Multi-generation cyclically renewable anti-freezing concrete and preparation method thereof

Abstract

The application discloses a kind of anti-freezing concrete and preparation method of multi-generation recycling, the concrete is by following raw material is formed according to weight parts: cement 405~418 parts, nano silicon dioxide 8~20 parts, river sand 680~735 parts, recycled coarse aggregate 865~890 parts, water 168~194 parts, polycarboxylate superplasticizer 2.2 parts and alkyl benzene sulfonate air entraining agent 0.05~0.1 parts.The application uses nano silicon dioxide as raw material, which has high specific surface area and pozzolanic activity, and the alkyl benzene sulfonate air entraining agent reduces the aggregation of nano silicon dioxide, not only promotes its uniform dispersion in concrete, but also makes the pore distribution in concrete uniform, thereby improving the mechanical properties and frost resistance of concrete, and the second generation and third generation recycled coarse aggregate obtained by crushing after 400 freeze-thaw cycles can be used in structural concrete in cold regions, greatly reducing material waste and environmental pollution.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of building materials, and particularly relates to a multi-generation recyclable anti-freezing recycled concrete and a preparation method thereof. BACKGROUND

[0002] Concrete is the main material in construction engineering, but it is prone to cracking damage due to freeze-thaw in cold regions. In addition, the large amount of waste concrete also brings pollution and waste to the environment. In order to solve these problems, recycled concrete gradually rises. Recycled concrete is prepared by recycling and reusing waste concrete, which can fully utilize resources, reduce waste and pollution, reduce construction cost and realize sustainable development.

[0003] However, the performance of recycled concrete is often worse than that of traditional concrete, such as low strength, poor durability, easy cracking, etc., which limits the application range of recycled concrete. In order to improve the performance of recycled concrete, people began to study how to use nanomaterials to improve the performance of concrete. Nanomaterials have special physical and chemical properties, which can improve the performance of concrete by adjusting its morphology, size, surface properties, etc. Nanosilica is a commonly used nanomaterial, which has extremely small particle size and large specific surface area, and can play a filling and reinforcing role in concrete, while also improving the durability and frost resistance of concrete. Therefore, the application of nanosilica in the preparation of recycled concrete can effectively improve the performance of recycled concrete, reduce cost and realize sustainable development.

[0004] Patent document CN108164208A introduces a kind of nanosilica recycled concrete, by controlling stirring time makes nanosilica completely dispersed, utilizes its high pozzolanic activity to improve the mechanical properties and physical properties of recycled concrete, but the frost resistance of nanosilica recycled concrete is not mentioned.

[0005] Patent document CN114656208A introduces a kind of recycled concrete that can be recycled in severe cold regions, uses fly ash and silica ash two mineral admixtures to partially replace cement, and mixes natural coarse aggregate with recycled coarse aggregate to prepare recycled concrete. This method still needs to use natural coarse aggregate resources, and the cost is relatively high.

[0006] The performance of recycled concrete prepared by using recycled coarse aggregate to completely replace natural coarse aggregate in the prior art is difficult to meet the multi-generation recycling for structural concrete after 400 freeze-thaw cycles. SUMMARY

[0007] This section is intended to summarize some aspects of the embodiments of the present application and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the Abstract and Title of the specification to avoid obscuring the purpose of this section, the Abstract and the Title, which are to summarize some aspects of the embodiments of the present application. Such simplifications or omissions are not intended to limit the scope of the present application.

[0008] In view of the above and / or problems existing in the prior art, the present application is proposed.

[0009] Therefore, the purpose of the present application is to overcome the deficiencies in the prior art, and to provide a multi-generation recycled anti-freezing concrete.

[0010] To solve the above technical problems, the present application provides the following technical solutions: comprising,

[0011] Cement, nano-silicon dioxide, river sand, recycled coarse aggregate, water, polycarboxylate superplasticizer and alkyl benzene sulfonate air entraining agent;

[0012] The mass ratio of the nano-silicon dioxide to the alkyl benzene sulfonate air entraining agent is 150-250.

