• Magazine of the Korean Society of Agricultural Engineers
• /
• v.45 no.1
• /
• pp.45-54
• /
• 2003

The effects of binder content and silica sand content on the durability characteristics of lightweight polymer concretes are examined. As a result, the flame lingering times using unsaturated polyester resin and non-combustible polyester resin were 60∼120 and 0∼4 seconds respectively, and the combustion lengths were 9∼11 mm and 0∼3 mm, respectively. Thus it is believed that the lightweight polymer concrete was incombustible and the light weight polymer concrete in which non-combustible material was added was perfectly non-combustible. The percent of original mass of lightweight polymer concrete, according to the freezing-thawing experiment, was below 0.3 %, which was much less than that of cement concrete. The pluse velocity, for the case of the binder content 28 %, showed the minimum decreasing rate for the lightweight polymer concrete with silica sand content of 50 %. The higher the binder content, the greater the durability. That is much higher than other material and believed that the freezing-thawing was suppressed by a low absorption.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1997.04a
• /
• pp.254-260
• /
• 1997

Chloride-induced corrosion of reinforcement is one of the main factors which cause the deterioration of concrete structures. Durability and service lives of the concrete sturctures should be predicted in order to minimize the risk of corrosion of reinforcement. The objective of this study is to suggest the basis of analytical methods of predicting the corrosion threhold time of concrete structures. Based on the chemistry and physics of chloride ion transport and corrosion process, chloride intrusion with various exposure conditions, variability of diffusivity and transport of pore water in concrete are taken into consideration in applying finite element formulation to the predicion of corrosion threhold time. The effects of main factors on the prediction of chloride intrusion and corrosion threhold time are examined. In addition, after chloride diffusivities of several mixture proportions with different parameters are measured by chloride diffusion test, the exemplary anayses of corrosion threhold time of those mixture proportions are carried out.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2004.11a
• /
• pp.221-224
• /
• 2004

Several factors of concrete durability decline factor are acted as complex deterioration and is happened not that happen by simplicity deterioration. Specially, in case of sea construction, as complex salt damage, carbonation and freezing & thawing, concrete surface and pore structure is deteriorated. Therefore, analyzing concrete carbonation and pore structure after freezing and thawing test by fresh water and sea water in this research, we wish to study about acceleration of decline of durability and complex deterioration by concrete surface deterioration in sea environment.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2004.11a
• /
• pp.257-260
• /
• 2004

The durability and water - resisting capability of nuclear concrete structures can be greatly improved as the density of concrete surface increases. Applying the surface penetration sealer to the concrete surface can increase the surface density. Therefore, the objective of this study is to identify the most suitable surface penetration sealer based on lab test. The considered parameters rate and water resistance and absorbance rate of the concrete specimen after the penetration sealer are applied. The experimental study resulted in the identification of the two most suitable surface penetration sealer based on their performance.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2006.11a
• /
• pp.601-604
• /
• 2006

Reinforcement corrosion is the most important durability problem of reinforced concrete structures. One of the important factors affecting the steel corrosion is carbonation. However, existing carbonation test takes several months to obtain the results. Therefore, in this study, new rapid carbonation test equipment for concrete was developed and its applicability was investigated. The testing period can be reduced by increasing $CO_2$ concentration up to 100% in the equipment. It is found from the test results that the carbonation depth of concrete specimens tested for 2 weeks was $3{\sim}5$ times greater than that of specimens tested by existing test method. In conclusion, it would be possible to get the reliable test results enough to evaluate the durability of concrete structures in a short-period.

• Journal of the Korean Society of Safety
• /
• v.26 no.4
• /
• pp.65-68
• /
• 2011

High strength concrete(HSC) has been mainly used in large SOC structures. HSC have superior property as well as improvement in durability compared with normal strength concrete. In spite of durability of HSC, explosive spalling in concrete front surface near the source of fire occurs serious problem in structural safety. It is reported that spalling is caused by the vapor pressure under fire and polypropylene(PP) fiber has an important role in protecting from spalling. The spalling properties of ultra high strength concrete specimens with various contents of PP fiber were investigated in this study. In results, the content of PP fiber for spalling protection increases over 0.2 vol.% as the concrete strength increases to 120 MPa.

