• Title/Summary/Keyword: concrete deterioration

Search Result 951, Processing Time 0.026 seconds

Early Frost Damage and Diagnose of Damage Depth Due to Early Frost Damage of the Concrete According to the Thickness of Members (부재 두께 변화에 따른 콘크리트의 초기동해 특성 분석 및 깊이진단)

  • Kim, Tae-Woo;Han, Min-Cheol
    • Journal of the Korea Institute of Building Construction
    • /
    • v.19 no.2
    • /
    • pp.131-138
    • /
    • 2019
  • Recently, there are many structures exposed to severe outdoor environments, which results in rapid degradation of durability of the concrete structures. there can be rapid deterioration of the concrete structures from early frost damage due to the insufficient curing in low outdoor temperature condition. The objective of this study is to investigate the effect of thickness change conditions and binding material on early frost damage depth of the concrete exposed to cold weather in winter, and is to clearly assess damage depth of the concrete structure due to early frost damage. Specimens with 300x300x(150, 200, 250, 300mm) were prepared. OPC and OPC+FA+BS were adopted for binders. Test results indicate that the depth of the early frost damage was deeper with the decrease of thickness of members. The brightness of specimens were reduced when the member thickness was thinner. When determining the depth of early frost damage, it can be distinguished into dark color and relatively bright color when dried for approximately 30 minutes in the indoors of $20^{\circ}C$ in temperature and 60% in relative humidity after submerging in water for 24 hours. The dark colored part can be determined easily when measured with vernier calipers.

Evaluating Chloride Absorption of Reinforced Concrete Structures with Crack Widths (균열 폭에 따른 콘크리트 구조물에서의 염화물 흡수 평가)

  • Kim, Kun-Soo;Park, Ki-Tae;Kim, Jaehwan
    • Journal of the Korea institute for structural maintenance and inspection
    • /
    • v.24 no.6
    • /
    • pp.10-16
    • /
    • 2020
  • Deterioration of reinforced concrete structure caused by chloride ingress is the main issue and regrading this, many studies have been investigated with both experiments and computational modelling. In addition to chloride diffusion, chloride sorption should be considered as a chloride transport mechanism in concrete structure and cracks formed in concrete structures are the main variable to evaluate the performance of the structures. In this study, after making two types of cracks width (0.1 and 0.3 mm) in reinforced concretes, chloride absorption tests were performed. Weight change and colour change using 0.1 AgNO3 solution from the samples were performed to measure chloride ingress. Image processing was also carried out to quantify range of colour change in carck face. From the result, it were confirmed that the amount of chloride absorption increases with exposure time and increasing crack width, and chlorides reached at steel depth within 1 hour. It would be possible that chloride can move through interface bewteen steel and concrete, thereby further study regarding this is required.

Cause Analysis for Sleeper Damage of Sleeper Floating Track in Urban Transit (도시철도 침목플로팅궤도의 침목손상 원인 분석)

  • Choi, Jung-Youl;Shin, Hwang-Sung
    • The Journal of the Convergence on Culture Technology
    • /
    • v.8 no.6
    • /
    • pp.667-674
    • /
    • 2022
  • In this study, the correlation between the damage type and operating conditions of the sleepers was analyzed based on the design data and visual inspection results for the concrete sleepers of the sleeper floating track (STEDEF) that have been in operation for more than 20 years. It appeared in the form of cracks, breakages, and breaks in the concrete at the center and tie bar contact and buried areas. As a result of the numerical analysis, it was analyzed that the change in the left and right spring stiffness of the sleeper resilience pad increases the maximum stress, tensile stress, compressive stress, and displacement of the concrete sleeper, and stress concentration in the concrete at the tie bar contact area. It was proved analytically that the sleeper resilience pad can affect the damage of the concrete sleeper. Therefore, damage of concrete sleepers in the sleeper floating track in urban transit could be caused by changes in spring stiffness of sleeper resilience pads. It was reviewed that preventive maintenance such as improvement and timely replacement of sleeper resilience pads was necessary.