[0013] As a preferred scheme of the multi-generation recycled anti-freezing concrete, in mass parts, the concrete comprises,

[0014] Cement 405-418 parts, nano-silicon dioxide 8-20 parts, river sand 680-735 parts, recycled coarse aggregate 865-890 parts, water 168-194 parts, polycarboxylate superplasticizer 2.2 parts and alkyl benzene sulfonate air entraining agent 0.05-0.1 parts.

[0015] As a preferred scheme of the multi-generation recycled anti-freezing concrete, the cement is ordinary portland cement P.O42.5, and the specific surface area is >300m 2 / kg.

[0016] As a preferred scheme of the multi-generation recycled anti-freezing concrete, the particle size of the nano-silicon dioxide is 5-20nm, and the specific surface area is >400m 2 / kg.

[0017] As a preferred scheme of the multi-generation recycled anti-freezing concrete, the recycled coarse aggregate is type II recycled coarse aggregate specified in GB / T25177-2010, the apparent density is 2423kg / m 3 , the water absorption is 4.05%, the crushing value is 15%, and the particle size is 5-20mm.

[0018] As a preferred scheme of the anti-freezing concrete capable of multi-generation recycling, the water-reducing rate of the polycarboxylate water-reducing agent is 30-50%.

[0019] As a preferred scheme of the anti-freezing concrete capable of multi-generation recycling, the air entraining amount of the alkyl benzene sulfonate air entraining agent is 1.4-1.8 L / g.

[0020] Another object of the present application is to provide a preparation method of the anti-freezing concrete capable of multi-generation recycling.

[0021] To solve the above technical problems, the present application provides the following technical scheme: comprising,

[0022] The raw material components are weighed according to the formula;

[0023] The nanometer silicon dioxide and the alkyl benzene sulfonate air entraining agent are sequentially poured into water and fully stirred until completely dispersed, and then the polycarboxylate water-reducing agent is added and stirred uniformly to form a mixed solution;

[0024] Half of the weight part of the cement and half of the mixed solution are poured into a stirrer to form a slurry;

[0025] The recycled coarse aggregate is poured into the stirrer to stir, so that the slurry is wrapped on the surface of the recycled coarse aggregate;

[0026] Finally, the river sand, the other half of the weight part of the cement and the remaining mixed solution are poured into the stirrer to stir and form a mixture, which is poured into a mold to be shaped, demolded and maintained to obtain the anti-freezing concrete capable of multi-generation recycling.

[0027] Another object of the present application is to provide a multi-generation recycling method of the anti-freezing concrete.

[0028] To solve the above technical problems, the present application provides the following technical scheme: comprising,

[0029] The anti-freezing concrete prepared by the preparation method is a first-generation recycled concrete, which is crushed after freeze-thaw, and the aggregate with a particle size of 5-20 mm is screened out, that is, a second-generation recycled coarse aggregate, which is recycled as the recycled coarse aggregate in the formula of the anti-freezing concrete to prepare a second-generation anti-freezing concrete.

[0030] The second-generation anti-freezing concrete is crushed after freeze-thaw, and the aggregate with a particle size of 5-20 mm is screened out, that is, a third-generation recycled coarse aggregate, which is recycled as the recycled coarse aggregate in the formula of the anti-freezing concrete to prepare a third-generation anti-freezing concrete.

[0031] As a preferred scheme of the multi-generation cyclic recycling method of the anti-freezing concrete, the anti-freezing concrete has the following advantages: the compressive strength of the second-generation concrete decreases by less than 4% compared with that of the first-generation concrete, the compressive strength of the third-generation concrete decreases by less than 5% compared with that of the second-generation concrete, and the mass loss rate of the third-generation concrete is less than 2% after 400 freeze-thaw cycles, so that the anti-freezing concrete has excellent mechanical properties, anti-freezing properties and cyclic recycling properties.

[0032] The present application has the following advantages:

[0033] (1) The present application provides an anti-freezing concrete which can be recycled for multiple generations, wherein the compressive strength of the second-generation concrete decreases by less than 4% compared with that of the first-generation concrete, the compressive strength of the third-generation concrete decreases by less than 5% compared with that of the second-generation concrete, and the mass loss rate of the third-generation concrete is less than 2% after 400 freeze-thaw cycles, so that the anti-freezing concrete has excellent mechanical properties, anti-freezing properties and cyclic recycling properties.

