Hydrophobic recycled concrete aggregate, method for producing the same, and use of hydrophobic recycled concrete aggregate in cement-based compositions

Abstract

The present invention relates to a method for producing hydrophobic recycled concrete aggregate (RCA), which is recycled concrete aggregate (RCA) surface-modified with one or more silanizing agents selected from organosilanes, linear, branched, or cyclic organosiloxane oligomers, polyorganosiloxanes, or combinations thereof, and to the hydrophobic recycled concrete aggregate obtained by this method. The hydrophobic recycled concrete aggregate of the present invention is suitable as aggregate for cement-based compositions that exhibits a reduction in water demand compared to cement-based compositions containing untreated recycled concrete aggregate.

Description

[Technical Field]

[0001] This invention relates to a method for producing hydrophobic recycled concrete aggregate, hydrophobic recycled concrete aggregate obtained by this method, a cement-based composition containing hydrophobic recycled concrete aggregate, and the use of hydrophobic recycled concrete aggregate as a substitute for primary aggregate in a cement-based composition. [Background technology]

[0002] Construction waste (CDW) accounts for the majority of the world's total solid waste production, and most of it ends up in landfills. Therefore, from an environmental perspective, there is a strong need to make this type of waste recyclable.

[0003] On the other hand, natural aggregates (e.g., sand) commonly used in cement-based compositions such as concrete or mortar are typically non-renewable natural resources, and an increasing number of countries are pushing for regulations to reuse alternative materials instead of using natural aggregates.

[0004] One method of recycling CWD is to use it in the form of so-called recycled aggregate (RA) or recycled concrete aggregate (RCA) from construction waste as a substitute for natural aggregate (e.g., sand) in cement-based products such as concrete and mortar.

[0005] Recycled aggregate (RA) derived from construction waste can be obtained relatively easily by crushing the construction waste and, if necessary, sieving it into materials of a specified particle size. In this process, contaminants such as reinforcing bars or embedded components are removed from the construction waste before, during, or after production. Naturally, the resulting recycled aggregate will vary depending on the type of construction waste used.

[0006] Recycled concrete aggregate (RCA), obtained from construction waste, is mainly composed of old concrete or cement-based waste such as mortar. Therefore, RCA primarily uses natural aggregates and hydrated cement paste from cement-based waste as its base material.

[0007] Using RCA as a partial or complete substitute for natural aggregates (such as sand) in cement-based compositions (such as concrete or mortar) is an attractive approach from an environmental and economic standpoint.

[0008] However, using RCA as a substitute for natural aggregates in cement-based compositions presents significant challenges. In particular, using RCA in cement-based compositions results in a significantly increased water demand and makes shrinkage control more difficult compared to commonly used aggregates.

[0009] According to prior art, high-performance water-reducing agents are used to avoid increased water demand in cement-based compositions. Examples of commonly used high-performance water-reducing agents include lignosulfonates or polycarboxylic acid ethers. Another common method for reducing water demand in cement-based compositions is the addition of water-reducing agents of various chemical compositions. High-performance water-reducing agents or other water-reducing agents are generally added to fresh cement-based compositions (i.e., a mixture of mixing water and concrete) or mixing water. Water-repellent agents are also used to treat the surface of hardened concrete elements from the outside.

[0010] However, achieving a certain level of effectiveness requires large quantities of expensive chemical substances, such as high-performance water-reducing agents or other water-reducing agents, which can adversely affect other properties of the cement-based composition. Therefore, the methods of the prior art are unsatisfactory. Furthermore, the aforementioned additions necessitate additional work steps at the site, which complicates the processing of the cement-based composition. [Overview of the Initiative] [Problems that the invention aims to solve]

[0011] Therefore, an object of the present invention is to reduce or eliminate an increase in water demand that occurs when using recycled concrete aggregates as a partial or complete substitute for conventional aggregates such as sand in cementitious compositions such as concrete or mortar. Furthermore, the properties of the cementitious composition containing the recycled concrete aggregates should be equivalent to those of the cementitious composition prepared using natural aggregates such as sand, for example, with respect to shrinkage control. In addition, the complication of the treatment of the cementitious composition by additional working steps should also be avoided. **Means for Solving the Problems**

[0012] Surprisingly, it has been found that this object can be solved by providing a hydrophobic recycled concrete aggregate obtainable by treating the recycled concrete aggregate with a specific silanizing agent. Therefore, the above object is solved by providing a method for producing a hydrophobic recycled concrete aggregate and a hydrophobic recycled concrete aggregate obtained by such a method as described in claim 1.

[0013] Therefore, the present invention relates to a method for hydrophobizing recycled concrete aggregates (RCA), the method comprising: (i) preparing recycled concrete aggregates (RCA); (ii) applying a silanizing solution to the recycled concrete aggregates, the silanizing solution containing one or more silanizing agents selected from organosilanes, linear, branched or cyclic organosiloxane oligomers, polyorganosiloxanes, or combinations thereof; (iii) drying the recycled concrete aggregates treated with the silanizing solution, preferably at a temperature of 15 to 90 °C and including.

