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
  • 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
  • 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
• • 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 a method for preparing fresh concrete using 5 recyclate from inert construction and demolition waste.
• the invention also relates to fresh concrete prepared by this method.
• Crushed or ground inert construction and 15 demolition waste is used mainly for packs and backfills of utility lines (a substitute for sorted gravel), as a sub-base for parking lots, roads, concrete structures of floors of buildings and halls, backfills of forefields of bridges, for the consolidation and levelling of forest and field roads (a substitute for a crusher-run materials), or as a sub-base filler of ground bodies of driveways and 20 roads, trackbeds, flood protection barriers (as a substitute for soil), etc.
• the object of the present invention to provide a method for the preparation of concretes by replacing the largest possible part of aggregate with recyclate produced by grinding or crushing inert construction and demolition waste, which would enable to prepare concretes with mechanical and physical parameters comparable to conventional concretes, while not requiring an extra addition of cement or any other component. Furthermore, the object of the invention is to provide fresh concrete in which the largest possible part of the aggregate is made up of recycled material produced by grinding or crushing inert construction and demolition waste.
• the method for the preparation of concrete according to the invention is based on a combination of a specific composition of the concrete and a specific procedure of mixing and dosing its components, which in mutual combination allow to replace up to 100 % by weight of the aggregate in the concrete with recyclate made from inert construction and demolition waste (i.e. ground or crushed inert construction and demolition waste) while achieving mechanical and physical parameters which are at least comparable to or even better than, conventional concretes.
• inert construction and demolition waste i.e. ground or crushed inert construction and demolition waste
• the fresh concrete thus prepared contains in 1 m 3 50 to 300 kg of water, 135 to 400 kg of cement or 135 to 600 kg of a mixture of cement and at least one substituent thereof, 10 to 27.9 kg of microsilica (preferably compacted) or at least one substituent thereof or a mixture of microsilica and at least one substituent thereof, 1000 to 2300 kg of aggregate, whereby 30 to 100 % by weight of the aggregate is formed by brick or ceramic or mixed recyclate made from inert construction and demolition waste, 0 to 40 % by weight of the aggregate consists of natural aggregate and another 0 to 40 % by weight of the aggregate consists of lightweight 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
• the used recyclate from inert construction waste can have substantially any fraction depending on the use of the concrete and requirements for its texture - it may be, for example, one-fractional, preferably having a fraction of 0 to 20 mm, two-fractional, preferably having fractions of 0 to 8 mm and 8 to 20 mm, or three-fractional, preferably having fractions of 0 to 4 mm, 4 to 8 mm and 8 to 20 mm.
• recyclate and aggregate with a fraction of up to 16 mm or up to 8 mm can be used.
• brick recyclate a recycled material produced by crushing or milling inert construction and demolition waste, which consists entirely or of at least a majority of bricks and possibly contains other building materials and/or substances (concrete, ceramic building elements and fittings, mortar, plaster and adhesive residues, etc.).
• brick recyclate consists entirely or of at least of a majority of crushed brick, possibly with the addition of rubble from other building materials and/or substances.
• ceramic recyclate we understand a recycled material produced by crushing or milling inert construction and demolition waste, 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., and possibly contains other building materials and/or substances (concrete, bricks, mortar, plaster and adhesive residues, 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 we mean a recycled material produced by crushing or milling inert construction and demolition waste, which consists entirely or of at least a majority of concrete or another cement containing material (concrete screed, cement mortar, etc.), and possibly with admixtures of other building materials and/or substances (bricks, ceramic building and fitting objects, mortar, plaster and adhesive residues, etc.).
• concrete recyclate consists entirely or of at least a majority of crushed concrete or other cement containing materials, possibly with the addition of rubble from other building materials and/or substances.
• mixed recyclate a recycled material produced by crushing or milling mixed inert construction and demolition waste, which is composed of a mixture of different building materials and substances, usually bricks, concrete and ceramic building elements and fittings in various ratios, possibly with admixtures of mortar, plaster and adhesive residues, etc., or recyclate produced by mixing two or more above-mentioned recyclates (brick, ceramic, concrete)
• mixed recyclate is composed of mixed rubble made from construction and demolition waste.
