Conventionally, concrete is used for different types of constructions. One specific concrete mixture comprises at least cement, ballast material, and reinforcement. The cement might for example be Portland cement. It is also previously known, e.g. through US 2014/0275349 Al, to use a cement mixture partly consisting of pozzolanic material, such as fly ash, which can provide a cement having good qualities in terms of, among other things, wear resistance and resistance against freezing and attacks from acids and chlorides.

Rods made from iron or steel can be used as reinforcement. It is also previously known to use fibrous reinforcement materials. One example is using mineral reinforcement materials, such as basalt.

In order to obtain the desired properties, such as compression strength, flow, and resistance against cold and heat of the concrete, the composition of the cement and the ballast and their properties might be varied. Further, different additives might be added to the concrete mixture. Such additives might for example increase the flow of the concrete, or might make the concrete self-compacting ("SCC"), which entails that less vibration is needed for the concrete to completely fill out a casting mould. Examples of additives comprise hydrated lime, limestone, chalk, talc, slag or clay, and various conventional synthetic additives.

Since different types of cement have different properties under different conditions, where the properties moreover might vary depending of for example pressure, temperature and dilatation, further, since different types of reinforcement involve different types of modified properties of the concrete, and since, because further different additives involves further changes of the properties of the concrete, there is a very large number of different, possible concrete mixtures, each having quite different properties over a number of different variable parameters, such as compression strength, resistance against different types of external influence, elasticity, cracking tendencies, ageing resistance, pollution load, energy demand during manufacture, being possible to recycle, and so on. It is a special problem that the manufacture and recycling of constructive elements made from concrete put a lot of strain on the environment, especially by exhaust of carbon dioxide but also of substances being more direct environmentally harmful substances. In many cases it is desirable to provide constructive elements with increased strength, enhanced corrosion resistance, and so on.

Accordingly, different constructive elements, which are manufactured from different concrete mixtures will get very different properties.

In a first aspect, the invention provides a particularly advantageous concrete mixture to be used in demanding applications and at a low total cost and with a small environmental load. The concrete mixture comprises cement, pozzolanic material, ballast, water and additives, and basalt fibers for reinforcement.

According to one embodiment, the concrete mixture comprises pozzolanic material in an amount, which amounts to at least 50 % dry weight, preferably between 75 % and 82 %.

According to another embodiment, the amount of basalt fibers amounts to between 0.1 % to 4 % dry weight. Preferably, the basalt fibers have been treated with polymer. Further advantages will be achieved if the basalt fibers are assembled in bundles. The basalt fiber bundles will have the best adhesion to the concrete when a basalt fiber is helicoidally wound around the bundle.

The basalt fiber bundles are between 5 and 60 mm long, preferably between 15 and 50 mm long, and most preferred between 20 and 46 mm long. The circumference of the basalt fiber bundles is between 0.5 and 1.0 mm, preferably between 0.6 and 0.8 mm. Preferably, the polymer has a melting point above 400 degrees Celsius, preferably above 475 degrees Celsius. The basalt fiber bundles according to the above are marketed under the trade names

Minibars™ and Basbars™.

According to a second aspect a sandwich element is provided, such as a wall element to be used in a house, having a substantially reduced total cost for manufacture and mounting, as well as considerably less environmentally load. The sandwich element comprises an exterior element, an insulating layer, and an interior element, whereby the exterior element and the interior element are accomplished with the inventive concrete mixture. According to one embodiment an exterior element is accomplished having a thickness between 35 and 50 mm, preferably between 40 and 45 mm. According to a further embodiment an interior element is

accomplished having a thickness between 70 and 95 mm, preferably between 80 and 85 mm. In a preferred embodiment an interior element is accomplished for temporary buildings, such as for example emergency housings, wherein the interior element rather is between 30 and 50 mm. Such thin inner walls will have sufficient bearing capacity for this kind of application, when the novel concrete mixture according to the invention is used. According to a third aspect a pylon is accomplished for use in installations of for example electric systems, providing higher flexibility for different substantial applications at a lower cost and lower environmental load, and which also have higher bearing capacity, when an inventive concrete mixture is used.

The possible combinations are not obvious, but instead demand extensive knowledge about the properties of the different materials and regarding construction/composition.

With the concrete based on fly ash, which is manufactured by VHSC in Houston Texas, according to US 2014/0275349 Al, some of these properties are supplied with the cement, and therefore some types of additives can be omitted while at the same time the cement in itself make possible a substantial decrease of the amount of cement, i.e. about 50 % less, in order to obtain the same concrete quality as before.

