• Title/Summary/Keyword: repair mortar

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A Study on Early-Age bond strength of Magnesium Potassium Phosphate Mortar (마그네슘 인산칼륨 모르타르의 초기재령 부착성능에 관한 연구)

  • Kang, Hye-Ju;Lee, Yeong-Won;Kim, Jea-Hwan;Kang, Suk-Pyo
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2015.05a
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    • pp.98-99
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    • 2015
  • In the study, based on analysing bond strength of MPC and existing rapid harding grout according to shape of cross section, early ages shape of cross section is investigated about effect on bond strength to use MPC as an emergency repair material for road defects such as the form of a pot-hole. The result, MPC is about 10% higher than the shear bond strength rapid harding grout, about 20% higher bending bond strength.

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Drying Shrinkage and Strength Properties of High-Fluidity Polymer-Modified Mortar (고유동 폴리머시멘트모르타르의 건조수축 및 강도 특성)

  • Joo Myung-Ki;Lee Youn-Su;Jung In-Su
    • Journal of the Korea Concrete Institute
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    • v.16 no.5 s.83
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    • pp.651-657
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    • 2004
  • The effects of polymer-cement ratio, antifoamer content and shrinkage-reducing agent content on the air content, setting time, drying shrinkage and strength of high-fluidity polymer-modified mortars using redispersible polymer powder are examined. As a result, the air content of the polymer-modified mortars using redispersible polymer powder tends to decrease nth increasing polymer-cement ratio and antifoamer content. Regardless of the antifoamer content, the setting time of the polymer-modified mortars using redispersible polymer powder tends to delayed with increasing polymer-cement ratio. Irrespective of the antifoamer content, the drying shrinkage of the polymer-modified mortars using redispersible polymer powder tend to decrease with increasing polymer-cement ratio and shrinkage-reducing agent content. Regardless of the antifoamer content, the flexural and tensile strengths of the polymer-modified mortars using redispersible polymer powder tends to increase with increasing polymer-cement ratio, and tend to decrease with increasing shrinkage-reducing agent content. However, the compressive strength of the polymer-modified mortars using redispersible polymer powder decreases with increasing polymer-cement ratio and shrinkage-reducing agent content.

The Bond Characteristics of Ultra Rapid Hardening Mortar for Repair using Magnesia-Phosphate Cement (마그네시아 인산염 시멘트를 이용한 초속경 보수 모르타르의 접착특성)

  • Lee, Sun-Ho;Kwon, Hee-Sung;Paik, Min-Su;Ahn, Moo-Young;Lee, Young-Do;Jung, Sang-Jin
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.04a
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    • pp.609-612
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    • 2008
  • Ultra Super Early Strength Cement is a material that satisfies these requirements. early hydration heat however, is significant over regular concrete, thus discretion is advised for thermal cracks in accordance with heat generation when constructing a large-scale structures. In addition, the negative point that it is difficult to achieve required strength in a short period of time following rubbing process while retaining workability, the cement is being used conditionally for engineering material and Ultra Super Early Strength Cement for maintenance material for construction doesn't exist. Magnesia Phosphate Cement, which is currently under studies in overseas uses no extra admixture and has strong points of Ultra Super Early Strength as well as favorable construction-ability and adhesive stability to the prototype concrete. These factors stem recognition that it could be used as maintenance material for construction of diverse applicability. In order to provide necessary data to increase practicality of the magnesia phosphate cement for Ultra Super Early Strength Mortar, the study carried out simulate experiment on member of framework to review field applicability.

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Strengthening of concrete damaged by mechanical loading and elevated temperature

  • Ahmad, Hammad;Hameed, Rashid;Riaz, Muhammad Rizwan;Gillani, Asad Ali
    • Advances in concrete construction
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    • v.6 no.6
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    • pp.645-658
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    • 2018
  • Despite being one of the most abundantly used construction materials because of its exceptional properties, concrete is susceptible to deterioration and damage due to various factors particularly corrosion, improper loading, poor workmanship and design discrepancies, and as a result concrete structures require retrofitting and strengthening. In recent times, Fiber Reinforced Polymer (FRP) composites have substituted the conventional techniques of retrofitting and strengthening of damaged concrete. Most of the research studies related to concrete strengthening using FRP have been performed on undamaged test specimens. This contribution presents the results of an experimental study in which concrete specimens were damaged by mechanical loading and elevated temperature in laboratory prior to application of Carbon Fiber Reinforced Polymer (CFRP) sheets for strengthening. The test specimens prepared using concrete of target compressive strength of 28 MPa at 28 days were subjected to compressive and splitting tensile testing up to failure and the intact pieces of the failed specimens were collected for the purpose of repair. In order to induce damage as a result of elevated temperature, the concrete cylinders were subjected to $400^{\circ}C$ and $800^{\circ}C$ temperature for two hours duration. Concrete cylinders damaged under compressive and split tensile loads were re-cast using concrete and rich cement-sand mortar, respectively and then strengthened using CFRP wrap. Concrete cylinders damaged due to elevated temperature were also strengthened using CFRP wrap. Re-cast and strengthened concrete cylinders were tested in compression and splitting tension. The obtained results revealed that re-casting of specimens damaged by mechanical loadings using concrete & mortar, and then strengthened by single layer CFRP wrap exhibited strength even higher than their original values. In case of specimens damaged by elevated temperature, the results indicated that concrete strength is significantly dropped and strengthening using CFRP wrap made it possible to not only recover the lost strength but also resulted in concrete strength greater than the original value.

