Classifications

• • E—FIXED CONSTRUCTIONS
  • E04—BUILDING
  • E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
  • E04C2/00—Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels
  • E04C2/02—Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels characterised by specified materials
  • E04C2/26—Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels characterised by specified materials composed of materials covered by two or more of groups E04C2/04, E04C2/08, E04C2/10 or of materials covered by one of these groups with a material not specified in one of the groups
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B28—WORKING CEMENT, CLAY, OR STONE
  • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
  • B28B1/00—Producing shaped prefabricated articles from the material
  • B28B1/008—Producing shaped prefabricated articles from the material made from two or more materials having different characteristics or properties
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B28—WORKING CEMENT, CLAY, OR STONE
  • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
  • B28B1/00—Producing shaped prefabricated articles from the material
  • B28B1/14—Producing shaped prefabricated articles from the material by simple casting, the material being neither forcibly fed nor positively compacted
  • B28B1/16—Producing shaped prefabricated articles from the material by simple casting, the material being neither forcibly fed nor positively compacted for producing layered articles

Definitions

• the present invention refers to a method of producing concrete structures with a surface protection on the underlying concrete, by casting the latter and at least a surface layer substantially "wet in wet", as well as a concrete structure with a surface protection in form of a surface layer, which is integrated with the under concrete by having the latter and the surface layer made substantially through a "wet in wet"-process.
• Concrete structure surfaces and surface layers have a significant importance for the technical lifespan of the structure. They completely determine the look or, with other words, are essential for the aesthetic quality of the concrete structures. Other technical characteristics that are bound to surfaces are wearing qualities, resistance against high point loads and impact resistance. For outdoor structures, it is those surfaces that are broken down by frost influence, erosion and chemical attack.
• the ground to concrete structures life-span lies in the protection of the reinforcement.
• the concrete that covers the reinforcement constitutes as it is well known the corrosion protection.
• the choice of concrete is guided almost exclusively by the characteristics that are required for the concrete to be a satisfactory reinforcement protection.
• the strength requirement for the structures, which are produced with present standards is about to be automatically fulfilled.
• the concrete is provided with a strength, which in some cases widely exceeds what is needed for the carrying capacity. With present production technics, one is forced to choose the same high concrete quality throughout a whole concrete structure even if it is only in the surface layer that the highest set requirements on the characteristics are set.
• SE-B-321 178 describes a method to produce building element with different density in different cross section parts under use of the same binding agent.
• porous light concrete element with a dense front surface are produced by placing in a casting mould against the mould surface slices of asbestos fibres and binding agent that are partly steam hardened and that space behind the slices is filled with a pore building light concrete mass. After the light concrete has bound up and solidified in the mould, it is steam hardened in an autoclave at a temperature that is higher than 150°C.
• the production of pre-prepared slices as well as the autoclave processing of the entire building block make the manufacture more expensive and make the procedure applicable only to prefabrication.
• composite concrete plates are produced, where the surface layer respectively layers are put to solidifying at increased temperature before the central core of light concrete is poured.
• the contact surface is coated with an adhesive polish. Not any kind of stress under compression is produced between the different layers.
• the object of the invention is to produce different types of surface layer on concrete at manufacturing.
• the surface layer shall have the possibility to completely cooperate with the underlying concrete, shall reinforce the protection in structures the environment conditions of, which have changed with time, shall in special cases be able to reduce the requirement on the covering concrete layer, and shall as extra protection further improve the durability in important structure parts even in extremely aggressive environment. This has been achieved through a method of producing concrete structures with a surface protection on the underlying concrete, by casting it and at least a surface layer substantially "wet in wet".
• the invention is based consequently on giving rise to pressure strains in the surface layer in concrete structures. These pressure strains are created by deformation differences in the surface layer and the underlying concrete. The deformations are caused by shrinkage and the drying shrinkage that arise after the hardening is concerned above all.
• the ended shrinkage can be regarded as being reached when a moisture balance has been set with the .surrounding.