• fresh concrete with a finer texture is prepared, sometimes referred to as cement mortar or concrete mortar.
• the fresh concrete according to the invention may contain in any variant at least one additive for concrete in a total amount of up to 10 % by weight of a dose of cement or of a dose of cement and substituent(s) thereof.
• any known additive can be used, for example additive for vibro-pressed concrete and/or additives according to EN 934-2.
• additives include especially water- reducing (plasticizing) and strongly water-reducing (superplasticizing or hyperplasticizing) additives, additives for improving the consistency of concrete, water- reducing additives, 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 hardening and solidification of concrete, additives for retarding hardening and solidification of concrete, sealing agents, corrosion inhibiting additives, etc.
• This additive/these additives is/are added to the other components of concrete dissolved in mixing water or separately, preferably after the addition of the mixing water.
• any industrial mixers can be used, for example planetary mixers, rotor mixers, single shaft mixers, dual shaft mixers or triple shaft mixers, trough mixers, continuous mixers, etc.
• a mixer with a forced circulation is especially advantageous, preferably a mixer with radial movement of mixing arms or with double simultaneous radial movement of mixing arms (such as the mixer described in IT 1244970 or in EP 0508962), in which all its interior surfaces are wiped. Nevertheless, it is necessary to observe not only the above-mentioned concrete composition, but also the mixing and dosing times of the individual components. All the components are dosed while the mixer is running.
• recyclate made from inert construction and demolition waste is hygienized, e.g. by water or steam bath or otherwise, thereby reducing the number of (pathogenic) organisms and microorganisms present in it or completely eliminating the presence of these organisms and microorganisms.
• Microsilica and/or substituent(s) thereof which serves as a binder in the conventional production of conventional concretes from natural aggregates, serves as a filler in the preparation of concrete according to the invention, provided that the below-described dosing method and the above-described mixing method is observed, filling the overall lattice structure of the concrete, together with the pozzolanic powder produced by rubbing the grains of the recyclate from construction and demolition waste, covering the particles of the recyclate with coating and filling up intensively the pores therein. Thanks to that, there is no clustering of fine particles and the resulting concrete has a lower porosity and after hardening achieves mechanical and physical parameters comparable to conventional concretes.
• compacted microsilica having a smaller volume is used.
• microsilica may be replaced by at least one microsilica substituent, such as metakaolin or shale with a silica content of at least 45 %.
• a mixture of microsilica and substituent(s) thereof containing 30 % to 70 % by weight of microsilica is used.
• microsilica and/or substituent(s) thereof is added to the mixer only after the last part of the aggregate.
• FIG. 1 which shows a SEM image of a grain of the recyclate from inert construction and demolition waste with microparticles of microsilica deposited on its surface and in its pores at a magnification of 1000 times
• Fig. 2 which shows a SEM image of the surface of the recyclate grain with the emerging transit zone, where it is possible to see also the resulting Ca(OFI) - portlandite, produced by the reaction of CaO contained in the aggregate and free water, at a magnification of 10,000 times
• Fig. 3 shows a SEM image of the surface of the recyclate grain of Fig. 2 at 20,000 times magnification.
• Part of the dose of cement may be replaced with a substituent of cement, e.g., with ground-granulated blast-furnace slag - GGBS or GGBFS and/or with fly ash, ground-calcium carbonate - GCC, stone powder (dust from aggregate mining and processing), or, optionally, with a mixture of at least two such substituents, whereby the ratio of cement to substituents of cement in the fresh concrete is from 30:70 to 70:30.
• This means that the total amount of cement and substituents of cement is the same as the amount of the cement alone, i.e. 135 to 400 kg/m 3 of fresh concrete, or up to 600 kg/m 3 of fresh concrete.
• cement and the substituent(s) of cement are added to the mixture at the same time, separately, or successively in any order (adding substituent(s) of cement first and then cement is preferred, but is not necessary), or in the form of a pre- formed mixture of the above-described composition.
