• Journal of the Korea institute for structural maintenance and inspection
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• v.28 no.2
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• pp.69-76
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• 2024

The rheological properties of fresh concrete significantly influence its manufacturing and performance. However, the diversification of newly developed mixtures and manufacturing techniques has made it challenging to accurately predict these properties using traditional empirical methods. This study introduces a multiscale rheological property prediction model designed to quantitatively anticipate the rheological characteristics from nano-scale interparticle interactions, such as those among cement particles, to micro-scale behaviors, such as those involving fine aggregates. The Yield Stress Model (YODEL), the Chateau-Ovarlez-Trung equation, and the Krieger-Dougherty equation were utilized to predict the yield stress for cement paste and mortar, as well as the plastic viscosity. Initially, predictions were made for the paste scale, using the water-cement ratio (W/C) of the cement paste. These predictions then served as a basis for further forecasting of the rheological properties at the mortar scale, incorporating the same W/C and adding the cement-sand volume ratio (C/S). Lastly, the practicality of the predictive model was assessed by comparing the forecasted outcomes to experimental results obtained from rotational rheometer.

• Journal of the Korean Recycled Construction Resources Institute
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• v.12 no.2
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• pp.206-213
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• 2024

The present study concerns the inhibition of Calcium Nitrite Inhibitor(Ca(NO₂)₂) in mortar contaminated by chloride ions. Thus, the corrosion resistance and chloride transport were measured for the mortar containing calcium nitrite inhibitor. As a result, an increase in the dosage of calcium nitrite inhibitor resulted in an increase in the chloride threshold concentration for reinforcement corrosion, while the rate of chloride transport was accelerated. However, the calcium nitrite inhibitor could not guarantee the time to corrosion, due to the increased mobility of chlorides. To ensure the passivity of steel, the dosage of calcium nitrite inhibitor must exceed a certain dosage, ranging from 2.0~3.0 % by cement weight.

• Journal of the Korean Ceramic Society
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• v.42 no.3 s.274
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• pp.198-204
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• 2005

Fluosilicate salts based hydration heat reducer(SWP-HR), used in this study, is composed of fluosilicate salts, soluble silica, aromatic polymer condensate and nitrate salt based inorganic compound with latent heat property. Effects of SWP-HR addition on the hydration heat and anti-crack property of cement mortar were investigated. Adiabatic hydration temperature and drying shrinkage length of SWP-HR added cement mortar had a tendency to decrease compared to those of cement mortar without SWP-HR addition. Also, it was confirmed through crack pattern experiment of plate-form specimen for elucidating crack-reducing characteristic that anti-crack property of SWP-HR added cement mortar was improved.

• Journal of the Korea Concrete Institute
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• v.14 no.2
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• pp.164-170
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• 2002

Effect of the polymer-binder ratio and slag content on the properties of combined wet/dry-cured polymer-modified mortars using granulated blast-furnace slag are examined. Results shows that the flexural and compressive strengths of polymer-modified mortar using the slag tend to increase with increasing slag content, and reaches a maximum at a slag content of 40 ％, and is inclined to increase with increasing polymer-binder ratio. Water absorption, carbonation depth and chloride ion penetration depth tend to decrease with increasing polymer-binder ratio and slag content. Accordingly, the incorporation of slag into polymer-modified mortars at a slag content of 40％ is recommended for a combined wet/dry curing regardless of the types of polymer.

• Journal of the Korea Concrete Institute
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• v.28 no.4
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• pp.395-405
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• 2016

The thermal and mechanical properties of fiber-reinforced mortars for thermal energy storage were investigated in this paper. The effect of the combination of different cementitious composite on the thermal and mechanical characteristics of fiber-reinforced mortars was investigated. Experiments were performed to measure mechanical properties including compressive strength before and after thermal cycling and split tensile strength, and to measure thermal properties including thermal conductivity and specific heat. The results showed that the residual compressive strength of mixtures with OPC and graphite was greatest among the mixtures. Thermal conductivity of mixtures with alumina cement was greater than that of mixtures with OPC, indicating favor of alumina cement for charging and discharging in thermal energy storage system. The addition of zirconium into alumina cement increased specific heat of mixtures. Test results of this study could be used to provide information of material properties for thermal energy storage concrete.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.2
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• pp.137-143
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• 2017

There has been a number of research on concrete durability. specially, as a research on chemical ingression, the research on the degradation against acid, alkali, and sulfate has been conducted. On the other hand, for the research on oils, especially, the influence of various oils on cement mortar with Supplementary Cementitious Materials(SCMs) is not sufficiently studied. hence, in this research, the degradation of cement mortar incorporated fly ash and blast furnace slag is researched when the cement mortar is submerged in various oils. For the result of experiment, as the content of fatty acid in the oils, the degradation of cement mortar with SCMs was occurred more, and the cement mortar with SCMs suffered more degradation than the ordinary portland cement regarding the oil submerging.

