• Earthquakes and Structures
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• v.16 no.6
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• pp.727-741
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• 2019

A reinforced concrete water tank is a typical functional liquid storage structure and cracks are the greatest threat to the liquid storage structure. Tanks are readily cracked due to seismic activity, thereby leading to the leakage of the stored liquid and a loss of function. In order to study the effect of cracks on liquid storage tanks, self-healing and leakage tests for bending cracks and through cracks in the walls of a reinforced concrete water tank were conducted. Material performance tests were also performed. The self-healing performance of bending cracks in a lentic environment and through cracks in a lotic environment were tested, thereby the self-healing width of bending micro-cracks in the lentic environment in the short term were determined. The through cracks had the capacity for self-healing in the lotic environment was found. The leakage characteristics of the bending cracks and through cracks were tested with the actual water head on the crack. The effects on liquid leakage of the width of bending cracks, the depth of the compression zone, and the acting head were determined. The relationships between the leakage rate and time with the height of the water head were analyzed. Based on the tests, the relationships between the crack characteristics and self-healing as well as the leakage were obtained. Thereby the references for water tank structure design and grading earthquake damage were provided.

• Journal of Environmental Science International
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• v.19 no.6
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• pp.737-746
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• 2010

Restraint to drying shrinkage is the most common cause of concrete cracking. In many applications, drying shrinkage cracks are inevitable. In this paper, the surface cracks of soil concrete caused by drying shrinkage were considered to become an one of concrete textures. So, laboratory shrinkage tests were conducted and the results were applied to the field applications. The study results were summarized as follows; First, the use of vinyl sheets and concrete polymers helped to control the concrete cracking. Second, crack propagation usually started at the interfaces of soil concrete slabs and the cracks grew to the inner slabs. Third, surface cracks of soil concrete slabs could be an one of good concrete textures

• Advances in concrete construction
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• v.7 no.4
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• pp.219-229
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• 2019

This paper presents an experimental study on the structural performance of an innovative ultra-high performance fiber reinforced concrete (UHPFRC) deck with coarse aggregate of composite bridge under shear force. Test parameters included curing method and shear span-to-height ratio. Test results indicated that more short fine cracks developed beside the existing cracks due to the randomly dispersed fibers, resulting in re-distributing and homogenizing of the concrete stress beside cracks and allowing for the occurrence of more cracks with small spacing compared to normal strength concrete beams. Curing methods, incorporating steam curing and natural curing, did not have obvious effect on the nominal bending cracking strength and the ultimate strength of the test specimens. Shear reinforcement need not be provided for UHPFRC decks with a fiber volume fraction of 2%. UHPFRC decks showed superior load resistance ability after the appearance of cracks and excellent post-cracking deformability. Lastly, the current shear provisions were evaluated by the test results.

• Smart Structures and Systems
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• v.20 no.1
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• pp.75-83
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• 2017

Effectively monitoring the concrete cracks is an urgent question to be solved in the structural safety monitoring while cracks in hydraulic concrete structures are ubiquitous. In this paper, two experiments are designed based on the measuring principle of Pulse-Pre pump Brillouin Optical Time Domain Analysis (PPP-BOTDA) utilizing Brillouin optical fiber sensor to monitor concrete cracks. More specifically, "V" shaped optical fiber sensor is proposed to determine the position of the initial crack and the experiment illustrates that the concrete crack position can be located by the mutation position of optical fiber strain. Further, Brillouin distributed optical fiber sensor and preinstall cracks are set at different angles and loads until the optical fiber is fractured. Through the monitoring data, it can be concluded that the variation law of optical fiber strain can basically reflect the propagation trend of the cracks in hydraulic concrete structures.

• Proceedings of the KSR Conference
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• 2004.06a
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• pp.1205-1210
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• 2004

Cracks in the underground structures are mainly observed due to internal ununiformity of thermal stresses or restraint of structural movement in associate with rapid temperature gradient. Especially, thermal cracks are known to occur easily in a massive structure, but possibility of these depend on the amount of cement applied and ratio of span to height of the structure even though the thickness is less than specification‘s. Thus, this study aims at how to control thermal cracks in a massive subway structure and figures out an optimized construction method and procedure. As results of parametric study for length, height and outer temperature for concrete placement, it is found that hydration heats were not affected by both length and height of concrete placement but thermal stresses were greatly dependent. Most effective ways of controling thermal cracks were to fit a proper ratio of length to height of concrete placement and to decrease temperature of concrete placement as much as possible.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10b
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• pp.1151-1156
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• 2000

Temperature rise and restraint condition in mass concrete structures may induce the cracks at early ages. The method to prevent the cracks induced by heat of hydration has become the major concern in mass concrete structure. Therefore, the purpose of this study is to propose a method to control heat of hydration in mass concrete structures by using cryogenic liquefied nitrogen. The method in this study was applied to actual mass concrete structure to prevent the occurrence of thermal cracks at early ages. The surface observation of structure during more than one month shows that there are seldom cracks. This represent that the method in the study is effective in the control of heat of hydration.

• Journal of the Korea Concrete Institute
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• v.24 no.2
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• pp.103-109
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• 2012

Micro-cracks with a width less than 0.1 mm in precast concrete panels do not cause structural problem, but they can cause problems in long term durability and concrete surfaces aesthetic, requiring additional repair costs. In this paper, polymer cement concrete is used to increase flexural tensile strength and to prevent micro-cracks due to construction loads on LB-DECK panels. Using 5% polymer-cement ratio, the panel crack moment is increased by improving flexural tensile strength and controlling visible micro-cracks during construction stage of LB-DECK.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.05a
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• pp.105-106
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• 2018

Cracks are typical defects that occur in concrete structures. When cracks occur in the structure, durability reduction, concrete neutralization, and steel corrosion cause functional safety problems. In order to prevent such cracks, surface repair method is performed for cracks smaller than 0.3 mm and rechargeable method is performed for cracks larger than 0.3 mm. However, even if it is applied by the surface repair method at less than 0.3 mm, re-leakage cracks continue to occur. Recently, the Supreme Court ruled that the rechargeable method should be applied to cracks less than 0.3mm in order to reduce the occurrence of defects. However, it was considered that the repair fees were too high relative to the observed defect rate, resulting in a necessitation of modifying the existing construction analysis administration standards. This study analyzes the differences in the subjective views on the durability degradation with regards to surface repair methods in concrete structures.

• Journal of the Korea Institute of Building Construction
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• v.7 no.2 s.24
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• pp.99-106
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• 2007

The purpose of this study presents in Relations between cracks in self-leveling material and quality of floor groundwork surface are experimentally examined. As the first stage, the experiment to observe cracks in self-leveling material constructed on floor groundwork made from various kinds of concrete was carried. As a result, following basic findings were obtained. First, observation of cracks should be continued until an increase in width of cracks stop, without constructing any finishing material. Second, degree of cracks may be indicated quantitatively by the product of length and width. Finally, Cracks and separation is not be influenced by specimen size. Based on these findings, the method of predicting cracks by evaluating surface layer quality of floor groundwork will be established.

• Proceedings of the Korea Concrete Institute Conference
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• 1995.10a
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• pp.183-186
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• 1995

Most defects in the cement concrete pavement take place mainly on the joints. These corner cracks don't happen as often as others relatively. it happens continuously. In order to analyze the structural behavior of the corner cracks, The finite element structural analysis was performed on the representative section of the cement concrete pavements using JSLAB which uses FEM analysis method. On plain cement concrete pavements, The result shows that loading not only on the joints but also on the center of slab brings out the maximum stress on the corner of slab and it is expected to make the corner cracks.