Environment-friendly concrete based on building waste and production method

Abstract

The invention relates to environment-friendly concrete based on building waste and a production method. The environment-friendly concrete is prepared from the following raw materials: cement, river sand, modified regenerated building waste, fly ash, water, a water reducing agent, epoxy resin and an alcohol amine compound. Wherein the modified regenerated building waste is obtained by sequentially carrying out carbonization treatment on regenerated building waste, immersing the regenerated building waste into a nano silicon dioxide aqueous dispersion liquid for freezing and melting circulation treatment and carrying out surface amination treatment. The internal structure of the regenerated building waste is optimized, so that the strength of the regenerated building waste is improved, the high-strength, low-bleeding and environment-friendly concrete material is developed, and recycling of the regenerated building waste is promoted.

Description

Technical Field

[0001] The present invention belongs to the technical field of building materials, and in particular relates to an environmentally friendly concrete based on construction waste and a production method thereof. Background Art

[0002] The demolition of old buildings generates large amounts of construction waste, primarily waste concrete. This bulky construction waste is difficult to degrade and represents a reusable building resource. The secondary use of this waste concrete to produce recycled coarse aggregate can partially replace natural aggregate, reduce the mining of natural sand and gravel, and achieve the recycling of domestic and construction waste. However, recycled aggregate has a high water absorption rate, high porosity, and a rough surface, resulting in poor fluidity in the recycled concrete mix. Furthermore, concrete prepared with recycled aggregate is typically weaker in strength than conventional concrete and exhibits poor durability. To promote its further application and development in concrete preparation, it is necessary to modify the recycled aggregate.

[0003] The current common treatment method is to add fly ash, cement and other materials that can react chemically with calcium hydroxide during hydration to generate compounds with hydraulic cementing properties that will be coated on the surface of the recycled coarse aggregate, thereby achieving the purpose of reducing the porosity and water absorption of the recycled coarse aggregate. However, this surface coating modification treatment method has limited strengthening effect and also destroys the water retention of the recycled aggregate to a certain extent. The water retention of concrete is also an important component of the workability of concrete, and has an important impact on the construction quality, strength development and durability of concrete. Summary of the Invention

[0004] The purpose of the present invention is to provide an environmentally friendly concrete based on construction waste and a production method in order to solve the above problems.

[0005] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0006] As one aspect of the present invention, the present invention provides an environmentally friendly concrete based on construction waste, comprising the following raw materials: cement, river sand, modified recycled construction waste, fly ash, water, water reducer, epoxy resin and amine compound; wherein the modified recycled construction waste is obtained by subjecting the recycled construction waste to carbonization treatment, immersing it in an aqueous dispersion of nano-silicon dioxide for freeze-thaw cycle treatment and surface amination treatment.

[0007] As a further optimization scheme of the present invention, the environmentally friendly concrete includes, by weight, 250-300 parts of cement, 500-800 parts of river sand, 900-1200 parts of modified recycled construction waste, 80-100 parts of fly ash, 150-160 parts of water, 4-6 parts of water reducer, 80-100 parts of epoxy resin and 8-12 parts of alcoholamine compound.

[0008] As a further optimized solution of the present invention, the alcoholamine compound is one of diethanolamine or triethanolamine.

[0009] As a further optimization solution of the present invention, the particle size of the modified recycled construction waste is 5mm-30mm.

[0010] As a further optimized solution of the present invention, the nano-silicon dioxide aqueous dispersion is obtained by first adding nano-silicon dioxide into deionized water and stirring evenly, and then adding sodium lauryl sulfate and subjecting to ultrasonic dispersion treatment.

[0011] As another aspect of the present invention, there is also provided a method for producing the above-mentioned environmentally friendly concrete, comprising the following steps:

[0012] (1) The recycled construction waste is first subjected to carbonization treatment, then immersed in a nano-silica aqueous dispersion for freeze-thaw cycle treatment, and finally subjected to surface amination treatment to obtain modified recycled construction waste;

[0013] (2) According to the formula, cement, river sand, modified recycled construction waste, fly ash, water, water reducer and epoxy resin are first mixed evenly, and then the alcohol amine compound is added and mixed evenly under alkaline conditions.

