There are not enough models or guidelines suitable for the estimation of pumpability in high-strength concrete used for high-rise building construction. Therefore, many difficulties arises from the planning stage in high-rise building construction. Since more accurate prediction in pumpability can minimize problems in such application, this study aims to develop a model using a friction factor for estimation of the pumpability in high-strength concrete used for high-rise building construction. In order to achieve the main objective of this study, a mix design suitable for high strength concrete, satisfying the target of 600 mm slump flow, was first established.
The changes in the friction factor were monitored through pumping tests in both horizontal and vertical pipelines. The results were then used for multiple regression analyses to derive a model that can estimate the friction factor. Finally, the estimated results from derived model were compared and verified by experimental results. According to the results in this study, following conclusions can be drawn.
1) It was found that the unit weight of concrete was affected by the pumping pressure. The friction factor was changed as a result.
2) The friction factor was also changed by water to binder ratio. A high viscosity in low W/B and higher amount of binder was found to affect the pumping performance.
3) From the pumping tests in horizontal pipeline, the measured maximum pumping pressures were all above the 100 bar. It is considered that the length of horizontal pipeline should be elongated if the results from horizontal pipeline are used for the prediction of pumpability in vertical pipeline.
4) According to the multiple regression analyses using data such as w/b and pumping pressure, a model for estimation of the friction was driven as follows: ln (y) = 3.687 + 0.002 × X1 - 0.092 × X2 where, y is the friction factor, X1 is the pumping pressure, and X2 is the water to binder ratio(%).
5) The discharge rate of concrete per hour was estimated using a derived model. The estimated results were similar to the experimental results from 40, 50, 60 MPa concrete in vertical pipeline tests. The level of accuracy between estimated and measured data was less than 10 % in standard deviation.
6) Using high strength concrete with water to binder ratio of 0.37, the pumping test were performed at pumping height of 300m. The variation in data from estimated and measured data showed the difference of only 1.91%. The result indicates that the friction factor model can be successfully utilized for similar construction purposes.
Considering the changes in water to binder ratio and pumping pressure, the friction factor was successfully estimated. The use of friction factor can eventually bring more accuracy than using current guidelines or models for predicting the pumpability of high-strength concrete.