By adding basalt fiber reinforcement to the above mentioned cement, preferably in fiber bundle form, such as those marketed under the trade names Minibars™ and Basbars™, a number of receipt combination possibilities result, which affects cost, environment, weight, working life, resistance against chlorides, etc. The possible receipt combinations are non-obvious but instead a very good understanding of the properties of the materials is necessary. The basalt fiber bundles, such as Minibars™, act in a different way compared to steel fibers and plastic fibers. Steel and plastic fibers do not act until the concrete starts to crack (shrinkage and micro cracks), while basalt fiber bundles, such as Minibars™, counteract these cracks already because of their strong adhesion in the concrete. Hereby an almost completely crack-free concrete is obtained, which might be said to be more dense and thereby less susceptible to let chloride and sulfate ions through. Some different receipt combination possibilities are:

1. Halving the amount of cement by choosing pozzolanic cement instead of Portland

cement with basalt fiber reinforcement allows thinner thicknesses of the concrete products because cover layers for steel reinforcement are reduced or completely eliminated because basalt fiber reinforcement is used. The basalt fiber reinforcement does not corrode, and therefore the cover layers can be reduce or removed completely. Besides the weight reduction depending on reduced or completely removed cover layers, the weight per cubic meter of the concrete is reduced since the weight of the cement is reduced by 50 %. The effects of this is that the completed product let out less greenhouse gases, between 70 - 90 % in comparison with a corresponding product with steel reinforcement. Moreover the cost of material is reduced with up to about 35 %. The resistance of the concrete and thus the resistance of the product against penetrating chlorides and sulfates increases because of the composition of the pozzolanic cement and raw materials and the lack of reinforcement corrosion.

2. With the same amount of pozzolanic cement as for Portland cement a compression strength which is increased with about 50 % is obtained. With a higher compression strength the amount of basalt fiber reinforcement can be reduced with up to 40 % while maintaining the same or increased strength properties as before, and maintaining the other properties according to item 1. The economic consequences of using cement with a higher strength/higher quality are small in comparison with the costs for basalt fiber reinforcement.

3. The pozzolanic cement together with the basalt fiber reinforcement result in an

increased chloride and sulfate resistance, and thus also a longer life for the products, also in combination with steel reinforcement and also in a so called hybrid construction, i.e. a reinforcement combination of basalt fiber and steel reinforcement. A standard receipt according to the prior art containing Portland cement for a concrete having a compression strength above 100 MPa can look approximately as below:

Cement 450 - 600 kg

Silica 50 - 100 kg

Flow agent 2.2 - 3.5 %

Shrinkage reducing agent

Ballast 1 400 - 1 600 kg

Water 80 - 150 kg

Total weight (approx.) 1 980 - 2 450 kg per cubic meter. A standard receipt according to the prior art comprising pozzolanic cement for a concrete having a compression strength above 100 MPa could be approximatively as is exemplified below:

Cement 225 - 300 kg

Silica 50 - 100 kg

Flow agent 2.2 - 3.5 %

Shrinkage reducing agent

Ballast 1 400 - 1 600 kg

Water 50 - 100 kg

Total weight (approx.) 1 725 - 2 100 kg per cubic meter - a reduction in weight of approx. 14 %, meaning e. g. that the carbon dioxide emissions in transportation and production are reduced thanks to lower weight and/or more elements per load unit.

A general receipt containing pozzolanic cement with basalt fibers for a concrete according to the invention, e.g. for sandwich element:

Cement 185 - 200 kg

Flow agent depends

Shrinkage reducing agent

Ballast 1 600 kg Water 180 kg

Basalt fibers 3.8 - 75 kg

Total weight (approx.) 1 965 - 1 980 kg per cubic meter - a reduction in weight of approx. 9 % meaning that e.g. the carbon dioxide emissions in transportation and production are reduced thanks to lower weight and/or more elements per load unit.

The ballast might vary according to different screening curves (the size of the stones and the combination of these and thereby affect the compression strength of the concrete. Generally it can be said that the higher the desired compression strength is, the smaller the desired size of the stones of the ballast is. In high strength concrete the size of the ballast is between 0 and 6 mm with a larger amount of the smallest sizes, which is the reason for the silica in the receipt.

The basalt fiber content in the concrete varies depending on the flexural tensile strength FTS to be accomplished. With basalt fibers, a FTS above 15 MPa can be accomplished. This should be compared with the FTS of the concrete itself of between 3 and 5 MPa, normally approximatively 4 - 4.5 MPa. The strength-demands on the product are decisive of how much fiber to be blended into the concrete. The advantage of fiber is that it can be blended directly into the concrete and in this way an "already reinforced concrete" is obtained, which is poured into the mould.

