Modified recycled coarse aggregate concrete and preparation method thereof

Abstract

The invention relates to modified recycled coarse aggregate concrete and a preparation method thereof. The modified recycled coarse aggregate concrete is prepared from the following raw material components in parts by mass: 300 to 450 parts of cement, 30 to 50 parts of zeolite powder, 150 to 300 parts of sodium silicate modified red brick powder, 15 to 50 parts of sodium hydroxide, 750 to 900 parts of machine-made sand, 850 to 1000 parts of modified recycled coarse aggregate and 150 to 200 parts of water, a preparation process of the modified recycled coarse aggregate comprises the following steps: calcining the recycled coarse aggregate, and cooling to obtain the modified recycled coarse aggregate. Compared with the prior art, the recycled coarse aggregate has high strength and can be effectively applied to high-strength and high-performance concrete, and the high-strength modified recycled coarse aggregate concrete is obtained.

Description

Technical Field

[0001] The invention relates to the technical field of concrete, and in particular to a modified recycled coarse aggregate concrete and a preparation method thereof. Background Art

[0002] The application of recycled aggregate concrete in the construction field has achieved certain results. It is widely used in the construction of foundations, columns, beams, slabs and other components of various buildings, and its strength and durability can meet the requirements of general construction projects. Although recycled aggregate concrete has achieved certain results in application, it still faces some challenges. The poor quality stability of recycled aggregate is a major problem. Because the surface of recycled aggregate is attached with waste cement stone, mortar, etc., its apparent density and bulk density are both lower than those of natural aggregate, and the old cement stone and mortar on the surface will crack, resulting in large crushing index and water absorption rate. At the same time, the defects caused by insufficient bonding between the surface of recycled aggregate and cementitious materials make it impossible to use it to prepare high-strength concrete. These problems affect the compressive strength and durability of recycled concrete. Therefore, if recycled aggregate can be applied to high-strength and high-performance concrete and can meet the relevant performance requirements, it will greatly expand the application of recycled aggregate in concrete.

[0004] Patent publication number CN115650688A discloses an assembled aerated concrete board and method prepared using recycled concrete aggregate. However, in this method, organic matter in the recycled concrete aggregate is treated by microwave sintering, and the decomposition of the recycled aggregate is not involved. In addition, the treated recycled concrete aggregate particles and red brick particles are used as aggregates in aerated concrete. These two types of particles have a small density and are not prone to floating or sinking during the preparation of aerated concrete, which helps to reduce the shrinkage of alkali-activated aerated concrete rather than promote alkali activation. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a modified recycled coarse aggregate concrete and a preparation method thereof, so that the recycled coarse aggregate has higher strength and can be effectively applied to high-strength and high-performance concrete to obtain high-strength modified recycled coarse aggregate concrete.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] In one aspect, the present invention provides a modified recycled coarse aggregate concrete, comprising the following raw material components by weight: 300-450 parts of cement, 30-50 parts of zeolite powder, sodium silicate (Na 2 SiO 3) 150-300 parts of modified red brick powder, 15-50 parts of sodium hydroxide (NaOH), 750-900 parts of machine-made sand, 850-1000 parts of modified recycled coarse aggregate, and 150-200 parts of water;

[0008] The preparation process of the modified recycled coarse aggregate is as follows: the recycled coarse aggregate is calcined and cooled to obtain the modified recycled coarse aggregate, so that the surface and the interior of the modified recycled coarse aggregate contain a large amount of calcium carbonate (CaCO 3 ), calcium hydroxide (Ca(OH) 2 ) decomposed into calcium oxide (CaO).

[0009] Furthermore, the calcination temperature is 1100-1100° C., and the calcination time is 2-4 hours.

[0010] Furthermore, the particle size of the modified recycled coarse aggregate is 5 to 25 mm.

[0011] Furthermore, the Na 2 SiO 3 The modified red brick powder is modified before use. The modification process is as follows: the red brick powder is placed in Na 2 SiO 3 The modified red brick powder is soaked in a solution and dried after soaking to obtain a modified red brick powder, wherein the modified red brick powder contains sodium silicate.

