WO2016024135A1

WO2016024135A1 - Anti-ballistic structure

Info

Publication number: WO2016024135A1
Application number: PCT/GB2015/052371
Authority: WO
Inventors: Dominic DILLION; Richard Elliott
Original assignee: Enviromate Limited
Priority date: 2014-08-15
Filing date: 2015-08-14
Publication date: 2016-02-18
Also published as: GB2529396B; GB201414556D0; GB2529396A

Abstract

This invention relates to blast-proof or bullet-proof structures. In particular, this invention relates to structures comprising a wall made from a material comprising rubber in a cementitious material. An anti-ballistic structure including a wall made from a material comprising rubber pieces with embedded fibres in a cement matrix, the volume ratio of said rubber pieces and cement in a dry state is between 3:1 and 8:1.

Description

Anti-ballistic Structure

BACKGROUND a. Field of the Invention

This invention relates to blast-proof or bullet-proof structures. In particular, this invention relates to structures comprising a wall made from a material comprising rubber in a cementitious material. b. Related Art

Anti-ballistic structures include both bullet-proof structures and blast-resistant structures. Bullet-proof structures are designed to prevent or resist the penetration of bullets or other high velocity projectiles such as shrapnel. Blast-resistant structures are primarily designed to resist deformation and damage caused by the shock waves emanating from a bomb blast or other explosion. Blast-resistant structures are also designed to minimise blast induced debris, which can cause further damage or injury in addition to the initial blast.

Traditionally anti-ballistic structures include one or more panels of steel. They are, therefore, heavy and difficult to erect. It is an object of the present invention to provide improved anti-ballistic structures.

SUMMARY OF THE INVENTION

According to the present invention there is provided an anti-ballistic structure including a wall made from a material comprising rubber pieces with embedded fibres in a cement matrix, the volume ratio of said rubber pieces and cement in a dry state is between 3: 1 and 8: 1 .

Preferably the volume ratio of said rubber pieces and cement in a dry state is between 3: 1 and 6: 1 .

In preferred embodiments the material further comprises an aggregate having a particle size of less than 2 mm. Most preferably this aggregate is sand. Beneficially the volume ratio of sand and cement, in a dry state, is between 1 : 1 and 2: 1 .

As such, in preferred embodiments, the wall of the anti-ballistic structure is composed primarily of rubber pieces with embedded fibres and sand in a cement matrix and includes no steel. In particular, a wall made from this material has been shown to prevent the penetration of shrapnel and armour piercing bullets without requiring any steel cladding or steel reinforcement.

In preferred embodiments the material comprises, in a dry state, more than 40% by volume rubber pieces with embedded fibres. In particularly preferred embodiments the material comprises, in a dry state, 55-80% by volume rubber pieces with embedded fibres, 8-25% by volume cement, and 10-23% by volume sand.

In some embodiments the wall is a single skin wall. In these embodiments the material of the wall preferably comprises, in a dry state, 55-65% by volume rubber pieces with embedded fibres, 18-22% by volume cement, and 18-22% by volume sand. The thickness of said single skin is preferably between 200 mm and 600 mm.

In other embodiments the wall is a double skin wall with a cavity between said skins. In these embodiments the material from which at least one of the walls is made preferably comprises, in a dry state, 55-72% by volume rubber pieces with embedded fibres, 16-25% by volume cement, and 16-23% by volume sand. The cavity preferably has a thickness of between 50 mm and 100 mm. The thickness of each of the two skins is preferably between 200 mm and 400 mm.

To aid in the ease of construction of the wall, the wall is preferably constructed from pre-cast blocks of said material.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be further described by way of example only and with reference to the accompanying drawings in which:

Figure 1 is a plan view from above of a single skin anti-ballistic wall according to an embodiment of the present invention;

Figure 2 is a plan view from above of a double skin anti-ballistic wall according to an embodiment of the present invention;

Figure 3 is a plan view from above of the double skin wall of Figure 2 with an additional, optional cladding layer;

Figure 4 is a perspective view of a block used in the construction of an anti- ballistic wall according to a further embodiment of the present invention; and

Figure 5 is a plan view from the side of a wall constructed from the blocks of Figure 4.

DETAILED DESCRIPTION

Typical bullet proof or blast proof structures include a layer of steel to prevent the penetration of a bullet, shrapnel or other high velocity ballistic through the structure. These structures are, therefore, relatively heavy and difficult to construct, especially in a harsh environment or if there is limited time or man power available.