[0034] (2) The anti-freezing concrete prepared by the present application has the performance of the second-generation and third-generation recycled coarse aggregate meeting the requirements of Class III, and can be used for structural concrete, so that the recycling of waste concrete can be realized and the environmental pollution can be reduced. BRIEF DESCRIPTION OF DRAWINGS

[0035] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the following embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor. Among them:

[0036] Figure 1 The figure is a multi-generation cyclic recycling diagram of the nano-silica recycled concrete in the embodiment of the present application DETAILED DESCRIPTION

[0037] In order to make the above-mentioned purposes, features and advantages of the present application more apparent and easy to understand, the specific embodiments of the present application will be described in detail in the following description.

[0038] In the following description, many specific details are set forth in order to provide a thorough understanding of the present application, but the present application can also be implemented in other ways different from those described herein, and those skilled in the art can make similar generalizations without departing from the scope of the present application, therefore the present application is not limited to the specific embodiments disclosed below.

[0039] Secondly, the "one embodiment" or "embodiment" referred to herein means a specific feature, structure, or characteristic that can be included in at least one implementation of the present application. The "in one embodiment" appearing in various places in the specification does not all refer to the same embodiment, nor does it necessarily refer to a single or particular embodiment, or a particular implementation, or a particular feature, nor does it exclude other embodiments or implementations.

[0040] The performance index of the present application is determined by the following method:

[0041] The compressive strength test of the concrete is carried out according to the Standard for Testing Methods of Mechanical Properties of Ordinary Concrete GB / T 50081-2019;

[0042] The mass loss rate and relative dynamic elastic modulus of the concrete are determined according to the Standard for Testing Methods of Long-term Performance and Durability of Ordinary Concrete GB / T 50082-2009;

[0043] The apparent density, water absorption rate and crushing value of the recycled coarse aggregate are determined according to the Recycled Coarse Aggregate for Concrete GB / T 25177-2010.

[0044] The freeze-thaw cycle test method in the present application is the fast-moving method;

[0045] The raw materials used in the present application are:

[0046] The cement is ordinary Portland cement P.O42.5, and the specific surface area is >300m 2 / kg;

[0047] The particle size of the nano-silicon dioxide is 5-20nm, and the specific surface area is >400m 2 / kg;

[0048] The recycled coarse aggregate is the type II recycled coarse aggregate specified in GB / T 25177-2010, and the apparent density is 2423kg / m 3 , the water absorption rate is 4.05%, the crushing value is 15%, and the particle size is 5-20mm;

[0049] The water-reducing rate of the polycarboxylic acid water-reducing agent is 40%;

[0050] The air entraining agent of alkyl benzene sulfonate is dodecyl benzene sulfonate, and the air entraining amount is 1.6L / g;

[0051] Example 1

[0052] The present embodiment provides a preparation method of freeze-resistant concrete and a recycling method thereof;

[0053] 1) Preparation of the first-generation freeze-resistant concrete:

[0054] The following raw material components are weighed according to the formula:

[0055] Cement 413 parts, nano-silica 16 parts, river sand 690 parts, recycled coarse aggregate 875 parts, water 175 parts, polycarboxylate superplasticizer 2.2 parts and dodecyl benzene sulfonate air entraining agent 0.07 parts.

[0056] The nano-silica and dodecyl benzene sulfonate air entraining agent were sequentially poured into water and stirred until the liquid surface was free of nano-silica suspension, and then the polycarboxylate superplasticizer was poured into the mixture and stirred uniformly to form a mixed liquid;

[0057] Half of the weight of the cement and half of the mixed liquid were poured into a blender and stirred for 60 s to form a slurry;

[0058] The recycled coarse aggregate was poured into the blender and stirred for 60 s to allow the slurry to coat the surface of the recycled coarse aggregate;

[0059] Finally, the river sand, the other half of the weight of the cement and the remaining mixed liquid were poured into the blender and stirred for 90-120 s to form a mixture, which was poured into a mold for 24 h molding, demolding, high-temperature water curing, and the first generation of frost-resistant concrete specimens were placed in a high-temperature curing oven at 85°C for 5 d, and then placed in a standard curing room after the high-temperature water curing was completed.