[0012] Furthermore, the drying is air-drying.

[0013] Furthermore, the composition of the red brick powder includes, by mass percentage: silicon dioxide (SiO 2 ) content 55%-60%, calcium dioxide (CaO 2 ) content 15%-25%, iron oxide (FeO) content 5%-10%, iron oxide (Fe 2 O 3 ) content 0-5%, aluminum oxide (Al 2 O 3 ) content 0-5%;

[0014] When the Fe 2 O 3 When the content is 0, it means that the red brick powder does not contain Fe 2 O 3 , when the Al 2 O 3 When the content is 0, it means that the red brick powder does not contain Al 2 O 3 .

[0015] Furthermore, the average particle size of the red brick powder is 20-50 μm.

[0016] Furthermore, the red brick powder is obtained by crushing and grinding red bricks from demolished old buildings into powder, and has a large number of nano-scale pores and irregular particle shapes.

[0017] Furthermore, the Na 2 SiO 3 The mass concentration of the solution is 20wt%-40wt%, the red brick powder is completely immersed in the sodium silicate solution, and the immersion time is 2-10 hours, preferably 3-6 hours.

[0018] Furthermore, the zeolite powder includes natural zeolite powder or synthetic zeolite powder, which is loosely agglomerated, has a large number of nano-scale pores, and has an irregular particle shape, and has the ability to absorb and solidify carbon dioxide (CO 2 )’s role.

[0019] Furthermore, the machine-made sand is medium-coarse sand, and its fineness modulus is 2.1 to 3.0.

[0020] Furthermore, the purity of the NaOH is 99% to 99.99%.

[0021] In another aspect, the present invention also provides a method for preparing modified recycled coarse aggregate concrete, comprising the following steps:

[0022] calcining the recycled coarse aggregate and obtaining modified recycled coarse aggregate after cooling;

[0023] Mix water and NaOH to obtain a sodium NaOH solution;

[0024] Modified recycled coarse aggregate, machine-made sand, zeolite powder, Na 2 SiO 3 The modified red brick powder and cement are mixed and stirred, and the sodium hydroxide solution is added and stirred evenly to obtain the modified recycled coarse aggregate concrete.

[0025] Furthermore, water and NaOH are mixed and stirred uniformly, and then cooled to obtain a sodium hydroxide solution.

[0026] Furthermore, the modified recycled coarse aggregate, machine-made sand, zeolite powder, red brick powder and cement are mixed and stirred for 10 to 60 seconds, the NaOH solution is added and stirred for 60 to 120 seconds to obtain modified recycled coarse aggregate concrete.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] (1) The present invention calcines the recycled coarse aggregate to obtain modified recycled coarse aggregate, so that the CaCO in the recycled aggregate 3 , Ca(OH) 2 Can decompose to produce CaO; put red brick powder in Na 2 SiO3 Soak in solution to obtain Na 2 SiO 3 Modified red brick powder, Na 2 SiO 3 After being released in the red brick powder, it not only solidifies the recycled aggregate, but also acts as an alkali activator, causing the red brick powder and CaO wrapped on the surface and inside of the modified recycled coarse aggregate to solidify in the Na 2 SiO 3 Under the stimulation of NaOH, alkali-activated cementitious materials are formed, which improves the bonding force between the surface of recycled coarse aggregate and the alkali-activated cementitious materials, thereby greatly weakening the defects caused by insufficient bonding between the surface of recycled coarse aggregate and the alkali-activated cementitious materials, thereby providing support for modified recycled coarse aggregate concrete.

[0029] (2) For ordinary recycled coarse aggregate concrete, due to the presence of hardened mortar and a large number of interface structures on the surface of the recycled coarse aggregate, its compressive strength is lower than that of ordinary concrete. The present invention calcines the recycled coarse aggregate at 600-1100°C to obtain modified recycled coarse aggregate, so that the Ca(OH) 2 Can decompose to produce CaO.

