Classifications

• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B40/00—Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability
  • C04B40/06—Inhibiting the setting, e.g. mortars of the deferred action type containing water in breakable containers ; Inhibiting the action of active ingredients
  • C04B40/0675—Mortars activated by rain, percolating or sucked-up water; Self-healing mortars or concrete
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B18/00—Use of agglomerated or waste materials or refuse as fillers for mortars, concrete or artificial stone; Treatment of agglomerated or waste materials or refuse, specially adapted to enhance their filling properties in mortars, concrete or artificial stone
  • C04B18/04—Waste materials; Refuse
  • C04B18/16—Waste materials; Refuse from building or ceramic industry
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
  • C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
  • C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
  • C04B28/04—Portland cements
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
  • C04B2111/34—Non-shrinking or non-cracking materials
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
  • Y02W30/00—Technologies for solid waste management
  • Y02W30/50—Reuse, recycling or recovery technologies
  • Y02W30/91—Use of waste materials as fillers for mortars or concrete

Definitions

• the invention relates to fresh concrete with a self-treating ability.
• the invention also relates to a dry mixture for preparing this concrete.
• Shrinkage is an inevitable phenomenon accompanying the solidification and hardening of cement composites, incl. concrete, which occurs without any external loads and practically cannot be completely removed. It is caused by an increase in tensile stress, which is caused by the loss of water in the capillary system of the concrete and the transfer of a large number of menisci (water-air interfaces) into capillaries of smaller dimensions - drying shrinkage, and the so- called autogenic shrinkage.
• the loss of water in the capillary system of concrete is caused by its evaporation from fresh concrete and its consumption during hydration reactions which take place during the drying of both hardening and hardened concrete.
• the autogenous shrinkage is then caused by the fact that the new formations, which are formed from cement paste and constitute the final solid structure of the concrete, have, at the same weight, a smaller volume than the initial cement paste.
• the period of time during which shrinkage takes place depends mainly on the size and shape of the concrete structure and on the rate of moisture loss. It can take place even several years after the concrete was placed (however, it is generally assumed that about 80 % of shrinkage occurs in the first 3 months of concrete age).
• the shrinkage of concrete can be influenced by a suitable choice of its composition and/or by its treatment after placing.
• Another approach to reduce the shrinkage rate of concrete is adding a suitable admixture or additive.
• Such an admixture is, for example, microsilica (silica fume), which is a very fine waste material from metallurgical plants with a specific surface area of 15,000 to 25,000 m 2 /kg.
• microsilica silicon fume
• Replacing approx. 10 % by weight of the dose of cement with microsilica treated to have water-repellent properties increases the contact angle between the solid phase of concrete and water and reduces the negative pressure of water in its capillary system, which results in a reduction in the rate of autogenous shrinkage of concrete; on the contrary, when untreated microsilica is used, the autogenous shrinkage increases.
• Microsilica can be combined or replaced with at least one of its known substituents, such as metakaolin, shale, ground-granulated blast-furnace slag (GGBS or GGBFS), fly ash, etc.
• substituents such as metakaolin, shale, ground-granulated blast-furnace slag (GGBS or GGBFS), fly ash, etc.
• GGBS or GGBFS ground-granulated blast-furnace slag
• fly ash fly ash
• Suitable admixtures include well-known plasticizing and superplasticizing additives and anti-shrinkage additives for concrete.
• Plasticizing additives such as lignin sulfonates, naphthalene, melamine based on vinyl copolymers or polycarboxylate derivatives, tend to reduce the surface tension of water in the capillary system of concrete, thereby reducing the shrinkage of concrete during water evaporation.
• Superplasticizers based on polypropylene glycol then make it possible to significantly reduce the dose of mixing water and cement and increase the proportion of aggregate (see Lyse's rule above) and thus reduce autogenous shrinkage of concrete.
• a larger proportion of aggregate serves as a solid obstacle to the formation of tensile stress.
• the polypropylene glycol-based shrinkage reducing admixture reduces the surface tension of water in the capillary system of concrete, especially in capillaries with a diameter of 2.5 to 50 nm, and thus limits the increase in tensile stress.
• the disadvantage of using this admixture is the slowing down of cement hydration and reducing compressive strength of concrete after 28 days, by up to 15 %.