The relationship between FTS and the amount of fiber in the concrete depends of the compression strength of the concrete - the lower the compression strength, the more fiber is needed to obtain the desired FTS. This relationship is outlined synoptically in the attached Fig. 1 in the form of graphs.

In general terms it can be stated that between 3.8 kg and up to 75 kg fiber are needed in the concrete, depending on concrete quality, in order to obtain a FTS between 5 and 16 MPa for standard concrete, and up to 25 MPa with high performance concrete, corresponding to 0.1 - 4 % of the dry weight according to the above. One further factor making Portland cement in the concrete complicated is that after the life of the product it has to be destructed. With the environmental regulations of today, concrete reinforced with steel reinforcement has to be separated, so that the steel is freed and can be put in a special deposit, and the concrete in another. The concrete will continue its decay also when lying in the deposit, where some environmentally dangerous substances leak out in the nature. See IVL "Jamforelse av miljopaverkan fran ledningsstolpar av olika material- en livscykelanalys, by Martin Erlandsson B2004 October 2011 (Comparison of environmental influence of telegraph poles of different materials - a life cycle analysis)). With a combination of the pozzolanic material containing cement and basalt fiber reinforcement this leakage is minimized and/or ceases completely.

A further advantage of the new concrete mixtures, wherein said cement prevails in combination with basalt fiber reinforcement, is that the energy consumption can be reduced and adapted when manufacturing different concrete products. With less concrete with a cement, which demands less energy to produce and with thinner and stronger products, energy is saved at several stages. The total energy consumption can be reduced with up to 60 % depending on which product it is.

In general, it can be stated that Portland cement in general has a low chloride resistance, and therefor different methods have been developed in order to increase the chloride resistance. This adds to the cost, affects the environment negatively and entails higher production costs and higher energy consumption.

The properties of the concrete are to a large part decided by the relationship between water and cement, water cement ratio (w/c ratio). Strength is the most important property of the concrete, second to durability. The strength of the concrete is decided, besides by the water cement ratio, also by type of cement and the properties of the ballast and its composition. Thereby, another factor for the strength of the concrete is the factual particle distribution of the ballast - that is the distribution of rock material having different particle sizes. Normally stone, gravel and sand are used together with fillers of different types. The ballast material normally consists of material having particle sizes down towards one tenth of a millimeter. The lower the water cement ratio is, the better properties the concrete will have against waterlogging. A w/c ratio below 0.30 gives a watertight concrete. With such low water cement ratios it is normally high performance concrete. With a smaller amount of cement, a smaller amount of water is also needed, and in such a way the compression strength increases. High w/c ratios mean that a larger amount of the water evaporates from the concrete mixture, whereby so called plastic shrinkage cracking occurs. With the pozzolanic cement less cement is needed, and accordingly also less water, which with a great probability is the reason for why a smaller number of so called plastic shrinkage cracks arise. This in combination with basalt fiber reinforcement reduces the risk for such cracks.

Concrete shrinks during the hardening time, which is why micro and shrinkage cracks arise, which convey water in towards the reinforcement. Therefore, cover layers are used when black steel reinforcement is used. The thicker the concrete to be cast is, the greater the risk for cracks, and thus also larger risk for waterlogging into the concrete. These cracks arise also in the cover layers, which is why there is a risk for corrosion of the reinforcement, also when cover layers are used. One method for minimizing shrinkage cracks is to use a mesh reinforcement. Basalt fiber bundles, such as Minibars™, act in a different way than both steel and plastic fibers. Steel and plastic fibers do not act until cracks have arisen in the concrete, and act by holding together the concrete, when the crack arises. Basalt fiber bundles, such as Minibars™, hold the concrete together, i.e. prevents micro and shrinkage cracks from arising. Basalt fiber bundles, such as Minibars™, counteract cracks thanks to their strong adhesion in the concrete. Hereby the risk for that water starts to penetrate through cracks is reduced already from the beginning.

In the same way sulfate and chloride ions work themselves into the concrete and affect the durability of the concrete, since the Portland cement has a low resistance against these ions. With pozzolanic cement the influence from these is considerably less, since the raw material for pozzolanic cement is fly ash, which has other chemical properties compared to limestone. In other words the pozzolanic cement is the most important component in order to make the concrete withstand chlorides and sulfates in water and from the surroundings. A high cement content in combination with a small amount of water (low w/c ratio) and different types of fillers such as silica, and a ballast having small diameters, are the most important components in order to produce a concrete, which is water tight. With pozzolanic cement the resistance against chlorides and sulfates increases. With the inventive concrete mixture comprising basalt fibers water tight concrete constructions can be accomplished.

