A recycled aggregate concrete and a method for producing the same

Abstract

The application discloses a kind of based on recycled aggregate concrete and preparation method thereof, belong to concrete preparation technical field.Concrete raw materials: cement 250-300 parts, sand 600-750 parts, modified recycled aggregate 300-400 parts, polypropylene fiber 250-350 parts, fly ash 100-200 parts, water 150-200 parts, mineral powder 80-100 parts, water reducing agent 3-8 parts.Modified recycled aggregate internal gap is less, apparent density is greater, so that the surface structure and density of modified recycled aggregate are improved;The mechanical properties, heat resistance, dimensional stability and corrosion resistance of polypropylene fiber added with modified glass fiber are more excellent;Modified recycled aggregate and polypropylene fiber form a network structure of mutual crosslinking support, not only improve the connection strength between polypropylene fiber and concrete skeleton, but also enhance the anti-cracking performance, compressive strength and impermeability of the concrete of the application.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of concrete preparation, and particularly relates to a recycled aggregate concrete and a preparation method thereof. BACKGROUND

[0002] Concrete has the characteristics of rich raw materials, low price and simple production process. In building engineering, the use amount of concrete is the largest, so the amount of waste concrete produced by the demolition of waste concrete, newly built buildings and the discharge of waste concrete from ready-mixed concrete plants and concrete prefabricated component plants is also huge. Among the several raw materials of concrete, the use amount of aggregate is the largest. Therefore, it has very important environmental and resource protection significance to use waste concrete as recycled aggregate to manufacture concrete and realize the recycling use of concrete materials.

[0003] However, the recycled aggregate is wrapped with a considerable amount of cement mortar on the surface, and the surface is rough and has many corners. Since the cement mortar has a large porosity, and in addition, a large number of microcracks exist in the recycled aggregate due to damage accumulation in the process of disintegration and crushing of the concrete block, the density and apparent density of the recycled aggregate are lower than those of ordinary aggregate, and the recycled aggregate concrete prepared therefrom has problems of insufficient compressive strength and poor impermeability. SUMMARY

[0004] The application aims to overcome the defects of the prior art and provide a recycled aggregate concrete and a preparation method thereof.

[0005] The object of the application can be achieved by the following technical scheme.

[0006] The recycled aggregate concrete comprises the following raw materials in parts by weight: cement 250-300 parts, sand 600-750 parts, modified recycled aggregate 300-400 parts, polypropylene fiber 250-350 parts, fly ash 100-200 parts, water 150-200 parts, mineral powder 80-100 parts and water reducing agent 3-8 parts.

[0007] Further, the modified recycled aggregate is prepared by the following steps.

[0008] (1) The recycled aggregate, anhydrous ethanol, deionized water and ammonia water are added into a beaker, stirred for 0.5 h, then tetraethyl orthosilicate is slowly added, stirred at room temperature for 12 h, and then filtered and dried to obtain pretreated recycled aggregate; the use amount ratio of the recycled aggregate, anhydrous ethanol, deionized water, ammonia water and tetraethyl orthosilicate is 20 g:24 mL:80 mL:1 mL:1 mL;

[0009] (2) Dry the three-necked flask with nitrogen blowing for 30 min to remove air and moisture, then add 1,2-bistrimethoxysilylethane, titanium tetraisopropylate and dimethyl sulfoxide, stir uniformly, then warm up to 90℃, then slowly add epoxypropanol, after the addition is completed, keep warm for 24 h, after the reaction is completed, cool to room temperature, distill under reduced pressure, wash with anhydrous ethanol for 3 times, dry at 80℃ for 12 h, the whole process is carried out under nitrogen protection, to obtain the additive; the amount ratio of 1,2-bistrimethoxysilylethane, epoxypropanol, titanium tetraisopropylate and dimethyl sulfoxide is 54.2 mL:14.8 g:1.9 mL:200 mL;

[0010] (3) Disperse the pretreated recycled aggregate of step (1) in a mixed solution of anhydrous ethanol and deionized water, after stirring uniformly, slowly add the additive of step (2), after the addition is completed, warm up to 65℃, stir for 2 h, remove the filtrate by filtration, dry the filter residue at 100℃ for 12 h, to obtain the modified recycled aggregate; the amount ratio of pretreated recycled aggregate, additive, anhydrous ethanol and deionized water is 15 g:0.75 g:10 mL:150 mL.

