• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.11a
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• pp.145-146
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• 2017

This research aimed to analyze the fundamental properties of cement mortar accompanying the change of the solid contents of the maintenance type PC water reducing agent. As a result of the experiment, it was found that the properties of fresh mortar show a tendency to decrease as the solid contents decreases in the case of flow and air contents, and the decrease width with time is small. It was found that the compressive strength of the hardened mortar has almost no difference due to the change of the solid fraction.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.11a
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• pp.68-69
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• 2019

Integrating 3D printing into architecture is gaining attention because it allows construction of construction structures without formwork. Among them, 3D printing construction materials must have high flow performance and at the same time ensure the performance that does not collapse during lamination. Therefore, in this study, we tried to determine the fluidity and lamination properties of mortar formulations, and set the thickener incorporation ratio as the formulation parameters. As a result of this experiment, it was confirmed that the lamination performance was secured from the thickening agent mixing rate of 1.5%.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.11a
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• pp.17-18
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• 2023

This study aims to compare the hardness value development characteristics according to the water-cement ratio during a series of experiments to develop a setting estimator for an AI-based concrete finishing automation system. For the test variables, water-cement ratios are varied with 30, 40 and 50%. Proctor penetration test and surface hardness test by setting time estimator are conducted to estimate the setting time. For the effect of water-cement ratios, they did not affect the surface hardness either, while initial set time and final set time are not constant with water-cement ratios.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.4
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• pp.124-131
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• 2017

The purpose of this study is to evaluate the basic performance of cement mortar for repair using alumina cement and nitrite can be cured in low temperature environment. For this purpose, the repair mortar used in the domestic construction site was selected and the experimental evaluation was carried out by adjusting the mixing amount by substituting alumina cement and nitrite for the blending ratio. The experimental test results confirmed that alumina cement and nitrite were replaced with the repair mortar, the initial strength was improved. Also, the chemical resistance was improved, the shrinkage behavior was decreased, and the resistance to freezing and thawing was increased. As a result, applying alumina cement and nitrite at a ratio of 2:1 at 7.5%, the surface condition was maintained for 5 months or longer and it was judged to be excellent in practical use for external structures.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.677-680
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• 2008

The surface of particles was energetically modified by inter-grinding OPC and BFS in vibration mill for improvement of the early strength and low-heat evolution of concretes. BFS was pre-grinding in ball-mill to 2535(BS2) and 3245 $cm^2/g$(BS3), in blaine surface area. The inter-grinding time in vibration mill was changed from 10 minutes to 30 minutes. And Mixing ration of BFS to OPC was changed in 60, 70, 80%. After inter-grinding, the change of specific surface area, particle size distribution, hydration heat of cement and compressive strength of mortar were measured. As the result of comparison test with LHC, it was found that the mixture and inter-grinding time satisfying the value of over 100% of compressive strength for 7 days and under 170J/g of heat of hydration for 72 hours. and it was confirmed that the possibility of low heat slag cement utilizing blast furnace slag(BS2, BS3) with the low fineness in high volumes.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.6
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• pp.27-32
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• 2021

This study was conducted to improve the workability of cementitious composites using nano-bubble water. The used nano-bubble water contains 7% of nano-sized bubbles with an averaged bubble size of 750 nm. Various different types of cementitious composites including ultar-high performance concrete, lightweight cementitious composites, and high-strength mortar have been tested to identify the changes of material properties. From the use of nano-bubble water, it was confirmed that workability has been improved by 3-22%. On the other hand, other material characteristics such as compressive strength did not have noticeable changes. Therefore, it was proposed that the use of nano-bubble water can enhance workability of cementitious composites without having significant impact on other material properties.

