초고층 건축물용 80 MPa급 고성능 콘크리트의 펌프압송에 따른 공학적 특성

다국어 초록 (Multilingual Abstract)

Recently, high rise buildings have been constructed with the trends of pursuing high rise and enlargement, so pump car placement is being generally applied in terms of workability and economic feasibility as the most excellent placement method. However, the high strength concrete used to construct super high-rise buildings are expected to raise various problems at the pumping of high pressure; therefore, a lot of researchers have conducted a series of tests related to the pumping in diverse ways and reported the findings so far. However, the results are so different from one another, and most of them deal with the tests on horizontal pumping performances only.
Accordingly, this study aims to consider the actual pumping performances of the vertical pipe. To attain the goal, the researcher selected super high-rise building projects in which the vertical height of the pumping was higher than 500 m. According to the vertical height of the pumping of 80 MPa high performance concrete placed, the study intends to analyze the quality fluctuations of the concrete before and after the pumping and also evaluate its rheological properties.

(1) According to the result of analyzing the fluid properties of the concrete unhardened before and after the pumping by the height of it, its slump flow, slump, and air quantity and temperature tended to increase more compared with those before the pumping. However, T-500 showed reduction after the pumping. Also, the content of chlorides measured indicated subtle difference before and after the pumping. And according to the result of evaluating the segregation of the concrete quantitatively based on the Evaluation Index for Segregation (EIS), the EIS value ranged from 2.2 to 2.4, so in terms of its performance, it indicated the excellent index reaching either the 1st or 2nd grade.

(2) Regarding the result of evaluating the filling through the V-lot time of flow and the U-Box filling test before and after the pumping by the height of it, the result of the V-lot time of flow test showed that the decrement of viscosity led to the reduction of time of about 45 %. And the result of the U-Box filling test showed that there was no significant difference before and after the pumping and both satisfied the range of the site management itself.

(3) The concrete’s yield stress and plastic viscosity were quantitatively evaluated by using the related equipment. And both its yield stress and plastic viscosity were significantly reduced up to 50% or so after the pumping due to the reduction of the concrete’s viscosity. Also, its yield stress and plastic viscosity were compared with quantitative evaluation as well as philological evaluation, and both showed that they had low correlation of about 10 to 30 %.

(4) According to the result of measuring the concrete’s compressive strength and elastic coefficient by age before and after the pumping based on the height of it, one of the dynamic properties, the 7th day showed about 14 %, the 28th day about 8 %, and the 56th day about 10 %; therefore, as the age gets higher, it tends to increase comparatively more after the pumping in general. And the elastic coefficient, too, tends to increase as the compressive strength increases.