• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.1
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• pp.67-73
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• 2020

In this study, the self-healing performance of mortar beams containing self-healing materials was evaluated through experiments. Normal mortar beams and self-healing mortar beams were used In the experiments. The self-healing performance was evaluated by comparing the mortar compressive strength, member strength, and self-healing effects of cracks. The experimental results showed that the compressive strength of mortar containing self-healing material was smaller than that of normal mortar, but the ratio of 118 days compressive strength to 28 days compressive strength was the same. The member strength tended to increase with increasing curing period. In normal mortar specimens, the member strength did not recover even if the curing period increased, but the strength of the self-healing mortar specimens tended to recover as reaction products were produced. The crack width tended to decrease after the healing periods in both specimens, but the reaction product was observed only in the self-healing mortar specimens.

• Magazine of the Korean Society of Agricultural Engineers
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• v.24 no.3
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• pp.92-99
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• 1982

The objective of this study was to investigate the compressive and bending strength characteristics of epoxy resin mortar, which is still in an early stage of its use and study in Korea. The results obtained are summarized as follows; 1. The compressive strengths of epoxy resin mortar after 1 day, 2 days and 3 days were gained 87%, 91% and 95%, respectively, in view of that of mortar at the age of 7 days. This result showed that the initial compressive strength within 1 day was very high. 2. The highest compressive strength of epoxy resin mortar was 914 kg/cm2 at the point of having the mixing ratio of one to two. It reached up to 3.7 times that of the normal portland cement mortar at the age of 28 days. 3. The bending strengths of epoxy resin mortar after 1 day, 2 days and 3 days came up to 88%, 93% and 97%, respectively, in comparing that of mortar at the age of 7 days. It was expressed to be simielar to the tendency of compressive strength. 4. The highest bending strength of epoxy resin mortar was 384 kg/cm2 at mixing ratio of one to two. It came up to as much as 6.5 times in comparing with that of the normal portland cement mortar at the age of 28 days. Therefore, the epoxy resin mortar would be effective for promoting the bending strength of structural members. 5. The regression equation between compressive and bending strength was obtained as follows; oo~=0.391 oc+27.54 (r=0.99) And the estimated value of bending strength was corresponded to about 44 per cent in comparing with that of the compressive strength.

• Structural Engineering and Mechanics
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• v.17 no.2
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• pp.141-152
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• 2004

The bonding behaviors of Lightweight Aggregate Concrete (LWAC) and normal weight concrete were investigated experimentally. Pull-out tests were carried out to measure the bond strengths of three groups of specimens with compressive strength levels of 60, 40, and 20 MPa, respectively. Test results showed that the difference in the bond failure pattern between LWAC and normal weight concrete was significant as the concrete compressive strength became lower than 40 MPa. The corresponding bond strengths of LWAC were lower than that for normal weight concrete. As the compressive strength of concrete became relatively high (> 40 MPa), a bond failure pattern in normal weight concrete occurred that was similar to that in LWAC. The bond strength of LWAC is higher than that for normal weight concrete because it possesses higher mortar strength. Stirrup use leads to an increase of approximately 20% in nominal bond strength for both types of concrete at any strength level.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.11a
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• pp.75-76
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• 2017

In this study, it is speculated that the special admixture can be mixed with ERCO beforehand to prevent adsorption of cement and AE at the time of contamination together with water, and the change in the amount of special admixture preliminarily added to ERCO We will try to analyze the influence on normal strength mortar. As a result, the flow quantity, the air quantity, the compressive strength and the flexural strength were improved as the added amount of the special admixture was increased, and When the special admixture with the addition amount of ERCO 3% was added, the strength was rather lowered. Therefore, it was found that the optimum amount of special admixture added to ERCO was 2%.