[0011] In step (1), tetraethyl orthosilicate hydrolyzes and condenses in the large number of micro-cracks and gaps in the recycled aggregate under the catalysis of ammonia water, to generate monodisperse silica particles, thereby filling the recycled aggregate, increasing its density, and preparing pretreated recycled aggregate with larger apparent density; in step (2), the siloxy group of 1,2-bistrimethoxysilylethane and the hydroxyl group of epoxypropanol react under the catalysis of titanium tetraisopropylate, to prepare the additive containing siloxy group and epoxy group; after the treatment of step (3), the siloxy group of the additive in step (2) hydrolyzes and condenses to form chemical bonds with the hydroxyl group on the surface of the silica particles in the pretreated recycled aggregate and inside the pretreated recycled aggregate, thereby making the modified recycled aggregate have fewer internal gaps and larger apparent density, which can not only avoid the water absorption of the modified recycled aggregate in the mixing process with concrete, but also improve the surface structure and density of the modified recycled aggregate, thereby enhancing the strength of the concrete of the application.

[0012] Further, the polypropylene fiber is prepared by the following steps:

[0013] 100 parts of polypropylene resin, 10-15 parts of modified glass fiber, 2-4 parts of toughening agent and 0.01-0.05 parts of initiator are weighed by weight parts and uniformly mixed, then sent into a twin-screw extruder for melt blending, polypropylene chips are prepared, then melt spinning and drawing winding are carried out, to obtain polypropylene fiber.

[0014] Further, the modified glass fiber is prepared by the following steps:

[0015] S1, dry three-necked flask is blown with nitrogen for 30 min to exclude air and moisture, then 3-aminopropyl triethoxysilane and toluene are added, after stirring, the temperature is raised to 65 DEG C, then the epoxy butene is slowly added, after the addition is completed, the reaction is kept for 6h, after the reaction is completed, it is cooled to room temperature, and distilled under reduced pressure, the whole process is carried out under nitrogen protection, to obtain intermediate 1; the amount ratio of 3-aminopropyl triethoxysilane, epoxy butene and toluene is 50.4 mL: 16.1 mL: 200 mL;

[0016] Under the condition of heating, the amino group of 3-aminopropyl triethoxysilane and the epoxy group of epoxy butene undergo ring-opening reaction to prepare intermediate 1;

[0017] S2, the glass fiber, deionized water are mixed uniformly in a three-necked flask, then glacial acetic acid is slowly added to adjust the pH to 4, then a mixed solution of intermediate 1 and anhydrous ethanol is slowly added while stirring, after the addition is completed, the temperature is raised to 65 DEG C, and the reaction is kept for 1h, after the reaction is completed, it is cooled to room temperature, centrifuged, and dried at 100 DEG C for 12h to obtain modified glass fiber; the amount ratio of glass fiber, intermediate 1, anhydrous ethanol and deionized water is 25g: 2g: 15mL: 150mL.

[0018] The main components of glass fiber are silicon dioxide, aluminum oxide, calcium oxide, boron oxide, magnesium oxide, sodium oxide, etc., so the glass fiber surface contains rich hydroxyl groups, the silanol groups on the surface of intermediate 1 are hydrolyzed under the condition of heating and acidity to form chemical bonds with the hydroxyl groups on the surface of glass fiber, and then the modified glass fiber is prepared.