Description of the Drawings

Figure la-f illustrate the flexural tensile strength for different cement qualities and amounts of basalt fiber bundles.

Fig. 2 shows a first illustrating wall element according to the invention.

Fig. 3a-b shows an illustrating pylon according to the invention.

Detailed Description

The invention will now be described more in detail with reference to exemplifying

embodiments. In Fig. la-f ratios between Flexural Tensile Strength (FTS) and the amount of fiber in the concrete are shown. The size of FTS depends on a combination of amount of fiber and the concrete quality used. Concrete quality in this case refers to its compression strength - the higher the compression strength is, the higher FTS will be obtained with a given amount of fiber. These circumstances depend on the fact that the amount of cement in the concrete having a higher compression strength is higher, and thus there is a larger amount of cement paste to which the fibers can adhere.

Fig. la shows concrete having the quality C25/30 with a basalt fiber bundle amount of 0.3 % (volume). When a load is applied this will go up to 25 kN until the first crack comes (the peak of the graph). Thereafter the concrete cannot take up much load. In Fig. lb the concrete is of the same quality as in Fig. la, but the amount of basalt fiber bundles is 2.5 % (volume). The first crack comes approximately at the same load, but the concrete continues to take up the applied load, and even an increased load. In Fig. lc the concrete is of the same quality as in Fig. la, but the amount of basalt fiber bundles is 4.0 % (volume). The first crack arises at about the same load, but the concrete is able to withstand increase loads of up to close to 50 kN. Fig. Id shows concrete of the quality C50/60 with an amount of basalt fiber bundles of 0.3 % (volume). When load is applied it will take until approximately 35 kN, before the first crack comes (the peak of the graph). Thereafter the concrete cannot take up much load. In Fig. le the concrete is of the same quality as in Fig. Id, but the basalt fiber bundle amount is 2.5 % (volume). The first crack comes at approximately the same load, ca. 40 kN, but the concrete can take up an increased applied force up to close to 60 kN. This should be compared also with Fig. lb, wherein the concrete has the same amount of basalt fiber bundles 2.5 %. Fig. la-e show measurements made according to European Standards. In Fig. If is shown a measurement according to North American Standard. The lower graph shows FTS in relation to the amount of basalt fiber bundles for a concrete of the quality C30 and the upper graph for concrete of the quality C65.

A sandwich element with Portland cement produced today normally has the following dimensions: exterior element having a thickness of 70 - 80 mm, an insulation with a thickness of approximately 200 mm (might vary depending on U-value, type of building, etc.), and an interior element having a thickness between 120 - 200 mm. The thickness depends mainly on that the steel reinforcement needs a cover layer in order to delay the corrosion of the steel

reinforcement. The exterior element weighs approximately 165 - 190 kg/m ² , the insulation is the same for the alternatives, the interior elements weights approx. 285 - 470 kg/m ² with a specific gravity of the concrete of 2 350 kg/m ³ . In Sweden about 450 kg Portland cement is used for this type of concrete.

With pozzolanic cement the amount can be reduced to approx. 225 kg. With this measure only, the weight is reduced with approx. 9.5 %, and the concrete cost drops from approx. SEK 420 to SEK 94.50. The average greenhouse gas reduction for the cement comprised in the concrete is approx. 77 %. The normal prize for this concrete is approx. SEK 900/m ³ , which means a prize of approx. SEK 207 /m ² excluding reinforcement. Steel reinforcement is approx. SEK 64/m ² , resulting in total cost of SEK 271 /m ² . With the use of the cement in this case the time until chloride penetration is increased with 4 %, and accordingly a moderate increase in product life. According to the present invention, pozzolanic cement is combined with fiber reinforcement in basalt, preferably in bundles, such as e.g. Minibars™. According to one embodiment, a wall element 1 is shown, a so called sandwich element, wherein the thickness of an exterior element 2 is reduced to 40 mm and the thickness of an interior element 3 is reduced to 80 mm. The thickness of an insulation 4 corresponds to the example above. The thickness of the exterior and interior elements 2, 3 can be reduced thanks to that the fiber reinforcement is free from corrosion, and accordingly no cover layers are necessary. The interior element can be made even thinner, from a structural point of view, but because of the sound propagation, this thickness has been chosen. Thanks to the inventive combination of pozzolanic cement and basalt fiber reinforcement the exterior element 2 weighs approx. 85 kg/m ² and the interior element 3 approx. 170 kg with a specific gravity of 2 125 kg/m ³ (the specific gravity has been reduced corresponding to the reduction of the cement). The amount of basalt fiber is approx. 0.3 % (volume) or 5.7 kg/m ³ . The sum of weight reductions is approx. 46 %. With the cost for pozzolanic cement one m ³ of concrete is approx. SEK 575. One m ² will in this case cost SEK 69 /m ² excluding reinforcement. The basalt fiber reinforcement will cost approx. SEK 100/m ² , which in total give SEK 169 /m ² ; a saving of approx. 38 %/m ² . Since the elements are lighter and thinner, more elements can be taken on each load unit, where the weight used to be the limiting factor. Three elements instead of two results in a saving of the transport with 33 %. With a lower weight, smaller cranes can be used on the building sites, and further smaller footings, larger living space because of thinner elements, shorter establishment times, etc. will be gained. With all factors taken into consideration the greenhouse gas emissions will be reduced with approx. 70 - 80 %. With this construction the effects of the chloride penetration will be reduced to only concern the concrete in itself, and accordingly the life will be substantially increased, since there is no influence on the reinforcement.