• this mixture After the preparation of the dry mixture from the above-mentioned components and after thorough mixing, this mixture is sprinkled with mixing water in a mixer under constant mixing, or the mixing water is sprayed on it.
• this method of dosing the mixing water the surface of the cement is gradually moistured and the cementing paste being formed gradually adheres to the grains of the recyclate already coated with a mixture of microsilica and pozzolanic powder, which prevents the agglomeration of fresh concrete particles, separation of the fine particles of the mixture as well as separation of water and ensures the required consistency of the fresh concrete.
• this dosing method activates the silica present in the microsilica and/or substituent(s) thereof and in pozzolanic powder and thereby latent hydraulicity of these components, which allows the concretes prepared by this method to achieve physical and mechanical parameters comparable to conventional concretes, this being achieved even at a dose of cement which may be lower than that for conventional concretes. Due to the unexpectedly large amount of pozzolanic powder, it is possible to shorten the mixing times compared to other processes and significantly reduce the required amount of microsilica and/or substituent(s) thereof.
• the mixing water quality must correspond to the drinking water. If required, it may contain at least one known standard additive (dissolved or undissolved) for concrete.
• the friction of the aggregate grains intensively rubs the grains of the recyclate from the inert construction and demolition waste and consequently increases the specific surface area of the recyclate and creates a fine pozzolanic powder, whereby the microsilica and/or substituent(s) thereof, together with the pozzolanic powder, coat/coats the aggregate particles and fill the pores in them.
• 135 to 400 kg of cement are added to the mixture thus obtained, under constant mixing within 1 to 20 seconds, preferably within 1 to 9.9 seconds, or cement and at least one substituent thereof in a total amount of 135 to 600 kg is added to it sequentially in any order or at the same time, under constant mixing within 1 to 20 seconds, and the mixture thus formed is mixed for a further 5 to 39.9 seconds, whereupon the mixture is sprinkled with 50 to 300 kg of mixing water under constant mixing within 5 to 39.9 seconds, or this amount of mixing water is sprayed onto it within 5 to 39.9 seconds, whereby the surface of the cement and, optionally, of its substituent(s) is gradually moistened and the paste formed gradually adheres onto the particles of the aggregate already coated with a mixture of microsilica and/or substituent(s) thereof and pozzolanic powder, and after a further 5 to 160 seconds of mixing, fresh concrete is prepared.
• Fig. 1 is a SEM image of a grain of recyclate made from inert construction and demolition waste in the structure of fresh concrete produced by the method according to the invention at a magnification of 1 ,000 times
• Fig. 2 is a SEM image of a grain of recyclate made from inert construction and demolition waste in the structure of fresh concrete produced by the method according to the invention at a magnification of 10,000 times
• Fig. 3 is a SEM image of the grain of recyclate made from inert construction and demolition waste in the structure of fresh concrete produced by the method according to the invention at a magnification of 20,000 times.
• examples 1 and 2 Exemplary variants of the preparation of fresh concrete according to the invention are described below, the first of which for the case when 100 % by weight of the aggregate is formed by one type of recyclate made from inert construction and demolition waste (examples 1 and 2), the second variant for the case when the aggregate is formed by recyclate from inert construction and demolition waste in combination with concrete recyclate or with natural aggregate (up to 40 % by weight of the total aggregate) (examples 3 and 4), the third variant for the case when 100 % by weight of the aggregate is formed by a combination of two types of recyclate from inert construction and demolition waste (examples 5 and 6), the fourth variant for the case when the aggregate is formed by a combination of three types of recyclate from inert construction and demolition waste or by a combination of two types of recyclate from inert construction and demolition waste and natural aggregate (up to 40 % by weight of the total aggregate) (examples 7 and 8), the fifth variant for the case
• the intervals or, more specifically, the periods of time during which individual components are added, as well as the amounts of these components, are determined by the technological requirements for hardened concrete and its mechanical and physical parameters and may vary within the whole intervals stated below.
• the upper fraction of the recyclate(s) and/or of the natural aggregate in other examples may be higher or lower than 20 mm.
