• Title/Summary/Keyword: Concrete mat

Search Result 98, Processing Time 0.028 seconds

Field Application of the Mass Concrete Utilizing Combined Method for Temperature Crack Reduction (온도균열 저감공법을 복합사용한 매스콘크리트의 현장적용)

  • Han, Sang-Yoon;Lee, Chung-Sub;Baek, Dae-Hyun;Jang, Duk-Bae;Han, Min-Cheol;Han, Cheon-Goo
    • Proceedings of the Korean Institute of Building Construction Conference
    • /
    • 2010.05a
    • /
    • pp.37-39
    • /
    • 2010
  • In this study, with new office construction site of S Construction company as subject, to solve all the problems according to reduced hydration heat and temperature crack of mass concrete used mat foundation and placing time difference, low heat combination of coarse particle cement and fly-ash and setting time difference applied AE water reducing agent, and to prevent the early frost damage caused by low outdoor temperature, a heat insulation method using double bubble sheet was conducted. As a result, it was found that hydration heat and setting time difference was reduced by applying a low heat combination and setting time difference construction method, and that the high insulation capability of the double bubble sheet was able to not only prevent the early frost damage but also reduce temperature difference between the central part and the upper part of mass concrete.

  • PDF

Study on Hydration Heat and Contact the Mix-Design of Foundation Mass Concrete Using Hydration Temperature Analysis Program (수화열 해석프로그램을 이용한 기초 매스콘크리트의 사전 배합선정 및 수화열 검토)

  • Seol, Jun-Hwan;Jo, Man-Ki;Bang, Hong-Soon;Kim, Ok-Kyue
    • Proceedings of the Korean Institute of Building Construction Conference
    • /
    • 2019.05a
    • /
    • pp.105-106
    • /
    • 2019
  • In this research, considering the practical conditions at field, thermal cracking method was suggested based on the comparative analysis between predicted value and actual value obtained from the actual structure member with optimum mix design. The optimum mix design was deduced from the various mix designs with various proportions of cementitious binder for upper and lower placement lifts of mat-foundation mass concrete. Therefore, it can be stated that applying low heat mix design and different heating technique between upper and lower placement lifts for mass concrete are efficient to control the thermal cracking. As future issues, based on the interpretation result value, we will select the optimal combination that is applied specifically to the actual site, and deeply analyze the correlation between the measured value and the analysis value through the combination and the test of the actual structure.

  • PDF

Numerical simulation approach for structural capacity of corroded reinforced concrete bridge

  • Zhou, Xuhong;Tu, Xi;Chen, Airong;Wang, Yuqian
    • Advances in concrete construction
    • /
    • v.7 no.1
    • /
    • pp.11-22
    • /
    • 2019
  • A comprehensive assessing approach for durability of reinforced concrete structures dealing with the corrosion process of rebar subjected to the attack of aggressive agent from environment was proposed in this paper. Corrosion of rebar was suggested in the form of combination of global corrosion and pitting. Firstly, for the purposed of considering the influence of rebar's radius, a type of Plane Corrosion Model (PCM) based on uniform corrosion of rebar was introduced. By means of FE simulation approach, global corrosion process of rebar regarding PCM and LCM (Linear Corrosion Model) was regressed and compared according to the data from Laboratoire $Mat{\acute{e}}riaux$ et $Durabilit{\acute{e}}$ des Constructions (LMDC). Secondly, pitting factor model of rebar in general descend law with corrosion degree was introduced in terms of existing experimental data. Finally, with the comprehensive numerical simulation, the durability of an existing arch bridge was studied in depth in deterministic way, including diffusion process and sectional strength of typical cross section of arch, crossbeam and deck slab. Evolution of structural capacity considering life-cycle rehabilitation strategy indicated the degradation law of durability of reinforced arch bridges.

A Study on the Mix Design and the Control System of Thermal Crack for High Quality Mass Concrete (고품질 매스콘크리트 시공을 위한 배합설계 및 온도균열제어 시스템에 관한 연구)

  • Kim, Sun-Gu;Lee, Sang-Soo;Won, Cheol;Park, Sang-Joon;Kim, Dong-Seok
    • Journal of the Korea Institute of Building Construction
    • /
    • v.1 no.2
    • /
    • pp.174-178
    • /
    • 2001
  • This study was performed to control the thermal crack of the mat footing slab in the multi-purposed buildings. In this study, we executed the mixing design of concrete to satisfy the workability and the quality according to the site conditions. And, we evaluated quantitatively about the possibility of thermal crack by using hydration heat analysis system. Finally, we proposed the optimal mixing conditions, curing methods and curing period which all factors are considered. As a result, the optimal mixing conditions were : W/B 41%, unit binder 375kgf/$\textrm{m}^3$, FA replacement ratio 20%. Lowest thermal stress was 22.0kgf/$\textrm{cm}^2$ and at that time thermal crack index was over 1.5, when the coefficient of thermal conductivity was lowest among the curing conditions. And, the total curing time was estimated at 6.7 days according to curing steps.

