A method for modifying subway muck slurry and low-carbon concrete based on modified subway muck slurry

Abstract

The application discloses a subway residue soil slurry modification method and low-carbon concrete based on modified subway residue soil slurry. First, the subway residue soil slurry is uniformly mixed with micron silica gel, and then mixed with cationic polyacrylamide to obtain a mixture; then, amino silane coupling agent, dilute sulfuric acid and microcrystalline cellulose are added, and sodium hydroxide is added to adjust the pH to obtain modified subway residue soil slurry; finally, the mixture is obtained by stirring the mixture, the modified subway residue soil slurry, modified slurry active inducer and water reducing agent, wherein the mixture is obtained by uniformly mixing cement, fly ash, coarse aggregate and fine aggregate. The low-carbon concrete realizes in-situ treatment of the residue soil slurry by modifying the residue soil slurry, realizes the use of the residue soil slurry to replace part of the cementitious material, and realizes the resource utilization of the residue soil slurry in the production of concrete. The application reduces the use of cement, realizes the resource utilization and in-situ use of the residue soil slurry, and reduces carbon emissions.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of industrial solid waste treatment, and particularly relates to a subway muck slurry modification method and low-carbon concrete based on modified subway muck slurry. BACKGROUND

[0002] With the further development of urbanization, subway construction in large and medium-sized cities across the country is becoming increasingly intensive, and a large amount of subway muck slurry, especially subway shield muck slurry, is also generated. The water content of the muck slurry is high, the clay content is high, the treatment difficulty is great, and the treatment cost is high. At present, the main treatment method for subway muck slurry is to transport the earthwork excavated by the shield machine to the storage tank through the belt, and then hoist it to the ground truck by the crane for landfill and stacking treatment. Few resources are used for treatment. However, if the subway muck is not treated harmlessly and directly enters the receiving field, it will not only cause adverse effects on the surrounding water and soil environment, but also may cause landslides and other geological disasters, threatening the safety of people's lives and property. Therefore, how to treat and utilize it in a low-carbon way has become an important technical problem in the field of subway construction.

[0003] Existing researches on resource utilization of subway muck slurry mainly conduct comprehensive researches in the fields of muck characteristics and classification, solidification technology, harmless treatment, clay unburned brick equipment and production line, etc. to realize the preparation of unburned muck bricks. In addition, no concrete resource utilization technology for subway muck slurry has been found. Especially in the process of subway construction, a large amount of concrete is needed. Through the modification of muck slurry, its utilization in concrete is an important direction for its resource utilization, and also an important means to realize its in-situ treatment. SUMMARY

[0004] In view of the problems in the background art, the present application proposes a low-carbon concrete based on subway muck and a preparation method thereof by modifying the muck slurry, realizing the resource utilization of subway muck slurry.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0006] A subway muck slurry modification method, comprising:

[0007] (1) uniformly mixing subway muck slurry and micron silica gel, and then mixing and ultrasonic dispersing the mixture with cationic polyacrylamide;

[0008] (2) adding amino silane coupling agent and dilute sulfuric acid to the mixture obtained in step (1) and ultrasonic dispersing them uniformly, then hydrothermally reacting for 6-8 hours, adding microcrystalline cellulose, ultrasonic dispersing again, and finally adding sodium hydroxide to adjust the pH to 12-13 to obtain modified subway muck slurry;

[0009] The mass fractions of the above raw material components are as follows:

[0010]

[0011] The water content of the subway muck slurry is 40-50%, and when the water content is too high, drying should be performed to control the water content to be 40-50%;

[0012] The mass concentration of the dilute sulfuric acid is 30%.

[0013] The ultrasonic dispersion time in step (1) is 15-20 min.

[0014] The hydrothermal reaction temperature in step (2) is 60-80 DEG C.

[0015] The ultrasonic dispersion reaction time after the addition of microcrystalline cellulose in step (2) is 4-6 h.

[0016] The application further provides a low-carbon concrete based on the modified subway muck slurry, which is obtained by pouring a mixture into a mold after stirring the mixture with the modified subway muck slurry, a modified slurry active inducer and a water reducing agent, and then pressing under the condition of 0.5-1 MPa, wherein the mixture is uniformly mixed by cement, fly ash, coarse aggregate and fine aggregate.

[0017] The mass fractions of the raw material components are as follows:

[0018]

[0019]

[0020] The modified slurry active inducer is a suspension obtained by ultrasonic dispersion of a mixture of nano calcium silicate crystal nucleus / nano calcium hydroxide, triethanolamine liquid and anhydrous ethanol at a mass ratio of 1:1:3, wherein the mixture of nano calcium silicate crystal nucleus / nano calcium hydroxide is obtained by mixing nano calcium silicate crystal nucleus and nano calcium hydroxide at a mass ratio of 1-5:20.

