WO2013079732A1

WO2013079732A1 - Air setting method for obtaining prefabricated parts with binding matrices, matrices and prefabricated parts thus obtained and use thereof

Info

Publication number: WO2013079732A1
Application number: PCT/ES2011/070826
Authority: WO
Inventors: Miguel Bermejo Sotillo; Carlos Rodriguez Navarro; Encarnación RUIZ AGUDO; Kerstin Elert
Original assignee: Geosilex Trenza Metal, S.L.
Priority date: 2011-11-29
Filing date: 2011-11-29
Publication date: 2013-06-06

Abstract

The invention relates to a method, accelerated by forced autoclaved carbonation, for the air setting of prefabricated parts with binding matrices including calcium hydroxide, using hydraulic and/or non-hydraulic limes, preferably carbide nano-limes, in which the setting rate is increased in relation to known processes by means of the addition of carbonic anhydrase as a catalytic carbonation accelerator. In order to promote ultra-rapid carbonation, once the parts have been sufficiently hardened and removed from the mould, they are introduced into an autoclave and the air is extracted therefrom by means of vacuum and replaced with CO ₂ and water vapour until the carbonation thereof. In addition to ultra-rapid air setting, the method can also be used for the industrial production of prefabricated parts having good early-age mechanical properties.

Description

PROCEDURE OF AIR FRAGUADO FOR THE OBTAINING OF PREFABRICATED PARTS WITH CEMENTING MATRICES, MATRICES AND PREFABRICATED PARTS SO OBTAINED AND USE OF THE SAME

The present invention relates to an air setting procedure for obtaining prefabricated pieces with cementitious matrices, the matrices used in this procedure and the prefabricated parts obtained by the application of the procedure, for use, among other fields, in construction , public works or street furniture. More particularly, the process of the invention consists of an air setting procedure, accelerated by forced carbonation in autoclave, of prefabricated pieces with cementitious matrices that include calcium idroxide, from artificial hydraulic limes and / or aerial, preferably carbide limes, where the setting speed is increased to a high degree compared to the setting processes known for the addition of carbonic anhydrase as the catalytic accelerator of carbonation. In order to favor ultrafast carbonation according to the process of the invention, the pieces, demoulded after having been sufficiently endured, are placed in an autoclave where the air is removed by vacuum and replaced by CO ₂ and water vapor until carbonation. The present procedure, in addition to an ultra-fast air setting, allows to obtain prefabricated parts with high mechanical performance at an early age.

In another aspect of the invention, this refers to matrices for cementitious mixtures based on carbide limes, that is hydrated calcium limes derived from the manufacture of acetylene from calcium carbide, in particular paste nanocals obtained from the residues which are generated in the manufacture of acetylene, also comprising water, pozzolans, aggregates and CO ₂ matrices, all of them obtained from industrial waste, obtained from the process of the present invention. The invention relates, according to a third aspect, to prefabricated parts produced from the process of the invention, in any form geometric possible, as well as its use in construction, public works and street furniture.

Lime mortars and mortars traditionally used until the 19th century in the construction industry quickly became obsolete after the invention of Portland cement, since it reached high mechanical performance in a very short time. However, cement manufacturing implies a very high energy cost while contributing to the emission of large amounts of CO2, a greenhouse gas that penalizes production. All limes (Ca (OH) ₂ ) are hardened by air setting, in contact with air, and some also by hydraulic setting, in contact with water, as is the case with hydraulic limes, whether natural (fruit of calcination of impure limestones with a certain content of aluminosilicates such as clays) or artificial ones (with pozzolanic additives). Both processes are independent and their duration is very different. The setting by the addition of (hydraulic) water ends in a few hours, but the air setting can last for years and even use according to the characteristics of the mortar or concrete (composition, porosity, thickness, etc.) and the environmental conditions .

By means of aerial setting, high strength and stability materials are obtained by the transformation of calcium hydroxide, in contact with CO2 and in the presence of certain humidity, in calcium carbonate, of high cementing power.

Among the types of precast concrete and concrete known, it is possible to mention that made under vacuum conditions called "vacuum treated concrete", where the concrete is subjected to suction (accompanied or not by a compaction process) immediately after being put in a mold. In this process part of the moisture is extracted leaving a drier concrete that, after a while, will reach a much greater hardness than that of common concrete. This causes a vacuum process to be used in the manufacture of concrete slabs and similar products made with hydraulic presses. In this regard, US Patent 2046867, "Method of and apparatus for treating concrete", refers to a method for treating concrete that consists of treating the concrete with an excess of water to ensure plasticity and then apply a suction to imitate excess water from the breast of the same and then apply a large compaction pressure.