[0060] 2) Preparation of the second generation of frost-resistant concrete:

[0061] After the first generation of concrete obtained in step 1) was subjected to freeze-thaw cycle test for 400 times, it was crushed by a jaw crusher in two stages, and the recycled coarse aggregate with a particle size of 5-20 mm was sieved out to obtain the second generation of recycled coarse aggregate;

[0062] The second generation of recycled coarse aggregate was used as recycled coarse aggregate again for the preparation of concrete, and the formulation and preparation process were consistent with step 1), and the second generation of frost-resistant concrete was prepared.

[0063] 3) Preparation of the third generation of frost-resistant concrete:

[0064] After the second generation of frost-resistant concrete obtained in step 2) was subjected to freeze-thaw cycle test for 400 times, it was crushed by a jaw crusher in two stages, and the recycled coarse aggregate with a particle size of 5-20 mm was sieved out to obtain the third generation of recycled coarse aggregate;

[0065] The third generation of recycled coarse aggregate was used as recycled coarse aggregate again for the preparation of concrete, and the formulation and preparation process were consistent with step 1), and the third generation of frost-resistant concrete was prepared.

[0066] Example 2

[0067] The difference between this example and example 1 is that the formulation of the raw materials of the concrete is adjusted, specifically:

[0068] Cement 418 parts, nano-silica 8 parts, river sand 680 parts, recycled coarse aggregate 890 parts, water 168 parts, polycarboxylic acid water reducer 2.2 parts, and dodecyl benzene sulfonate air entraining agent 0.05 parts.

[0069] The remaining preparation method and recycling method are the same as in Example 1.

[0070] Example 3

[0071] The difference between this example and Example 1 is that the raw material formula of the concrete is adjusted, specifically:

[0072] Cement 415 parts, nano-silica 13 parts, river sand 715 parts, recycled coarse aggregate 882 parts, water 185 parts, polycarboxylic acid water reducer 2.2 parts, and dodecyl benzene sulfonate air entraining agent 0.07 parts.

[0073] The remaining preparation method and recycling method are the same as in Example 1.

[0074] Example 4

[0075] The difference between this example and Example 1 is that the raw material formula of the concrete is adjusted, specifically:

[0076] Cement 405 parts, nano-silica 20 parts, river sand 735 parts, recycled coarse aggregate 865 parts, water 173 parts, polycarboxylic acid water reducer 2.2 parts, and dodecyl benzene sulfonate 0.1 parts.

[0077] The remaining preparation method and recycling method are the same as in Example 1.

[0078] The properties of the recycled coarse aggregate of each generation in the above Examples 1 to 4 were measured, and the results are shown in Tables 1 and 2.

[0079] Table 1 Second-generation recycled coarse aggregate

[0080]

[0081] Table 2 Third-generation recycled coarse aggregate

[0082]

[0083] From the table 1, table 2 can see, the second generation and the third generation of recycled coarse aggregate performance prepared by the method of the application all meet the above standard of the III class in the "recycled coarse aggregate for concrete GB / T25177-2010", can be used for preparing structural concrete again, with the increase of the proportion of nano-silicon dioxide in cement, the strength and the frost resistance of the first generation and the second generation of nano-silicon dioxide recycled concrete are improved, but the inventors find that with the further increase of the content of nano-silicon dioxide, the concrete mixture becomes viscous, the slump is decreased significantly, which affects the actual construction and reliability, so the content of nano-silicon dioxide is not tried to be further increased under the condition of meeting the concrete standard.

[0084] The performance of each generation of concrete in the above embodiments 1-4 is determined, and the results are shown in tables 3-5.

[0085] Table 3: Comparison of compressive strength of three generations of concrete

[0086]

[0087]

[0088] From table 3, it can be seen that the three generations of concrete all have excellent compressive strength, and the compressive strength of each generation decreases by less than 5%.

[0089] Table 4: Comparison of mass loss rate of three generations of concrete

[0090] First generation concrete / % Second generation concrete / % Third generation concrete % Example 1 1.01 1.21 1.42 Example 2 1.56 1.68 1.78 Example 3 1.24 1.53 1.67 Example 4 0.98 1.20 1.39

[0091] From table 4, it can be seen that the mass loss of the frost-resistant concrete of the application after two generations of recycling is still 2%, which has good durability.