• brick, ceramic, concrete or mixed recyclate made from inert construction and demolition waste with an upper fraction of 20 mm e.g. one-fractional recyclate with a fraction of 0 to 20 mm, two-fractional recyclate with fractions of 0 to 8 mm and 8 to 20 mm, or three-fractional recyclate with fractions of 0 to 4 mm, 4 to 8 mm and 8 to 20 mm
• an industrial mixer for 5 to 39.9 seconds (preferably for 5 to 19.9 seconds).
• the whole dose of microsilica and/or substituent(s) thereof is added to it under constant mixing within 1 to 15 seconds, preferably within 1 to 9.9 seconds, and the mixture thus prepared is mixed for a further 5 to 39.9 seconds.
• the whole dose of cement or the whole dose of cement and substituent(s) thereof is added to the mixture under constant mixing within 1 to 20 seconds, preferably within 1 to 9.9 seconds, and the mixture thus prepared is mixed for a further 5 to 39.9 seconds.
• this mixture is sprinkled with the whole dose of mixing water (which, if appropriate, contains at least one additive for concrete) under constant mixing within 5 to 39,9 seconds or the whole dose of mixing water (which, if appropriate, contains at least one additive for concrete) is sprayed on it within 5 to 39,9 seconds.
• mixing water which, if appropriate, contains at least one additive for concrete
• fresh concrete is prepared, in which 100 % by weight of the aggregate is composed of recyclate from inert construction and demolition waste.
• the fresh concretes thus prepared were subjected to consistency tests by a method according to EN 12350-2 and air content was measured by a method according to EN 12350-7.
• test bodies were removed from the molds on the following day and stored for the appropriate tests in an air-conditioned chamber at a temperature of 20 ⁇ 2 ° C and a relative humidity above 95 %. Parameters measured during these tests are summarized in Table 2.
• chloride content in this concrete was determined by calculation according to EN 196-2 and EN 1744-1 , the content of natural radionuclides and mass activity index were determined according to the procedure of Regulation No. 307/2002 Coll of the State Office for Nuclear Safety on radiation protection, as amended, whereby both these parameters meet the requirements of this Regulation for use for buildings with residential rooms or spaces (mass activity 226 Ra ⁇ 150 Bq.kg 1 , mass activity index I ⁇ 0.5).
• mass activity index I ⁇ 0.5 mass activity index
• Table 4 shows the strength classes of concrete to which the respective concretes belong due to their mechanical-physical parameters and the classification classes of specification of use of these concretes according to CSN (Czech Technical Standard) EN 206 (see Table 5).
• brick, ceramic or mixed recyclate from inert construction and demolition waste with an upper fraction of 20 mm e.g. one-fractional recyclate with a fraction of 0 to 20 mm, two-fractional recyclate with fractions of 0 to 8 mm and 8 to 20 mm, or three-fractional recyclate with fractions of 0 to 4 mm, 4 to 8 mm and 8 to 20 mm
• an industrial mixer for 5 to 39.9 seconds (preferably for 5 to 19.9 seconds).
• concrete recyclate with an upper fraction of 20 mm e.g., one- fractional concrete recyclate with a fraction of 0 to 20 mm, two-fractional concrete recyclate with fractions of 0 to 8 mm and 8 to 20 mm, or three- fractional concrete recyclate with fractions of 0 to 4 mm, 4 to 8 mm and 8 to 20 mm
• natural aggregate with an upper fraction of 20 mm, preferably 8 mm, or fine aggregate with an upper fraction of 4 mm (up to 40 % by weight of the total aggregate in the concrete) is added to it under constant mixing and the mixture thus obtained is mixed for a further 5 to 39.9 seconds.
• the whole dose of microsilica and/or substituent(s) thereof is added to it under constant mixing within 1 to 15 seconds, preferably within 1 to 9.9 seconds, and the mixture thus prepared is mixed for an additional 5 to 39.9 seconds.
• the whole dose of cement or the whole dose of cement and substituent(s) thereof is added to it under constant mixing within 1 to 20 seconds, preferably within 1 to 9.9 seconds, and the mixture thus prepared is mixed for a further 5 to 39.9 seconds.
