• Computers and Concrete
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• v.21 no.6
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• pp.705-715
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• 2018

This paper presents an experimentally investigation pertinent to the mechanical properties of rubberized mortar (RM) with styrene-butadiene rubber (SBR). The SBR were used with constant water-to-cement ratio of 0.485 and two different volume proportion of SBR particles were utilized as aggregates. One types of SBR particles with fineness modulus of 4.951 were utilized 0%, 10%, and 20% of aggregate volume. Effectiveness of SBR replacement ratio, curing and aging effect on the compressive strength, flexural strengths as well as load-displacement. Compressive and flexural strength of concrete were investigated at the end of 28-days and 56-days age. Obtained results demonstrated that utilization of SBR reduced the flexural strength of SBR mortar at the earlier curing age while SBR increased. Moreover, mechanical properties of mortar mentioned above were significantly affected by the water cure timing with an increasing proportion of the replacement level of SBR.

• Korean Journal of Agricultural Science
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• v.14 no.2
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• pp.358-372
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• 1987

This study was performed to obtain data which can be applied to use of water-proof mortars. The data was based on the properties of water-proof mortars depending upon various mixing ratios to compare those of cement mortar. The water-proof agents used were retard and accelerate type which are being used as mortar structures. The water-proof agents, mixing ratios of cement to fine aggregate were 1:1, 1:2, 1:3 and 1:4. The results obtained were summarised as follows; 1. The results of flow test, water-cement ratio was increased with the increasing of mixing ratio. 2. The permeability were increased in poorer mixing ratio and higher water pressure. 3. The bulk density was decreased with the increasing of mixing ratio, and compressive and tensile strength were increased with increasing of the bulk density. 4. At 1:1 mixing ratio, the highest strengths were showed and strengths were decreased with the increasing of mixing ratio. 5. The absorption rates were increased in- poorer mixing ratio 6. The correlation between W/C, permeability, bulk density, compressive strength and absorption rate were highly significant as a straight line, respectively.

• Advances in concrete construction
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• v.10 no.5
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• pp.381-391
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• 2020

This study aimed to develop reference materials (RMs) for mortar that can simulate the initial flow characteristics with constant quality over a long period. Through the previous research on the development of RMs for cement paste, the combination of limestone, glycerol, and water was used as the basic matrix for developing RMs for mortar in this study. In addition, glass beads of three particle sizes (0.5, 1.0, and 2.0 mm) and ISO standard sand were selected as tentative candidates to derive fine aggregate substitutes. The mixture of glass beads could simulate the initial flow characteristics of mortar, but under the same mixing ratio, replicates showed an unstable tendency to indicate inconsistent values due to the generation of electrostatic properties between materials and equipment. On the other hand, the mixture using ISO standard Sand not only simulates the constant flow characteristics for a long period of time, but also shows stable results with little error in replicates. Therefore, limestone, glycerol, ISO standard sand, and water were finally determined as components that met the required properties of RMs for mortar. The effect of each component on the flow characteristics of RMs was analyzed. It was found that glycerol increased the cohesion between the particles of standard sand, resulting in a constant increase both in the plastic viscosity and yield stress. Both limestone and standard sand had a dominant effect on the yield stress. The relationships between various mortar mixing ratios and the corresponding mixing ratios of RMs were established. In addition, the results of the verification experiment showed that the rheological properties of the RMs obtained through the relationships correlated with various water/cement ratios and the fine aggregate volume fractions of mortar obtained with same manner. In other words, the RMs for mortar developed in this study can be used as standard samples because they can simulate the initial flow characteristics of mortar of various mixing ratios for a long period without any chemical changes.

• Proceedings of the Korea Concrete Institute Conference
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• 1995.04a
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• pp.177-182
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• 1995

Large-scaling recycling of demolished concrete will contribute not only to the solution of a growing waste disposal problem. it will also help to conserve natural resoures of sand and gravel and to secure future supply of reasonly priced aggregates for builiding and other construction purposes within large urban areas. because recycled aggregate particles consist of substaintial amount of relatively soft cement paste component, it is less resistant to mechanical actions. With this view in mind, to obtain a reference data for the development of recycling system and to a basic data the guideline of recycled aggregate concrete construction and mix design, this study deals with the comparative analysis of the workability and engineering properties of recycled aggregate concrete according to the factors, such as blending ratio of recycled aggregate with the natural aggregate, addition of flyash, water cement ration.