The present invention provides an anti-ballistic structure, i.e. one that is capable of withstanding the penetration of bullets, shrapnel and other similar projectiles, that is easier to assemble than previous structures and does not require the use of steel plates or panels.

The structure comprises one or more walls that are made from a material consisting primarily or entirely of rubber pieces with absorbent fibres and a small particle size aggregate in a cement matrix. By altering the ratio of rubber pieces to cement it is possible to tune the properties of the material to withstand different threat levels, e.g. to withstand larger or higher velocity ammunition. The level of protection afforded by the wall may be measured with respect to a NATO Standard such as STANAG 4569 or a British Standard such as BS EN 1522/1523.

The rubber pieces typically have dimensions or an equivalent diameter of 5 mm to 30 mm. The absorbent fibres are at least partially embedded in the rubber pieces and, preferably, at least end regions of the fibres project from the rubber pieces.

The fibres are, therefore, able to form a bond with the surrounding cement matrix.

The fibres are preferably cloth-like and absorbent such that, when the rubber pieces are mixed with the cement, the fibres draw in a suspension of the cement in water and help to interlock adjacent rubber pieces as the material cures. This interlocking or bonding of the rubber pieces creates a stronger material compared to a material containing rubber without fibres or rubber containing non-absorbent fibres. The fibre embedded rubber pieces are preferably obtained from chopped up or shredded car tyres and, accordingly, the fibres are preferably made from polyester or nylon. The small particle size aggregate of the material preferably has a particle size of less than 2 mm. In preferred embodiments the aggregate is sand. In other embodiments the aggregate may be made from a glass material, a plastics material or another small particle size material such as crushed stone or flyash.

The material used to form the anti-ballistic wall comprises the rubber pieces embedded with fibres and cement in a ratio of between 3: 1 and 8: 1 of their dry volume and cement and aggregate in a ratio of between 1 : 1 and 1 :2 of their dry volume. Preferred embodiments of the material, therefore, comprise 55-80% by volume rubber pieces embedded with fibres, 8-25% by volume cement and 10- 23% by volume small particle size aggregate, when the components are in a dry state, i.e. before being mixed with water. Preferably the small particle size aggregate is sand.

By increasing the ratio of cement to rubber, the strength of the material can be increased to withstand larger munitions. In particularly preferred embodiments the material comprises 55-65% by volume rubber pieces embedded with fibres, 18- 25% by volume cement and 10-23% by volume sand.

Some example materials are listed in Table 1 below.

Table 1

Volume % dry state

Cement Rubber pieces Sand

embedded with fibres

9 73 18

20 60 20

16.67 66.66 16.67

12.5 75 12.5

14.28 71.44 14.28 The anti-ballistic structure of the present invention may include a single skin wall or a double skin wall. The thickness of the or each skin of the wall is preferably between 200 mm and 600 mm, and more preferably between 200 mm and 400 mm.

In embodiments comprising a single skin wall 100, such as that illustrated in Figure 1 , the wall 100 is preferably made from a material comprising about 20% by volume cement, about 60% by volume rubber pieces embedded with fibres and about 20% by volume sand, when the components are in a dry state. It has been shown by the applicant that a wall 100 constructed from this material and having a thickness of about 300 mm is able to prevent penetration of a 7.62 mm calibre armour piercing bullet in accordance with level 2 of NATO Standard STANAG 4569. In embodiments comprising a double skin wall 200, such as that illustrated in Figure 2, the wall 200 preferably comprises a cavity 202 between the two skins 204, 206. The cavity 202 preferably has a thickness of between 50 mm and 100 mm. The cavity 202 will, in general, be an air cavity and will not be filled with another material. The cavity 202 will, however, typically be sealed or blocked at ends of the wall or structure 200 to prevent any ammunition that is caught within the cavity 202 exiting from the ends.

In embodiments comprising a double skin wall 200, at least one of the skins 204, 206 is preferably made from a material comprising at least 16% by volume cement, at least 16% by volume sand and no more than 72% by volume rubber pieces embedded with fibres, when the components are in a dry state. More preferably, at least one of the skins 204, 206 is made from a material comprising between 16% and 25% by volume cement, between 16% and 23% by volume sand and between 55% and 72% by volume rubber pieces embedded with fibres, when the components are in a dry state. It has been shown by the applicant that a wall 200 constructed in this way, with each skin 204, 206 having a thickness of about 300 mm and the cavity 202 having a thickness of about 60 mm, is able to prevent penetration of a 14.5 mm calibre armour piercing bullet in accordance with level 4 of NATO Standard STANAG 4569.

