NL2010848B1 - Method for the production of permeable foamed concrete, permeable structural part and use thereof. - Google Patents

Abstract

The present invention relates to a method for the production of permeable foamed concrete, a permeable structural part and the use thereof. The method comprises: - forming a mixture by mixing water, concrete-reinforcing fibers, cement and a plasticizer; and - foaming the mixture with a foaming agent. The plasticizer may also comprise a superplasticizer.

Description

METHOD FOR MANUFACTURING PERIODIC FOAM CONCRETE, PERIODIC CONSTRUCTION PART AND USE THEREOF

The invention relates to a method for manufacturing foamed concrete. Foam concrete includes cement, water, foaming agent and air. A foam is obtained by means of the foaming agent and the air, as a result of which the concrete contains air bubbles. This means that foamed concrete has a low weight.

Another property of foamed concrete is that it is hardly permeable. Foam concrete, for example, can hardly absorb water. In some applications, however, a permeable building material with a low weight and strength comparable to the strength of foamed concrete is required. Conventional foamed concrete is unsuitable for such applications. In particular, an application can be envisaged for a material for a substrate so that it is permeable, for example for water and air. Among other things, this benefits the drainage.

An object of the invention is to remedy or reduce the above problem and to provide a method for manufacturing a lightweight, strong and permeable building material.

This object is achieved with the method for manufacturing permeable foamed concrete according to the invention, the method comprising: - forming a mixture by mixing water, concrete-reinforcing fibers, cement and a plasticizer; and - foaming the mixture with a foaming agent, such that a foamed concrete is obtained that is water and / or air permeable.

It is noted that the steps of the process can be carried out in any suitable order.

In particular, the water, the fibers, the cement and the plasticizer can be added in any suitable order. For example, the water is mixed with the concrete-reinforcing fibers, after which the remaining raw materials are added. This results in a uniform distribution of fibers in the final concrete, which benefits the strength of the concrete. Preferably, cement is first added to the mixture of water and fibers, and then the plasticizer. In another example, the water is first mixed with the cement, after which the remaining raw materials are added.

Practical tests have shown that by carrying out the steps of the method a foamed concrete is obtained which is permeable, for example permeable to liquids such as water and / or air permeable. Moreover, it has surprisingly been found that the strength of the foamed concrete obtained according to the invention is comparable to the strength of conventional foamed concrete. The density of about 400-600 kg / m3 of the permeable foamed concrete obtained with the method according to the invention is also comparable with the density of conventional foamed concrete.

For example, the mixture of water, cement, fibers, plasticizer and foam for obtaining foamed concrete is poured into a formwork. The foamed concrete is then allowed to cure.

According to the inventors, the addition of the plasticizer, also known as water reducers or pees, provides the permeability of the foamed concrete to a large extent. Where with conventional foamed concrete isolated air bubbles are created in the concrete, the air bubbles in the foamed concrete are connected to each other according to the method according to the invention, so that the material becomes permeable.

The concrete reinforcing fibers prevent the foam concrete from collapsing due to its own weight. Although concrete reinforcing fibers are conventionally used to prevent shrinkage in the transition from plastic phase to solid phase and thus for better water tightness, it is surprisingly found that the fibers do not have a negative influence on the permeability of the foam concrete resulting from the method according to the invention. It has been found that in combination with the plasticizer the fibers provide firmness and the plasticizer essentially provides the permeability. Concrete-reinforcing fibers, in particular plastic fibers or glass fibers, moreover have the advantage that they are well resistant to moisture, in contrast to conventional metal reinforcement. Given the open structure of the foam concrete, this is of great importance.

For example, the fibers are provided such that they have substantially the same orientation in the resulting foamed concrete. An anisotropic concrete is thus obtained.

Moreover, experiments show that despite the open structure of the foamed concrete obtained, the foamed concrete is not damaged when exposed to moisture and cold. For example, conventional concrete can crack when it freezes. Surprisingly, the method according to the invention leads to a permeable foamed concrete that is not or hardly damaged by freezing cold.

Preferably no aggregate material is used at all in the method according to the invention. If aggregate materials are nevertheless used in an alternative embodiment according to the invention, relatively coarse aggregate materials, such as gravel or coarse sand, are preferably added to the mixture. Impact materials with a grain size of less than about 1 mm are preferably avoided, since these materials reduce the permeability of the foam concrete to some extent.

