WO2016064325A1

WO2016064325A1 - Concrete mixture and its applications

Info

Publication number: WO2016064325A1
Application number: PCT/SE2015/050362
Authority: WO
Inventors: Günter VILLMAN; Göte LINDFORS
Original assignee: Smart Development Sweden Ab
Priority date: 2014-10-22
Filing date: 2015-03-25
Publication date: 2016-04-28
Also published as: SE1400498A1; WO2016064324A1; WO2016064326A1

Abstract

Novel concrete installations are accomplished, comprising pozzolanic cement in combination with mineral based reinforcements. Moreover, several applications of the novel concrete mixtures are disclosed.

Description

CONCRETE MIXTURE AND ITS APPLICATIONS

1

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 which partly consists of pozzolanic material, such as fly ash, which might 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 to use 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 on for example pressure, temperature and dilatation, further, since different types of reinforcement involves 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 of which has 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. In particular, it is a 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 obtain substantially different properties.

The invention offers 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 is at least 50 % dry weight, preferably between 75 % and up to 82 %.

According to another embodiment, the amount of basalt fibers is 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 substantially watertight construction detail is accomplished, for use for example as a foundation base or a so called sea-wall, which is also associated with substantially lower total cost and environmental load, where an inventive concrete mixture is used.

According to a third aspect, a construction detail for installation in contact with or floating on water is accomplished, which entails lower total cost and environmental load, and also a longer life, where an inventive concrete mixture is used.

The possible combinations are not obvious, but instead 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 in 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 addition of ballast 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 receipt combinations possibilities are not obvious but instead a very good understanding of the properties of the materials is necessary. The basalt fiber bundles, such as Minibars™, act on 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. Half 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 reduced or be 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 lets 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, an 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 is, 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 leek out in the nature. See IVL "Jamforelse av miljopaverkan fran ledningsstolpar av olika material- en livscykelanalys, by Martin Eriandsson 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 completely ceases.

A further advantage with 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 add 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 extent 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 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 the properties of the concrete will be 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 pozzolanic cement less cement is needed and thus also less amounts of water. Therefore with great probability a smaller number of so called plastic shrinkage cracks will arise. This in combination with basalt fiber

reinforcement reduces the risk of such cracks.

Concrete shrinks during the hardening time, which is why micro and shrinkage cracks arise, which lead 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 increased risk for waterlogging into the concrete. These cracks also arise in the cover layers, which is why there is a risk for corrosion 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 Portland cement has a low resistance against these ions. With pozzolanic cement the influence from these 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 bring about a concrete, which is watertight. With pozzolanic cement the resistance against chlorides and sulfates increases.

With the inventive concrete mixture with basalt fibers watertight 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 one example of how an existing sea-wall can be strengthened.

Fig. 3 shows one embodiment of a sea-wall.

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 the 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 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 lasts until approximately 35 kN, before the first crack comes (the peak of the graph). Thereafter the concrete cannot take 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. For example, there are two kinds of foundation bases, one being a sandwich construction, the other a simpler variant with one concrete side plus insulation. The construction can also be used as separator and support between water and ground, so called sea-walls.

Sea-walls are often subjected to water with high contents of chlorides, wherefore both a chloride resistant cement and corrosion free reinforcement are necessary in order to obtain a long life. In this case, all variables according to the above, might be used in order to accomplish the optimum construction in view of costs, environmental load, weight and life. Moreover, at very high loads, hybrid solutions might be accomplished without noticeably affecting the weight conditions.

According to one example of the invention a reinforcement of an existing sea-wall 1 can be accomplished, see Fig. 2. With the same amount of pozzolanic cement as Portland cement the compression strength is increased with 50 % at less carbon dioxide emission, approx. 70 %. Hereby the chloride resistance is increased while at the same time the need of fiber

reinforcement is reduced with maintained strength, and possible shrinkage and microcracks are diminished, which enhances the chloride resistance ever further, and also the life of the product. With a thinner construction 2, up to approx. 50 %, a so called hybrid solution can also be made, wherein the combination of the pozzolanic cement and basalt fiber bundles, such as Minibars™, give the necessary protection against corrosion for any steel reinforcement.

The costs for a construction according to the above is reduced with approx. 25 % compared to the corresponding construction with Portland cement because a smaller amount of cement is needed and thanks to less costs for the comprised reinforcement. If the cement content of pozzolanic cement would be increased with 50 %, the compression strength is further increased, and if, at the same time, the screening graph of the ballast is changed upwards, similarities with high performance concrete is obtained. Such a concrete in combination with the chloride sustainability of the cement and the properties of the basalt fiber reinforcement, make it substantially watertight, and accordingly very suitable for chloride rich environments, such as for example at the sea and in some deserts. One example of a water durable reinforcement 2 on an existing sea-wall having the thickness of 180 - 800 mm, is shown in Fig. 2. The reinforcement 2 can be 30 - 100 mm thick and might comprise a concrete with a compression strength of 80 - 150 MPa and a w/c ratio below 0.30, preferable below 0.25. The concrete comprises pozzolanic cement with reinforcement of basalt fiber bundles, such as Minibars™, 0.3 - 1.5 % (volume), having a diameter of 0.5 - 0.7 mm and a length between 15 and 46 mm.