Studies on Damage Characteristics of Gyeongju Bunhwangsa Stone Brick Pagoda (경주 분황사 모전석탑의 손상 특성 연구)

  • Do, Jin Young;Kim, Jeong Jin
    • Journal of the Mineralogical Society of Korea
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    • v.31 no.3
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    • pp.149-159
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    • 2018
  • The Gyeongju Bunhwangsa Stone Brick Pagoda, which was built with bricks of andesite, is the oldest brick stone pagoda of Silla period. The damage patterns in the stone pagoda are pollutants such as white crust, black crust, discoloration, soil adsorption, and microorganisms, and repair materials. The damage pattern of structural factors in the Stone Brick Pagoda is a bulging phenomenon. According to the X-ray diffraction analysis, white crust are mainly consist of calcite ($CaCO_3$) and thermonatrite ($Na_2CO_3{\cdot}H_2O$) that evaporite finds in nature. Damage pattern varies depending on location of stone pagoda. The pollutants are first story body of pagoda. The microorganisms are confirmed at base, lion statues, first and second story capstone, and repair materials observed at base. The bulging phenomenon appeared on the first story body of the pagoda. Occupancy rates by damage type were higher in the order of microorganisms, pollutants, repair material, bulging phenomenon, and peeling. The highest percentage of individual damage patterns were black microorganisms (39.3%), followed by lichen (17.9%), discoloration (8.0%), white crust (5.5%), cement mortar (5.1%) and peeling (3.1%).

An Experimental Study on the Durability and Load Carrying Capacity of RC Structure Repair System Using FR-ECC (고인성 내화보수모르터(FR-ECC)를 활용한 RC 구조물 보수공법의 내구성능 및 내하력에 관한 실험적 연구)

  • Kim, Jeong Hee;Lim, Seung Chan;Kim, Jae Hwan;Kwon, Yung Jin
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.16 no.2
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    • pp.75-86
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    • 2012
  • This paper presents some research results on the shrinkage characteristics and frost resistance before and after cracking of FR-ECC(Fire Resistance-Engineered Cementitious Composite). Also, a waterstop performance and exfoliating resistance of multi-layer lining specimens using FR-ECC and flexural performance of beam member by repaired FR-ECC are estimated in this paper. Experimental results indicate that the plastic shrinkage crack and length change ratio of FR-ECC have been reduced as compared with that of the existing repair mortar, and that its crack resistance on the dry shrinkage is improved under the confining stress. As well as FR-ECC has been great in the frost resistance and its tensile properties under the cracked state have been not reduced by freezing and thawing reaction. In addition, beam member by repaired FR-ECC have been increased in the flexural properties such as initial crack moment, yeild moment, and its crack width has been controled in a stable by the frexural failure.

Adhesive Properties of High Flowable SBR-modified Mortar for Concrete Patching Material Dependent on Surface Water Ratio of Concrete Substrate (콘크리트 피착체의 표면수율에 따른 단면복구용 고유동성 SBR 개질 모르타르의 부착특성)

  • Do, Jeong Yun;Kim, Doo Kie
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.17 no.2
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    • pp.124-134
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    • 2013
  • This study investigated the effect of surface water on concrete substrate on adhesive strength in tension of very high flowable SBR-modified cement mortar. The specimens were prepared with proportionally mixing SBR latex, ordinary portland cement, silica sand, superplasticizer and viscosity enhancing agent. Polymer cement ratio (P/C) were 10, 20, 30, 50 and 75% and the weight ratio of fine aggregate to cement were 1:1 and 1:3. The specimens obtained with different P/C and C:F were characterized by unit weight, flow test, crack resistance and adhesion test. After basic tests, two mixtures of P/C=20% and 30% in case of C:F=1:1, and one mixture of P/C=50% in case of C:F=1:3 were selected, respectively. These three selected specimens were studied about the effect of surface water evenly sprayed on concrete substrate by a amount of 0, 0.006, 0.012, 0.017, 0.024g per unit area ($cm^2$) of concrete substrate surface The results show that surface water on concrete substrate increases the adhesive strength in tension of high flowable SBR-modified cement mortar and improve the flowability compared to the non-sprayed case.