[0014] As a further optimization scheme of the present invention, in step (1), the immersion time of the recycled aggregate in the aqueous dispersion of nano-silica is 2 days to 4 days, the freezing end temperature is -18°C to -20°C, the freezing time is 1 hour to 2 hours, the melting end temperature is 8°C to 10°C, and the melting time is 1 hour to 2 hours.

[0015] As a further optimization solution of the present invention, in step (1), the number of freeze-thaw cycle treatments is 5-10 times.

[0016] As a further optimization scheme of the present invention, in step (1), the process parameters of the carbonization treatment are: pressure of 0.1 MPa, humidity of 70%±5%, temperature of 20°C±2°C, and carbon dioxide concentration of 25%±2%.

[0017] As a further optimization scheme of the present invention, in step (1), the surface amination treatment is to disperse the carbonized recycled construction waste in ethanol, add aminosilane coupling agent and deionized water, stir and filter out the liquid.

[0018] The working principle of the present invention is that the present invention uses recycled construction waste as recycled coarse aggregate to partially replace natural aggregate. In order to solve the problems of high water absorption and low strength of recycled construction waste, the present invention modifies it. Specifically, the recycled construction waste is first carbonized to optimize the pore structure of the recycled construction waste. The carbonized product produced by the carbonization treatment is filled into the pore structure, thereby improving the pore structure and strengthening the structure. The recycled construction waste is then subjected to a freeze-thaw cycle treatment. The frost heave force generated when water freezes is used to generate microcracks inside the waste, thereby promoting the filling effect of nano-silica in the recycled construction waste and forming a multi-stage strengthening effect. Finally, the surface of the recycled construction waste is subjected to an amination treatment to graft active amino groups on the surface of the recycled construction waste. The presence of the active amino groups allows the epoxy groups of the epoxy resin to react with the active amino groups on the surface of the recycled construction waste and the amino groups of the diethanolamine under alkaline conditions during concrete mixing to form a coating that can reduce the entry of moisture into the interior of the modified recycled construction waste, thereby reducing the water bleeding rate of the concrete as a whole.

[0019] The beneficial effects of the present invention are as follows: the environmentally friendly concrete provided by the present invention includes cement, river sand, modified recycled construction waste, fly ash, water, water reducing agent, epoxy resin and alcohol amine compound. By sequentially subjecting the recycled construction waste to a three-step modification method of carbonization treatment, freeze-thaw cycle treatment and surface amino acid treatment, the internal structure of the recycled construction waste is optimized and its strength is improved. In addition, a high-strength, low-bleeding and environmentally friendly concrete material is developed using the modified recycled construction waste, thereby promoting the recycling and utilization of recycled construction waste. DETAILED DESCRIPTION

[0020] The present invention is described in further detail below. It is necessary to point out that the following specific implementation methods are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above application content.

[0021] In the following examples, the reagents and materials used, unless otherwise specified, were commercially available.

[0022] The cement is selected to be silicate cement, but is not limited thereto.

[0023] Modified recycled construction waste is recycled aggregate obtained by recycling waste concrete. The means of preparing recycled aggregate through the recycling process of waste concrete is well known to those skilled in the art. The embodiment of the present invention is obtained through commercial channels and purchased from Zhengzhou Weida Refractory Materials Co., Ltd., with a particle size range of 5mm-30mm.

[0024] The water reducer selected was polycarboxylate high-efficiency water reducer, purchased from Shanghai Hengchuang Chemical.

[0025] Alcoholamine compounds: diethanolamine or triethanolamine, purchased from Nanjing Kerunjiang Chemical.

[0026] In the present invention, the mass concentration of the nano-silica aqueous dispersion is 20% but not limited thereto. The preparation method of the nano-silica aqueous dispersion is: first, nano-silica is added to deionized water and stirred evenly, and then sodium lauryl sulfate is added and ultrasonically dispersed to obtain the dispersion. In the present invention, the mass ratio of nano-silica to sodium lauryl sulfate is 10:1 but not limited thereto.