[0014] The hydrophobization of RCA is achieved by treatment with a silanizing solution. In other words, the silanizing agent acts as a hydrophobizing agent.

[0015] Surprisingly, it has been found that the hydrophobic recycled concrete aggregate obtained by the method of the present invention can be integrated without any problems into cement-based compositions such as mortar or concrete mixes. It has been shown that when other hydrophobic agents are used as modifiers for recycled concrete aggregate, aggregates that cannot be integrated into cement-based compositions are produced. Although we do not intend to be bound by any theory, it is thought that certain silanizing agents used according to the present invention do not completely waterproof the aggregate.

[0016] After treatment of RCA with silane solution, the water absorption rate decreases. The performance of cement-based compositions containing treated RCA improves, becoming closer to that of raw sand and other natural aggregates.

[0017] The specific advantages of this invention are as follows: - When hydrophobized according to the present invention, the performance of recycled concrete aggregate obtained from construction waste is improved, for example, the water absorption rate is reduced. - Compared to using untreated recycled concrete aggregate, the water consumption of the cement-based composition containing the hydrophobic recycled concrete aggregate according to the present invention is reduced, thereby reducing water consumption. - When hydrophobic recycled concrete aggregate is incorporated according to the present invention, the performance of the final cement-based composition such as concrete and mortar is improved. - Reduction in the amount of construction waste (CDW) disposed of in landfills. - Saving non-renewable resources, i.e., natural aggregates such as sand. - Saving energy required for the supply and transportation of natural aggregates, - Creation of a new and diverse range of products based on recycled aggregate.

[0018] Further aspects of the present invention are the subject of additional independent claims. Preferred embodiments are the subject of dependent claims. [Modes for carrying out the invention]

[0019] The present invention relates to a method for producing hydrophobic recycled concrete aggregate, wherein the method is (i) The step of preparing recycled concrete aggregate (RCA), (ii) A step of applying a silane solution to recycled concrete aggregate, wherein the silane solution comprises one or more silane agents selected from organosilanes, linear, branched or cyclic organosiloxane oligomers, polyorganosiloxanes, or combinations thereof, (iii) A step of drying the recycled concrete aggregate treated with the silane solution at a temperature of preferably 15 to 90°C. Includes.

[0020] Recycled concrete aggregate (RCA) is provided according to step (i) of the method of the invention. Recycled concrete aggregate (RCA) is obtained from construction waste (CDW). Various types of CDW exist depending on the origin of the waste and the degree of sorting or mixing. In particular, construction waste mainly consisting of cement-based waste such as concrete or mortar waste is usually used in the production of recycled concrete aggregate. Concrete or mortar waste is recovered, for example, from renovation work on bridges, sidewalks, roads, buildings and other structures.

[0021] In relation to the present invention, the term CDW refers to any construction material containing aggregate, and is not intended for its original purpose. CDW is particularly a residue, off-spec material, returned material, or demolition waste. In particular, CDW is demolition waste. CDW in relation to the present invention contains aggregate and at least one binder, but is not otherwise limited in composition.

[0022] According to a preferred embodiment, the CDW comprises at least one aggregate and at least one mineral hydraulic binder, preferably a hardened mineral binder. Examples of mineral hydraulic binders include cement, gypsum, lime, clay, latent hydraulic binders, pozzolanes, and geopolymers. The CDW may be a mixture of different materials. For example, the CDW may be concrete or mortar, a mixture of concrete and gypsum-based material, a mixture of concrete and plaster, a mixture of brick and mortar, or a mixture of brick, mortar, and plaster. However, it is preferable that the CDW does not contain large pieces of metal or wood. According to a particularly preferred embodiment, the CDW is waste concrete, especially waste concrete from demolition.

[0023] Construction waste is typically processed by crushing, removal of rebar, wood, plastic, glass, or other embedded materials, and optionally sieving, in order to obtain recycled concrete aggregate. The particle size of the recycled concrete aggregate can be controlled, for example, by the type, intensity, and duration of the crushing process. Optionally, a sieving step is added to obtain recycled concrete aggregate of a desired particle size. Removal of contaminants such as rebar, wood, plastic, glass, or other embedded materials can be carried out before, during, or after the crushing process. This removal can be carried out, for example, by magnets, washing, or density separation. Naturally, if the construction waste used does not contain unwanted contaminants, such removal is not necessary.

[0024] Recycled concrete aggregate (RCA) primarily consists of aggregates and hydrated cement paste derived from cement waste contained in recycled concrete waste (CDW). The amount of aggregates and hydrated cement paste from CDW, particularly cement waste, is typically at least 50 wt.%, preferably at least 75 wt.%, more preferably at least 90 wt.%, and can be up to 100 wt.%, based on the total weight of the recycled concrete aggregate. Examples of aggregates derived from CDW include sand, gravel, crushed stone, or slag. The hydrated cement paste derived from CDW may be derived from any type of cement or cement-based material commonly used.

