Abstract

ASSALI, Mirella Pennacchi  and  LOH, Kai. Feasibility of employing retarding agents as a substitute for conventional release agents in concrete moulding for the application of rendering mortar. Ambient. constr. [online]. 2011, vol.11, n.4, pp. 07-23. ISSN 1678-8621.  http://dx.doi.org/10.1590/S1678-86212011000400002.

The presence of the release agent on the surface of concrete structures may jeopardize the initial adhesion of the mortar still in plastic state to the concrete surface, as well as the bond strength after hardening. The aim of this study is to explore the potential use of retarding agents as a replacement for conventional release agents in concrete formwork in order to achieve greater bonding strength on the mortar surface. The technical feasibility of using a retarding agent was verified by comparing the tensile bond strength of rendering mortars applied on concrete surfaces cast with a conventional release agent and with a retarding release agent. The adhesion test showed that the use of retarding products allowed easier removal of the concrete surface layer, which increased surface roughness, and surface water absorption e. Finally, performance tests were done with commercially available retarding products to verify the behaviour of such products during application on moulds, their impact on workers' health and on the environment. Retarding agents proved to be a feasible technique to avoid detachment problems of rendering mortars applied on concrete surfaces.

Keywords : Concrete; Release agents; Retarding agents; Mortar; Tensile bond strength.