A waste slurry admixture containing CO2 micro-nano bubbles and its preparation method and application

Abstract

The invention relates to the technical field of concrete production and discloses a waste slurry admixture containing CO2 micro-nano bubbles, a preparation method thereof, and an application thereof. The preparation method comprises the following steps: introducing CO2 gas into water to produce carbonated water with a CO2 concentration of not less than 5%; crushing solid waste from a mixing station to less than 3 mm to obtain crushed material; mixing the crushed material with carbonated water and grinding it into fine material, and controlling the pH value of the fine material to be not less than 7.5; subjecting the ground fine material to sedimentation treatment and taking the lower layer as the final product. The waste slurry admixture containing CO2 micro-nano bubbles prepared by the above method can be used as an auxiliary cementitious material in concrete production; the alkalinity of the waste slurry after carbon absorption is reduced, and the activity is further improved due to the formation of a new product, nano calcium carbonate; in addition, by introducing micro-nano bubbles into the ground fine material, ball lubrication is exerted and cohesion is reduced, thereby improving the problems of high consistency and rapid work loss of the waste slurry.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete production, and in particular to a waste slurry admixture containing CO2 micro-nano bubbles, and a preparation method and application thereof. Background Art

[0002] Waste slurry residue from mixing stations is solid waste generated during the concrete production process, usually including powder particles after screening of sand and gravel aggregates, concrete production waste, and waste collected after site cleaning.

[0003] Waste slurry residue, after sand and gravel separation, concentration, and grinding, can be used as a concrete admixture to replace some fly ash or cement, allowing it to be reused as a raw material in concrete production. However, due to its poor workability and low reactivity, its performance needs to be improved, resulting in limited applications.

[0004] Waste slurry residue contains a large amount of concrete-related alkaline substances with strong alkalinity. Using waste slurry residue to absorb CO2 and using the absorbed product in concrete production can help achieve carbon neutrality and green concrete production. Currently, there are no reports on combining waste slurry residue disposal with CO2 absorption. However, in the similar field of wastewater treatment, the use of ozone aeration for wastewater purification has been proposed. However, the technical difficulty lies in the fact that CO2 is slightly soluble in water. When combined with waste slurry residue through conventional aeration, CO2 escape is significant, the CO2 utilization rate is low, and the product easily forms and blocks the aeration pores. Summary of the Invention

[0005] The purpose of the present invention is to provide a waste pulp admixture containing CO2 micro-nano bubbles and its preparation method and application, so as to solve the technical problems in the prior art of low activity, narrow application range and difficulty in absorbing CO2 of waste pulp.

[0006] The present invention provides a method for preparing a waste slurry admixture containing CO2 micro-nano bubbles, comprising the following steps:

[0007] S100, introducing CO2 gas into water to produce carbonated water having a CO2 concentration of not less than 5%;

[0008] S200, crushing the solid waste from the mixing station to less than 3 mm to obtain crushed material;

[0009] S300, mixing the crushed material with carbonated water and grinding it into fine material, and controlling the pH value of the fine material to be not less than 7.5;

[0010] S400, the ground fine material is subjected to sedimentation treatment, and the lower layer of material is taken as the final product

[0011] Furthermore, in S100, the carbonated water is produced under a first pressure, and the first pressure is not less than 0.6 MPa.

[0012] Furthermore, the solid waste from the mixing station is alkaline and contains at least one alkaline substance in unhydrated cement and cement hydration products.

[0013] Furthermore, in S300, every 1.0m 3 Add 0.5-2.0m3 of crushed material 3 of carbonated water.

[0014] Furthermore, the mixing and grinding in S300 is performed under a second pressure, and the second pressure is not higher than 0.1 MPa.

[0015] Furthermore, the particle size of the fine material in S300 is less than 10 μm.

[0016] Furthermore, the final product in S400 has a solid content of at least 20%.

[0017] Furthermore, a foam stabilizer is added in the S300 grinding process. The foam stabilizer is at least one of sodium benzenesulfonate, polyacrylamide, and hydroxymethyl cellulose, and the added amount is 0.1-0.5% of the mass of the fine material.

[0018] The present invention further provides a waste slurry admixture containing CO2 micro-nano bubbles, which is prepared by the above preparation method.

[0019] The present invention also provides the use of the waste slurry admixture containing CO2 micro-nano bubbles as an auxiliary cementitious material for the production of ready-mixed concrete.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) A method for absorbing CO2 by using waste pulp is proposed. By preparing CO2 into carbonated water and adding it as a raw material component to the waste pulp grinding process, the waste pulp can efficiently absorb CO2 and accurately measure the amount of CO2 added, thereby avoiding the problems of obvious escape, low gas utilization rate, and easy clogging of aeration holes caused by conventional aeration.

