WO2017149207A1

WO2017149207A1 - Method for manufacturing of concrete and concrete product

Info

Publication number: WO2017149207A1
Application number: PCT/FI2017/050146
Authority: WO
Inventors: Raija KORHONEN; Seppo Saarelainen; Sirkku SAARELAINEN
Original assignee: Invest Saarelainen Oy
Priority date: 2016-03-04
Filing date: 2017-03-03
Publication date: 2017-09-08

Abstract

The invention relates to a method for manufacturing of concrete in which silane is added into fresh concrete. Furthermore, the invention relates to a concrete product which includes aggregate, cement, water and additives, the additive being silane.

Description

METHOD FOR MANUFACTURING OF CONCRETE AND CONCRETE PRODUCT

The invention relates to a method for manufacturing of concrete and a concrete product manufactured by the method. Concrete is manufactured by mixing aggregate, cement, water and additives. The purpose of additives is to increase the strength and weather-resistance of concrete, facilitate its processibility and increase its life and/or chemical durability.

Air-entraining agents commonly used in connection with manufacturing fresh concrete decrease the surface tension of concrete water and create a desired number of air voids in concrete leaving freezing water space to expand and thus increasing the weather-resistance of concrete. Penetration of water, i.e. the capillary action, in finished concrete products has not been resolved by additives but the aim is to solve the problem by various coatings.

The mixture of cement and water is called cement paste. Cement paste facilitates pasting natural aggregate grains together and, of thus created fresh concrete, it is possible to cast pieces of desired shape. When the cement paste has been set, it is called cement stone. Hardened concrete consists of cement stone and natural stone grains. When trying to pass through hardened concrete, water cannot penetrate a single natural stone grain but it finds its way through cement stone including various voids. Fig. 1 shows a diagram of the internal construction of concrete. Cement stone includes voids of various sizes. They are: 1. compaction voids, 2. protective voids, 3. capillary voids and 4. gel voids.

Gel voids are small voids of the size of about a nanometre (about 0.0000005- 0.00005 mm) and filled with water. Gel voids constitute about 25-30% of the total volume of cement gel.

When there is too much water in cement paste, larger water- filled spaces, which gel crystals cannot fill, remain between cement particles. Spaces created this way are called capillary voids. They are created of extra water in cement paste which has not been adhered in hydration or got into gel voids. The number of capillary voids is strongly dependent on the water-cement ratio water mass / cement mass. Capillary voids are very harmful to concrete because, through them, water is able to be absorbed very efficiently into concrete from the effect of capillary forces. The cement stone of common K20 concrete used in interior spaces consists for about half of capillary voids, i.e. sole air. There are the more of capillary voids, the greater the water-cement ratio is and the younger the concrete is. The size of capillary voids is about 1 micrometre (about 0.00005-0.05 mm). Water in them is able to move and freeze.

Protective voids are provided in concrete by means of the so-called air-entraining agents to increase the resistance to freezing and thawing of concrete. Compared with capillary voids, the protective voids are large, of the size of about 0.1 mm (about 0.01-0.3 mm).

Compaction voids are created during casting on surfaces being against the mould when air and water gather in the barrier between the mould and the concrete. Their size is about 1 mm (about 0.5-5 mm).

Disadvantages of previously utilised waterproofing arrangements

Currently, waterproofing is provided by various coatings or other products or product combinations applied onto the concrete surface construction. Coatings on the market are powdery products which are used to coat concrete products. In them, an active catalyst actuates the formation of crystals to prevent the capillary action. Separate mechanical coatings require maintenance and they must be replaced regularly in order to ensure waterproofness. This leads to the fact that, due to maintenance and long-lasting repair and alteration works, facilities/properties are out of use, whereby the return of the facilities or properties decreases. Furthermore, installing coatings in awkward positions increases water leakage risks.

Installing coatings is one of the most critical points of constructions and the instructing and supervision of coating work demands a lot of resources. E.g. in the case of a bridge deck, waterproofing work requires a weather guard.

An object of the invention is to introduce a manufacturing method of fresh concrete which provides totally waterproof, aerated fresh concrete. A further object of the invention is to introduce a concrete product in which water cannot penetrate.

The object of the invention is achieved by a concrete manufacturing method and a concrete product which are characterised by what is presented in the claims.

The concrete manufacturing method according to the invention is characterised by adding silane into fresh concrete. Silanes and their compounds are totally compatible with cement and they do not cause a counterreaction, such as e.g. silicones or equivalents do. As an additive, silane blocks the capillary voids and gel voids of cement stone, whereby water cannot be absorbed into concrete through them. Silanes react with the components of cement forming small brush-like nano- molecule hairs evenly throughout fresh concrete. These molecule hairs have an extremely large area which changes the incidence angle of water such that water cannot penetrate concrete. The phenomenon is evident in the spherical shapes of water drops which remain on the surface of the concrete product. In nature, this phenomenon is known as the Lotus effect. Because chemical insulation is formed throughout fresh concrete, it works even though holes were drilled in the concrete or pieces were split of it. In the method according to the invention, silane compounds, such as triethoxyoctylsilane or equivalents, are advantageously added into fresh concrete.

One additive in the concrete product according to the invention is silane. Then, the construction of fresh concrete forms a waterproof construction throughout in which water cannot penetrate into capillary voids and thus proceed in concrete voids decaying constructions and creating humidity problems. Waterproofness is also inside the product, not only on its surface.

The method and the product according to the invention provide several advantages.

