In this study, cement mortar (KS F 4042) used for repairing concrete structures was evaluated for compressive strength and bond strength according to the mixing ratio of polymer. From the experimental results, it was confirmed that as the polymer content increases, the bond strength properties increase, but the compressive strength decreases slightly at a certain rate.

This study examined the safety and reliability of code equations for the bond strength of FRP bars with concrete using test data compiled from the different sources. ACI equations have a better agreement with test results, whereas high overestimation is observed in JSCE equations.

This research developed the fiber pullout impact test machine to investigate interfacial bond strength between fiber and cement based matrix under high velocity. To achieve the goal, firstly the existing pullout test machines were investigated. And then, these drawback were comprehended. Finally, Fiber pullout impact test machine base on strain energy frame impact machine was proposed.

The maximum bond strength of PCS-coated rebar with ultra high-early strength cement and EVA at polymer-cement ratio of 80%, curing ages of 7-day, and coating thickness of 100㎛ is about 1.32 and 1.38 times respectively, the strength of uncoated rebar and epoxy-coated rebar. It is also high bond strength at coating thicknesses of 75㎛ and 100㎛ compared with 150㎛ and 250㎛. It is apparent in this study that the coating thickness is very important factors to improve the bond strength of PCS-coated rebar to cement concrete.

Characteristics of bond strength between AR-glass textile and fine concrete was performed through pull-out test with various transverse reinforced methods as number of lateral reinforced textile and transverse development length. In the both case of change in reinforcing method, bond strength was increased sharply in the first case.

In this study, cement mortar (KS F 4042) used for repairing concrete structures was evaluated for compressive strength and bond strength according to the mixing ratio of polymer. From the experimental results, it was confirmed that as the polymer content increases, the bond strength properties increase, but the compressive strength decreases slightly at a certain rate.

시멘트 생산 과정에서 생성되는 이산화탄소 배출량을 감소시키기 위하여 시멘트를 대체할 수 있는 건축 재료 개발에 많은 연구가 진행되어왔다. 시멘트 대체재로 사용될 수 있는 활성 황토는 850°C에서 소성 과정을 거쳐 제작된다. Poly-Vinyl Alcohol(PVA) 섬유와 GFRP 보강근은 활성 황토 콘크리트의 균열 문제를 해결하기 위하여 사용된다. 본 논문은 PVA 섬유 보강 활성 황토 콘크리트에 대하여 인발 하중에 따른 GFRP 보강근의 부착 성능을 평가하기 위한 실험 연구를 나타내고 있다. 실험 결과, 황토가 치환된 PVA 보강 및 무보강 실험체들의 평균 부착 응력 계수가 2.27~2.48로 나타났으며, 부착 응력 계수가 PVA 섬유 보강 유무 및 황토 치환율에 크게 영향을 받지 않는 것으로 나타났다. 그리고 부착 길이가 길어질수록 부착 강도는 저하되었다.

본 논문은 바탕면의 함수조건에 따른 보수재료로서 MKPC의 인발 부착강도, 전단 부착강도, 계면 부착강도를 폴리머 시멘트 모르 타르, 에폭시 모르타르와 비교 분석하였다. 그 결과 MKPC는 PC 및 MKPC와 비교하여 바탕면 함수조건에 따른 부착성능의 변화가 상대적으 로 작은 것으로 나타났다. 또한 MKPC의 경우 절건 바탕면에서의 부착성능은 무기계 보수재료인 폴리머 시멘트 모르타르와 비교하여 우수한 특성을 지니고 있으며, 습윤 바탕면에서의 부착성능은 폴리머 시멘트 모르타르와 유사한 수준을 보이고 있으나 에폭시 모르타르와 비교하여 우수한 특성을 지니는 것으로 나타났다.

이 연구에서는 고연성과 낮은 탄성계수를 갖는 PET 섬유로 보강한 철근콘크리트 보의 부착특성과 휨거동을 각각 부착실험 및 휨실 험을 통하여 규명하고자 하였다. 부착실험은 CSA S806에 따라 수행하였고, 실험변수는 섬유 종류와 보강량(CF 및 GF 시트 각 1겹, PET 시트 10겹)이었다. 총 8개의 보 실험에서 주요 실험변수는 단면의 연성비(μ = 3.4, 7.0), 보강섬유 종류(CF, GF, PET) 및 보강량이었다. 보 단면의 모 멘트-곡율 해석을 병행하였다. 부착실험의 결과, CF, GF 시트 1겹 보강에서 유효 부착길이는 각각 120, 60 mm 이었고 최대부착응력은 각각 3.25, 2.99 MPa 이었다. PET 10겹 보강에서 유효 부착길이는 60 mm, 최대 및 평균 부착응력은 각각 2.30, 2.10 MPa 이었다. 또한 최대 강도 시 CF, GF, PET의 변형율은 각각 0.36%, 0.49%, 6.29% 였으며 CF, GF 부착실험체는 계면에서 시트가 최종적으로 탈락하였지만 PET 부착 실험 체에서 박리현상은 나타나지 않았다. 휨실험의 결과, PET 10, 20, 30겹으로 보강한 RC 보의 휨강도, 휨강성이 모두 무보강 보에 비해 증가하였 고, 연성적인 휨파괴 양상을 보였으나 PET 30겹의 경우 20겹에 비하여 연성이 감소하였다. 모멘트-곡율 해석의 결과, PET 보강 보에서 접착제 의 물성을 해석에 포함시키면 해석의 정확도가 향상하였다. 한편 PET 의 내구성에 대해서는 보고된 문헌이 없어서 현재 연구 진행 중이다.

