FIELD OF THE INVENTION

The present invention relates to a concrete material, a method of producing such a concrete material and uses thereof.

BACKGROUND OF THE INVENTION

Concrete is extensively used worldwide for building durable structures. It is further commonly used in industrial applications in rather harsh conditions, such as for industry flooring, and in furnaces where it is exposed to high temperatures. A problem with concrete materials used for high temperature applications, such as in furnaces, incinerators or chimneys, is that they are often cumbersome to install and require long downtimes for maintenance in case replacements are needed due to for example cracking, or loss of mechanical properties of the material over time.

A problem with concrete materials used in industrial environments handling combustible liquids is that is that, although concrete per se might be fire-resistant, extinguishing a fire due to ignited combustible liquids spilled thereon is difficult. This since the lighter density and different polarity of such liquids with respect to water causes the ignited liquid to flow on top of the surface of water which might be applied thereto to extinguish the fire, whereat it continues to burn.

SUMMARY OF THE INVENTION

It is an object of the present invention to overcome or at least alleviate some of the above mentioned drawbacks. A particular object is to provide a concrete material with improved fire resistance and reduced weight. It is a further object of the invention to provide a method of producing such a concrete material.

To better address this concern, in a first aspect of the invention there is presented a concrete material having a density of 800-2200 kg/m ³ and an air pore volume of at least 10 %, which concrete material comprises fired ceramic particles as aggregate material.

This provides a fire resistant and relatively light concrete material, with the density of 800 to 2200 kg/m ³ , which is able to withstand high temperatures without deteriorating. The structure of the concrete material, having an air pore volume of at least 10 %, allows liquids applied thereto, or spilled thereon, to be absorbed in the material, i.e. to enter the air pores and travel there through. The fired ceramic particles of the concrete material can further absorb liquids with which it comes into contact. Thus, if an inflammable liquid, such as for example gasoline, diesel or other chemicals, is spilled on the concrete material, for example when used as industrial flooring, such liquid is absorbed by the air pores and the aggregate material of the concrete material. Should the inflammable liquid ignite and a fire break out, the fire could easily be extinguished with water when sprayed in such an amount that a layer of water covers the fire affected area. As water covers the concrete material, air pores are obstructed whereby no air enters the interior structure and reaches the ignited liquid, thus eliminating air supply to the fire. When the air supply to the fire is eliminated, the fire is extinguished. Should a fire break out at the concrete material due to a combustible liquid spilled thereon, it can thus easily and efficiently be extinguished with water. It is generally hard to extinguish a fire caused by an ignited combustible liquid with water, as such liquids tend to flow on top of the water and remain on fire. The inventors surprisingly found that this behavior of combustible liquid can be prevented with a concrete material as disclosed herein, providing a great advantage in terms of fire resistance thereof.

A further advantage of the concrete material having an air pore volume of at least 10 %, is that it provides an insulating material considering that the air pores do not conduct heat.

Yet another advantage of the concrete material is its resistance to high temperatures, provided by the fired ceramic particles. This allows the concrete material to withstand high temperatures, such as from 1100 to 1500 °C, without deteriorating in terms of, for example, cracking, chipping, exploding, or suffering major losses of mechanical properties following exposure to high temperatures. Using fired ceramic particles as aggregate material provides stability to the material when heated, since fired ceramic particles present little to no expansion upon exposure to high temperature. It further allows using recycled material, considering that used fired ceramic objects may be crushed into particles and thereafter reused as fired ceramic particles. Undoubtedly, this presents a benefit for the environment.

Herein, the term “fired ceramic particles” refers to materials of clay and/or ceramics which have been fired at high temperatures. The term is intended to denote all fired clay and ceramic wares, including but not limited to pottery, technical, structural, and refractory products. The term also denotes volcanic rock or sand particles, which have effectively been fired at high temperature when generated in a volcanic eruption. The particles may have a size which ranges from tenths of a millimeter to several centimeters.

