• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.1A
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• pp.53-59
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• 2010

Recently, NDTs (Non-Destructive Techniques) using infrared camera are widely studied for detection of damage and void in RC (reinforced concrete) structures and they are also considered as an effective techniques for maintenance of infrastructures. The temperature on concrete surface depends on material and thermal properties such as specific heat, thermal conductivity, and thermal diffusion coefficient. Different porosity on cement mortar due to different mixture proportions can show different heat behavior in cooling stage. The porosity can affect physical and durability properties like strength and chloride diffusion coefficient as well. In this paper, active thermography which uses flash for heat induction is utilized and thermal characteristics on surface are evaluated. Samples of cement mortar with W/C (water to cement ratio) of 0.55 and 0.65 are prepared and physical properties like porosity, compressive strength, and chloride diffusion coefficient are evaluated. Then infrared thermography technique is carried out in a constant room condition (temperature $20{\sim}22^{\circ}C$ and relative humidity 55-60%). The mortar samples with higher porosity shows higher residual temperature at the cooling stage and also shows reduced critical time which shows constant temperature due to back wall effect. Furthermore, simple equation for critical time of back wall effect is suggested with porosity and experimental constants. These characteristics indicate the applicability of infrared thermography as an NDT for quality assessment of cement based composite like concrete. Physical properties and thermal behavior in cement mortar with different porosity are analyzed in discussed in this paper.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.327-328
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• 2009

This study was conducted to substitute blast furnace slag powder and gypsum activator for the purpose of improving mortar quality with fine particle cement extracted using particle size screening in the cement manufacturing process. While flowability and early strength were reduced, partial compressive strength showed increase on the 28th day.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.2
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• pp.81-88
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• 2011

This study ascertained the possibility of use of sulfur abstracted from waste sulfur as a construction material through modification process and manufacturing high efficiency modification sulfur with superior quality on dispersibility and hydrophilic in normal temperature. Mechanic, behavior and chemical durability of mortar with added modification sulfur. The results of the study are as follows. The fluidity of mortar mixed with modification sulfur and compressive strength decreased as ratio of mixing of them increases. Flexural, tensile and bond strength of the mortar are also improved and shrinkage of it increases. Especially chemical durability of the mortar showed excellent resistance with the increase of ratio of mixing. Therefore this research has confirmed the modification sulfur can be used as a addmixture for cement.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2007.04a
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• pp.51-54
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• 2007

This study investigates the properties of paste and mortar from different types and forms of silica fume on cement binder for ultra high strength. Although most Silica Fumes distributed in the market fulfill the KS quality standard, each type showed different levels of loss of ignition. When evaluating cement binder for ultra high strength in a form of paste. Flow, viscosity and moving freely time show great difference depending on the Silica Fume's form and type of primary particle's dispersibility. The evaluation of Silica Fume's dispersibility can be possible with the paste test since there is a high correlation of flow quality between paste and mortar. The compressive strength when using Silica Fume was correlated to the SiO2 content. Synthetically, selecting Silica Fume with the most the ideal primary particle is the key to optimizing the formation for cement binder for ultra high strength.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.4
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• pp.99-105
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• 2010

This study analyzed the effects of changes in mixing factors of zero-cement mortar that only used recycled fine aggregates and fly-ash on quality of mortar, and the results are as follows. To describe the property of fresh mortar, as mix proportion and flow of mortar increased, W/B was highly selected and air content decreased. To describe compressive strength according to age as the property of hardened mortar, it was revealed that the strength did not strength until the 14 day, but strength of about 1 ~ 2 MPa strength during the 14 day through 28 day, and almost similar strength after 28 day. Also, compressive strength according to changes in mix proportion, flow and B/W was generally similar. Summarizing the above experimental results, in case of mortar that used recycled fine aggregates and fly-ash, it secured the strength for the use of landfill even though not for structural use. Especially, poor mix proved to be more useful than rich mix.

• Journal of the Korea Concrete Institute
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• v.28 no.4
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• pp.387-394
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• 2016

This study was evaluated that fundamental quality properties in the mortar level, as part of a basic study for development of fiber reinforced concrete using basalt fiber. Mortar mixtures used in the experiments used the mortar using cement only and high volume fly ash mortar using fly ash of 50%, was evaluated by comparison. As a experiments results, high volume fly ash mortar using 50% fly ash was effective for improving fiber dispersibility than mortar using cement only, accordingly, it showed that fiber aggregation phenomenon has been greatly reduced. In addition, if the fly ash used much more than 50%, the compressive strength has been shown to decrease of about 30%, fiber length and mixing ratio of basalt fiber was found to have a greater effect on flow properties than mechanical properties.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.05a
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• pp.47-48
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• 2016

Recently over the world, many studies on the methods for using some binding materials which replace cement, such as FA, etc., for reducing CO₂. However, it has sometimes been reported that some cement products without passing through the refining process at some of FA refineries in Korea are released for sales for some reasons of shortening the production time and the cost reduction, etc., so it exerts a bad effect on the quality of many construction structures. Therefore, in this study, it was intended to conduct an experimental review on the effects of using an extreme quality of FA which is distributable domestically on the engineering characteristics of high-strength mortar. As a result, it was judged that it is beneficial for the engineering characteristics of concrete, such as, flow property, air volume and strength, etc, to use some refined FA.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.10a
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• pp.56-57
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• 2016

Recently amongst Korea's construction companies there has been heightened interest in environment load reduction and resource recycling. As a result, the construction industry is examining recycled materials alternative to cement and blast-furnace slag (BS henceforth) cement, such as waste refractories and desulfurized plaster. This study analyzes the liquidity and intensity characteristics of mortar according to changes in replacement ratios of waste refractories and desulfurized plaster, used as industry by-products in mortar environments that use BS 3-type cements and circulated fine aggregate. As a result, the greater the increase in replacement ratios of desulfurized plaster, the greater the increase in liquidity and air quantity, as well as compression strength.

• Journal of the Korea Institute of Building Construction
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• v.19 no.2
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• pp.105-112
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• 2019

Fine aggregate made of ferronickel slag(FNS) is similar to natural fine aggregates and is used in concrete structures both domestically and abroad, but its applications and research areas are limited. In this research, in order to expand the availability of FNS and improve the performance of cement mortar products, the applicability of FNS on dry mortar for floor was examined. Experimental results show that FNS improves flow of cement mortar because it has low absorption rate, spherical shape, and glassy surface. Also, the high stiffness of the FNS aggregate itself is considered to contribute to the improvement of cement mortar quality such as crack reduction by improving the compressive strength and shrinkage reducing. In addition, when FNS fine aggregate is applied, it was possible to secure the impact sound insulation performance equal to or higher than that of mortar using natural fine aggregate.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.05a
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• pp.54-55
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• 2018

Reinforced concrete is a building material that is generally used in modern society. Securing the performance of reinforced concrete is directly connected to the durability and longevity of the building. One of the major factors that deteriorate the durability of concrete is harmful ion. Recently, the quality and improvement method of reinforced concrete for penetration of harmful ion has been studied. In this study, the bead type ion exchange resin is substituted for 0%, 3%, and 6% of the fine aggregate volume in the mortar. The speciments underwent underwater curing and were checked for compressive strengths of 3 days and 28 days. From the results of compressive strength, it can be seen that the higher the substitution ratio of the ion exchange resin, the lower the early strength and long-term strength development, especially the early strength development.