Change in the adhesion strength between AR-glass textile and concrete was performed through pull-out test with longitudinal (load direction) and transverse development length. In case of longitudinal development length, adhesion performance was not shown. But in case of transverse, adhesion performance was increased according to the increasing transverse textile length.

Recently, Advanced water treatment facilities with Ozone are being introduced domestically. However, waterproofing/corrosion prevention construction method of concrete structure for existing advanced water treatment makes waterproofing/corrosion prevention materials and concrete deteriorated because of strong oxidation of ozone. Therefore, in this study, It was evaluated in ozone resistance and bond strength of metal spraying coating.

Result of test, adhesive strength improved 7% in 4℃ when test object used vibrating roller than unused vibrating roller. In case of 20℃, it improved 16.9%. Therefore, using vibrating roller is useful in construction of waterproofing layer because the test showed that using vibrating roller has excellent adhesive strength han unused it.

According to social needs, eco-friendly material for concrete structures has been developed in recent years. Hwang-toh is one of the eco-friendly architectural material and hwang-toh has been used by partial or complete replacement of portland cement. Pullout tests on deformed steel reinforcing bars with non-activated hwangtoh concrete are conducted in this paper. Experimental results, average bond strength of non-activated hwangtoh concrete was appeared to 7.3 MPa.

This paper describes pullout tests on deformed steel reinforcing bars with PVA fiber-reinforced activated hwangtoh concrete (PFRC). Four pullout specimens with the variation of the replacement ratio of PFRC to cement are prepared and test. Experimental results, average bond strength of PFRC was appeared to 19.81. MPa.

This is A Study on the Bond Performance of Synthetic Polymer Composite Waterproofing and Anticorrosion Method in accordance with PE Fiber Reinforcement. Test results, A Bond Performance of the Test Specimen was confirmed to have increased 37.5%. By PE Fiber Reinforcement.

This study examines whether Korean rating agencies such as Korea Investors Service (KIS), National Information & Credit Evaluation (NICE), and Korea Ratings Corporation (KR), incorporate corporate governance into their corporate bond ratings in Korea. We find that the Korean rating agencies assign higher ratings to the bonds issued by Chaebol (Korean business group) affiliated firms. Our results also indicate that those rating agencies give higher ratings to the bonds with greater foreign investor share ownership. Moreover, if the rating agencies value corporate governance, higher rated firms should issue bonds at lower yield to maturity. We discover that Chaebol affiliation is counted favorably by the rating agencies. We find that investors are willing to pay lower risk premium for bonds with higher institutional ownership, but higher risk premium to bonds with greater equity ownership in the form of depository receipts. Therefore, even if the rating agencies and investors in Korea consider corporate governance (Chaebol affiliation and ownership structure) an important determinant in bond ratings and the yields to maturity, they have opposite views on institutional ownership and share ownership in the form of depository receipts

The purpose of this paper is to evaluate bond capacity of steel fiber reinforced concrete. Test variables were compressive strength of concrete and steel bar diameter and a total of six specimens in order to examine the discrepancy in bond resistance due to each variable. The specimens were tested by using universal testing machine in displacement control mode. From the test results, it can be seen that the bond strength increased with increasing diameter of steel bar for the same compressive strength of concrete. Also, the higher strength concrete is, the higher bond strength can be found in the test. Significant slip resistance inducing greater bond strength can be observed in the specimens with large diameter steel bar. All the specimens failed in splitting failure after its maximum load and compressive stress of concrete predominated in bond capacity.

Concrete and bar of bond performance used in the most RC structure. So Through recent studies and experiments for the attachment behavior of concrete and steel issues and evaluate their characteristics. Bar are two was used as the D13 and D16. The Bond stress was increased result of experiment by placing a variable length according to the Bond stress formulation according to the diameter and reinforced.

본 연구는 고강도 섬유보강 시멘트 복합체(UHSCC) 접착성능을 평가하는 것이 목적이다. Direct shear test를 통해 압축전단접착강 도를 측정한 결과 NC(보통강도콘크리트)+ NC 실험체(150×150×150)에서는 모든 수준에서 유사한 압축전당접착강도를 나타내었고, 반 면 UHSCC+UHSCC에서는 지연타설 30분 후부터 0분에 비해 압축전단접착강도가 낮아지는 것을 확인할 수 있었다. 이를 통한 접착면의 파괴 모드를 분석한 결과 NC+NC 에서는 모든 수준에서 비계면 파괴를 보였고 UHSCC+UHSCC에서는 30분, 60분, 90분 시험체에서 계면파괴가 일 어났다. NC 및 UHSCC의 타설면을 XRD 시험을 통해 분석한 결과 NC 시험체에 비해 UHSCC의 시험체 에서 많은량의 SiO2의 성분이 검출되 는 것을 알 수 있었고 UHSCC에서 나타난 코팅막의 주성분의 대부분은 SiO2로 사료된다. 따라서 본 연구에서 사용된 UHSCC는 지연타설 30분 후 부터는 접착성능의 저하로 구조체로서의 사용이 어렵다고 판단된다. 금후 연구에서는 콜드조인트 발생 부위의 면처리 방법을 통한 접착성 능 향상이 필요하다고 사료된다.

FRP(Fiber Reinforced Polymer) reinforced lightweight concrete structures can offer corrosion resistance and weight reduction effect simultaneously, so practical use of the structures may be expected afterwards. During that time, a lot of studies for bond behaviors of FRP bar in normal concrete were conducted, but studies for bond behavior of the FRP bar in lightweight concrete are very limited to date. So, bond characteristic between lightweight concrete and helically deformed GFRP bar was investigated in the former study by the authors. In this study, re-consideration of the bond capacity were performed by using results of the former study, results from additional experiment considering variation of the concrete compressive strength, and results from literature survey.