[0092] Table 5: Comparison of relative dynamic elastic modulus of three generations of concrete

[0093] First generation concrete / % Second generation concrete / % Third generation concrete / % Example 1 80.25 79.53 68.75 Example 2 68.68 65.12 60.13 Example 3 75.16 69.23 61.67 Example 4 81.78 72.18 63.12

[0094] From table 5, it can be seen that the relative dynamic elastic modulus of the frost-resistant concrete of the application after two generations of recycling is still 2%, which has good frost resistance and durability.

[0095] The nano-silicon dioxide in the formula of the present application can react with Ca(OH)2 generated by cement hydration to generate C-S-H gel as a crystal nucleus. Due to the high chemical reactivity and surface area of the surface of the nano-silicon dioxide, the nano-silicon dioxide can adsorb calcium ions and water in the cement, promote the formation and crystal growth of C-S-H gel, fill the micro-pores in the recycled concrete, form a three-dimensional space firm and dense whole, optimize the internal pore structure, effectively hinder the penetration of external moisture, significantly improve the frost resistance of the recycled concrete, and the recycled coarse aggregate obtained by crushing the first generation of recycled concrete has some cracks and voids. The nano-silicon dioxide has a filling effect and can make up for these deficiencies. In addition, the surface of the recycled coarse aggregate is left with part of Ca(OH)2, and the nano-silicon dioxide can react with it to further improve the physical properties of the recycled coarse aggregate, so that the second generation of recycled concrete prepared has good mechanical properties and frost resistance, and the third generation of recycled coarse aggregate can still be recycled.

[0096] The compressive strength of the first and second generation of recycled concrete prepared by the present application is greater than 40 MPa, the mass loss after 400 freeze-thaw cycles is less than 2%, and the relative dynamic elastic modulus is greater than 65%, which has excellent mechanical properties and frost resistance. Among them, the performance of the formula of Example 4 is the best, and even the mechanical properties and frost resistance of the second and third generations of concrete under this formula can be better than those of the first generation of concrete under other formulas, which shows that the present application realizes the improvement of the mechanical properties and frost resistance of the concrete itself while realizing the improvement of the cycle stability.

[0097] Comparative Example 1

[0098] The difference between this comparative example and Example 4 is that the nano-silicon dioxide in the raw material formula is adjusted to silica fume, specifically:

[0099] Cement 413 parts, ordinary silica fume 20 parts, river sand 690 parts, recycled coarse aggregate 875 parts, water 175 parts, polycarboxylic acid water reducer 2.2 parts and dodecyl benzene sulfonate air entraining agent 0.01 parts.

[0100] The rest of the preparation method and recycling method are the same as those of Example 4.

[0101] Comparative Example 2

[0102] The difference between this comparative example and Example 1 is that the type of air entraining agent is adjusted to rosin air entraining agent, specifically:

[0103] Cement 413 parts, nano-silicon dioxide 20 parts, river sand 690 parts, recycled coarse aggregate 875 parts, water 175 parts, polycarboxylic acid water reducer 2.2 parts and rosin air entraining agent 0.01 parts.

[0104] The rest of the preparation method and recycling method are the same as those of Example 4.

[0105] Comparative Example 3

[0106] The difference between this comparative example and Example 4 is that the ratio of nano-silica to dodecyl benzene sulfonate in the raw material formula of the concrete is adjusted to 300:1, specifically:

[0107] cement 405 parts, nano-silica 30 parts, river sand 735 parts, recycled coarse aggregate 865 parts, water 173 parts, polycarboxylate superplasticizer 2.2 parts, and dodecyl benzene sulfonate 0.1 part.

[0108] The rest of the preparation method and the recycling method are the same as those of Example 4.

[0109] Comparative Example 4

[0110] The difference between this comparative example and Example 4 is that the ratio of nano-silica to dodecyl benzene sulfonate in the raw material formula of the concrete is adjusted to 100:1, specifically:

[0111] cement 405 parts, nano-silica 20 parts, river sand 735 parts, recycled coarse aggregate 865 parts, water 173 parts, polycarboxylate superplasticizer 2.2 parts, and dodecyl benzene sulfonate 0.2 part.

[0112] The rest of the preparation method and the recycling method are the same as those of Example 4.