[0022] (2) The present invention improves and optimizes the performance of existing waste slurry admixtures. By absorbing CO₂ from the waste slurry to form a new active substance, nano-calcium carbonate, the alkalinity of the waste slurry is reduced while increasing its activity. Furthermore, by introducing micro-nano bubbles into the ground material, ball lubrication is achieved, reducing cohesion and thus improving problems such as high consistency and rapid work loss.

[0023] (3) The preparation method of the admixture product proposed in the present invention is simple, and the raw materials come from solid waste and CO2, which are widely available resources, and can help enterprises achieve carbon neutrality and green production. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 This is a microscopic morphology of the admixture provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0026] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0027] The components of the embodiments of the present invention generally described and shown in the drawings herein may be arranged and designed in a variety of different configurations. Therefore, the following detailed description of the embodiments of the invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the invention.

[0028] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of the present invention.

[0029] An embodiment of the present invention provides a method for preparing a waste slurry admixture containing CO2 micro-nano bubbles. The method converts CO2 gas into carbonated water, which fully reacts with alkaline substances in solid waste from a mixing station to form nano-calcium carbonate, which is beneficial to strength. Compared with the waste slurry admixture prepared by the existing method, the alkalinity is significantly reduced and the admixture exhibits higher activity.

[0030] The specific preparation process includes the following steps:

[0031] S100, introducing CO2 gas into water to produce carbonated water having a CO2 concentration of not less than 5%;

[0032] S200, crushing the solid waste from the mixing station to less than 3 mm to obtain crushed material;

[0033] The solid waste from the mixing station here is alkaline and contains at least one alkaline substance in unhydrated cement and cement hydration products.

[0034] S300, mixing the crushed material with carbonated water and grinding it into fine material, preferably with a particle size of less than 10 μm, and controlling the pH value of the fine material to be not less than 7.5;

[0035] S400, performing sedimentation treatment on the ground fine material, taking the lower layer of material as the final product, and controlling the solid content of the final product to be at least 20%.

[0036] Among them, in S100, carbonated water is produced under a first pressure, which is not less than 0.6 MPa. The pressurized condition significantly increases the solubility of CO2, forming a CO2 supersaturation state, allowing more CO2 to be stored in the aqueous solution in the form of carbonic acid.

[0037] In addition to the pressure control required in the aforementioned processes, in S300, the crushed material and carbonated water are mixed and ground under a second pressure, which is no higher than 0.1 MPa. This setting is intended to take into account the reduced ambient pressure and the shearing effect of the solid-liquid multiphase mixing caused by physical grinding, thereby disrupting the CO2 dissolution equilibrium and allowing the CO2 to be released in the form of micro-nano bubbles.

[0038] In addition, in S300, the mixing ratio of crushed material and carbonated water is generally controlled at 3 Add 0.5-2.0m3 of crushed material 3 At the same time, in the mixed grinding process of solid waste crushing materials and carbonated water, the amount of carbonated water added needs to be adjusted according to the CO2 concentration in the carbonated water and the pH performance of the fine material. This is because when carbonated water is added in excess, the generated nano-calcium carbonate will be converted into calcium bicarbonate. Therefore, the pH value of the fine material is maintained at a level not lower than 7.5, which can avoid the deterioration of the fine material performance and waste of raw materials caused by excessive addition of carbonated water.

[0039] During the grinding process, a foam stabilizer can be added. This modifies the surface tension of bubbles in the ground material, forming a thin molecular film on their surface, thereby reducing their potential for collapse and disappearance. Furthermore, the foam stabilizer enhances the entrainment process, facilitating the formation of microbubbles. Preferably, the foam stabilizer is at least one of sodium benzenesulfonate, polyacrylamide, and hydroxymethylcellulose, with an addition level of 0.1-0.5% of the mass of the ground material.

[0040] The invention also discloses a waste slurry admixture containing CO2 micro-nano bubbles, which is prepared by the above preparation method and can be used as an auxiliary cementitious material in the production of ready-mixed concrete.

[0041] The present invention is described in detail below by way of examples:

[0042] Example 1:

[0043] (1) introducing CO2 gas into water to produce carbonated water, wherein the CO2 concentration in the carbonated water is 5%;

[0044] (2) crushing the solid waste from the mixing station to less than 3 mm to obtain crushed material;

[0045] (3) Mix the crushed material with carbonated water and grind it into fine material (d50 = 8.5 μm). 3 Crushed material added 2.0m 3 Carbonated water to control the pH of the fines at 7.5;

[0046] (4) The ground material is subjected to sedimentation treatment, and the lower layer is taken as the final product S1 (solid content is 20%);

[0047] Example 2:

[0048] (1) introducing CO2 gas into water to produce carbonated water, wherein the CO2 concentration in the carbonated water is 15%;