The term "aggregate materials" as referred to herein refers to a particulate material which may be added to the concrete mixture in order to control the density of the concrete material.

In a preferred embodiment, the air pore volume is between 10 and 60 %. This provides a good compromise between mechanical stability, absorption capacity and light weight of the concrete material. A density of between 800 and 2200 kg/m ³ provides a relatively light yet mechanically strong concrete material, which eases handling thereof. In some examples, the concrete material has a density between 900 and 2000 kg/m ³ , preferably between 1000 and 1800 kg/m ³ . Densities closer to 800-1000 kg/m ³ are preferable when a higher air pore volume of the concrete material is desired, allowing the material to absorb a substantial amount of liquids. At the other end, densities closer to 1800-2200 kg/m ³ are preferable when higher mechanical stability of the concrete material is desired. The fired ceramic particles absorb liquids at all densities. The amount of liquid which can be absorbed by the fired ceramic particles depend on the particle size.

Generally, volcanic sand particles can absorb liquid up to around 30 % of its own weight.

The concrete material is generally made from a cured concrete mixture comprising water, cement, an air pore forming agent and fired ceramic particles as aggregate material. This provides a fire-proof concrete material. The cement of the concrete material may be Portland cement or a mixture of Portland cement and a refractory cement. The concrete material comprising Portland cement as cement can generally withstand temperatures up to around 700 °C. Portland cement is preferably used owing to its good all-round properties. Portland cement comprises tricalcium silicate, tricalcium aluminate and calcium aluminium ferrite. Other examples of suitable types of cement to be used are Portland blast-furnace cement, white Portland cement, low-heat Portland cement and rapid-hardening Portland cement, which are all based on Portland cement clinker.

The addition of a refractory cement, such as calcium aluminate cement, to the Portland cement allows accelerating the hardening process of the concrete mixture the addition of a refractory cement also provides an increased temperature resistance of the concrete material.

In an embodiment, the cement of the concrete material is a mixture of Portland cement and at least 60 % by weight of a refractory cement with respect to the total amount of cement in the concrete material. Providing a mixture of Portland cement and the refractory cement increases the temperature resistance of the concrete material. As an example, such a concrete material, comprising a mixture of Portland cement and at least 60 % by weight of a refractory cement, can resist temperatures up to 1500 °C.

According to an embodiment of the concrete material, the refractory cement is a calcium aluminate cement. Such a calcium aluminate cement may for example be known under the commercial names SECAR ^® and TERNAL ^®

According to an embodiment of the concrete material, the cement of the concrete material comprises at least 80 % by weight of a refractory cement, with respect to the total amount of cement in the concrete material. This provides a higher resistance of the concrete material to high temperatures, while maintaining a considerably low cost of the same.

According to an embodiment of the concrete material, the cement of the concrete material is a refractory cement. For producing such a concrete material, a starter is generally needed in order to initiate the chemical reactions of the concrete mixture.

According to an embodiment, the concrete material has an air pore volume of at least 15 %, such as of at least 20 %, preferably of at least 25 %.

It is contemplated that the amount of liquid the concrete material can absorb relates in part to the air pore volume, and in part to the amount of liquid absorbable by the fired ceramic particles.

According to an embodiment, the air pore forming agent is a tenside. A suitable tenside generates air pores of the concrete material which are surrounded by the cement and wet the aggregate material, thereby creating a bond between the cement and the aggregate material, here the fired ceramic particles. The tenside may be of ionic or non-ionic type. Examples of tensides of ionic type are anionic tensides and cationic tensides. Examples of tensides of non-ionic type are ethylene oxide adducts, such as non-ionic tensides obtained by adding ethylene oxide to linear secondary alcohols having alkyl carbon atoms ranging between 10 and 14. Such non-ionic tensides may be known under the commercial names Softanol ^® (80, 90, 100 or 120) or Surfonyl ^® (500 or 600). Tensides with similar molecular chains and structure are also possible within the inventive concept. The air pore forming agent may alternatively be a melamine resin or a protein-based air pore forming agent made up of protein and synthetic additives.