The foaming agent is preferably a synthetic foaming agent. For example, the foaming agent of the Cugla type concerns foaming agent 12070.

In a preferred embodiment of the method according to the invention, the plasticizer comprises a so-called superplasticizer, also referred to as superplast. For example, the plasticizer comprises a polycarboxylate ether (PCE) superplasticizer. More water can be kept off by means of a superplasticizer, so that a more permeable foamed concrete can be obtained. Moreover, it appears that compared to a conventional plasticizer, less superplasticizer is required to achieve the same result.

Preferably the superplasticizer comprises naphthalene sulfonate (also called: sulfonated naphthalene) or sulfonated melamine formaldehyde, most preferably naphthalene sulfonate. For example, Cugla OQ is used.

In a preferred embodiment of the invention, 1-50 ml plasticizer is used per kilogram of cement, preferably 1-25 ml plasticizer, and more preferably 1-12 ml plasticizer.

The amount of plasticizer is preferably adjusted to the desired openness of the foamed concrete to be produced. The addition of more plasticizer leads to a more open structure, so that, for example, liquid uptake is faster. The amount of plasticizer appears to have no, or at least little, influence on the total volume of liquid or air that a cubic meter of permeable foamed concrete can absorb according to the method, only on the speed at which the liquid or air is absorbed.

The volume percentage of water absorption of the foamed concrete obtained with the method according to the invention is 10 to 50 volume percent. This allows 1 m3 of foamed concrete to buffer approximately 100-500 1 water.

Preferably 0.3 liter -1.7 liter plasticizer is added per m3 permeable foamed concrete, more preferably 0.4 liter - 1.6 liter, for example 0.4 - 0.8 liter.

Preferably, the amount of plasticizer is inversely proportional to the power being mixed. It appears that less plasticizing is necessary when more powerful mixing.

Preferably, 1-3 grams of plasticizer per kg of cement is used, preferably 1.5-2 grams and most preferably 1.75 grams.

In a preferred embodiment of the invention, the water / cement factor is 0.3-0.6, preferably 0.35-0.55 and most preferably 0.4-0.5.

The water / cement factor, also known as wcf, is the weight ratio between water and cement. In the context of the invention, the ratio between water and cement is meant excluding any water used for foaming the mixture. This is in line with the current definition of water / cement factor.

In a preferred embodiment according to the invention, the concrete-reinforcing fibers comprise plastic fibers.

It appears that in particular plastic fibers are suitable for reinforcing the permeable foamed concrete. For example, the plastic fibers are uncoated or provided with a special coating.

For example, the plastic fibers are nylon fibers. Preferably the fibers comprise polypropylene fibers.

Preferably the fibers have a length of 3 - 30 mm, for example 3, 6, 12 or 18 mm. The fibers are preferably coated with a surfactant. For example, fibers of the ADFIL Fibrin brand are used.

In a preferred embodiment, 1-20 g of concrete-reinforcing fibers are used per kilogram of cement, preferably 1-10 g of fibers, more preferably 2-5 g of fibers and most preferably 2.25 g of fibers.

The aforementioned quantities appear to reinforce the foam concrete to be obtained in such a way that it can be applied in a layer with a layer thickness of at least 1 meter, the foam concrete being sufficiently strong.

In a preferred embodiment of the method according to the invention, foaming comprises forming a foam on the basis of a foaming agent and subsequently mixing the foam with the mixture.

In other words, a foam is first created separately, after which this foam is mixed with the mixture. Alternatively, foaming agent is added to the mixture, or a part of the mixture, after which the mixture is foaming with foaming agent, for example by adding water and air.

As described above, various sequences in the addition of raw materials and in the foaming step of the invention are possible. For example, the concrete-reinforcing fibers and / or the plasticizer can be added before foaming or after foaming the mixture.

Preferably, plasticizer is added to the foaming agent prior to forming the foam. The mixture of cement, water and concrete-reinforcing fibers is thus mixed with the foam obtained from a mixture of foaming agent and the plasticizer. For example, the fibers are first mixed with water, after which cement is added.

Mixing the foaming agent and plasticizer before the foaming step causes the plasticizer to be substantially uniformly distributed in the foam obtained from this mixture. The influence of the plasticizer on the air bubbles in the foam concrete is thus increased. A permeable foamed concrete is hereby formed with relatively little plasticizer.