[0030] (3) The present invention utilizes Na 2 SiO 3 The red brick powder was soaked and modified to obtain Na 2 SiO 3 Modified red brick powder, red brick powder has a large number of nearly spherical micropores, which can transfer Na 2 SiO 3 After the red brick powder is dried, sodium silicate can be effectively retained in the micropores. 2 SiO 3 After the modified red brick powder is used in recycled coarse aggregate concrete, it will be able to release Na 2 SiO 3 The recycled coarse aggregate is chemically cured and modified to weaken the defect that the strength of the recycled coarse aggregate cannot be increased due to its own characteristic defects.

[0031] (4) Since the modified red brick powder is a low-calcium and high-silicon alkali-activated raw material, adjusting the amount of modified recycled coarse aggregate and modified red brick powder can effectively adjust the overall calcium oxide content in the modified red brick powder, thereby obtaining the optimal Ca / Si ratio, so that CaO is at the Na 2 SiO 3 Under the action of NaOH, the alkali-activated reaction is promoted, the strength of the alkali-activated cementitious material is improved, and then the strength of the modified recycled coarse aggregate concrete is improved.

[0032] (5) Zeolite powder itself contains porous inorganic internal curing agent. Zeolite powder also has two adsorption characteristics: selective adsorption and efficient adsorption. It can effectively adsorb CO 2 The present invention uses zeolite powder, when CO in the air 2 When low carbon concrete is corroded, the zeolite powder inside the modified recycled coarse aggregate will be able to absorb CO 2 In addition, when the zeolite powder cannot absorb the excess CO 2 When CO 2 It will react with calcium hydroxide in the residual cement slurry on the surface of the modified recycled coarse aggregate to produce calcium carbonate, which will block more microporous defects on the surface of the modified recycled coarse aggregate and alleviate the problem that the strength of the modified recycled coarse aggregate concrete cannot be improved due to the defects of the modified recycled coarse aggregate.

[0033] (6) The present invention organically combines the characteristics of the recycled coarse aggregate itself, Na 2 SiO 3 Characteristics of modified red brick powder, modified recycled coarse aggregate and Na 2 SiO 3 The combination of modified red brick powder and zeolite powder makes the modified recycled coarse aggregate have a large amount of CaCO inside and on the surface. 3 , Ca(OH) 2 Calcination and decomposition to obtain CaO can make the modified recycled coarse aggregate provide CaO for part of the red brick powder and in Na 2 SiO 3 Na provided by modified red brick powder 2 SiO 3 and the addition of NaOH promotes alkali excitation; in addition, the Na in the modified red brick powder 2 SiO 3 The surface of recycled coarse aggregate can be chemically cured and modified; finally, the CO absorbed by zeolite powder 2 Ca(OH) 2 The reaction fills the holes on the surface of the modified recycled coarse aggregate; under the combined action of the three effects, the strength of the modified recycled coarse aggregate concrete can be greatly and effectively improved.

[0034] (7) The present invention organically combines and utilizes the physical and chemical properties of construction waste, and can effectively solve the problem of poor strength of recycled coarse aggregate concrete caused by defects in the properties of the recycled aggregate itself. DETAILED DESCRIPTION

[0035] The present invention is described in detail below in conjunction with specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and a detailed implementation method and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiments. Based on the given embodiments, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0036] Unless otherwise specified, the reagents, methods, instruments and equipment used in the present invention are conventional reagents, methods, instruments and equipment in the art.

[0037] A modified recycled coarse aggregate concrete comprises the following raw material components by weight: 300-450 parts of cement, 30-50 parts of zeolite powder, 2 SiO 3 150-300 parts of modified red brick powder, 15-50 parts of NaOH, 750-900 parts of machine-made sand, 850-1000 parts of modified recycled coarse aggregate, 150-200 parts of water;

[0038] The preparation process of the modified recycled coarse aggregate is as follows: the recycled coarse aggregate is calcined and cooled to obtain the modified recycled coarse aggregate, so that the surface and the interior of the modified recycled coarse aggregate contain a large amount of CaCO 3 , Ca(OH) 2 Decomposed CaO substance.

