DE202015002828U1 - Easily dismountable formwork for concrete test specimen made of glass-clear acrylic glass preferably PLEXIGLAS® - Google Patents

Abstract

Easily dismountable formwork for concrete test specimen made of crystal-clear acrylic glass, preferably PLEXIGLAS®, characterized in that sheets of clear acrylic glass, preferably PLEXIGLAS® of thickness up to 20 mm are milled so that the individual parts can be assembled and professionally glued and an upwardly open mold for Betonprüfkörper whose dimensions (1), (2), (3) meet the requirements of DIN EN 12390: 1 2012 for a calibratable formwork form. (1)

Description

For formwork forms for concrete test specimens various materials are currently in use, such as steel, foamed plastic or other plastics.

To test the air content of the concrete sample directly in the formwork over the 2 bar water column (HYDRO_5 fresh concrete tester), foamed plastic molds are used, which have the advantage over assembled steel molds that they can be sealed with a rubber substance in the bottom opening in that no pressure escapes.

It has proven to be a disadvantage that the plastic molds at the test pressure load of 2 bar expand like a balloon. Volume increases of 25 to 45 ml were measured. This corresponds to a volume of the form of 3375 ml of an increase of 0.7 to 1.3%.

After the concrete has hardened, the rubber substance d = 10 to 12 mm is removed from the bottom opening and a pressure gun is guided into the opening. The air or water pressure (maximum 2.5 to 3 bar) then presses the test specimen out of formwork.

Thus, initially, if the test piece still sits firmly in the mold, a force of about 1 to 2 kg must be sufficient to release the test specimen from the formwork.

In fact, this relatively low pressure is usually sufficient for stripping, because the molds are injected around a core, which must be pulled after cooling of the plastic. This is only possible if the core is larger on the outside than inside, so is designed as a stump pyramid. The greater the deviation, the easier it is to pull the core and the easier it is to shed the concrete specimen.

However, the advantage of the easy Ausschalens is bought with the disadvantage that in the concrete strength test, the pressure surfaces are not parallel. This has disadvantages on the strength results.

In composite metal molds, the pressure surfaces are parallel, at least if the manufacturing ensures appropriate accuracies. However, even after the first use there is no longer any certainty for the accuracy, because deformations of the individual parts and soiling during assembly can lead to considerable deviations.

Thus, there should be clear differences between the strength results from the molds in each case and from one use to another but especially between plastic molds and steel molds.

It is therefore understandable that there is no form of form on the market which, as a calibrated form, meets the requirements of the market Standard DIN EN 12390: 1 2012 fulfilled, because the dimensions specified there are not reached within the required tolerances secured.

The previous formwork forms have one thing in common. During filling and compaction, it is not visible whether the compaction is sufficient.

What we are looking for is a mold that ideally combines the advantages of the steel mold and the plastic mold and is used as a calibrated mold. DIN EN 12390: 1 2012 suitable is. The use of a calibrated formwork form has the advantage that the test specimens produced therein need not be laboriously measured and must be ground when the tolerances are exceeded. In addition, should be visible during compaction, whether all remaining on the formwork surfaces compression pores are expelled.

This problem is solved with the features listed in protection claim 1.

With the acrylic glass material selected for the invention preferably PLEXIGLAS ^® clear thickness up to 20 mm, the production in highest accuracy (+ -2 / 10 mm) is possible. The individual wall segments and the bottom plate are milled in accordance with the requirements of accuracy and glued into a closed upwardly open mold.

If the milled parts are glued correctly, the splices will withstand the loads when filling with concrete, withstand testing at 2 bar and stripping without difficulty.

In the formwork forms, it depends on the accuracy of the internal dimensions, because they determine the dimensions of the concrete test specimen. The formwork acc. listed in protection claim 1 features met for the first time for a one-piece shape, the dimensions and tolerances of the requirements of DIN EN 12390: 1 2012 ,

The test specimen produced therein has the shape of a stump pyramid, whereby the stripping by pressing is possible. The deviation of the side surfaces from the vertical ( 3 ) is lower than in the Standard DIN EN 12390: 1 2012 set as a limit.

This has not been achieved in the production of injection-molded plastics and has not been achieved, especially in the case of foamed plastics, not even because mold-forming bevels of 1 ° are required for foamed plastics. (Specification for polyurethane integral hard foam Baydur 60)

In addition, foamed plastic are very soft.

This is particularly disadvantageous when testing with the HYDRO_5 fresh concrete tester. The volume of the mold increases by 25 to 45 ml at a test pressure of 2 bar. This affects the quality of the measurement results. It is particularly disadvantageous that the values differ from shape to shape.