Various methods have been suggested to induce air setting by forced carbonation of materials based on Ca (OH) ₂ , such as compacted pastes at pressures ranging between 0.65 and 6 MPa (De Silva et al. 2006, Carbonate binders: Reactionkinetics, strength and microstructure Cement & Concrete Composites, 28, 613-620). Such materials once carbonated at CO2 pressures from 0.1 MPa to 2 Mpa experience an increase in their resistance to compression from values of 1.5 MPa to 15 MPa. The main disadvantage of this technology is that it is applied to materials smaller than 1, 6 cm.

O. Matsuda and H. Yamada, in "Experimental Study of the Manufacture of Building Materials by Carbonation of Slaked Lime.", Gypsum & Lime, 125 (1973), pp. 8-17, indicate the possibility of obtaining materials of high mechanical resistance from lime if in the manufacturing process the element is compacted at a high pressure (from 10 to 100 MPa).

Thus, US 4362679, "Method of casting concrete", describes a method for producing carbonated cement-based elements in an accelerated manner. This method consists in vacuum extraction of moisture and gases from an already molded paste based on cement, with different types of aggregates and additives, achieving its compaction. After that, the cement paste is subjected to forced carbonation under an atmosphere of pCO2 of up to 1.5 atm. The forced carbonation of cement-based building elements is also described in US 5,650,562 and US 5,744,078. However, the use of lime as the main binder or of any carbonation accelerator is not contemplated in the cited patents.

On the other hand, there are studies of forced carbonation of mortars developed by mixing lime with water and aggregates in various proportions. After said forced carbonation in an atmosphere of 100% CO2 and at a pressure of 1 bar, products with compressive strength values are obtained that double or triple the resistance of the product subjected to carbonation in the air. However, the times required to carbonate material thicknesses of A few mm are days or weeks, which makes such a system impractical from an industrial point of view.

Other methods for manufacturing compact construction materials produced by forced carbonation of lime pastes with or without aggregate addition are those indicated in W. Uschmann, Production of Compact Construction Elements from Lime and Admixtures by Treatment with Carbon Dioxide Gas. Translation from SR BST, 29 (1974), pp. 7-23. However, one of the main drawbacks of the setting and hardening process by reacting Ca (OH) ₂ with CO2 to form a CaCO3 binder is the low rate of the carbonation reaction. This is an effect that greatly limits the preparation in reasonable times of lime-based elements for use in construction.

To reduce carbonation time, on the one hand, high concentrations of CO2 help reduce such times, but not enough so that the process is effective from an industrial point of view (Cultroney col. 2005, Cement and Concrete Research, 35, 2278-2289).

In this regard, US Patent 3,149,986 indicates that it is possible to obtain prefabricated elements (artificial stone) made from calcified hydrated lime and dolomitic aggregate with a high tensile strength of 4.27 MPa after subjecting them to forced carbonation during 48 h; while patent GB774.432 indicates that, using similar materials, products with compressive strength of up to 48 MPa are obtained after a forced carbonation period of three weeks.

In other cases, the use of additives that act as carbonation accelerators has been proposed. Thus, DE 1,197,369, "Veríahren zur Verbesserung der Carbonisation von Calcium hydroxyd in Bau- und Anstrichstoffen" proposes the addition of alcohols and / or sugars to obtain a faster carbonation of lime mortars.

In WO 95/04010, "A low shrinkage cement composition" proposes the addition of carbamates that release CO2 in an alkaline environment, which could on the one hand accelerate carbonation and on the other reduce the shrinkage of cement elements. European patent EP 0650940 A1, "Inorganic hardening composition", proposes the addition of a compound based on organic carbonic acid (olefinic carbonate, soluble carbonates of amines, carbamic acid or even urea) to prepare inorganic prefabricated products. However, such parts need at least 28 days to achieve an adequate mechanical strength value.

In general, the results obtained in the indicated inventions are not satisfactory, especially in regard to the very slow carbonation rate, of days or weeks, since one of the aspects not considered to date is that the slowest reaction that controls the overall kinetics of the carbonation process of Ca (OH) ₂ is the dissolution of atmospheric CO2 in the water or in the pores of the lime-based element to be carbonated.