[0019] The polypropylene fiber can well improve the crack resistance, permeability resistance, impact resistance, frost resistance, blast resistance and workability of concrete. The polypropylene fiber is uniformly distributed in the concrete, which can play a good micro-reinforcing effect, which can well maintain the integrity of the concrete structure, avoid the structure from being broken into many fragments when the structure is impacted, prevent the corrosion of the steel bars in the structure, greatly prolong the service life of the project, and reduce the maintenance cost of the project.

[0020] The compatibility between the modified glass fiber and the polypropylene resin is greatly increased after the treatment of the modified glass fiber by intermediate 1, and the surface of the modified glass fiber contains terminal carbon-carbon double bonds, which can react with the terminal unreacted carbon-carbon double bonds of the polypropylene resin under the action of a small amount of initiator in the melt blending process, and then the modified glass fiber is highly dispersed and stably exists in the polypropylene fiber and is not easy to migrate and come out, so that the mechanical properties, heat resistance, dimensional stability and corrosion resistance of the polypropylene fiber can be greatly enhanced, and the polypropylene fiber can synergistically improve the compressive strength, crack resistance, permeability resistance, dimensional stability and corrosion resistance of concrete.

[0021] Further, in the preparation process of the modified recycled aggregate, the auxiliary agent prepared in step (2) contains not only siloxy group but also epoxy group, and under the treatment of intermediate 1, the surface of the modified glass fiber contains amino and hydroxyl groups, and the surface of the polypropylene fiber contains amino and hydroxyl groups, and the epoxy group in the auxiliary agent can be chemically bonded with the amino and hydroxyl groups in the polypropylene fiber, and further, a network structure of mutual cross-linking support is formed between the polypropylene fiber and the modified recycled aggregate, which not only improves the connection strength between the polypropylene fiber and the concrete framework, but also enhances the anti-cracking performance and the compressive strength of the concrete, and improves the impermeability of the concrete.

[0022] Further, the toughening agent is one or both of ethylene-vinyl acetate copolymer and styrene-butadiene-styrene block copolymer.

[0023] Further, the initiator is one or more of dicumyl peroxide, di-tert-butyl peroxide and azobisisobutyronitrile.

[0024] Further, the water reducing agent is one or more of sodium lignosulfonate, magnesium lignosulfonate and calcium lignosulfonate.

[0025] A preparation method of recycled aggregate concrete, comprising the following steps:

[0026] The raw materials are weighed by weight parts, the cement, sand and mineral powder are first mixed uniformly, then the water and the water reducing agent are added, and the mixture is fully stirred, then the modified recycled aggregate and the polypropylene fiber are added, and the mixture is stirred uniformly, then the fly ash is added, and the mixture is uniformly mixed to obtain the recycled aggregate concrete.

[0027] The modified recycled aggregate filled with monodisperse silica particles and treated with the auxiliary agent has fewer internal gaps and higher apparent density, so that the surface structure and density of the modified recycled aggregate are improved, the polypropylene fiber prepared by mixing the modified glass fiber with polypropylene resin and other raw materials has more excellent mechanical properties, heat resistance, dimensional stability and corrosion resistance, and the network structure of mutual cross-linking support is formed between the modified recycled aggregate and the polypropylene fiber, which not only improves the connection strength between the polypropylene fiber and the concrete framework, but also enhances the anti-cracking performance, the compressive strength and the impermeability of the concrete. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0029] Example 1, preparation of modified recycled aggregate, the specific steps are as follows:

[0030] (1) 20 g of recycled aggregate, 24 mL of anhydrous ethanol, 80 mL of deionized water and 1 mL of ammonia water were added into a beaker, stirred for 0.5 h, then 1 mL of tetraethyl orthosilicate was slowly added, stirred at room temperature for 12 h, filtered and dried to obtain the pretreated recycled aggregate;