[0027] Example 1

[0028] The environmentally friendly concrete provided in this embodiment includes 250 parts of cement, 800 parts of river sand, 900 parts of modified recycled construction waste, 100 parts of fly ash, 150 parts of water, 6 parts of water reducing agent, 80 parts of epoxy resin and 12 parts of diethanolamine;

[0029] Among them, the recycled construction waste is processed through the following steps:

[0030] (1) Carbonization treatment: The recycled construction waste is carbonized under the conditions of a pressure of 0.1 MPa, a humidity of 70% ± 5%, a temperature of 20°C ± 2°C, and a carbon dioxide concentration of 25% ± 2%. The carbonization time is 1 hour.

[0031] (2) Freeze-thaw cycle treatment: The carbonized recycled construction waste was immersed in a nano-silica aqueous dispersion for 2 days, and then subjected to freeze-thaw cycle treatment in a freeze-thaw test chamber for 5 times. The freezing end temperature was -18°C, the freezing time was 2 hours, the melting end temperature was 8°C, the melting time was 2 hours, and the freezing and melting temperatures changed evenly.

[0032] (3) Surface amination treatment: The recycled construction waste that has undergone freeze-thaw cycle treatment is dispersed in ethanol, deionized water and an aminosilane coupling agent accounting for 0.5% of the mass of the recycled construction waste are added, and the mixture is stirred for 30 minutes and then the liquid is filtered off.

[0033] The production method of environmentally friendly concrete is to mix cement, river sand, modified recycled construction waste, fly ash, water, water reducer and epoxy resin according to the formula, then add diethanolamine and mix them evenly under the condition of pH value of 7.5.

[0034] Example 2

[0035] The environmentally friendly concrete provided in this embodiment includes 300 parts of cement, 500 parts of river sand, 1200 parts of modified recycled construction waste, 80 parts of fly ash, 160 parts of water, 4 parts of water reducing agent, 100 parts of epoxy resin and 8 parts of triethanolamine;

[0036] Among them, the recycled construction waste is processed through the following steps:

[0037] (1) Carbonization treatment: The recycled construction waste is carbonized under the conditions of a pressure of 0.1 MPa, a humidity of 70% ± 5%, a temperature of 20°C ± 2°C, and a carbon dioxide concentration of 25% ± 2%. The carbonization time is 1 hour.

[0038] (2) Freeze-thaw cycle treatment: The carbonized recycled construction waste was immersed in a nano-silica aqueous dispersion for 4 days, and then subjected to freeze-thaw cycle treatment in a freeze-thaw test chamber for 10 times. The freezing end temperature was -20°C, the freezing time was 1 hour, the melting end temperature was 10°C, and the melting time was 1 hour. The freezing temperature and melting temperature both changed uniformly.

[0039] (3) Surface amination treatment: The recycled construction waste that has undergone freeze-thaw cycle treatment is dispersed in ethanol, deionized water and an aminosilane coupling agent accounting for 0.5% of the mass of the recycled construction waste are added, and the mixture is stirred for 30 minutes and then the liquid is filtered off.

[0040] The production method of environmentally friendly concrete is to mix cement, river sand, modified recycled construction waste, fly ash, water, water reducer and epoxy resin according to the formula, then add triethanolamine and mix them evenly under the condition of pH value of 7.5.

[0041] Example 3

[0042] The environmentally friendly concrete provided in this example includes 280 parts cement, 600 parts river sand, 1000 parts modified recycled construction waste, 92 parts fly ash, 157 parts water, 5 parts water reducer, 85 parts epoxy resin, and 10 parts triethanolamine. The modification process for the modified recycled construction waste is the same as in Example 1, and the production method for the environmentally friendly concrete is the same as in Example 1.

[0043] Comparative Example 1

[0044] The environmentally friendly concrete provided in this comparative example includes 250 parts cement, 800 parts river sand, 900 parts modified recycled construction waste, 100 parts fly ash, 150 parts water, 6 parts water reducer, and 92 parts epoxy resin. The modification process for the modified recycled construction waste is the same as in Example 1, and the production method for the environmentally friendly concrete is the same as in Example 1.

[0045] Comparative Example 2

[0046] The environmentally friendly concrete provided in this comparative example includes 250 parts cement, 800 parts river sand, 900 parts modified recycled construction waste, 100 parts fly ash, 150 parts water, 6 parts water reducer, and 92 parts diethanolamine. The modification process for the modified recycled construction waste is the same as in Example 1, and the production method for the environmentally friendly concrete is the same as in Example 1.

