• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.5
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• pp.114-126
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• 2021

This paper compared bridge maintenance in United Stated, United Kingdom, Japan, and Korea. Bridges play an essential role in transportation network and in the economic production process. To provide a desirable level of service to the public within limited budgets, it is required to provide effective bridge maintenance activities (e.g. inspection and repair/rehabilitation) at acceptable level of bridge service. A number of bridges are expected to age rapidly in Korea, which will be the excess burden of government. Since several countries have experienced a number of deteriorated bridges because of aging, the countries aforementioned in this study have already developed comprehensive bridge maintenance programs such as inspection practice and repair/rehabilitation techniques. Therefore, the goal of this paper is to synthesize and to compare useful knowledge on bridge maintenance and bridge crack repair/restoration of deteriorated concrete bridge in the four countries. Finally, recommendations that will serve as guidance to transportation agencies for potential enhancements to bridge maintenance and bridge repairs are presented.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.7
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• pp.113-119
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• 2019

Concrete structures built on reclaimed land are combined with chemical erosion such as chlorine and sulfate ions from seawater. Chloride attack deteriorates the performance of the structure by corroding reinforcing bars. In addition, the waste water treatment structure has a problem that the concrete is deteriorated by the sulfate generated inside. Therefore, in this study, the characteristics and chemical resistance of low heat cement concrete used in wastewater treatment structures constructed on reclaimed land were evaluated. As a result of the experiment, the target slump and air content were satisfied under all the mixing conditions. The slump of low heat cement (LHC) concrete was higher than that of ordinary portland cement (OPC) concrete, while the air content of LHC concrete was smaller than that of OPC concrete with the same mix proportion. As a result of compressive strength test, OPC concrete showed higher strength at younger age compared to 28 days. In contrast, LHC concrete exhibited higher strength than OPC concrete at the age of 56 days. As a result of chlorine ion penetration tests, LHC-B concrete showed chlorine ion penetration resistance performance of the "very low" level at the age of 56 days. As a result of chemical resistance evaluation, when the LHC concrete is applied without epoxy treatment, chemical resistance is improved by about 18% compared to OPC concrete. In testing chemical resistance, the epoxy coated concrete exhibited less than 5% strength reduction when compared to sound concrete.

• Journal of the Korea Concrete Institute
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• v.18 no.1 s.91
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• pp.125-132
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• 2006

Recently, surface finishing and protection materials were developed to restore performance of the deteriorated concrete and inhibiting corrosion of the reinforcing-bar. For this purpose, surface protection agent as well as coatings are used. Coatings have the advantage of low Permeability of $CO_2,\;SO_2$ and water. However, for coatings such as epoxy, urethane and acryl, long-term adhesive strength is reduced and the formed membrane of those is blistered by various causes. Also when organic coatings are applied to the wet surface of concrete, those have a problem with adhesion. On the other hand, surface protection agent penetrates into pore structure in concrete through capillary and cm make a dense micro structure in concrete as a result of filling effect. Furthermore, the chemical reaction between silicate from surface protection agent and cement hydrates can also make a additional hydration product which is ideally compatible with concrete body. The aim of this study is to examine the effect of penetrative surface protection agent(SPA) by evaluating several concrete durability characteristics. The results show that the concrete penetrated surface protection agent exhibited higher durability characteristics for instance, carbonation velocity coefficient, resistance to chemical attack and chloride ion penetration than the plain concrete. These results due to formation of a discontinuous macro-pore system which inhibits deterioration factors of concrete by changed the pore structure(porosity and pore size distributions) of the concrete penetrated surface protection agent.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.6
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• pp.102-112
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• 2012

Recently, the near surface mounted (NSM) FRP strengthening technique has been actively applied to deteriorated concrete structures for rehabilitation purposes. However, the use of this conventional NSM technique could be restricted due to the insufficient height or strength of the concrete cover. In this study, the stirrup-Cutting Near Surface Mounted(CNSM) technique was considered as an alternative, whereby NSM strips are placed at a deeper level, namely at the level of the main steel reinforcement. A flexural test of a concrete beam strengthened with CNSM technique was performed and the results were then compared to those for a concrete beam strengthened by the conventional NSM technique. The embedment length of the CFRP strips was varied in order to increase the effect of the anchoring depth of the NSM and CNSM CFRP strips in the beam specimens. From the results of the test, the beam with the CNSM CFRP strip showed typical structural behavior similar to that of the beam with the NSM CFRP strip. Moreover, there was no apparent structural degradation resulting from the stirrup partial-cutting. Consequently, the CNSM strengthening technique can be suitably utilized for extensively damaged concrete structures where it is difficult to apply the conventional NSM technique.

• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.4
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• pp.301-306
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• 2015

For the purpose of developing high performance marine concrete with improved crack resistance and durability, this analytical study aimed to estimate strength, hydration heat characteristics, and chloride attack resistance of concrete with mineral admixture. Ground granulated furnace slag and fly ash were considered for mineral admixture. The replacement of ground granulated furnace slag and fly ash considered in the analysis was in the range of 0~70% and 0~40 %, respectively. The analysis results indicated that both ground granulated furnace slag and fly ash decreased compressive strength, and the effect of adding ground granulated furnace slag on mitigation of hydration heat was limited whereas fly ash had an noticeable influence on it. It was also found that the replacement with ground granulated furnace slag enhanced the chloride attack resistance but fly ash deteriorated the resistance. From the analytical studies, It could be expected that a ternary blended cement composition with proper amount of ground granulated furnace slag and fly ash might be effective to control crack resistance as well as chloride attack resistance of marine concrete.

