FR2665922A1 - Protection for wooden shuttering panels using non-adhesive liquid film - Google Patents

Abstract

Method for applying a synthetic resin on wooden shuttering elements making it possible to substantially improve the finishing quality of concrete, to avoid the use of an oil for dismantling shuttering, and to remedy all the problems posed by pouring concrete on wood shuttering, such as nailability, leaktightness defects at the joints (seals), etc.

Description

The present invention relates to forms, panels or assemblies of wooden structures intended to be used for formwork of works or molded concrete objects. These elements of formwork are light, allowing easily to realize structures with complex shapes and assemblies. problems related to their employment remain, however:
-The laitance of the concrete flows between the joints between elements, which creates spalling of the concrete and makes demolding of the concrete difficult. A treatment of the concrete is necessary to eliminate these defects (sanding, grinding, possible leveling).

 -After a certain number of cycles, leaks at the level of the nails create swelling of the panels, and a rapid deterioration of the formwork elements. appearance of concrete.

 -In the case where the panels are coated with a protective adhesive film (for example ebonite sheet), the installation of a nail causes the bursting of the protective sheet, thus creating a rupture of the seal.

 -In the case of complex assembly structures, the assembly angles appear clearly marked on demolding, which requires a correction of this defect in appearance.

- The formwork oil is necessary to facilitate demolding, which leads to several drawbacks:
.oil is one of the causes of bubbling concrete, which is detrimental to the appearance, especially in the case of architectural concrete.

 The oil permeates the concrete support, which sometimes requires a preliminary treatment for its elimination before applying a coating on the concrete.

 All the drawbacks previously explained can be eliminated by implementing the method for coating the formwork which is the subject of the present invention.

The method consists in applying to the formwork elements either by spraying with an application machine or manually a liquid film of the resin type adhering to the wood and having all of the following properties:
-Very good resistance to shocks and impacts.

 -very good resistance to wear.

 -resistance to basic pH of concrete.

 -tight, without porosity.

-Having thixotropy qualities allowing application in thick
variable sister.

 -being a non-stick of concrete.

-be nailable
Such properties can best be obtained with modified polyurethane or polyurethane resins, one-component or two-component, and can also be regenerated or repaired on site in the event of accidental degradation or significant wear due to service constraints.

Such a technique ensures the following important functions for the efficiency and durability of wooden formwork:
-Water tightness, which eliminates the spalling of concrete, and also ensures the dimensional stability of the panels.

 -Mounts nails, metal frames, etc. without leaving a source of infiltration, while ensuring perfect quality of smooth surface appearance.

 - Nailable, without risk of leakage at the nails.

 -Allows thanks to its thixotropy to compensate for the angular lines of a complex structure, by depositing if necessary a greater quantity of material at the places whose geometry is to be corrected.

 - formwork oil is not necessary, thanks to its naturally non-stick properties of concrete.

The simple implementation of this process thus makes it possible to ensure a significant improvement in the technique of wooden formwork, mainly on the following points:
-better quality of finish appearance of the poured concrete.

 -healthy concrete, because not impregnated with formwork oil.

-ensures a longer life of the panels which are especially
degraded by leaks and mechanical shocks.

Claims (2)

 l.-A method of treating wooden panels or structures used as formwork elements characterized in that it consists in the application of a liquid film adhering to the wood, of resin type, applied manually or by machine and removing any oil formwork.  2.-Method according to claim I characterized in that it implements a film consisting of a polyurethane resin or modified polyurethane, mono or two-component.