In one preferred embodiment both skins 204, 206 of a double skin wall 200 are made from a material comprising between 16% and 18% by volume cement, between 16% and 18% by volume sand and between 65% and 70% by volume rubber pieces embedded with fibres, when the components are in a dry state.

In another preferred embodiment both skins 204, 206 of a double skin wall 200 are made from a material comprising between 18% and 22% by volume cement, between 18% and 22% by volume sand and between 55% and 65% by volume rubber pieces embedded with fibres, when the components are in a dry state.

To aid in the ease of construction of the anti-ballistic structure, the wall or walls 100, 200 are preferably constructed from pre-cast blocks 8 of the rubber and cementitious material. The dimensions of the blocks 8 are preferably 300 mm x 300 mm x 200 mm so that they may be easily handled and manipulated by a person. The nature of the material used to form the blocks 8 is such that the surface of the blocks 8, as well as the internal volume, comprises voids and recesses between the rubber pieces. The surfaces of the blocks 8 are, therefore, relatively rough.

The blocks 8 may be joined or bonded together using any known means or materials, such as those used to bond traditional bricks or concrete blocks. The blocks 8 may be bonded together using cement mortar 10, an adhesive or any other suitable bonding material or compound. Due to the rough surface texture of the blocks 8, the mortar 10 or adhesive will tend to at least partially penetrate into the surface voids and recesses. This helps to bond the blocks 8 more securely together within a wall 100, 200.

It is envisaged that a suitable pallet or container may be loaded with a plurality of blocks and a bag of ready-mix cement mortar or other bonding material, and that this pallet may then be transported to the required site of the anti-ballistic structure. Due to the non-metallic and, therefore, relatively lightweight nature of the blocks, transportation of the construction materials is relatively easy.

Typically the blocks 8 will be generally rectangular or cuboidal having opposing first and second supporting faces 12, opposing first and second end faces 14, and opposing first and second side faces 16. It will be appreciated, however, that any size or shape of block may be used to construct the wall.

In some embodiments, in which a stronger or more robust wall is required, the blocks 8' include a hole 18 that extends through the full thickness of the block 8' between the first and second supporting faces 12' and recesses 20 in the first and second end faces 14'. Each of these recesses 20 also extends for the full thickness of the block 8' between the first and second supporting faces 12'. An example of such a block 8' is illustrated in Figure 4.

The holes 18 have a generally circular cross sectional shape and each of the recesses 20 has a generally semi-circular cross sectional shape, and the length of the radius of the hole 18 is equal to the length of the radius of each of the recesses 20. Furthermore, the hole 18 is centrally located in the block 8' such that a distance between the recess 20 in a first end face 14' and the hole 18 is equal to the distance between the recess 20 in a second end face 14' and the hole 18. To construct a wall 300 using these blocks 8', the blocks 8' are laid end to end such that opposing end faces 14' of neighbouring blocks 8' are in touching contact with each other. The blocks 8' are butted up against each other with no mortar or other joining compound between the end faces 14'. With the blocks 8' positioned in this way, the recesses 20 of adjoining end faces 14' are aligned to form a single space or channel extending through the layer of blocks 8'. In this example, because each of the recesses 20 has a substantially semi-circular cross sectional shape, the resultant channel has a substantially circular cross sectional shape. Once the first layer of blocks 8' has been laid, a second layer of blocks 8' is laid directly on top of the first layer of blocks 8'. Again, no mortar or other jointing compound is used and the second supporting faces 12' of each of the blocks 8' of the second layer are, therefore, in direct touching contact with the first supporting faces 12' of the blocks 8' of the first layer.

The position of the blocks 8' of the second layer are staggered with respect to the blocks 8' of the first layer, such that the recesses 20 in the end faces 14' of the blocks 8' of the second layer are vertically aligned with the holes 18 in the blocks 8' in the first layer. Similarly, this means that the holes 18 in the blocks 8' of the second layer are also vertically aligned with the recesses 20 in the end faces 14' of the blocks 8' of the first layer. Further layers may then be added to the wall 300 in a similar manner to the second layer, with each of the layers being staggered with respect to the layer below, until the wall 300 is of the desired height. The blocks 8' are then bonded together by pouring or injecting a cementitious material or similar into vertical columnar channels 22 formed by the aligned holes 18 and recesses 20 formed in the wall 300. This cementitious material fills the columnar channels 22 and acts to securely bond or key the blocks 8' together.