[0025] In accordance with step (ii) of the method of the invention, a silanating solution is applied to the recycled concrete aggregate, wherein the silanating solution comprises one or more silanating agents selected from organosilanes, linear, branched or cyclic organosiloxane oligomers, polyorganosiloxanes, or combinations thereof.

[0026] Silanating agents selected from organosilanes, linear, branched, or cyclic organosiloxane oligomers, polyorganosiloxanes, or combinations thereof are generally organosilicon compounds comprising one or more silicon atoms, at least one organic group (preferably a substituted or unsubstituted alkyl group) bonded to the silicon atom, and at least one reactive group (selected from a hydroxyl group or a hydrolyzable group) bonded to the silicon atom. The substituted or unsubstituted alkyl group has 1 to 18 carbon atoms, preferably 1 to 8 carbon atoms. The hydrolyzable group is, for example, an alkoxy group, preferably an alkoxy group having 1 to 6 carbon atoms, preferably an alkoxy group having 1 or 2 carbon atoms, or an acyloxy group. The selected silanating agents are known compounds and are commercially available.

[0027] During hydrolysis, the hydrolyzable groups of silanizing agents can be converted to hydroxyl groups (silanol groups) bonded to silicon atoms, which are reactive with the chemical groups present on the surface of recycled concrete aggregate. As mentioned above, silanizing agents can also contain hydroxyl groups as reactive groups, in which case hydrolysis is unnecessary. While not intended to be bound by any theory, it is thought that treating recycled concrete aggregate with a silanizing solution modifies the surface of the recycled concrete aggregate by causing at least partial chemical bonding of the silanizing agent to the surface of the recycled concrete aggregate. However, alternatively or in addition to this, surface modification by silanizing agents may also result in a mere coating of the surface of the recycled concrete aggregate and / or filling of pores within the recycled concrete aggregate.

[0028] The mixture provides an active coating that prevents water absorption on the surface of recycled concrete aggregates. Whether the fundamental mechanism is due to a change in the surface tension of the aggregates or to the occlusion of pores remains unclear. In any case, surface modification with a silanizing agent improves the properties of recycled concrete aggregates, and as a result, the aggregates can be made to resemble the properties of natural aggregates as closely as possible, particularly with regard to water absorption.

[0029] In connection with the present invention, applying a silanizing agent to a particulate material, particularly recycled concrete aggregates, results in hydrophobization of the particulate material.

[0030] The silanizing agent is selected from organosilanes, linear, branched or cyclic organosiloxane oligomers, polyorganosiloxanes, or combinations thereof.

[0031] The organosilane is preferably an alkylsilane such as alkyltrialkoxysilane, preferably particularly of the general formula (I):

Chemical formula

[0032] Preferred examples of R 1 and R 2 of the alkylsilane having the general formula (I) are as follows: R 1 =CH3-, C2H5-, C3H7-, i-C3H7-, C4H9-, i-C4H9-, C6H 13 -, i-C6H 13 、C8H 16 -, or i-C8H 16 -, and R 2=H-, methyl group-, or ethyl group-.

[0033] Preferred examples of organosilanes include n-propyltrialkoxysilane, isopropyltrialkoxysilane, n-butyltrialkoxysilane, isobutyltrialkoxysilane, and octyltrialkoxysilane, where the alkoxy group preferably has 1 to 6 carbon atoms and more preferably is methoxy or ethoxy.

[0034] The linear, branched, or cyclic organosiloxane oligomers preferably have an average oligomerization degree in the range of 2 to 100, preferably 2 to 50, more preferably 2 to 30, and even more preferably 10 to 50 or 10 to 30, and these organosiloxane oligomers are preferably alkylsiloxane oligomers, and one or more alkyl groups of the alkylsiloxane oligomer may contain one or more substituents containing heteroatoms such as N, O, F, Cl, P, or S, for example, an amino group or a hydroxyl group. The average molecular weight of the linear, branched, or cyclic organosiloxane oligomers is preferably in the range of 300 to 10000 g / mol.

[0035] Such linear, branched, or cyclic organosiloxane oligomers are preferably silanes having general formula (IIa) and / or silanes having general formula (IIb): [ka] It can be obtained by hydrolysis and condensation reactions of one or more silanes selected from the above.

[0036] In the silane of general formula (IIa), R 3 These are independent of each other, C1~C 18 This represents alkyl, which may include one or more substituents containing heteroatoms such as N, O, F, Cl, P, or S, such as an amino group or a hydroxyl group, or an aryl group such as phenyl. 3 Preferred examples include CH3-, C2H5-, C3H7-, C4H9-, i-C4H9-, C6H13 -, i-C6H 13 C8H 16 -or i-C8H 16 - is

[0037] In the silane of general formula (IIb), R 4 C1~C 18 This represents alkyl, which may include one or more substituents containing heteroatoms such as N, O, F, Cl, P, or S, such as an amino group or a hydroxyl group, or an aryl group such as phenyl. 4 Preferred examples include CH3-, C2H5-, C3H7-, C4H9-, i-C4H9-, C6H 13 -, i-C6H 13 C8H 16 -or i-C8H 16 - is

[0038] In both silanes of general formula (IIa) and silanes of general formula (IIb), X is the same or different and represents a hydroxyl group or a hydrolyzable group, such as an alkoxy group having 1 to 6 carbon atoms, preferably 1 or 2 C atoms, or an acyloxy group such as an acetoxy group. Preferred examples of X are hydroxyl, methoxy, and ethoxy.

