CN118184183A

CN118184183A - Silt curing agent

Info

Publication number: CN118184183A
Application number: CN202410293515.9A
Authority: CN
Inventors: 符文妍; 黄宏; 沙马什布; 陈建宝; 刘明旺; 蒋菊生
Original assignee: HAINAN LANDAO ENVIRONMENTAL PROTECTION INDUSTRY CO LTD
Current assignee: HAINAN LANDAO ENVIRONMENTAL PROTECTION INDUSTRY CO LTD
Priority date: 2024-03-14
Filing date: 2024-03-14
Publication date: 2024-06-14

Abstract

The invention discloses a sludge curing agent, and relates to the technical field of curing agents. The curing agent consists of a cementing material and an additive; the cementing material consists of cement, mineral powder, fly ash and water-washed coal ash, and the additive consists of alkali-exciting agent, sulfur-aluminum cement and desulfurized gypsum. The sludge curing agent can overcome the difficult problem of curing high-water-content and high-sludge-content sludge, can carry out modification and curing treatment on the high-water-content sludge which is in a plastic flowing state and has zero unconfined compressive strength, improves the mechanical property of the sludge, can be used for constructing a highway subbase, realizes the utilization of solid waste resources such as slag, water cinder and the like, solves the problem of water and soil environmental pollution, and brings good economic benefit.

Description

Silt curing agent

Technical Field

The invention relates to the technical field of curing agents, in particular to a sludge curing agent.

Background

The curing treatment is a main treatment mode for recycling the waste soil as the geotechnical material. The waste soil refers to waste soil with high water content such as sea sludge, dredged soil, slurry balance shield residue soil and the like, which cannot be directly utilized. The curing treatment is to mix a large amount of curing agent into the waste soil, mix, pour and cure the waste soil, and harden the waste soil into an integrally hard hardened body, namely the solidified soil. The solidified soil has high strength and difficult deformation, has the functions of stabilizing and wrapping various harmful substances in the waste soil, can solve the problem of harm of the waste soil to the environment, and can be applied to practical engineering.

The silt is engineering waste soil with high water content and high mud content, and cannot be recycled because of the physical and mechanical properties such as a flowing plastic state, zero unconfined compressive strength and the like and no engineering application property. With the continuous development of society, people's environmental awareness is increasingly strengthened, and research on modern sediment of various enriched pollutants such as silt is carried out on the sediment, and researchers at home and abroad are many aspects of resource utilization, and the goal is to carry out pollution-free treatment on engineering waste soil such as silt, avoid causing secondary pollution of environment, and simultaneously can apply the solidified silt sample to actual construction engineering, thereby realizing win-win of environment and economy.

Although researchers at home and abroad develop the research and obtain certain results, the method still has some defects, such as generally higher cost of various curing agents in the current market, and the development of a plurality of dredging sludge application projects is restricted to a great extent; the current research direction of curing agents is focused on mechanical properties, but the physical properties are ignored, and the main reason that many silt is difficult to directly use in highway engineering is that the curing agents are limited by the ultrahigh water content and the high mud content, and the physical and mechanical properties are zero because of the molding state.

Therefore, the curing agent which can be applied to dredging sludge with high water content and high mud content is provided, excellent sludge curing effect is realized, and the curing agent has positive significance for promoting the application of curing sludge.

Disclosure of Invention

The invention aims to provide a sludge curing agent for solving the problems of the prior art and realizing the efficient curing of dredging sludge with high water content and high sludge content.

In order to achieve the above object, the present invention provides the following solutions:

one of the technical schemes of the invention is to provide a silt curing agent which consists of cementing materials and additives;

The cementing material consists of cement, mineral powder, fly ash and water-washed coal ash;

the additive consists of an alkali-activated agent, aluminum sulfate cement and desulfurized gypsum.

As a further preferred aspect of the present invention, the cementing material is composed of 30% -50% of cement, 10% -40% of mineral powder, 10% -60% of fly ash and 10% -30% of water-washed coal ash, based on 100% of the total mass of the cementing material;

Based on the total mass of the cementing material, the alkali-activator is 0.15-0.35% of the total mass of the cementing material, the aluminum sulfate cement is 0.15-0.35% of the total mass of the cementing material, and the desulfurized gypsum is 1.35-3.45% of the total mass of the cementing material.

