Abstract
Concrete surface quality is generally linked to the development conditions of concrete close to the formwork. This work aims to study the influence of the nature of release agent and the quantity of fine elements on the chemical interactions at the concrete/oil/formwork interface. Five concretes were prepared at 28, 30, 32, 34, and 36% of paste to study the influence of paste volume on the friction between formwork and fresh concrete. The friction tests were performed using an apparatus which can reproduce the same conditions of construction sites. In addition, a physicochemical investigation was achieved to identify the effect of fine elements on the ability to form the interstitial mediums at the interface. The formation of soap in the vicinity of the formwork surfaces was also studied as a function of the content and the nature of oils. The results showed that the friction between fresh concrete and formwork depends on the pore solution content present at the interface.
Highlights
The characterization of fresh concrete on construction sites is still typically limited to use of a single parameter, workability, which is presumed to describe the behaviour of fresh concrete
To understand the mechanisms at the concrete/oil/formwork interface as they relate to the paste volume, friction tests were conducted using a plan/plan tribometer
The results show that the curve shapes are similar regardless of the pressure
Summary
The characterization of fresh concrete on construction sites is still typically limited to use of a single parameter, workability, which is presumed to describe the behaviour of fresh concrete. Good workability reduces the risk of defects and improves the final quality of structures (Amziane et al 2005; Ferraris, De Larrard 1998; Laskar, Talukdar 2009). There are many gaps in the understanding of the phenomena that take place when concrete is poured into formwork. Some of these phenomena are directly related to the friction between the materials in contact. The friction at the concrete/formwork interface can be considered a favourable factor that reduces lateral pressure exerted on the formwork, but it can be unfavourable to the quality of the concrete surfaces (Proske et al 2010; Graubner et al 2012; Libessart 2006; Kwon et al 2011). Some studies have reported on the effect of friction on formwork pressure. Proske (2007)
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