In the CALIBE national project carried out in France from 1995 to 1999, one of the goals was to develop special devices in order to better control concrete pumping. An experimental 150-m (500 ft.) pumping network with twelve elbows was installed, in which more than 50 concrete compositions were pumped. The flow rate and the pressure in the concrete vs. length were measured during each test. It was found that the pressure vs. length patterns were always linear, which is experimental evidence of the validity of the equation in the previous section. Moreover, the rheological parameters measured with the BTRHEOM rheometer and the interface parameters assessed with a large-gap coaxial viscometer were used to predict the relationship between pressure and flow rate, accounting for the total length and diameter of the pipes. The agreement between a calculation and experiment was found to be very satisfactory (see Figure 11). In addition, it was found that elbows play a negligible role in the pressure losses, but are only important to the extent to which they may facilitate blockage.
Figure 11: Comparison between experiments and theory from the CALIBE pumping tests [51]. NSC: normal-strength concrete (w/c = 0.53, slump = 190 mm); HPC: high-performance concrete (w/c = 0.33, slump = 240 mm); SCC: self-compacting concrete (w/c = 0.25, slump = 270 mm); Air-Entrained Mixture: 10 % air (w/c = 0.40, slump = 110 mm).