DRY MIXTURE FOR THE PREPARATION OF CONCRETE, FRESH CONCRETE AND METHOD FOR THE PREPARATION OF FRESH CONCRETE

Abstract

Fresh concrete which contains in 1 m3 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 150 kg of finely ground brick, ceramic, mixed or concrete recyclate having a particle size of 5 to 250 microns and a specific surface of 300 to 1500 m2/kg or 10 to 150 kg of a mixture of finely ground brick, ceramic, mixed or concrete recyclate having a particle size of 5 to 250 microns and a specific surface of 300 to 1500 m2/kg and microsilica and/or at least one substituent thereof, with a content of finely ground recyclate in this combination of at least 10% by weight, and 1000 to 2300 kg of aggregate.

Claims

1. Fresh concrete, wherein it contains in 1 m3 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 150 kg of finely ground recyclate from inert construction and demolition waste having a particle size of 5 to 250 μm and a specific surface of 300 to 1500 m2/kg or 10 to 150 kg of a mixture of finely ground recyclate from inert construction and demolition waste having a particle size of 5 to 250 μm and a specific surface of 300 to 1500 m2/kg in combination with microsilica and/or at least one substituent thereof with a content of finely ground recyclate in this combination of at least 10% by weight, and 1000 to 2300 kg of aggregate, whereby 45 to 100% of the aggregate is formed by recyclate from inert construction and demolition waste, 0 to 40% of aggregate is formed by natural aggregate and 0 to 40% of aggregate consists of lightweight artificial aggregate and/or cinder and/or scoria and/or polystyrene and/or at least one organic filler and/or another component for improving thermal and/or acoustic and/or fire resistance properties of hardened concrete, whereby the aggregate grains are coated and their pores are filled with finely ground recyclate from inert construction and demolition waste or with a mixture of finely ground recyclate from inert construction and demolition waste and microsilica and/or at least one substituent thereof, and cement paste formed by the moistening of cement or substituent(s) thereof is adhered to the aggregate particles thus treated.

2. The fresh concrete according to claim 1, wherein in that it further contains 10 to 290 kg of finely ground recyclate from inert construction and demolition waste having a particle size of s 5 to 250 μm and having a specific surface of 300 to 1500 m2/kg, which is incorporated in cement paste formed by moistening cement or substituent(s) thereof.

3. The fresh concrete according to claim 1, wherein 60 to 100% of aggregate consists of recyclate from inert construction and demolition waste.

4. The fresh concrete according to claim 1, wherein it further contains at least one additive for concrete, whereby the total amount of all the additives for concrete added is up to do 10% by weight of the dose of cement or of the dose of cement and substituent(s) thereof.

5. The fresh concrete according to claim 1, wherein it further contains reinforcing fibers in an amount of 0.6 to 25 kg/m3 of fresh concrete.

6. The fresh concrete according to claim 1, wherein the substituent of cement is finely ground recyclate from inert construction and demolition waste having a particle size of 5 to 250 μm and a specific surface of 300 to 1500 m2/kg in a dose of 10 to 150 kg/m3 of fresh concrete.

7. The Fresh concrete according to claim 1, characterized in that the finely ground recyclate from inert construction and demolition waste has a particle size of 5 to 125 μm.

8. A dry mixture for the preparation of fresh concrete according to claim 1, wherein it contains when computed for 1 m3 of fresh concrete 10 to 150 kg of finely ground recyclate from inert construction and demolition waste having a particle size of 5 to 250 μm and a specific surface of 300 to 1500 m2/kg, or finely ground recyclate in combination with microsilica and/or at least one substituent thereof, with a content of the finely ground recyclate in this combination of at least 10% by weight, and 1000 to 2300 kg of aggregate, 45 to 100% by weight of the aggregate being composed of recyclate from inert construction and demolition waste, whereby the aggregate grains are coated and their pores are filled with the finely ground recyclate from inert construction and demolition waste or with the mixture of the finely ground recyclate from inert construction and demolition waste and the microsilica and/or at least one substituent thereof.

9. The dry mixture according to claim 8, wherein it further contains 135 to 400 kg of cement, or cement and at least one substituent thereof in a total amount of 135 to 600 kg, whereby the ratio of cement to the substituent(s) of cement ranges from 30:70 to 70:30.

10. The dry mixture according to claim 8, wherein the particles of the finely ground recyclate from inert construction and demolition waste have a size of 5 to 125 μm.

11. A method for the preparation of 1 m3 of fresh concrete using recyclate from inert construction and demolition waste, wherein 1000 to 2300 kg of aggregate, in which 45% by weight to 100% by weight consists of recyclate from inert construction and demolition waste, is mixed in a mixer with 10 to 150 kg of finely ground recyclate from inert construction and demolition waste having a particle size of 5 to 250 μm and a specific surface of 300 to 1500 m2/kg or with 10 to 150 kg of a mixture of finely ground recyclate from inert construction and demolition waste having a particle size of 5 to 250 μm and a specific surface of 300 to 1500 m2/kg and of microsilica and/or of at least one substituent thereof, with a content of finely ground recyclate in this combination of at least 10% by weight, whereby the finely ground recyclate from inert construction and demolition waste, optionally in combination with microsilica and/or at least one substituent thereof, coats the aggregate particles and fills the pores in them, and after thorough mixing, 135 to 400 kg of cement is added to the mixture thus obtained under constant mixing, or cement and at least one substituent thereof in a total amount of 135 to 600 kg are added to it either one by one in any order or simultaneously under constant mixing, and after mixing the mixture thus obtained, this mixture is sprinkled with 50 to 300 kg of mixing water under constant mixing, or it is sprayed with this amount of the mixing water, whereby the surface of cement or the surface of the substituent(s) thereof is gradually moistened and the (cement) paste thus formed gradually adheres to the grains of the recyclate already coated with the finely ground recyclate from inert construction and demolition waste or with this recyclate in combination with microsilica and/or at least one substituent thereof, and after further mixing of this mixture, fresh concrete is prepared.