According to an embodiment of the concrete material, the fired ceramic particles are selected from at least one of crushed bricks, tiles, clay products, pottery, earthenware, clinkers, lightweight expanded clay aggregates and volcanic rocks. This allows using recycled material in the production of the concrete material, which is advantageous both from an environmental and an economic perspective. With respect to volcanic rocks, this is a material which is naturally available in large quantities and for which no extensive use has yet been found. As used herein, the terms “volcanic rock” and “volcanic sand” refers to sand and rock that has been formed from lava erupted from a volcano. In an embodiment, the volcanic sand comprises grains of the glassy rock type obsidian comprising basalt. Particularly, particles of volcanic rock have been considered unsuitable as aggregate material for forming a concrete material due to the particles being porous and therefore having a poor mechanical strength per se. However, the inventors have surprisingly found that when provided as aggregate material in a concrete material as herein defined, these particles are wetted and adhere well to the cement, leading to a concrete material with high mechanical strength and temperature resistance.

According to an embodiment of the concrete material, the fired ceramic particles have a particle size which is less than 20 mm, preferably less than 12 mm, more preferably less than 6 mm. The term “particle size” refers to that the particles are able to pass through a sieve having the corresponding mesh size. That is, particles having a particle size of less than 20 mm are able to pass through a sieve having mesh size of 20 mm. Generally, the particle distribution curve of the aggregate material is chosen depending on the application of the concrete material. For a concrete material cast in thin layers, a smaller particle size is desired. In an embodiment of the concrete material having a thickness of 10 mm, the maximum particle size is around 3 mm. In another embodiment, the concrete material having a thickness of 3 mm comprises fired ceramic particles with a maximum particle size of around 1 mm. It is generally preferable that the size of the fired ceramic particles is three times less than the desired thickness of the concrete material. Furthermore, in order to provide a good compromise between mechanical stability and absorption with respect to the density of the concrete material, a maximum particle size of the fired ceramic particles of 20 mm is preferred. Fired ceramic particles of this size provide a large surface for absorbing liquid. For a concrete material of greater thickness, it is however possible to use larger particles.

According to an embodiment of the concrete material, the fired ceramic particles are fine grained, having a particle size of 0.05 to 2 mm. Providing fired ceramic particles in that particle size range, preferably with an even particle size distribution, allows providing the concrete material in a layer of a thickness between 0.5 and 5 mm. Preferably, in order to provide mechanical strength and a smooth, thin layer, the thickness of the concrete material is three times that of the particle size. Advantageously, such concrete material is applicable in thin layers to a surface before it hardens. Thus, the concrete material can be provided in the form of a paste, such as e.g. a putty, which is spreadable onto a surface in thin layers whereat it is allowed to harden. The spreadable concrete material can e.g. be applied to plaster or wooden walls or surfaces to provide flame resistance of the same. This is a very efficient way of providing flame resistance of a surface, both in terms of cost and in terms of handling and/or installation.

According to an embodiment of the concrete material, the concrete material further comprises a hydrophobic agent. The hydrophobic agent causes the concrete material to repel water rather than absorbing it. The hydrophobic agent thus further enhances the ability of the concrete material to be extinguished in case of a fire due to ignited combustible liquids spilled thereon, considering that water applied thereto will not be absorbed by the concrete material.

The hydrophobic agent may be a synthetic or natural resin, or derivatives thereof, having molecular weights of usually below 10,000 and a saponification number of 100-250. Such a resin may be at least partially soluble in the concrete mixture, preferably substantially fully soluble in the concrete mixture. The resin may have a viscosity (Brookfield, 25 degrees C,

50 rpm, cps) in the range of 400-1200, such as 600. The resin may be added as a dispersion having a pH in the range of 8.0-9.5, such as 8.5. The resins and their derivatives may comprise one or more aromatic and/or aliphatic groups having at least 10, preferably 16-35 carbon atoms. The groups may be saturated or unsaturated. Preferred resins are such having an acid number from 10-25, such as 20 and a saponification number from 150 to 175. Examples of suitable resins are various resin acids and mixtures thereof, such as colophonium, and their dimerised derivatives and wholly or partly esterified and/or hydrated derivatives thereof. The resin may be a tall oil rosin. The resin may be a polymer.