[0039] In some specific embodiments, the calcination temperature is 1100-1100° C., and the calcination time is 2-4 hours.

[0040] In some specific embodiments, the particle size of the modified recycled coarse aggregate is 5 to 25 mm.

[0041] In some specific embodiments, the Na 2 SiO 3 The modified red brick powder is modified before use. The modification process is as follows: the red brick powder is placed in Na 2 SiO 3 The modified red brick powder is soaked in a solution and dried after soaking to obtain a modified red brick powder, wherein the modified red brick powder contains sodium silicate.

[0042] In some specific embodiments, the drying is air-drying.

[0043] In some specific embodiments, the composition of the red brick powder includes, by mass percentage: SiO 2 Content 55%-60%, CaO 2 Content 15%-25%, FeO content 5%-10%, Fe 2 O 3 Content 0-5%, Al2 O 3 Content 0-5%;

[0044] When the Fe 2 O 3 When the content is 0, it means that the red brick powder does not contain Fe 2 O 3 , when the Al 2 O 3 When the content is 0, it means that the red brick powder does not contain Al 2 O 3 .

[0045] In some specific implementations, the average particle size of the red brick powder is 20-50 μm.

[0046] In some specific implementations, the red brick powder is obtained by crushing and grinding red bricks from demolished old buildings into powder, and has a large number of nano-scale pores and irregular particle shapes.

[0047] In some specific embodiments, the Na 2 SiO 3 The mass concentration of the solution is 20wt%-40wt%, the red brick powder is completely immersed in the sodium silicate solution, and the immersion time is 2-10 hours.

[0048] In some specific embodiments, the zeolite powder includes natural zeolite powder or synthetic zeolite powder, which is loosely agglomerated and has a large number of nano-scale pores and irregular particle shapes, and has the ability to absorb and solidify CO. 2 role.

[0049] In some specific implementations, the machine-made sand is medium-coarse sand, and its fineness modulus is 2.1-3.0.

[0050] In some specific embodiments, the purity of the NaOH is 99% to 99.99%.

[0051] A method for preparing modified recycled coarse aggregate concrete comprises the following steps:

[0052] calcining the recycled coarse aggregate and obtaining modified recycled coarse aggregate after cooling;

[0053] Mix water and NaOH to obtain a sodium NaOH solution;

[0054] Modified recycled coarse aggregate, machine-made sand, zeolite powder, Na 2 SiO 3 The modified red brick powder and cement are mixed and stirred, and the sodium hydroxide solution is added and stirred evenly to obtain the modified recycled coarse aggregate concrete.

[0055] Furthermore, water and NaOH are mixed and stirred uniformly, and then cooled to obtain a sodium hydroxide solution.

[0056] Furthermore, the modified recycled coarse aggregate, machine-made sand, zeolite powder, red brick powder and cement are mixed and stirred for 10 to 60 seconds, the NaOH solution is added and stirred for 60 to 120 seconds to obtain modified recycled coarse aggregate concrete.

[0057] Example 1

[0058] A modified recycled coarse aggregate concrete, comprising, by weight, 300 parts of cement, 40 parts of zeolite powder, 2 SiO 3 300 parts of modified red brick powder, 40 parts of NaOH, 800 parts of machine-made sand, 950 parts of modified recycled coarse aggregate, and 200 parts of water.

[0059] A method for preparing modified recycled coarse aggregate concrete comprises the following steps:

[0060] S1. calcining the recycled coarse aggregate at 1050° C. for 3 h, and obtaining modified recycled coarse aggregate after cooling, wherein the particle size of the modified recycled coarse aggregate is 5 to 25 mm;

[0061] S2. Red bricks from old building demolition are crushed and ground into powder to obtain red brick powder. The average particle size of the red brick powder is 20-50 μm, and the composition thereof includes, by mass percentage: SiO 2 Content 55%-60%, CaO 2 Content 15%-25%, FeO content 5%-10%, Fe 2 O 3 Content 0-5%, Al 2 O 3 Content 0-5%; when the Fe 2 O 3 When the content is 0, it means that the red brick powder does not contain Fe 2 O 3 , when the Al 2 O 3 When the content is 0, it means that the red brick powder does not contain Al 2 O 3 ;

[0062] S3, placing the red brick powder in a 30wt% sodium silicate solution to completely immerse it for 4 hours, and then air-drying it to obtain Na 2 SiO 3 Modified red brick powder, making the Na 2 SiO 3 Modified red brick powder contains Na 2 SiO 3 .