12. The method according to claim 11, wherein 1000 to 2300 kg of aggregate, in which 45% by weight to 100% by weight is formed by recyclate from inert construction and demolition waste is mixed in a mixer for 5 to 40 seconds with 10 to 150 kg of finely ground recyclate from inert construction and demolition waste having a particle size of 5 to 250 μm and a specific surface of 300 to 1500 m2/kg or with 10 to 150 kg of a mixture of finely ground recyclate from inert construction and demolition waste having a particle size of 5 to 250 μm and a specific surface of 300 to 1500 m2/kg and microsilica and/or at least one substituent thereof, with a content of finely ground recyclate of at least 10% by weight in this combination, whereby the finely ground recyclate from inert construction and demolition waste, optionally in combination with microsilica and/or at least one substituent thereof, coats the aggregate grains and fills the pores in them, whereby after thorough mixing, 135 to 400 kg of cement is added to the mixture thus obtained under constant mixing within 1 to 20 seconds, or cement and at least one substituent thereof in a total amount of 135 to 600 kg is added to it under constant mixing within 1 to 20 seconds either one by one in any order or simultaneously, and the mixture thus obtained is mixed for a further 5 to 80 seconds, whereupon the mixture is sprinkled with 50 to 300 kg of mixing water under constant mixing within 5 to 60 seconds, or this amount of the mixing water is sprayed onto it within 5 to 60 seconds, whereby the surface of cement or the surface of substituent(s) thereof is gradually moistened and the (cement) paste thus formed gradually adheres to the grains of the recyclate already coated with the finely ground recyclate from inert construction and demolition waste, optionally in combination with microsilica and/or at least one substituent thereof, and after another 5 to 160 seconds of mixing, fresh concrete is prepared.

13. The method according to claim 11, wherein at first, aggregate is mixed in a mixer and after thorough mixing, finely ground recyclate from inert construction and demolition waste having a particle size of 5 to 250 μm and a specific surface of 300 to 1500 m2/kg is added to it under constant mixing, or finely ground recyclate from inert construction and demolition waste having a particle size of 5 to 250 μm and a specific surface of 300 to 1500 m2/kg and microsilica and/or at least one substituent thereof are added to it either one by one in any order or simultaneously, whereby the content of the finely ground recyclate in this combination is at least 10% by weight, and the mixture thus obtained is mixed.

14. The method according to claim 11, wherein at first, aggregate is mixed in a mixer for 5 to 40 seconds and after thorough mixing, finely ground recyclate from inert construction and demolition waste having a particle size of 5 to 250 μm and a specific surface of 300 to 1500 m2/kg is added to it under constant mixing within 1 to 15 seconds, or finely ground recyclate from inert construction and demolition waste having a particle size of 5 to 250 μm and a specific surface of 300 to 1500 m2/kg and microsilica and/or at least one substituent thereof are added to it either one by one in any order or simultaneously, whereby the content of the finely ground recyclate in this combination is at least 10% by weight, and the mixture thus obtained is mixed for a further 5 to 80 seconds.

15. The method according to claim 11, wherein the finely ground brick recyclate is brick dust from brick grinding or from brick kilns having a particle size of 5 to 250 μm and a specific surface of 300 to 1500 m2/kg.

16. The method according to claim 11, wherein a substituent of microsilica is metakaolin or shale with a content of silicon dioxide of at least 45% by weight.

17. The method according to claim 11, wherein up to 40% by weight of the total aggregate is composed of natural aggregate.

18. The method according to claim 11, wherein up to 40% by weight of the total aggregate is composed of lightweight artificial aggregate and/or cinder and/or scoria and/or polystyrene and/or at least one organic filler and/or another component for improving thermal and/or acoustic and/or fire resistance properties of hardened concrete.

19. The method according to claim 11, wherein at least one additive for concrete is added to the mixture being prepared together with mixing water or after the mixing water, whereby the total amount of all the additives for concrete added is up to 10% by weight of the dose of cement or the dose of cement and substituent(s) thereof.

20. The method according to claim 11, wherein after the addition of finely ground recyclate from inert construction and demolition waste or of finely ground recyclate from inert construction and demolition waste in combination with microsilica and/or at least one substituent thereof, and after mixing the mixture thus obtained, reinforcing fibers of at least one type are added to it under constant mixing, whereby the total amount of all reinforcing fibers ranges from 0.6 to 25 kg/m3 of fresh concrete.

21. The method according to claim 11, wherein the substituent of cement is finely ground recyclate from inert construction and demolition waste having a particle size of 5 to 250 μm and a specific surface of 300 to 1500 m2/kg in a dose of 10 to 150 kg/m3 of fresh concrete, which is during mixing incorporated into cement paste formed by moistening cement or substituent(s) thereof.

22. The method according to claim 11, wherein the recyclate from inert construction and demolition waste has a particle size of 5 to 125 μm.

Description

EXAMPLES OF EMBODIMENT

[0040] Examples of the preparation of fresh concrete according to the invention are described below for illustration.