[0047] Comparative Example 3

[0048] The environmentally friendly concrete provided in this comparative example includes 250 parts cement, 800 parts river sand, 992 parts modified recycled construction waste, 100 parts fly ash, 150 parts water, and 6 parts water reducer. The modification process for the modified recycled construction waste is the same as in Example 1, and the production method for the environmentally friendly concrete is the same as in Example 1.

[0049] In addition, in order to explore the influence of the treatment method of recycled construction waste on the performance of concrete, based on the definition of the composition and production method of environmentally friendly concrete in Example 1, the treatment method of recycled construction waste was adjusted according to Table 1.

[0050] Table 1 Treatment methods for recycled construction waste

[0051]

[0052]

[0053] Note: "+" and "-" indicate that the corresponding treatment was performed or not performed, respectively. The amount of ethyl orthosilicate and ammonia water used in the control example was determined by the content of nano-silica in the nano-silica aqueous dispersion.

[0054] First, the concrete prepared in Example 1, Comparative Examples 1-3 and the blank example was made into 100 mm × 100 mm × 100 mm specimens according to the standard of GB / T50081-2019. After curing for 3 days, 7 days and 28 days under standard curing conditions, the compressive strength of the specimens was tested. The number of specimens in each group was 3, and the results were averaged.

[0055] The concrete prepared in Example 1, Comparative Examples 1-3, and a blank were subjected to water exudation rate measurement. The water exudation rate was determined as follows: First, wet a 5 L covered cylinder (185 mm inner diameter, 200 mm height) with a damp cloth. The concrete mixture was loaded into the cylinder at once. The cylinder was vibrated on a vibrating table for 20 seconds, then gently smoothed with a spatula. The cylinder was covered to prevent evaporation. The sample surface should be approximately 20 mm lower than the edge of the cylinder. Starting from the start of the smoothing process, water exudation was aspirated using a pipette every 10 minutes for the first 60 minutes. Thereafter, water was aspirated every 20 minutes until no water exudation was observed three times in a row. Five minutes before each aspiration, one side of the cylinder bottom was raised by approximately 20 mm to tilt the cylinder for easier aspiration. After aspiration, the cylinder was gently laid flat and covered. The water aspirated each time was poured into a stoppered graduated cylinder. The total water exudation was calculated to the nearest 1 g, and the water exudation rate was calculated according to the following formula. Three samples were collected for each group, and the results were averaged.

[0056]

[0057] Wherein, B represents the bleeding rate, in %; Vw represents the total mass of bleeding water, in g; W represents the total water consumption of the concrete mixture, in g; G represents the total mass of the concrete mixture, in g; Gw represents the mass of the sample, in g.

[0058] Table 2 Test results

[0059]

[0060]

[0061] As can be seen in Table 2, the concrete obtained in Example 1 exhibits good compressive strength. Comparative Examples 1-3, which varied the addition of epoxy resin and diethanolamine to the concrete components, show that the combination of epoxy resin and diethanolamine has a positive effect on the compressive strength of the concrete. This is because the recycled construction waste undergoes a freeze-thaw cycle, carbonization, and surface amination treatment. Under alkaline conditions, the active amino groups on the recycled construction waste react with some of the epoxy groups in the epoxy resin, while the remaining epoxy groups react with the amino groups on the diethanolamine. This strengthens the interaction between the epoxy resin and the recycled construction waste, forming a coating that reduces moisture intrusion into the modified recycled aggregate and ensures proper setting and hardening of the concrete.

[0062] In addition, the recycled construction waste of Example 1 is obtained by three-step modification, namely, freeze-thaw cycle treatment, carbonization treatment, and surface amino treatment. This allows the gaps in the aggregate to be filled with nano-silica, resulting in fewer gaps. While enhancing the strength, it can also avoid water absorption during the mixing process. At the same time, its surface structure is improved by mixing with epoxy resin and diethanolamine. Overall, its water bleeding rate is significantly reduced compared to the blank example.

[0063] Subsequently, the compressive strength and bleeding rate of the concrete prepared from Treatment-A to Treatment-E and the control example were tested according to the same test method as above. The results are shown in Table 3.

