• Computers and Concrete
• /
• 제18권5호
• /
• pp.951-968
• /
• 2016

In this study, pullout capacities of post-installed deformed bars anchored in low strength concrete using different bonding materials are investigated experimentally. The experimental study was conducted under outdoor and indoor conditions; on the beams of an actual reinforced concrete building and on concrete bases constructed at Istanbul Technical University (ITU). Ready-mixed cement based anchorage mortar with modified polymers (M1), ordinary cement with modified polymer admixture (M2), and epoxy based anchorage mortar with two components (E) were used as bonding material. Furthermore, test results are compared with the predictions of current analytical models. Findings of the study showed that properly designed cement based mortars can be efficiently used for anchoring deformed bars in low quality concrete. It is important to note that the cost of cement based mortar is much lower with respect to conventional epoxy based anchorage materials.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
• /
• pp.11-14
• /
• 2003

The purpose of this paper is to offer a base data of specification, so that the strength information of concrete in the structure for irrigation can be rationally determined the coefficient of variation of an existing irrigation structure and the best fit the ready-mixed concrete strength to specified strength $f_ck$. From analysis of concrete cylinders from about 30 numbers in southern Korea, it was concluded that the coefficient of variation of cylinder strength were approximately 5.9%. On the basis of the core strength test data, it was appeared that the average coefficient of variation for the existing irrigation structure can be taken as 17.8% for strength level 21MPa.

• 한국농공학회논문집
• /
• 제60권3호
• /
• pp.123-133
• /
• 2018

The purpose of this paper is to propose an experimental method to evaluate the resistance of abrasion about 24 MPa, 27 MPa, and 30 MPa compressive strength. These strength are used in the design and construction of concrete hydraulic structures in Korea. The mixing ratios of the ready mixed concrete strengths were investigated countrywide and set the representative mixture proportion ratios of the nine mixed types of OPC, FA and BFS. After making and curing the test specimens, the underwater abrasion test was performed. ASTM C 1138 International Standard was used to fabricate the test equipment, and the surface abrasion resistance of the specimen was tested using the test equipment. In the case of OPC, the 30% abrasion resistance improvement effect was observed at 72 hours as the water-binder ratio decreased. That was reason the coated cement bond strength of the specimen was strong. In the case of BFS and FA, it was improved by 9.9% and 3.8%, respectively, at 72 hours as the water-binder ratio decreased. It was due to the characteristics of the latent hydraulic and pozzolanic reactions. Generally, the relative abrasion resistance of concrete can be evaluated at 24 hours. However, in case of low strength (under 24 MPa), the surface mortar layer wears much faster at the first 12 hours, so it can be considered to evaluate the relative abrasion loss rate at this point.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
• /
• pp.465-468
• /
• 2008

본 연구는 영, 호남 지역의 레미콘 공장에서 현재 사용하고 있는 잔골재의 특성을 분석하고, 혼합사용 시 잔골재율 조정에 따른 콘크리트의 특성실험을 통하여 혼합사용 시 최적조건을 분석한 것으로 그 결과를 요약하면 다음과 같다. 영, 호남에서 사용하는 골재 종류별 물성은 조립률 및 0.08mm체 통과량을 제외하고 모두 KS F 2526 및 KS F 2527의 규정에 적합한 것으로 나타났는데, 각 공장에서는 단독사용이 부적합한 골재를 2종 이상 적절한 비율로 혼합사용하고, KS규정에 적합하게 품질을 관리하고 있었다. 영, 호남 각 공장에서 단위용적질량법에 의해 산출한 잔골재율로 조정한 콘크리트의 배합은 기존의 출하배합보다 높은 유동성을 보이는 것으로 나타났는데, 이는 잔골재율 약 2% 저감에 따라 잔골재의 표면적 감소 및 공극감소에 따른 시멘트 페이스트의 유동성에 미치는 잉여수량의 상대적 증가에 기인한 것으로 분석된다. 따라서 최적 잔골재율을 적용함으로써 단위수량 감소로 인한 경제적인 콘크리트 배합과 콘크리트의 내구성을 증진시키는 효과가 있을 것이라 사료된다.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2015년도 추계 학술논문 발표대회
• /
• pp.105-106
• /
• 2015

