Method for the Preparation of a Carbonated Mineral Component, Carbonated Mineral Component, and Method for the Preparation of a Hydraulic Binder

Abstract

The invention relates to a method for the preparation of a carbonated mineral component in particular for the use as a substituent of cement in hydraulic binder compositions wherein a raw material comprising at least one of the group of concrete demolition waste, hardened concrete paste, hardened cement paste, or any mineral component containing hydrated calcium silicates, calcium aluminates is carbonated and heated, a carbonated mineral component manufactured in this way, a method for the preparation of a hydraulic binder using the carbonated mineral component and a cementitious component as well as a concrete composition with that hydraulic binder.

Claims

1-28. (canceled)

29. A method for the preparation of an at least partially carbonated mineral component, comprising the steps of: providing a raw material including at least one of concrete demolition waste, recycled cement paste, hardened concrete paste, hardened cement paste, concrete fines, dried concrete sludges, and a mineral component containing hydrated calcium silicates and/or calcium aluminates; and heating and optionally carbonating the raw material, wherein the raw material is heated to a temperature T.sup.0 e of 250 e<T.sup.0 e<800 e.

30. The method of claim 29, wherein the raw material is either composed entirely of hardened cement paste, or a mixture of hardened cement paste and partially ground sand or aggregates including at least 10% by weight hardened cement paste.

31. The method of claim 29, wherein the carbonating step is performed before, during, or after the heating step.

32. The method of claim 29, further comprising the step of crushing the raw material to a fineness of 0.1 to 0.5 mm.

33. The method of claim 32, further comprising the step of grinding the raw material to a Blaine fineness of at least 2,000 cm.sup.2/g.

34. The method of claim 29, wherein the heating is performed in a heat exchanger or by miking the raw material with hot clinker.

35. The method of claim 29, wherein the heating is performed using a vertical counterflow heat exchanger, a fluidized bed heat exchanger, or an apparatus that transfers heat from a gas flow to powdered raw material.

36. The method of claim 29, wherein the heating is performed in a heat exchanger that uses sustainable energy.

37. The method of claim 36, wherein the sustainable energy is derived from at least one of a combustion of biogas, gases from pyrolysis of renewable raw materials, hydrogen manufactured by electrolysis of water, solar heat from a solar furnace, and electricity from solar, wind or water energy.

38. The method of claim 29, wherein the heating is performed using heat from one or more industrial processes.

39. The method of claim 29, wherein carbonating the raw material is performed using CO.sub.2 generated from at least one of a cement kiln from decarbonation of limestone and combustion of fuel, combustion of biogas, gases from pyrolysis of renewable raw materials, sourcing of energy by combustion, industrial processes, and ambient air.

40. The method of claim 33, wherein carbonating the raw material is performed during or after the grinding, or before or during the heating.

41. The method of claim 29, wherein carbonating the raw material comprises a wet carbonation of the raw material followed by the heating.

42. The method of claim 29, wherein carbonating the raw material comprises dry carbonation at a temperature above 300 C. using calcium oxide originating from at least one of calcium-silicate-hydrate, Ca(OH).sub.2, and Ca-rich phases generated by thermal activation of the foregoing.

43. The method of claim 29, wherein carbonating the raw material comprises wet carbonation in the presence of water or steam present in an amount of at least 5% based on a dry weight of the raw material.

44. The method of claim 33, wherein carbonating the raw material comprises wet carbonation using at least one of water or steam during the grinding, and water or steam injection during the heating.

45. The method of claim 29, wherein carbonating the raw material comprises wet carbonation, and the wet carbonation includes injecting CO.sub.2 in an amount of at least 10% based on a total gas volume present during the wet carbonation.

46. The method of claim 29, wherein carbonating the raw material comprises wet carbonation conducted in an autoclave using saturated steam and a CO.sub.2 containing gas under high pressure.

47. The method of claim 46, wherein the raw material is present as powdered raw material, the powdered raw material is agitated while being autoclaved, and the powdered raw material is subjected to deagglomeration after autoclaving.

48. The method of claim 29, wherein carbonating the raw material comprises dry carbonation carried out in a low humidity atmosphere having a humidity less than 5% based on a dry weight of the raw material.