[0063] S4, mixing 200 parts of water and 40 parts of NaOH, stirring evenly, and cooling to obtain a sodium hydroxide solution;

[0064] S5, 950 parts of modified recycled coarse aggregate, 800 parts of machine-made sand, 40 parts of zeolite powder, 300 parts of Na 2 SiO 3 The modified red brick powder and 300 parts of cement were poured into a mixer and fully mixed for 30 seconds, and the NaOH solution was added and stirred for 90 seconds until the mixture was uniform, thereby obtaining a modified recycled coarse aggregate concrete.

[0065] In this embodiment, the recycled coarse aggregate is recycled coarse aggregate from waste concrete, and its particle size is 5 to 20 mm. When used, it is washed with water to remove debris, dust and impurities on the surface of the recycled coarse aggregate, and then dried; the red bricks are selected from red bricks after the demolition of old buildings; the zeolite powder is natural zeolite powder, which is commercially available and produced in Xinyang, Henan. It is loosely agglomerated and has a large number of nano-scale pores. The particle shape is irregular and has the ability to absorb and solidify CO 2 The machine-made sand is medium-coarse sand with a fineness modulus of 2.1 to 3.0. The cement is Conch PO42.5 ordinary Portland cement. The purity of the sodium hydroxide is 99.5%, which is industrially purified sodium hydroxide.

[0066] Example 2

[0067] Compared with Example 1, most of the contents are the same, except that the modified recycled coarse aggregate concrete comprises, by mass, 325 parts of cement, 40 parts of zeolite powder, and Na 2 SiO 3 275 parts of modified red brick powder, 36 parts of NaOH, 800 parts of machine-made sand, 950 parts of modified recycled coarse aggregate, and 200 parts of water.

[0068] Example 3

[0069] Compared with Example 1, most of the contents are the same, except that the modified recycled coarse aggregate concrete comprises, by mass, 350 parts of cement, 40 parts of zeolite powder, and Na 2 SiO 3 250 parts of modified red brick powder, 32 parts of NaOH, 800 parts of machine-made sand, 950 parts of modified recycled coarse aggregate, and 200 parts of water.

[0070] Example 4

[0071] Compared with Example 1, most of the contents are the same, except that the modified recycled coarse aggregate concrete comprises, by mass, 375 parts of cement, 40 parts of zeolite powder, and Na 2 SiO 3225 parts of modified red brick powder, 28 parts of NaOH, 800 parts of machine-made sand, 950 parts of modified recycled coarse aggregate, and 200 parts of water.

[0072] Example 5

[0073] Compared with Example 1, most of the contents are the same, except that the modified recycled coarse aggregate concrete comprises, by mass, 400 parts of cement, 40 parts of zeolite powder, and Na 2 SiO 3 200 parts of modified red brick powder, 24 parts of NaOH, 800 parts of machine-made sand, 950 parts of modified recycled coarse aggregate, and 200 parts of water.

[0074] Example 6

[0075] Compared with Example 1, most of the contents are the same, except that the modified recycled coarse aggregate concrete comprises, by mass, 425 parts of cement, 40 parts of zeolite powder, and Na 2 SiO 3 175 parts of modified red brick powder, 20 parts of NaOH, 800 parts of machine-made sand, 950 parts of modified recycled coarse aggregate, and 200 parts of water.