According to an embodiment of the concrete material, the concrete material has a thickness of at least 2 mm. This means that the concrete material can be applied as thin blocks, for example as an outermost protection or sacrificial layer within a furnace. The thickness of the concrete material can further be adapted to the requirements posed on its different fields of application. The concrete material can be used as a fire delimiting element, for example for flooring, furnaces, high temperature transportation compartments, and buildings. More particularly, the concrete material can for example be provided as panels used as fire delimiting wall elements in buildings. The concrete material can also be used as sacrificial panels in incinerators to protect the masonry wall. Due to the light weight and cost of the concrete material, it can easily be replaced when needed, providing shortened down times of the incinerator for maintenance of this kind. Additionally, due to the high temperature resistance of the concrete material, the temperature of the incinerator using the concrete material as sacrificial panels may operate at higher temperatures, such as at 1400 °C at which e.g. dioxins are dissolved, thereby preventing emissions of the same from the incinerator to the air.

According to an embodiment of the concrete material, the concrete material comprises a reinforcing element, such as carbon fibres. Such a reinforcing element provides increased mechanical strength of the concrete material.

According to an embodiment of the concrete material the concrete material can absorb at least 200 ml inflammable liquid per square meter, thereby allowing a fire in said inflammable liquid to be extinguished by water being sprayed or poured on the concrete material. The inflammable liquid may be gasoline, diesel or other inflammable chemicals, such as oils of different kinds. Preferably, the concrete material should be able to absorb at least 250 ml, such as at least 300 ml, preferably at least 400 ml inflammable liquid per square meter, when the concrete material is used as e.g. a flooring material. In particular, it is capable of absorbing the above amount of liquid when said liquid is being spilled on the floor. Thus, should the inflammable liquid ignite and a fire breaks out in the spilled liquid, the fire could easily be extinguished with water when sprayed in such an amount that a layer of water covers the fire affected area on the concrete floor. As water covers the concrete material, air pores are obstructed whereby no air enters the interior structure and reaches the ignited liquid, thus eliminating air supply to the fire. When the air supply to the fire is eliminated, the fire is extinguished.

In accordance with a second aspect of the invention, there is provided a method of producing a concrete material having a density of 800-2200 kg/m ³ and an air pore volume of at least 10 %. The method comprises the steps of providing water, an air pore forming agent, cement and aggregate material to a mixer; agitating the added ingredients while entraining air to form a homogeneous, stable, air-containing concrete mixture; and curing the concrete mixture, thereby forming the concrete material having a density of 800-2200 kg/m ³ and an air pore volume of at least 10 %, wherein the aggregate material is composed of fired ceramic particles.

The method allows producing the concrete material with a density of 800-2200 kg/m ³ and an air pore volume of at least 10 % which is resistant to high temperatures. The method is further advantageous as it allows producing the concrete material on site or prefabricate the concrete material for posterior delivery to the installation site. The method allows casting the concrete material vertically or horizontally.

The air pore forming agent may be a tenside of a non-ionic, cationic or an anionic type. The air pore forming agent may, in other embodiments, be a melamine resin or a protein-based air pore forming agent made up of protein and synthetic additives, as discussed with regards to the first aspect of the invention.

According to an embodiment, the fired ceramic particles are selected from at least one of crushed bricks, tiles, clay products, pottery, earthenware, clinkers, light weight expanded clay aggregates, and volcanic rocks. Such fired ceramic particles are inert during the curing of the cement mixture and has, thus, no accelerating effect on that stage of the production method of the concrete material.