• Polymer(Korea)
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• v.34 no.3
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• pp.247-252
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• 2010

This paper investigates the effects of the monomer ratios on the typical properties of polymer-modified mortars that contain methyl methacrylate-based latexes. Basic data are also obtained to develop appropriate latexes for cement modifiers. Polymer-modified mortars that contain methyl methacrylate latexes copolymerized with butyl acrylate or ethyl acrylate are prepared for different polymer-cement ratios. They are then tested to obtain the tensile and tensile adhesive strengthes of polymer-modified mortar with methyl methacrylate-based latexes. From the test results, the tensile strength of MB7 polymer-modified mortar was higher than normal cement mortar by a maximum of 94% with a 20% polymer-cement ratio, which was almost twice higher than normal. The tensile adhesive strength of the MB polymer-modified mortar was higher for higher MMA monomer contents and polymer-cement ratios, and increased up to four times than that of normal cement mortar. The basic properties of the polymer-modified mortars are more affected by the polymer-cement ratio than by the monomer ratio, and are improved over unmodified mortar.

• Tunnel and Underground Space
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• v.4 no.3
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• pp.261-273
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• 1994

Direct shear tests were carried out on the rock joints and artificial discontinuities to investigate the influence of joint roughness on the shear strength and deformation behaviour. Single direct shear testing apparatus used in experiment was designed and manufactured. Its capacity is 200 tons of shear load, 20 tons of normal load and 50$\textrm{cm}^2$ of maximum shear area. Test samples were cement mortar with artificial discontinuity and sandstone with natural joint. Peak shear strength was increased as joint roughness or normal stress was increased, especially, linearly increased with roughness angle in cement mortar. If joint roughness angle was constant at low normal stress, shear strength was not affected by width and height of joint roughness in cement mortar. Peak shear strengths obtained from tests were larger than the values calculated by Barton's equation, and shear stiffness was increased with joint roughness coefficient.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.11a
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• pp.148-149
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• 2014

The aim of this research is to contribute on investment of less cement mortar or concrete in normal strength range using additional hydration of BS with stimulating effect of FGD and OPC based on the previous research result of the BS and RFA using cement mortar. As a test, the composition for normal strength range of mortar was evaluated with 0, 10, and 20 % of FDA and 0, 20 % of OPC replacement.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.11a
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• pp.31-32
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• 2020

This study measured the mechanical performance and residual strength of high strength/normal strength mortar mixed with waste glass fine aggregate after alkali-silica reaction and alkali-silica reaction. As a result, the effect of improving the slip phenomenon of the waste glass fine aggregate in the high-strength mortar was not significant, but rather the amount of ASR was increased.

• Journal of the Korea Concrete Institute
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• v.27 no.5
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• pp.531-539
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• 2015

Properties of normal-strength mortar containing coarsely-crushed coal bottom ash considering standard particle size distribution of fine aggregate were investigated. Mortar containing raw bottom ash was applied as a reference. By crushing the bottom ash with a particle size larger than fine binder but smaller than fine aggregates, i.e., coarse-crushing, water absorption and specific gravity of the particles could be controlled as similar levels to those of natural fine aggregates. Workability and strength of the mortar were not changed and even increased when the coarsely-crushed bottom ash was added considering standard particle size distribution in Standard Specification for Concrete, while those were decreased when raw bottom ash was added without any treatment. When a replacement ratio of coarsely-crushed bottom ash was less than 30 vol.%, there were no significant decrease in dynamic modulus of elasticity and dry shrinkage of the mortar.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.193-196
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• 2003

In this paper, the experimental investigation for the setting properties of cement paste, the consistency and strength properties of mortar with steel furnace slag dust was performed and compared with those of cement paste and mortar with ground granulated blast furnace slag. When steel furnace slag dust was replaced with normal portland cement, setting time and flow value indicated to good results like as mortar with ground granulated blast furnace slag. However, mortar with steel furnace slag dust expressed to appreciably strength devaluation according to containing ratio, and did not indicate the pozzolanic reaction like as ground granulated blast furnace slag.