WO1997027371A1

WO1997027371A1 - Masonry tape

Info

Publication number: WO1997027371A1
Application number: PCT/GB1997/000217
Authority: WO
Inventors: Thomas Saunders
Original assignee: Scapa Group Plc
Priority date: 1996-01-25
Filing date: 1997-01-24
Publication date: 1997-07-31
Also published as: GB9601517D0; AU1452997A

Abstract

A masonry tape (10) comprises one or more layers of a synthetic thermoplastics material provided in mesh form. One or more of the layers includes load bearing yarns (15) extending in the longitudinal direction of the tape. The load bearing yarns (15) have a Young's Modulus of at least 4 GN/mm2.

Description

Masonry Tape

The present invention relates to a masonry tape.

Masonry tapes, also known as lattice tapes, are used for reinforcing mortar, concrete or other hydraulic binder compositions, for example in

brickwork, plaster, concrete floors, thin concrete elements, foam concretes

or the like. One of the more important applications is the reinforcement of

mortar during the construction of a building wall from bricks, stone blocks or breezeblocks.

Conventional masonry tapes are made of steel, in the form of two

parallel Iongitudinal steel rods, bars or tapes interconnected by a series of

parallel transverse bars welded onto each steel rod, bar, tape etc., giving it

the appearance of a miniature ladder. Steel is used on account of its high

Young's modulus, a crucial property for masonry tape since even a fairly

small degree of elasticity in the Iongitudinal direction would lead to the

masonry cracking in the event of shear forces being applied. Cross-

directional strength is not considered to be important since the forces

experienced in the Iongitudinal direction of a masonry wall far exceed those

ever found in the cross-direction. Generally the cross-directional bars, that

is the ladder rungs, are there to make the tape easy to handle. The other

important property for masonry tape is the large open mesh area. If the

mesh holes are too small then the masonry tape effectively forms an

intermediate layer within the mortar, creating upper and lower mortar phases, which in turn make the masonry construction far more susceptible to cracking and shear.

A masonry tape is typically 60 - 80 mm wide using two parallel 4 -

5 mm diameter steel rods linked via welded "rungs" to give a structure

having a Young's modulus in the longitudinal direction of about 5 GN/mm².

An alternative to steel masonry tapes is the product developed by

Akzo Nobel Faser AG and sold by the Dutch company Intervam under the trade name ARAGRID, which is a fabric comprising woven Twaron para-

aramid fibres (supplied by Akzo Nobel Faser AG) held in an epoxy resin

matrix whose surface has been sprinkled with sand to improve adhesion to

mortar. This woven lattice tape is laid into mortar for brick wall

constructions in order to reinforce the masonry against cracking. The strength member in ARAGRID tape consists entirely of p-aramid polymer.

Therefore, unlike steel, it can be used in acidic or alkaline environments; it

is several times stronger than steel; weighs less thus allowing easier

handling, transport and storage, and is much easier to cut, for example

scissors may be used.

As an example, ARAGRID tape Type 5001 has a tensile strength of

75 kN/m, an elongation at break of 4.4%, a modulus of elasticity 45 GPa

[according to ASTM D 885], a mesh size of 10mm² and a unit weight of

300 g/m². However, ARAGRID uses para-aramid yarns in both Iongitudinal

and transverse directions. These para-aramid yarns are very expensive. Other conventional synthetic woven tapes also consist of very expensive material so that high material costs are involved in the production of the woven tape.

The present invention has been made from a consideration of this problem.

The present invention seeks to provide an improved membrane having the required characteristic properties such as high Young's modulus, tenacity and Iongitudinal tensile strength for use as a masonry tape.

According to a first aspect of the present invention there is provided a masonry tape comprising one or more layers of a synthetic thermoplastics

material provided in mesh form, one or more of said layers including load bearing yarns extending in the longitudinal direction of the tape, wherein at least some of said load bearing yarns have a Young's Modulus of at least 4 GN/mm².

Thus the said load bearing yarns have a low extrusion under high

load. This is a particularly desirable property for a masonry tape. Preferably

said at least some load bearing yarns have a maximum elongation at break

of 5%. Preferably no expensive high performance yarn material is provided in the transverse, cross machine direction. Furthermore not all of the Iongitudinal extending yams need comprise such high performance material.

Preferably at least 25% of the longitudinally extending yarns have the said

Young's Modulus value. The yarns are preferably wholly provided within the lands of the mesh.

