• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.5
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• pp.55-64
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• 2008

Shotcrete have become a deterioration which was exposed to harmful environments. In this study, in order to evaluate the deterioration properties of shotcrete, visual examination, compressive strength, adhesive strength, microstructural analysis were investigated up to the 60th weeks of exposure. The attack solutions for test are sodium sulfate and hydrochloric acid solution with different concentrations, respectively. From the results, although the compressive strength of shotcrete specimens and the adhesive strength between specimens and rocks were high at the early immersion age, they rapidly dropped in the subsequent phases, especially in 5% sodium sulfate and pH1 hydrochloric acid solution. With continued exposure, various harmful ions penetrated into the shotcrete specimen, reacted with the cement hydrate, and generated expansion substances. It was verified that the shotcrete specimens suffered a serious deterioration by chemical attack.

• Computers and Concrete
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• v.23 no.3
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• pp.189-201
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• 2019

Recent advances in the concrete technology are aiding in minimizing the use of conventional materials by substituting by-products of various industries and energy sources. A large amount of stone waste i.e., dust and slurry form both are being originated during natural stone processing and causing deadily effects on the environment. The disposal problem of stone waste can be resolved effectively by using waste in construction industries. In present work, Kota stone slurry powder, as a substitution of cement was used along with accelerators namely calcium nitrate and triethanolamine as additives, to study their impact on various properties of the concrete mixtures. Kota stone slurry powder (7.5%), calcium nitrate (1%) and triethanolamine (0.05%) were used separately as well in combination in different concrete mixtures. Mechanical Strength, modulus of elasticity and electrical resistivity of concrete specimens of different mix proportions under water curing were studied experimentally. The durability properties in terms of strength and electrical resistivity against sulphate and chloride solution attack at various curing ages were also studied experimentally. Results showed that accelerators and Kota stone slurry powder separately enhanced the mechanical strength and electrical resistivity; but, their combination decreased strength at all curing ages. The durability of concrete specimens was also affected under the exposure to chemical attack too. Kota stone slurry powder found to be the most effective material among all materials. Material characterization was also done to study the microstructural properties.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2010.05a
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• pp.77-81
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• 2010

This study deals with the analysis of color-difference and physical property of anti-corrosion coatings using at inside of concrete tank for drinking water. Because anti-corrosion coatings are effected by chemical attack, color and physical property are changed. So in this study when epoxy resin coatings of 3 types were received chemical attack by Cl- and NaOH, we present the co-relationship between color-difference and bond strength. For this study, we used the colorimetry, which can measure the degree of color difference on surface of materials. As the results, in case of Cl-, color change is appeared, bond strength also is decreased. From this experiment, we could know that color change due to chemical aging has the deep relationship with physical performance(bond strength) materials. further researches are needed.

• Proceedings of the Korea Concrete Institute Conference
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• 1995.10a
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• pp.30-34
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• 1995

There are carbonatiion, salt attack, freezing & thawing and alkali-aggregate reactions as the cautions of durability lowering of concret structure. Generally, these cautions complicatedly lower the durability of structure and among these cautions the most serious problem is salt attack and carbonation. This study is intending to get the carbonation phenominon, that among cement calcium hydroxides change into calcium carbonate by responding to carbon mitrogen in the air.

• Bulletin of the Korean Chemical Society
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• v.33 no.3
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• pp.1042-1046
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• 2012

The kinetics and mechanism of the pyridinolysis ($XC_5H_4N$) of diethyl isothiocyanophosphate are investigated in acetonitrile at $55.0^{\circ}C$. The Hammett and Bronsted plots for substituent X variations in the nucleophiles exhibit the two discrete slopes with a break region between X = 3-Ac and 4-Ac. These are interpreted to indicate a mechanistic change at the break region from a concerted to a stepwise mechanism with rate-limiting expulsion of the isothiocyanate leaving group from a trigonal bipyramidal pentacoordinated intermediate. The relatively large ${\beta}_x$ values with more basic and less basic pyridines imply much greater fraction of frontside nucleophilic attack TSf than that of backside attack TSb.