Example 1

[0041] For the preparation of concrete according to the invention, brick, ceramic, concrete or mixed recyclate from mixed inert construction and demolition waste with an upper fraction of 20 mm is mixed in an industrial mixer with forced circulation for 5 to 40 seconds, preferably for 5 to 20 seconds. After thorough mixing, finely ground brick, ceramic, mixed or concrete recyclate having a particle size of 5 to 250 μm, preferably 5 to 125 μm, and having a specific surface of 300 to 1500 m.sup.2/kg is added to it under constant mixing within 1 to 15 seconds, preferably within 1 to 10 seconds, or finely ground brick, ceramic, mixed or concrete recyclate and microsilica and/or at least one substituent thereof are added either one by one in any order or simultaneously, and the mixture thus obtained is mixed for a further 5 to 80 seconds, preferably for 5 to 40 seconds. Thereafter, cement is added to it under constant mixing within 1 to 20 seconds, preferably within 1 to 10 seconds, or cement and at least one substituent thereof is added to it either one by one in any order or simultaneously within 1 to 15 seconds, preferably within 1 to 10 seconds, and the mixture thus obtained is mixed for a further 5 to 80 seconds, preferably for 5 to 40 seconds. As a substituent of cement, another dose of finely ground recyclate from inert construction and demolition waste can be used, preferably concrete recyclate having a particle size of 5 to 250 μm, preferably 5 to 125 μm and having a specific surface of 300 to 1500 m.sup.2/kg. Subsequently, this mixture is sprinkled with the entire dose of mixing water (which, if necessary, contains at least one additive for concrete) within 5 to 60 seconds, preferably within 5 to 40 seconds, under constant mixing, or it is sprayed with the entire dose of the mixing water within 5 to 60 seconds, preferably within 5 to 40 seconds. After another 5 to 160 seconds, preferably 5 to 80 seconds, of mixing, fresh concrete is prepared, in which 100% by weight of aggregate is composed of recyclate from inert construction and demolition waste.

[0042] 10 samples of fresh concrete according to the invention were prepared by this method, whereby the composition of 1 m.sup.3 of each of them is described in Table 2.

[0043] The fresh concretes thus prepared were subjected to consistency tests according to EN 12350-2 and air content was measured according to EN 12350-7.

[0044] From these fresh concretes, 150 mm cubes were created for the compressive strength test according to EN 12390-3, 100 mm×100 mm×400 mm prisms were formed for testing flexural strength according to EN 12390-5, for the measurement of volume changes according to CSN (Czech Technical Standard) 73 1320, for the measurement of static modulus of elasticity according to ISO 1920-10 and 200 mm×200 mm×50 mm boards were formed for thermal conductivity test. After the hardening of concrete, the test bodies were removed from the molds on the following day and stored for the respective 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 3.

TABLE-US-00002 TABLE 2 Sample Component ERC 1/1 ERC 1/2 ERC 1/3 ERC 1/4 ERC 1/5 ERC 1/6 ERC 1/7 ERC 1/8 ERC 1/9 ERC 1/10 Mixed recyclate 0 0 0 1300   1450 0 0 0 0 0 from mixed inert construction and demolition waste, fraction 0 to 20 mm [kg] Brick recyclate, 0 0 0 0 0 0 0 1420 1200   0 fraction 0 to 20 mm [kg] Ceramic 0 0 0 0 0 0 0 0 0 1160 recyclate, fraction 0 to 20 mm [kg] Concrete 1500 1570 1250 0 0 2255 1670 0 0 0 recyclate, fraction 0 to 20 mm [kg] Microsilica [kg] 5 0 0 10  5 0 0 0 15  20 Finely ground 15 30 50 60  95 10 120 150 35  50 recyclate from inert construction and demolition waste [kg] Cement [kg] 200 230 360 190  210 230 230 180 250  250 Substituent of 150/50 140/100 40/40 140/70 90/10 0 50/20 60/30 100/100 150/150 cement [kg]/ finely ground recyclate from inert construction and demolition waste [kg] Concrete 4.7 2 4.6   5.0 5.0 0 0 5.4   5.2 5.1 plasticizer or superplasticizer [kg] Water [kg] 235 245 195 282  286 215 257 202 265  272 Aerating agent 0 0 0.9 0 0 0 0 0 0 0 for concrete [%] Volume weight 2110 2170 1760 1940   2090 — 2190 1990 1 850    1870 of concrete at age of 7 days [kg/m.sup.3] Volume weight 2100 2150 1750 1 935    2080 — 2195 1990 1845   1862 of concrete at age of 28 days [kg/m.sup.3]

TABLE-US-00003 TABLE 3 Sample Parameter ERC 1/1 ERC 1/2 ERC 1/3 ERC 1/4 ERC 1/5 ERC 1/6 ERC 1/7 ERC 1/8 ERC 1/9 ERC 1/10 Consistency of fresh 200 130 150 170 230 40 80 190 230 220 concrete - slump cone test [mm] Air content in fresh 3.5 3.0 2.9 3.8 3.4 — — 4.0 4.5 4.8 concrete [%] Compressive strength [MPa] After 7 days 24.50 28.0 25.60 18.50 20.80 12.8 17.7 19.4 20.5 22.2 After 14 days 29.40 33.50 31.0 28.70 27.80 17.5 24.9 27.9 27.7 28.7 After 28 days 37.0 42.20 39.10 33.20 34.50 24.6 33.9 35.9 33.2 34.5 Flexural strength 5.50 4.70 5.10 2.60 3.50 2.1 1.9 2.70 3.7 — after 28 days [MPa] Depth of water 22 12 — 20 16 30 — 25 — 28 penetration under pressure [mm]

[0045] In addition, chloride content in these concretes 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 of the State Office for Nuclear Safety No. 307/2002 Coll., as amended, on radiation protection, whereby all these parameters meet the requirements of this Regulation for use for buildings with residential rooms or spaces (mass activity .sup.226Ra≤150 Bq.Math.kg.sup.−1, mass activity index I≤0.5). According to the procedure of EN 12457 and Regulation of the Ministry of the Environment No. 294/2005 Coll. its ecotoxicity was found to be complying with the requirements. The criteria for the determination of ecotoxicity are summarized in Table 4.

