Abstract
To study the influence of different mix proportions on the fresh properties of wet shotcrete, the rheological properties and air content of wet shotcrete with different admixtures before pumping were measured. In addition, the pressure drop along the pipeline and the build-up thickness were studied, and the relationship between the rheological properties and the pumpability and sprayability was discussed. This paper attempts to reveal the influence mechanism of admixtures on the fluidity of wet shotcrete by means of pictures. The results show that free paste effect and ball effect are two key factors that affect the performance of fresh wet shotcrete. Air-entraining agent and fly ash are commonly used admixtures, which improve the pumping performance and spraying performance. Finally, the mix proportions of wet shotcrete are put forward to meet the requirements of different types of shotcrete.
Highlights
Wet shotcrete is a kind of self-compacting concrete technology, in which fresh wet shotcrete is pumped into the pipeline, and sprayed onto the receiving surface under the function of compressed air [1,2,3,4,5,6,7]
Pumpability refers to the pumping capacity of fresh wet shotcrete, i.e., fresh concrete should have proper fluidity and stability when transported through pipes under pressure
Yun et al [17,18] used the IBB rheometer to measure the influence of mineral admixtures on the performance of wet shotcrete, and concluded that the pumpability and shotcretability of fresh concrete can be improved by adding silica fume and fly ash at the same time
Summary
Wet shotcrete is a kind of self-compacting concrete technology, in which fresh wet shotcrete is pumped into the pipeline, and sprayed onto the receiving surface under the function of compressed air [1,2,3,4,5,6,7]. Yun et al [17,18] used the IBB rheometer to measure the influence of mineral admixtures on the performance of wet shotcrete, and concluded that the pumpability and shotcretability of fresh concrete can be improved by adding silica fume and fly ash at the same time. Mixing various chemical admixtures or mineral additives can have a significant impact on the rheological properties of concrete, affecting the pumping performance, at the same time, improving the stability of the mixture, and even changing the thickness of the lubrication layer [28,29]. To study the rheological properties of wet shotcrete with different admixtures and further estimate the pumpability and shotcreting performance before pumping, this paper studies the influence of water–binder ratio (w/b, WC), sand ratio (SR), fiber length (FI), air-entraining agent (AE), water-reducing agent (WR), silica fume (SF) and fly ash (FA). The main goal is to provide a simplified guide for shotcrete technologists
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