Low-temperature high-moisture-content silt solidifying agent, its preparation method and application

Abstract

The present invention relates to the technical field of cement-based building materials, and in particular to a low-temperature high-water-content silt solidifying agent, its preparation method and application. By using composite cement, ultra-fine mineral admixtures, and cooperating with high-water-demand active powders and strengthening agents as the main materials, and adding water-reducing agents, water-absorbing resins, thickeners, retarders and dispersants as compound admixtures, a solidifying agent that can be used for solidifying high-water-content silt with rapid solidification, good anti-dispersion property, green and low-carbon under low-temperature conditions is prepared.

Description

Technical Field

[0001] The present invention relates to the technical field of cement-based building materials, and particularly to a low-temperature high-water-content sludge solidifying agent, a preparation method thereof, and an application thereof. Background Art

[0002] In coastal areas, the middle and lower reaches of rivers, or areas near lakes, there are a large amount of sludge soft soils under the surface of the water bottom.

[0003] The sludge soft soil has extremely low strength, high compressibility, and poor water permeability, resulting in low foundation bearing capacity and slow strength growth in this area.

[0004] Solidification treatment is a commonly used method for realizing the resource utilization of a large amount of dredged sludge at home and abroad.

[0005] In addition to the factors of the solidifying material itself, the initial water content of the sludge also has an important impact on the final strengthening effect of the solidified soil.

[0006] The prior art CN118993499A uses magnesium silicate, aluminum sulfate, polyferric sulfate, ammonium sulfate, and quicklime as solidifying materials, which can effectively improve the early strength of the solidified soil within 3-7 days of age, improve the construction efficiency. Among them, the water content of the solidified soil is 120%-260%, the dosage of the solidifying agent is 8%-15%, and the 7-day compressive strength can reach up to 900 kPa at most.

[0007] In the prior art patent CN118239721A, ground granulated blast-furnace slag and glass powder are used to modify marine sludge. The water content of the soil is 80%-90%, and the 7-day compressive strength of the solidified body can reach up to 4 MPa at most.

[0008] The above-mentioned prior arts can all treat high-water-content sludge. However, in the construction of sludge solidification in high-latitude coastal areas under low temperature, in an environment with high water content and low temperature, how to make the sludge soil reach the hourly strength and can also resist the erosion of seawater to meet the requirements of rapid service of the project still needs further research. Summary of the Invention

[0009] To solve the problems existing in the prior art, the present invention provides a low-temperature high-water-content sludge solidifying agent. Specifically, by using composite cement, ultrafine mineral admixtures, and cooperating with high-water-demand active powders and strengthening agents as main materials, adding water-reducing agents, water-absorbing resins, thickeners, retarders, and dispersants as compound admixtures, a solidifying agent that can be used for solidifying high-water-content sludge with rapid solidification, good anti-dispersion property, and green and low-carbon under low-temperature conditions is prepared.

[0010] Specifically, the low-temperature high-water-content sludge solidifying agent of the present invention is composed of the following raw materials in parts by weight: 10-15 parts of ordinary Portland cement, 25-30 parts of sulfoaluminate cement, 20-28 parts of ultra-fine mineral admixture, 20-30 parts of high-water-demand active powder, 6-8 parts of reinforcing agent, 0.1-1 part of water reducer, 0.1-1 part of water-absorbing resin, 0.1-0.5 part of thickening agent, 0.1-1 part of retarder, and 0.1-2 parts of dispersant.

[0011] Preferably, the ultra-fine mineral admixture is composed of ultra-fine fly ash, silica fume and mineral powder mixed in a mass ratio of (1-2):(0.3-0.5):(2-3).

[0012] Preferably, the preparation process of the high-water-demand active powder is as follows: CaO, Al2O3 and SiO2 are uniformly mixed in a mass ratio of 1:(0.5-0.8):(2-3), pressed into tablets, melted at high temperature, quenched rapidly, ground into fine powder, and the fine powder and anhydrite are mixed evenly in a mass ratio of (6.5-7):(3-4) and then ultra-finely ground to obtain the product.

