• International Journal of Concrete Structures and Materials
• /
• 제8권4호
• /
• pp.269-278
• /
• 2014

When concrete is being transported through a pipe, the lubrication layer is formed at the interface between concrete and the pipe wall and is the major factor facilitating concrete pumping. A possible mechanism that illustrates to the formation of the layer is the shear-induced particle migration and determining the rheological parameters is a paramount factor to simulate the concrete flow in pipe. In this study, numerical simulations considering various rheological models in the shear-induced particle migration were conducted and compared with 170 m full-scale pumping tests. It was found that the multimodal viscosity model representing concrete as a three-phase suspension consisting of cement paste, sand and gravel can accurately simulate the lubrication layer. Moreover, considering the particle shape effects of concrete constituents with increased intrinsic viscosity can more exactly predict the pipe flow of pumped concrete.

• Advances in concrete construction
• /
• 제13권5호
• /
• pp.395-410
• /
• 2022

This study collected the results of material tests and full-scale pumping tests using 127 types of concrete mixtures with compressive strength ranging from 24 to 200 MPa. The results of 242 material tests showed high correlations between the viscosity of the lubricating layer and concrete, between the slump and the yield stress of concrete, between the water-binder ratio and the viscosity of lubricating layer, and between the time required to reach 500 mm of slump flow and concrete viscosity. Based on these correlations, pumpability was predicted using 101 pumping test conditions, and their accuracy was compared to the actual test results. When the rheological properties of concrete and the lubricating layer were directly measured, the prediction result showed the highest accuracy. A high accuracy can be achieved when the measured viscosity of the lubricating layer, a key determinant of concrete pumpability, is reflected in the prediction of pumpability. When measuring rheological properties is difficult, the slump test can be used to quantitatively predict the pumpability despite the lower accuracy than those of other prediction methods.

• Advances in concrete construction
• /
• 제16권1호
• /
• pp.59-68
• /
• 2023

In the pumping process, concrete moves along the pipe and experiences both pressure and shear. This changes the workability and flow characteristics of the concrete. However, the effect of pressure and shear on the change in properties of concrete during the pumping process has not yet been accurately identified. This study analyzed the effects of pressure and shear on the properties of concrete during pumping. For quantitative tests, lab-scale test equipment capable of simulating the pressure and shear applied to concrete during pumping was used. For one coarse aggregate type, two paste types, three mortar types, and five concrete types, the effects of pressure, shear, and shear under pressure conditions were examined by varying the maximum pressure (0 to 200 bar) and the rotational speed of the vane for shear (0 to 180 rpm). Under the maximum pressure condition of 200 bar, the water absorption of coarse aggregate increased by 0.62% and that of fine aggregate also increased. When the concrete was under pressure, significant changes (a reduction in a slump and an increase in viscosity and yield stress) compared with the effect of the elapsed time occurred owing to an increase in the water absorption of the aggregates. When both pressure and shear were applied to concrete, both the slump and viscosity decreased. As the rotational speed of the vane increased, changes in properties became significant. Shearing in the absence of pressure maintained the properties of concrete. However, shearing under pressure conditions caused a reduction in slump and viscosity.

• 한국산학기술학회논문지
• /
• 제16권2호
• /
• pp.1364-1369
• /
• 2015

반도체 칩의 고집적화로 과거 와이어 본딩 공정에서 BUMP 공정으로 전환되면서 반도체칩과 외부 기기로 이어지는 통신선도 더욱 미세해짐으로 인해 보다 정밀한 작업이 필요한 실정이지만 PSPI의 고점도 특성상 정량제어가 어렵고 버블유입에 따른 수율의 저하가 계속되고 있는 실정이다. 따라서 본 논문에서는 반도체 BUMP 공정에서 고점도 감광성 폴리이미드(PSPI : Photosensitive Polyimide)의 도포(coating)시 발생하는 기포(gas)를 제거하여 공급하는 D&P(Degassing and Pumping) 시스템을 개발하였다.

• Advances in concrete construction
• /
• 제6권5호
• /
• pp.465-483
• /
• 2018

The most crucial factor determining the pumping performance of concrete is the characteristics of the lubricating layer formed between the pipe wall and the inner concrete. Thus, it is important to accurately identify the rheological properties of the lubricating layer to predict the pumping of concrete. In this study, a new method is proposed for measuring the rheological properties of the lubricating layer with improved convenience. To verify the new method, a pumping test was conducted with 337 m-long horizontal piping. The rheological properties of the lubricating layer were assessed by a previously verified method and the new method proposed in this study for a total of four concrete mixtures with design strength ranging from 27 MPa to 60 MPa. The correlation between the existing method and the new method in relation to the viscosity of the lubricating layer was determined, and it was possible to predict the pumping performance with an accuracy of about 88.5% using the viscosity of the lubricating layer obtained from this correlation.

• 한국건축시공학회지
• /
• 제11권4호
• /
• pp.387-395
• /
• 2011

In the construction of tall-building, concrete pumping influences the success of the project. In order to establish pumping technology for high speed construction of tall building, study for quantitative evaluation of flow characteristics and pumpability should be conducted. So in this study, the characteristics including the inner pipe pressure, rheological properties of concrete and mortar through the continuous pumping test were evaluated. Then we analyzed the relations between rheological properties and pumpability. In the result of test, there are high correlations between the rheological characteristics which represented by yield stress and plastic viscosity and pressure loss with pipe length. Also, we estimated pressure loss according to conditions of concrete mix and pumping through the evaluation of inner pipe friction.

• 한국윤활학회:학술대회논문집
• /
• 한국윤활학회 1999년도 제29회 춘계학술대회
• /
• pp.359-365
• /
• 1999

We have evaluated the performance and some physical properties of 25 automotive engine oils (21 domestic and 5 imported products) which are purchased on the market to verify the API(American Petroleum Institute) or ILSAC(International Lubricant Standardization and Approval Committee) certification marks attached on the products and to determine the necessity of the quality control of the engine oils on the market. 12 test items are chosen according to API engine oil specification, which are flash point, pour point, cold cranking simulator apparent viscosity, pumping viscosity, gelation index, HTHS(High Temperature High Shear viscosity), foam, high temperature foam, filterability, volatility, high temperature deposit(TEOST), phosphorus content. We have found one product which did not meet the API specification on gelation index, one on HTHS, four on foam, and one on volatility, which implies that the quality control system is in need to check the fidelity of the certification marks attached on the engine oils being marketed. In addition, this works raises the necessity of the upgrade of the present Korean engine oil specification.

• 대한설비공학회지:설비저널
• /
• 제4권4호
• /
• pp.303-308
• /
• 1975

• 대한설비공학회지:설비저널
• /
• 제5권1호
• /
• pp.25-28
• /
• 1976

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2011년도 춘계 학술논문 발표대회 1부
• /
• pp.99-101
• /
• 2011

In order to have pumping technology for high speed construction of tall building, study for quantitative evaluation of flow characteristics and pumpability should be conducted. So, this study evaluate the characteristics among the inner pipe pressure, fresh concrete properties and separated mortar through the continuous pumping test. Then it consider of relations between rheological properties and pumpability. In the result of test, it found that there are high interrelationship between the rheological characteristics which represented plastic viscosity and pressure lose by pipe length.