[0064] Table 3 Test results

[0065]

[0066] As can be seen from Table 3, different treatment methods of recycled construction waste have different effects on the performance of the prepared concrete. Treatment-A omits carbonization treatment, Treatment-B omits freeze-thaw cycle treatment, and Treatment-C omits both carbonization and freeze-thaw cycle treatment steps. From the results, it can be seen that the combination of carbonization treatment and freeze-thaw cycle treatment can promote the improvement of concrete strength while reducing the water exudation of concrete. At the same time, compared with the data of Treatment-D, it can be seen that the order of carbonization treatment and freeze-thaw treatment also affects the improvement of the strength of the final prepared concrete.

[0067] The foregoing description shows and describes several preferred embodiments of the invention. However, as previously stated, it should be understood that the invention is not limited to the form disclosed herein and should not be construed as excluding other embodiments. Rather, the invention is applicable to various other combinations, modifications, and environments and is capable of modification within the scope of the inventive concept described herein, through the teachings above, or through techniques or knowledge in the relevant art. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the invention are intended to be within the scope of the appended claims.

Claims

1. An environmentally friendly concrete based on construction waste, characterized in that: The raw materials include cement, river sand, modified recycled construction waste, fly ash, water, water reducing agent, epoxy resin and alcohol amine compound; The modified recycled construction waste is obtained by subjecting the recycled construction waste to carbonization treatment, immersing it in a nano-silicon dioxide aqueous dispersion for freeze-thaw cycle treatment, and surface amination treatment.

2. The environmentally friendly concrete based on construction waste according to claim 1, characterized in that: Calculated by weight, the environmentally friendly concrete includes 250-300 parts of cement, 500-800 parts of river sand, 900-1200 parts of modified recycled construction waste, 80-100 parts of fly ash, 150-160 parts of water, 4-6 parts of water reducer, 80-100 parts of epoxy resin and 8-12 parts of alcoholamine compound.

3. The environmentally friendly concrete based on construction waste according to claim 1, characterized in that: The alcoholamine compound is one of diethanolamine and triethanolamine.

4. The environmentally friendly concrete based on construction waste according to claim 1, characterized in that: The particle size of the modified and recycled construction waste is 5mm-30mm.

5. The environmentally friendly concrete based on construction waste according to claim 1, characterized in that: The nano-silicon dioxide aqueous dispersion is obtained by first adding nano-silicon dioxide into deionized water and stirring evenly, then adding sodium lauryl sulfate and subjecting it to ultrasonic dispersion treatment.

6. A method for producing environmentally friendly concrete based on construction waste according to any one of claims 1 to 5, characterized in that: The following steps are involved: (1) The recycled construction waste is first subjected to carbonization treatment, then immersed in a nano-silica aqueous dispersion for freeze-thaw cycle treatment, and finally subjected to surface amination treatment to obtain modified recycled construction waste; (2) According to the formula, cement, river sand, modified recycled construction waste, fly ash, water, water reducing agent and epoxy resin are first mixed evenly, and then the alcohol amine compound is added and mixed evenly under alkaline conditions.

7. The method for producing environmentally friendly concrete based on construction waste according to claim 6, characterized in that: In step (1), the immersion time of the recycled aggregate in the nano-silica aqueous dispersion is 2 days to 4 days, the freezing end temperature is -18°C to -20°C, the freezing time is 1 hour to 2 hours, the melting end temperature is 8°C to 10°C, and the melting time is 1 hour to 2 hours.

8. The method for producing environmentally friendly concrete based on construction waste according to claim 6, characterized in that: In step (1), the number of freeze-thaw cycle treatments is 5-10 times.

9. The method for producing environmentally friendly concrete based on construction waste according to claim 6, characterized in that: In step (1), the process parameters of the carbonization treatment are: pressure of 0.1 MPa, humidity of 70%±5%, temperature of 20°C±2°C, and carbon dioxide concentration of 25%±2%.

10. The method for producing environmentally friendly concrete based on construction waste according to claim 6, characterized in that: In step (1), the surface amination treatment is to disperse the carbonized recycled construction waste in ethanol, add aminosilane coupling agent and deionized water, stir and filter out the liquid.

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