[0039] Some examples of silanes of general formula (IIa) are dimethyldimethoxysilane, dimethyldiethoxysilane, ethylmethyldimethoxysilane, ethylmethyldiethoxysilane, isobutylmethyldimethoxysilane, isobutylmethyldiethoxysilane, phenylethyldimethoxysilane, phenylethyldiethoxysilane, phenylmethyldimethoxysilane, phenylmethyldiethoxysilane, phenylmethoxydiethoxysilane, and phenylmethyldiacetoxysilane.

[0040] Examples of silanes of general formula (IIb) include methyltrimethoxysilane, methyltriethoxysilane, methyltri-n-propoxysilane, methyltri-i-propoxysilane, methyltri-n-butoxysilane, methyltri-i-butoxysilane, methyltri-sec-butoxysilane, methyltri-t-butoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltri-n-propoxysilane, ethyltri-i-propoxysilane, ethyltri-n-butoxysilane, and These are tiltri-i-butoxysilane, ethyltri-t-butoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, isopropyltrimethoxysilane, n-butyltrimethoxysilane, isobutyltrimethoxysilane, isobutyltriethoxysilane, pentyltrimethoxysilane, pentyltriethoxysilane, hexyltrimethoxysilane, n-octyltrimethoxysilane, n-octyltriethoxysilane, and isooctyltrimethoxysilane.

[0041] Polyorganosiloxanes are preferably of general formula (III): [ka] (In the formula, R 5 R represents an alkyl group having the same or different hydrogen atom or 1 to 6 carbon atoms, preferably 1 or 2 carbon atoms, and R is either the same or different. 6 R represents an alkyl group having the same or different hydrogen atoms or 1 to 6 carbon atoms, preferably 1 or 2 carbon atoms, and o is greater than 100, preferably greater than 100 and up to 5000, more preferably greater than 100 and up to 1000. 5 Preferred examples are H-, CH3-, and C2H5-. 6 Preferred examples are H-, CH3-, and C2H5. It has.

[0042] In preferred embodiments, the polyorganosiloxane, preferably a polyorganosiloxane of general formula (III), is a polydialkylsiloxane, particularly polydimethylsiloxane or polydiethylsiloxane, each having at least one or at least two terminal groups selected from hydroxyl and alkoxy, preferably methoxy or ethoxy.

[0043] The most significant reduction in water absorption rate of the hydrophobic recycled concrete aggregate obtained by the method of the present invention was achieved when the amount of silane agent was in the range of 10-15 wt.% based on the weight of the recycled concrete aggregate. However, such a large amount of silane agent may impair the ability to incorporate or integrate the hydrophobic recycled concrete aggregate into cement-based compositions, particularly admixtures with water. Furthermore, such a large amount of silane agent may lead to increased costs. To obtain a more improved water reduction effect, the amount of silane agent is preferably at least 0.5% by weight.

[0044] Therefore, the amount of silanizing agent applied to the recycled concrete aggregate using the silanizing solution is preferably in the range of 0.5 to 10 wt.%, more preferably 0.5 to 6 wt.%, and even more preferably 0.5 to 2 wt.%, based on the weight of the recycled concrete aggregate.

[0045] The silane solution contains one or more silane agents dissolved, emulsified, or dispersed in a solvent, preferably an emulsified solvent. The solvent may be at least one organic solvent, such as water and / or alcohol. The solvent is preferably water or a mixture of water and at least one organic solvent, such as alcohol.

[0046] For example, it may be advantageous to adjust the pH of the silane solution before application by adding a base to adjust the pH to >10, or by adding an acid to adjust the pH to <4. It is more preferable to adjust the pH to <4 by adding an acid.

[0047] Preferably, the silanation solution may be a solution, emulsion, or dispersion. The silanation solution is preferably an aqueous silanation solution. In a preferred embodiment, the silanation solution is an aqueous emulsion.