[0076] Example 7

[0077] Compared with Example 1, most of the contents are the same, except that the modified recycled coarse aggregate concrete comprises, by mass, 450 parts of cement, 40 parts of zeolite powder, and Na 2 SiO 3 150 parts of modified red brick powder, 16 parts of NaOH, 800 parts of machine-made sand, 950 parts of modified recycled coarse aggregate, and 200 parts of water.

[0078] Example 8

[0079] Compared with Example 1, most of the contents are the same, except that the modified recycled coarse aggregate concrete comprises, by mass, 300 parts of cement, 40 parts of zeolite powder, and Na 2 SiO 3 300 parts of modified red brick powder, 40 parts of NaOH, 800 parts of machine-made sand, 850 parts of modified recycled coarse aggregate, and 200 parts of water.

[0080] Example 9

[0081] Compared with Example 1, most of the contents are the same, except that the modified recycled coarse aggregate concrete comprises, by mass, 300 parts of cement, 40 parts of zeolite powder, and Na 2 SiO 3 300 parts of modified red brick powder, 40 parts of NaOH, 800 parts of machine-made sand, 1000 parts of modified recycled coarse aggregate, and 200 parts of water.

[0082] Example 10

[0083] Compared with Example 1, most of the steps are the same, except that the recycled coarse aggregate is calcined at 1000°C for 4h to obtain modified recycled coarse aggregate.

[0084] Embodiment 11

[0085] Compared with Example 1, most of the steps are the same, except that the recycled coarse aggregate is calcined at 1100°C for 2h to obtain modified recycled coarse aggregate.

[0086] Comparative Example 1

[0087] A fly ash common concrete comprises, by weight, 950 parts of crushed stone, 800 parts of common sand, 550 parts of cement, 100 parts of fly ash, 16 parts of water reducing agent and 200 parts of water.

[0088] A method for preparing fly ash ordinary concrete comprises the following steps: pouring 950 parts of crushed stone and 800 parts of ordinary sand into a mixer, adding 550 parts of cement and 100 parts of fly ash, mixing and stirring for 30 seconds, and finally adding 200 parts of water mixed with 16 parts of a water reducing agent, mixing and stirring evenly, and obtaining C30 fly ash ordinary concrete.

[0089] In this embodiment, the crushed stone is modified recycled crushed stone with a particle size range of 5-31.5 mm, and the crushed stone is calcined at 1050°C for 3 hours to obtain modified recycled crushed stone; the cement is Conch PO42.5 ordinary Portland cement; the fly ash is Class I fly ash, taken from Jilin Yuanyuan Thermal Power Plant, with a density of 2868 kg / m 3 , specific surface area 5.1%, water requirement 94.1%, loss on ignition 4.76%, SO 3 The content is 0.48%; the water reducer is a naphthalene-based high-efficiency water reducer (sodium β-naphthalenesulfonate formaldehyde condensate) with a water reduction rate of 18%-28%, and the quality indicators meet the requirements of the "Concrete Admixtures" (GB8076-2008) standard.

[0090] Comparative Example 2

[0091] Compared with Example 5, most of the contents are the same, except that 950 parts of modified recycled coarse aggregate is adjusted to 712 parts of modified recycled coarse aggregate and 238 parts of crushed stone.

[0092] Comparative Example 3

[0093] Compared with Example 5, most of the contents are the same, except that 950 parts of modified recycled coarse aggregate is adjusted to 475 parts of modified recycled coarse aggregate and 475 parts of crushed stone.

[0094] Comparative Example 4

[0095] Compared with Example 5, most of the contents are the same, except that 950 parts of modified recycled coarse aggregate is adjusted to 238 parts of modified recycled coarse aggregate and 712 parts of crushed stone.

[0096] Comparative Example 5

[0097] Compared with Example 1, most of them are the same, except that the modified recycled coarse aggregate is changed to recycled coarse aggregate, which is not calcined and modified.

[0098] Comparative Example 6

[0099] Compared with Example 1, most of them are the same, except that the Na 2 SiO 3 Modified red brick powder is changed to red brick powder without modification.