[0021] The cement is P.O. 42.5 Portland cement.

[0022] The application has the following beneficial effects:

[0023] (1) The low-carbon concrete realizes resource utilization of muck slurry by modifying the muck slurry, and realizes resource utilization in concrete production by replacing part of cementing materials through modification of the muck. The application reduces the use of cement, realizes resource utilization of muck slurry, reduces carbon emission, and has important significance for production and utilization of low-carbon muck concrete.

[0024] (2) In the subway soil slurry modification method, the flowability of the slurry and the ease of sliding between the slurry particles are improved by the addition of micron silica gel, and the exchange of siloxyl ions between the slurry and the silica gel is promoted; further, the suspension and dispersion of the slurry micro-particles are increased by the addition of cationic polyacrylamide, and agglomeration is avoided, and a stable slurry with uniformly distributed particles is formed after ultrasonic dispersion; further, ion replacement and surface modification of the montmorillonite in the slurry, which has a water absorption and swelling effect on cement and thus adversely affects the cement, can be carried out by the addition of acid and amino silane coupling agent, reducing the overall water absorption of the slurry and improving the activity of the slurry micro-particles under certain temperature (60-80℃) conditions; further, by incorporating microcrystalline cellulose, which has no fiber and has strong flowability, the surface of the modified slurry particles is attached, the water absorption and active ion replacement reaction are reduced, and the overall flowability is improved; on this basis, the pH of the slurry is increased, the solubility and permeability of the microcrystalline cellulose on the particle surface are improved, and the swelling effect is improved, which can better adhere to the montmorillonite in the slurry and reinforce the interface film, reduce the water absorption, and at the same time, the activity of the slurry as a whole under alkaline conditions is further stimulated and maintained, which is convenient for reaction with cement and other cementitious materials.

[0025] (3) In the modified slurry activity inducer used in the present application, nano calcium hydroxide can rapidly react with activated silicon dioxide in the slurry to form hydrated calcium silicate, and further use nano calcium silicate as a crystal nucleus to reduce the formation reaction barrier, accelerate the formation of hydrated calcium silicate and promote the reaction to occur, induce the activation of the slurry, and quickly participate in the cement hydration reaction, thereby realizing the use of the slurry as a low cementitious material and the preparation of a low-carbon cementitious material based on the soil slurry.

[0026] (4) In the preparation process of concrete, after the mixture is formed, it is poured into a mold for compression molding, mainly because the concrete prepared by the present application is low water-cement ratio concrete, which exhibits dry hardness after the mixture is formed, and therefore needs to be compression molded. The reason why the present application adopts low water-cement ratio is based on the use of microcrystalline cellulose, which has excellent lubricity and high compressibility, especially under high pressure, the adhesion of microcrystalline cellulose increases, which can improve the adhesion between concrete materials, thereby greatly improving the performance of the concrete. DETAILED DESCRIPTION

[0027] The technical solutions of the present application will be described below in conjunction with the embodiments, obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0028] Example 1

[0029] A preparation method of low-carbon concrete based on subway soil slurry:

[0030] (1) Take 180 parts of cement P.O42.5 Portland cement, 80 parts of fly ash, 850 parts of coarse aggregate, and 800 parts of fine aggregate, mix and stir uniformly to obtain a mixture;

[0031] (2) Take 200 parts of modified subway soil slurry (slurry moisture content 40%), 5 parts of modified slurry active inducer, and 5 parts of water reducing agent, mix and stir uniformly, then pour into the mixture, continue to stir to form low-carbon concrete;

[0032] The modification method of subway soil slurry is as follows: 100 parts of slurry are mixed with 3 parts of micron silica gel, then mixed with 2 parts of cationic polyacrylamide, ultrasonic dispersion for 15 min, 3 parts of amino silane coupling agent are added, 5 parts of dilute sulfuric acid are added, ultrasonic dispersion is uniform, heated to 80℃, reacted for 6h, 1 part of microcrystalline cellulose is added, ultrasonic dispersion is reacted for 6h, sodium hydroxide is added to adjust the pH to 12, and the modified subway soil slurry is obtained;

[0033] The mass concentration of the dilute sulfuric acid is 30%.

[0034] The modified slurry active inducer is: 1 part of nano calcium silicate crystal nucleus and 20 parts of nano calcium hydroxide are mixed according to the mass ratio of 5:20, 1 part of triethanolamine liquid and 3 parts of anhydrous ethanol are added, and a suspension obtained by ultrasonic dispersion.