• this mixture is sprinkled with the whole dose of mixing water (which, if necessary, contains at least one additive for concrete) under constant mixing within 5 to 39.9 seconds or the whole dose of the mixing water (which, if necessary, contains at least one additive for concrete) is sprayed on it within 5 to 39.9 seconds.
• fresh concrete is prepared, in which 60 to 100 % by weight of the aggregate is composed of recyclate from inert construction and demolition waste.
• chloride content in this concrete was determined by calculation according to EN 196-2 and EN 1744-1 , the content of natural radionuclides and mass activity index were determined following the procedure of Decree No. 307/2002 Coll on radiation protection of the State Office for Nuclear Safety, as amended, whereby all these parameters meet the requirements of this Decree for use in buildings with residential rooms or spaces (mass activity 226 Ra ⁇ 150 Bq.kg 1 , mass activity index I ⁇ 0.5).
• mass activity index I ⁇ 0.5 mass activity index
• Table 8 shows strength classes of concrete to which the respective concretes belong due to their mechanical-physical parameters and the classification classes of specification of the use of these concretes according to CSN (Czech Technical Standard) EN 206 (see Table 5).
• recyclate made from inert construction and demolition waste with an upper fraction of 20 mm e.g. one-fractional recyclate with a fraction of 0 to 20 mm, two-fractional recyclate with fractions of 0 to 8 mm and 8 to 20 mm, or three-fractional recyclate with fractions of 0 to 4 mm, 4 to 8 mm and 8 to 20 mm
• the first type brick, ceramic or mixed recyclate, alternatively concrete recyclate
• recyclate from inert construction and demolition waste with an upper fraction of 20 mm e.g.
• one-fractional recyclate with a fraction of 0 to 20 mm, two-fractional recyclate with fractions of 0 to 8 mm and 8 to 20 mm, or three-fractional recyclate with fractions of 0 to 4 mm, 4 to 8 mm and 8 to 20 mm) of the second type (brick, ceramic or mixed recyclate, optionally concrete recyclate) is added under constant mixing, whereby the recyclate being added is made from inert construction and demolition waste of a different type than the recyclate to which it is added, and the mixture thus prepared is mixed for a further 5 to 39.9 seconds.
• the whole dose of microsilica and/or substituent(s) thereof is added to it under constant mixing within 1 to 15 seconds, preferably within 1 to 9.9 seconds and the mixture thus prepared is mixed for a further 5 to 39.9 seconds.
• the whole dose of cement or the whole dose of cement and substituent(s) thereof is added to it under constant mixing within 1 to 20 seconds, preferably within 1 to 9.9 seconds, and the mixture thus prepared is mixed for a further 5 to 39.9 seconds.
• this mixture is sprinkled with the whole dose of mixing water (which, if necessary, contains at least one additive for concrete) under constant mixing within 5 to 39.9 seconds or the whole dose of mixing water (which, if necessary, contains at least one additive for concrete) is sprayed on it within 5 to 39.9 seconds.
• fresh concrete is prepared, in which 100 % by weight of the aggregate is composed of recyclate from inert construction and demolition waste.
• chloride content in this concrete was determined by calculation according to EN 196-2 and EN 1744-1 , the content of natural radionuclides and mass activity index were determined following the procedure of Decree No. 307/2002 Coll on radiation protection of the State Office for Nuclear Safety, as amended, whereby all these parameters meet the requirements of this Decree for use in buildings with residential rooms or spaces (mass activity 226 Ra ⁇ 150 Bq.kg 1 , mass activity index I ⁇ 0.5). According to the procedure in EN 12457 and Decree of the Ministry of Environment No. 294/2005 Coll its ecotoxicity was found to be complying with the requirements. The criteria for determination of ecotoxicity are shown in Table 3, example 2.
• Table 1 1 shows the strength classes of concretes into which the respective concrete belongs due to its mechanical-physical parameters and classification classes of specification of the use of these concrete according to CSN EN 206 (see Table 5).