49. A carbonated mineral component produced according to a method that comprises the following steps: providing a raw material including at least one of concrete demolition waste, recycled cement paste, hardened concrete paste, hardened cement paste, concrete fines, dried concrete sludges, and a mineral component containing hydrated calcium silicates and/or calcium aluminates; and heating and optionally carbonating the raw material, wherein the raw material is heated to a temperature T.sup.0 e of 250 e<T.sup.0 e<800 e.

50. The carbonated mineral component of claim 49, having a Blaine fineness between 2,000 cm.sup.2/g and 10,000 cm.sup.2/g.

51. A method for preparing a hydraulic binder composition, comprising the steps of: providing a carbonated mineral component according to the method of claim 29; and mixing the carbonated mineral component with a cementitious component selected from Portland cement, a Portland cement clinker, and combinations thereof.

52. The method of claim 51, further comprising the steps of milling the carbonated mineral component, wherein the carbonated mineral component is added to the cementitious component before or during the milling and ground together with the cementitious component to obtain the hydraulic binder composition.

53. The method of claim 52, wherein the hydraulic binder composition comprises about 25% to about 75% by weight of the carbonated mineral component.

54. The method of claim 29, further comprising the step of using the carbonated mineral component as a substituent for cement a hydraulic binder composition.

55. A hydraulic binder composition for mortars and concrete, comprising: a carbonated mineral component prepared according to the method of claim 29; and a cementitious component selected from Porland cement, a Porland cement clinker, and mixtures thereof.

56. A concrete composition comprising a hydraulic binder composition that includes a carbonated mineral component having a Blaine fineness of 2,000 cm.sup.2/g to 10,000 cm.sup.2/g and at least one of Porland cement and a Porland cement clinker.

Description

[0096] The invention is explained by way of examples and a accompanied drawing which shows in:

[0097] FIG. 1: a schematic process flowchart;

[0098] FIG. 2: a suitable device for the heating of the raw material;

[0099] FIG. 3: another schematic flow chart;

[0100] FIG. 4: the compressive strength at 2, 7 and 28 days of comparative examples, wherein concrete demolition waste replaces a cement by 25% and a calcination of 450 C.;

[0101] FIG. 5: the compressive strength at 2, 7 and 28 days of comparative examples, wherein concrete demolition waste replaces a cement by 25% and a calcination of 600 C.;

[0102] FIG. 6: the compressive strength at 2, 7 and 28 days of comparative examples, wherein recycled concrete fines replace a cement by 25% and a calcination of 450 C.;

[0103] FIG. 7: the compressive strength at 2, 7 and 28 days of comparative examples, wherein recycled concrete fines replace a cement by 25% and a calcination of 600 C.;

[0104] FIG. 8: the compressive strength at 2, 7 and 28 days of comparative examples, wherein concrete sludge replace a cement by 25% and a calcination of 550 C.;

[0105] FIG. 9: the compressive strength after 28 days of a CEM I 52,5 N in comparison to examples in which the cement was replaced by 25% recycled cement paste, calcined recycled cement paste and carbonated calcined recycled cement paste, calcination at 450 C.;

[0106] FIG. 10: the compressive strength after 28 days of a CEM I 52,5 N in comparison to examples in which the cement was replaced by 50% recycled cement paste, calcined recycled cement paste and carbonated calcined recycled cement paste, calcination at 450 C.;

[0107] The method according to the invention comprises two substantial steps in the processing.

[0108] One substantial step is the heating of the first raw material wherein the raw material may consist of one or more of the group of concrete demolition waste, hardened concrete paste, hardened cement paste or any mineral component containing hydrated calcium silicates, calcium aluminates and the like.

[0109] The purpose of the heating step is that the heat treatment of said first raw material results in a material that has a pozzolanic reactivity so that the heating step can be seen as an activation step.

[0110] The heating step can be performed in any suitable device which is capable of transferring heat to a raw material which consists of particles and in particular fine particles. The particles to be activated may be particles which are obtained by crushing said raw material. In this case the particle size would be preferable between 0.1 and 5 mm.