Of course, it is also possible to create sea-walls 3 from the start using the inventive concrete mixture as described above. These can be made as prefab elements or be moulded at the site, preferably with a thickness of 75 - 400 mm.

Floating, or close-to-water related concrete constructions are defined as constructions made of concrete, which are intended to exist, completely or partly, in water and/or on water and on land. Example of such constructions are floating pontoons, floating freely or connected with land, oil rigs, barges, completely or partly made of concrete, floating caissons for e.g. beacons, buoys, etc. Other types of constructions, which lie completely or partly in water and on land, getting in contact with both medias, are quays, bridges with pylons and abutments, piers, loading areas in association with ports, poles, etc.

Today one is forced to use different thicknesses of the cover layers and/or to choose stainless and acid proof steel reinforcement, and/or epoxy laminated black steel reinforcement in order to obtain a sufficiently long life of constructions in the above described areas. These factors are varied depending on the chloride content in the area, for which the product intended. This has led to that the constructions often is unnecessary large and heavy, while at the same time the construction then involve a high environmental load at manufacture, transport and destruction. With an inventive combination of the pozzolanic cement and basalt fiber reinforcement inclusive of hybrid solutions, the above drawbacks can be reduced with different combinations of the pozzolanic cement and different reinforcement solutions, and the thickness and compression strength of the concrete. Thanks to its chloride durability and ability to increase compression strength, the amount of concrete can be reduced with approx. 10 - 40 %, depending on construction and needed flexural strength. Through the combination with basalt fiber bundles, such as Minibars™, the density of the concrete is increased because micro and shrinkage cracks (occur when the concrete burns) are considerably reduced while at the same time the need of minimum reinforcement is removed. The minimum reinforcement is aimed to reduce shrinkage cracks in the cover layers intended to protect the structural black steel reinforcement in the construction. The chloride durability in combination with basalt fiber bundles, such as Minibars™, and higher compression strength give a denser concrete, which protects the structural reinforcement for a longer time. Less concrete means less transports, lower greenhouse gas emissions, lower costs, lower maintenance costs, etc. The combination possibilities are good with the frame of these concrete constructions in that the concrete and its thickness can be adapted after the prevailing chloride conditions, the demand of life span, the demand of carrying capacity, demand of environment and the desired levels of greenhouse gas emissions. This is accomplished by using the correct amount of pozzolanic cement in

combination with thickness, demands of strength and reinforcement, etc. The dimensioning will be cost effective and more environmentally friendly compared to what was possible before. Reduction of greenhouse gas emissions up to approx. 50 %, cost reduction with up to between 35 and 40 %, life span increase with up to 50 %, LCC reduction with up to 30 %, etc. One example is a concrete with a compression strength of 80 to 150 MPa, and a w/c ratio below 0.30, preferably below 0.25. The concrete comprises pozzolanic cement with reinforcement of basalt fiber bundles, such as Minibars™, 0.3 - 1,5 % (volume), having a diameter of 0.5 - 0.7 mm and a length of between 15 and 46 mm.

Claims

I. A concrete installation in, or partly in contact with, water, wherein the installation is erected with a concrete mixture comprising cement, pozzolanic material, ballast, water and possible additives, characterized in that it also comprises basalt fibers for reinforcement.

2. The concrete installation according to claim 1, in which the amount of pozzolanic material is at least 50 % dry weight.

3. The concrete installation according to claim 2, in which the amount of pozzolanic material is between 75 % and up to 82 %.

4. The concrete installation according to any of claims 1, 2, or 3, in which the amount of basalt fiber is between 0.1 % and 4 % dry weight.

5. The concrete installation according to claim 4, in which the basalt fibers have been treated with polymer.

6. The concrete installation according to claim 5, in which the basalt fibers are collected in bundles.

7. The concrete installation according to claim 6, in which the basalt fiber bundles have a basalt fiber helicoidally wound around them.

8. The concrete installation according to claim 5, 6, or 7, in which the basalt fiber bundles are between 5 and 60 mm long, preferably between 15 and 50 mm long, and most preferably between 20 and 46 mm long.

9. The concrete installation according to any of claims 5 - 8, in which the circumference of the basalt fiber bundles are between 0.5 and 1.0 mm, preferably between 0.6 and 0.8 mm. 10. The concrete installation according to any of claims 5 - 9, in which the polymer has a melting point above 400 degrees Celsius, preferably above 475 degrees Celsius.

II. The concrete installation according to any of the previous claims, characterized in that the concrete mixture has a water cement ratio below 0.30, preferably below 0.25.

12. A method of dimensioning a specific construction detail in concrete in order to accomplish a desired strength, characterized in that the dimensioning starts from a specific existing construction detail, which existing construction detail is manufactured from a conventional concrete mixture and comprises a cover layer of a non-reinforced concrete, in that the specific construction detail is designed in a concrete mixture according to any of the preceding claims, in that said specific construction detail is dimensioned with a profile, which is more narrow than the existing construction detail, and in that said specific construction detail lacks especially a non-reinforced protective layer.