• recyclate made from inert construction and demolition waste having an upper fraction of 20 mm e.g. one-fractional recyclate with a fraction of 0 to 20 mm, two-fractional recyclate with fractions of 0 to 8 mm and 8 to 20 mm, or three-fractional recyclate with fractions of 0 to 4 mm, 4 to 8 mm and 8 to 20 mm
• the first type brick, ceramic or mixed recyclate, optionally concrete recyclate
• recyclate from inert construction and demolition waste with an upper fraction of 20 mm e.g.
• one-fractional recyclate with a fraction of 0 to 20 mm, two-fractional recyclate with fractions of 0 to 8 mm and 8 to 20 mm, or three-fractional recyclate with fractions of 0 to 4 mm, 4 to 8 mm and 8 to 20 mm) of the second type (brick, ceramic or mixed recyclate, optionally concrete recyclate) is added to it under constant mixing, whereby the recyclate being added is made from inert construction and demolition waste of a different type than the recyclate to which it is added, and the mixture thus prepared is mixed for a further 5 to 39.9 seconds.
• recyclate from inert construction and demolition waste with an upper fraction of 20 mm e.g.
• the whole dose of microsilica and/or its substituent(s) is added to it under constant mixing within 1 to 15 seconds, preferably within 1 to 9.9 seconds and the mixture thus prepared is mixed for a further 5 to 39.9 seconds.
• the whole dose of cement or the whole dose of cement and substituent(s) thereof is added to it under constant mixing within 1 to 20 seconds, preferably within 1 to 9.9 seconds, and the mixture thus prepared is mixed for a further 5 to 39.9 seconds.
• this mixture is sprinkled with the whole dose of mixing water (which, if necessary, contains at least one additive for concrete) under constant mixing within 5 to 39.9 seconds or the whole dose of the mixing water (which, if necessary contains at least one additive for concrete) is sprayed on it within 5 to 39.9 seconds.
• fresh concrete is prepared, in which at least 60 % by weight of the aggregate consists of recyclate from inert construction and demolition waste.
• chloride content in this concrete was determined by calculation according to EN 196-2 and EN 1744-1 , the content of natural radionuclides and mass activity index were determined following the procedure of Decree No. 307/2002 Coll on radiation protection of the State Office for Nuclear Safety, as amended, whereby all these parameters meet the requirements of this Decree for use in buildings with residential rooms or spaces (mass activity 226 Ra ⁇ 150 Bq.kg 1 , mass activity index I ⁇ 0.5). According to the procedure in EN 12457 and Decree of the Ministry of Environment No. 294/2005 Coll its ecotoxicity was found to be complying with the requirements. The criteria for determination of ecotoxicity are shown in Table 3, example 2.
• Table 14 shows the strength classes of concrete to which the respective concrete belongs due to its mechanical-physical parameters and classification classes of specification of the use of these concrete according to CSN (Czech Technical Standard) EN 206 (see Table 5).
• concrete recyclate having an upper fraction of 20 mm (e.g. one-fractional recyclate with a fraction of 0 to 20 mm, two-fractional recyclate with fractions of 0 to 8 mm and 8 to 20 mm, or three-fractional recyclate with fractions of 0 to 4 mm, 4 to 8 mm and 8 to 20 mm) is mixed in an industrial mixer for 5 to 39.9 seconds (preferably for 5 to 19.9 seconds).
• natural aggregate with an upper fraction of 20 mm up to 40 % by weight of the total aggregate in concrete
• the mixture thus obtained is mixed for a further 5 to 39.9 seconds (preferably for 5 to 19.9 seconds).
• the whole dose of microsilica and/or of substituent(s) thereof is added to it under constant mixing within 1 to 15 seconds, preferably within 1 to 9.9 seconds, and the mixture thus obtained is mixed for a further 5 to 39.9 seconds.
• the whole dose of cement or the whole dose of cement and substituent(s) thereof is added to it under constant mixing within 1 to 20 seconds, preferably within 1 to 9.9 seconds, and the mixture thus prepared is mixed for a further 5 to 39.9 seconds.