• CZ 304133 it is known to add to the concrete mixture 0.1 to 20% by volume of hollow fibers the cavities of which are at least partially filled with water and/or with a liquid anti-shrinkage agent for concrete.
• a liquid anti-shrinkage agent for concrete for concrete.
• the liquid anti-shrinkage agent then reduces the increase in tensile stress by reducing the surface tension of the water in the capillary system of the concrete.
• cellulose fibers which, due to their absorbent nature, absorb water during the mixing of fresh concrete, which is then released into its capillary system during the solidification and hardening of the concrete.
• these fibers represent a foreign element in the structure of the concrete.
• these fibers increase the price of the concrete.
• Another well-known method is to limit the evaporation of water from the surface of the concrete structure by a suitable vapor-tight material, e.g. in the form of a spray, paint or foil.
• a suitable vapor-tight material e.g. in the form of a spray, paint or foil.
• this has only limited effectiveness, as it only objectively reduces the total water loss in the capillary system of the concrete without replenishing it.
• the object of the present invention to provide fresh concrete with a self treating ability and therefore with a limited shrinkage rate, which would eliminate the disadvantages of the background art. Furthermore, the object of the invention is a dry mixture for the preparation of this concrete.
• the object of the invention is achieved by fresh concrete which contains in 1 m 3 30 to 300 kg of water, 135 to 450 kg of cement or 135 to 600 kg of a mixture of cement and at least one substituent thereof, 1000 to 2400 kg of aggregate with an upper fraction of up to 40 mm, whereby at least 55 % by weight of the aggregate consists of natural aggregate, and further contains 10 to 300 kg of inert construction and demolition waste and/or waste from industrial production of construction products in powder form having a particle size of 5 to 250 pm, preferably 5 to 125 pm (in which even better results can be expected).
• the specific surface area of this powder is from 300 to 1500 m 2 /kg.
• the addition of inert construction and demolition waste in the form of fine powder has several major advantages.
• this powder also improves the rheological properties of the concrete and its workability and does not represent foreign component in the structure of the concrete.
• experiments have also shown that the filling of the microstructure of the concrete with this powder decreases in most cases the depth of penetration of pressurized water into the concrete. The purchase price of this powder is completely negligible, since it is de facto a waste, otherwise substantially unusable, which is produced globally in huge quantities.
• This powder is used alone in the preparation of concrete or in a pre prepared mixture with cement.
• This powder may consist of finely ground inert construction and demolition waste from demolition or construction of different types of constructions and/or of waste from industrial production of different construction products.
• a suitable powder is, for example:
• inert construction and demolition waste inert construction and demolition waste
• waste from industrial production of different construction products which consists entirely or of at least a majority of bricks (with possible admixtures of other building materials and/or substances, such as concrete, ceramic building elements and fittings, residues of mortar, plaster, construction glue, etc.), of scrap bricks, etc., or of powder which is formed during the firing and grinding of fired bricks;
• - concrete powder which is produced by the fine grinding of inert construction and demolition waste (incl. construction residues) and/or waste from industrial production of different construction products, which consists entirely or of at least a majority of concrete (with possible admixtures of other building materials and/or substances, such as bricks, ceramic building elements and fittings, residues of mortar, plaster, construction glue, etc.), or scrap concrete products and prefabricated parts, etc., or powder generated by grinding concrete, etc.;
• - ceramic powder which is produced by the fine grinding of inert construction and demolition waste (incl. construction residues ) and/or of waste from industrial production of different construction products, which consists entirely or of at least a majority of ceramic building and fitting elements, e.g.
• floor and wall tiles sanitary ceramic products, clay roofing tiles, etc. (with possible admixtures of other building materials and/or substances, such as concrete, bricks, residues of mortar, plaster, construction glue, etc.), or of scrap ceramic products, their shards, etc.;
• inert construction and demolition waste which is produced by the fine grinding of mixed inert construction and demolition waste (incl. construction residues ) and/or of waste from industrial production of construction products, which is formed by a mixture of different construction products and substances, usually of bricks, concrete and ceramic building elements and fittings in different proportions (with a possible admixture of residues of mortar, plaster, gypsum, construction glue etc.), or is formed by mixing two or more above-mentioned powders (brick, ceramic, concrete powder), etc.