TABLE-US-00004 TABLE 4 Exposure time Tested organism [hours] I II Water arthropod 48 Max. Max. Daphnia magna immobilization immobilization 30% 30% Aquatic vertebrate 96 without death without death Poecillia reticulata and behavioral and behavioral change change Alga Desmodesmus 72 Max. inhibition Max. change in subspicatus 30% growth 30% Seeds of the plant 72 Max. inhibition Max. change in Sinapis alba 30% growth 30%

[0046] Table 5 shows strength classes of concrete to which the respective concretes belong due to their physical and mechanical parameters and classification classes of specification regarding use of these concretes according to CSN (Czech Technical Standard) EN 206 (see Table 6).

TABLE-US-00005 TABLE 5 Sample ERC 1/1 ERC 1/2 ERC 1/3 ERC 1/4 ERC 1/5 ERC 1/6 ERC 1/7 ERC 1/8 ERC 1/9 ERC 1/10 Concrete C25/30 C30/37 C25/30 C20/25 C25/30 C16/20 C20/25 C25/30 C20/25 C25/30 strength class Specification X0 XF1 X0 X0 X0 X0 X0 X0 X0 X0 of concrete XC1 XC1 XC1 XC1 XC1 XC1 XC1 XC1 XC1 use XC2 XC2 XC2 XC2 XC2 XC2 XC2 XC2 XC2 XC3 XC3 XC3 XC3 XC3 XC3 XC3 XC3 XC4 XC4 XC4 XC4 XC4 XC4 XC4 XC4 XD1 XD1 XD1 XD1 XD1 XD1 XD1 XD2 XD2 XD2 XD2 XD2 XD2 XD2 XF1 XF1 XF1 XF XF1 XF1 XF2

TABLE-US-00006 TABLE 6 Class Description of degree of Informative examples where designation environmental impact exposure classes may occur for concrete with no risk of corrosion or attack X0 For concrete without re- Concrete inside buildings with inforcement or embedded metal very low humidity inserts. All exposures, except where there is freeze/ thaw, abrasion or aggressive chemical environment For reinforced concrete or concrete with embedded metal inserts: Very dry for concrete with risk of corrosion induced by carbonation XC1 Dry or permanently wet. Concrete inside buildings with very low humidity; Concrete permanently submerged in water. XC2 Wet, rarely dry. Concrete surfaces subject to long-term water contact; Most foundations. XC3 Moderate humidity. Concrete inside buildings with moderate or high air humidity; External concrete sheltered from rain. XC4 Cyclic wet and dry. Concrete surfaces subject to water contact, not within exposure class XC2 for concrete with risk of corrosion induced by chlorides other than from sea water XD1 Moderate humidity. Concrete surfaces exposed to airborne chlorides. XD2 Wet, rarely dry. Swimming pools. Concrete exposed to industrial waters containing chlorides. for concrete exposed to freeze/thaw attack, without chemical de-icing agents XF1 Moderate water saturation, Vertical concrete surfaces without de-icing agents. exposed to rain and freezing XF2 Moderate water saturation, Vertical concrete surfaces of with de-icing agents road structures exposed to frost and de-icing agents dispersed in air Class Description of degree of Informative examples where designation environmental impact exposure classes may occur XF4 High water saturation, with Roads and bridge decks de-icing agents or sea water exposed to de-icing agents, concrete surfaces exposed to direct spray, splashed zone of marine structures exposed to freezing for concrete exposed to the chemical effects of soil and groundwater XA1 Slightly aggressive chemical Concrete exposed to natural environment soils and groundwater

Example 2

[0047] For the preparation of concrete according to the invention, brick, ceramic or mixed recyclate from mixed inert construction and demolition waste with an upper fraction of 20 mm is mixed in an industrial mixer with forced circulation for 5 to 40 seconds, preferably for 5 to 20 seconds. After thorough mixing, concrete recyclate with an upper fraction of 20 mm or natural aggregate with an upper fraction of 20 mm, preferably 8 mm, or small 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 another 5 to 40 seconds, preferably for 5 to 20 seconds. After thorough mixing, finely ground brick, ceramic, mixed or concrete recyclate having a particle size of 5 to 250 μm, preferably 5 to 125 μm, and having a specific surface of 300 to 1500 m.sup.2/kg or finely ground brick, ceramic, mixed or concrete recyclate and microsilica and/or at least one substituent of microsilica is added to it either one by one in any order or simultaneously under constant mixing within 1 to 15 seconds, preferably within 1 to 10 seconds, and the mixture thus obtained is mixed for a further 5 to 80 seconds, preferably for 5 to 40 seconds. After that, cement is added to it under constant mixing within 1 to 20 seconds, preferably within 1 to 10 seconds, or cement and at least one substituent thereof is added either one by one in any order or simultaneously within 1 to 15 seconds, preferably within 1 to 10 seconds, and the mixture thus obtained is mixed for another 5 to 80 seconds, preferably for 5 to 40 seconds. As a substituent of cement can be used a further dose of finely ground brick, ceramic, mixed or concrete recyclate having a particle size of 5 to 250 μm, preferably 5 to 125 μm, and having a specific surface of 300 to 1500 m.sup.2/kg, which is dispersed in the concrete structure. Subsequently, this mixture is sprinkled with the entire dose of mixing water (which, if necessary, contains at least one additive for concrete) under constant mixing within 5 to 60 seconds, preferably within 5 to 40 seconds, or the entire dose of the mixing water is sprayed on it within 5 to 60 seconds, preferably within 5 to 40 seconds. After another 5 to 160 seconds of mixing, preferably after 5 to 80 seconds, fresh concrete is prepared, in which 60 to 100% by weight of aggregate is composed of recyclate from inert construction and demolition waste.