Alternatively, the concrete-reinforcing fibers are added afterwards, so that a mixture of cement and water is mixed with the foam obtained from a mixture of foaming agent and plasticizer, after which the concrete-reinforcing fibers are added.

In a preferred embodiment of the invention 1-10 liters of foam is used per kilogram of cement, preferably 1-5 liters of foam and more preferably 2-3.5 liters of foam.

In the case that the foaming agent is added to the mixture after which the mixture is foamed, an amount of foaming agent is added equivalent to that required for the aforementioned amounts per kilogram of cement.

Preferably, 1-5 grams of foaming agent is used per kilogram of cement, preferably 1-3 grams and most preferably 2.25 grams.

In an embodiment according to the invention the cement comprises Portland cement type A and / or type B and / or a cement with a comparable grain size distribution.

In a preferred embodiment, the cement comprises a cement of strength class A (32.5 MPa) and / or B (42.5 MPa). For example, the cement comprises CEM I / A, CEM I / B, CEM II / A, CEM II / B, CEM III / A, CEM III / B, CEM IV / A, CEM IV / B, CEM V / A or CEM V / B.

It appears that coarse cement types lead to a better result than fine cement types, such as, for example, Portland cement type C. Although some degree of permeability is still obtained in that case, the results with coarse milled cement types are many times better.

Preferably the cement comprises a class B cement.

In a preferred embodiment, the following is added per kilogram of cement, preferably cement with strength class B: - 0.3 - 0.6 kg of water, preferably 0.35 - 0.55 kg and most preferably 0.4 - 0, 5 kg; - 1 - 5 grams of foaming agent, preferably 2-3 grams and most preferably about 2.25 grams, wherein the foaming agent preferably comprises a synthetic foaming agent; - 1 - 5 grams of plasticizer, preferably 1-3 grams and most preferably about 1.75 grams, wherein the plasticizer preferably comprises a superplasticizer; - 1 to 5 grams of concrete reinforcing fibers, preferably 2-3 grams and most preferably about 2.25 grams, wherein the fibers preferably comprise plastic fibers; and 40-160 grams of additional water for producing the foam, preferably 60-120 grams, most preferably about 80 grams.

For example, the foamed concrete is produced on the basis of the following weight ratios: - 400 kg of cement (type B) - 165 kg of water - 900 grams of synthetic foaming agent - 700 grams of superplasticiser - 900 grams of synthetic fibers - 32.5 kg of water for the purpose of producing the foam.

In a further preferred embodiment - first the water is mixed with the fibers and the cement and separately the foaming agent and the plasticizer are mixed together; and - subsequently pumping the mixture of water, fibers and cement, injecting the foamed mixture of foaming agent and plasticizer.

With reference to the previous example, a foamed concrete is created in this way with a water absorption of 36% and a water permeability of at least 600 mm of water per hour.

The water permeability of the foamed concrete can be tested by an infiltration test. For example, a double ring infiltrometer is used for this purpose, which is punched into the foamed concrete.

In a preferred embodiment, the base sludge (cement, water and fibers) is mixed with the foamed foaming agent and plasticizer mixture in less than 2 seconds, preferably in less than 1 second, preferably less than 0.5 second. For this purpose, the mixture of basic sludge, foam and plasticizer is preferably passed through an inline mixer. For example, the inline mixer is a mixing tube. For example, a mixing tube of 1 meter in length and 65 mm in diameter is used at a pouring rate of 50 cubic meters per hour, so that the mortar, foam and pee are only present in the mixing tube for about 0.2 s.

For example, the base species is made by mixing the water, concrete, and fibers at 70 - 150 revolutions per minute, more preferably at about 120 revolutions per minute.

The invention further relates to one permeable structural part for forming a substrate, comprising a layer of foamed concrete manufactured with the method as described above.

Such a permeable structural part can be used for water storage, for example in greenhouses. Also for applications where buffer capacity of rainwater is important, the permeable construction part according to the invention finds its application, such as in sports fields, such as soccer fields, tennis courts, hockey fields and athletics courts, as well as for example in parking areas. In addition, the sports court does not freeze up in the event of frost, preventing dangerous situations and / or damage. A further advantage is that moisture can be retained temporarily so that drying out of a layer on or below the structural part is prevented.

