Concrete prepared from recycled aggregate and preparation method thereof

Abstract

The invention relates to the field of concrete, in particular to concrete prepared from recycled aggregate and a preparation method of the concrete. The concrete prepared from the recycled aggregate is prepared from quick lime, the modified recycled aggregate, an alkaline activator, a siliceous reinforcing filler, a water reducing agent, chopped fibers and water, the preparation method of the modified recycled aggregate comprises the following steps: mixing hydroxyethyl acrylate and sulfopropyl methacrylate, adding hydroxypropyl methacrylate, and mixing to obtain a mixed monomer solution; mixing an initiator, nano silicon dioxide gel, N, N '-methylene bisacrylamide and water, adding the mixture into the mixed monomer solution, and reacting to obtain a gel material; mixing the recycled aggregate and the gel material, and curing to obtain the modified recycled aggregate. By adopting specific raw material components and a modified recycled aggregate preparation process, the performance of the recycled aggregate is remarkably improved.

Description

Technical Field

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

[0002] The large accumulation of construction waste will cause serious pollution to the ecological environment. Using recycled aggregates obtained after a series of processing such as crushing, cleaning, and grading of waste concrete for concrete production has become an important way to realize the resource utilization of construction waste. However, recycled aggregates have problems such as high water absorption, many fine cracks, poor durability and bonding properties, which greatly limit their application in concrete engineering. At present, there are two main methods for treating recycled aggregates: physical strengthening and chemical strengthening. Physical strengthening activates coarse aggregates through mechanical methods, destroys weak recycled gravel particles or removes residual mortar adhering to recycled gravel; chemical strengthening is to improve the surface state of recycled aggregates by adding additives to strengthen the transition zone of the recycled concrete interface. However, these methods still have shortcomings in improving the performance of recycled aggregates, especially cracks and voids generated during the treatment process, which lead to a large water absorption rate of recycled aggregates, thereby affecting the strength and durability of concrete. Summary of the invention

[0003] In view of this, the present invention is committed to providing a concrete prepared from recycled aggregate and a preparation method thereof, so as to solve the problems of high water absorption and many fine cracks of recycled aggregate in the prior art.

[0004] In order to solve the above technical problems, this application is implemented as follows:

[0005] The present invention provides a concrete prepared from recycled aggregate, comprising the following components in parts by weight:

[0006] 700-800 parts of quicklime, 500-650 parts of modified recycled aggregate, 150-160 parts of alkaline activator, 200-220 parts of siliceous reinforcing filler, 7-10 parts of water reducer, 15-25 parts of chopped fiber and 200-250 parts of water;

[0007] The method for preparing the modified recycled aggregate comprises the following steps:

[0008] Mixing hydroxyethyl acrylate and sulfopropyl methacrylate, adjusting the neutralization degree thereof with a NaOH solution, and then adding hydroxypropyl methacrylate to mix, thereby obtaining a mixed monomer solution;

[0009] The initiator, nano-silica gel, N,N'-methylenebisacrylamide and water are mixed, dispersed and added into the mixed monomer solution to react and obtain a gel material;

[0010] The recycled aggregate and the gel material are mixed and solidified to obtain the modified recycled aggregate.

[0011] Preferably, in the concrete prepared from the above-mentioned recycled aggregate, the mass ratio of hydroxyethyl acrylate, sulfopropyl methacrylate and hydroxypropyl methacrylate is 5-10:2-4:1-2;

[0012] The mass ratio of hydroxyethyl acrylate to initiator is 5-10:0.08-0.12;

[0013] The mass ratio of hydroxyethyl acrylate to nano-silica aerogel is 5-10:4-6;

[0014] The dosage ratio of the hydroxyethyl acrylate, N,N'-methylenebisacrylamide and water is 5-10 g: 0.05-0.1 g: 2.5-5 mL;

[0015] The reaction method is microwave polymerization, the power of the microwave polymerization is 300-400W, and the time of the microwave polymerization is 2-4h.

[0016] Preferably, in the concrete prepared from the above-mentioned recycled aggregate, the mass ratio of the recycled aggregate to the gel material is 1:1-3;

[0017] The curing conditions are as follows: temperature of 20-30° C., time of 12-24 hours, and humidity of 50-60%.