• At least 20 % by weight of this powder consists of concrete powder and/or mortar powder, since this material contains a plurality of non-hydrated cement grains which, in combination with the absorbency of this powder, make it possible to achieve a greater degree of hydration during concrete maturation and thus to achieve higher concrete strength and/or reduce the required cement dose, thereby reducing also the rate of the autogenous shrinkage of this concrete.
• the resulting concrete it is possible to replace up to 40 % by weight, preferably up to 20 % by weight or up to 15 % by weight of the total content of aggregate in the concrete with artificial aggregate (such as agloporite, ceramsite, expandit, expanded perlite, etc.) and/or cinder and/or scoria and/or polystyrene and/or at least one organic filler (such as wood sawdust, shavings, rice husks, shives, etc.), and/or another component for improving thermal and/or acoustic and/or fire resistance properties of hardened concrete.
• artificial aggregate such as agloporite, ceramsite, expandit, expanded perlite, etc.
• cinder and/or scoria and/or polystyrene and/or at least one organic filler (such as wood sawdust, shavings, rice husks, shives, etc.), and/or another component for improving thermal and/or acoustic and/or fire resistance properties of hardened concrete
• up to 45 % by weight of aggregate may consist of recyclate from inert construction waste - brick recyclate and/or ceramic recyclate and/or concrete recyclate and/or mixed recyclate having a particle size of up to 24 mm.
• brick recyclate refers to a recycled material produced by the crushing or grinding of inert construction and demolition waste (incl. construction residues and/or waste from industrial production of construction products), which consists entirely or of at least a majority of bricks, with possible admixtures of other building materials and/or substances (concrete, ceramic building elements and fittings, residues of mortar, plaster and construction glue, etc.).
• brick recyclate consists entirely or of at least a majority of crushed brick, possibly with the addition of rubble from other building materials and/or substances.
• ceramic recyclate refers to a recycled material produced by the crushing or grinding of inert construction and demolition waste (incl. construction residues and/or waste from industrial production of construction products), which consists entirely or of at least a majority of ceramic building and fitting elements, such as floor and wall tiles, sanitary ceramic products, clay roofing tiles, etc., with possible admixtures of other building materials and/or substances (concrete, bricks, residues of mortar, plaster, construction glue, etc.).
• ceramic recyclate consists entirely or of at least a majority of crushed ceramics, possibly with the addition of rubble from other building materials and/or substances.
• concrete recyclate refers to a recycled material produced by the crushing or grinding of inert construction and demolition waste (incl. construction residues and/or waste from industrial production of construction products), which consists entirely or of at least a majority of concrete or another cement containing material (e.g. concrete screed, cement mortar, etc.), and optionally with admixtures of other building materials or substances (bricks, ceramic building elements and fittings, residues of mortar, plaster, construction glue, etc.).
• cement recyclate consists entirely or at least of a majority of crushed concrete or another cement containing material, possibly with the addition of rubble from other building materials and/or substances.
• mixed recyclate refers to a recycled material made by the crushing or grinding of mixed inert construction and demolition waste (construction residues and/or waste from industrial production of construction products), which is formed by a mixture of different building materials and substances, usually bricks, concrete and ceramic building elements and fittings in different proportions, optionally with admixtures of residues of mortar, plaster, construction glue, etc., or recyclate formed by mixing two or more above- mentioned recyclates (brick, ceramic, concrete powder).
• the mixed recyclate thus consists of mixed crushed or ground rubble from construction and demolition waste.
• the upper fraction of natural aggregate is, according to the requirements for the use and texture of the concrete, up to 40 mm, preferably, e.g., up to 16, 20 or 24 mm.
• the aggregate can have one fraction, e.g., a fraction of 0 to 40 mm, preferably, e.g., 0 to 12 mm or 0 to 16 mm; or it can have two fractions, e.g. fractions of 0 to 20 mm and 20 to 40 mm, preferably, e.g., 0 to 8 mm and 8 to 32 mm or 0 to 16 mm and 16 to 32 mm, or it can have three fractions, e.g.
• fractions of 0 to 8 mm, 8 to 20 mm and 20 to 40 mm preferably, e.g., 0 to 4 mm, 4 to 8 mm and 8 to 16 mm, etc.