[0048] 8 samples of fresh concrete according to the invention were prepared by this method, whereby the composition of 1 m.sup.3 of each of them is described in Table 7.

[0049] These concretes were subsequently subjected to tests described in example 1. The results of these tests are summarized in Table 8.

[0050] In addition, chloride content in these concretes 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 of the State Office for Nuclear Safety No. 307/2002 Coll., as amended, on radiation protection, whereby all these parameters meet the requirements of this Regulation for use in buildings with residential rooms or spaces (mass activity .sup.226Ra≤150 Bq.Math.kg.sup.−1, mass activity index I≤0.5). According to the procedure of EN 12457 and Regulation of the Ministry of the Environment No. 294/2005 Coll. its ecotoxicity was found to be complying with the requirements. The criteria for the determination of ecotoxicity are shown in Table 4, example 1.

[0051] Table 9 shows strength classes of concrete to which the respective concretes belong due to their physical and mechanical parameters and classification classes of specification regarding use of these concretes according to CSN (Czech Technical Standard) EN 206 (see Table 6)

TABLE-US-00007 TABLE 7 Sample Component ERC 2/1 ERC 2/2 ERC 2/3 ERC 2/4 ERC 2/5 ERC 2/6 ERC 2/7 ERC 2/8 Mixed recyclate from mixed 1127 0 740 863 0 765 740 975 inert construction and demolition waste, fraction 0 to 20 mm [kg] Brick recyclate, fraction 0 1137 0 0 0 0 0 0 0 to 20 mm [kg] Ceramic recyclate, fraction 0 0 0 0 650 0 0 0 0 to 20 mm [kg] Concrete recyclate, fraction 0 0 740 863 650 765 740 975 0 to 20 mm [kg] Natural aggregate, fraction 420 390 0 0 0 0 0 0 0 to 4 mm [kg] Microsilica [kg] 25 15 0 0 5 10 25 10 Finely ground recyclate 75 10 50 150 30 100 120 20 from inert construction and demolition waste [kg] Cement [kg] 240 230 220 230 230 190 180 190 Substituent of cement [kg]/finely 0 70/0 100/0 100/50 150/20 60/20 190/150 100/50 ground recyclate from inert construction and demolition waste [kg] Concrete plasticizer or 0 0 6.6 6.9 7.6 4.5 4.8 4 superplasticizer [kg] Water [kg] 200 205 230 215 235 175 235 100 Volume weight of concrete 2020 2017 2010 2370 1915 2030 2190 2310 at age of 7 days [kg/m.sup.3] Volume weight of concrete 2015 2020 2010 2355 1910 2025 2190 2300 at age of 28 days [kg/m.sup.3]

TABLE-US-00008 TABLE 8 Sample Parameter ERC 2/1 ERC 2/2 ERC 2/3 ERC 2/4 ERC 2/5 ERC 2/6 ERC 2/7 ERC 2/8 Consistency of fresh 35 30 180 200 220 80 220 60 concrete - slump cone test [mm] Air content in fresh 2.4 2.0 3.5 3.3 3.4 2.0 2.3 2.4 concrete [%] Compressive strength [MPa] After 7 days 23.2 22.8 29.2 27.8 29.7 19.0 21.2 16.0 After 28 days 34.6 33.1 42.0 40.5 38.3 25.5 29.6 25.8 Flexural strength 3.3 3.1 4.5 4.2 3.9 2.8 2.9 2.3 after 28 days [MPa] Transverse tensile 3.7 — 4.1 — — — 3.5 3.3 strength after 28 days [MPa] Static modulus of 25.2 25.7 20.2 19.7 — 17.0 17.3 — elasticity [GPa]

TABLE-US-00009 TABLE 9 Sample ERC 2/1 ERC 2/2 ERC 2/3 ERC 2/4 ERC 2/5 ERC 2/6 ERC 2/7 ERC 2/8 Concrete C25/30 C20/25 C30/37 C25/30 C25/30 C16/20 C20/25 C16/20 strength class Specification X0 X0 X0 X0 X0 X0 X0 X0 of concrete XC1 XC1 XC1 XC1 XC1 XC1 XC1 XC1 use XC2 XC2 XC2 XC2 XC2 XC2 XC3 XC3 XC3 XC3 XC3 XC3 XC4 XC4 XC4 XC4 XC4 XC4 XD1 XD1 XD1 XD1 XD1 XD1 XD2 XD2 XD2 XD2 XD2 XD2 XF1 XA1 XF1 XF1 XF2 XF1 XF2 XF2 XF2 XF3 XF4