As a further preferred aspect of the present invention, the cement is a conventional pozzolanic portland cement; the mineral powder is blast furnace slag powder. The blast furnace slag is subjected to drying, grinding and other processes to obtain slag micropowder, which is also called mineral powder.

As a further preferable aspect of the present invention, the water-washed coal ash is coal ash produced by a petrochemical plant, and is obtained by water washing, drying and grinding; the modulus of the alkali-activated agent is 1.2-1.6.

More preferably, the washed fly ash passes through a 100-mesh sieve, and the screen residue is 0%.

More preferably, the alkali-activated agent is prepared from sodium silicate and sodium hydroxide; wherein, the sodium hydroxide is AR grade.

As a further preferred aspect of the present invention, the aluminosulfate cement is low-alkalinity aluminosulfate cement; the alkali content of the low-alkalinity sulphoaluminate cement is not higher than 0.6%, wherein the alkali content is calculated as equivalent sodium oxide (Na ₂O+0.658K₂ O); the desulfurized gypsum is dihydrate gypsum.

More preferably, the dihydrate gypsum is obtained by drying desulfurization gypsum at 50 ℃.

The second technical scheme of the invention is to provide a preparation method of the sludge curing agent, which comprises the following steps:

firstly, mixing components except the alkaline excitant, and then adding the alkaline excitant into the obtained mixture to obtain the sludge curing agent.

The preparation process of the silt curing agent comprises the steps of mixing dry powder and adding an alkaline excitant, wherein cementing material cement, mineral powder, fly ash and water-washed coal ash are firstly mixed with aluminum sulfate cement and desulfurized gypsum by dry powder stirring, and then the obtained dry powder mixture is stored in a sealing way for standby; the alkaline activator component is stored separately. In preparation for the solidification of the sludge, an alkaline activator is added to the dry powder mixture, and the obtained sludge solidifying agent is added to the sludge to be solidified for solidification.

More preferably, when dry powder stirring and mixing is performed, stirring is performed at a low speed for 30 minutes or more.

The third technical scheme of the invention is to provide the application of the sludge curing agent in curing dredging sludge.

The fourth technical scheme of the invention is to provide the application of the sludge curing agent in curing dredged sludge in Hainan area.

As a further preferred aspect of the invention, the sludge curing agent comprises 7-10% of the total mass of the sludge.

As a further preferred aspect of the invention, the dredged silt has a silt content of 15-85% and a water content of 5-70%.

The composition, physical and mechanical properties, pollutants and the like of the sludge in different areas are different, and the sludge curing agent can be prepared according to local conditions to obtain the curing agent more suitable for the local sludge property.

The sludge curing agent has low price and can meet the curing requirements of dredging sludge with high water content and high sludge content.

The sludge curing agent disclosed by the invention has the following functions in the sludge curing process:

And (3) cement: the cement mineral phase C ₃S、C₂S、C₃A、C₄ AF and calcium sulfate generate hydration reaction to generate hydration products such as C-S-H, C-A-H, AFm, AFt, CH, and the hydration products and the cementing action form among the powder particles with different particle sizes, sand grains and gravel grains form a structural whole with certain strength, so that the strength of the solidified soil is improved. The CAO in the cement generates severe hydration reaction to generate Ca (OH) ₂, and the ionized OH ^- ions increase the pH of the soil sample and provide an alkaline environment for chemical excitation.

Mineral powder: the slag taking CaO-Al ₂O₃-SiO₂ system as the main material has lower activity, weaker curing effect on sludge and poor use effect when being directly used as a sludge curing agent, so that the glass phase content and the volcanic ash reactivity of the slag need to be stimulated and improved by adopting a certain method. On one hand, the fineness of the particles is reduced through physical excitation (mechanical grinding) to increase the specific surface area and further increase the reaction rate; on the other hand, by a chemical excitation method of adding an alkali excitant (prepared by water glass and sodium hydroxide) into the curing agent, the breakage of a silicon oxygen bond, an aluminum oxygen bond and a Si-O-Al bond is promoted, and the reactivity and the mechanical properties of the solid waste base cementing material are improved.