[0035] Example 2

[0036] A preparation method of low-carbon concrete based on in-situ treatment of subway soil slurry:

[0037] (1) Take 240 parts of cement P.O42.5 Portland cement, 50 parts of fly ash, 1100 parts of coarse aggregate, and 650 parts of fine aggregate, mix and stir uniformly to obtain a mixture;

[0038] (2) Take 150 parts of modified subway soil slurry (slurry moisture content 50%), 10 parts of modified slurry active inducer, and 3 parts of water reducing agent, mix and stir uniformly, then pour into the mixture, continue to stir to form low-carbon concrete;

[0039] The modification method of subway soil slurry is as follows: 100 parts of slurry are mixed with 5 parts of micron silica gel, then mixed with 1 part of cationic polyacrylamide, ultrasonic dispersion for 20 min, 2 parts of amino silane coupling agent are added, 6 parts of dilute sulfuric acid are added, ultrasonic dispersion is uniform, heated to 60℃, reacted for 8h, 2 parts of microcrystalline cellulose are added, ultrasonic dispersion is reacted for 4h, sodium hydroxide is added to adjust the pH to 13, and the modified subway soil slurry is obtained;

[0040] The mass concentration of the dilute sulfuric acid is 30%.

[0041] The modified mud active inducer is: nano calcium silicate crystal nucleus, nano calcium hydroxide, after mixing in a mass ratio of 1:20, taking 1 part, adding 1 part triethanolamine liquid, 3 parts of anhydrous ethanol, and obtaining a suspension liquid by ultrasonic dispersion.

[0042] Example 3

[0043] A preparation method of low-carbon concrete based on in-situ treatment of subway soil slurry:

[0044] (1) Take 200 parts of cement P.O.425 Portland cement, 60 parts of fly ash, 1000 parts of coarse aggregate, and 750 parts of fine aggregate, mix and stir uniformly to obtain a mixture;

[0045] (2) Take 180 parts of modified subway soil slurry (slurry moisture content 45%), 8 parts of modified mud active inducer, and 4 parts of water reducing agent, mix and stir uniformly, then pour into the mixture, continue to stir to form low-carbon concrete;

[0046] The modification method of subway soil slurry is: uniformly mix 100 parts of slurry with 4 parts of micron silica gel, mix with 1.5 parts of cationic polyacrylamide, ultrasonic dispersion for 17 min, add 2.5 parts of amino silane coupling agent, add 5.6 parts of dilute sulfuric acid, ultrasonic dispersion, heat to 70℃, react for 7h, then add 3 parts of microcrystalline cellulose, ultrasonic dispersion and reaction for 5h, then add sodium hydroxide to adjust pH to 12.8 to obtain modified subway soil slurry;

[0047] The mass concentration of the dilute sulfuric acid is 30%.

[0048] The modified mud active inducer is: nano calcium silicate crystal nucleus, nano calcium hydroxide, after mixing in a mass ratio of 4:20, taking 1 part, adding 1 part triethanolamine liquid, 3 parts of anhydrous ethanol, and obtaining a suspension liquid by ultrasonic dispersion.

[0049] Comparative Example 1

[0050] The difference from Example 3 is that the modified subway soil slurry and the modified mud active inducer are not mixed, and are replaced by cement.

[0051] Comparative Example 2

[0052] The difference from Example 3 is that the subway soil slurry is not modified.

[0053] Comparative Example 3

[0054] The difference from Example 3 is that the modified mud active inducer is not mixed.

[0055] Comparative Example 4

[0056] The difference from Example 3 is that no microcrystalline cellulose is added in the process of modifying the slag slurry.

[0057] Comparative Example 5

[0058] The difference from Example 3 is that no nano calcium hydroxide is added in the process of modifying the slurry activation inducer.

[0059] Comparative Example 6

[0060] The difference from Example 3 is that non-nano analytical pure calcium hydroxide is added in the process of modifying the slurry activation inducer to replace nano calcium hydroxide.

[0061] The performance indicators of the low-carbon concrete obtained in each of the above examples and comparative examples are shown in Table 1:

[0062] Table 1: 28d compressive strength and activity index of each group of samples

[0063] No. 28d compressive strength / MPa Example 1 56.7 Example 2 54.9 Example 3 55.4 Comparative Example 1 54.8 Comparative Example 2 32.5 Comparative Example 3 45.9 Comparative Example 4 44.5 Comparative Example 5 46.8 Comparative Example 6 47.6