[0013] Preferably, the reinforcing agent is composed of C-S-H crystal nuclei, silicon nitride nanowhiskers and methyldiethanolamine mixed in a mass ratio of (0.5-5):(0.1-1):1.

[0014] The solidification of high-water-content sludge is more difficult than that of ordinary sludge. First, the influence of high water content needs to be overcome, and then the solidification of sludge particles needs to be achieved. For this reason, the present invention uses ordinary Portland cement and sulfoaluminate cement as composite cement, and uses ultra-fine mineral admixture to improve the activity of cementitious materials, provide a micro-filling effect to promote the drainage of water between sludge particles. The present invention burns the high-water-demand active powder at high temperature and cooperates with a reinforcing agent to achieve the low-temperature rapid solidification of high-water-content sludge.

[0015] The present invention uses CaO, Al2O3 and SiO2 to prepare high-water-demand active powder by high-temperature burning and then adds anhydrite. Compared with active components such as cement and admixture, it has a higher water demand and good activity, and is more suitable for the solidification of high-water-content sludge. Cooperating with a reinforcing agent composed of C-S-H crystal nuclei, silicon nitride nanowhiskers and methyldiethanolamine can improve the mechanical properties of the solidified body at low temperature.

[0016] Preferably, the thickening agent is composed of polyaluminum sulfate, ammonium sulfate and β-cyclodextrin mixed in a mass ratio of (2-3):(1-2):(4-5).

[0017] In the present invention, a part of water-absorbing resin is added to absorb the water in the sludge. It is found during the test that when it is used in combination with a thickener composed of polyaluminum sulfate, ammonium sulfate, and β-cyclodextrin, it can ensure the mechanical properties of the solidified body, which is superior to adding only water-absorbing resin or other types of thickeners. However, cellulose ether thickeners are likely to cause poor forming effect of the slurry and damage the mechanical properties.

[0018] Preferably, the strength grade of the ordinary Portland cement is ≥42.5. More preferably, the ordinary Portland cement is of grade 52.5, and the content of C3S mineral is not less than 70%.

[0019] Preferably, the strength grade of the sulfoaluminate cement is ≥52.5. More preferably, the sulfoaluminate cement is of grade 72.5, and the specific surface area is 350 - 400m 2 / kg.

[0020] Preferably, the D50 of the fly ash is 1 - 3μm.

[0021] Preferably, the D50 of the silica fume is 1 - 2μm.

[0022] Preferably, the mineral powder is S140 ultra-fine mineral powder, and the D50 is 3 - 5μm.

[0023] Preferably, in the preparation process of the high water-demand active powder, the high-temperature melting temperature is 2000 - 2100°C, the heat preservation time is 10 - 15min, and the ultra-fine grinding is carried out by a jet mill.

[0024] Preferably, the specific surface area of the high water-demand active powder is 900 - 1000cm 2 / g.

[0025] Preferably, the C-S-H crystal nucleus is prepared by the coprecipitation method.

[0026] Preferably, the particle size of the silicon nitride nanowhiskers is less than 300nm.

[0027] Preferably, the water reducer is a polycarboxylate water reducer.

[0028] Preferably, the particle size of the water-absorbing resin is 0.1 - 0.3mm.

[0029] Preferably, the retarder is at least one of tartaric acid and boric acid.

[0030] Preferably, the dispersant is at least one of sodium hexametaphosphate, sodium polyacrylate, and sodium pyrophosphate.

[0031] The present invention also relates to a preparation method of the above-mentioned low-temperature high-water-content sludge solidifying agent. Specifically, it includes the following steps: Weigh each raw material according to parts by mass and mix them evenly to obtain it.

[0032] The present invention also relates to the application of the above-mentioned low-temperature high-water-content sludge solidifying agent in the solidification of high-water-content sludge.