Fly ash: the fly ash is the main solid waste discharged from coal-fired power plants, the early fly ash has lower activity and can only be used for filling, and the soluble substances contained in the early fly ash gradually react with Ca (OH) ₂ along with the continuous growth of the age to generate a gelled substance with certain strength.

Washing coal ash: the cinder is a sintered pozzolanic material, contains a large amount of siliceous glass bodies, active silica, active alumina and the like, has stronger activity and hydraulic gelation performance after being ground, and can effectively improve the solidification strength of sludge.

Alkali-exciting agent: under normal temperature, industrial solid wastes such as fly ash, mineral powder and the like can form a cementing material with a three-dimensional space network structure consisting of [ SiO ₄ ] and [ AlO ₄ ] tetrahedral structural units by utilizing the action of alkali excitation and the bond breaking recombination process of depolymerizing and polycondensation after depolymerizing silicon oxygen bonds and aluminum oxygen bonds in an alkali excitation liquid environment, so that the mechanical property of sludge solidification is improved. Because the geopolymer has the characteristics of high early strength and quick setting time, the setting time and strength requirements of engineering can be met; the alkali excitation product has compact structure, weak neutralization reaction and strong acid erosion resistance of the hardened body.

Aluminum sulfate cement (sulfoaluminate cement): because the sludge curing agent contains a large amount of C ₄A₃ minerals, the sludge curing agent has the characteristics of high early strength, high freezing resistance, corrosion resistance, high impermeability, expansion performance, low alkalinity and the like, and improves the sludge curing efficiency.

Desulfurization gypsum: the strong alkaline environment generated by the desulfurized gypsum is beneficial to depolymerizing the slag glass bulk phase structure to generate reactive [ SiO ₄]^4- and [ AlO ₄]^5- tetrahedron structures, so that the speed of hydration reaction and pozzolan reaction is improved, and more gelled products are generated. The desulfurization gypsum is hydrated to generate a large amount of SO ₄ ^2- which reacts with C-S-H to generate needle-shaped and short-rod-shaped expansion hydrate AFt, which can fill gaps in a soil sample, SO that the soil body structure is more compact, and meanwhile, the needle-shaped AFt can form a grid structure, SO that the physical and mechanical properties of solidified soil are changed, and the strength of the solidified soil is improved.

The invention discloses the following technical effects:

The sludge curing agent can overcome the difficult problem of curing high-water-content and high-sludge-content sludge, can carry out modification and curing treatment on the high-water-content sludge which is in a plastic flowing state and has zero unconfined compressive strength, improves the mechanical property of the sludge, can be used for constructing a highway subbase, realizes the utilization of solid waste resources such as slag, water cinder and the like, solves the problem of water and soil environmental pollution, and brings good economic benefit.

Detailed Description

Various exemplary embodiments of the invention will now be described in detail, which should not be considered as limiting the invention, but rather as more detailed descriptions of certain aspects, features and embodiments of the invention.

It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In addition, for numerical ranges in this disclosure, it is understood that each intermediate value between the upper and lower limits of the ranges is also specifically disclosed. Every smaller range between any stated value or stated range, and any other stated value or intermediate value within the stated range, is also encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference for the purpose of disclosing and describing the methods and/or materials associated with the documents. In case of conflict with any incorporated document, the present specification will control.

It will be apparent to those skilled in the art that various modifications and variations can be made in the specific embodiments of the invention described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from consideration of the specification of the present invention. The specification and examples of the present invention are exemplary only.

As used herein, the terms "comprising," "including," "having," "containing," and the like are intended to be inclusive and mean an inclusion, but not limited to.

The dredging sludge used in the embodiment of the invention is the dredging sludge with high water content and high mud content of the new Yingwan section engineering of the tourist highway in Hainan province.