According to an embodiment, the ratio, by weight, of cement to aggregate material is in the range of 0.8-1.2 : 0.8-1.2. In these proportions, the aggregate material and the generated air pores are surrounded by cement, providing mechanical strength to the concrete material, The air pores surrounded by cement further provides a good absorption capacity of the concrete material.

According to an embodiment, the method comprises the step of providing a hydrophobic agent to the mixer to form part of the concrete mixture. This provides hydrophobic properties to the produced concrete material, enhancing the ability of the material to be extinguished with water in case of a fire due to ignited combustible liquids absorbed by the material. Examples of hydrophobic agents used are discussed with reference to the first aspect of the invention.

According to an embodiment, the concrete material obtained by the method has a density of 1000-1800 kg/m ³ . The provision of different constituents of the concrete material, i.e. the amount of cement, aggregate particles, air pore forming agent and eventual additives are adapted to the desired density of the concrete material. A density of between 1000 and 1800 kg/m ³ is particularly preferred in view of the combination provided of absorption capacity, weight and mechanical strength of the concrete material.

According to an embodiment, the aggregate material is damp when provided in the mixer. According to another embodiment, the aggregate material is dry when provided in the mixer. That is, the aggregate material can be provided either damp or dry. It may be advantageous to provide the aggregate material damp in order to avoid particle contamination of the air in the working environment.

According to an example, the method further comprises a step of wetting the aggregate material before provision to the mixer. The wetting is preferably performed by pouring water over the aggregate material under stirring of the aggregate material.

According to an embodiment, the aggregate material, instead of being provided in the mixer together with water, the air pore forming agent and cement, is provided to the homogeneous, stable, air-containing concrete mixture formed after agitating the aforementioned constituents. Also in this example, the aggregate material may be provided damp or dry to the concrete mixture. In accordance with a third aspect of the invention, there is provided a use of a concrete material as disclosed herein. According to an embodiment, there is provided a use of a concrete material as disclosed herein as a fire delimiting element, such as for flooring, walls, furnaces, high temperature transportation compartments, and buildings. The use of the concrete material in such applications is advantageous due to its resistance to high temperatures and capacity to be extinguished in case it is ignited as discussed herein. Further advantages with the use of the concrete material in such applications are ascribed the light weight, low cost and convenient production method thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail and with reference to the appended drawings, in which:

Figs. 1a-c show schematic illustrations of a floor of a standard concrete material; and

Figs. 2a-c is show schematic illustrations of a floor made of an embodiment of a concrete material according to an aspect of the invention.

DESCRIPTION OF EMBODIMENTS

The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplifying embodiments of the invention are shown. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness, and to fully convey the scope of the invention to the skilled addressee.

Referring to Figs. 1a-c, a scenario for an industry floor made of a standard concrete material 10 is illustrated. In Fig. 1a, combustible liquid 2, such as for example gasoline or diesel, has been spilled onto the standard concrete floor 10. If the combustible liquid 2 ignites, a fire breaks out and water 3 can be applied to the floor in an attempt to extinguish the fire, see Fig. 1 b. Due to the nature of the combustible liquid 2, generally having a lower density and different polarity with respect to water 3, the combustible liquid 2 flows on the surface of the water 2 where it continues to burn. Therefore, the fire is difficult to extinguish.

Referring to Figs. 2a-c, a similar scenario for an industry floor is illustrated where the industry floor is made of a concrete material 1 having a density of 800-2200 kg/m ³ and an air pore volume of at least 10 %, the concrete material comprising fired ceramic particles as aggregate material and at least 60 % by weight of a refractory cement, with respect to the total amount of cement in the concrete material. In Fig. 2a, a combustible liquid 2 is spilled onto the concrete material 1. In case the combustible liquid 2 ignites, water 3 is applied to the floor of concrete material 1 in Fig. 2b. Due to the structure of the concrete material 1 , having an air pore volume of at least 10 %, the combustible liquid is absorbed in the in the concrete material 1, see Fig. 2c. The water 3 applied to the surface of the concrete material 1 forms a layer on top of the same, obstructing the air pores, whereby no air enters the pores and to the ignited liquid 2. The fire is thereby efficiently extinguished.