A waterproof, compact concrete construction will be more ecological than previous ones because waterproofing is omitted from the construction. Building will speed up and become simpler when waterproofing and coating stages are excluded. Possible concrete aeration is omitted, whereby material and work costs will decrease. Along with the invention, concrete constructions will become safer preventing mould from being created, because humidity cannot penetrate / move inside the concrete constructions. The structural dryness and strength of hardened concrete will be attained quicker than when using normal fresh concretes. The waterproof construction will be quickly ready for further treatment as the building project proceeds, which enables quicker and safe building because it is possible to decrease the amount of water used in concrete element constructions.

The cost-efficiency of connections will improve considerably when insulation structures are left out.

The frost-resistance and cyclicity of the construction will be better than earlier because of the construction being more homogenous. The long-term durability of the constructions will be better, the value of the constructions and the property higher and maintenance costs smaller than in conventional arrangements. Waterproof concrete will also be frost-resistant because nano silane does not block the protective voids of cement stone.

Fresh concrete manufactured by means of the method according to the invention and concrete products manufactured are used in waterproof external and internal constructions, such as e.g. concrete bridges, exterior wall constructions, building foundations, walls, floor concretings, parking facilities and other constructions which require waterproofness. Particularly, the product can be used in swimming pools, fish-farming tanks and equivalents. E.g. in the case of a bridge deck, no separate weather guard is required. Waterproof concrete can be utilised in manufacturing elements required in various constructions which are e.g. bridge decks, founding elements, soil pressure walls, tiles and beams. Waterproof concrete enables developing new applications which have not earlier been possible to manufacture from concrete.

The method and materials can also be used in ready-mixed concrete when casting constructions on the work site.

Technical description

Limit values of waterproofness in measuring pressurised water penetration according to Standard SFS EN 12390-8 are the following: Concrete is somewhat waterproof when water penetration is at the most 100 mm, whereby a test piece has been abundantly impregnated with water for the depth of 100 mm. Abundant impregnation with water means that over 50%, typically at least about 70%, extremely typically at least about 80%, sometimes at least about 90% of the capillary and compaction voids of concrete are filled with water. Sometimes, substantially all of the capillary and compaction voids can then be filled with water, whereby only the protective voids of concrete are filled with air. Concrete is totally waterproof when there is no water penetration or it is at the most 1 mm considering the inaccuracy of measurement, whereby the test piece is totally dry. Totally dry means that over 50%, typically at least about 70%, extremely typically at least about 80%, sometimes at least about 90% of the capillary and compaction voids of concrete are not filled with water.

Fresh concretes contain aggregate for about 58-72 volumetric percentages, typically about 64 volumetric percentages, also a smaller amount of 58 volumetric percentages or a larger amount of even about 72 volumetric percentages is possible. Fresh concretes contain cement for about 7-19 volumetric percentages, typically about 12 volumetric percentages, sometimes a smaller amount of 7 volumetric percentages or a larger amount of even about 19 volumetric percentages is possible. Fresh concretes contain water for about 15-30 volumetric percentages, typically about 19 volumetric percentages, sometimes a smaller amount of about 15 volumetric percentages or a larger amount of even about 30 volumetric percentages is possible.

TESTING

In the test, fresh concrete according to the invention was manufactured by mixing 385 kg of cement, 1,772.9 kg of aggregate and batched water, the total of 130.7 kg, of which 9.4 kg was replaced by polymer water containing silane. Concrete was of the K45-1 type. It is easy to add agent replacing liquid according to the invention because the volume weight of the additive used in the invention, i.e. polymer water containing silane, is almost the same as that of water.

The samples were examined in the accredited building laboratory of the Technical Unit at the Oulu University of Applied Sciences on 17 February 2015 utilising the principles of the water penetration test according to Standard SFS-EN 12390-8. The test showed that the tested piece did not allow water to penetrate the piece and, thus, the capillary action is also not possible.

At the Savonia University of Applied Sciences, air void parameter determination, method A and test R003-00-2010 according to Standard ASTM C457 were performed of a polished section. The result of the resistance to freezing and thawing test was that the void division of protective voids was 0.25 mm (requirement at the most 0.36 mm), i.e., the test fulfilled the resistance to freezing and thawing requirement. Table 1. Test values for concrete which was manufactured by the method according to the invention:

Temperature of fresh concrete +14 degrees C

Slump immediately 100 mm after 30 minutes 90 mm after 60 minutes 50 mm Density immediately 2,390 kg/m³ after 30 minutes 2,390 kg/ m³ after 60 minutes 2,390 kg/ m³ Air content (volumetric percentages) immediately 4.5 after 30 minutes 4.4 after 60 minutes 4.3

HARDENED CONCRETE Density, kg/m³ 28 d 2,380

Compressive strength, MPa

1 d 29.0

7 d 48.0

28 d 57.0 Void division 0.25

Water penetration 1 mm

It is also possible to use the liquid according to the invention, i.e. polymer water containing silane, in considerably larger or smaller quantities than mentioned in the examples above depending on the purpose of use, qualities of aggregates and other additives, such as e.g. various fibres. There can be silanes for about half of the product (50%). The quantity of silalanes can still vary in various embodiments and be about 30-60% of the liquid, and advantageously about 40-60% or advantageously 45-55%. Polymer water containing silane used in the method can also be utilised for concrete jointing, second stage concreting and expanded clay aggregate concrete products. It is obvious to those skilled in the art that the invention will not be limited only to the above examples but it can vary within the scope of the claims presented later.

Claims

1. A method for manufacturing of concrete, characterised by adding silane to fresh concrete.

2. A method for manufacturing of concrete according to claim 1, characterised in that into fresh concrete are added silane compounds, triethoxyoctylsilane or equivalents.

3. A concrete product which includes aggregate, cement, water and additives, characterised in that the additive is silane.

4. A concrete product according to claim 3, characterised in that the additives are silane compounds, triethoxyoctylsilane or equivalents.