In the following examples of the invention, the cement used was a conventional pozzolanic portland cement (pp 325) with a specific surface area of 392.9m ²/kg; the mineral powder is blast furnace slag powder, and the specific surface area is 365.4m ²/kg; the fly ash is the fly ash of a coal-fired power plant, and the specific surface area is 409.8m ²/kg; the water-washed coal ash is coal slag produced by petrochemical plants, and is obtained by water washing, oven drying (50+/-5 ℃) and mechanical ball milling, and is sieved by a 100-mesh sieve, wherein the screen residue is 0%; the modulus of the alkaline excitant is 1.2, and the alkaline excitant is prepared by water glass with the modulus of 3.28 and sodium hydroxide (AR level) solid particles; the used aluminum sulfate cement is low-alkalinity aluminum sulfate cement (alkali content is 0.3%), and the specific surface area is 443.5m ²/kg.

In the following embodiments of the present invention, a formula for calculating the water content of the dredging sludge is shown in formula (1):

Water content ω= (wet soil mass m-dry soil mass m _s)/dry soil mass m _s x 100% formula (1);

Sieving, washing and drying the dredged sludge through an 80-micrometer standard sieve; the sample mass before screening and washing is marked as m ₀, the sample mass after drying is marked as m ₁, and the mud content of the dredging mud is calculated according to the formula (2):

Dredging sludge content= (m ₀-m₁)/m₀ x 100% formula (2).

Example 1

(1) And (3) drying the wet desulfurized gypsum in an oven at 50 ℃ for 4 hours to obtain dihydrate gypsum, and storing the dihydrate gypsum in a sealing manner for standby.

(2) Placing cement, mineral powder, fly ash, water-washed fly ash, aluminum sulfate cement and desulfurized gypsum into a cement mortar stirrer in a dry powder stirring manner, and stirring at a low speed of 140+/-5 r/min for 30min uniformly to obtain a dry powder mixture; and then mixing the dry powder mixture with an alkaline activator to obtain the sludge curing agent.

Wherein cement, mineral powder, fly ash and water-washed fly ash are gel material components; the sulfur aluminum cement, the desulfurized gypsum and the alkaline excitant are used as additive components; the cement accounts for 50% by weight, the mineral powder accounts for 20% by weight, the fly ash accounts for 20% by weight and the water-washed fly ash accounts for 10% by weight of 100% by weight of the total cementing material; based on the total mass of the cementing material, the alkali-activator is 0.15% of the total mass of the cementing material, the aluminum sulfate cement is 0.20% of the total mass of the cementing material, and the total mass of the desulfurized gypsum cementing material is 2.45%.

(3) Adding a sludge curing agent accounting for 5% of the total mass of the dredged sludge with 25% of natural water content and 19% of sludge content into the dredged sludge, placing the mixture into a cement mortar stirrer, stirring at a low speed of 140+/-5 r/min for 60s, stirring at a high speed of 285+/-10 r/min for 30s, stopping 90s, stirring at a high speed of 285+/-10 r/min for 60s, and stopping stirring to obtain the required sludge curing soil.

Placing the obtained silt solidified soil in a plastic triple mold with the thickness of 70.7mm and 70.7mm on a compaction table, compacting and compaction forming by two layers, and scraping the surface of a sample by using a ruler to obtain three parallel test blocks.

The test block and the die are placed under standard curing conditions that the temperature is 20+/-2 ℃ and the humidity is more than or equal to 95%, and the surface of the test block is wrapped with a plastic film, so that the hydration reaction is promoted to be complete, and cracks on the surface of the test block are avoided; and demolding the test block after 5d, wrapping the test block by using a plastic film, and continuing to maintain the test block for 7d years under standard maintenance conditions.

The test block is dark gray, the inside of the test block is compact and has no defects, and the surface of the test block has no obvious cracks.

The test block is placed on a WDW-10 electronic universal tester (microcomputer controlled), and the unconfined compressive strength test is carried out on the test sample according to the loading rate of 10mm/min, wherein the 7d compressive strength is 1.15MPa.