In addition, the soft plastic loses its shape very quickly with increasing use. The wall surfaces bulge, which also adversely affects the quality of the strength results.

The material selected according to the invention claim 1 Acrylic glass preferably PLEXIGLAS ^® clear the thickness to 20 mm, however, is much harder than foamed plastic and the formwork produced from it is to be considered at an elongation <15 ml at a test pressure of 2 bar as nearly dimensionally stable. This significantly improves the quality of the air pore content test results by means of the water column (HYDRO_5 fresh concrete test).

For the essential material parameters such as compressive strength, tensile strength and surface hardness of acrylic glass, twice to 4 times the values of the usual polyurethane integral foam are achieved.

The material characteristics of the invention acc. Claim 1 are exemplified for crystal clear PLEXIGLAS ^®.

The gem. Protection claim 2 attached handles is based on the problem that the formwork filled with a weight of up to 12 kg by the laboratory technician must be moved by hand. This problem solve the gem. Protection claim 2 attached handles ( 4 ) with the advantage that they are connected via a screw connection ( 5 ) are fixed so that the screws are to be regarded as additional reinforcement of the adhesive bond.

The gem. Protection claim 3 located in the bottom opening ( 6 ) is based on the problem that over the opening pressure can be applied to the hardened concrete, so that the concrete test specimen dissolves from the mold and can then be completely turned off.

This problem is solved gem. Protection claim 3 a recess ( 7 ), which milled into the formwork floor and which corresponds in the dimensions of a metal disc and in which the metal plate can be placed before filling with concrete, so that the surface of the metal disc and the shuttering floor form a flat surface.

After hardening of the concrete, a force can then be exerted on the metal disk, which can press the test piece out of the formwork.

Conveniently, the opening is formed so that the metal disc is connected during filling with the formwork so that the opening is pressure-tight manner.

LIST OF REFERENCE NUMBERS

1

Inside dimension below

2

External dimension below

3

Inside dimension above

4

External dimensions above

5

Deviation from the vertical

6

Deep container shape

7

handles

8th

Screw connection for reinforcement

9

bottom opening

10

deepening

embodiment

• (1) Internal dimension below 149.2 mm
• (2) Inside dimension above 150.0 mm
• (3) deviation from the vertical 0.4 mm
• (4) handles strip 20/20 mm L = 190 mm
• (5) Bolt to reinforce M5
• (6) bottom opening d = 12
• (7) recess d = 40 mm T = 2 mm

Material crystal clear acrylic glass PLEXIGLAS ^® (source Evonik)

• Mechanical properties / Test specification / Value
• Density/ ISO 1183 / 1.19 g / cm3
• Tensile strenght/ ISO 527-2 / 16/5/80 MPa
• Elongation at break ISO 527-2 / 1B / 5 / 5.5%
• Modulus of elasticity/ ISO 527-2 / 1B / 1/3300 MPa
• Flexural strength / ISO 178 / 115 MPa
• compressive yield stress / ISO 604 / 110 MPa
• Shear modulus / ISO 537 / 1700 MPa
• Impact / ISO 179 / 1fu / 15 kJ / m ²
• Notched impact strength / ISO 180 / 1 A / 1.6 kJ / m ²
• Permissible material tension / - / 5-10 MPa
• Poisson / ISO 527-1 / 0.37
• Ball indentation hardness / ISO 2039-1 / 175 MPa
• Scratch resistance / ISO 9352 / 20-30% Haze
• Minimum allowable cold bend radius / - / 330 x plate thickness

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited non-patent literature

• Standard DIN EN 12390: 1 2012 [0010]
• DIN EN 12390: 1 2012 [0012]
• DIN EN 12390: 1 2012 [0016]
• Standard DIN EN 12390: 1 2012 [0017]

Claims (3)

Easily dismountable formwork for concrete test specimens made of crystal clear acrylic glass, preferably PLEXIGLAS ^®, characterized in that sheets of clear acrylic glass, preferably PLEXIGLAS ^® of thickness up to 20 mm are milled so that the individual parts can be assembled and professionally glued and an upwardly open mold for Betonprüfkörper whose dimensions ( 1 ) 2 ) 3 ) meets the requirements of DIN EN 12390: 1 2012 for a calibratable formwork form. ( 1 ) Mold form made of crystal-clear acrylic glass, preferably PLEXIGLAS ^®, characterized in that carrying handles ( 7 ) are mounted so that the screw ( 8th ) reinforced with the mold form the bond. Mold form made of crystal-clear acrylic glass, preferably PLEXIGLAS ^®, characterized in that a recess ( 10 ) is milled to receive a metal disc, which is dimensioned so that the surface of the metal disc with the shuttering bottom forms a plane.

Images