For example, the permeable structural part comprises a rubber top layer applied to the foam concrete layer.

Such a construction part is particularly interesting for use as a substrate in sports courts. Due to the open structure of the foam concrete according to the invention, the rubber mat is pressed slightly loose from the substrate by the vapor pressure.

In another example, artificial grass or gravel is provided on the structural part. An advantage of the structural part according to the invention is that no intermediate layer is required for applying a top layer. With conventional foamed concrete, an intermediate layer must be provided, for example asphalt, because the top layer cannot be glued directly onto the bottom layer.

Finally, the invention relates to the use of such a permeable structural member as a permeable substrate. For example, the substrate is applied at sports fields, parking areas, greenhouses, roads and / or squares.

For the permeable structural part and the use thereof according to the invention, the same advantages and effects as described above with regard to the method according to the invention apply.

In the following, the invention will be described with reference to exemplary embodiments thereof, with reference to the figures.

Figure 1 shows schematically the different steps of the method according to the invention in a first preferred embodiment;

Figure 2 shows schematically the different steps of a second embodiment of the method according to the invention;

Figure 3 shows schematically the different steps of the method according to a third embodiment according to the invention;

Figure 4 shows schematically a possible internal structure of the foamed concrete obtained with the method according to the invention; and

Figure 5 shows schematically a system for performing the method according to the invention.

In an exemplary embodiment, 900 g of plastic fibers are mixed with 90 kg of water in step 2 of Figure 1. These are fibers with a length of about 5 mm. Although the fibers in the figure are shown schematically in the form of a cartel, they are generally straight. 225 kg of cement is then added in step 4.

Then in step 6 2500 cc superplasticizer is added. In step 8, foaming agent and water are mixed, which are then foamed in step 10 by means of air under pressure so that 750 liters of foam are obtained. In this case it is synthetic foam.

In step 12 the foam is mixed with the mixture from step 6. The final mixture is finally poured into a formwork to form a structural part (step 14). This mixture is allowed to cure to permeable foamed concrete.

In an alternative embodiment according to the invention, 900 g of fibers are also mixed with 90 kg of water in step 2, after which 225 kg of cement is added in step 4. However, plasticizer is now mixed with foaming agent and water in step 16, which mixture is then foamed in step 10 by supplying air under increased pressure. The resulting foam is added to the mixture from step 4 in step 12, after which a structural part can again be poured in step 14 (Figure 2).

Preferably, the ratio of foaming agent to pee is 50% -60% foaming agent to 50% -40% pee, more preferably 53% -60% foaming agent to 47% -40% pee and most preferably about 60% foaming agent to about 40% pee.

In a third embodiment, fibers are mixed with water in step 2 (Figure 3), after which cement is added in step 4. Foam is prepared as in the first embodiment in steps 8 and 10 and added to the mixture in step 12. Only then is the superplasticiser added in step 6, after which the concrete can be poured in step 14.

Alternatively, in the above embodiments (Figs. 1-3), the cement is first mixed with water and then the plastic fibers added.

Figure 4 shows schematically how an internal structure of foamed concrete manufactured according to the method according to the invention can be constructed. The foamed concrete 18 comprises air bubbles 20 which are connected by means of channels 22. In addition, the foamed concrete 18 contains plastic fibers 24.

In this embodiment a damping layer 26 is placed on the top side of the foam concrete on which a top layer 28 is provided. For example, the top layer 28 is artificial grass, gravel or rubber. Layer 26 is, for example, a layer of sand, such as breaker sand. Layer 26 is optional.

It may be clear that other relationships between cement and water can also be chosen. For example, 350 kg of cement is mixed with 175 kg of water and 400 cc of superplasticizer is added. In addition, in particular any intermediate value is also possible, i.e.: 225-350 kg of cement, 90-175 kg of water and 400 cc - 2500 cc plasticizer.

This leads to a draining foam concrete with a density of 400-600 kg per cubic meter. The first embodiment (Figure 1) with 225 kg of cement and 90 kg of water leads to a density of 400 kg per cubic meter and an embodiment with 350 kg of cement and 175 kg of water leads to a density of 600 kg per cubic meter.