A Study on the Fundamental Properties of Ultra Rapid Hardening Mortar using Coal-Ash (잔골재 대체재로서 석탄회를 이용한 초속경 보수모르타르의 기초적 특성에 관한 연구)

  • Lee, Gun-Cheol;Oh, Dong-Uk;Kim, Young-Geun;Cho, Chung-Ki
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.6 no.1
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    • pp.128-135
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    • 2011
  • In this study, in order to develop ultra rapid hardening mortar(URHM) for tunnel repairs using bottom ash of low recycle ratio and Admixture as Eco concept, fundamental properties of URHM on temperature condition of construction field were performed. Test result, URHM of three types for fluidity and setting time were as in the following : B > C > A. Those for low temperatures were later than the standard condition. Compressive, bending and bond strength were similar with three types as follow. In compressive strength, initial strength of the low were smaller than the standard but the low in the long-term were similar with the standard. On the contrary to this, bending strength were similar in initial strength but the low in the long-term were smaller than the standard. The low in bond strength was average 35% less than the standard. Length changes was as in the following : A > C > B. the low is two times much as the standard but the case using blast furnace slag particles noticeably reduced length changes. Water absorption coefficient and water vapor resistance were as in the following : C > A > B. In case of URHM added bottom ash, water absorption coefficient and water vapor resistance were increased because bottom ash is porous material.

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Effect of Substrate Surface Water on Adhesive Properties of High Flowable VA/VeoVa-modified Cement Mortar for Concrete Patching Material (단면수복용 고유동성 VA/VeoVa 개질 시멘트 모르타르의 부착특성에 대한 피착면 표면수의 영향)

  • Do, Jeong-Yun;Kim, Doo-Kie
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.17 no.5
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    • pp.94-104
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    • 2013
  • Experiments were divided into two parts; one part is to understand the basic properties of high flowable VA/VeoVa-modified cement mortar with different polymer cement ratio (P/C) and the weight ratio of fine aggregate to cement (C:F) and the other part is to investigate the effect of surface water spread on the concrete substrate on adhesion in tension. To understand the basic performance, the specimens were prepared with proportionally mixing VA/VeoVa redispersible powder, ordinary portland cement, silica sand, superplasticizer and viscosity enhancing agent. Here, P/C were 10, 20, 30, 50 and 75% and C:F were 1:1 and 1:3. As the change of P/C and C:F unit weight, flow test, crack resistance and adhesion in tension were measured. Three specimens with good adhesion properties were selected among specimens with different P/C and C:F. The effect of surface water evenly sprayed on concrete substrate on adhesive strength is investigated. The results show that surface water on concrete substrate increases the adhesion in tension of high flowable VA/VeoVa-modified cement mortar and additionally improves the flowability compared to the non-sprayed case.

Study on Adhesive Strength of Polymer Modified Cement Mortar for Maintenance in Concrete Structure (콘크리트 구조물 보수용 폴리머시멘트 모르타르의 부착강도 특성에 관한 연구)

  • Park, Sang-Soon;Kim, Jung-Heum
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.14 no.5
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    • pp.128-135
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    • 2010
  • Polymer-modified cement mortar(PCM) has been widely used for strengthening of the concrete structures due to its excellent physical properties such as high strength and durability. Adhesive strength or behavior, on the other hands, between PCM and concrete is very important in strengthening the concrete member using PCM. Therefore the adhesive failure mechanism between PCM and concrete should be fully verified and understood. This study was performed to evaluate adhesive strength of PCM to the concrete by the direct pull-out test. In the direct pull-out tests, the adhesive strength under the various pre-treatment conditions such as immersion, thunder shower, freezing and thawing are evaluated. Also, the field direct pull-out test are performed to investigate the adhesive strength of mock-up test specimens. In the results of the test, the adhesive strength value by field test are lower than those of the standard curing condition. From these comparison and investigation, field test result was similar with the thunder shower test result. The results of the test was used to evaluate the korean industrial standard of polymer modified cement mortars for maintenance in concrete.