[0100] Table 1 shows the compositions of Examples 1 to 9 and Comparative Examples 2 to 6 (by mass fraction).

[0101] Table 1 Composition of Examples 1 to 9 and Comparative Examples 2 to 6 (by mass fraction)

[0102]

[0103] The anti-setting time test and compressive strength test were carried out on Examples 1 to 9 and Comparative Examples 1 to 6. The setting time test method was carried out in accordance with the method in GB / T 50080-2016 "Standard Test Method for Performance of Ordinary Concrete Mixtures"; the compressive strength test method was carried out in accordance with the method in GB / T 50081-2019 "Standard Test Method for Physical and Mechanical Properties of Concrete".

[0104] Table 2 shows the anticoagulation time and compressive strength test results of Examples 1 to 9 and Comparative Examples 1 to 8.

[0105] Table 2 Anticoagulation time test and compressive strength test of Examples 1 to 10 and Comparative Examples 1 to 7

[0106]

[0107]

[0108] Comparative Example 1, Comparative Example 5, and Comparative Example 6 show that the modified recycled coarse aggregate and Na 2 SiO 3 The modified recycled coarse aggregate concrete prepared by modified red brick powder has higher strength. 2 SiO 3 When only ordinary recycled coarse aggregate or ordinary red brick powder is used, the strength of the recycled coarse aggregate concrete prepared is reduced, indicating that the use of modified recycled aggregate and Na 2SiO 3 The modified red brick powder plays a role in promoting the alkali-induced reaction, which is beneficial to improving the strength of concrete. The present invention calcines the recycled coarse aggregate to obtain the modified recycled coarse aggregate, so that the CaCO in the recycled aggregate 3 , Ca(OH) 2 The red brick powder can be decomposed to produce CaO; 2 SiO 3 Soak in solution to obtain Na 2 SiO 3 Modified red brick powder, Na 2 SiO 3 After being released in the red brick powder, it not only solidifies the recycled aggregate, but also acts as an alkali activator, so that the red brick powder and the CaO wrapped on the surface and inside of the modified recycled coarse aggregate form alkali-activated cementitious materials under the stimulation of sodium silicate and sodium hydroxide, thereby improving the bonding force between the surface of the recycled coarse aggregate and the alkali-activated cementitious materials, thereby greatly weakening the defects caused by insufficient bonding between the surface of the recycled coarse aggregate itself and the alkali-activated cementitious materials, thereby providing support for the modified recycled coarse aggregate concrete.

[0109] Zeolite powder itself contains porous inorganic internal curing agent. At the same time, zeolite powder has two major adsorption characteristics: selective adsorption and efficient adsorption, which can effectively adsorb CO 2 The present invention uses zeolite powder, when CO in the air 2 When low carbon concrete is corroded, the zeolite powder inside the modified recycled coarse aggregate will be able to absorb CO 2 In addition, when the zeolite powder cannot absorb the excess CO 2 When CO 2 The Ca(OH) in the residual cement paste on the surface of the modified recycled coarse aggregate 2 Reaction to produce CaCO 3 , blocking more micropore defects on the surface of modified recycled coarse aggregate, alleviating the problem that the strength of modified recycled coarse aggregate concrete cannot be improved due to defects in modified recycled coarse aggregate.

[0110] By comparing Examples 1 to 7, with the amount of modified recycled coarse aggregate unchanged, as Na 2 SiO 3 Adjustment of the dosage of modified red brick powder, modified recycled aggregate and Na 2 SiO 3 The overall calcium oxide content in the modified red brick powder was adjusted. 2 SiO 3 Effect of the dosage ratio of modified red brick powder on the modified recycled aggregate and Na 2 SiO 3The modified red brick powder has an effect, among which Examples 5, 6, and 7 have better mechanical properties, reaching or even exceeding that of C30 fly ash ordinary concrete (Comparative Example 1), and Example 7 has the best effect. 2 SiO 3 Under the action of NaOH, the alkali-activated reaction is promoted, the strength of the alkali-activated cementitious material is improved, and then the strength of the modified recycled coarse aggregate concrete is improved.