• Journal of the Society of Disaster Information
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• v.13 no.4
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• pp.562-569
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• 2017

Reinforced concrete is used for bridges and large structures that are constructed with social overhead capital because they are economically and semi-permanently integrated with reinforcing bar and concrete. However, when the chloride ion in the concrete destroys the passive film of the reinforcing bar by the marine exposure environment and the snow remover used in the winter season, and the reinforcing bar is corroded by various chemical and physical actions, the durability is deteriorated in a short period, and the life span is shortened. In this study, a repair method to recover the durability of the initial structure by effectively removing chloride ion from the damage caused by salting of the above mentioned reinforced concrete was conducted.

• Journal of the Korea Institute of Building Construction
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• v.24 no.5
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• pp.529-540
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• 2024

This research aimed to refine the concrete floor finishing for enhancing its performance compared to the traditional way. The new method involved the removing the deteriorated mortar layer and reinforcing the surface to augment the durability and bond strength of the floor surface. This study performed the experience to evaluate the bond strength, drop depth, rebound hammer hardness, and the surface hardness of the surface by adopting traditional and refined method. The results showed the proposed method enhanced the performance on all the metrics. Based on the experiment, the bond strength increased about 2.79 times before installing the finishing material, and the strength also improved about 1.67 times and 1.44 times at the painted finishing and non-painted finishing, respectively. In addition, the drop depth decreased about 4.42 times when adopting the proposed method, which shows the enhanced resistance to declamination compared with applying the traditional way. Lastly, the surface hardness measured by scratch thickness significantly improved about 505% in this experiment. The finding of this study indicates that the proposed method can substantially enhance in bond strendth and durability of floor finishing, reduce the defects of the concrete-based floor, and extend the life of the products.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.4
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• pp.177-186
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• 2005

The latest concrete structure has showed that the deterioration of durability has been increased by the damage from salt, carbonization, freezing & thawing and the others. Therefore, the measures for the concrete which has deteriorated durability have been taken. Among them, it has been often used that surface treatment which cuts off the deterioration factors of durability by protecting the surface of concrete. However, troubles such as fracture and rupture in the repair layer have been reported as time goes by due to the difference between the organic repair material like epoxy and concrete properties. Researchers have been developing the repair material which can cut off the deterioration factors of durability such as $CO_2$ gas, chloride ion and water by making the formation of concrete elaborate through the reaction with calcium ion when the surface improving agent is coated on the concrete. The main ingredient of that is inorganic substance which is the same as the concrete property. This study was evaluated the surface improving agent for permeability, watertightness, air-permeability, chemical resistance and elution resistance. As a result, it has been reported that the surface improving agent improves watertightness and air-permeability by penetration more than 10mm within concrete. Therefore, it is concluded that the surface improving agent developed in this research prevents deterioration of concrete durability when it is coated on the concrete structure.

• Journal of the Korea Concrete Institute
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• v.15 no.4
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• pp.529-540
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• 2003

Recently, the researches on the durability design of concrete structures have been studied. As the examples, models to evaluate the service life prediction of the structure have been developed. The purpose of this article is to develop the model for predicting remaining service life. The final aim is to provide the user time for repairing the concrete structures. In addition, it makes possible to maintain the concrete structure economically. 70 reservoirs out of the inland concrete structures were selected and concrete structures of their components were surveyed. Two methods were used for measuring carbonation; TG/DTA method and Phenolphtalein indicator and, the value of pH was measured by the pH meter, After deriving correlations of calcium carbonate and used year, duration from completion year to 2002, pH value, and concrete cover depth the model was developed for predicting remaining service life by measuring data as small as possible. The conventional models had been developed on the basis of experiment data obtained from the restricted lab environment like as carbon gas exposure. On the other hand this model was developed on the basis of measuring data obtained from the real field that the complex deterioration actions are occurred such as freezing and thawing, carbonation, steel corrosion, and so on. The reliability of the developed model will be evaluated high in this point and this model can help to maintain concrete structures economically by providing the manager time to repair the deteriorated concrete structures in site of facility management.

• Magazine of the Korea Concrete Institute
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• v.10 no.4
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• pp.153-161
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• 1998

Concrete structures has been deteriorated by and freezing the thawing due to temperature gap. This study was conducted to evaluate durability of concrete which are increasingly demanded recently. Therefore the research of durability must be executed for application of waste foundry sand concrete real structures. Concrete durability properties incorporating waste foundry sand was performed with the variable of W/C ratio. Sand/Waste foundry sand ratio and Air entrainment-Non air entrainment. Cylinder specimens were made and subjected to freezing and thawing cycle at -18$^{\circ}C$ and 4$^{\circ}C$. Dynamic modulus of elasticity were evaluated as F/T cycle increase. The results show that strength of concrete is increased the W/C ratio decrease, the Sand/Waste foundry sand ratio increases when the concrete contains AE agent and decreasing W/C ratio and AE concrete makes improved resistance of freezing and thawing improved. Especially, resistance of freezing and thawing is improved by Fine aggregate/Waste foundry sand ratio which is 50%, 25%, 0% in a row. Therefore it is turn out the waste foundry sand could be applied to concrete from the experiment.