  • PDF

BIM based Data Exchange System of Welded Wire/bar Mat for Pre-fab RC Members (BIM 기반 프리패브 부재의 용접철근매트 정보교환 시스템)

  • Jung, Jae-Hwan;Kim, Do-Hyeong;Kim, Hyun-Gi
    • Journal of KIBIM
    • /
    • v.11 no.1
    • /
    • pp.21-30
    • /
    • 2021
  • Reinforcing bars, a major component of the pre-fab structure, adheres to the existing on-site assembly method and attempts to develop and commercialize the technology of the pre-assembly method, but the effect is insignificant. Welded Wire / Bar Mat (WBM) has various advantages such as commercialization of rebar through machine manufacturing to improve workability, but it is different from the existing design and the construction method is different from the previous one. Therefore, to maximize the advantages of WBM and improve productivity, manufacturing, transportation, and construction from the design stage should be considered based on BIM from the initial design stage. In this paper, the concept of the design support system for the WBM was established based on the use of BIM in concrete reinforcement and the preliminary research on the WBM. WBM conversion design was performed for the existing prefabricated members, and based on this, the exchange format and system of the master prefabricated model with the WBM design data were set up. As a result of the pilot test, it was found that the traditional reinforcing bar information extracted from the master prefab model has transmitted 100% accurately. As for the WBM information, 100% of the information on the straight reinforcement was transmitted and represented, and the information on the bent reinforcement was found to have a 90% recall in the master BIM tool.

A Case Study on Field Construction of Cold Weather Mass Concreting Using Double Bubble Sheets and Hydration Heat Difference Method (이중 버블시트 및 수화발열량차 공법에 의한 한중매스콘크리트의 현장적용 연구)

  • Kim Jong;Yoon Jae-Ryung;Jeon Chung-Keun;Shin Dong-An;Oh Seon-Gyo;Han Cheon-Goo
    • Proceedings of the Korean Institute of Building Construction Conference
    • /
    • 2006.05a
    • /
    • pp.15-18
    • /
    • 2006
  • The test result of mat concrete applying both hydration heat difference and insulation curing method on new construction of Cheongju university educational building are summarized as following. Both fresh concrete and compressive strength properties were satisfied In aimed value. Setting time of concrete incorporating 15% of fly ash(FA) retarded 1.2 hour than control concrete. Temperature history of mali concrete indicated that the highest temperature of center was exhibited at $126^{\circ}C$ after 51 hours while the highest temperature of upper section was $10.6^{\circ}C$ after 46 hours. Temperature Difference between center and surface was managed at less than $6^{\circ}C$ during whole curing period. In addition the temperature of upper section secured more than $3.3^{\circ}C$ while the temperature of outside was indicated at less than $-10^{\circ}C$. Maturity by parts of construction secured more than $30^{\circ}C$ DD higher than outside at 3 days. The more number of times, applying insulation curing method by double bubble sheets, increased, the higher economic effect was secured. Overall it was clear that applying both double bubble sheets and hydration heat difference method on this new construction can resist hydration heat crack, early frost demage and strength decrease. It also significantly contributed quality improvement of cold weather concreting

  • PDF

The Effect of Heat Curing Methods on the Protection against Frost Damage at Early Age of the Concrete Under Extremely Cold Climate

  • Jung, Eun-Bong;Shin, Hyun-Sup;Han, Min-Cheol
    • Journal of the Korea Institute of Building Construction
    • /
    • v.13 no.6
    • /
    • pp.513-521
    • /
    • 2013
  • This study aimed to examine whether heat curing methods of concrete subjected to $-10^{\circ}C$ could be effective by varying the combination of heating cable and surface heat insulations. Three different concrete specimens incorporating 30% fly ash with 50% W/B were fabricated to simulate wall, column and slab members with dimensions of $1600{\times}800{\times}200$ mm for slab, $800{\times}600{\times}200$ mm for wall and $800{\times}800{\times}800$ mm for column. For heat curing combinations, Type-1 specimens applied PE film for slab, plywood for wall and column curing. Type-2 specimens applied double layer bubble sheet (2LB) and heating coil for slab, and 50 mm styrofoam for wall and column curing. Type-3 specimen applied 2LB for slab, electrical heating mat for wall and column inside heating enclosure. The test results revealed that the temperature of Type 1 specimen dropped below $0^{\circ}C$ beginning at 48 hours after placement due to its poor heat insulating capability. Type 2 and 3 specimens maintained a temperature of around $5{\sim}10^{\circ}C$ after placement due to favorable heat insulating and thermal resistance.