[0018] Preferably, in the concrete prepared from the above-mentioned recycled aggregate, the alkaline activator comprises fly ash and sodium hydroxide;

[0019] The mass ratio of the fly ash to sodium hydroxide is 8-10:1.

[0020] Preferably, in the concrete prepared from the above-mentioned recycled aggregate, the siliceous reinforcing filler comprises silica fume modified by an aminosilane coupling agent;

[0021] The water reducing agent includes a polycarboxylate water reducing agent.

[0022] Preferably, in the concrete prepared from the above-mentioned recycled aggregate, the chopped fibers include at least one of polyvinyl alcohol fibers, polyvinyl alcohol nitrile fibers, polypropylene fibers, glass fibers, basalt fibers and carbon fibers;

[0023] The length of the chopped fibers is 3 to 6 mm.

[0024] The present invention also provides a method for preparing concrete made from recycled aggregate, comprising the following steps:

[0025] Mix quicklime, alkaline activator, siliceous reinforcing filler and water reducing agent, then add water and mix to obtain slurry;

[0026] After the slurry and the chopped fibers are mixed, the modified recycled aggregate is added and mixed to obtain a mixture;

[0027] The mixture is poured and cured to obtain concrete.

[0028] Preferably, in the concrete prepared from the above-mentioned recycled aggregate, the curing temperature is 25 to 30° C., and the curing time is 25 to 30 days.

[0029] Through the above technical solution, the beneficial technical effects of the present invention are:

[0030] (1) In the concrete prepared from the recycled aggregate provided in the present invention, the recycled aggregate is modified by using a gel material. Specifically, hydroxyethyl acrylate, sulfopropyl methacrylate and hydroxypropyl methacrylate undergo free radical polymerization under the action of an initiator and a crosslinking agent to form a polymer having a three-dimensional grid structure. Hydroxyethyl acrylate and hydroxypropyl methacrylate contain hydroxyl functional groups, which can form hydrogen bonds or chemical bonds with active groups on the surface of the aggregate, thereby enhancing the interaction between the aggregate and the polymer. Sulfopropyl methacrylate contains a sulfonic acid group, which can provide good hydrophilicity and ion exchange capacity, and help improve the dispersibility and adhesion of the polymer on the surface of the aggregate. By forming a layer of polymer film on the surface of the aggregate, the tiny pores and cracks on the surface of the aggregate can be filled, thereby improving the density and strength of the aggregate. At the same time, the polymer network can enhance the bonding force between the aggregate particles, improve the compressive and tensile properties of the aggregate, and reduce the breakage and shedding of the aggregate during the use of the concrete, thereby improving the overall mechanical properties of the recycled aggregate. Nano-silica gel has a large specific surface area and high activity. It can react with calcium hydroxide and other components in aggregates to generate substances such as hydrated calcium silicate. These hydration products can fill the pores of aggregates and improve the density and strength of aggregates. In addition, nano-silica gel can also react with cement hydration products during cement hydration to enhance the interfacial adhesion between aggregates and cement paste. Through chemical reactions with aggregates and cement paste, nano-silica gel can significantly improve the strength and durability of recycled aggregates. It can reduce pores and defects in aggregates, improve the compressive strength and flexural strength of aggregates, and enhance the adhesion between aggregates and cement matrix, so that the overall mechanical properties of concrete are improved. That is, the acrylate monomer combines with the surface of recycled aggregates through hydrogen bonds and ionic bonds to construct a chemically strengthened interface transition zone; nano-silica accurately repairs micron-level cracks and cooperates with the gel macromolecular network to achieve multi-level pore blocking.