The load bearing yarn material may comprise one or more of the

following; a para-aramid, meta-aramid, liquid crystal polymer or gel-spun

polyolefin, such as those sold under the trade names KEVLAR, TWARON,

DYNEEMA, CERTRAN, NOMEX or VECTRAN. The high strength material

would be present as a core yarn coextruded with a sheath of thermoplastics material such as polyurethane or polyamide.

Thus, the present invention provides a replacement for conventional

synthetic products which is less costly to produce.

Preferably the tape would have one or more of the following

properties:- Young's modulus 4 - 7 GN/mm², tenacity 2000 - 3000 MPa, tensile strength (in lengthways direction) 70 - 150 kN/m modulus of

elasticity 35 - 60 GPa [according to ASTM D 885] and unit weight of 200 -

300 g/m². The tape may comprise two layers, each of which may have

different mesh sizes.

Preferably the minimum total mesh opening size would be in the order

of at least 10mm². Otherwise the tape will act as a barrier layer that

separates the top and bottom layers of mortar, giving a highly unstable wall

construction. The mesh openings are typically of rectangular form extending

longitudinally in the Iongitudinal direction of the tape.

Typically the layers will be of the order of 1 to 2 mm thick although the thickness may depend on the number of superimposed layers in the tape. The tapes are easier to store and handle as well as contributing less

to the "barrier layer effect" when placed in mortar. For most purposes, the

tape will be of the order of 60 - 80 mm wide. The tape ideally has planar

upper and lower surfaces so as to minimise the required storage space.

The preferred material for the matrix of the mesh layers is

thermoplastic polyurethane. However, any suitable thermoplastics material

is appropriate. Localised protuberances or profiled ribs may be provided on

one or more surfaces of one or more of the layers to increase the surface

area thereby enhancing adhesion with the mortar in use.

According to a second aspect of the present invention there is

provided a method of making a masonry tape, said masonry tape comprising

at least one layer of synthetic thermoplastics material in mesh form, said

method comprising the steps of forming the said mesh by heating the

thermoplastics material so as to fluidise the said material on a body

comprising a series of pins, such that on cooling the thermoplastics material

sets in the said mesh form, the pins of the said body extending through the

mesh so as to define apertures in the mesh, wherein load bearing yarns are

provided within the lands of the mesh, said load bearing yarns extending in

the Iongitudinal direction of the tape, at least some of the load bearing yarns

having a Young's Modulus of at least 4 GN/mm²-

According to a third aspect of the present invention there is provided a method of making a masonry tape, said masonry tape comprising at least

one layer of synthetic thermoplastics material in mesh form, said method

comprising the steps of forming the said mesh by heating the thermoplastics material so as to at least partially fluidise the said material on a body

comprising a series of pins, then laying yarn members onto said partially

fluidised material at regular intervals substantially transverse to the length direction of the thermoplastics material members, such that on cooling the

thermoplastics material bonds with said transverse yarn members to form

a mesh, wherein load bearing yarns are provided within the lands of mesh,

said load bearing yarns extending in the Iongitudinal direction of the tape, wherein at least some of the load bearing yarns have a Young's Modulus of at least 4 GN/mm².

The masonry tape is preferably made by heating a plurality of yarns

comprising thermoplastics material on a pinned plate or drum such that the

thermoplastics material is fluidised and fills the space between the pins of

the plate and drum. On solidification the thermoplastics materials is formed

as a mesh, the apertures through the mesh corresponding to the position of

the pins of the plate or drum. A load bearing yarn may be added in the

mesh by applying a core sheath yarn to the pinned plate or drum the core

being a non-thermoplastics materials such as aramid. The sheath could be

a thermoplastics material such as polyurethane. Here the core yarn would

not fluidise on heating and thus would form a load bearing yarn through the longitudinal lands of the mesh tape.

It will be appreciated that the present invention has all the advantages as aforesaid of conventional synthetic tapes over conventional steel

masonry tapes, including being lightweight and not being susceptible to

corrosion, but has several additional advantages over such tapes.

It is noted that, due to its nonwoven nature, the masonry tape of the

present invention does not require expensive narrow weaving machinery.

Also it is far less expensive in material costs. TWARON, for example is a

very expensive material. The tape of the invention achieves the same

strength or Young's Modulus as conventional synthetic masonry tape products, such as ARAGRID but uses only a fraction of high performance yarn material.

Being nonwoven the Iongitudinal yarns are entirely straight so that

any load forces are taken up immediately, whereas fabrics with woven

structures such as ARAGRID will therefore possess a degree of crimp and

hence possibly extend under the influence of Iongitudinal forces. An elastic matrix of, for example, polyurethane enables the tape to deform somewhat

in use in accordance with the contours of the bricks, stones, blocks or the

like whereas a steel or conventional synthetic fabric such as TWARON is

fairly incompressible.