• Journal of the Korea Institute of Building Construction
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• v.18 no.4
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• pp.329-335
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• 2018

The objective of this study is to develop a mortar mixture with high workability and adhesive strength for section jacketing in seismic strengthening technology of existing concrete structures. To achieve targeted requirements of the mortars (initial flow exceeding 200 mm, compressive strength of 30MPa, and adhesive strength exceeding 1MPa), step-by-step tests were conducted under the variation of the following mixture parameters: water-to-binder ratio, sand-to-binder ratio, polymer-to-binder ratio, dosage of viscosity agent, and content of ultra-rapid-hardening cement. The adhesive strength of the mortars was also estimated with respect to the various surface treatment states of existing concrete. Based on the test results, the mortar mixture with the polymer-to-binder ratio of 10% and the content of ultra-rapid-hardening cement of 5% can be recommended for the section jacketing materials. The recommended mortar mixture satisfied the targeted requirements as follows: initial flow of 220 mm, high-early strength gain, 28-day compressive strength of 35MPa, and adhesive strength exceeding 1.2MPa.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.2
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• pp.127-134
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• 2021

A hydrophobic emulsion consisting of PMHS and PVA was mixed into a cement mortar to observe changes in cement hydrate and microstructure, and to experimentally evaluate compressive strength and flexural strength. The hydrophobic emulsion was added with metakaolin and PVA fibers, and the stirring speed and sequence were adjusted to prepare a shell-concept hydrophobic emulsion. It was then mixed when mixing mortar to enhance filling of the internal pores and change of the hydrates. It was observed that the mortar mixed with a hydrophobic emulsion was filled with micropores and a coating film was formed on the surface of the hydrates by the emulsion. It was analyzed that the total pore area and porosity of the mortar mixed with the emulsion decreased from 30% to 60% compared to OPC, excluding the 50MK variable, which was extremely reduced and the median pore diameter decreased in some variables. It was also found that the compressive strength of the mortar mixed with emulsion 1% was increased up to 20%, but the strength of the mortar specimen mixed with 2% decreased to 50%.

• Journal of Conservation Science
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• v.27 no.3
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• pp.313-322
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• 2011

The floral wall of Lee Sang-beom's House and Atelier, which is No. 171 of the Registrated Cultural Heritage was conserved. In addition, materials characteristics and manufacturing technique have revealed through the scientific analysis. As a result of the analysis, samples were divided into three sections; the support layer that is made from block bricks, the paint layer and the cement mortar layer on the paint layer for the reinforcement of the construction. The higher layer lies, the finer grains it has. Furthermore, a little it was generated a small quantity of pores and calcium carbonates ($CaCO_3$) generated due to aeration of cement mortar. The patterns of letters, animals and plants pattern were expressed in the paint layer by relief and openwork. The results of qualitative analysis of the pigments of the paint layer were detected components of carbon black (C), Fe oxide ($Fe_2O_3$) and oyster shell white ($CaCO_3$, or quicklime). On the other hands, as the conservation of the floral wall, stainless frames were set up for the structural stability, the cement mortar were removed from the surface and the partly damaged and cracked areas were filled with KSE Filler A, B.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.6A
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• pp.427-435
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• 2012

In order to evaluate the effects of exposure conditions on the resistance to sulfate attack of normal and blended cement mortars, several mechanical characteristics of the mortars such as expansion, strength and bulk density were regularly monitored for 52 cycles under sodium sulfate attack. The mortar specimens were exposed to 3 different types of exposure conditions; 1) continuous full immersion(Exposure A), continuous half-immersion(Exposure B) and cyclic wetting-drying(Exposure C). Experimental results indicated that the maximum deterioration was noted in OPC mortar specimens subjected to Exposure B, showing the wide cracks in the portions where attacking solution is adjacent to air. Additionally, the beneficial effect of ground granulated blast-furnace slag and silica fume was clearly observed showing a superior resistance against sodium sulfate attack, because of its lower permeability and densified structure. Thus, it is suggested that when concrete made with normal cement is exposed to sulfate environment, proper considerations on the exposure conditions should be taken.