[0048] In certain embodiments, the silane solution preferably further comprises at least one emulsifier. The emulsifier is preferably selected from the following series: C8~C 18 -A series of alkyl sulfates having alkyl groups, with C8-C in the hydrophobic residue. 18 - Alkyl and alkyl and alkaryl ether sulfates having 1 to 40 ethylene oxide (EO) or propylene oxide (PO) units, C8-C 18 -Alkyl sulfonates containing alkyl, C8~C 18 -Alkyl sulfonates having alkyl groups, and half-esters of monohydric alcohols or alkylphenols containing 5 to 15 carbon atoms and sulfosuccinic acid, alkali metal and ammonium salts of carboxylic acids containing 8 to 20 carbon atoms in alkyl, aryl, alkaryl, or aralkyl residues, alkyl and alkaryl phosphates containing 8 to 20 carbon atoms in organic residues, alkyl ethers or alkaryl ether phosphates having 8 to 20 carbon atoms and 1 to 40 EO units in alkyl or alkaryl residues, 8 to 40 EO units and C8 to C in alkyl or aryl residues 22 Alkyl polyglycol ethers and alkaryl polyglycol ethers having carbon atoms, ethylene oxide / propylene oxide (EO / PO) block copolymers having 8 to 40 EO or PO units, C8 to C 22 Addition products of alkylamines having alkyl residues with ethylene oxide or propylene oxide, linear or branched saturated or unsaturated C8-C 24 A mixture of an alkyl polyglycoside having an alkyl residue, an oligoglycoside residue having 1 to 10 hexose or pentose units, a silicon-functional surfactant, or the above emulsifier.

[0049] The emulsifier content in the silane solution is preferably 0.01 to 5% by weight, based on the total weight of the emulsion.

[0050] The silane solution may further contain at least one hydrolysis catalyst or condensation catalyst. The hydrolysis catalyst or condensation catalyst can be selected from halides, oxides, hydroxides, imides, alkoxides, amides, thiolates, carboxylates and / or substituents thereof, elements of groups 3 and 4 of the periodic table (PSE), and elements of subgroups II, III, IV, V, VI, VII and Villa, Villb and VIIIc of PSE, particularly titanates or zirconates, such as complex compounds such as tetra-n-butyl orthotitanate or tetra-n-propyl orthozirconate. Further examples include oxides, hydroxides, hydrogen phosphates, hydrogen sulfates, sulfides, hydrogen sulfides, carbonates or bicarbonates and / or alkoxides of groups 1 and 2 of PSE, preferably sodium methanolate or sodium ethanolate and / or amino alcohols, preferably 2-aminoethanol or 2-(N,N-dimethyl)aminoethanol. Finally, carboxylic acids such as formic acid, acetic acid, or propionic acid, as well as mineral acids such as hydrochloric acid or phosphoric acid, can also be used as hydrolysis or condensation catalysts.

[0051] Furthermore, the silane solution may contain one or more conventional additives such as inorganic or organic acids, buffering substances, fungicides, bactericides, algaecides, microcides, deodorants, rust inhibitors, preservatives, and rheological additives.

[0052] Advantageously, the silane solution, especially in emulsion form, can be further diluted with water before use. In principle, any type of water is suitable, such as deionized water, drinking water, wastewater, or seawater. A diluent usable according to the present invention comprises 1 part of the silane solution and 0 to 99 parts of water, preferably 1 part of the silane solution and 0.1 to 49 parts of water, more preferably 1 part of the silane solution and 1 to 9 parts of water. Here, "parts" means parts by weight.

[0053] The silanating agent content in the silanating solution applied to the RCA can vary widely, from 0.5 to 99.5% by weight, preferably 2 to 90% by weight, based on the total weight of the silanating solution. However, it is preferable to apply a considerably diluted form of the silanating solution to help ensure a uniform distribution of the silanating agent in the aggregate. In a preferred embodiment, the applied silanating solution contains 3 to 60 wt.%, preferably 5 to 20 wt.%, of one or more silanating agents based on the total weight of the silanating solution.

[0054] According to step (ii) of this method, the silanation solution is applied to the recycled concrete aggregate. The application can be carried out by spraying or pouring the silanation solution onto the recycled concrete aggregate, preferably by spraying. Pouring can be done by adding the silanation solution dropwise onto the recycled concrete aggregate.

[0055] According to a preferred embodiment, the application of the silanation solution to the recycled concrete aggregate is thought to be facilitated by mixing the obtained silanation solution with the recycled concrete aggregate material.

[0056] Mixing can be carried out in a mixing unit, or simply by manually stirring the resulting material of silane solution and recycled concrete aggregate with a stirring element. Suitable mixing units are internal mixers such as Lödige mixers, Hobart mixers, conical mixers, stirring tanks, kneaders, or mixers. A suitable mixing unit is advantageous in that it does not decompose the hydrophobic recycled concrete aggregate into smaller particles during the mixing process. A mixing time of 30 seconds to 5 minutes, for example, 1 to 2 minutes, may be sufficient.

[0057] Therefore, in a preferred embodiment, the silanation solution is applied to the recycled concrete aggregate by spraying or pouring the silanation solution onto the recycled concrete aggregate and mixing the resulting silanation solution with the recycled concrete aggregate material.

[0058] As described above, in a preferred embodiment of the method according to the present invention, the amount of silanizing agent applied by the silanizing solution is in the range of 0.5 to 10 wt.%, preferably 0.5 to 6 wt.%, and more preferably 0.5 to 2 wt.%, based on the weight of the recycled concrete aggregate.

[0059] According to step (iii) of the method of the present invention, the recycled concrete aggregate treated with the silane solution is dried.