• aggregates With an upper fraction of up to 8 mm.
• the powder which is composed of finely ground inert construction and demolition waste and/or waste from industrial production of construction products, fills the pores in the grains of the aggregate during mixing of the concrete, as a result of which part of the transit zone (CSH phase) moves into the pores of the aggregate, thanks to which is this zone strengthened and the individual grains of the recyclate are strengthened as well. Consequently, the resulting concrete achieves better mechanical parameters.
• the concrete according to the invention in any variant may contain at least one known additive and/or admixture, such as microsilica (silica fume) and/or at least one known substituent thereof, such as. metakaolin, shale, ground-granulated blast-furnace slag (GGBS or GGBFS), fly ash, micronized limestone, etc., or reinforcing fibers of at least one type which reinforce the structure of the concrete and thereby improve some of its properties, such as tensile strength and flexural tensile strength.
• microsilica silicon fume
• substituent thereof such as. metakaolin, shale, ground-granulated blast-furnace slag (GGBS or GGBFS), fly ash, micronized limestone, etc.
• the suitable reinforcing fibers include, e.g., polypropylene (PP) fibers, polyvinyl alcohol (PVA) fibers, blends of polypropylene and polyethylene (PLV) fibers, cellulose fibers, steel fibers, glass fibers, carbon fibers, Kevlar fibers, etc. These fibers are typically added to the concrete mixture in an amount of 0.6 to 1.2 kg/m 3 of fresh concrete, in the case of steel and similar fibers in an amount of up to 25 kg/m 3 of fresh concrete.
• Another suitable additive may be any known additive, for example an additive intended for vibro-pressed concrete and/or additives according to EN 934-2.
• these additives also include additives for improving the consistency of concrete, water- reducing additives (plasticizing, superplasticizing, hyperplasticizing and the like), additives for improving the strength and some other properties of fresh and hardened concrete, as well as stabilizing additives, air-entraining admixtures, foaming agents, additives accelerating solidification and hardening of concrete, additives retarding solidification and hardening of concrete, sealing agents, corrosion inhibiting additives, etc.
• This additive/these additives is/are preferably added to the other components of concrete dissolved in mixing water or alone, preferably after the addition of the mixing water.
• the total amount of all added additives for concrete is up to 10 % by weight of the dose of cement or of the dose of cement and its substituent/substituents.
• the fresh concrete according to the invention can be prepared by any known method of preparing concrete using any method of dosing the individual components.
• a dry mixture for preparing fresh concrete with a self-treating ability according to the invention has an analogous composition, but does not contain water or any plasticizer; those are usually added to it at the concreting site, e.g., when being processed with continuous mixers.
• a total of 18 examples of concrete according to the invention are given below for illustration, including their comparison to a reference concrete according to the background art. Examples of embodiment Example 1
• ERC 1/19 a reference concrete was prepared (hereinafter referred to as ERC 1/19), which did not contain inert construction and demolition waste and/or industrial waste from production of construction products in powder form with a particle size of 5 to 250 pm.
• ERC 2/19 to ERC 10/19 9 samples of concrete were prepared (hereinafter referred to as ERC 2/19 to ERC 10/19) which had the same or very similar composition as the reference concrete, but which also contained different proportions of different types of construction and demolition waste and/or industrial waste from production of construction products in powder form with a particle size of 5 to 250 pm.
• Example 2 Four other samples of concrete were prepared by the same procedure as in Example 1. The samples contained different proportions of different types of construction and demolition waste and/or industrial waste from production of construction products in powder form with a particle size of 5 to 250 pm and at the same time did not contain any plasticizers.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Ceramic Engineering (AREA)
• Materials Engineering (AREA)
• Structural Engineering (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Inorganic Chemistry (AREA)
• Civil Engineering (AREA)
• Environmental & Geological Engineering (AREA)
• Curing Cements, Concrete, And Artificial Stone (AREA)

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Citations (6)

• 2020
  • 2020-02-18 CZ CZ202079A patent/CZ202079A3/cs unknown
  • 2020-08-18 WO PCT/CZ2020/050054 patent/WO2021164794A1/en not_active Ceased

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