[0031] (2) The concrete prepared from the recycled aggregate provided in the present invention comprises quicklime, modified recycled aggregate, alkaline activator, siliceous reinforcing filler, water reducing agent, chopped fibers and water; wherein the high strength and good bonding property of the modified recycled aggregate and the addition of chopped fibers effectively improve the compressive, flexural and tensile strength of the concrete, enhance its toughness and impact resistance, and reduce the occurrence of cracks; the alkaline activator and siliceous reinforcing filler optimize the pore structure of the concrete, reduce the porosity, enhance its impermeability, frost resistance and carbonization resistance, and extend its service life; the silica fume modified by the aminosilane coupling agent further improves the strength and stability of the concrete, enabling it to maintain good performance in harsh environments. DETAILED DESCRIPTION

[0032] The present invention discloses a concrete prepared from recycled aggregate and a preparation method thereof. Those skilled in the art can refer to the content of this article and appropriately improve the process parameters to achieve the same. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are deemed to be included in the present invention. The method and application of the present invention have been described through preferred embodiments, and relevant personnel can obviously modify or appropriately change and combine the method and application described herein without departing from the content, spirit and scope of the present invention to implement and apply the technology of the present invention.

[0033] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range or the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0034] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0035] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0036] If there is no special explanation, the "include" and "comprising" mentioned in this application represent open-ended or closed-ended expressions. For example, the "include" and "comprising" may represent that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0037] The present invention provides a concrete prepared from recycled aggregate, comprising the following components in parts by weight:

[0038] 700-800 parts of quicklime, 500-650 parts of modified recycled aggregate, 150-160 parts of alkaline activator, 200-220 parts of siliceous reinforcing filler, 7-10 parts of water reducer, 15-25 parts of chopped fibers and 200-250 parts of water.

[0039] In the present invention, the weight proportion of quicklime in the concrete prepared from the recycled aggregate is preferably 700 to 800 parts, more preferably 720 to 780 parts, and even more preferably 750 to 760 parts.

[0040] In the present invention, the weight proportion of the modified recycled aggregate in the concrete prepared from the recycled aggregate is preferably 500 to 650 parts, more preferably 530 to 600 parts, and even more preferably 550 to 580 parts.

[0041] In the present invention, the weight portion of the alkaline activator in the concrete prepared from the recycled aggregate is preferably 150 to 160 parts, more preferably 152 to 157 parts, and even more preferably 155 to 156 parts.

[0042] In the present invention, the weight portion of the siliceous reinforcing filler in the concrete prepared from the recycled aggregate is preferably 205 to 217 parts, more preferably 210 to 215 parts.

[0043] In the present invention, the weight portion of the water reducing agent in the concrete prepared from the recycled aggregate is preferably 7 to 10 parts, more preferably 7.5 to 9 parts, and even more preferably 8 to 8.5 parts.

[0044] In the present invention, the weight proportion of the chopped fibers in the concrete prepared from the recycled aggregate is preferably 15 to 25 parts, more preferably 18 to 23 parts, and even more preferably 20 to 22 parts.

[0045] In the present invention, the method for preparing the modified recycled aggregate comprises the following steps:

[0046] Mixing hydroxyethyl acrylate and sulfopropyl methacrylate, adjusting the neutralization degree thereof with a NaOH solution, and then adding hydroxypropyl methacrylate to mix, thereby obtaining a mixed monomer solution;

[0047] The initiator, nano-silica gel, N,N'-methylenebisacrylamide and water are mixed, ultrasonically dispersed, and then added to the mixed monomer solution to react to obtain a gel material;

[0048] The recycled aggregate and the gel material are mixed and solidified to obtain the modified recycled aggregate.

[0049] In the present invention, the mass ratio of hydroxyethyl acrylate, sulfopropyl methacrylate and hydroxypropyl methacrylate is preferably 5-10:2-4:1-2, more preferably 6-9:2.5-3.5:1.2-1.8, and more preferably 7-8:2.8-3:1.5-1.6.

[0050] In the present invention, the target value of the neutralization degree is 70%.

[0051] In the present invention, the mass ratio of the hydroxyethyl acrylate to the initiator is preferably 5-10:0.08-0.12, more preferably 6-9:0.09-0.11, and more preferably 7-8:0.1.

[0052] In the present invention, the initiator includes ammonium persulfate.

[0053] In the present invention, the mass ratio of hydroxyethyl acrylate to nano-silica aerogel is preferably 5-10:4-6, more preferably 6-9:4.5-5.5, and more preferably 7-8:4.8-5.

[0054] In the present invention, the usage ratio of hydroxyethyl acrylate, N,N'-methylenebisacrylamide and water is preferably 5-10g: 0.05-0.1g: 2.5-5mL, more preferably 6-9g: 0.06-0.09g: 3-4.5mL, and more preferably 7-8g: 0.07-0.08g: 3.5-4mL.