[0064] As can be seen from Table 1, the 28d compressive strength in the examples is between 54.9-56.7MPa, and as can be seen from Comparative Example 3 and Comparative Example 1, when the modified mud is used to replace cement, the 28d compressive strength is also reduced by 0.6MPa, which shows that the use of the modified mud can ensure that the mechanical properties of the concrete do not decrease; as can be seen from Comparative Example 3, Comparative Example 1 and Comparative Example 2, when the mud is not modified, the compressive strength is greatly reduced and is lower than that of the concrete prepared by the modified mud and cement; as can be seen from Comparative Example 3 and Comparative Example 3, when the modified mud does not contain the activation inducer, the strength is reduced by 3.5MPa, which shows that the activation inducer plays an important role in improving the activity of the mud. As can be seen from Comparative Example 3 and Comparative Example 4, when the microcrystalline cellulose is not added during the modification of the mud, the mechanical properties of the concrete decrease obviously, which is mainly because the adhesion of the microcrystalline cellulose itself increases under the action of drying and pressure, which improves the adhesion between the concrete particles, and when the microcrystalline cellulose is not added, the modification effect on the mud and the montmorillonite-like substance in the mud is reduced. As can be seen from Comparative Example 3 and Comparative Example 5, the mechanical properties of the concrete prepared by the activation activator lacking nano calcium hydroxide are reduced, which is mainly because the nano silicon dioxide can quickly react with the active silicon dioxide to promote the activation of the active substances in the mud, and the lack of high-activity alkaline substance activation suppresses the dissolution of the active substances in the mud. As can be seen from further comparison of Comparative Example 3 and Comparative Example 5, Comparative Example 6, the use of conventional analytical pure calcium hydroxide has limited activation effect on the mud and has little difference from the case where no calcium hydroxide is used, but is obviously lower than Example 3 using nano calcium hydroxide. This is mainly because the nano calcium hydroxide has high activity and can obviously promote the dissolution of the silicon dioxide in the mud and accelerate the reaction between the two, which is beneficial to the activation of the mud. However, the conventional calcium hydroxide has low solubility and can only react with the silicon dioxide in the mud by slow dissolution and calcium ion replacement (similar to the three-component mortar), which takes a long time and has low efficiency. Moreover, after the addition of cement, a large amount of calcium ions in the cement are dissolved and the cement hydration reaction is carried out, which greatly inhibits the reaction between the silicon dioxide and the calcium hydroxide in the mud, resulting in a decrease in the strength of the concrete. As can be seen, the use of nano calcium hydroxide as the activation activator component can promote the activation of the mud during the mixing process with the inducer in advance, and then participate in the cement hardening process. This is an effect that cannot be achieved by conventional calcium hydroxide.

Claims

1. A method for modifying subway construction waste slurry, characterized in that, include: (1) After the subway slag slurry is mixed evenly with micron silica gel, it is mixed with cationic polyacrylamide and then ultrasonically dispersed. (2) After adding aminosilane coupling agent and dilute sulfuric acid to the mixture obtained in step (1) and ultrasonically dispersing it evenly, after hydrothermal reaction for 6-8 hours, microcrystalline cellulose is added, ultrasonic dispersion reaction is carried out again, and finally sodium hydroxide is added to adjust the pH to 12-13 to obtain modified subway slag slurry. The mass fractions of the above raw material components are as follows: The moisture content of the subway slag slurry is controlled at 40% to 50%. The mass concentration of the dilute sulfuric acid is 30%.

2. The method for modifying subway construction waste slurry according to claim 1, characterized in that, The ultrasonic dispersion time mentioned in step (1) is 15-20 min; The hydrothermal reaction temperature in step (2) is 60–80°C; The ultrasonic dispersion reaction time after adding microcrystalline cellulose in step (2) is 4-6 hours.

3. A low-carbon concrete based on the modified subway slag slurry as described in claim 1 or 2, characterized in that, The mixture is obtained by mixing the above-mentioned modified subway slag slurry, modified slurry activation inducer and water-reducing agent, pouring it into a mold, and pressing it under a pressure of 0.5 to 1 MPa. The mixture is obtained by mixing cement, fly ash, coarse aggregate and fine aggregate evenly. The mass fractions of each raw material component are as follows: The modified mud activity inducer is a suspension obtained by ultrasonic dispersion of a mixture of nano-calcium silicate nuclei / nano-sized calcium hydroxide, triethanolamine liquid, and anhydrous ethanol in a mass ratio of 1:1:

3.

4. The low-carbon concrete according to claim 3, characterized in that, The mixture of nano-calcium silicate crystal nuclei / nano-grade calcium hydroxide is obtained by mixing nano-calcium silicate crystal nuclei and nano-grade calcium hydroxide at a mass ratio of 1 to 5:

20.

5. The low-carbon concrete according to claim 4, characterized in that, The cement is PO42.5 silicate cement.

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