[0031] (2) A 500 mL dry three-necked flask was blown with nitrogen for 30 min to exclude air and moisture, then 54.2 mL of 1,2-bistrimethoxysilyl ethane, 1.9 mL of titanium isopropylate and 200 mL of dimethyl sulfoxide were added, stirred uniformly, then heated to 90℃, then 14.8 g of glycidol was slowly added, after the addition was completed, the reaction was kept for 24 h, after the reaction was completed, it was cooled to room temperature, distilled under reduced pressure, washed with anhydrous ethanol for 3 times, dried at 80℃ for 12 h, the whole process was carried out under nitrogen protection, to obtain the additive;

[0032] (3) 15 g of the pretreated recycled aggregate of step (1) was dispersed in a mixed solution of 10 mL of anhydrous ethanol and 150 mL of deionized water, stirred uniformly, then 0.75 g of the additive of step (2) was slowly added, after the addition was completed, it was heated to 65℃, stirred for 2 h, the filtrate was removed by filtration, and the residue was dried at 100℃ for 12 h to obtain the modified recycled aggregate.

[0033] Example 2, preparation of modified glass fiber, the specific steps are as follows:

[0034] S1, a 500 mL dry three-necked flask was blown with nitrogen for 30 min to exclude air and moisture, then 50.4 mL of 3-aminopropyltriethoxysilane and 200 mL of toluene were added, stirred uniformly, then heated to 65℃, then 16.1 mL of epoxy butene was slowly added, after the addition was completed, the reaction was kept for 6 h, after the reaction was completed, it was cooled to room temperature, distilled under reduced pressure, the whole process was carried out under nitrogen protection, to obtain the intermediate 1;

[0035] S2, 25 g of glass fiber and 150 mL of deionized water were mixed uniformly in a 500 mL three-necked flask, then 2 g of the mixed solution of intermediate 1 and 15 mL of anhydrous ethanol was slowly added while stirring, after the addition was completed, it was heated to 65℃, kept for 1 h, after the reaction was completed, it was cooled to room temperature, centrifuged, dried at 100℃ for 12 h, to obtain the modified glass fiber.

[0036] Example 3, preparation of polypropylene fiber, the specific steps are as follows:

[0037] Take 100 parts of polypropylene resin, 10 parts of modified glass fiber prepared in Example 2, 2 parts of ethylene-vinyl acetate copolymer and 0.01 part of azobisisobutyronitrile by weight, and mix uniformly, then send into a twin-screw extruder for melt blending, after polypropylene chips are prepared, melt spinning and drawing and winding are carried out, and polypropylene fiber is obtained.

[0038] Example 4, preparation of polypropylene fiber, the specific steps are as follows:

[0039] Take 100 parts of polypropylene resin, 12 parts of modified glass fiber prepared in Example 2, 3 parts of styrene-butadiene-styrene block copolymer and 0.03 parts of di-t-butyl peroxide by weight, and mix uniformly, then send into a twin-screw extruder for melt blending, after polypropylene chips are prepared, melt spinning and drawing and winding are carried out, and polypropylene fiber is obtained.

[0040] Example 5, preparation of polypropylene fiber, the specific steps are as follows:

[0041] Take 100 parts of polypropylene resin, 15 parts of modified glass fiber prepared in Example 2, 2 parts of ethylene-vinyl acetate copolymer, 2 parts of styrene-butadiene-styrene block copolymer and 0.05 parts of dicumyl peroxide by weight, and mix uniformly, then send into a twin-screw extruder for melt blending, after polypropylene chips are prepared, melt spinning and drawing and winding are carried out, and polypropylene fiber is obtained.

[0042] Example 6, preparation of concrete, the specific steps are as follows:

[0043] Take each raw material by weight, first mix 250 parts of cement, 600 parts of sand, 80 parts of mineral powder uniformly, then add 150 parts of water and 3 parts of sodium lignosulfonate, stir well, then add 300 parts of modified recycled aggregate prepared in Example 1 and 250 parts of polypropylene fiber prepared in Example 3, stir uniformly, then add 100 parts of fly ash, mix uniformly to prepare concrete.

