H. Li, D. Sun, Z. Wang, F. Huang, Z. Yi, Z. Yang and Y. Zhang / Journal of Advanced Concrete Technology Vol. 18, 352-363, 2020 354 under the shear action during pumping. In the process of concrete pumping, migration of the sands (fine particles) is ignorable as
11/4/2020 · Many studies have been performed to predict pumping pressures of concrete, whether through the use of interface rheometers [1,3–7], the Sliper [8–11], or by measuring the rheology of concrete and its constituent (micro-) mortar [12–14].
measure 1 point. Rheology is better tool to evaluate the behavior of concrete. Pumping is a process that induces considerable shearing in the concrete that can impact its rheological properties. Therefore, the magnitude of these changes in fresh properties
The concrete pump is often used in commercial construction and is particularly helpful where access is difficult (for example, in tunnels). However, concrete pumping remains to date an empirical, trial-and-error process, involving frequent troubleshooting on construction sites.
The rheology of fresh concrete has a major impact on the way it is mixed, transported, pumped, placed and finished. Traditional test methods of slump or slump flow measurement are not capable of characterizing the fundamental rheological properties of fresh concrete. Workers often observe a significant difference when handling concrete even if the mixes exhibit similar slump and slump flow values. The situation in the field of concrete technology was so unsatisfactory that Tattersall wrote in 1976 that "at present, the most reliable method of measurement of workability is subjective judgement by an experienced operator….it remains common experience for two concretes giving identical slump …
30–60 s-1 during pumping, in the bulk concrete. Assuming the lubrication layer has 10 times lower viscosity, the shear rate in this layer would be several 100 s-1. As shearing can signiﬁcantly affect concrete rheology, SCC properties should be largely affected
The rheology of fresh concrete has a major impact on the way it is mixed, transported, pumped, placed and finished. Transport of fresh concrete by pumping through pipes to the point of placement has been used since the 1930s and, given current trends
Adding a polymer-based pumping aid can modify the cement paste rheology to help provide this enhanced lubrication. Pumping aids can also provide better workability retention for long pumping distances and can be particularly effective if interruptions to pumping are likely and when segregation or stiffening in the line could prevent a restart.
3. Lubrication layer The concrete pumped in the pipe comprises two parts: bulk concrete and lubrication layer. The pipe flow of the pumped concrete is predominated by the lubrication layer. The relatively thin lubrication layer has a lower viscosity than the bulk
11/4/2020 · A recent study on pumping of concrete has shown that the lubrication layer thickness appeared not to be a ected by the coarse aggregate size, but its rheological properties were a ected . In light of the discrepancies in reported values for thickness and
22/1/2015 · The rheology of concrete is predominant for the required pressures in a pumping pipe. However, more detailed information is required on the formation and the properties of the lubrication layer near the pipe surface, in order to be able to accurately predict the pressure-discharge relation. By means of experimental research in combination with advanced numerical simulations, the lubrication
In contrast, heterogeneities in the range of 3-5% are specified for pumping and in rheometers. In [6, 7] the rheological properties of both concrete bulk and lubricating layer due to particle
These pumps are capable of pumping 130 m3 of concrete per hour with 8 inch pipes. Squeeze pumps or peristaltic pumps are the ones that use vacuum pumping. These pumps can cover a distance of 90 m horizontally and 30 m vertically, and are capable of pumping 20 m3 of concrete per hour using 3 inch pipes. (a) Direct acting piston pump.
25/11/2016 · Abstract. Pumping of fresh concrete is of utmost importance for concrete practice. Required pumping pressures are typically estimated based on design charts. However, with the increased use of chemical admixtures and the development of more flowable concrete mixtures, the accuracy of traditional design charts is questioned.
through analyzing the properties of lubrication layer playing a dominant role to facilitate concrete pumping. Concrete mixtures incorporating blast furnace slag (BFS), fly ash (FA) and silica fume (SF) were selected with three different replacement ratios for each
Pumping is the most efficient transportation and placing method for concrete. Despite the immense progress in the field of concrete technology, so far there are neither official regulations nor
The rheology of concrete is predominant for the required pressures in a pumping pipe. However, more detailed information is required on the formation and the properties of the lubrication layer near the pipe surface, in order to be able to accurately predict the pressure
8/7/2014 · 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