With an increase of concrete buildings as result of rapid industrialization, Remicon sludge, which is a strong alkaline construction waste, should be neutralized to prevent damage to a natural environment, and the cost of the neutralization processing is increasing as well. Accordingly, this study investigates the mechanical properties of cementless concrete which is processed with recycled water and industrial byproducts in order to determine the possibility of re-using sludge, recycled sand, and gravel which are contained in recycled water.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1995년도 봄 학술발표회 논문집
• /
• pp.18-21
• /
• 1995

Continued from study on fresh concrete properties of the part 1, this study is designed for analyzing to the increasing trend of the compressive strength according to the curing method, standard deviation, strength properties of pumping before and after, and a length change to the drying shrinkage. And for quality control, this study is designed for analyzing the early estimation of compressive strength by hydrometer method in diluted concrete solution at the fresh state, and non-destructive testing by the Schumidt hammer at the hardened state.

• Computers and Concrete
• /
• 제25권1호
• /
• pp.59-65
• /
• 2020

The premise for the study reflected in this article is the need to dispose of industrial waste, which is increasingly being used in the construction materials industry. Also, dynamically developing building industry demands attention of scientists and a direction of their works on improvement of the technology of carrying out construction works. Thus, the article is devoted to studying the influence of various chemical additives and fine fillers (industrial wastes) available in Kazakhstan on self-compacting concrete (SCC) mixtures and its rheological, physical, and technical properties. According to the studies, revealed the most efficient type of fine-dispersed filler and the most optimal type of chemical additive to enable obtaining a high-quality SCC mixture based on local raw materials. As a result, the use of microsilica in comparison with other industrial wastes resulted in a conglomerate with high compressive strength of SCC at early terms of curing. In terms of economic efficiency and quality improvement, the results of study are of practical value for the manufacturers of ready-mixed concrete operating in Kazakhstan.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
• /
• pp.53-56
• /
• 2000

The performance of high-strength concrete is controlled by the fact, affecting the quality management, especially by revision error in water content of the ratio of surface moisture in fine aggregate. The difference in water content results from the revision error of the ratio of surface moisture and errors in sampled aggregate in the processing ready-mixed concrete plant. This study is to investigate the properties of flowing and hardening by investionally varying the revision error of the ratio of surface moisture in fine aggregate to compare and analyze the variance in quality.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2013년도 추계 학술논문 발표대회
• /
• pp.19-20
• /
• 2013

Consider about aggregate's price, coarse aggregates from 13 to 25mm were widely used in ready mixed concrete company. But if only use 13 to 25mm aggregates in the concrete, gap grading problem would be occurred. When recycled aggregates from 13 to 25mm was used, continuous grading would increase the durability and strength for the concrete, meanwhile the construction waste materials would also be reused. In this paper, 5-13mm recycled aggregates was utilized, to analyse the fundamental properties for concrete, strength has been tested to evaluate the quality and reusing effect of the recycled materials.

• 콘크리트학회논문집
• /
• 제24권3호
• /
• pp.333-340
• /
• 2012

경량골재 콘크리트의 압축강도에 대한 크기 및 형상효과를 평가하기 위하여 9 배합의 실내 실험과 3 배합의 레미콘 배합을 수행하였다. 콘크리트 배합은 보통중량, 전경량 및 모래경량의 3그룹으로 분류되었다. 각 콘크리트 배합에서 원형 또는 사각형 단면을 갖는 시험체의 형상비는 1.0과 2.0이었다. 시험체의 단면 크기는 각 실내배합에서는 50~150mm, 각 레미콘 배합에서는 50~400mm 범위에 있었다. 실험 결과 경량골재 콘크리트의 균열진전과 국부 파괴영역은 보통중량 콘크리트와 상당히 달랐다. 경량골재 콘크리트에서 균열은 골재를 관통하였으며, 균열의 분포영역은 매우 국부적이었다. 이로 인해, 경량골재 콘크리트의 크기효과는 보통중량 콘크리트에 비해 더 크게 나타났으며, 이 현상은 형상비 1.0보다는 2.0인 시험체에서 더 뚜렷하게 나타났다. 김진근 등의 크기효과 예측모델은 경량골재 콘크리트에서 시험체 단면크기가 150mm 이상일 때 과대 평가하였다. 반면, 압축강도에 대한 시험체 형상의 영향을 보정하기 위해 ASTM 및 CEB-FIP에서 제시한 수정계수는 경량골재 콘크리트에서도 안전측에 있었다.