[0044] Example 7, preparation of concrete, the specific steps are as follows:

[0045] Take each raw material by weight, first mix 280 parts of cement, 700 parts of sand, 90 parts of mineral powder uniformly, then add 180 parts of water and 7 parts of magnesium lignosulfonate, stir well, then add 350 parts of modified recycled aggregate prepared in Example 1 and 300 parts of polypropylene fiber prepared in Example 4, stir uniformly, then add 170 parts of fly ash, mix uniformly to prepare concrete.

[0046] Example 8, preparation of concrete, the specific steps are as follows:

[0047] The raw materials were weighed by parts by weight, 300 parts of cement, 750 parts of sand, 100 parts of mineral powder were mixed uniformly, then 200 parts of water, 4 parts of magnesium lignin sulfonate and 4 parts of calcium lignin sulfonate were added, and stirred thoroughly, then 400 parts of the modified recycled aggregate prepared in Example 1 and 350 parts of the polypropylene fiber prepared in Example 5 were added, and stirred uniformly, then 200 parts of fly ash was added, and mixed uniformly to prepare the concrete.

[0048] Comparative Example 1, polypropylene fibers were prepared, and the specific steps were as follows:

[0049] The remaining steps were unchanged, only the modified glass fiber in Example 3 was replaced with glass fiber without any treatment, and polypropylene fiber was prepared.

[0050] Comparative Example 2, concrete was prepared, and the specific steps were as follows:

[0051] The remaining steps were unchanged, only the modified recycled aggregate in Example 6 was replaced with recycled aggregate without any treatment, and concrete was prepared.

[0052] Comparative Example 3, concrete was prepared, and the specific steps were as follows:

[0053] The remaining steps were unchanged, only the polypropylene fiber in Example 6 was replaced with the polypropylene fiber prepared in Comparative Example 1, and concrete was prepared.

[0054] Performance test

[0055] 1. The compressive strength of the concrete prepared in Examples 6-8 and Comparative Examples 2-3 was detected according to GB / T 50081-2002 "Standard for Testing Methods of Mechanical Properties of Ordinary Concrete".

[0056] 2. According to the standard of GB / T 50082-2009, the impermeability of the concrete prepared in Examples 6-8 and Comparative Examples 2-3 was tested by preparing a circular truncated cone sample with a diameter of 175mm and 185mm at the top and bottom respectively and a height of 150mm (curing time was 28d). The average water penetration height of the hardened concrete sample under a constant water pressure of 1.2MPa was measured to represent the water permeability of the concrete. The greater the average water penetration height, the worse the impermeability;

[0057] 3. The early crack resistance of the concrete prepared in Examples 6-8 and Comparative Examples 2-3 was detected according to the standard of early crack resistance test in GB / T 50082-2009, and the total cracking area per unit area (mm 2 / m 2 ) of the recycled aggregate concrete at 24h after pouring was measured. The smaller the total cracking area per unit area, the better the early crack resistance of the recycled aggregate concrete.

[0058] The test results of all items are shown in the following table:

[0059]

[0060] From the above test results, compared with the concrete prepared by Comparative Example 2-3, the concrete prepared by Examples 6-8 has more excellent compressive strength, impermeability and crack resistance, which shows that the modified recycled aggregate, modified glass fiber and polypropylene fiber play an important role in improving the strength, impermeability and crack resistance of the concrete.

[0061] In the description of the specification, the description of the terms "one embodiment", "an example", "a specific example" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0062] The above is only an example and description of the present application, and those skilled in the art can make various modifications or supplements to the described specific embodiments or use similar ways to replace, as long as it does not deviate from the invention or exceed the scope defined by the present claims, which shall belong to the protection scope of the present application.

