• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.1
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• pp.72-79
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• 2007

This study investigates the engineering properties of concrete incorporating lime stone crushed fine aggregate(Ls), which has been abandoned about 20% of total production due to the low purity. Test results showed that increase of Ls had favorable fluidity and slightly decreased air content. Bleeding capacity of all specimens was not appeared as those were high strength mixture proportion, but the specimens using more Ls accelerated initial and final setting. For the mechanical properties, specimens incorporating higher ratio of Ls, overall, resulted in increase of compressive strength, and exhibited very small inclined tendency in a dynamic elasticity modulus test In addition, for the durability properties, specimens incorporating higher Ls dramatically decreased a drying shrinkage and showed similar tendency in a frost & thaw test, as well as showing no more change in an accelerated neutralization test from the beginning. In conclusion, as it was confirmed in the experimental test, the high strength concrete applying Ls did not showed any problems in the aspects of engineering properties and mostly exhibited even more excellent quality than the specimens using natural fine aggregate.

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

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.183-188
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• 2002

When Concrete work during winter is placed, it has anxiety that concrete freeze at low temperature. As concrete's freezing cause reduction of durability, it is necessary for mixing to pay attention to Air content and W/C ratios. Accordingly, in this study, we set up three series and evaluate a frost-resistance of concrete with admixture, like fly-ash and blast-furnace slag, for early curing method and types of chemical admixture..The study is composed as; I series : Analysis for early curing method and types of chemical admixture in laboratory II series : Analysis for early curing method and types of chemical admixture in batcher plant and measured concrete' temperature. The result of this study, it was more effective the use of super-plasticizers than air entraining agent.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.641-644
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• 2006

Considering properties of the low-heat concrete mixed with the blended cements, the influences compared blended cements with ordinary portland cement made experiments on. (1) Blended cements were superior to OPC in the fresh concrete flow that the use of blended cements reduced chemical admixture. (2) The more the use of additive increase, the more bleeding happens. So it is considered to heights, order, and rate of placement, curing methods and so on. (3) The use of blended cements increase long term strength after 28 days, but decrease early strength and durability. So it is considered to the curing methods and early frost damage, and endurance limit.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.663-666
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• 2005

Chloride attach is one of the main factors which cause the deterioration of structures. In the case highway bridges, de-icer salts very significantly increase the surface scaling due to frost action. The deteriorated concrete is subject to experience degrading of durability under chloride attach environment. In this study, diagnosis report of 147 bridges is investigated and core sample of 21 bridge decks is examined and analyzed. The results show that the cover of decks concrete is required more than 8cm for retaining bridge lifetime over 30 years.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.2
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• pp.75-86
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• 2012

This paper presents some research results on the shrinkage characteristics and frost resistance before and after cracking of FR-ECC(Fire Resistance-Engineered Cementitious Composite). Also, a waterstop performance and exfoliating resistance of multi-layer lining specimens using FR-ECC and flexural performance of beam member by repaired FR-ECC are estimated in this paper. Experimental results indicate that the plastic shrinkage crack and length change ratio of FR-ECC have been reduced as compared with that of the existing repair mortar, and that its crack resistance on the dry shrinkage is improved under the confining stress. As well as FR-ECC has been great in the frost resistance and its tensile properties under the cracked state have been not reduced by freezing and thawing reaction. In addition, beam member by repaired FR-ECC have been increased in the flexural properties such as initial crack moment, yeild moment, and its crack width has been controled in a stable by the frexural failure.

• Journal of the Korea Concrete Institute
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• v.21 no.5
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• pp.639-647
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• 2009

In order to evaluate the durability of reinforced concrete structures under chloride attack from sea water and frost damage, it is important to analyze both the microstructural characteristics of concrete and its diffusion resistance of concrete against chloride ingress. In this study, a relation between micro-pore structures of concrete obtained by the Mercury Intrusion Porosimetry and accelerated chloride diffusivity as well as long term chloride diffusivity were studied for ground granulated blast furnace slag(GGBS) concrete. Different water-cement ratio of 40, 45, 50% and different unit cement concrete of 300, 350, 400 or 450 kg/$m^3$ of the GGBS concrete along with OPC concrete were used and freeze and thawing, and the change in diffusivity and microstructure were observed for both GGBS concrete and damaged GGBS concrete due to rapid freezing and thawing.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.3
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• pp.276-281
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• 2023

Water pipes manufactured using existing Portland cement suffer from the problem of rapid deterioration and reduced durability due to the hydration product of cement being vulnerable to acids. Therefore, in this study, water pipes were manufactured using slag and fly ash, which are industrial by-products from various industries, and their characteristics were analyzed. As a result of the experiment, slump in unhardened concrete tended to increase due to the ball bearing action of fly ash, and the amount of air was reduced due to unburned coal, indicating that measures for frost resistance were needed. In addition, the initial strength of the compressive strength was increased through steam curing, and the results were equal to or better than OPC when mixing more than 50 % of slag. The acid resistance results showed that the mass reduction rate was less than 5 %, showing excellent durability performance, and the bending failure load of the water pipe also exceeded the KS standards, so it is judged to be commercializable.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.6
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• pp.152-158
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• 2007

Chloride attach is one of the main factors which cause the deterioration of structures. In the case highway bridges, de-ice salts very significantly increase the surface scaling due to frost action. The deteriorated concrete is subject to experience degrading of durability under chloride attach environment. In this study, diagnosis report of 147 bridges is investigated and core sample of 21 bridge decks is examined and analyzed. The results show that the cover of decks concrete is required more than 8cm for retaining bridge lifetime over 30 years.

• Journal of Information Processing Systems
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• v.18 no.4
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• pp.457-469
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• 2022

Hydraulic concrete buildings in the northwest of China are often subject to the combined effects of low-temperature frost damage, during drying and wetting cycles, and salt erosion, so the study of concrete deterioration prediction is of major importance. The prediction model of the relative dynamic elastic modulus (RDEM) of four different kinds of modified concrete under the special environment in the northwest of China was established using Grey residual Markov theory. Based on the available test data, modified values of the dynamic elastic modulus were obtained based on the Grey GM(1,1) model and the residual GM(1,1) model, combined with the Markov sign correction, and the dynamic elastic modulus of concrete was predicted. The computational analysis showed that the maximum relative error of the corrected dynamic elastic modulus was significantly reduced, from 1.599% to 0.270% for the BS2 group. The analysis error showed that the model was more adjusted to the concrete mixed with fly ash and mineral powder, and its calculation error was significantly lower than that of the rest of the groups. The analysis of the data for each group proved that the model could predict the loss of dynamic elastic modulus of the deterioration of the concrete effectively, as well as the number of cycles when the concrete reached the damaged state.