• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.469-472
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• 2006

The use of admixture(PNS type & PC type) played a important role in the development of rapid hardening concrete. This paper presents an experimental study on the effect of a kinds of admixture on hydration characteristics, mini slump, apparent viscosity of fresh cement pastes and workability, compressive strength properties of hardened concrete for rapid hardening. Measurements have showed that their characteristics depends on the type of the admixture. As a result, the excellent quality was obtained, also being widely used for the construction field is expected.

• Architectural research
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• v.20 no.1
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• pp.27-34
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• 2018

To improve the chloride ingress resistance of concrete, slag is widely used as a mineral admixture in concrete industry. And currently, most of experimental investigations about non steady state diffusion tests of chloride penetration are started after four weeks standard curing of concrete. For slag blended concrete, during submerged chloride penetration tests periods, binder reaction proceeds continuously, and chloride diffusivity decreases. However, so far the dependence of chloride ingress on curing ages are not detailed considered. To address this disadvantage, this paper shows a numerical procedure to analyze simultaneously binder hydration reactions and chloride ion penetration process. First, using a slag blended cement hydration model, degree of reactions of binders, combined water, and capillary porosity of hardening blended concrete are determined. Second, the dependences of chloride diffusivity on capillary porosity of slag blended concrete are clarified. Third, by considering time dependent chloride diffusivity and surface chloride content, chloride penetration profiles in hardening concrete are calculated. The proposed prediction model is verified through chloride immersion penetration test results of concrete with different water to binder ratios and slag contents.

• Journal of Korean Association for Spatial Structures
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• v.15 no.2
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• pp.69-77
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• 2015

Ultra High Performance Fiber Reinforced Concrete (UHPFRC) has a outstanding tensile hardening behaviour after a crack develops, which gives ductility to structures. Existing shear strength model for fiber reinforced concrete is entirely based on crack opening behavior(mode I) which comes from flexural-shear failure, not considering shear-slip behavior(mode II). To find out the mode I and mode II behavior on a crack in UHPFRC simultaneously, maximum shear strength of cracked UHPFRC is investigated from twenty-four push-off test results. The shear stress on a crack is derived as variable of initial crack width and fiber volume ratio. Test results show that shear slippage is proportional to crack opening, which leads to relationship between shear transfer strength and crack width. Based on the test results a hypothesis is proposed for the physical mechanics of shear transfer in UHPFRC by tensile hardening behavior in stead of aggregate interlocking in reinforced concrete. Shear transfer strength based on tensile hardening behavior in UHPFRC is suggested and this suggestion was verified by comparing direct tensile test results and push-off test results.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.211-212
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• 2009

In this study, the fresh properties and compressive strength of Strain-Hardening Cement Composites is compared between manufactured by ready-mixed concrete batcher mixer and small mixer in laboratory.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.213-214
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• 2009

In this study, the banding stress and tensile strength of Strain-Hardening Cement Composites is compared between manufactured by ready-mixed concrete batcher mixer and small mixer in laboratory.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.05a
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• pp.38-39
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• 2015

This study reviewed slump and air content as pre-hardening characteristics depending on B/P production of amorphous steel fiber-reinforced concrete and evaluated compressive strength, flexural strength and tensile strength as post-hardening characteristics depending on B/P production of amorphous steel fiber-reinforced concrete.

• Journal of the Korea Concrete Institute
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• v.24 no.4
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• pp.361-368
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• 2012

Required performance for repair materials are strength, ductility, durability and bonding with the substrate concrete. Various kinds of fiber-reinforced cement composites (FRCCs) have been developed and used as repair materials. Strain-hardening cement based composites (SHCC) is one of the effective repair materials that can be used to improve crack-damage tolerance of reinforced concrete (RC) structures. SHCC is a superior FRCC that has multiple cracking characteristic and pseudo strain-hardening behavior. The expansive admixture, which can be used to reduce shrinkage in SHCC materials with less workability by controlling interfacial bonding performance between SHCC and substrate concrete. For the application of SHCC as a repair material to RC structures, this study investigates the flexural performance of expansive SHCC-layered concrete beam. Test variables include the replacement levels of expansive admixture (0 and 10%), repair thickness (30 and 40 mm), and compressive strength of SHCC (30, 70 and 100 MPa). Four point bending tests on concrete beams strengthened with SHCCs were carried out to evaluate the contribution of SHCC on the flexural capacity. The result suggested that expansive SHCC materials can be used for repairing and strengthening of concrete infrastructures.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.11a
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• pp.221-222
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• 2012

This study is to high early concrete development which reveals 14 MPa within 12 hours in order to reduce the mold time of dismantlement and not do the steam curing of the precast concrete product. About (40~50) min could shorten the final setting time if the coagulation test result cement amount 100 kg/m3 was increased. In the case of the compressive strength, it was exposed to be satisfied the target value with the cement amount 500 kg/m3 combination according to the hardening accelerator addition.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.153-158
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• 2001

The effects of polymer-cement ratio and shrinkage-reducing agent content on the durability characteristics of ultrarapid-hardening polymer-modified mortars using redispersible polymer powder are examined. As a result, the flexural and tensile strengths of the ultrarapid-hardening polymer-modified mortars using redispersible polymer powder tend to increase with increasing polymer-cement ratio, and tend to decrease with increasing shrinkage-reducing agent content. However, the compressive strength of the ultrarapid-hardening polymer-modified mortars using redispersible polymer powder decrease with increasing polymer-cement ratio and shrinkage-reducing agent content. And, water absorption and mass change of chemicals resistance of ultrarapid-hardening polymer-modified mortars using redispersible polymer powder tend to decrease with increasing polymer-cement ratio.

• International Journal of Concrete Structures and Materials
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• v.10 no.2
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• pp.249-256
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• 2016

This paper deals with the effects of silica fume content and polymer-binder ratio on the properties of ultrarapid-hardening polymer-modified mortar using silica fume and ethylene-vinyl acetate redispersible polymer powder instead of styrene-butadiene rubber latex to shorten the hardening time. The ultrarapid-hardening polymer-modified mortar was prepared with various silica fume contents and polymer-binder ratios, and tested flexural strength, compressive strength, water absorption, carbonation depth and chloride ion penetration depth. As results, the flexural, compressive and adhesion strengths of the ultrarapid-hardening polymer-modified mortar tended to increase as increasing polymer-binder ratio, and reached the maximums at 4 % of silica fume content. The water absorption, carbonation and chloride ion penetration resistance were improved according to silica fume content and polymer-binder ratio.