[0113] The properties of the recycled coarse aggregate of each generation in the above Comparative Examples 1-4 were determined and compared with Example 4, and the results are shown in Tables 6 and 7.

[0114] Table 6 Second-generation recycled coarse aggregate

[0115]

[0116] Table 7 Third-generation recycled coarse aggregate

[0117]

[0118] As can be seen from Tables 6 and 7, the recycled aggregate prepared in the comparative examples does not meet the Class II standard of recycled coarse aggregate, and is close to the minimum standard of Class III. The performance of the third-generation recycled aggregate in Comparative Example 2 cannot meet the Class III standard, indicating that only the nano-silica recycled concrete prepared according to the formula of the present application can achieve multiple cycles of use in cold regions.

[0119] The properties of the concrete of each generation in the above Comparative Examples 1-4 were determined and compared with Example 4, and the results are shown in Tables 8-10.

[0120] Table 8 Comparison of compressive strength of third-generation concrete

[0121]

[0122]

[0123] Table 9 Comparison of mass loss rate of three generations of concrete

[0124] First generation concrete / % Second generation concrete / % Third generation concrete % Example 4 0.98 1.20 1.39 Comparative Example 1 2.53 2.78 3.04 Comparative Example 2 2.89 2.96 3.23 Comparative Example 3 2.62 2.83 3.11 Comparative Example 4 2.74 2.87 3.19

[0125] Table 10 Comparison of relative dynamic elastic modulus of three generations of concrete

[0126] First generation concrete / % Second generation concrete / % Third generation concrete / % Example 4 81.78 72.18 63.12 Comparative Example 1 67.95 63.33 49.25 (failed) Comparative Example 2 61.36 57.62 (failed) 42.24 (failed) Comparative Example 3 64.56 60.75 47.32 (failed) Comparative Example 4 62.47 59.31 (failed) 43.89 (failed)

[0127] As can be seen from Tables 8-10, the interaction of nano-silica and alkyl benzene sulfonate air entraining agent in the present application has a significant effect on the technical effect. This is because nano-silica is easy to aggregate in water, and the alkyl benzene sulfonate air entraining agent is a hydrophilic molecule, which has both hydrophilic groups and hydrophobic groups in its molecular structure, which allows them to form a layer of hydrophilic molecular film on the surface of nano-silica, while the hydrophobic groups are outward, forming a hydrophobic environment. This structure can effectively reduce the electrostatic interaction between nano-silica, thereby preventing the aggregation and precipitation of nano-silica, achieving the effect of dispersion stability, allowing nano-silica to fully play its role, and thus improving the comprehensive performance of recycled concrete.

[0128] In addition, the silicate substance formed by the interaction of nano-silica and dodecyl benzene sulfonate can react with cement colloid to form more hardened products, increasing the strength and durability of concrete. Furthermore, it can also reduce the expansion and shrinkage of water in concrete during freeze-thaw cycles, thereby improving the frost resistance of concrete. The ratio of the two is the key to achieving the technical effect. For example, the performance of the concrete prepared by adjusting the ratio in Comparative Examples 3 and 4 is decreased.

[0129] In Comparative Example 1, silica fume is used as the raw material. On the one hand, the particle size of silica fume is generally greater than 0.1 μm, which can only fill pores greater than 0.1 μm of capillary pores and cracks, while nano-silica can fill smaller micro-cracks and pores. On the other hand, silica fume can only have a physical adsorption reaction with dodecyl benzene sulfonate, and dodecyl benzene sulfonate only acts as an air entraining agent to improve the fluidity of concrete in the overall concrete system, having little effect on the overall mechanical properties and frost resistance. Similarly, replacing dodecyl benzene sulfonate with other types of air entraining agents in Comparative Example 2 also cannot achieve the technical effect of the present application.

[0130] To sum up, the anti-freezing concrete prepared by the application can be recycled and reused for multiple generations, wherein the compressive strength of the second-generation concrete decreases by less than 4% compared to that of the first-generation concrete, the compressive strength of the third-generation concrete decreases by less than 5% compared to that of the second-generation concrete, and the mass loss rate of the third-generation concrete is less than 2% after 400 freeze-thaw cycles, and the anti-freezing concrete has excellent mechanical properties, anti-freezing properties and recyclable performance.