[0033] The present invention has the following technical advantages:

[0034] 1. The present invention uses composite cement, ultra-fine mineral admixture and high-water-demand active powder as cementitious materials, which can realize the solidification of high-water-content sludge, and can effectively improve the early-age strength of the solidified body in a low-temperature environment and the stable later-age strength growth.

[0035] 2. The high-water-demand active powder and the strengthening agent of the present invention can improve the hydration process of the cementitious material system in a low-temperature environment and promote the low-temperature solidification of high-water-content sludge.

[0036] 3. The water-absorbing resin and the thickening agent composed of polyaluminum sulfate, ammonium sulfate and β-cyclodextrin can fully absorb the free water in the sludge.

[0037] 4. The solidifying agent of the present invention has quick setting and high strength, and the solidified body has good erosion resistance.

[0038] 5. The preparation process of the solidifying agent of the present invention is simple. After the sludge is solidified, it can be used for soft foundation treatment, road construction and other projects, realizing the resource utilization of high-water-content submarine sludge. Specific Embodiments

[0039] To characterize the technical effects of the present invention, a solidifying agent was prepared and mixed with submarine sludge with a water content of 100%. The addition amount of the solidifying agent was 30% of the mass of the sludge. In an environment of 5°C, specimens were formed according to the provisions of JTG E51-2009 and unconfined compressive strength tests were carried out. The erosion resistance performance test used a water flow of 4 m / s. During the test, the ordinary Portland cement was of grade 52.5, the sulfoaluminate cement was of grade 72.5, and boric acid was selected as the retarder.

[0040] Example 1

[0041] The solidifying agent is composed of the following raw materials in parts by weight: 12 parts of ordinary Portland cement, 27 parts of sulfoaluminate cement, 26 parts of ultra-fine mineral admixture, 28 parts of high-water-demand active powder, 7 parts of strengthening agent, 0.8 part of polycarboxylate water reducer, 0.6 part of water-absorbing resin, 0.5 part of thickening agent, 0.6 part of retarder, and 1.5 parts of sodium hexametaphosphate.

[0042] The ultra-fine mineral admixture is composed of ultra-fine fly ash, silica fume and mineral powder mixed in a mass ratio of 2:0.4:2.

[0043] The preparation process of the high water demand active powder is as follows: CaO, Al2O3 and SiO2 are uniformly mixed at a mass ratio of 1:0.6:3, tableted, kept at a high temperature of 1200 °C for melting for 12 min, quenched, and then ground to obtain fine powder. The fine powder and anhydrite are mixed evenly at a mass ratio of 7:3 and ultrafinely ground to a specific surface area of 950 cm 2 / g, and then it is obtained.

[0044] The enhancer is composed of C-S-H crystal nuclei, silicon nitride nanowhiskers and methyldiethanolamine mixed at a mass ratio of 3:0.4:1.

[0045] The thickener is composed of polyaluminum sulfate, ammonium sulfate and β-cyclodextrin mixed at a mass ratio of 2:2:4.

[0046] After testing, in an environment of 5 °C, the unconfined compressive strength of the solidified body is 0.22 MPa at 3 h, 0.85 MPa at 12 h, 1.85 MPa at 1 d, and 5.76 MPa at 28 d. The solidified sludge is non-dispersible underwater and can resist a water flow of 4 m / s.

[0047] Example 2

[0048] The curing agent is composed of the following raw materials in parts by weight: 15 parts of ordinary Portland cement, 26 parts of sulfoaluminate cement, 22 parts of ultrafine mineral admixture, 30 parts of high water demand active powder, 6 parts of enhancer, 0.8 part of polycarboxylate water reducer, 1 part of water absorbent resin, 0.2 part of thickener, 0.7 part of retarder, and 1.6 parts of sodium hexametaphosphate.

[0049] The ultrafine mineral admixture is composed of ultrafine fly ash, silica fume and ore powder mixed at a mass ratio of 1:0.5:2.5.