[0055] In the present invention, the reaction method is microwave polymerization, and the power of the microwave polymerization is preferably 300-400 W, more preferably 320-380 W, and more preferably 330-350 W; the time of the microwave polymerization is preferably 2-4 h, more preferably 2.5-3.5 h, and more preferably 3 h.

[0056] In the present invention, the mass ratio of the recycled aggregate to the gel material is preferably 1:1-3, more preferably 1:1.5-2.5, and even more preferably 1:2.

[0057] In the present invention, the curing conditions are: the temperature is preferably 20-30°C, more preferably 22-28°C, and more preferably 25°C; the time is preferably 12-24h, more preferably 15-20h, and more preferably 17-18h; the humidity is preferably 50-60%, more preferably 52-56%, and more preferably 55%.

[0058] In the present invention, the alkaline activator includes fly ash and sodium hydroxide.

[0059] In the present invention, the mass ratio of the fly ash to sodium hydroxide is preferably 8 to 10:1, more preferably 8.5 to 9.5:1, and more preferably 9:1.

[0060] In the present invention, the siliceous reinforcing filler comprises silica fume modified by an aminosilane coupling agent.

[0061] In the present invention, the water reducer includes a polycarboxylate water reducer.

[0062] In the present invention, the chopped fibers include at least one of polyvinyl alcohol fibers, polyvinyl alcohol nitrile fibers, polypropylene fibers, glass fibers, basalt fibers and carbon fibers.

[0063] In the present invention, the length of the chopped fibers is preferably 3 to 6 mm, more preferably 3.5 to 5.5 mm, and even more preferably 4 to 5 mm.

[0064] The present invention also provides a method for preparing concrete made from recycled aggregate, comprising the following steps:

[0065] Mix quicklime, alkaline activator, siliceous reinforcing filler and water reducing agent, then add water and mix to obtain slurry;

[0066] After the slurry and the chopped fibers are mixed, the modified recycled aggregate is added and mixed to obtain a mixture;

[0067] The mixture is poured and cured to obtain concrete.

[0068] In the present invention, the curing temperature is preferably 25 to 30° C., more preferably 26 to 29° C., and more preferably 27 to 28° C.; the curing time is preferably 25 to 30 days, more preferably 27 to 29 days, and more preferably 28 days.

[0069] The present invention is further described in detail by way of examples. The raw materials used in the examples can be obtained through commercial sources.

[0070] In the following embodiments, the method for preparing silica fume modified by an aminosilane coupling agent comprises the following steps:

[0071] Silica fume (SiO 2 ≥90%) was immersed in 5% dilute hydrochloric acid (solid-liquid ratio 1:10), stirred at 60°C for 2h, then washed with deionized water until the pH of the filtrate was neutral, and then dried at 120°C to obtain pretreated silica ash;

[0072] γ-aminopropyltriethoxysilane (KH-550) was dropped into the water-ethanol mixture and magnetically stirred at 40°C for 30 h to obtain a hydrolyzate;

[0073] The pretreated silica ash was added into the hydrolyzate (solid-liquid ratio 1:15, the mass of γ-aminopropyltriethoxysilane in the hydrolyzate was 5% of the mass of the silica ash), and after ultrasonic dispersion (power 300 W, time 20 min), the mixture was stirred at a constant temperature of 75°C for 4 h. After the reaction, the silica ash modified with the aminosilane coupling agent was obtained by centrifugal separation and drying.

[0074] Example 1

[0075] A concrete prepared from recycled aggregate, comprising the following components in parts by weight:

[0076] 750 parts of quicklime, 550 parts of modified recycled aggregate, 155 parts of alkaline activator, 200 parts of silica fume modified by aminosilane coupling agent, 8 parts of polycarboxylate water reducer, 20 parts of chopped fibers and 200 parts of water;

[0077] The method for preparing the modified recycled aggregate comprises the following steps:

[0078] 8 parts of hydroxyethyl acrylate and 4 parts of sulfopropyl methacrylate were mixed, and the neutralization degree was adjusted to 70% with NaOH solution, and then 2 parts of hydroxypropyl methacrylate were added and mixed to obtain a mixed monomer solution;