• Computers and Concrete
• /
• v.23 no.2
• /
• pp.107-119
• /
• 2019

In-service reinforced concrete structures are simultaneously subjected to a combination of multi-deterioration environmental actions and mechanical loads. The combination of two or more deteriorative actions in environments can potentially accelerate the degradation and aging of concrete materials and structures. This paper reviews the coupling and synergistic mechanisms among various deteriorative driving forces (e.g. chloride salts- and carbonation-induced reinforcement corrosion, cyclic freeze-thaw action, alkali-silica reaction, and sulfate attack). In addition, the effects of mechanical loads on detrimental environmental factors are discussed, focusing on the transport properties and damage evolution in concrete. Recommendations for advancing current testing methods and predictive modeling on assessing the long-term durability of concrete with consideration of the coupling effects are provided.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2019.11a
• /
• pp.60-61
• /
• 2019

Concrete carbonation is one of the factors that reduce the durability of concrete. In modern times, due to industrialization, the carbon dioxide concentration in the atmosphere is increasing, and the impact of carbonation is increasing. So, it is important to understand the carbonation resistance according to the concrete compounding to secure the concrete durability life. In this study, we want to predict the concrete carbonation velocity coefficient, which is an indicator of the carbonation resistance of concrete, through the deep learning algorithm, and to find the activation function suitable for the prediction of carbonation rate coefficient as a process to determine the learning accuracy through the deep learning algorithm. In the scope of this study, using the ReLU function showed better accuracy than using other activation functions.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.04a
• /
• pp.589-592
• /
• 2008

This study was conducted to assess the durability of Chloride-inhibiting Low-Heat Cement while being subjected to freezing-thawing during winter seasons. Although durability varies slightly depending on the conditions of the jobsite, frost damage to concrete resulting from repeated freezing and thawing over the course of seasonal changes is the leading cause behind lowered concrete durability. in addition, concrete that has been subjected to freezing and thawing during the winter season develops a significant amount of expansive force at the core and begins to exhibit signs of damage, such as cracking, peeling, and detachment from the aggregate. Therefore, this study fabricated test specimens using a Chloride-inhibiting Low-Heat Cement(CLC) and the widely used blast furnace slag cement(BFS) and Ordinary Portland Cement(OPC) with water-to-cement ratios of 35%, 40% and 45%, respectively, to assess the durability index of the CLC as per resistance to freezing-thawing. The specimens were then tested using the KS F 2456 method (Testing method for resistance of concrete to rapid freezing and thawing) to measure the dynamic modulus of elasticity. The dynamic modulus of elasticity measurements were then used to derive the durability indices. By comparing the durability indices, it was confirmed that CLC, BFS, and OPC all had superior durability.

• Advances in concrete construction
• /
• v.9 no.1
• /
• pp.9-22
• /
• 2020

The present work looks at the possibilities of recycling more than once demolished concrete as coarse aggregates, to produce new concrete. Different concrete mixes were made with substitutions of 50%, 75% and 100% of recycled concrete aggregates respectively as coarse aggregates. The physico-mechanical characterization tests carried out on the recycled concrete aggregates revealed that they are suitable for use in obtaining a structural concrete. The resulting concrete materials had rheological parameters, compressive strengths and tensile strengths very slightly lower than those of the original concrete even when 100% of two cycles recycled concrete aggregates were used. The durability of the recycled aggregates concrete was assessed through water permeability, water absorption and chemical attacks. The obtained concretes were thought fit for use as structural materials. A linear regression was developed between the strength of the material and the number of cycles of concrete recycling to anticipate the strength of the recycled aggregates concrete. From the results, it appear clear that recycling demolished concrete represents a valuable resource for aggregates supply to the concrete industry and a the same time plays a key role in meeting the challenge for a sustainable development.