[0050] The preparation process of the high water demand active powder is as follows: CaO, Al2O3 and SiO2 are uniformly mixed at a mass ratio of 1:0.6:3, tableted, kept at a high temperature of 1200 °C for melting for 12 min, quenched, and then ground to obtain fine powder. The fine powder and anhydrite are mixed evenly at a mass ratio of 7:3 and ultrafinely ground to a specific surface area of 950 cm 2 / g, and then it is obtained.

[0051] The enhancer is composed of C-S-H crystal nuclei, silicon nitride nanowhiskers and methyldiethanolamine mixed at a mass ratio of 4:0.2:1.

[0052] The thickener is composed of polyaluminum sulfate, ammonium sulfate and β-cyclodextrin mixed at a mass ratio of 3:1:5.

[0053] After testing, under the environment of 5°C, the unconfined compressive strength of the solidified body is 0.26 MPa at 3 h, 0.91 MPa at 12 h, 1.92 MPa at 1 d, and 5.90 MPa at 28 d. The solidified silt does not disperse underwater and can resist a water flow of 4 m / s.

[0054] Comparative Example 1

[0055] The solidifying agent is composed of the following raw materials in parts by weight: 15 parts of ordinary Portland cement, 26 parts of sulfoaluminate cement, 10 parts of silica fume, 12 parts of S95-grade mineral powder, 30 parts of high water-demand active powder, 6 parts of reinforcing agent, 0.8 part of polycarboxylate water-reducing agent, 1 part of water-absorbing resin, 0.2 part of thickening agent, 0.7 part of retarder, and 1.6 parts of sodium hexametaphosphate.

[0056] The preparation process of the high water-demand active powder is as follows: CaO, Al2O3, and SiO2 are uniformly mixed in a mass ratio of 1:0.6:3, tableted, kept at a high temperature of 1200°C for melting and heat preservation for 12 min, quenched rapidly, and ground into fine powder after grinding. The fine powder and anhydrite are mixed evenly in a mass ratio of 7:3 and ultrafinely ground to a specific surface area of 950 cm 2 / g, thus obtained.

[0057] The reinforcing agent is composed of C-S-H crystal nuclei, silicon nitride nanowhiskers, and methyldiethanolamine mixed in a mass ratio of 4:0.2:1.

[0058] The thickening agent is composed of polyaluminum sulfate, ammonium sulfate, and β-cyclodextrin mixed in a mass ratio of 3:1:5.

[0059] After testing, under the environment of 5°C, the unconfined compressive strength of the solidified body is 0.19 MPa at 3 h, 0.77 MPa at 12 h, 1.51 MPa at 1 d, and 4.36 MPa at 28 d. The solidified silt does not disperse underwater and can resist a water flow of 4 m / s.

[0060] Comparative Example 2

[0061] The solidifying agent is composed of the following raw materials in parts by weight: 15 parts of ordinary Portland cement, 26 parts of sulfoaluminate cement, 52 parts of ultrafine mineral admixture, 6 parts of reinforcing agent, 0.8 part of polycarboxylate water-reducing agent, 1 part of water-absorbing resin, 0.2 part of thickening agent, 0.7 part of retarder, and 1.6 parts of sodium hexametaphosphate.

[0062] The ultrafine mineral admixture is composed of ultrafine fly ash, silica fume, and mineral powder mixed in a mass ratio of 1:0.5:2.5.

[0063] The reinforcing agent is composed of C-S-H crystal nuclei, silicon nitride nanowhiskers, and methyldiethanolamine mixed in a mass ratio of 4:0.2:1.

[0064] The thickener is composed of polyaluminum sulfate, ammonium sulfate and β-cyclodextrin mixed in a mass ratio of 3:1:5.

[0065] After testing, at 5°C, the solidified body has no strength in 3 hours, the unconfined compressive strength is 0.34 MPa in 12 hours, 1.05 MPa in 1 day, and 2.17 MPa in 28 days. The solidified sludge is dispersed underwater.