[0131] The anti-freezing concrete prepared by the application has the performance of the second-generation and third-generation recycled coarse aggregate meeting the requirements of type III, and can be used for structural concrete, so that the recycled use of waste concrete can be realized, and the environmental pollution can be reduced, and the natural resources can be protected.

[0132] It should be noted that the above examples are only used to illustrate the technical solutions of the application and are not limiting, and although the application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the application can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the application, and they should be covered in the scope of the claims of the application.

Claims

1. A freeze-resistant concrete that can be recycled and reused for multiple generations, characterized by: The concrete comprises, in mass fraction, cement 405-418 parts, nano-silica 8-20 parts, river sand 680-735 parts, recycled coarse aggregate 865-890 parts, water 168-194 parts, polycarboxylate superplasticizer 2.2 parts, and alkyl benzene sulfonate air entraining agent 0.05-0.1 parts; The mass ratio of the nano-silica to the alkyl benzene sulfonate air entraining agent is 150-250.

2. The freeze-resistant concrete according to claim 1, wherein: The cement is ordinary Portland cement P.O 42.5 with a specific surface area > 300 m 2 / kg.

3. The freeze-resistant concrete according to claim 1, wherein: The nano-silica has a particle size of 5-20 nm, a specific surface area of >400 m 2 / kg.

4. The freeze-resistant concrete that can be recycled and reused for multiple generations according to claim 1, characterized in that: The recycled coarse aggregate is a II type recycled coarse aggregate specified in GB / T25177-2010, with an apparent density of 2423 kg / m 3 , a water absorption of 4.05%, a crushing value of 15%, and a particle size of 5-20 mm.

5. The freeze-resistant concrete that can be recycled and reused for multiple generations according to claim 1, characterized in that: The polycarboxylate superplasticizer has a water-reducing rate of 30-50%.

6. The freeze-resistant concrete that can be recycled and reused for multiple generations according to claim 1, characterized in that: The alkyl benzene sulfonate air entraining agent includes dodecyl benzene sulfonate, and has an air entraining amount of 1.4-1.8 L / g.

7. The method for preparing the freeze-resistant concrete capable of being recycled and reused for multiple generations according to any one of claims 1 to 6, characterized in that: The method comprises the steps of: The components are weighed according to the formula; The nano-silica and the alkyl benzene sulfonate air entraining agent are sequentially poured into water and fully stirred to be completely dispersed, and then the polycarboxylate superplasticizer is added and uniformly stirred to form a mixed solution; Half of the cement and half of the mixed solution are poured into a stirrer to form a slurry; The recycled coarse aggregate is poured into the stirrer to stir, so that the slurry is wrapped on the surface of the recycled coarse aggregate; Finally, the river sand, the other half of the cement, and the remaining mixed solution are poured into the stirrer to form a mixture, which is poured into a mold to be shaped, demolded, and maintained to obtain the anti-freezing concrete which can be recycled and utilized for multiple generations.

8. A method for multi-generation recycling of frost-resistant concrete prepared by the method described in claim 7, characterized in that: The method comprises the steps of: The anti-freezing concrete prepared by the method is a first-generation concrete, which is crushed after freeze-thaw, and the aggregate with a particle size of 5-20 mm is screened out, which is a second-generation recycled coarse aggregate, and is reused as the recycled coarse aggregate in the formula of the anti-freezing concrete to prepare a second-generation anti-freezing concrete; The second-generation anti-freezing concrete is crushed after freeze-thaw, and the aggregate with a particle size of 5-20 mm is screened out, which is a third-generation recycled coarse aggregate, and is reused as the recycled coarse aggregate in the formula of the anti-freezing concrete to prepare a third-generation anti-freezing concrete.

9. The method of claim 8, wherein the method is a multi-generation recycling method of anti-frozen concrete. The compressive strength of the second-generation concrete decreases by less than 4% compared with that of the first-generation concrete, and the compressive strength of the third-generation concrete decreases by less than 5% compared with that of the second-generation concrete, and the mass loss rate of the third-generation concrete is less than 2% after 400 freeze-thaw cycles, and the third-generation concrete has excellent mechanical properties, anti-freezing properties, and recyclable performance.

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