Performance Evaluation of Bridge Deck Materials based on Ordinary Portland Cement Concrete (보통 포틀랜드 콘크리트 기반 교면포장 재료 성능 평가)

  • Nam, Jeong-Hee;Jeon, Seong Il;Kwon, Soo Ahn
    • International Journal of Highway Engineering
    • /
    • v.19 no.6
    • /
    • pp.129-137
    • /
    • 2017
  • PURPOSES : The purpose of this study is to develop bridge deck concrete materials based on ordinary Portland cement concrete, and to evaluate the applicability of the developed materials through material properties tests. METHODS : For field implementation, raw material (cement, fine aggregate, and coarse aggregate) properties, fresh concrete properties (slump and air content), strength (compressive, flexural and bond strength) gain, and durability (freeze-thaw resistance, scaling resistance, and rapid chloride penetrating resistance) performance were evaluated in the laboratory. RESULTS : For the selected binder content of $410kg/m^3$, W/B = 0.42, and S/a = 0.48, the following material performance results were obtained. Considering the capacity of the deck finisher, a minimum slump of 150 mm was required. At least 6 % of air content was obtained to resist freeze-thaw damage. In terms of strength, 51.28 MPa of compressive strength, 7.41 MPa of flexural strength, and 2.56 MPa of bond strength at 28 days after construction were obtained. A total of 94.9 % of the relative dynamic modulus of elasticity after 300 cycles of freeze-thaw resistance testing and $0.0056kg/m^2$ of weight loss in a scaling resistance test were measured. However, in a chloride ion penetration resistance test, the result of 3,356 Coulomb, which exceeds the threshold value of the standard specification (1000 Coulomb at 56 days) was observed. CONCLUSIONS : Instead of using high-performance modified bridge deck materials such as latex or silica fume, we developed an optimum mix design based on ordinary Portland cement concrete. A test construction was carried out at ramp bridge B (bridge length = 111 m) in Gim Jai City. Immediately after the concrete was poured, the curing compound was applied, and then wet mat curing was applied for 28 days. Considering the fact that cracks did not occur during the monitoring period, the applicability of the developed material is considered to be high.

Mat Drying Characteristics of the Wet-thresheds Rough-rice and Effect of Drying Environment on the Cracks Formation (생탈곡(生脱糓)벼의 깔아말림 특성(特性)과 건조조건(乾燥條件)이 동할미(胴割米) 발생(發生)에 미치는 영향(影響))

  • Chun, Jae Kun;Choi, Boo Dol;Lee, Jeong Cheol
    • Journal of Biosystems Engineering
    • /
    • v.6 no.2
    • /
    • pp.58-64
    • /
    • 1982
  • The fresh threshed paddy-mat dryings on the various environments were analyzed on their drying characteristics and rice quality resulted. The moisture content of paddy was mainly determined by the accumulated solar energy received, and which was expressed as a simple equation. The drying characteristics revealed to follow a constant rate drying type, and as the depth increased the more typical constant-rate drying pattern was observed. The relationship between the drying rate and bed depth was established with a simple exponential equation. The raking operation during the drying period showed a favorable effect both on the drying rate and the reduction of crack formation. Drying environments such as straw mat, concrete, ground, polyethylene film did not affect significantly the drying rate and rice quality. Considering the drying rate and quality, the optimum bed depth of mat paddy drying was around 6 cm.

  • PDF

A Study on the Loss Reduction Method of Reinforcing Bar through Case Study

  • Park, U-Yeol;Jung, Hyeon-Ok;Kang, Tai-Kyung;Cho, Hun-Hee
    • Journal of the Korea Institute of Building Construction
    • /
    • v.10 no.4
    • /
    • pp.123-132
    • /
    • 2010
  • Rebar work accounts for approximately 30% of the total construction costs for rebars and concrete. Recently, the high rising prices of rebars have become one of the principle factors of rising construction costs. Therefore, construction companies are putting much effort into loss reduction of rebars. Consequently, in this study, we wished to present loss reduction methods of rebars before the preparation of the placing drawings. To devise such methods, we collected previous case studies and analyzed methods that were applied for loss reduction. As a result of the analysis, we were able to find the following methods for loss reduction of rebars: method of reducing the number of splices at the mat foundation, method of reducing splice length at the internal columns or walls of the underground parking lot, method of reducing cap-ties of internal beams of basement floors excluding perimeter beams, and method of reducing anchorage length at the internal column or wall of the underground parking lot. Based on those analysis results, we presented our own loss reduction methods of rebars. Applying our methods resulted in considerable loss reduction.