Example 2

The difference from example 1 is only that the natural water content of the dredging sludge is 60.3% and the sludge content is 84%; the addition amount of the sludge curing agent is 9% of the mass of the dredged sludge.

The mechanical properties were tested using the test method of example 1, and the results showed that: the 7d compressive strength is 0.35MPa.

Example 3

The only difference from example 2 is that the sludge solidifying agent is added in an amount of 10% of the mass of the dredging sludge.

The mechanical properties were tested using the test method of example 1, and the results showed that: the 7d compressive strength is 0.45MPa.

Example 4

The only difference from example 1 is that the sludge curing agent comprises the following components in proportion: the cement accounts for 50% by weight, the mineral powder accounts for 30% by weight, the fly ash accounts for 10% by weight and the water-washed fly ash accounts for 10% by weight of 100% by weight of the total cementing material; based on the total mass of the cementing material, the alkali-activator is 0.20% of the total mass of the cementing material, the aluminum sulfate cement is 0.15% of the total mass of the cementing material, and the total mass of the desulfurized gypsum cementing material is 2.95%.

The mechanical properties were tested using the test method of example 1, and the results showed that: the 7d compressive strength was 1.25MPa.

Example 5

Wherein cement, mineral powder, fly ash and water-washed fly ash are gel material components; the sulfur aluminum cement, the desulfurized gypsum and the alkaline excitant are used as additive components; the cement accounts for 50% by weight, the mineral powder accounts for 30% by weight, the fly ash accounts for 10% by weight and the water-washed fly ash accounts for 10% by weight of 100% by weight of the total cementing material; based on the total mass of the cementing material, the alkali-activator is 0.20% of the total mass of the cementing material, the aluminum sulfate cement is 0.15% of the total mass of the cementing material, and the total mass of the desulfurized gypsum cementing material is 2.95% (the same as the sludge curing agent formula of the example 4).

(3) Adding a sludge curing agent accounting for 9% of the total mass of the dredged sludge (the dredged sludge in the same example 2) with the natural water content of 60.3% and the sludge content of 84%, placing the mixture into a cement mortar stirrer, stirring at a low speed of 140+/-5 r/min for 60s, stirring at a high speed of 285+/-10 r/min for 30s, stopping 90s, stirring at a high speed of 285+/-10 r/min for 60s, and stopping stirring to obtain the required sludge curing soil.

The mechanical properties were tested using the test method of example 1, and the results showed that: the 7d compressive strength is 0.42MPa.

Example 6

The only difference from example 5 is that the sludge solidifying agent is added in an amount of 10% of the mass of the dredging sludge.

The mechanical properties were tested using the test method of example 1, and the results showed that: the 7d compressive strength is 0.50MPa.

Example 7

The only difference from example 1 is that the sludge curing agent comprises the following components in proportion: the cement accounts for 40% by weight, the mineral powder accounts for 20% by weight, the fly ash accounts for 20% by weight and the water-washed fly ash accounts for 20% by weight of 100% by weight of the total cementing material; based on the total mass of the cementing material, the alkali-activator is 0.15% of the total mass of the cementing material, the aluminum sulfate cement is 0.15% of the total mass of the cementing material, and the total mass of the desulfurized gypsum cementing material is 1.35%.

The mechanical properties were tested using the test method of example 1, and the results showed that: the 7d compressive strength is 1.14MPa.

Example 8

Wherein cement, mineral powder, fly ash and water-washed fly ash are gel material components; the sulfur aluminum cement, the desulfurized gypsum and the alkaline excitant are used as additive components; the cement accounts for 40% by weight, the mineral powder accounts for 20% by weight, the fly ash accounts for 20% by weight and the water-washed fly ash accounts for 20% by weight of 100% by weight of the total cementing material; based on the total mass of the cementing material, the alkali-activator is 0.15% of the total mass of the cementing material, the aluminum sulfate cement is 0.15% of the total mass of the cementing material, and the total mass of the desulfurized gypsum cementing material is 1.35% (the same as the sludge curing agent formula of the example 7).