Thus, according to a first aspect of the invention, this refers to a process that allows to favor carbonation and make it progress more rapidly. To this end, the method of accelerated aerial setting by forced carbonation in the autoclave of the invention includes a step of adding a carbonation accelerator and this, in addition, is favored by extracting the air from the mixture to replace it with CO2 and water vapor. dosed in specific concentrations.

Said carbonation reaction can be accelerated as proposed in this invention, without having to significantly increase the hardening temperature of the prefabricated parts and pressures of CO2 is relatively lower than those used in the prior art methods, adding carbonic anhydrase to the fresh paste in appropriate proportions.

In this regard, carbonic anhydrase (AC) catalyzes the first part of the following reaction, in which carbon dioxide (CO2) in the presence of water (H ₂ O) is converted to carbonic acid (H2CO3), which at its Once it dissociates forming bicarbonate and carbonate ions depending on the pH:

CO ₂ + H ₂ O <-AC → H2CO3 <→ H ⁺ + HCO3 ^" <→ H ⁺ + CO ₃ ^2"

In turn, carbonate ions, in the presence of calcium ions resulting from the dissolution of calcium hydroxide, cause the precipitation of calcium carbonate according to the reaction: C0 ₃ ^{2 '} + Ca ²⁺ ^ CaC0 ₃

Carbonic anhydrase increases the dissolution rate of CO2 in water by several orders of magnitude. Each molecule of carbonic anhydrase can catalyze r 1, 4 x 10 ⁶ CO2 molecules per second (Yadavy col. 201 1, CurrentScience, 100, 520-524). Given its high effectiveness, carbon dioxide has found applications in CO2 sequestration in both solution and solid phase (Bond et al. 2001, Energy & Fuels, 15, 309-316; Mirjafariy col., 2007, Industrial EngineeringChemistryResearch 46, 921 -926; Fabre et al., 2009, Journal of Molecular Catalysis B: Enzymatic, 60, 163-170). In relation to the second aspect of the invention, the cement matrices based on carbide nanocals, said matrices also comprising water, pozzolans, aggregates and CO2, all of them obtained from industrial waste, obtained from the process of the present invention and the third aspect thereof, the prefabricated parts produced from the process of the invention, in any possible geometric form, as well as its use in construction, public works and urban furniture, the advantages of the materials obtained are due to the fact that they allow the use of recycled components with a very low carbon footprint, especially nanocals, mineralize dirty CO2 recovered from industrial process emissions, obtain high resistance at an early age never before reached in agglomerates with calcium hydroxide, avoid efflorescence by leaching or dispersion of calcium hydroxides, admit light and dry recycled aggregates duo pozzolanic and reduce thermal density and conductivity, which makes these products obtained with the process of the invention a paradigm of waste utilization and positive environmental action in the construction materials industry.

The accelerated air setting process of the invention allows the use of hydraulic and / or air limes, preferably carbide limes, as the only binding reagent in cementitious matrices for prefabricated parts, obtaining results comparable to or superior to cement prefabricated at similar setting times.

For this, the process of the invention includes the following steps: one . Mixing of the solid materials in concrete mixer, said materials consisting of cementitious matrices that include calcium hydroxide, from hydraulic limes and / or aerial limes, preferably limescale, as the only reactant agglomerating, and subsequently kneaded having been added to the fresh carbonic anhydrase mixture;

2. Dumping of the mixture thus obtained in prefabricated molds and, once sufficient hardness is reached, extraction of the mold piece and air drying until it is in equilibrium in an environment whose relative humidity does not exceed 85%; 3. Once hardened and pe rd id oelagual íq uida po rs eca do, preferably after seven days of air drying, introduction of the pieces in an autoclave which, once closed, is degassed by depression by vacuum to a maximum of - 760 mm Hg;

4. Injection into the steam autoclave (from distilled water) nebulized distilled water or a saturated aqueous solution of micronized calcium hydroxide, until the chamber is depressurized at - 500-200 mm Hg, preferably at -400— 300 mm Hg, in particular at -350 mm Hg;

5. CO2 injection into the autoclave until the pressure is 1 atm, the prefabricated parts remain inside until at least 50% and preferably at least 90% of the calcium hydroxide of the prefabricated parts has been transformed into calcium carbonate;

6. Total depressurization of the autoclave, discharge and storage of the finished parts. In a preferred embodiment of the process of the invention, the carbonic anhydrase of the first stage is added in concentrations ranging between 0.0001 and 0.1% by weight with respect to the total of the mixture, with particular preference between 0.001 and 0.01% by weight with respect to the total weight of the mixture. In another preferred embodiment of the process of the invention, the cementitious matrix that includes calcium hydroxide is that obtained as a residue in the Acetylene production, called in particular carbide lime in particular that purified and optimized as described in PCT / ES201 0/070294, of the same applicant.