[0079] 0.1 parts of initiator ammonium persulfate, 6 parts of nano-silica gel, N,N'-methylenebisacrylamide and water are mixed, ultrasonically vibrated to make them uniformly dispersed, and then added to the mixed monomer solution, and microwave polymerization is carried out at a power of 350W for 3 hours to obtain a gel material; wherein the amount ratio of hydroxyethyl acrylate, N,N'-methylenebisacrylamide and water is 8g:0.1g:5mL;

[0080] One part of recycled aggregate and two parts of gel material were mixed, and the mixture was cured at a temperature of 30° C. and a humidity of 50% for 24 hours to obtain modified recycled aggregate.

[0081] The alkaline activator includes fly ash and sodium hydroxide in a mass ratio of 10:1;

[0082] The chopped fibers included polyvinyl alcohol fibers having a length of 6 mm;

[0083] The method for preparing concrete made of recycled aggregate comprises the following steps:

[0084] Mix quicklime, alkaline activator, siliceous reinforcing filler and water reducing agent, then add water and mix to obtain slurry;

[0085] After the slurry and the chopped fibers are mixed, the modified recycled aggregate is added and mixed to obtain a mixture;

[0086] The mixture was poured and cured at 25°C for 28 days to obtain concrete.

[0087] Example 2

[0088] A concrete prepared from recycled aggregate, comprising the following components in parts by weight:

[0089] 800 parts of quicklime, 650 parts of modified recycled aggregate, 160 parts of alkaline activator, 220 parts of silica fume modified by aminosilane coupling agent, 10 parts of polycarboxylate water reducer, 25 parts of chopped fibers and 200 parts of water;

[0090] The method for preparing the modified recycled aggregate comprises the following steps:

[0091] Mix 5 parts of hydroxyethyl acrylate and 4 parts of sulfopropyl methacrylate, adjust the neutralization degree to 70% with NaOH solution, and then add 2 parts of hydroxypropyl methacrylate to mix, to obtain a mixed monomer solution;

[0092] 0.12 parts of initiator ammonium persulfate, 4 parts of nano-silica gel, N,N'-methylenebisacrylamide and water are mixed, ultrasonically vibrated to make them uniformly dispersed, and then added to the mixed monomer solution, and microwave polymerization is carried out at a power of 400 W for 4 hours to obtain a gel material; wherein the amount ratio of hydroxyethyl acrylate, N,N'-methylenebisacrylamide and water is 5:0.05g:5mL;

[0093] Mix 1 part of recycled aggregate and 1 to 3 parts of gel material, and cure them at a temperature of 25° C. and a humidity of 50° C. for 24 hours to obtain modified recycled aggregate.

[0094] The alkaline activator includes fly ash and sodium hydroxide in a mass ratio of 10:1;

[0095] The chopped fibers included polyvinyl alcohol fibers having a length of 6 mm;

[0096] The method for preparing concrete made of recycled aggregate comprises the following steps:

[0097] Mix quicklime, alkaline activator, siliceous reinforcing filler and water reducing agent, then add water and mix to obtain slurry;

[0098] After the slurry and the chopped fibers are mixed, the modified recycled aggregate is added and mixed to obtain a mixture;

[0099] The mixture was poured and cured at 25°C for 28 days to obtain concrete.

[0100] Example 3

[0101] A concrete prepared from recycled aggregate, comprising the following components in parts by weight:

[0102] 780 parts of quicklime, 630 parts of modified recycled aggregate, 160 parts of alkaline activator, 220 parts of silica fume modified by aminosilane coupling agent, 10 parts of polycarboxylate water reducer, 15 parts of chopped fibers and 250 parts of water;

[0103] The method for preparing the modified recycled aggregate comprises the following steps:

[0104] 10 parts of hydroxyethyl acrylate and 3 parts of sulfopropyl methacrylate were mixed, and the neutralization degree was adjusted to 70% with NaOH solution, and 1 part of hydroxypropyl methacrylate was added and mixed to obtain a mixed monomer solution;

[0105] 0.08 parts of initiator ammonium persulfate, 5 parts of nano-silica gel, N,N'-methylenebisacrylamide and water are mixed, ultrasonically vibrated to make them uniformly dispersed, and then added to the mixed monomer solution, and microwave polymerization is carried out at a power of 400 W for 3 hours to obtain a gel material; wherein the amount ratio of hydroxyethyl acrylate, N,N'-methylenebisacrylamide and water is 10g:0.1g:5mL;

[0106] 1 part of recycled aggregate and 1 to 3 parts of gel material are mixed, and the mixture is cured for 24 hours at a temperature of 25° C. and a humidity of 50% to obtain a modified recycled aggregate.