• Journal of the Korea Institute of Building Construction
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• v.22 no.5
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• pp.441-450
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• 2022

In this study, the fluidity and strength characteristics of NSC mortar according to the type and rate of addition of superplasticizer were analyzed to secure the fluidity of NSC composed of only slag and ash. Through the flow test, it was found that the fluidity of NSC was related to the basicity according to the binder condition, and the lower the reactivity, the higher the fluidity. When polycarboxylate is added, NSC mortar is considered to be more advantageous than plain mortar in terms of securing fluidity. As a result of the strength tests of NSC mortar containing Lignin or Polycarboxylate superplasticizer, it was found that the strength tends to increase as the basicity increases. In addition, when polycarboxylate is added, it is judged that the NSC mortar can secure adequate fluidity and strength at the same time. Through this experiment, an appropriate binder condition that satisfies the flowability while securing the strength was derived.

• Journal of the Korean GEO-environmental Society
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• v.7 no.6
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• pp.113-119
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• 2006

Recently, the ground injection method using water glasses as one of the main resources and the products of these constructions have basic problems in terms of the method of constructions for the permanent foundation reinforcement and stopping leakage of water because they have some serious problems such as durability, compressive strength, injectant eluviation and so forth even though they are still used to stop leakage of water in the temporary structures. The purpose of this study is to demonstrate the strength characteristic and environment friendliness of NDS method by unconfined compressive strenth test, permeability test, length change test, leaching test, and assessment of environmental impact in comparison water glass type material. The test results show that NDS method has significant improvement of strength, permeability, volume change, and leaching. An assessment of environmental impact also demonstrates that the NDS material is environmentally friendly.

• Journal of the Korea Concrete Institute
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• v.17 no.3 s.87
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• pp.411-418
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• 2005

Polymer-modified mortar and concrete are prepared by mixing either a polymer or monomer in a dispersed, or liquid form with fresh cement mortar and concrete mixtures, and subsequently curing, and if necessary, the monomer contained in the mortar or concrete is polymerized in situ. Although polymers and monomers in any form such as latexes, water-soluble polymers, liquid resins, and monomers are used in cement composites such as mortar and concrete, it is very important that both cement hydration and polymer phase formation proceed well the yield a monolithic matrix phase with a network structure in which the hydrated cement phase and polymer phase interpenetrate. In the polymer-modified mortar and concrete structures, aggregates are bound by such a co-matrix phase, resulting in the superior properties of polymer-modified mortar and concrete compared to conventional mortar and concrete. The purpose of this study is to obtain the necessary basic data to develope appropriate latexes as cement modifiers, and to clarify the effects of the monomer ratios and amount of emulsifier on the properties of the polymer-modified mortars using methyl methacrylate-butyl acrylate(MMA/BA) and methyl methacrylate-ethyl acrylate(MMA/EA) latexes. The results of this study are as follows, the water absorption, chloride ion penetration depth and carbonation depth of MMA/BA-modified mortar are lowest. However, they are greatly affected by the polymer-cement ratio rather than the bound MMA content and type of polymer.

• Journal of the Korea Concrete Institute
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• v.19 no.4
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• pp.457-465
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• 2007

In this paper, polymer-modified repair materials using polymer dispersions with six repair methods are prepared with various polymer-cement ratios, and tested for compressive and flexural strengths through each curing condition such as dry cure, water cure, and freezing and thawing cyclic action. And, the adhesive interface between the polymer-modified mortar and mortar substrate is observed by a scanning electron microscope. From the test results, the compressive and flexural strengths of cement mortar repaired by polymer-modified mortar are improved with a rise in the polymer-cement ratio regardless of the type of polymer and curing conditions. Such an improvement in the strengths of polymer-modified repair materials to ordinary cement mortar is explained by the high adhesion of polymer-modified mortar. Strength reduction of polymer-modified repair materials after freezing and thawing cyclic actions is recognized, but it is lower than that of unmodified mortar. Especially, cement mortar repaired by polymer-modified mortar with a St/BA emulsion has good strength properties compared with those of SBR latex and PA emulsion. Accordingly, it is judged that polymer-modified mortars with a St/BA emulsion are possible to use as repair materials to ordinary cement mortar and concrete.