Preferably, the relative humidity considered in step 2 does not exceed 85%; in particular it is 25% to 85% and particularly preferably it is maintained between 50% and 75%.

Preferably, the process temperature ranges between 10 and 50 ° C, in particular between 20 and 40 ° C.

Also in a preferred embodiment, the CO2 mentioned in step 5 of the present process is that recovered directly from the combustion gases of industrial processes, for example the coal thermoelectric, either the so-called "dirty CO2" or "CO2 clean "suitable for food use (purity> 95%).

The time necessary for the prefabricated parts to reach the total carbonation in the autoclave is a function of thickness, gas permeability, humidity, CO2 concentration and composition of the mixture of the pieces in addition to the characteristic properties of the lime used, where appropriate, of the other cementing compounds, pozzolanic materials, aggregates and additives. In the event that in addition to lime cement is used, the free calcium hydroxide thereof will also be carbonated contributing to the concrete reaching greater initial strengths.

The invention also provides various cementitious matrices that, regardless of whether they incorporate cement or not, comprise different materials dispersed in a lime matrix. In the presence of pozzolans, both cement and lime with hydraulic properties develop a greater production of aluminosilicate phases (hydrated calcium silicate phases and hydrated calcium aluminates) thus achieving the prefabricated elements greater mechanical performance. Aerial nanocals, due to their high reactivity, also develop hydraulic reactions in the presence of pozzolans. The invention shows as preferred examples a nanocal matrix commercially named GeoSilex obtained by purifying and optimizing the residues from carbide lime used in the Acetylene manufacturing, as described in patent application PCT / ES2010 / 070294. This matrix incorporates recycling pockets such as residual metacaolin from various industries, or residual fly ash from the thermoelectric industry. The preferred matrix object of the invention also includes recycling aggregates such as recycled glass powder, whether it is simply crushed or expanded in the form of hollow spheres.

In one embodiment, the matrix of the invention incorporates glass powder of a particle size between 10 and 50 μιτι, preferably recycled

In another embodiment, the matrix of the invention incorporates hollow glass spheres of a granulometry between 200 μιτι and 8 mm.

Since for its rapid carbonation the prefabricated elements of the invention may require a certain porosity, the process of the invention may also include the use of aerating additives and other additives typical of cryogenic concretes or cellular cements and concrete (cellular concrete) . Likewise, the cementitious matrix of the invention and the parts obtained therefrom and applying the method of this invention may also include the usual additives in the cement industry, such as plasticizers, water repellent, accelerators or setting retardants, as well as any of the heavy or light aggregates, the loads and the fibers or reinforcement materials usual in the concrete industry.

In an exemplary embodiment, the prefabricated material with the cementitious matrix and that prepared according to the process of the invention is characterized by the following properties:

• Light: Density <1, 5

· Low thermal conductivity: Landa <0.3

• Negative carbon footprint: CO2 eq <0 g / m3 of concrete

• Cement: 0 Kg / m3

• Cementing reagent: GeoSilex nanocal 100% recycled industrial waste

Pozzolanas: 100% obtained from industrial waste

• Aggregates: 100% recycled • Water: saturated with calcium idroxide, 1 00% obtained from industrial effluents

• Carbonation CO2: 100% recovered from industrial process emissions

In another exemplary embodiment, the cementitious matrix of the invention is obtained by applying the present process and from the following elements, the percentages expressed as percentages by weight:

• Binder reagent: 20% GeoSilex (50% solid), 100% recycled nanocal

• Water: 20% saturated water of Ca (OH) ₂

• Pozzolana: fly ash (5%)

• Arid 1: Glass powder (13%)

• Arid 2: Hollow glass spheres 0.5-1 mm (15%)

Fiberglass (5%)

• Carbonation accelerator: carbonic anhydrase (0.001%)

• CO2 recovered from industrial emissions (12%)