• Bulletin of the Korean Chemical Society
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• v.33 no.10
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• pp.3203-3207
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• 2012

The nucleophilic substitution reactions of diisopropyl chlorothiophosphate (5) with X-pyridines have been kinetically studied in MeCN at $35.0^{\circ}C$. The Hammett and Br$\ddot{o}$nsted plots for the substituent X variations in the nucleophiles show biphasic concave upwards with a break point at X = 3-Ph. The pyridinolysis rate of 5 exhibits great negative deviation from the Taft plot. A concerted $S_N2$ mechanism is proposed involving a change of the attacking direction of the X-pyridines from a frontside attack with the strongly basic pyridines to a backside attack with the weakly basic pyridines.

• Bulletin of the Korean Chemical Society
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• v.35 no.9
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• pp.2797-2802
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• 2014

Nucleophilic substitution reactions of Y-aryl methyl (8) and Y-aryl propyl (10) chlorothiophosphates with substituted anilines and deuterated anilines are investigated kinetically in acetonitrile at $55.0^{\circ}C$. A concerted mechanism is proposed for 8 based on the negative ${\rho}_{XY}$ (= -0.23) value, while a stepwise mechanism with a rate-limiting leaving group departure from the intermediate is proposed for 10 based on the positive ${\rho}_{XY}$ (= +0.68) value. The deuterium kinetic isotope effects (DKIEs; $k_H/k_D$) are 0.89-1.28 and 0.62-1.20 with 8 and 10, respectively. Primary normal and secondary inverse DKIEs are rationalized by a frontside attack involving hydrogen bonded, four-center-type transition state and backside attack involving in-line-type transition state, respectively.

• Bulletin of the Korean Chemical Society
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• v.34 no.6
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• pp.1829-1834
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• 2013

The nucleophilic substitution reactions of Y-aryl ethyl isothiocyanophosphates with substituted X-anilines and deuterated X-anilines were investigated kinetically in acetonitrile at $75.0^{\circ}C$. The free energy relationships with X in the nucleophiles exhibited biphasic concave downwards with a break point at X = H. A stepwise mechanism with rate-limiting bond formation for strongly basic anilines and with rate-limiting bond breaking for weakly basic anilines is proposed based on the negative and positive ${\rho}_{XY}$ values, respectively. The deuterium kinetic isotope effects (DKIEs; $k_H/k_D$) changed gradually from primary normal with strongly basic anilines, via primary normal and secondary inverse with aniline, to secondary inverse with weakly basic anilines. The primary normal and secondary inverse DKIEs were rationalized by frontside attack involving hydrogen bonded, four-center-type TSf and backside attack involving in-line-type TSb, respectively.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.196-199
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• 2004

Metakaolin is a cementitious material for producing high-strength concrete. This material is now used as substitute for silica-fume. In this paper, we tested the compressive strength of concrete according to the substitute ratio of metakaolin, silica-fume. And we did the durability test such as chloride ion diffusion and chemical attack. In the compressive strength test, the result shows that $10\%$ substitute of metakaolin & silica-fume for binder is optimum. In the chloride ion diffusion test, according to the increase of substitute of metakaolin & silica-fume for binder, the diffusion coefficient is more reduced. And in the chemical attack test, according to the increase of substitute, the resistance is more excellent. In the durability test, we recognized that metakaolin is able to used as a substitute for silica-fume.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.790-793
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• 2004

The factors influencing concrete deterioration in marine environment can be generally divided into the physical and chemical action. The physical attack due to drying and wetting would increase the internal stress of concrete. The chemical attack resulting from the diffusion of ions$(i,e,\;Cl^-,SO_4^{2-},Mg^+)$ from seawater through the pores in concrete. The objective of this study is to evaluate corrosion characteristics of steel when using the various concrete materials under marine exposure environment. After 3 years of exposure, concrete specimen incorporating $40\%$ blast-furnace slag as replacement for type I cement with low w/c ratio of 0.42 and using the inhibitor shows excellent performance.