[0107] The alkaline activator includes fly ash and sodium hydroxide in a mass ratio of 10:1;

[0108] The chopped fibers included polyvinyl alcohol fibers having a length of 6 mm;

[0109] The method for preparing concrete made of recycled aggregate comprises the following steps:

[0110] Mix quicklime, alkaline activator, siliceous reinforcing filler and water reducing agent, then add water and mix to obtain slurry;

[0111] After the slurry and the chopped fibers are mixed, the modified recycled aggregate is added and mixed to obtain a mixture;

[0112] The mixture was poured and cured at 25°C for 28 days to obtain concrete.

[0113] Example 4

[0114] A concrete prepared from recycled aggregate, comprising the following components in parts by weight:

[0115] 700 parts of quicklime, 500 parts of modified recycled aggregate, 155 parts of alkaline activator, 210 parts of silica fume modified by aminosilane coupling agent, 10 parts of polycarboxylate water reducer, 20 parts of chopped fibers and 210 parts of water;

[0116] The method for preparing the modified recycled aggregate comprises the following steps:

[0117] 7 parts of hydroxyethyl acrylate and 3 parts of sulfopropyl methacrylate were mixed, and the neutralization degree was adjusted to 70% with NaOH solution, and 1 part of hydroxypropyl methacrylate was added and mixed to obtain a mixed monomer solution;

[0118] 0.12 parts of initiator ammonium persulfate, 6 parts of nano-silica gel, N,N'-methylenebisacrylamide and water are mixed, ultrasonically vibrated to make them uniformly dispersed, and then added to the mixed monomer solution, and microwave polymerization is carried out at a power of 300 W for 3 hours to obtain a gel material; wherein the amount ratio of hydroxyethyl acrylate, N,N'-methylenebisacrylamide and water is 7g:0.1g:5mL;

[0119] 1 part of recycled aggregate and 1 to 3 parts of gel material are mixed, and the mixture is cured for 24 hours at a temperature of 25° C. and a humidity of 50% to obtain a modified recycled aggregate.

[0120] The alkaline activator includes fly ash and sodium hydroxide in a mass ratio of 10:1;

[0121] The chopped fibers included polyvinyl alcohol fibers having a length of 6 mm;

[0122] The method for preparing concrete made of recycled aggregate comprises the following steps:

[0123] Mix quicklime, alkaline activator, siliceous reinforcing filler and water reducing agent, then add water and mix to obtain slurry;

[0124] After the slurry and the chopped fibers are mixed, the modified recycled aggregate is added and mixed to obtain a mixture;

[0125] The mixture was poured and cured at 25°C for 28 days to obtain concrete.

[0126] Comparative Example 1

[0127] A concrete prepared from recycled aggregate is the same as that in Example 1, except that the modified recycled aggregate is replaced by untreated recycled aggregate.

[0128] Comparative Example 2

[0129] A concrete prepared from recycled aggregate is the same as that in Example 1, except that no nano-silica gel is added in the preparation method of the modified recycled aggregate.

[0130] Comparative Example 3

[0131] A concrete prepared from recycled aggregate is the same as that in Example 1, except that the silica fume modified by aminosilane coupling agent is replaced by untreated silica fume.

[0132] Test Example 1

[0133] The 28d cubic compressive strength and splitting tensile strength of concrete were tested according to the mechanical properties test method in GB / T50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete". The test results are shown in Table 1.