• the prerequisite is consequently that the surface layer and the underlying concrete material have different shrinkage magnitude and that the shrinkage of the surface layer is smaller than the underlying concrete. This can generally be fulfilled when the surface layer is made of mortar or concrete with high strengths or of other material, which does not have after-shrinkage and if the underlying concrete is of the lightweight type.
• Lightweight concrete has a low elastic modulus and gives therefore a limited obstacle for the shrinkage. It is a necessary condition that the so-called relaxations that are generated between the surface layer and the existing under-concrete must be able to be carried up without the separating of the surface layer to occur. This problem can be solved by resorting to particular actions in the transition zone associated with the casting.
• the pressure strains in the surface layer are approximately 10-15 Mpa and pulling strains in the underlying concrete 1/10 thereof.
• the maximum pressure strain in the surface layer is reduced with some more than 20% and the maximum pulling strain in the underlying concrete with less than 10%. The biggest deflection is approximately 1/400 of the span when this one is 1.2 m.
• the shrinkage strains will get different magnitude. The difference is caused by the separation of the aggregate particles so that different aggregate volume shares arise within the layer, low percentage in the upper part. When the volume percentage is reduced from 0.7 to 0.35, i.e. halved, the shrinkage increases about four times.
• the results can then be that the less shrinking operative thickness of the surface layer becomes thinner, the pressure strains bigger and the bending smaller. Through intentionally arisen sedimentation of aggregate particles in the surface layer, a successive increase of the shrinkage and a reduction of the pressure strains in the direction of the underlying concrete appear.
• Lightweight concrete elastic modulus is 6000-7000 Mpa and its shrinkage (end shrinkage) at 50% relative air humidity is at least 0.9 fe.
• the strains in the surface layer will not become as big as in a glass surface layer where strains of up to 140 Mpa can arise after the hardening.
• the goal is however not the same with concrete material even if similarities are found.
• the following can be achieved with thin surface layers:
• Aesthetic effects Great freedom to colour surfaces with long durability, among other by pigment inking, good possibilities to create surface structures, such as reliefs, smooth and even surfaces with possibly high lustre (without grinding) and, in the manufacturing process, to create flexible surfaces with the mosaic technique.
• a material that is particularly adapted to combination is, for surface layers, cement bound mortar with low water binding agent ratio, equivalent to a binding agent strength in general over 70 Mpa.
• lightweight concrete with dense structure has appeared particularly appropriate, for example the lightweight concrete with density in the range 800-1500 kg/m 3 mentioned in SE-B-8305474-2.
• This concrete type is a structure concrete with approximately half the density of normal concrete, strengthen in the area 10 - 20 Mpa, contains high air entrained volume in cement paste, has hydrophobic characteristics and is open for diffusion with regard to water vapour. Drying shrinkage is further about three times bigger than for the high-test concrete with particular high strength, which can be chosen for the surface layer.
• Even concrete types with usual heavy aggregate material is possible to use as underlying concrete with density about 2300 kg/m 3 .
• thermosetting resin such as epoxy and urethane as well as combinations between polymers and cement.
• thermosetting resin such as epoxy and urethane
• combinations between polymers and cement are of the type that corresponds to modified polymer concrete in, which hydraulic binding agents cooperates with polymer dispersions, for example based on acrylic and styrene butadiene.
• the surface layer consisting of merely thermosetting resin, should be chosen with little thickness, from 100 ⁇ m to 1 - 2 mm.
• the advantage to fix the polymer layer in connection with the concrete casting is that the polymer becomes completely tight. Pore formation that forms frequently channels in polymer layer occurs when the layer is applied on hardened concrete surfaces. Polymer types must be compatible with non hardened concrete.
• the hydraulic binding agent is based partly on Portlandcement, which can be regarded as calcium silicate- cement and partly on calcium aluminate-cement. Particular to Portlandcement are added different agents and supplemental material to change the characteristics in both the fresh and the hardened stadium. In the modern concrete there is foremost the binding agent, which has changed by means of combinations of additive and supplemental material. With additive is meant topics, which in a little amount can change the chemical and physical characteristics. To these belongs ,as an example dispersing, even called wetting and water reducing, accelerating, retarding air pore creating, tightening and hydrophobing. Supplemental material are those, which cooperates with Portlandcement as binding agent, such as puzzolanics (microsilica and fly ash) and latent hydraulic binding agent (granulated slag).
• puzzolanics microsilica and fly ash
• latent hydraulic binding agent granulated slag
• the particle size of the aggregate material is limited. Maximum aggregate size should not outreach half the thickness of the layer. If the largest aggregate size is 2 mm the thickness of the layer as a rule should be at least 4 mm.
• the minerals or the kind of rocks that is suitable for surface layer is the same as normal is used in usual concrete, with same demand with regard to for example durability, strength and wear resistance.