Example 3

[0052] For the preparation of concrete according to the invention, recyclate from inert construction and demolition waste with an upper fraction of 20 mm of the first type (brick, ceramic or mixed, alternatively concrete recyclate) is mixed in an industrial mixer with forced circulation for 5 to 40 seconds, preferably for 5 to 20 seconds. After thorough mixing, recyclate from inert construction and demolition waste with an upper fraction of 20 mm of the second type (brick, ceramic or mixed, alternatively concrete recyclate) is added to it under constant mixing, whereby the recyclate being added is recyclate from inert construction and demolition waste of a different type than the recyclate to which it is added, and the mixture thus obtained is mixed for another 5 to 40 seconds, preferably for 5 to 20 seconds. After that, finely ground brick, ceramic, mixed or concrete recyclate having a particle size of 5 to 250 μm, preferably 5 to 125 μm, and having a specific surface of 300 to 1500 m.sup.2/kg is added to it under constant mixing within 1 to 15 seconds, preferably within 1 to 10 seconds, or finely ground brick, ceramic, mixed or concrete recyclate and microsilica and/or at least one substituent thereof are added either one by one in any order or simultaneously, and the mixture thus obtained is mixed for a further 5 to 80 seconds, preferably for 5 to 40 seconds. After that, cement is added to it under constant mixing within 1 to 20 seconds, preferably within 1 to 10 seconds, or cement and at least one substituent thereof are added to it either one by one in any order or simultaneously within 1 to 15 seconds, preferably within 1 to 10 seconds, and the mixture thus obtained is mixed for a further 5 to 80 seconds, preferably for 5 to 40 seconds. As a substituent of cement it is possible to use another dose of finely ground brick, ceramic, mixed or concrete recyclate having a particle size of 5 to 250 μm, preferably 5 to 125 μm, and having a specific surface of 300 to 1500 m.sup.2/kg, which is dispersed in the concrete structure. Subsequently, this mixture is sprinkled with the entire dose of mixing water (which, if necessary, contains at least one additive for concrete) under constant mixing within 5 to 60 seconds, preferably within 5 to 40 seconds, or the entire dose of the mixing water is sprayed onto the mixture within 5 to 60 seconds, preferably within 5 to 40 seconds. After a further 5 to 160 seconds of mixing, fresh concrete is prepared, in which 100% by weight of aggregate is composed of recyclate from inert construction and demolition waste.

[0053] 3 samples of fresh concrete according to the invention were prepared by this method, whereby the composition of 1 m.sup.3 of each of them is described in Table 10.

TABLE-US-00010 TABLE 10 Sample Component ERC 3/1 ERC 3/2 ERC 3/3 Mixed recyclate from 755 1500 600 mixed inert construction and demolition waste, fraction 0 to 20 mm [kg] Brick recyclate, 765 580 1200 fraction 0 to 20 mm [kg] Microsilica [kg] 10 0 15 Finely ground recyclate 15 75 80 from inert construction and demolition waste [kg] Cement [kg] 200 200 200 Substituent of cement 100/20 50/50 120/100 [kg]/finely ground recyclate from inert construction and demolition waste [kg] Concrete plasticizer or 6.0 6.0 6.0 superplasticizer [kg] Water [kg] 247 130 225 Aerating agent for 0 0 0 concrete [%] Volume weight of 2210 2750 2730 concrete at age of 7 days [kg/m.sup.3] Volume weight of 2200 2750 2720 concrete at age of 28 days [kg/m.sup.3]

[0054] These concretes were subsequently subjected to the tests described in example 2. The results of these tests are summarized in Table 11.

TABLE-US-00011 TABLE 11 Sample Parameter ERC 3/1 ERC 3/2 ERC 3/3 Consistency of 190 30 190 fresh concrete - slump cone test [mm] Air content in fresh 5.5 — 4.5 concrete [%] Compressive 28.5 17.0 27.1 strength [MPa] After 7 days After 28 days 39.4 24.5 38.9 Static modulus of 21.0 14.5 20.5 elasticity [GPa]

[0055] In addition, 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 Regulation of the State Office for Nuclear Safety No. 307/2002 Coll., as amended, on radiation protection, whereby all these parameters meet the requirements of this Regulation for use for buildings with residential rooms or spaces (mass activity .sup.226Ra≤150 Bq.Math.kg.sup.−1, mass activity index I≤0.5). According to the procedure of EN 12457 and Regulation of the Ministry of the 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 4, example 1.

[0056] Table 12 shows strength classes of concrete to which the respective concretes according to the invention belong due to their physical and mechanical parameters and classification classes of specification regarding use of these concretes according to CSN (Czech Technical Standard) EN 206 (see Table 6).

TABLE-US-00012 TABLE 12 Sample ERC 3/1 ERC 3/2 ERC 3/3 Concrete C25/30 C16/20 C25/30 strength class Specification X0 X0 X0 of concrete XC1 XC1 XC1 use XC2 XC2 XC3 XC3 XC4 XC4 XD1 XD1 XD2 XD2 XF1 XF1 XF2 XF2