A conceivable sandwich element 1, see Fig. 2, might comprise an exterior element 2 having a thickness of 10 - 40 mm of the concrete quality C25/30 - C200 and being reinforced with 0.1 - 0.5 % basalt fibers, preferably in the form of bundles, such as Minibars™. An interior element 3 can be 20 - 100 mm in thickness of the same concrete quality with basalt fiber reinforcement comprising 0.1 - 1 % (volume) basalt fibers, preferably in bundles having a diameter of 0.65 - 2 mm and a length of between 10 and 50 mm. Further, rods of basalt fiber reinforcement, e.g. Basbars™ having a diameter between 4 and 14 mm can be inserted into the interior elements in order to handle higher buildings. Also so called hybrids, i.e. a combination of basalt fiber reinforcement and e. g. steel can be used. An interior layer 4 between the exterior and interior elements 2, 3 might also be provided with a reinforcement of basalt 5 (in everyday speech "ladder"). This connects the exterior and interior elements so that they are connected to each other during transport and fire. Corresponding examples can be applied on mounting bases for e.g. house construction. It is also conceivable to have two types of mounting bases, one with a sandwich construction similar to the sandwich element, and a simpler variant having a concrete side plus insulation.

According to the invention the inventive concrete might also be used for ground poles and pylons. One example, shown in Fig. 3, is a pylon having a construction primarily intended for electric power transmission. The construction is built on a combination of pre-tensioned basalt fibers, such as Basbars™, with basalt fiber bundles, such as Minibars™, mixed into the concrete for crack control in a high performance concrete. With the pozzolanic cement the design, the strength and reinforcement content of the pylon can be varied depending on where in an electric power line the pylon is to be placed. Moreover, the chloride resistance is enhanced, which means that a further extension of the life in chloride influenced areas, such as e.g. close to the sea, deserts and other areas with high chloride concentrations in the surroundings.

With the inventive concrete a further variable is created in the design of pylons and similar objects, which did not exist earlier, and in this way the cost effect analysis (LCC) can be enhanced for the respective geographical area, and thus also the costs for this. With different amounts of cement and with varying amounts of reinforcement the strength can be adapted to different forces and climates. Such an adaption has not been economically and environmentally possible earlier, since increased amounts of cement affect the environment negatively. Even thinner layers can be accomplished with maintained strength, wherein both material and costs are saved. The energy consumption in the production and transport are further reduced.

Since the chloride durability is increased in combination with basalt fiber reinforcement, much thinner constructions can be accomplished, also with steel reinforcement, wherefore other areas of use are made possible, for example pylons, ground poles for pile driving in earth with inferior bearing capacity, e.g. old lake bottoms, etc. Hereby is provided a construction, which has several fields of use in one and the same form and in the same production line, wherefore the cost of production is considerably reduced while at the same time the other properties are held intact. Pylons and ground poles are built on the same principle, in that they shall be able to carry vertical loads. High vertical loads often demands steel reinforcement, wherefore the properties of the pozzolanic cement together with the basalt fiber make it possible to cope with the corrosion demands with thin cover layers in combination med basalt fibers.

The combination gives a very low energy consumption in the manufacture of the products because the consumption of materials, i.e. concrete and reinforcement, is low and the composition of the materials at the time of the production results in a low energy requirement.