[0134] Table 1

[0135] 28d compressive strength / MPa 28d splitting tensile strength / MPa Example 1 36.58 5.12 Example 2 34.27 4.92 Example 3 33.18 5.03 Example 4 35.30 5.08 Comparative Example 1 25.93 2.81 Comparative Example 2 29.45 3.25 Comparative Example 3 30.21 3.80

[0136] As can be seen from Table 1, the 28d compressive strength and splitting tensile strength of Examples 1-4 are significantly higher than those of Comparative Example 1, indicating that the modified recycled aggregate significantly improves the mechanical properties of concrete. Comparative Example 1 uses untreated recycled aggregate, and its compressive strength and splitting tensile strength are significantly lower, indicating that the modification of recycled aggregate is crucial to improving the performance of concrete. Comparative Example 2 does not add nano-silica gel, and its compressive strength and splitting tensile strength are lower than those of Example 1, indicating that nano-silica gel plays an important role in improving the performance of concrete. Comparative Example 3 uses untreated silica fume, and its compressive strength and splitting tensile strength are lower than those of Example 1, indicating that silica fume modified with aminosilane coupling agent can effectively improve the mechanical properties of concrete.

[0137] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A concrete prepared from recycled aggregate, characterized in that: The composition comprises the following components in parts by weight: 700-800 parts of quicklime, 500-650 parts of modified recycled aggregate, 150-160 parts of alkaline activator, 200-220 parts of siliceous reinforcing filler, 7-10 parts of water reducer, 15-25 parts of chopped fiber and 200-250 parts of water; The method for preparing the modified recycled aggregate comprises the following steps: Mixing hydroxyethyl acrylate and sulfopropyl methacrylate, adjusting the neutralization degree thereof with a NaOH solution, and then adding hydroxypropyl methacrylate to mix, thereby obtaining a mixed monomer solution; The initiator, nano-silica gel, N,N'-methylenebisacrylamide and water are mixed, dispersed and added into the mixed monomer solution to react and obtain a gel material; The recycled aggregate and the gel material are mixed and solidified to obtain the modified recycled aggregate.

2. The concrete prepared from recycled aggregate according to claim 1, characterized in that: The mass ratio of hydroxyethyl acrylate, sulfopropyl methacrylate and hydroxypropyl methacrylate is 5-10:2-4:1-2; The mass ratio of hydroxyethyl acrylate to initiator is 5-10:0.08-0.12; The mass ratio of hydroxyethyl acrylate to nano-silica aerogel is 5-10:4-6; The dosage ratio of the hydroxyethyl acrylate, N,N'-methylenebisacrylamide and water is 5-10 g: 0.05-0.1 g: 2.5-5 mL; The reaction method is microwave polymerization, the power of the microwave polymerization is 300-400W, and the time of the microwave polymerization is 2-4h.

3. The concrete made from recycled aggregate according to claim 1, characterized in that: The mass ratio of the recycled aggregate to the gel material is 1:1-3; The curing conditions are as follows: temperature of 20-30° C., time of 12-24 hours, and humidity of 50-60%.

4. The concrete made from recycled aggregate according to claim 1, characterized in that: The alkaline activator includes fly ash and sodium hydroxide; The mass ratio of the fly ash to sodium hydroxide is 8-10:

1.

5. The concrete made from recycled aggregate according to claim 1, characterized in that: The siliceous reinforcing filler comprises silica fume modified by an aminosilane coupling agent.

6. The concrete made from recycled aggregate according to claim 1, characterized in that: The water reducing agent includes a polycarboxylate water reducing agent.

7. The concrete made from recycled aggregate according to claim 1, characterized in that: The chopped fibers include at least one of polyvinyl alcohol fibers, polyvinyl alcohol nitrile fibers, polypropylene fibers, glass fibers, basalt fibers, and carbon fibers.

8. The concrete made from recycled aggregate according to claim 1, characterized in that: The length of the chopped fibers is 3 to 6 mm.

9. The method for preparing concrete made from recycled aggregate according to any one of claims 1 to 8, characterized in that: The following steps are involved: Mix quicklime, alkaline activator, siliceous reinforcing filler and water reducing agent, then add water and mix to obtain slurry; After the slurry and the chopped fibers are mixed, the modified recycled aggregate is added and mixed to obtain a mixture; The mixture is poured and cured to obtain concrete.

10. The method for preparing concrete made from recycled aggregate according to claim 9, characterized in that: The curing temperature is 25-30° C., and the curing time is 25-30 days.