For example, the method is performed using system 30 (Figure 5). The system comprises, among other things, a water supply 32, a supply 34 for a mixture of foaming agent and pee, and a compressor 36 for generating an air flow. By means of pumps 38, 40, the water, the mixture of foaming agent and plasticizer and the air are led to a foam generator 42 (also known as a foam chamber or foam gun). The supply of the foam to the rest of the system can be controlled by means of a valve 44.

System 30 further comprises a second water inlet 46, a cement inlet 48 and a fiber inlet 50. The water from inlet 46 can be introduced into the cement mixer 54 with the cement and the fibers, pump 52 pumping the water towards mixer 54. As soon as the basic sludge is ready, it is led to base 56 for further supply to the rest of the system 30.

The foam and the base species are mixed in mixing tube 58. By controlling the pumping speed, the mixture remains in mixing tube 58 for only 0.23 s. In the example shown, the tube has a length of 1 meter and a diameter of 65 mm; the volume of the mixing tube is therefore 3.3 liters. At a pump speed of 50 m3 per hour, the mixture thus remains in the mixer for approximately 0.23 s.

The invention is by no means limited to the above described preferred embodiments thereof. The requested rights are determined by the following claims within the scope of which many modifications are conceivable.

Claims (16)

A method for manufacturing permeable foamed concrete, comprising: - forming a mixture by mixing water, concrete-reinforcing fibers, cement and a plasticizer; and - foaming the mixture with a foaming agent, such that a foamed concrete is obtained that is water and / or air permeable. The method of claim 1, wherein the plasticizer comprises a superplasticizer. A method according to claim 1 or 2, wherein 1 to 50 ml plasticizer is used per kilogram of cement, preferably 1 to 25 ml plasticizer and more preferably 1 to 12 ml plasticizer. Method according to claim 1, 2 or 3, wherein the water / cement factor is in the range of 0.3 - 0.6, preferably in the range of 0.35 - 0.55 and most preferably in the range of 0, 4 - 0.5. Method according to at least one of claims 1-4, wherein the concrete-reinforcing fibers comprise plastic fibers. The method according to at least one of claims 1 to 5, wherein 1 to 20 grams of concrete-reinforcing fibers is used per kilogram of cement, preferably 1 to 10 grams of fibers and more preferably 2 to 5 grams of fibers. Method according to at least one of claims 1-6, foaming comprising forming a foam on the basis of the foaming agent and subsequently mixing the foam with the mixture. The method of claim 7, wherein plasticizer is added to the foaming agent prior to forming the foam. A method according to at least one of claims 1-8, wherein 1 to 10 liters of foam is used per kilogram of cement, preferably 1 to 5 liters of foam and more preferably 2 to 3.5 liters of foam. The method according to at least one of claims 1-9, wherein the cement comprises a cement of strength class A or B. A method according to at least one of claims 1-10, wherein the following is added per kilogram of cement, preferably cement with strength class B: - 0.3 - 0.6 kg of water, preferably 0.35 - 0, 55 kg and most preferably 0.4 - 0.5 kg; - 1 - 5 grams of foaming agent, preferably 2-3 grams and most preferably about 2.25 grams, wherein the foaming agent preferably comprises a synthetic foaming agent; - 1 - 5 grams of plasticizer, preferably 1-3 grams and most preferably about 1.75 grams, wherein the plasticizer preferably comprises a superplasticizer; - 1 to 5 grams of concrete reinforcing fibers, preferably 2-3 grams and most preferably about 2.25 grams, wherein the fibers preferably comprise plastic fibers; and 40-160 grams of additional water for producing the foam, preferably 60-120 grams, most preferably about 80 grams. A method according to at least one of claims 1 to 11, wherein - first the water is mixed with the fibers and the cement and separately the foaming agent and the plasticizer are mixed together; and - then the mixture of water, fibers and cement is pumped, injecting the foamed mixture of foaming agent and plasticizer. Method according to claim 12, wherein the mixture of water, fibers and cement is mixed with the foamed mixture of foaming agent and plasticizer in less than 2 seconds, preferably in less than 1 second, preferably less than 0.5 second. A permeable structural member for forming a substrate, comprising a layer of foamed concrete manufactured with the method according to one of claims 1-13. 15. Permeable structural member according to claim 14, comprising a rubber top layer applied to the foam concrete layer. Use of a permeable structural member according to claim 14 or 15 as a permeable substrate.