The mechanical properties were tested using the test method of example 1, and the results showed that: the 7d compressive strength is 0.52MPa.

Example 9

The only difference from example 8 is that the sludge solidifying agent is added in an amount of 10% of the mass of the dredging sludge.

The mechanical properties were tested using the test method of example 1, and the results showed that: the 7d compressive strength was 0.41MPa.

Comparative example 1

The difference from example 1 is that the cementing material in the step (2) is not added with fly ash, and the cementing material is composed of cement, mineral powder and water-washed fly ash according to the mass ratio of 5:2:1.

The mechanical properties were tested using the test method of example 1, and the results showed that: the 7d compressive strength is 0.55MPa.

Comparative example 2

The difference from example 1 is that the cementing material in the step (2) is not added with water-washed fly ash, and the cementing material is composed of cement, mineral powder and fly ash according to the mass ratio of 5:2:2.

The mechanical properties were tested using the test method of example 1, and the results showed that: the 7d compressive strength was 0.43MPa.

Comparative example 3

The difference from example 1 is only that no alkali-activator is added, the sulfur-aluminum cement is 0.20% of the total mass of the cementing material, and the total mass of the desulfurized gypsum cementing material is 2.45%.

The mechanical properties were tested using the test method of example 1, and the results showed that: the 7d compressive strength was 0.61MPa.

The data show that the 7d unconfined compressive strength obtained in the examples 1-9 can meet the strength requirement of the construction soil of the three-level highway subbase layer; the curing agent proportioning scheme in the embodiment 1 is the optimal selection scheme in consideration of the requirements of meeting engineering requirements and saving construction cost.

According to the data of comparative examples 1-3, the strength of the silt solidified soil can be effectively improved by the fly ash and the water-washed fly ash, wherein the water-washed fly ash has better effect; the result of comparative example 3 verifies that the alkali-activated agent has positive effect on sludge solidification, and the alkali-activated agent can form inorganic gelled substances, so that the gelled substances have the characteristics of compact structure, weak neutralization reaction and the like, and the mechanical properties of the sludge solidified soil can be effectively improved.

For dredging sludge with different water content and mud content working conditions, the experimental purpose can be achieved by adjusting the proportion of each component and the external mixing amount of the curing agent. The invention realizes the resource utilization of the dredging sludge with high water content and high mud content, and has important positive significance for promoting the construction of related engineering.

The above embodiments are only illustrative of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention, and various modifications and improvements made by those skilled in the art to the technical solutions of the present invention should fall within the protection scope defined by the claims of the present invention without departing from the design spirit of the present invention.

Claims

1. The sludge curing agent is characterized by consisting of a cementing material and an additive;

2. The sludge curing agent according to claim 1, wherein the cementing material consists of 30% -50% of cement, 10% -40% of mineral powder, 10% -60% of fly ash and 10% -30% of water-washed fly ash, based on 100% of the total mass of the cementing material;

3. The sludge curative as claimed in claim 1, wherein the cement is a pozzolanic portland cement; the mineral powder is blast furnace slag powder.

4. The sludge curing agent according to claim 1, wherein the water-washed coal ash is coal ash produced by petrochemical plants, and is obtained by water washing, drying and grinding; the modulus of the alkali-activated agent is 1.2-1.6.

5. The sludge curing agent of claim 1, wherein the aluminous cement is a low alkalinity aluminous cement; the alkali content of the low-alkalinity sulphoaluminate cement is not higher than 0.6%; the desulfurized gypsum is dihydrate gypsum.

6. A method for preparing the sludge curing agent as claimed in any one of claims 1 to 5, comprising the steps of:

7. Use of a sludge solidification agent as claimed in any one of claims 1 to 5 in the solidification of dredging sludge.

8. Use of a sludge solidification agent according to any one of claims 1 to 5 for solidification of dredging sludge in the Hainan region.

9. Use according to claim 7 or 8, characterized in that the sludge solidifying agent represents 7-10% of the total mass of the dredging sludge.

10. Use according to claim 7 or 8, characterized in that the dredging sludge has a sludge content of 15-85% and a water content of 5-70%.