Lagenbildung - Teil 1: Untersuchungen zur Förderung von Nass-Mischgut und zur Lagenbildung im aufgetragenen Spritzbeton

In the ÖBV-FFG funded research project "Advanced and sustainable sprayed concrete (ASSpC)" new shotcrete mix designs were developed. This paper deals with the effect of the fresh concrete properties and the pumping processes at the spraying machine on the sprayability and layer formation in the applied shotcrete. In addition to the fresh concrete properties and rheological properties of the concrete, the various pumping flows at the spraying machine were investigated (measurements of the pressures in the various delivery lines for concrete, accelerator and compressed air were carried out). Furthermore, findings from slowmotion pictures of the spray jet are reported. A marking agent was added to the accelerator to finally document its distribution in the applied shotcrete. It was shown that - assuming correct nozzle technique - the formation of layers in the shotcrete depends strongly on the machinerelated influences of the pumping and spraying process. It is accompanied by an unwanted uneven distribution of the accelerator in the concrete, which has far-reaching negative consequences on the shotcrete properties. The visualization of the optically visible and
optically invisible inhomogeneities is reported in a related further article (Layer Formation - Part 2). Derived from the results shown, a large development potential for devices and processes is opened up