Furthermore the ability to provide transverse rib profiles to improve

tape-to-mortar adhesion is a far less messy process than the standard method of providing a sand coating, although clearly a sand coating may

also be used if preferred for the tape of the present invention.

The masonry tape of the invention has application as a reinforcement

in any suitable structural building element. The specific mechanical

properties and geometric dimensions of the tape will typically depend on the specific application thereof.

The invention will now be further described by way of example only and with reference to the accompanying drawings in which:-

Fig. 1 is a diagrammatic perspective view of one form of masonry

tape constructed in accordance with the invention; and

Figs. 2 and 3 are enlarged sections taken on lines IMI and Ill-Ill,

respectively, of Fig. 1.

Referring to the drawings, and particularly to Fig. 1 thereof, a

masonry tape 10 comprises a mesh layer 1 1 , which presents longitudinally

extending land areas 12 and transversely extending land areas 13, to give

rectangular mesh openings 14 and areas 12 include yarns 15 to provide

load bearing yarns in the Iongitudinal direction of the tape, the yarns having

a maximum elongation at break of 5%. The yarns may be coextruded with

a sheath (not shown) of thermoplastics material.

Typically the size of the mesh openings 14 will be at least 10 mm²

and the total through opening size of the mesh should preferably be at least 10 mm². The apertures need not, of course, be of rectangular configuration.

The mesh layers are conveniently manufactured by providing a series of longitudinally extending core sheath yarns on a pinned drum of the type disclosed in GB-A-2202873. The core is made from an aramid material and

the sheath from a thermoplastics material. A series of monofilament yarns are further provided in the transverse direction. The thermoplastics material is subsequently heated so as to fluidise that material until it fills the gaps between the pins on the pinned drum. On cooling the thermoplastics material solidifies in the form of a mesh having aramid yarns running through the iongitudinal lands thereof. Other materials may however be used such as, for example, a powder dispersal technique.

It will be appreciated that the present invention is not intended to be restricted to the details of the above embodiments which are described by way of example only. In particular, a tape of the invention may comprise more than one layer of thermoplastics material.

Claims

O i S

1. A masonry tape comprising one or more layers of a synthetic thermoplastics material provided in mesh form, one or more of said layers

including load bearing yarns extending in the Iongitudinal direction of the

tape, wherein at least some of said load bearing yarns have a Young's

Modulus of at least 4 GN/mm^2-

2. A masonry tape as claimed in claim 1 , wherein the said at least some

load bearing yarns have a maximum elongation at break of 5%,

3. A masonry tape as claimed in claim 1 or claim 2, wherein the load

bearing yarns are provided wholly within lands of the mesh.

4. A masonry tape as claimed in any preceding claim, wherein the load

bearing yarn comprises any of the following:- para-aramid, meta-aramid,

liquid crystal polymer or gel-spun polyolefin.

5. A masonry tape as claimed in any preceding claim, wherein the

thermoplastics material comprises polyurethane.

6. A masonry tape as claimed in any preceding claim, wherein the

minimum total mesh opening size is at least 10mm².

7. A masonry tape as claimed in any preceding claim, wherein localised

protuberances or profiled ribs are provided on one or more surfaces of one

or more layers of the tape.

8. A method of making a masonry tape, said masonry tape comprising

at least one layer of synthetic thermoplastics material in mesh form, said method comprising the steps of forming the said mesh by heating the thermoplastics material so as to fluidise the said material on a body

comprising a series of pins, such that on cooling the thermoplastics material

sets in the said mesh form, the pins in the said body extending through the apertures through the mesh, wherein load bearing yarns are provided within

the lands of the mesh, said load bearing yarns extending in the longitudinal

direction of the tape, wherein at least some of the load bearing yarns have

a Young's Modulus of at least 4 GN/mm² 9. A method of making a masonry tape, said masonry tape comprising at least one layer of synthetic thermoplastics material in mesh form, said

method comprising the steps of forming the said mesh by heating the

thermoplastics material so as to at least partially fluidise the said material

on a body comprising a series of pins, then laying yarn members onto said

partially fluidised material at regular intervals substantially transverse to the

length direction of the thermoplastics material members, such that on

cooling the thermoplastics material bonds with said transverse yarn

members to form a mesh, wherein load bearing yarns are provided within

the lands of mesh, said load bearing yarns extending in the Iongitudinal

direction of the tape, wherein at least some of the load bearing yarns have

a Young's Modulus of at least 4 GN/mm².