[0066] Comparative Example 3

[0067] The curing agent is composed of the following raw materials in parts by weight: 15 parts of ordinary Portland cement, 26 parts of sulfoaluminate cement, 28 parts of ultra-fine mineral admixture, 30 parts of high water demand active powder, 0.8 part of polycarboxylate water reducer, 1 part of water absorbent resin, 0.2 part of thickener, 0.7 part of retarder, and 1.6 parts of sodium hexametaphosphate.

[0068] The ultra-fine mineral admixture is composed of ultra-fine fly ash, silica fume and mineral powder mixed in a mass ratio of 1:0.5:2.5.

[0069] The preparation process of the high water demand active powder is as follows: CaO, Al2O3 and SiO2 are uniformly mixed in a mass ratio of 1:0.6:3, tableted, kept at a high temperature of 1200°C for 12 minutes, quenched rapidly, ground into fine powder after grinding, and the fine powder and anhydrite are mixed evenly in a mass ratio of 7:3, and ultra-finely ground to a specific surface area of 950 cm 2 / g, thus obtained.

[0070] The thickener is composed of polyaluminum sulfate, ammonium sulfate and β-cyclodextrin mixed in a mass ratio of 3:1:5.

[0071] After testing, at 5°C, the solidified body has no strength in 3 hours, the unconfined compressive strength is 0.60 MPa in 12 hours, 1.36 MPa in 1 day, and 4.05 MPa in 28 days. The solidified sludge is dispersed underwater.

[0072] Comparative Example 4

[0073] The curing agent is composed of the following raw materials in parts by weight: 15 parts of ordinary Portland cement, 26 parts of sulfoaluminate cement, 22 parts of ultra-fine mineral admixture, 31.2 parts of high water demand active powder, 6 parts of enhancer, 0.8 part of polycarboxylate water reducer, 0.7 part of retarder, and 1.6 parts of sodium hexametaphosphate.

[0074] The ultra-fine mineral admixture is composed of ultra-fine fly ash, silica fume and mineral powder mixed in a mass ratio of 1:0.5:2.5.

[0075] The preparation process of the high water demand active powder is as follows: CaO, Al2O3 and SiO2 are uniformly mixed in a mass ratio of 1:0.6:3, tableted, melted at a high temperature of 1200 °C and kept warm for 12 min, quenched, and then ground to obtain fine powder. The fine powder and anhydrite are uniformly mixed in a mass ratio of 7:3 and ultrafinely ground to a specific surface area of 950 cm 2 / g, thus obtaining it.

[0076] The enhancer is composed of C-S-H crystal nuclei, silicon nitride nanowhiskers and methyldiethanolamine mixed in a mass ratio of 4:0.2:1.

[0077] After testing, at 5 °C, the unconfined compressive strength of the solidified body is 0.21 MPa at 3 h, 0.80 MPa at 12 h, 1.59 MPa at 1 d, and 4.95 MPa at 28 d. The solidified sludge is slightly dispersed underwater.

[0078] Comparative Example 5

[0079] The curing agent is composed of the following raw materials in parts by weight: 15 parts of ordinary Portland cement, 26 parts of sulfoaluminate cement, 22 parts of ultrafine mineral admixture, 30 parts of high water demand active powder, 6 parts of enhancer, 0.8 part of polycarboxylate water reducer, 1 part of water absorbent resin, 0.2 part of hydroxypropyl methylcellulose ether, 0.7 part of retarder, 1.6 parts of sodium hexametaphosphate.

[0080] The ultrafine mineral admixture is composed of ultrafine fly ash, silica fume and ore powder mixed in a mass ratio of 1:0.5:2.5.

[0081] The preparation process of the high water demand active powder is as follows: CaO, Al2O3 and SiO2 are uniformly mixed in a mass ratio of 1:0.6:3, tableted, melted at a high temperature of 1200 °C and kept warm for 12 min, quenched, and then ground to obtain fine powder. The fine powder and anhydrite are uniformly mixed in a mass ratio of 7:3 and ultrafinely ground to a specific surface area of 950 cm 2 / g, thus obtaining it.