Claims

1. A type of concrete based on recycled aggregate, characterized in that, The raw materials include the following parts by weight: 250-300 parts cement, 600-750 parts sand, 300-400 parts modified recycled aggregate, 250-350 parts polypropylene fiber, 100-200 parts fly ash, 150-200 parts water, 80-100 parts mineral powder, and 3-8 parts water-reducing agent. The modified recycled aggregate is prepared through the following steps: (1) Stir the recycled aggregate, anhydrous ethanol, deionized water and ammonia, then add tetraethyl orthosilicate, stir at room temperature, filter and dry to obtain pretreated recycled aggregate; (2) After nitrogen blowing the flask, add 1,2-bis(trimethoxysilyl ethane), tetraisopropyl titanate and dimethyl sulfoxide, stir and heat to 90°C, add glycidol, react for 24 h, cool, distill under reduced pressure, wash and dry to obtain the auxiliary agent. (3) Disperse the pretreated recycled aggregate from step (1) in a mixed solution of anhydrous ethanol and deionized water, add the additive from step (2) after stirring, heat to 65°C, stir for 2 hours, filter, dry the filter residue, and obtain modified recycled aggregate. The polypropylene fiber is prepared by the following steps: 100 parts by weight of polypropylene resin, 10-15 parts by weight of modified glass fiber, 2-4 parts by weight of toughening agent and 0.01-0.05 parts by weight of initiator are weighed and mixed, fed into a twin-screw extruder for melt blending, and after obtaining polypropylene chips, melt spinning and drawing and winding are performed to obtain polypropylene fiber. The modified glass fiber is prepared by the following steps: S1. After blowing nitrogen into the flask, add 3-aminopropyltriethoxysilane and toluene, stir and heat to 65°C, add epoxybutene, react for 6 hours, and distill under reduced pressure to obtain intermediate 1. S2. Mix glass fiber and deionized water in a flask, add glacial acetic acid to adjust the pH to 4, add intermediate 1 and anhydrous ethanol, heat to 65°C, react for 1 hour, cool, centrifuge, and dry to obtain modified glass fiber.

2. The recycled aggregate-based concrete according to claim 1, characterized in that, The ratio of recycled aggregate, anhydrous ethanol, deionized water, ammonia and tetraethyl orthosilicate in step (1) is 20g:24mL:80mL:1mL:1mL.

3. The recycled aggregate-based concrete according to claim 1, characterized in that, The ratio of 1,2-bis(trimethoxysilyl ethane), glycidol, tetraisopropyl titanate and dimethyl sulfoxide in step (2) is 54.2 mL: 14.8 g: 1.9 mL: 200 mL.

4. The recycled aggregate-based concrete according to claim 1, characterized in that, The ratio of the amount of pretreated recycled aggregate, additives, anhydrous ethanol and deionized water in step (3) is 15g:0.75g:10mL:150mL.

5. The recycled aggregate-based concrete according to claim 1, characterized in that, In step S1, the ratio of 3-aminopropyltriethoxysilane, epoxybutene, and toluene is 50.4 mL: 16.1 mL: 200 mL.

6. The recycled aggregate-based concrete according to claim 1, characterized in that, The ratio of glass fiber, intermediate 1, anhydrous ethanol and deionized water used in step S2 is 25g:2g:15mL:150mL.

7. A type of recycled aggregate concrete according to claim 1, characterized in that, The toughening agent is one or both of ethylene-vinyl acetate copolymer and styrene-butadiene-styrene block copolymer.

8. A type of recycled aggregate concrete according to claim 1, characterized in that, The initiator is one or more of dicumyl peroxide, di-tert-butyl peroxide, and azobisisobutyronitrile.

9. A type of recycled aggregate concrete according to claim 1, characterized in that, The water-reducing agent is one or more of sodium lignosulfonate, magnesium lignosulfonate, and calcium lignosulfonate.

10. The method for preparing recycled aggregate concrete according to claim 1, characterized in that, Includes the following steps: Weigh each raw material according to weight. First, mix cement, sand, and mineral powder evenly. Then add water and water-reducing agent and stir thoroughly. Next, add modified recycled aggregate and polypropylene fiber and stir evenly. Then add fly ash and mix evenly to obtain recycled aggregate concrete.

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