[0060] Drying can be carried out at temperatures such as 15-90°C, preferably 20-80°C, and more preferably 30-50°C. From the viewpoint of energy and cost saving, drying at low temperatures, and even at room temperature or slightly higher temperatures, is preferable. Naturally, the drying time also depends on the drying temperature used. When using higher temperatures, drying can be carried out in, for example, 0.5-2 hours, but drying at low temperatures such as 30-50°C may require, for example, 12-48 hours, or even 24 hours.

[0061] The present invention also relates to hydrophobic recycled concrete aggregate (RCA) obtained by the method according to the present invention described above.

[0062] All aspects, proportions, and embodiments described above regarding the method of the present invention, particularly with respect to the silanation solution, silanation agent, and recycled concrete aggregate, also apply to the hydrophobic recycled concrete aggregate (RCA) of the present invention, and therefore will be referred to accordingly.

[0063] As described above, the hydrophobic recycled concrete aggregate of the present invention may be recycled concrete aggregate (RCA) surface-modified with one or more silanizing agents selected from organosilanes, linear, branched or cyclic organosiloxane oligomers, polyorganosiloxanes, or combinations thereof, wherein the surface modification includes chemical bonding of the silanizing agent to the surface of the recycled concrete aggregate, and / or physical coating of the recycled concrete aggregate with the silanizing agent, and / or filling of pores in the recycled concrete aggregate with the silanizing agent.

[0064] In a preferred embodiment, the amount of silane agent present in the hydrophobic RCA is preferably in the range of 0.5 to 10 wt.%, more preferably 0.5 to 6 wt.%, and even more preferably 0.5 to 2 wt.%, based on the weight of the recycled concrete aggregate.

[0065] In preferred embodiments, the hydrophobic recycled concrete aggregate of the present invention has a particle size of 40 mm or less, preferably 20 mm or less, more preferably 10 mm or less, and most preferably 4 mm or less. The hydrophobic recycled concrete aggregate may have a particle size of at least 0.001 mm, for example, at least 0.063 mm, for example, at least 0.125 mm, but separation of very fine particles is usually not required. Particle size can be analyzed by sieve analysis, for example, as described in EN12192-1:2002 or EN933-1:2012. For particles with a particle size of less than 75 μm, the wet method of EN933-1:2012 is used.

[0066] The present invention further relates to a cement-based composition comprising: a) A cement-based binder, preferably a Portland cement such as Ordinary Portland Cement (OPC), and b) Hydrophobic recycled concrete aggregate according to the present invention as described above.

[0067] The cement-based composition is preferably mortar or concrete.

[0068] Since we have discussed hydrophobic recycled concrete aggregate according to the present invention, we will also refer to that.

[0069] The cement-based binder is preferably cement, particularly Portland cement such as Ordinary Portland Cement (OPC). A suitable OPC is, for example, classified as CEM I under standard DIN 197-1. However, other OPCs classified under relevant ASTM, JIS, or Chinese standards are also suitable. Furthermore, instead of OPC, blended cements such as Portland composite cement (CEM II), blast furnace cement (CEM III), pozzolanic cement (CEM IV), and composite cement (CEM V) conforming to DIN 197-1 can also be used as the cement-based binder. In addition to OPC, special cements such as calcium sulfoaluminate cement, calcium aluminate cement, or mixtures thereof can also be used.

[0070] The cement-based binder of the cement-based composition of the present invention may include a latent hydraulic binder and / or a pozzolanic binder. Suitable latent hydraulic binders and / or pozzolanic binders are, in particular, granulated blast furnace slag, calcined clay, fly ash, silica fume and / or microsilica.

[0071] The cement-based composition may be a dry, wet, or hardened cement-based composition. A dry cement-based composition typically has a water content of 10 wt.% or less, preferably 3 wt.% or less, and particularly 1 wt.% or less, relative to the total weight of the dry cement-based composition. A dry cement-based composition is usually a powdered cement-based composition.

[0072] A wet cement-based composition refers to a cement-based composition that has been mixed with water (dried) to obtain a fresh cement-based composition. The weight mixing ratio of water to the cement-based composition is, for example, 0.1 to 1.0, preferably 0.2 to 0.6. After the wet cement-based composition hardens, a hardened cement-based composition is obtained.

[0073] Apart from the hydrophobic recycled concrete aggregate according to the present invention, the cement-based composition may or may not contain conventional aggregates different from the hydrophobic recycled concrete aggregate of the present invention, such as sand. In other words, in the cement-based composition, the primary aggregate commonly used may be completely or partially replaced with the hydrophobic recycled concrete aggregate.

[0074] The cement-based composition of the present invention may contain one or more additives commonly used in the mortar and / or concrete industry, such as plasticizers and / or superplasticizers, redispersible polymers, accelerators, retarders, air-entraining agents, stabilizers, viscosity modifiers, thickeners, accelerators, retarders, waterproofing agents, strength-enhancing additives, foaming agents, pigments, and rust inhibitors.

[0075] In a preferred embodiment, the cement-based composition according to the present invention comprises the following, based on the dry weight of the cement-based composition: a) 10-40 wt.%, preferably 20-30 wt.%, of a cement-based binder, preferably Portland cement, and b) Hydrophobic recycled concrete aggregate in an amount of 50-80 wt.%, preferably 60-70 wt.%.

