwitterionic derivatives (ZD) of sulfobetaine methacrylate (SBMA) and 2-methacryloyloxyethyl phosphorylcholine, were added in concentrations of 0, 1, and 3% to three different types of commercially available resin-modified glass ionomer cement (RMGIC) (RMC-I: RelyX Luting 2, RMC-II: Nexus RMGI, and RMC-III: GC FujiCEM 2). The unmodified RMGICs served as the control group for comparison. The resistance of Streptococcus mutans to ZD-modified RMGIC was evaluated with a monoculture biofilm assay. The following physical properties of the ZD-modified RMGIC were assessed: wettability, film thickness, flexural strength, elastic modulus, shear bond strength, and failure mode. The ZD-modified RMGIC significantly inhibited biofilm formation, with at least a 30% reduction compared to the control group. The addition of ZD improved the wettability of RMGIC; however, only 3% of the SBMA group was statistically different (P < 0.05). The film thickness increased in proportion to the increasing ZD concentrations; there was no statistical difference within the RMC-I (P > 0.05). The experimental groups' flexural strength, elastic modulus, and shear bond strength showed an insignificant decrease from the control group; there was no statistical difference within the RMC-I (P > 0.05). The mode of failure differed slightly in each group, but all groups showed dominance in the adhesive and mixed failure. Thus, the addition of 1 wt.% ZD in RMGIC favorably enhanced the resistance to Streptococcus mutans without any tangible loss in flexural and shear bond strength.

유기단열재 수축에 의한 틈새 발생이 공동주택 외벽의 결로 방지 및 단열 성능에 미치는 영향에 대한 해석 - 열유동(CFD) 해석 및 현장 실측 결과 비교를 중심으로 -

In recent years, due to the strengthening of insulation performance standards and increasing demand for low-energy buildings, the high performance of the insulation material installed in the building is demanded. Meanwhile, crevices due to shrinkage of insulation board may cause thermal bridges and cause a decrease in surface temperature and thermal performance. When the size of the crevices is large, it is difficult to predict only conduction because internal air flow occurs. The purpose of this study is to analyze the heat flow implemented by computational fluid dynamics based on the field measurement and to quantitatively analyze the effect on the crevices by analyzing the effect of the heat flow due to the crevice to lower the surface temperature inside the building wall and the resulting energy loss. After measuring the surface temperature and indoor/outdoor air temperature of the actual wall where condensation occurred in the indoor, the wall was disassembled to check the size of the crevice, and the results of the crevice length and temperature reduction were obtained. Based on this data, the thermal flow analysis is conducted by dividing two cases according to the presence or absence of a crevice connection.BRDue to the occurrence of a crevice of 12 to 15 mm, a surface deterioration of about 9 to 10°C occurred in the upper and lower parts of the wall, and the performance standard of the wall was not met. In addition, as a result of the analysis of the wall, the heat transmission coefficient increased by 1.67 times compared to the existing wall due to the occurrence of crevices.