Example 4

[0057] For the preparation of concrete according to the invention, recyclate from inert construction and demolition waste with an upper fraction of 20 mm of the first type (brick, ceramic or mixed, alternatively concrete recyclate) is mixed in an industrial mixer with forced circulation for 5 to 40 seconds, preferably for 5 to 20 seconds. After thorough mixing, recyclate from inert construction and demolition waste with an upper fraction of 20 mm of the second type (brick, ceramic or mixed, alternatively concrete recyclate) is added to it under constant mixing, whereby the recyclate being added is recyclate from inert construction and demolition waste of a different type than the recyclate to which it is added, and the mixture thus obtained is mixed for another 5 to 40 seconds, preferably for 5 to 20 seconds. After thorough mixing, recyclate from inert construction and demolition waste with an upper fraction of 20 mm or natural aggregate with an upper fraction of 20 mm, preferably 8 mm, or small 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 40 seconds. Thereafter, finely ground brick, ceramic, mixed or concrete recyclate having a particle size of 5 to 250 μm, preferably 5 to 125 μm, and having a specific surface of 300 to 1500 m.sup.2/kg is added to it under constant mixing within 1 to 15 seconds, preferably within 1 to 10 seconds, or finely ground brick, ceramic, mixed or concrete recyclate and microsilica and/or at least one substituent thereof are added to it either one by one in any order or simultaneously, and the mixture thus obtained is mixed for a further 5 to 80 seconds, preferably for 5 to 40 seconds. After that, cement is added to it under constant mixing within 1 to 20 seconds, preferably within 1 to 10 seconds, or cement and at least one substituent thereof is added to it within 1 to 15 seconds, preferably within 1 to 10 seconds either one by one in any order or simultaneously, and the mixture thus obtained is mixed for a further 5 to 80 seconds, preferably for 5 to 40 seconds. As a substituent of cement it is possible to use another dose of finely ground brick, ceramic, mixed or concrete recyclate having a particle size of 5 to 250 μm, preferably 5 to 125 μm, and having a specific surface of 300 to 1500 m.sup.2/kg, which is dispersed in the concrete structure. Subsequently, this mixture is sprinkled with the entire dose of mixing water (which, if necessary, contains at least one additive for concrete) under constant mixing within 5 to 60 seconds, preferably within 5 to 40 seconds, or the entire dose of mixing water is sprayed on it within 5 to 60 seconds, preferably within 5 to 40 seconds. After another 5 to 160 seconds, preferably after 5 to 80 seconds, of mixing, fresh concrete is prepared, in which it is up to 100% by weight of aggregate that is composed of recyclate from inert construction and demolition waste.

[0058] 3 samples of fresh concrete according to the invention were prepared by this method, whereby the composition of 1 m.sup.3 of each of them is described in Table 13.

TABLE-US-00013 TABLE 13 Sample Component ERC 4/1 ERC 4/2 ERC 4/3 Mixed recyclate from 500 0 420 mixed inert construction and demolition waste, fraction 0 to 20 mm [kg] Brick recyclate, 500 900 500 fraction 0 to 20 mm [kg] Ceramic recyclate, 0 500 0 fraction 0 to 20 mm [kg] Concrete recyclate, 700 300 500 fraction 0 to 20 mm [kg] Microsilica [kg] 15 25 20 Finely ground recyclate 10 20 50 from inert construction and demolition waste Cement [kg] 230 300 180 Substituent of cement 90/90 0 150/120 [kg]/finely ground recyclate from inert construction and demolition waste [kg] Concrete plasticizer or 4.9 5.5 4.5 superplasticizer [kg] Water [kg] 230 190 200 Volume weight of 2400 2370 2200 concrete at age of 7 days [kg/m.sup.3] Volume weight of 2370 2350 2190 concrete at age of 28 days [kg/m.sup.3]

[0059] These concretes were subsequently subjected to the tests described in example 2. The results of these tests are summarized in Table 14.

TABLE-US-00014 TABLE 14 Sample Parameter ERC 4/1 ERC 4/2 ERC 4/3 Consistency of 190 200 140 fresh concrete - slump cone test [mm] Air content in fresh 5.1 4.5 4.2 concrete [%] Compressive 22.3 25.4 21.2 strength [MPa] After 7 days After 28 days 37.2 39.4 34.7 Flexural strength 3.8 3.5 — after 28 days [MPa] Static modulus of 21.3 21.8 20.5 elasticity [GPa]

[0060] In addition, 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 Regulation of the State Office for Nuclear Safety No. 307/2002 Coll., as amended, on radiation protection, whereby all these parameters meet the requirements of this Regulation for use for buildings with residential rooms or spaces (mass activity .sup.226Ra≤150 Bq.Math.kg.sup.−1, mass activity index I≤0.5). According to the procedure of EN 12457 and Regulation of the Ministry of the 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 4, example 1.

[0061] Table 15 shows strength classes of concrete to which the respective concretes according to the invention belong due to their physical and mechanical parameters and classification classes of specification regarding use of these concretes according to CSN (Czech Technical Standard) EN 206 (see Table 6).

TABLE-US-00015 TABLE 15 Sample ERC 4/1 ERC 4/2 ERC 4/3 Concrete C25/30 C25/30 C25/30 strength class Specification X0 X0 X0 of concrete XC1 XC1 XC1 use XC2 XC2 XC2 XC3 XC3 XC3 XC4 XC4 XC4 XD1 XD1 XD1 XD2 XD2 XD2 XA1 XA1 XA1

Example 5

[0062] For the preparation of concrete according to the invention, concrete recyclate with an upper fraction of 20 mm is mixed in an industrial mixer with forced circulation for 5 to 40 seconds, preferably for 5 to 20 seconds. After thorough mixing, natural aggregate with an upper fraction of 20 mm (up to 40% by weight of the total aggregate in concrete) is added to it under constant mixing, and the mixture thus obtained is mixed for another 5 to 40 seconds, preferably for 5 to 20 seconds. After that, finely ground brick, ceramic, mixed or concrete recyclate having a particle size of 5 to 250 μm, preferably 5 to 125 μm, and having a specific surface of 300 to 1500 m.sup.2/kg is added to it under constant mixing within 1 to 15 seconds, preferably within 1 to 10 seconds, or finely ground brick, ceramic, mixed or concrete recyclate and microsilica and/or at least one substituent of microsilica are added to it either one by one in any order or simultaneously, and the mixture thus obtained is mixed for a further 5 to 80 seconds, preferably for 5 to 40 seconds. Subsequently, cement is added to it under constant mixing within 1 to 20 seconds, preferably within 1 to 10 seconds, or cement and at least one substituent thereof is added to it one by one in any order or simultaneously within 1 to 15 seconds, preferably within 1 to 10 seconds, and the mixture thus obtained is mixed for another 5 to 80 seconds, preferably for 5 to 40 seconds. As a substituent of cement it is possible to use another dose of finely ground brick, ceramic, mixed or concrete recyclate, having a particle size of 5 to 250 μm, preferably 5 to 125 μm, and having a specific surface of 300 to 1500 m.sup.2/kg, which is dispersed in the concrete structure. Subsequently, the mixture is sprinkled with the entire dose of mixing water (which, if necessary, contains at least one additive for concrete) under constant mixing within 5 to 60 seconds, preferably within 5 to 40 seconds, or it is sprayed with the entire dose of mixing water within that period. After another 5 to 160 seconds, preferably after 5 to 80 seconds, of mixing, fresh concrete is prepared, in which at least 60% by weight of aggregate is composed of recyclate from inert construction and demolition waste.