[0076] Those skilled in the art are familiar with methods, processes, and apparatus for mixing dry cement-based compositions with water.

[0077] The successful integration of hydrophobic recycled concrete aggregate into cement-based compositions positively impacts the workability of newly produced concrete. Workability is evaluated by measuring how flowable the concrete is, which can be measured, for example, by a concrete slump test in accordance with UNE EN 83258:2005, and this slump test also indicates the water requirements of the composition.

[0078] The particular advantages of hydrophobic recycled concrete aggregate are that it reduces the water absorption of recycled concrete aggregate and, at the same time, allows the hydrophobic recycled concrete aggregate to integrate well with cement-based compositions.

[0079] Furthermore, the present invention relates to the use of hydrophobic recycled concrete aggregate according to the present invention as a substitute for primary aggregate in a cement-based composition. The cement-based composition is preferably mortar or concrete.

[0080] By using hydrophobic recycled concrete aggregate in cement-based compositions, the consumption of natural primary concrete aggregates such as sand can be reduced. This saves resources and reduces costs without significantly affecting the material properties of the cement-based composition.

[0081] The use according to the present invention is particularly suitable for reducing the water demand in the cement-based composition compared to using non-hydrophobized recycled concrete aggregate in the same cement-based composition.

[0082] Using hydrophobic recycled concrete aggregate in cement-based compositions not only reduces the consumption of fresh concrete aggregate but also reduces water consumption. This contributes to environmental protection, especially when considering changes in climate conditions.

[0083] The following embodiments provide further embodiments of the present invention to those skilled in the art. [Examples]

[0084] The materials used are outlined below.

[0085] [Table 1]

[0086] Examples 1-6 - Preparation of hydrophobic RCA For application, silane solutions SIL1 and SIL2 were each diluted with water to obtain emulsions containing 10% by weight of silane based on the total weight of the silane solutions. Based on the weight of the RCA, the diluted silane solutions were applied to the RCA in amounts of 1% by weight, 5% by weight, and 10% by weight, respectively, as shown in Table 1 below. After applying the diluted silane solutions SIL1 and SIL2 to the RCA by spraying or dripping, the resulting materials were mixed. Mixing was carried out in a Hobart mixer for 60 seconds. After mixing, the materials were dried at 23°C for 24 hours to obtain hydrophobic recycled concrete aggregate. In some cases, application by dripping, for example, of the silane solutions may be advantageous in that it is easier to scale up.

[0087] The water absorption rate of the prepared hydrophobic recycled concrete aggregate was measured according to UNE EN 1097-6. ​​For reference, the water absorption rate of RCA that had not been treated with silane solution was also measured. The results are shown in Table 1.

[0088] [Table 2]

[0089] Examples 7 and 8 and Reference Examples 1 and 2 - Preparation of Mortar 1:3 mortar was prepared by adding 1 part cement (by weight) to 3 parts aggregate. 450g of cement was used. The mortar was then mixed with water. The actual w / c ratio was 0.58 (w / c is the weight ratio of water to cement).

[0090] The aggregate used in Reference Example 1 is ordinary commercially available sand with a particle size of 0-4 mm that has not undergone any treatment.

[0091] The aggregate used in Example 7 was hydrophobized RCA prepared in Example 2 (RCA surface-treated with SL1, amount of silane agent: 5 wt.%) based on the weight of the RCA.

[0092] The aggregate used in Example 8 was hydrophobized RCA prepared in Example 5 (RCA surface-treated with SL2, amount of silane agent: 5 wt.%) based on the weight of the RCA.

[0093] The aggregate used in Reference Example 2 is RCA (untreated).

[0094] A slump test was conducted to measure the consistency of the fresh mortar according to UNE EN 83258:2005, which indicates the water requirements of the mortar.

[0095] Table 2 summarizes the details of the test and the results of the slump test.

[0096] [Table 3]

[0097] Examples 7 and 8 demonstrate that the hydrophobic RCA is well integrated into the mortar. The water requirements in Examples 7 and 8 are reduced compared to Reference Example 2.

[0098] The hardened mortar of Example 8 was visually inspected using a scanning electron microscope (SEM). The photograph shows moderate cement crystallization (CSH gel), demonstrating that the hydrophobic RCA did not affect cement crystallization and was properly integrated into the cementitious matrix.

[0099] Reference Example 3 Mortar test specimens measuring 40 × 40 × 160 mm were prepared using fresh mortar in the same manner as in Reference Example 1, i.e., using untreated sand as aggregate.

[0100] Example 9 A full-scale mortar test specimen measuring 40 × 40 × 160 mm was prepared in the same manner as in Example 8, that is, using RCA hydrophobized with SL2 as aggregate, in fresh mortar.

[0101] Porosity testing of specimens from Reference Example 3 and Reference Example 9 The porosity was measured for three sections (sections 1, 2, and 3) of each mortar test specimen measuring 40 × 40 × 160 mm in full size, according to Reference Example 3 and Example 9. The porosity was measured by mercury intrusion porosimetry in accordance with ASTM D4404.