The columnar channels 22 may be filled with cement grout, concrete, a geopolymer material, a mixture comprising cement and rubber, or any other similar material. The material used to fill the channels 22 may additionally include steel or plastic fibres. Furthermore, reinforcing bars (rebar) may be positioned to extend through the channels 22 to further strengthen the wall 300.

Constructing a wall 300 in this way creates a stronger structure than that achieved by bonding individual blocks 8 together with mortar 10 between them. Additionally, it may be quicker to erect a wall in this way, as the blocks 8' are dry stacked and then the cementitious material is poured through the channels 22 in the completed wall. As such, the wall already offers some level of protection before the construction process is completed.

In some embodiments the anti-ballistic structure may include one or more cladding panels 30 affixed to one or both faces of a wall 400, as illustrated in Figure 3. The cladding panels 30 are, preferably, also made from a material comprising rubber with embedded fibre and small particle aggregate in a cement matrix. The panels 30 may additionally include a geogrid 32 or layer of geofabric embedded within the cementitious material to improve the tensile and flexural strength of the panels 30.

The panels 30 have a thickness of between 100 mm and 200 mm. The height and width of the panels 30 are preferably such that a single panel 30 covers the faces of a plurality of blocks 8, 8' in a wall. A panel 30 may, for example, be about 800 mm by 1500 mm. The panels may be attached to an existing wall using any suitable fixing means, such as brackets or bolts. In a preferred embodiment, corner brackets or attachment plates are provided on the panel. These brackets or plates will typically be made from a plastics material such as high density polyethylene or a metallic material such as steel. In other embodiments the panels 30 may be freestanding, i.e. not secured to an existing wall, to provide stand alone screens.

Although in the preceding description the construction material used to form the blocks, the panels and the walls has been described as consisting essentially of rubber embedded with fibre, and sand, in a cement matrix, in some embodiments the material may additionally include one or more of the following components: flyash, geopolymer, glass, steel fibres and plastic particles.

Furthermore, it will be appreciated that the anti-ballistic walls may be formed or cast in situ, rather than being built from pre-cast blocks.

The anti-ballistic structures according to the present invention have many advantages over prior art structures including ease of construction, durability and a lower weight than conventional steel-based structures of an equivalent level of protection. The present invention, therefore, provides improved anti-ballistic structures which, in particular, do not include steel plate.

Claims

1 . An anti-ballistic structure including a wall made from a material comprising rubber pieces with embedded fibres in a cement matrix, the volume ratio of said rubber pieces and cement in a dry state is between 3: 1 and 8: 1 .

2. An anti-ballistic structure as claimed in Claim 1 , wherein the material further comprises an aggregate having a particle size of less than 2 mm.

3. An anti-ballistic structure as claimed in Claim 2, wherein the aggregate is sand.

4. An anti-ballistic structure as claimed in Claim 3, wherein the volume ratio of sand and cement, in a dry state, is between 1 : 1 and 2: 1 .

5. An anti-ballistic structure as claimed in Claim 3 or Claim 4, wherein the material comprises, in a dry state, 55-80% by volume rubber pieces with embedded fibres, 8-25% by volume cement, and 10-23% by volume sand.

6. An anti-ballistic structure as claimed in any preceding claim, wherein the wall is a single skin wall.

7. An anti-ballistic structure as claimed in Claim 6, wherein the material comprises, in a dry state, 55-65% by volume rubber pieces with embedded fibres, 18-22% by volume cement, and 18-22% by volume sand.

8. An anti-ballistic structure as claimed in Claim 6 or Claim 7, wherein the thickness of said single skin is between 200 mm and 600 mm.

9. An anti-ballistic structure as claimed in any one of Claims 1 to 5, wherein the wall is a double skin wall with a cavity between said skins.

10. An anti-ballistic structure as claimed in Claim 9, wherein the material from which at least one of the walls is made comprises, in a dry state, 55-72% by volume rubber pieces with embedded fibres, 16-25% by volume cement, and 16- 23% by volume sand.

1 1 . An anti-ballistic structure as claimed in Claim 9 or Claim 10, wherein the cavity has a thickness of between 50 mm and 100 mm.

12. An anti-ballistic structure as claimed in any one of Claims 9 to 1 1 , wherein the thickness of each of the two skins is between 200 mm and 400 mm.

13. An anti-ballistic structure as claimed in any preceding claim, wherein the wall is constructed from pre-cast blocks of said material.