[0082] The enhancer is composed of C-S-H crystal nuclei, silicon nitride nanowhiskers and methyldiethanolamine mixed in a mass ratio of 4:0.2:1.

[0083] After testing, at 5 °C, the unconfined compressive strength of the solidified body is 0.18 MPa at 3 h, 0.63 MPa at 12 h, 1.52 MPa at 1 d, and 4.77 MPa at 28 d. The solidified sludge is partially dispersed underwater.

[0084] 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 them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and 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 various embodiments of the present invention.

Claims

1. A low temperature high moisture content sludge solidifying agent, characterized in that: The invention is composed of the following raw materials in parts by weight: 10-15 parts of ordinary Portland cement, 25-30 parts of sulphoaluminate cement, 20-28 parts of ultrafine mineral admixture, 20-30 parts of high water-requiring active powder, 6-8 parts of reinforcing agent, 0.1-1 part of water reducing agent, 0.1-1 part of water-absorbing resin, 0.1-0.5 part of thickener, 0.1-1 part of retarder, 0.1-2 parts of dispersant, The ultrafine mineral admixture is prepared by mixing ultrafine fly ash, silica ash and mineral powder in a mass ratio of (1-2):(0.3-0.5):(2-3). The high water-requiring active powder preparation process comprises: uniformly mixing CaO, Al2O3 and SiO2 in a mass ratio of 1:(0.5-0.8):(2-3), tableting, high-temperature melting, rapid cooling, grinding to obtain fine powder, uniformly mixing fine powder and anhydrite in a mass ratio of (6.5-7):(3-4), ultrafine grinding to obtain, the high-temperature melting temperature is 2000-2100°C, the heat preservation time is 10-15min, and the ultrafine grinding adopts a jet mill, The reinforcing agent is prepared by mixing CSH crystal nuclei, silicon nitride nano whiskers and methyldiethanolamine in a mass ratio of (0.5-5):(0.1-1):

1. The thickener is prepared by mixing polyaluminium sulfate, ammonium sulfate and beta-cyclodextrin in a mass ratio of (2-3):(1-2):(4-5).

2. The low temperature high moisture content sludge solidifying agent according to claim 1, characterized in that: The strength grade of the ordinary Portland cement is ≥42.5, and the strength grade of the sulphoaluminate cement is ≥52.

5.

3. The low temperature high moisture content sludge solidifying agent according to claim 1, characterized in that: The fly ash has a D50 of 1-3 μm, the silica ash has a D50 of 1-2 μm, and the mineral powder is S140 ultrafine mineral powder, with a D50 of 3-5 μm.

4. The low temperature high moisture content sludge solidifying agent according to claim 1, characterized in that: The specific surface area of ​​the high water-demand active powder is 900-1000 cm2 / g.

5. The low temperature high moisture content sludge solidifying agent according to claim 1, characterized in that: The CSH crystal nucleus is prepared by a co-precipitation method, and the particle size of the silicon nitride nano whisker is less than 300 nm.

6. The low temperature high moisture content sludge solidifying agent according to claim 1, characterized in that: The water reducing agent is a polycarboxylic acid water reducing agent, and the particle size of the water absorbing resin is 0.1-0.3 mm.

7. The low temperature high moisture content sludge solidifying agent according to claim 1, characterized in that: The retarder is at least one of tartaric acid and boric acid, and the dispersant is at least one of sodium hexametaphosphate, sodium polyacrylate and sodium pyrophosphate.

8. The method for preparing the low-temperature high-water content sludge solidifying agent according to any one of claims 1 to 7, characterized in that: The method comprises the following steps: weighing various raw materials according to mass parts, and mixing them evenly to obtain the product.

9. Use of the low-temperature high-water content sludge solidifying agent according to any one of claims 1 to 7 in the solidification of high-water content sludge.