Claims

1. Aerial fragmentation procedure for obtaining prefabricated cements with cementitious matrices, including the following stages: i. Mixture of solid materials consisting of such materials in cementitious matrices that include calcium hydroxide, from hydraulic and / or aerial lime, and carbonic anhydrase and subsequent kneaded with water;

/ ^' / ^' . Dumping of the mixture thus obtained in prefabricated molds and, once a sufficient hardness has been reached, extraction of the mold piece and air drying until it is balanced in an environment whose relative humidity does not exceed 85%;

/ ^' / ^' / ^' . Once the relapses have been lost and the year is gone by drying, preferably after seven days of drying in the air, inserting the pieces in an autoclave and degassing by depression through vacuum to a maximum of -760 mm of Hg; iv. Water vapor injection from distilled water, nebulized distilled water or a saturated aqueous solution of micronized calcium hydroxide until the chamber is depressurized at -500 - (-200) mm Hg, v. Injection of CO ₂ into the autoclave until it depressurizes and reaches 760 mm Hg of internal pressure, the prefabricated parts remain inside until at least 50% of the calcium hydroxide of the prefabricated parts has been transformed into calcium carbonate ; saw. Depressurization of the autoclave, discharge and storage of finished parts.

2. Method according to claim 1, characterized in that the limes used are carbide limes derived from the manufacture of acetylene from calcium carbide, in particular paste nanocals obtained from the residues generated in the manufacture of acetylene.

Method according to claim 1, characterized in that the carbonic anhydrase of the first stage is added in concentrations between 0.0001 and 0.1% by weight with respect to the total weight of the mixture.

Method according to claim 3, characterized in that the carbonic anhydrase of the first stage is added in concentrations between 0.001 and 0.01% by weight with respect to the total weight of the mixture.

Method according to claim 1, characterized in that the relative humidity in step ii) is between 25% and 85%.

Method according to claim 5, characterized in that the relative humidity is between 50% and 75%.

Method according to claim 1, characterized in that in stage iv) the chamber is depressurized at -400 - (-300) mm Hg.

Method according to claim 7, characterized in that in stage iv) the chamber is depressurized at -350 mm Hg.

Method according to claim 1, characterized in that in step v) the pressure of 760 mm Hg is maintained by CO2 injection.

Method according to claim 1, characterized in that the CO2 of step v) is recovered from the combustion gases of industrial processes, being dirty CO2 or clean CO2 suitable for food use.

Method according to claim 1, characterized in that the prefabricated parts remain inside the autoclave until at least 90% of the calcium oxide of the prefabricated parts has been transformed into calcium carbonate.

Method according to claim 1, characterized in that it is carried out at a temperature between 10 and 50 ° C.

Method according to claim 12, characterized in that it is carried out at a temperature between 20 and 40 ° C.

Process according to claim 1, characterized in that the cementitious matrix incorporates recycling pockets as residual metacaolin of various units or centric residual flyers of the thermoelectric system.

15. Cementing matrix according to claim 1, which includes calcium hydroxide from hydraulic and / or aerial lime as the sole binding reagent.

16. Cementing matrix according to claim 15, characterized in that it also includes recycling aggregates in the form of recycled glass powder.

17. Cementing matrix according to claim 16, characterized in that it includes expanded glass powder in the form of hollow spheres.

18. Cementing matrix according to claim 16, characterized in that the glass powder has a granulometry between 10 and 50 μιτι.

19. Cementing matrix according to claim 17, characterized in that the hollow glass spheres have a granulometry between 200 μιτι and 8 mm.

20. Cementing matrix according to any one of claims 1 to 1 9, characterized in that it also includes aerating additives and other additives typical of concrete.

21. Cementing matrix according to any of claims 1 to 20, characterized in that it includes customary additives in the cement industry, such as plasticizers, fire retardants, accelerators or retarders of setting, as well as any of the heavy or light aggregates, usual loads and fibers or reinforcement materials in the concrete industry.

22. Prefabricated piece obtained by the application of the method according to claims 1 to 14, in any of its possible geometric shapes, for use in construction, public works and street furniture.

23. Prefabricated part according to claim 22, obtained from a cementitious matrix according to any of claims 15 to 21 for use in construction, public works and street furniture.

24. Use of a cementitious matrix according to claims 15 to 21 for obtaining prefabricated pieces intended for construction, public works and street furniture.