Browsing by Author "Labuschagne, Jean-Claude"
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- ItemFormwork pressures by self-compacting concrete: a practical perspective(Stellenbosch : Stellenbosch University, 2018-03) Labuschagne, Jean-Claude; Wium, Jan; Jurgens, Chris; Stellenbosch University. Faculty of Engineering. Dept. Civil Engineering.ENGLISH ABSTRACT: One of the challenges facing the South African construction industry is the prediction of lateral formwork pressure exerted by Self-Compacting Concrete. A major hindrance to the increased use of Self-Compacting Concrete (SCC) in cast-in-place applications in the South African construction industry is the lack of information about and understanding of, lateral formwork pressure exerted by SCC. There are no accepted standardised codes or guidelines for the local construction industry that can be used to facilitate the design of formwork for predicting formwork pressure exerted by SCC. Formwork systems designers have been encouraged to design formwork to withstand full hydrostatic pressures, unless a method based on appropriate and reliable experimental data is available. This generally limits contractors to low wall or extremely strong formwork, which can lead to extra formwork costs. Numerous parameters, including placement conditions, material properties and formwork characteristics can influence lateral formwork pressure. This study presents the results of an experimental investigation undertaken using on-site conditions, aimed at studying the influence of placement methods (top-down and bottom-up pumping), of various casting rates, as well as implementing predetermined waiting periods of 10 and 15 minutes between castings. The influence of each of these parameters was evaluated by using six vertical instrumented wall elements. All six walls were fitted with eight flush diaphragms transducers and were identical in dimensions (5.4 m x 2.0 m x 0.25 m). The test results show that with high casting rates from the top of the formwork system, hydrostatic pressure can be expected. It was shown that by interrupting the casting procedure and implementing waiting periods to allow the fresh SCC to set, decreased the lateral pressure exerted. It was found that, when pumping from the base of the formwork system at high casting rates, hydrostatic pressure could be expected during the casting process and that lateral pressures above the hydrostatic pressure could be expected during the casting of the SCC. The knowledge gained in this study can therefore be used to lay the foundation for future studies for the prediction of lateral pressure exerted on formwork by SCC under South African conditions.