[0063] 5 samples of fresh concrete according to the invention were prepared by this method, whereby the composition of 1 m.sup.3 of each of them is described in Table 16.

TABLE-US-00016 TABLE 16 Sample Component ERC 5/1 ERC 5/2 ERC 5/3 ERC 5/4 ERC 5/5 Concrete recyclate, 1210 1000 980 800 860 fraction 0 to 20 mm [kg] Natural aggregate, 450 300 450 800 520 fraction 0 to 4 mm [kg] Microsilica [kg] 10 0 0 0 0 Finely ground recyclate 20 50 150 80 100 from inert construction and demolition waste [kg] Cement [kg] 220 200 150 190 190 Substituent of cement 50/0 100/40 150/100 150/120 150/150 [kg]/finely ground recyclate from inert construction and demolition waste [kg] Concrete plasticizer or 0 5 3 1 0 superplasticizer [kg] Water [kg] 220 150 100 175 190 Volume weight 2480 2070 2210 2300 2210 of concrete at age of 7 days [kg/m.sup.3] Volume weight 2460 2060 2210 2290 2200 of concrete at age of 28 days [kg/m.sup.3]

[0064] These concretes were subsequently subjected to the tests described in example 1. The results of these tests are summarized in Table 17.

TABLE-US-00017 TABLE 17 Sample Parameter ERC 5/1 ERC 5/2 ERC 5/3 ERC 5/4 ERC 5/5 Consistency of fresh 120 80 10 70 140 concrete - slump cone test [mm] Air content in fresh 2.4 4.5 - 3.0 2.5 concrete [%] Compressive strength 28.8 26.5 16.0 17.2 20.2 [MPa] After 7 days After 28 days 40.5 36.5 24.5 25.7 29.7 Flexural strength 3.8 3.2 — 2.2 2.7 after 28 days [MPa] Static modulus 24.5 23.1 — 17.0 17.7 of elasticity [GPa]

[0065] In addition, 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 Regulation of the State Office for Nuclear Safety No. 307/2002 Coll., as amended, on radiation protection, whereby all these parameters meet the requirements of this Regulation for use for buildings with residential rooms or spaces (mass activity .sup.226Ra≤150 Bq.Math.kg.sup.−1, mass activity index I≤0.5). According to the procedure of EN 12457 and Regulation of the Ministry of the 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 4, example 1.

[0066] Table 18 shows strength classes of concrete to which the respective concretes according to the invention belong due to their physical and mechanical parameters and classification classes of specification regarding use of these concretes according to CSN (Czech Technical Standard) EN 206 (see Table 6).

TABLE-US-00018 TABLE 18 Sample ERC 5/1 ERC 5/2 ERC 5/3 ERC 5/4 ERC 5/5 Concrete C25/30 C25/30 C16/20 C16/20 C20/25 strength class Specification X0 X0 X0 X0 X0 of concrete XC1 XC1 XC1 XC1 XC1 use XC2 XC2 XC2 XC3 XC3 XC3 XC4 XC4 XC4 XD1 XD1 XD1 XD2 XD2 XD2 XA1 XA1

[0067] In all the above cases, 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 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. Preferably, this material is added prior to the addition of microsilica and/or substituent(s) thereof. In all these cases, recyclate from inert construction and demolition waste constitutes at least 45% by weight of the total aggregate in the concrete.

[0068] If necessary, it is possible to add to any of the concretes described above reinforcing fibers of at least one type which reinforce the concrete structure and thereby improve some of its properties, e.g. tensile strength and flexural strength. Such 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 finely ground brick, ceramic, mixed or concrete recyclate or a mixture of finely ground brick, ceramic, mixed or concrete recyclate and microsilica and/or at least one 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.sup.3 of fresh concrete, in the case of steel and similar fibers the total amount being up to 25 kg/m.sup.3 of fresh concrete. Reinforcing fibers are added to the concrete mixture under constant mixing within 5 to 30 seconds, which ensures their uniform distribution in it.

[0069] If all the components of the aggregate with an upper fraction of 8 mm are used, fresh concrete with a finer texture is prepared using the same processes, sometimes referred to as cement mortar or concrete mortar.

[0070] The 0 to 20 mm aggregate fraction described in the above examples does not limit 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.

[0071] 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. In addition to fresh concrete (transport concrete) for the construction of houses, hotels, residential buildings, office buildings, industrial buildings, production halls, special purpose facilities, medical facilities, etc., or for their parts, such as pillars and posts, floors, lintels in lengths up to approximately 6 m, base plates or bases, foundation concrete, etc., 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. Their advantage is good transportability, or, pumpability. Moreover, all variants are concretes which are 100% recyclable in the same way they were produced.