• Journal of the Korea Concrete Institute
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• v.17 no.5 s.89
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• pp.709-716
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• 2005

The objective of this study is to develop a high ductile fiber reinforced mortar, ECC(Engineered Cementitious Composite) with using raw material commercially available in Korea. A single fiber pullout test and a wedge splitting test were employed to measure the bond properties in a matrix and the fracture toughness of mortar matrix respectively, which are used for designing mix proportion suitable for achieving strain-hardening behavior at a composite level. Test results showed that the properties tended to increase with decreasing water-cement ratio. A high ductile fiber reinforced mortar has been developed by employing micromechanics-based design procedure. Micromechanical analysis was initially peformed to properly select water-cement ratio, and then basic mixture proportion range was determined based on workability considerations, including desirable fiber dispersion without segregation. Subsequent direct tensile tests were performed on the composites with W/C's of 47.5% and 60% at 28 days that the fiber reinforced mortar exhibited high ductile uniaxial tension property, represented by a maximum strain capacity of 2.2%, which is around 100 times the strain capacity of normal concrete. Also, compressive tests were performed to examine high ductile fiber reinforced mortar under the compression. The test results showed that the measured value of compressive strength was from 26MPa to 34 MPa which comes under the strength of normal concrete at 28 days.

• International Journal of Concrete Structures and Materials
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• v.3 no.1
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• pp.25-32
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• 2009

A non-destructive testing (NDT) method for evaluating physical properties of concrete including the compressive strength is highly desirable. This paper presents such an NDT method based on measurement of electromagnetic (EM) properties of the material. Experiments are carried out on cement mortar with different water/cement (W/C) ratios. Their EM properties including the conductivity and the dielectric constant are measured at different exposure conditions and curing periods over a wide frequency range of the EM wave. The compressive strength of these specimens is also tested. It is found that both the conductivity and the dielectric constant increase as the W/C ratio decreases and the curing period increases, which lead strength development in the specimens. A linear correlation is observed between the averaged EM properties over the 5 to 20 GHz frequency range and the measured compressive strength, demonstrating the effectiveness of the EM property-based NDT method in evaluating strength of OPC mortar.

• Magazine of the Korea Concrete Institute
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• v.6 no.5
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• pp.158-170
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• 1994

The results of an experimental study on the manufacture and the mechanical properties of carbon fiber rekforced silica fume . cement composites and light weight fly ash . cement composites are presented in this paper. 11s the test results show, the flexural strength, fracture toughness and ductility of CF reinforced silica fume . cement composites were remarkably increased by the increase of carbon fiber contents. And the workability of the fly ash . cement composites were improved, but the compressive and flexural strength and bulk specific gravity of them are decreased by increasing the ratio of fly ash to cement. And the compressive and flexural strength of the fly ash cement composites by cured under the hot water were improved than those by mositure cured. Also, the manufacturing process technology of lightweight fly ash . cement composites in replacement of general autoclaved lightweight concrete was developed and its optimum mix proportions were proposed.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.05a
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• pp.28-29
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• 2017

Recently, the tendency of the insulation of buildings to be important is making the buildings airtight. However, in order to get closer to the technology, it is necessary to improve the performance of walls and panels of buildings, but it is a problem due to the increase of the unit price. We will review the basic data on the density and table flow characteristics of high thermal insulation materials.

• Journal of the Korea Institute of Building Construction
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• v.11 no.6
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• pp.538-546
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• 2011

This paper is to experimentally investigate the strength and autogenous shrinkage of high strength mortar with the 20 % of water?binder ratio(W/B). In this study, the water substituting liquid(WSL) was used including gasoline, light oil, lamp oil, edible oil, HFE, ethanol, methanol and acetone in order to explore changes in strength and autogenous shrinkage depending on WSL type and replacement. For fresh properties, the replacement of WSL did not affect the fluidity of mortar mixtures considerably, except for ethanol and methanol. However, the replacement of WSL resulted in a slight decrease in flexural and compressive strength. For autogenous shrinkage, the replacement of WSL led to reduce autogenous shrinkage, and especially, the replacement of edible oil led to reduce autogenous shrinkage significantly due to saponification between edible oil and cement.

• Journal of the Korea Institute of Building Construction
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• v.14 no.4
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• pp.285-291
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• 2014

Partial replacement of cement with blast furnace slag has many advantages such as the reduction of construction fee, the decrease of hydration heat and the increase of long-term strength. Hence, slag is widely used in practice. This study investigates the effect of slag on the rheological properties of cement paste and mortar. Three different types of slag (BS1, BS2 and BS3) with five different contents (0, 20, 40, 60 and 80 wt.%) were used to replace the cement. Each type of slag has different fineness. Water to binder ratio was 0.5. Test results showed that the partial replacement of BS1 and BS2 decreased flow and increased O-lot flow time, whereas that of BS3 caused an opposite effect, i.e., increased flow and decreased O-lot flow time. It was found that there was a good corelation between the values of yield stress and flow.