NL9101666A - Shuttering arrangement for concrete - Google Patents

Abstract

The present invention provides a shuttering arrangement for concrete, comprising: two shuttering walls spaced apart; and one or more rods or wires which are attached to the shuttering walls and are made of plastic material having a breaking strength of more than 100 kN, or 196 kN (103 Newtons) or a so-called 0.2% proof stress (0.2% yield strength, tensile yield strength), i.e. 1.75 x the breaking strength. Although much research has been carried out into plastic fibres having a particularly high tensile strength, it is further proposed that the rods or wires preferably be made of aramid fibres, which are expected to be readily embeddable in concrete. Aramid fibres are already commercially available under the names Kevlar<IMAGE>, Twaron<IMAGE> (Arapree<IMAGE>) and Technora<IMAGE>.

Description

FORMWORK DEVICE FOR CONCRETE

In practice, in many cases concrete is poured into a formwork that determines the thickness of the wall to be poured. When pouring the concrete, great outward forces are exerted on the walls of the formwork. For this purpose, steel bars are usually included between the formwork walls. When removing the formwork, after the concrete has hardened, the concrete must be removed over some depth, after which the rod can be cut and the wall can be smoothed. If reinforcement is included in the concrete, such bars, also called center pins, formwork clamps, Dywidag bars or quick-release clamps, may contact the reinforcement, and if the ends of the bars are not sufficiently finished, this can cause corroding. Formwork devices are also known in which the metal bars are accommodated in a tube, for instance of plastic, fiber concrete or steel, and are removed after the concrete has hardened. This may reduce the strength of the concrete wall.

From US Pat. Nos. 3,734,453 and 4,006,878 formwork devices are known in which plastic rods or wires are used. However, such formwork devices have not been used in practice, since these wires have proved unable to withstand the forces that occur when pouring concrete.

The present invention provides a formwork apparatus for concrete, comprising: - two spaced formwork walls; and - one or more rods or wires attached to the formwork walls and made of plastic material with a breaking strength of more than 100kN, or 196 kN (10 Newton) or a so-called 0.2 yield strength, ie 1.75 x breaking strength .

Although much research is being carried out into plastic fibers with particularly high tensile strength, it is furthermore preferably proposed to use for the rods or wires of aramid fibers, which are expected to be well embedded in concrete. Aramid fibers are already on the market under the names Kevlar®, Twaron® (Arapree®) and Technora®.

Further advantages, features and details of the present invention will become apparent from a description of a preferred embodiment thereof, with reference to the accompanying figure.

A preferred embodiment of a shuttering device 1 according to the present invention comprises shuttering walls 2, for instance of wood, between which concrete C is poured. Wires or rods 3 of aramid fibers are inserted through holes in the formwork walls, which are secured to the outside of the formwork walls by means of clamping elements 4.

Preferably, the wires or rods 3 are passed through spacer 5, which is provided with openings so that the concrete penetrates to the wire 3 which is thus embedded. In the exemplary embodiment shown, a spacer 5 for keeping the formwork walls 2 at a distance before concrete C is poured is of a screw design, for instance also of plastic.

After the concrete has hardened, the clamping elements 4 can be easily removed, the formwork walls 2 removed and the wires 3 cut or ground on the concrete surface, without further finishing being necessary.

A concrete wall formed with the aid of the preferred embodiment of the shuttering device according to the present invention will exhibit a long service life, will exhibit good acoustic insulation (no cavities), and be highly waterproof. Such a concrete wall will have a high quality, while the number of lost parts is small and therefore the cost price is relatively low. Moreover, the labor effort to be made for building the wall will be small.

Claims (4)

Formwork device for concrete, comprising: - two formwork walls arranged at a mutual distance; and - one or more rods or wires attached to the formwork walls and made of plastic material with a tensile strength greater than 100kN (103 Newtons). Formwork device according to claim 1, wherein the rods or wires are made of round or rectangular aramid fibers, preferably with a cross section 2 of more than 30 mm. Formwork device according to claim 1 or 2, provided with clamping elements for clamping the bars or wires on the outside of the formwork walls. Formwork device according to claim 1, 2 or 3, provided with spacers for keeping the formwork walls at a distance, which are arranged around the bars or wires and which are provided with openings.