Durability Evaluation and Defect Pattern Analysis in Railway Bridge Through Field Investigation (현장조사를 통한 철도 고가교 구조물의 내구성 평가 및 결함 패턴 분석)

  • Kwon, Seung Jun
    • Journal of the Korea institute for structural maintenance and inspection
    • /
    • v.17 no.1
    • /
    • pp.10-20
    • /
    • 2013
  • Because of the defect in design, damage in using period, and deterioration in long term exposure to severe environmental condition, degradation of performance in RC (Reinforced Concrete) structures has occurred. This paper contains durability performance evaluation in railway bridges which covers eight districts through field investigation. For the target structures, durability performance is evaluated and the critical problems in use are derived. Additionally, service lifes for the deteriorated structures are evaluated through Durability-Environment index method based on the results from field investigation, and the results are compared with those from the condition assuming the structures without defect, damage, and deterioration. The target structures which consist of RC T girder, PSC girder, RC box, and Rahmen are investigated and the critical damage patterns are derived. They are evaluated to be cracks in PSC girder end, flexural cracks in PSC girder, crack around EPT anchor, and flexural cracks in RC T girder and RC box. The reasons for the critical patterns are also investigated. This study can be utilized for the repair planning considering the different district and the structure types.

Wireless structural health monitoring of bridges: present and future

  • Hoult, Neil A.;Fidler, Paul R.A.;Hill, Peter G.;Middleton, Campbell R.
    • Smart Structures and Systems
    • /
    • v.6 no.3
    • /
    • pp.277-290
    • /
    • 2010
  • Internationally the load carrying capacity of bridges is decreasing due to material deterioration while at the same time increasing live loads mean that they are often exposed to stresses for which they were not designed. However there are limited resources available to ensure that these bridges are fit for purpose, meaning that new approaches to bridge maintenance are required that optimize both their service lives as well as maintenance costs. Wireless sensor networks (WSNs) provide a tool that could support such an optimized maintenance program. In many situations WSNs have advantages over conventional wired monitoring systems in terms of installation time and cost. In order to evaluate the potential of these systems two WSNs were installed starting in July 2007 on the Humber Bridge and on a nearby approach bridge. As part of a corrosion prevention strategy, a relative humidity and temperature monitoring system was installed in the north anchorage chambers of the main suspension bridge where the main cables of the bridge are anchored into the foundation. This system allows the Bridgemaster to check whether the maximum relative humidity threshold, above which corrosion of the steel wires might occur, is not crossed. A second WSN which monitors aspects of deterioration on a reinforced concrete bridge located on the approach to the main suspension bridge was also installed. Though both systems have provided useful data to the owners, there are still challenges that must be overcome in terms of monitoring corrosion of steel, measuring live loading and data management before WSNs can become an effective tool for bridge managers.

The Maintenance and Management Method of Deteriorated Facilities Using 4D map Based on UAV and 3D Point Cloud (3D Point Cloud 기반 4D map 생성을 통한 노후화 시설물 유지 관리 방안)

  • Kim, Yong-Gu;Kwon, Jong-Wook
    • Journal of the Korea Institute of Building Construction
    • /
    • v.19 no.3
    • /
    • pp.239-246
    • /
    • 2019
  • According to the survey on the status of aged buildings in Korea, A number of concrete buildings deterioration such as houses and apartment buildings has been increased rapidly. To solve this problem, the research related to the facility management, that is one of the importance factor, for monitoring buildings has been increased. The research is divided into Survey-based and Technique-based. However, the problem is that Survey-based research is required a lot of time, money and manpower for management. Also, safety cannot be guaranteed in the case of high-rise buildings. Technique-based research has limitations to applying to the current facility maintenance system, as detailed information of deteriorated facilities is difficult to grasp and errors in accuracy are feared. Therefore, this paper contribute to improve the environment of facility management by 4D maps using UAV, camera and Pix4D mapper program to make 3D model. In addition, it is expected to suggest that residents will be offered easy verification to their buildings deterioration.

Evaluation of Bond Strength in FRP Hybrid Bar Affected by Freezing/thawing Test and UV Rays (동결융해 및 UV 폭로시험을 거친 FRP Hybrid Bar의 인발거동특성 평가)

  • Park, Jae-Sung;Yoon, Yong-Sik;Park, Ki-Tae;Kwon, Sung-Jun
    • Journal of the Korean Recycled Construction Resources Institute
    • /
    • v.5 no.1
    • /
    • pp.53-58
    • /
    • 2017
  • FRP Hybrid Bar, composed of an embedded steel and the coated composites with epoxy and glass fiber, is an effective construction material with tension-hardening performance and lightweight. The epoxy exposed to UV(Ultra Violet Rays) and FT(Freezing and Thawing) action easily shows a surface deterioration, which can cause degradation of bonding strength between inside-steel and outside-concrete. In the present work, surface inspection for 3 different samples of normal steel, FRP Hybrid Bar before UV, and FRP Hybrid Bar after UV test was performed, then concrete samples with 3 reinforcement types were prepared for accelerated FT test. Through visual inspection on 3 typed reinforcement, no significant deterioration like chalking was evaluated. The results from FT test to 120 and 180 cycles showed FRP Hybrid Bar exposed to UV test has higher bonding strength than normal steel by 106.3% due to enlarged bond area by silica coating. The 3 cases showed a similar bond strength tendency with increasing FT cycles, however a relatively big deviations of bond strength were evaluated in FRP Hybrid Bar after UV test due to loss of silica coating.