• this mixture is sprinkled with the whole dose of mixing water (which, if necessary contains at least one additive for concrete) under constant mixing for 5 to 39.9 seconds or the whole dose of the mixing water (which, if necessary contains at least one additive for concrete) is sprayed on it within 5 to 39.9 seconds.
• fresh concrete is prepared, in which at least 60 % by weight of the aggregate is composed of recyclate from inert construction and demolition waste.
• chloride content in this concrete was determined by calculation according to EN 196-2 and EN 1744-1 , the content of natural radionuclides and mass activity index were determined following the procedure of Decree No. 307/2002 Coll on radiation protection of the State Office for Nuclear Safety, as amended, whereby all these parameters meet the requirements of this Decree for use in buildings with residential rooms or spaces (mass activity 226 Ra ⁇ 150 Bq.kg 1 , mass activity index I ⁇ 0.5). According to the procedure in EN 12457 and Decree of the Ministry of Environment No. 294/2005 Coll its ecotoxicity was found to be complying with the requirements. The criteria for determination of ecotoxicity are summarized in Table 3, example 2.
• Table 17 shows the strength classes of concrete to which the respective concrete belongs due to its mechanical-physical parameters and classification classes of specification of the use of these concretes according to CSN (Czech Technical Standard) EN 206 (see Table 5).
• brick or ceramic or mixed recyclate from inert construction and demolition waste with concrete recyclate and with up to 40 % by weight of natural aggregate.
• a brick or ceramic or mixed recyclate from inert construction and demolition waste is added to the mixer first, afterwards it is followed by concrete recyclate and then by natural aggregate.
• Brick, ceramic or mixed recyclate from inert construction and demolition waste have similar characteristics and behavior and can therefore be interchanged or mixed.
• the whole dose of microsilica and/or substituent(s) thereof, as well as the whole dose of the aggregate may be divided into two or more smaller portions (equal or different), whereby the individual portions of the dose of microsilica and/or substituent(s) thereof are added one by one after the addition of the individual portions of the whole dose of the aggregate, or recyclate from inert construction and demolition waste of different types or and/or fractions, or at least some parts of the dose of microsilica and/or substituent(s) thereof may be added simultaneously with some parts of the whole dose of the aggregate or recyclate - see examples 11 and 12 below.
• the first part of the whole dose of aggregate composed of recyclate made from inert construction and demolition waste is mixed in an industrial mixer for 5 to 39.9 seconds (preferably for 5 to 19.9 seconds), whereupon the first part of the whole dose of microsilica and/or of substituent(s) thereof is added to it within 1 to 15 seconds, preferably within 1 to 9.9 seconds, and the mixture thus obtained is mixed for 5 to 39.9 seconds (preferably for 5 to 19.9 seconds).
• the remaining part of the aggregate consisting of recyclate from inert construction and demolition waste or natural aggregate is added to it under constant mixing and the mixture thus obtained is mixed for 5 to 39.9 seconds (preferably for 5 to
• the second part of the dose of microsilica and/or of substituent(s) thereof is added to it within 1 to 15 seconds, preferably within 1 to
• the whole dose of the aggregate is 1000 to 2300 kg/m 3 of fresh concrete and the whole dose of microsilica and/or of substituent(s) thereof is 10 to 27.9 kg/m 3 of fresh concrete.
• the mixture thus obtained is mixed for a further 5 to 39.9 seconds.
• the whole dose of cement or of cement and substituent(s) thereof is added to it under constant mixing within 1 to 20 seconds, preferably within 1 to 9.9 seconds, and the mixture thus prepared is mixed for another 5 to 39.9 seconds.
• the mixture is sprinkled with the whole dose of mixing water (which, if necessary, contains at least one addition for concrete) under constant mixing within 5 to 39.9 seconds or the whole dose of the mixing water (which, if necessary, contains at least one addition for concrete) is sprayed on it within 5 to 39.9 seconds.
• fresh concrete is prepared, in which 100 % by weight of the aggregate is composed of recyclate made from inert construction and demolition waste.
• Both parts of the whole dose of the aggregate may consist of the same type of recyclate made from inert construction and demolition waste or may differ in fraction and/or the type of recyclate.