[0102] Porosity has three pore size ranges, namely: PS1 Pore diameter<0.001mm 3 PS2 Pore diameter=0.001~0.09mm 3 PS3 Pore diameter>0.09mm 3 Each was measured individually.

[0103] For each of these pore size ranges, the amount and volume of pores present were measured. The results of the porosity tests are summarized in Table 3.

[0104] [Table 4]

[0105] In Reference Example 3, superior porosity is achieved when the pore size is <0.001 mm. 3 (PS1, quantity) is observed. When the volume is quantified, the pore size > 0.09 mm 3 Despite the small number of pores containing (PS3), the total volume occupied by these pores is large.

[0106] In Example 9, a change in the pore formation tendency is observed. While we do not intend to be bound by any theory, this is thought to be directly related to the surface tension modified by the presence of the SIL2 coating on the RCA particles.

Claims

1. A method for producing hydrophobic recycled concrete aggregate, (i) A step of preparing recycled concrete aggregate (RCA), (ii) A step of applying a silane solution to the recycled concrete aggregate, wherein the silane solution comprises one or more silane agents selected from organosilanes, linear, branched or cyclic organosiloxane oligomers, polyorganosiloxanes, or combinations thereof, (iii) The step of drying the recycled concrete aggregate treated with the silane solution, preferably at a temperature of 15 to 90°C. A method that includes this.

2. The method according to claim 1, wherein the silane solution is an aqueous silane solution, preferably an aqueous solution, an aqueous dispersion, or an aqueous emulsion.

3. The method according to claim 1 or 2, wherein the silane solution to be applied contains 3 to 60 wt.%, preferably 5 to 20 wt.%, of the one or more silane agents based on the total weight of the silane solution.

4. The method according to any one of claims 1 to 3, wherein the silane agent is applied in an amount ranging from 0.5 to 10 wt.%, preferably 0.5 to 6 wt.%, and more preferably 0.5 to 2 wt.%, based on the weight of the recycled concrete aggregate.

5. The method according to any one of claims 1 to 4, wherein the silane solution is sprayed or poured onto the recycled concrete aggregate, and the silane solution is applied to the recycled concrete aggregate by mixing the obtained silane solution with the recycled concrete aggregate material.

6. The organosilane is an alkylsilane, preferably of general formula (I): 【Chemistry 1】 (In the formula, R １ C １ ~C １８ Alkyl, preferably C ３ ~C ８ It is alkyl, R ２ (These are either the same or different atoms, and are either hydrogen atoms or alkyl groups having 1 to 6 carbon atoms, preferably 1 or 2 carbon atoms.) It is an alkylsilane having, The linear, branched, or cyclic organosiloxane oligomer has an average degree of oligomerization in the range of 2 to 100, preferably 2 to 50, more preferably 2 to 30, the organosiloxane oligomer is preferably an alkylsiloxane oligomer, and one or more alkyl groups of the alkylsiloxane oligomer may contain one or more substituents including heteroatoms such as N, O, F, Cl, P, or S, and / or The aforementioned polyorganosiloxane has the general formula (III): 【Chemistry 2】 (In the formula, R ５ R represents an alkyl group that is the same or different, and has a hydrogen atom or 1 to 6 carbon atoms, preferably 1 or 2 carbon atoms. ６ (where is the same or different and represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, preferably 1 or 2 carbon atoms; where o is greater than 100, preferably greater than 100 and up to 5000, more preferably greater than 100 and up to 1000) The method according to any one of claims 1 to 5, comprising:

7. Hydrophobic recycled concrete aggregate (RCA) obtained by the method described in any one of claims 1 to 6.

8. The hydrophobic recycled concrete aggregate according to claim 7, wherein the amount of silane agent present is in the range of 0.5 to 10 wt.%, preferably 0.5 to 6 wt.%, and more preferably 0.5 to 2 wt.%, based on the weight of the recycled concrete aggregate.

9. The hydrophobic recycled concrete aggregate according to claim 7 or 8, wherein the hydrophobic recycled concrete aggregate has a particle size of 40 mm or less, preferably 20 mm or less, more preferably 10 mm or less, and most preferably 4 mm or less.

10. a) A cement-based binder, preferably Portland cement, b) Hydrophobic recycled concrete aggregate according to any one of claims 7 to 9 A cement-based composition containing, A cement-based composition wherein the cement-based composition is preferably mortar or concrete.

11. Based on the dry weight of the cement-based composition, a) 10 to 40 wt.%, preferably 20 to 30 wt.%, of the cement-based binder, preferably Portland cement, b) 50 to 80 wt.%, preferably 60 to 70 wt.%, of the hydrophobic recycled concrete aggregate and A cement-based composition according to claim 10, comprising:

12. Use of hydrophobic recycled concrete aggregate according to any one of claims 7 to 9 for replacing primary aggregate in cement-based compositions, preferably mortar or concrete.

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