Examples

Example 1. Production of a concrete material for fire delimiting applications

For producing a concrete material suitable for use in fire delimiting applications, the following step-wise procedure took place. Into a laboratory mixer, 200 g of standard Portland cement, 800 g of refractory cement sold under the trade name SECAR ^® 71 and 1000 g of crushed brick particles having a particle size between 4 pm - 3 mm was added. Thereafter, 700 g of water, 3.5 g of an air pore forming agent and 5 g of a hydrophobic agent, previously mixed, was added to the mixer. The mixture was agitated while entraining air resulting in the formation of a homogeneous, stable, air- containing concrete mixture. The concrete mixture was casted in a mold to obtain a shape which is suitable for fire delimiting applications, and allowed to harden. The density of the produced concrete material was 1400 kg/m ³ . Example 2. Production of a concrete material for fire delimiting applications

For producing a concrete material suitable for use in fire delimiting applications, the following step-wise procedure took place. Into a laboratory mixer, 200 g of standard Portland cement, 800 g of refractory cement sold under the trade name SECAR ^® 71 and 1000 g of crushed brick particles having a particle size between 4 pm - 3mm was added. Thereafter, 640 g of water, 3.3 g of an air pore forming agent and 3.3 g of a hydrophobic agent, previously mixed, was added to the mixer. The mixture was agitated while entraining air, resulting in the formation of a homogeneous, stable, air- containing concrete mixture. The concrete mixture was casted in a mold to obtain a shape which is suitable for fire delimiting applications, and allowed to harden. The density of the produced concrete material was 1740 kg/m ³ .

Example 3. Fire extinguishing test

The concrete material produced according to Example 1 was used in a fire extinguishing test. A block of the concrete material having a size of 350 x 350 x 50 mm with an edge around the periphery of the upper surface, referred to as block A, was arranged next to a block of a standard Portland cement of grade K400 having the same size and geometry, referred to as block B, with a space there between. 100 ml of gasoline was poured onto each of the two concrete blocks. The edges around the periphery of the respective upper surfaces assured that the gasoline did not flow along the outer sides of the block. After 60 s, block A and block B were ignited by means of a lighter. After another 60 s, during which both block A and block B were on fire, two bottles with a volume of 330 ml containing water was used for pouring water onto each of the two blocks, i.e. one bottle was used for block A and one bottle was used for block B. The fire of block A was extinguished immediately, before the content of the bottle was emptied. The fire of block B was extinguished 60 s after the entire content of the bottle had been poured thereon.

The test clearly shows that the concrete material disclosed herein presents high fire delimiting capacity. Example 4. Production of a flame proof concrete material in form of a paste For producing a concrete material suitable for being provided as a paste and spread onto a surface whereat it is allowed to harden for providing flame resistance of the surface, the following step-wise procedure took place. Into a laboratory mixer, 800 g of cement and 2000 g of fine grained volcanic rocks, having a particle size of 0.1-1 mm, was added and mixed to form a dry mixture. Into a container, 875 g of water was added. Thereafter, 2.5 g of an air pore forming agent and 3.5 g of a hydrophobic agent was added to the water, forming a liquid mixture. Subsequently, approximately 70 % of the liquid mixture was added to the dry mixture in the laboratory mixer forming a concrete mixture. The concrete mixture was agitated. More liquid mixture was thereafter added until a desired density and consistency of the concrete mixture paste was obtained. The skilled person realizes that a number of modifications of the embodiments described herein are possible without departing from the scope of the invention, which is defined in the appended claims. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. Any reference signs in the claims should not be construed as limiting the scope.