• the first part of the whole dose of the aggregate composed of recyclate made from inert construction and demolition waste is mixed in an industrial mixer for 5 to 39.9 seconds (preferably for 5 to 19.9 seconds). Thereafter, the first part of the whole dose of microsilica and/or of substituent(s) thereof is added to it within 1 to 15 seconds, preferably within 1 to 9.9 seconds, and the mixture thus obtained is mixed for 5 to 39.9 seconds (preferably for 5 to 19.9 seconds).
• the second part of the whole dose of the aggregate composed of recyclate from inert construction and demolition waste or natural aggregate is added to it under constant mixing and the mixture thus obtained is mixed for 5 to 39.9 seconds (preferably for 5 to 19.9 seconds), whereupon the second part of the dose of microsilica and/or of substituent(s) thereof is added to it within 1 to 15 seconds, preferably 1 to 9.9 seconds, and the mixture thus obtained is mixed for 5 to 39.9 seconds (preferably for 5 to 19.9 seconds).
• the third part of the aggregate composed of recyclate from inert construction and demolition waste or natural aggregate is added to it under constant mixing and the mixture thus obtained is mixed for 5 to 39.9 seconds (preferably for 5 to 19.9 seconds) and then the third part of the dose of microsilica and/or substituent(s) thereof is added to it within 1 to 15 seconds, preferably within 1 to 9.9 seconds, and the mixture thus obtained is mixed for 5 to 39.9 seconds (preferably for 5 to 19.9 seconds).
• the whole dose of the aggregate is 1000 to 2300 kg/m 3 of fresh concrete and the whole dose of microsilica and/or substituent(s) thereof is 10 to 27.9 kg/m 3 of fresh concrete.
• the mixture thus obtained is further mixed for 5 to 39.9 seconds.
• the whole dose of cement or cement and substituent(s) thereof is added to it under constant mixing within 1 to 20 seconds, preferably within 1 to 9.9 seconds, and the mixture thus prepared is mixed for a further 5 to 39.9 seconds. Subsequently, this mixture is sprinkled with the whole dose of mixing water (which, if necessary, contains at least one additive for concrete ) under constant mixing wihin 5 to 39.9 seconds or the whole dose of the mixing water (which, if necessary, contains at least one additive for concrete,) is sprayed on it within 5 to 39.9 seconds. After another 5 to 160 seconds of mixing, fresh concrete is prepared, in which at least 100 % by weight of the aggregate is composed of recyclate from inert construction and demolition waste.
• Different parts of the whole dose of the aggregate may consist of the same type of recyclate from inert construction and demolition waste or may differ from each other in fraction and/or the type of recyclate.
• reinforcement fibers of at least one type which reinforce the structure of the concrete and thereby improve some of its properties, e.g. tensile strength and flexural strength.
• Suitable reinforcing fibers are, 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 preferably added to the concrete mixture after the addition of microsilica and/or substituent(s) thereof and after thorough mixing of the mixture obtained.
• the total amount of all reinforcing fibers is 0.6 to 1.2 kg/m 3 of fresh concrete, in the case of steel and similar fibers the total amount is up to 25 kg/m 3 of fresh concrete.
• the reinforcing fibers are added to the concrete mixture under constant mixing within 5 to 30 seconds, which ensures their uniform distribution in the concrete.
• fresh concrete with a finer texture is prepared using the same processes, sometimes referred to as cement mortar or concrete mortar.
• the 0 to 20 mm aggregate fraction described in the above examples is not limiting for the implementation of the invention, since both natural aggregate and recyclate from inert construction and demolition waste may have a higher limit of the upper fraction.
• All the concretes according to the invention are designed for both manual and machine processing (including shotcrete) and are suitable for conventional concrete structures from both plain concrete and ferroconcrete.
• fresh concrete transport concrete
• these concretes can be also used for the production of concrete products and prefabricated elements, e.g., concrete blocks and bricks, paving cobbles, slabs, blocks, curbs, various elements of garden architecture, ceiling beams and inserts, etc.

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