A Study on Behavior of Post-integrated Abutment Bridge When Abutment and Bridge Decks are Jammed (교대 협착 발생 시 무조인트화 교량의 거동 분석 연구)

  • Park, Yang Heum;Nam, Moon S.;Jang, Il Young
    • Journal of the Korean GEO-environmental Society
    • /
    • v.22 no.3
    • /
    • pp.31-35
    • /
    • 2021
  • The expansion joints installed on the bridge for the accommodation of expansion and contraction of the supper structure are essential members of the bridge. However, the expansion joints are deteriorated over time and the waterproof function weakens, causing rainwater to penetrate and deteriorate the structure. In order to solve the traffic congestion caused by frequent replacement of the old expansion joints along with the deterioration of the structure, a post-integrated abutment bridge in which the existing expansion joints are removed and replaced with reinforced concrete link connection has been applied to highway bridges since 2016. After the post-integrated abutment method was applied, it was partially applied to bridges in which the superstructure and abutment were jammed. In this study, the causes of problems that may occur when the post-integrated abutment method is applied to the jammed bridge were analyzed numerically. It was analyzed that damage occurred in the link connection part. Based on the results of this study, the application condition for the post-integrated abutment method is reinforced as it is not possible to apply the post-integrated abutment method to bridges are already jammed.

Evaluation of Chemical Resistance Performance of Synthetic Rubber and Cement Based Injection Repair Materials Used in Underground Concrete Structures (지하 콘크리트 구조물에 적용되는 합성고무계 및 시멘트계 주입형 보수재료의 화학 저항성능평가)

  • Kim, Soo-Yeon;Lee, Yeon-Sil;Song, Je-Young;Kim, Byoungil;Oh, Sang-Keun
    • Journal of the Korea institute for structural maintenance and inspection
    • /
    • v.21 no.5
    • /
    • pp.148-155
    • /
    • 2017
  • In this study, by using the international standards ISO TS 16774, Part 2 Test method for chemical resistance as a quality control method of injection type repair material used for leakage crack of underground concrete structure, the performance requirement against of chemical environment of underground concrete structures for repair materials was tested. For this testing 3 types for each of the 2 classes of repair materials(synthetic rubber, cement), with a total of 9 types repair materials, were selected and examined. As a result, the test results showed that the smallest performance deterioration by the change in the mass was with the synthetic rubber(RG) type as opposed to the cement type system, showing that the synthetic rubber type had the strongest relative resistance to chemical exposure. Furthermore, it is necessary to investigate the material with high resistance to chemical substances and to examine the material which can increase resistance to sodium hydroxide and sodium chloride in cement system. These results can be used as a basic index for the selection of repair materials with the strongest resistance to chemical environment found in concrete structures. In addition, it is expected that the test results derived in this study can be used as reference data that can be reflected in the quality improvement of the maintenance material to be developed later.

Evaluation of Application of High Quality Recycled Fine Aggregate Manufacturing System by the Drying Specific Gravity Separation Method (건식비중분리법에 의한 고품질 재생잔골재 제조생산 시스템의 적용성 평가)

  • Kim Moo-Han;Kim Jae-Hwan;Kim Yong-Ro;Na Chul-Sung
    • Journal of the Korea Concrete Institute
    • /
    • v.17 no.1 s.85
    • /
    • pp.69-76
    • /
    • 2005
  • In this study, the high qualify recycled fine aggregate manufacturing system by the drying specific gravity separation method was evaluated. For the evaluation of the performance of the recycled aggregate, the engineering properties and durability of recycled aggregate has been tested. From the test results, the quality of recycled fing aggregates was improved by high quality recycled fine aggregate manufacturing system and satisfied with the quality standards of KS and JASS 5. Also, compressive and tensile strengths of recycled concrete show no critical difference caused by recycled fine aggregate replacement ratio. However, durability such as carbonation depth chloride ion penetration depth and drying shrinkage shows more deterioration than the concrete without recycled fine aggregate