[0111] By observing Example 5 and Comparative Examples 2 to 4, it can be seen that with the gradual decrease in the amount of modified recycled coarse aggregate, the mechanical properties of the modified recycled coarse aggregate concrete show a trend of gradually decreasing, indicating that with the decrease in the modified recycled aggregate, the overall calcium oxide content in the modified recycled coarse aggregate and the modified red brick powder decreases. When the calcium oxide content is low, it is not conducive to the development of the strength of the alkali-activated cementitious material in the modified recycled coarse aggregate concrete, resulting in a lower strength of the modified recycled coarse aggregate concrete.

[0112] From the above, it can be seen that the modified recycled coarse aggregate concrete has good mechanical properties and high strength, which is better than the recycled coarse aggregate concrete prepared by ordinary recycled coarse aggregate. When the amount of modified recycled coarse aggregate and modified red brick powder is appropriate (such as Examples 5, 6, and 7), its mechanical properties are in a better state and can reach or even exceed C30 fly ash ordinary concrete (Comparative Example 1).

[0113] Although the present invention has been described in detail above by means of general description, specific implementation methods and tests, it is obvious to those skilled in the art that some modifications or improvements may be made to the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed by the present invention.

Claims

1. A modified recycled coarse aggregate concrete, characterized in that: The raw material components include the following parts by weight: 300-450 parts of cement, 30-50 parts of zeolite powder, 150-300 parts of sodium silicate modified red brick powder, 15-50 parts of sodium hydroxide, 750-900 parts of machine-made sand, 850-1000 parts of modified recycled coarse aggregate, and 150-200 parts of water; The preparation process of the modified recycled coarse aggregate is as follows: the recycled coarse aggregate is calcined and cooled to obtain the modified recycled coarse aggregate.

2. The modified recycled coarse aggregate concrete according to claim 1, characterized in that: The calcination temperature is 1100-1100° C., and the calcination time is 2-4 hours.

3. The modified recycled coarse aggregate concrete according to claim 1, characterized in that: The particle size of the modified recycled coarse aggregate ranges from 5 to 25 mm.

4. The modified recycled coarse aggregate concrete according to claim 1, characterized in that: The sodium silicate modified red brick powder is modified before use, and the modification process is: the red brick powder is soaked in a sodium silicate solution, and then dried to obtain the modified red brick powder.

5. The modified recycled coarse aggregate concrete according to claim 4, characterized in that: The composition of the red brick powder includes, by mass percentage: SiO2 content 55%-60%, CaO2 content 15%-25%, FeO content 5%-10%, Fe2O3 content 0-5%, Al2O3 content 0-5%; When the Fe2O3 content is 0, it means that the red brick powder does not contain Fe2O3, and when the Al2O3 content is 0, it means that the red brick powder does not contain Al2O3.

6. The modified recycled coarse aggregate concrete according to claim 4, characterized in that: The average particle size of the red brick powder is 20 to 50 μm.

7. The modified recycled coarse aggregate concrete according to claim 4, characterized in that: The mass concentration of the sodium silicate solution is 20wt%-40wt%, and the soaking time is 2-10h.

8. The modified recycled coarse aggregate concrete according to claim 1, characterized in that: The zeolite powder includes natural zeolite powder or synthetic zeolite powder.

9. The modified recycled coarse aggregate concrete according to claim 1, characterized in that: The machine-made sand is medium-coarse sand, and its fineness modulus is 2.1 to 3.

0.

10. The method for preparing a modified recycled coarse aggregate concrete according to any one of claims 1 to 9, characterized in that: The following steps are involved: calcining the recycled coarse aggregate and obtaining modified recycled coarse aggregate after cooling; Mixing water and sodium hydroxide to obtain a sodium hydroxide solution; The modified recycled coarse aggregate, machine-made sand, zeolite powder, sodium silicate modified red brick powder and cement are mixed and stirred, and the sodium hydroxide solution is added and stirred evenly to obtain the modified recycled coarse aggregate concrete.

Images