[0111] If it is desired it is possible to grind the crushed material to a Blaine fineness of at least 2000 cm.sup.2/g, preferably more than 3000 cm.sup.2/g and more preferred 4000 cm.sup.2/g or more, measured as described in the standard EN 196-6:2018.

[0112] To transfer heat into this material a device as shown in FIG. 3 may be used which is a kind of a rotary drum-like heat exchanger.

[0113] Such a heat exchanger may be heated by an electrical heating which is for example circumferential placed at the outer wall of the drum-like heat exchanger. Especially in cases where a powdered material is heated, such a rotary heat exchanger may be advantageous.

[0114] Especially finally ground material as set forth above can be heated in a fluidized bed device where a hot gas is conducted through the finely ground material.

[0115] The heating is conducted in such a way that the raw material is heated to temperatures between 250 C. and 650 C., preferentially between 400 C. and 600 C.

[0116] The energy needed for heating the raw material may be electrical energy or a hot gas flow wherein in both cases it is preferred to use sustainable energy for the heating.

[0117] Sustainable energy in case of electrical energy may be energy from solar power, wind energy, water energy or the like.

[0118] Further, hot gas flows from other industrial processes may be used.

[0119] These gas flows can be used directly in case the temperature range is in the respective area between 250 C. and 650 C., whereby gases with higher temperatures may be cooled down. These gas flows can be used directly by flowing through the fluidized bed, for example, or indirectly by heating-up a gas-like ambient air via a heat exchanger. The latter may occur for example if the gas flow is contaminated within gradients which are not appreciated in the product.

[0120] Examples for these gas flows can be the hot gas from the rotary cement kiln or from a cement clinker cooling device.

[0121] Further, hot gas streams can be achieved by combustion of combustible liquids or gases. It is preferred that these combustible liquids or gases originate from sustainable processes.

[0122] This may be, for example, hydrogen originating from the electrolysis of water by sustainable electrical energy, combustion of biogas like biomethane or methane which is produced by the microbiobal recombination of hydrogen with CO.sub.2 in natural gas reservoirs, alcohol from the fermentation of sustainable vegetable products or the paralysis of vegetable sustainable products.

[0123] Besides this first substantial step of pozzolanic activation by heating, a second substantial step is carried out which is a carbonation of the raw material.

[0124] In general, the carbonation can be carried out after or during the crushing and grinding of the concrete waste. Preferentially, the carbonation step is carried out after the crushing and grinding of the concrete waste.

[0125] In cases where concrete sludges are used, crushing and grinding may not be required.

[0126] Further, the carbonation can be carried out as a wet carbonation or a dry carbonation.

[0127] The definition of a wet and a dry carbonation has been given above.

[0128] In general, the carbonation may be carried out with CO.sub.2 enriched gas flows as already mentioned wherein this CO.sub.2 enriched gas flows may be separate gas flows with CO.sub.2 from ambient air or with CO.sub.2 from industrial processes and the like. The carbonation can be partially or fully achieved by the gas flows used for the heating as well.

[0129] In case a carbonation is done during the heating step which means, for example, at the beginning during or at the end of the heating step, the same devices are used.

[0130] Further to the above-mentioned devices heating and carbonation may take place in an autoclave with steam or saturated steam, the CO.sub.2 rich gas and heat.

[0131] After the two substantial steps a deagglomeration step may be conducted in cases needed.

[0132] The deagglomeration step may be a joint grinding and mixing step of the carbonated mineral component according to the invention and cement clinker in a rotary mill.

[0133] One example of carrying out the invention is schematically shown in FIG. 1.

[0134] After the crushing of the raw material, the raw material is ground to a Blaine fineness of about 4000 cm.sup.2/g, measured as described in the standard EN 196-6:2018. At this stage the carbonation can take place wherein grinding is done under a CO.sub.2 enriched gas flow or CO.sub.2 containing atmosphere.

[0135] Alternatively or additionally, a carbonation step can be carried out afterwards wherein the carbonation as already pointed out can be done in various devices and by various ways as long as the ground raw material is perfused by the CO.sub.2 enriched gas flow. Afterwards, the heating of the crushed and/or ground raw material is performed at temperatures of 450 C. or 600 C. Alternatively or additionally carbonation can take place even during the heating of the ground raw material.