• the colour of the aggregates cooperates with the colour, which the surface layer shall have. Normally the aggregates shall be light when the surface layer shall have light nuance. Pigment added to the binding agent and thereto adapted aggregate material enables big variation in the colour of the surface layer.
• the structure of the surface layer is determined by the form material.
• the casting becomes a copy of the surface of the form.
• form material When using most of form material for concrete casting the form material must be covered by some type of release agent, form oil. In many cases the form oil has negative impact on the concrete surface, such as discolouration and problem in connection with later surface treatment.
• the polymer modified binding agent and particular layer of thermosetting plastics demand special release agent. The choice of form material in these cases are important. General requirement is to avoid all forms of form oils, which can influence the surfaces.
• the surface layer is moulded in a lying form and is vibrated, e.g. by form vibrators, to compress the material, to obtain an even thickness as well as to drive out eventual air-bubbles.
• the layer thickness being small, one obtains entirely pore free surfaces.
• Underlying concrete, for example light concrete, is suitably moulded immediately after that the surface layer laying is finished.
• the surface layer and the underlying concrete can be reinforced with conventional material, for example fibre reinforcement and usual reinforcement in the underlying concrete.
• conventional material for example fibre reinforcement and usual reinforcement in the underlying concrete.
• the concrete material, which is chosen as underlying concrete has approximately the half of the density of the surface layer material the penetration is avoided.
• extra fibres can be scattered on the newly moulded surface layer, which both reinforces and constitutes the carrying surface for the weight, which is applied from conventional reinforcement without using distance spacer to ensure a determined coat layer thickness.
• Distance models gives visible marks on the surface and makes a possible risk to leak arise.
• the surface layer is compound according to the valid requirement, for example durable surface, which resist high concentrated loads.
• the surface can also be given a determined colour.
• super wetting agents mortar with very loose consistence with ability to float out during the casting can be obtained.
• the ballast particles in the mortar can be allowed to separate so that the volume share of particles in the bottom are higher than the average for the layer. This is for advantage to surface hardness and durability.
• the top of the layer instead becomes poor of ballast particles.
• This separation layer which mainly consists of paste gives a successive transfer to the top concrete without a sharp border between the two materials. The tension gradients in the transition thereby becomes smaller. In extreme cases, this layer can be blocking layer to increase the stroke resistance by energy absorption and energy distribution.
• a double layer can be moulded in such case and to reinforce the effect of the middle layer and increase the resistance for blow and strokes.
• Some type of polymer dispersion can be added in the first mortar layer or fibre in the blocking layer. Same technic is basically the basis for the structure of bulletproof glass.
• Air pore builder in the mortar open the ballast material by gas or cavity mortar, i.e. mortar with deficit of cement past can be a possible solution when dense surface layer must be avoided.
• Polymer dispersions are added to the recipe examples 1 - 7 with polymer amount that corresponds to 2-15% of the weight binding agent.
• Grounded granulated cinder which activates with alkalis, sulphate lime etc. can constitute the binding agent, specially the increased chemical permanence (acid attack) and block against penetration of chloride is intended to be achieved.
• Examples of surface layer of polymers or thermosetting plastics are epoxy, urethane and polyester. To combine these with fresh concrete, which consequently has not hardened the same principles should be valid for the function, namely that the surface layer should have full adhesion in the mortar state against the concrete and that pressure tensions are developed. Since shrinkage of the polymer layer above all is bound to the polymerization, the shrinking in later phase is insignificant. Furthermore, epoxy has hardly any shrinkage at the polymerization unlike, for example polyester types.

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• Engineering & Computer Science (AREA)
• Ceramic Engineering (AREA)
• Architecture (AREA)
• Mechanical Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Chemical & Material Sciences (AREA)
• Structural Engineering (AREA)
• Civil Engineering (AREA)
• Curing Cements, Concrete, And Artificial Stone (AREA)
• Manufacturing Of Tubular Articles Or Embedded Moulded Articles (AREA)
• Panels For Use In Building Construction (AREA)
• Laminated Bodies (AREA)
• Road Paving Structures (AREA)

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• 1993
  • 1993-06-18 SE SE9302118A patent/SE9302118L/sv not_active IP Right Cessation
• 1994
  • 1994-06-09 AU AU70874/94A patent/AU7087494A/en not_active Abandoned
  • 1994-06-09 DE DE4494457T patent/DE4494457T1/de not_active Withdrawn
  • 1994-06-09 WO PCT/SE1994/000558 patent/WO1995000305A1/en active Application Filing
  • 1994-06-09 US US08/569,080 patent/US5797238A/en not_active Expired - Fee Related

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