[0049] (2) crushing the solid waste from the mixing station to less than 3 mm to obtain crushed material;

[0050] (3) Mix the crushed material with carbonated water and grind it into fine material (d50 = 8.5 μm). 3 Add 0.5m3 of crushed material 3 Carbonated water to control the pH of the fines at 7.5;

[0051] (4) The ground material is subjected to sedimentation treatment, and the lower layer is taken as the final product S2 (solid content is 20%);

[0052] Example 3:

[0053] (1) introducing CO2 gas into water to produce carbonated water, wherein the CO2 concentration in the carbonated water is 15%;

[0054] (2) crushing the solid waste from the mixing station to less than 3 mm to obtain crushed material;

[0055] (3) Mix the crushed material with carbonated water and grind it into fine material (d50 = 8.5 μm). 3 Crushed material added 2.0m 3 Carbonated water to control the pH of the fines at 7.5;

[0056] (4) The ground material is subjected to sedimentation treatment, and the lower layer is taken as the final product S3 (solid content 40%);

[0057] Example 4:

[0058] (1) introducing CO2 gas into water to produce carbonated water, wherein the CO2 concentration in the carbonated water is 5%;

[0059] (2) crushing the solid waste from the mixing station to less than 3 mm to obtain crushed material;

[0060] (3) Mix the crushed material with carbonated water and grind it into fine material (d50 = 8.5 μm). 3 Crushed material added 2.0m 3 Carbonated water was used to control the pH value of the fine material at 7.5. During the grinding process, 0.15% foam stabilizer (sodium benzenesulfonate and polyacrylamide in a mass ratio of 1:1) was added.

[0061] (4) The ground material is subjected to sedimentation treatment, and the lower layer is taken as the final product S4 (solid content is 20%);

[0062] Example 5:

[0063] (1) introducing CO2 gas into water to produce carbonated water, wherein the CO2 concentration in the carbonated water is 5%;

[0064] (2) crushing the solid waste from the mixing station to less than 3 mm to obtain crushed material;

[0065] (3) Mix the crushed material with carbonated water and grind it into fine material (d50 = 8.5 μm). 3 Crushed material added 1.0m 3 carbonated water, the pH value of the fine material was actually measured to be 9.0;

[0066] (4) The ground material is subjected to sedimentation treatment, and the lower layer is taken as the final product S5 (solid content is 20%);

[0067] Comparative Example 1:

[0068] (1) Crushing the solid waste from the mixing station to less than 3 mm to obtain crushed material;

[0069] (2) The crushed material was ground into fine material (d50 = 8.5 μm), and the pH value was measured to be 13.1;

[0070] (3) The ground material was subjected to sedimentation treatment, and the lower layer was taken as the final product D1 (solid content 20%);

[0071] Comparative Example 2:

[0072] (1) introducing CO2 gas into water to produce carbonated water, wherein the CO2 concentration in the carbonated water is 15%;

[0073] (2) crushing the solid waste from the mixing station to less than 3 mm to obtain crushed material;

[0074] (3) Mix the crushed material with carbonated water and grind it into fine material (d50 = 8.5 μm). 3 Crushed material added 3.0m 3 Carbonated water, the pH value of the fine material was not controlled to 7.5, and the actual measurement was 5.8;

[0075] (4) The ground material is subjected to sedimentation treatment, and the lower layer is taken as the final product D2 (solid content is 20%);

[0076] The final products of Examples 1-5 and Comparative Examples 1-2 were subjected to concrete tests. The test mix ratios and concrete performance test results are as follows:

[0077] Table 1 Concrete test mix ratio

[0078] cement fly ash Waste pulp medium sand gravel water admixtures 220 70 30 950 980 160 5.5

[0079] Table 2 Test results

[0080] Group S1 S2 S3 S4 S5 D1 D2 Slump expansion at the exit of the machine / mm 580 580 610 600 560 520 600 2h slump expansion / mm 530 540 580 600 480 430 550 28d compressive strength / MPa 36.7 37.1 37.3 35.5 34.9 33.2 33.6

[0081] From the comparison of S1 and D1, it was found that under the same test conditions, the concrete prepared with S1 had a larger slump expansion after leaving the machine, a smaller 2h expansion loss, and a higher 28-day strength, which was close to an increase of 3MPa, showing obvious advantages in workability and strength performance.

[0082] This is precisely because the present invention uses CO2 as a raw material for waste slurry production. After carbon absorption, the alkalinity of the waste slurry is significantly reduced, reducing the adverse effects of alkali substances in the waste slurry on the workability of concrete. After carbon absorption, the alkali substances in the waste slurry form nano-calcium carbonate, which exerts a crystal nucleation and micro-filling effect, showing higher gelling activity, thereby further improving the strength of concrete. At the same time, the micro-nano bubbles formed in the waste slurry act as ball lubrication, reducing the cohesion between the cement paste and aggregate, thereby improving the fluidity and collapse resistance of the concrete.