[0136] After the heating step and the cooling of the in this way achieved material, the carbonated mineral component produced in this manner is mixed with Portland cement as a substitute of that cement component.

[0137] In FIG. 3 two general processing paths for examples of the invention are shown in which in a first process a carbonation takes place before heating but without grinding and the grinding is conducted after the heating step.

[0138] In a second process the raw material is ground to 4000 cm.sup.2/g, afterwards carbonated and then heated.

[0139] FIGS. 4 and 5 show comparative examples, wherein samples in which a portland cement is replaced by 25% concrete demolition waste are compared. The calcination temperature if applied was 450 C. in FIG. 4 and 600 C. in FIG. 5.

[0140] The dotted lines show the compressive strength of a CEM I 52,5 N after 2, 7 and 28 days.

[0141] Four cases are shown from the left to the right: concrete demolition waste, carbonated concrete demolition waste, calcined demolition waste and carbonated and calcined concrete demolition waste.

[0142] As it can be seen the short term compressive strength (2 days) is in both charts for every sample nearly the same. The same appears for the 7 day medium term compressive strength. Although it is obvious that calcination of the Concrete demolition waste leads to a somewhat higher strength and carbonation and calcination increase said strength further. In comparison between the calcination temperatures the higher temperature increases for carbonated and calcined concrete demolition waste the strength only slightly for the other samples not at all.

[0143] The same appears having a look on the long term compressive strength. An increase is shown by calcination and further by calcination and carbonation om one hand.

[0144] On the other hand a slight increase in compressive strength after 28 days can be derived by the higher calcination temperature.

[0145] In FIGS. 6 and 7 charts are presented in which the effect of recycled concrete fines is shown. Again the portland cement is replaced by 25% and the calcination temperatures are 450 C. and 600 C.

[0146] It seems that the carbonation has in this samples a stronger effect on the short and medium term compressive strength rather than the calcination temperature which has a slight increasing effect.

[0147] In FIG. 8 samples are shown in which a portland cement is replaced by 25% concrete sludge, carbonated concrete sludge and carbonated and calcined concrete sludge respectively are compared. The calcination temperature was 550 C.

[0148] As a result the carbonation increases the medium and long term compressive strength remarkably. The carbonation and calcination is increasing that compressive strength even more.

[0149] FIGS. 9 and 10 show samples in which a CEM I 52,5 and samples in which that cement is replaced by 25% (FIG. 9) and 50% (FIG. 10) of recycled cement paste. The calcination temperature is 450 C. in both cases.

[0150] As it could be expected from the other samples in comparison to recycled cement paste the calcination leads to a higher 28 day compressive strength. With a carbonated and calcined recycled cement paste the compressive strength is increases even more.

[0151] The compressive strength is at a replacement of 50% somewhat lower but still remarkably high

[0152] The concrete demolition waste used for these examples is partially carbonated, as throughout its lifetime, it was exposed to the CO.sub.2 present in the air. The examples show that the method of present invention provides outstanding performance even if the waste material is partially carbonated prior its treatment according to the present invention.

[0153] As a result, even without carbonation heating a recycled cement paste or other raw material as set forth above to a temperature between 250 C. and 650 C. results in a mineral component which is able to contribute to the 28-day compressive strength of a binder composition.

[0154] As a further result the incorporation of CO.sub.2 by carbonation of the raw material in a suitable manner results in a carbonated mineral component, capable of contributing to the strength of a mineral component, even if it is heated at lower temperatures (450 C.) and further acts a CO.sub.2 trap.

[0155] By using sustainable energy for the heating of the mineral component, the carbon footprints of the mineral component can be put down to zero and the overall carbon footprint of a binder composition with that mineral component and a cement component can be lowered remarkably.

[0156] Heating the raw material in said manner and carbonating it absorbs CO.sub.2 and serves as a CO.sub.2 trap and may in a mixture with a cementitious component for a hydraulic binder composition brings the carbon footprint of the overall binder composition to zero.