[0083] From the comparison of S1 and S4, it can be seen that the slump retention of waste pulp is better after adding the foam stabilizer, but the compressive strength is reduced. Therefore, in actual use, the foam stabilizer can be selectively added according to the specific conditions of use.

[0084] Comparisons of S2 / D2 and S1 / S5 reveal that the performance of the present invention is highly correlated with the pH of the ground material. Excessive addition of carbonated water in D2 makes the ground material acidic, affecting the formation of nano-calcium carbonate and eliminating the concrete strength advantages originally demonstrated by this technology. S5, due to the low CO2 concentration in the carbonated water and insufficient addition of carbonated water, incomplete carbon absorption by the waste pulp residue resulted in inferior performance to S1 and S2.

[0085] Although the pH value of the above-mentioned fine material is too high or too low, it affects the performance of the final product. However, when the pH value is high, although the performance is not as good as that of other embodiments, it absorbs CO2 and the performance is improved compared with the original waste pulp. On the other hand, when the pH value is low, the excess carbonated water cannot be absorbed by the waste pulp, causing CO2 to escape and failing to achieve the purpose of carbon neutrality. Therefore, in this application, the pH value of the fine material is preferably not less than 7.5.

[0086] The final product prepared by the above preparation method contains micro-nano bubbles, and the diameter of the micro-nano bubbles is 100-1000 nm. The final products of Example 1, Example 4, Example 5, and Comparative Example 1 were analyzed for micro-nano bubble concentration. The bubble concentration in the range of 10-1000 nm per unit volume was obtained by nanoparticle size tester and software analysis. The results are as follows:

[0087] Table 3 Bubble concentration test results (unit: pieces / mL)

[0088] Group S1 S4 D1 S5 Initial bubble concentration <![CDATA[4.2×10 6 ]]> <![CDATA[3.3×10 8 ]]> 120 <![CDATA[9.2×10 4 ]]> Bubble concentration after 3 days <![CDATA[8.1×10 4 ]]> <![CDATA[5.6×10 7 ]]> — 211

[0089] From the test results of S1 in Table 3, it can be seen that a large number of micro-nano bubbles can be detected in the product from the initial stage to 3 days after placement. This is not present in the waste slurry admixture D1 prepared according to the existing method, and is also the reason why the performance of S1 and D1 shows significant differences.

[0090] S4 adds a foam stabilizer, which causes more micro-nano bubbles to form in the product.

[0091] Due to insufficient addition of carbonated water in S5, micro-nano bubbles were only formed in the early stage of the product. Under the action of residual alkaline substances and the slow escape of CO2, the micro-nano bubbles in the product were significantly reduced after 3 days.

[0092] The product of Example 1 was photographed by scanning electron microscope, and the results were as follows: Figure 1 , micro-nano calcium carbonate grains were observed at a resolution of 200nm, indicating that nano calcium carbonate was formed in the product of the present invention.

[0093] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a waste pulp admixture containing CO2 micro-nano bubbles, characterized in that: The steps include: S100, introducing CO2 gas into water to produce carbonated water having a CO2 concentration of not less than 5%; S200, crushing the solid waste from the mixing station to less than 3 mm to obtain crushed material; S300, mixing the crushed material with carbonated water and grinding it into fine material, and controlling the pH value of the fine material to be not less than 7.5; S400, performing sedimentation treatment on the ground fine material, and taking the lower layer of material as the final product; In S100, the carbonated water is produced under a first pressure, and the first pressure is not less than 0.6 MPa; The mixing and grinding in S300 is performed under a second pressure, which is not higher than 0.1 MPa.

2. The preparation method according to claim 1, characterized in that The solid waste from the mixing station is alkaline and contains at least one alkaline substance in unhydrated cement and cement hydration products.

3. The preparation method according to claim 1, characterized in that In S300, every 1.0m 3 Add 0.5-2.0m3 of crushed material 3 of carbonated water.

4. The preparation method according to claim 1, characterized in that The particle size of fine material in S300 is less than 10μm.

5. The preparation method according to claim 1, characterized in that The final product in S400 has a solid content of at least 20%.

6. The preparation method according to claim 1, characterized in that A foam stabilizer is further added during the S300 grinding process. The foam stabilizer is at least one of sodium benzenesulfonate, polyacrylamide, and hydroxymethyl cellulose, and the added amount is 0.1-0.5% of the mass of the fine material.

7. A waste pulp admixture containing CO2 micro-nano bubbles, characterized in that: Prepared by the preparation method according to any one of claims 1 to 6.

8. An application of the waste pulp admixture containing CO2 micro-nano bubbles as claimed in claim 7, characterized in that: Used as an auxiliary cementitious material in concrete production.

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