Anti-salting-out high-strength salt-containing dredging land polymer and preparation method thereof

Abstract

The invention provides a salting-out-resistant high-strength salt-containing dredging land polymer and a preparation method thereof. The salting-out-resistant high-strength salt-containing dredging land polymer is prepared from a cementing material and an alkali activator, the cementing material comprises salt-containing dredged soil, fly ash and granulated blast furnace slag, and the alkali activator comprises a mixed solution of sodium silicate and sodium hydroxide. According to the method, a strong alkaline environment is utilized, silicon-oxygen bonds and aluminum-oxygen bonds in the cementing material are broken and recombined to form a stable silicon-oxygen tetrahedral structure, and a three-dimensional mesh gel structure is finally formed, so that ion migration is reduced, the salting-out resistance of a salt-containing dredged soil recycling product is enhanced, and the salting-out resistance of the salt-containing dredged soil recycling product is improved. The desalting steps such as leaching in the salt-containing dredged soil resource utilization process can be omitted, the salt-containing dredged soil resource cost is reduced, and meanwhile high compressive strength is kept.

Description

Technical Field

[0001] The invention relates to the technical field of dredged soil disposal and utilization, and in particular to a high-strength salt-containing dredged soil polymer that is resistant to salting out and a preparation method thereof. Background Art

[0002] In coastal engineering, coastal engineering construction and maintenance dredging of ports and waterways usually produces a large amount of dredged materials, the main component of which is saline dredged soil, which is mostly natural soil material deposited on the seabed in estuary areas and contains rich clay minerals and secondary minerals. Affected by the strict control of land reclamation policies, the amount of saline dredged soil dumped into the ocean in my country has increased year by year, and the existing dumping areas cannot meet the growing demand for dumping. On the one hand, national construction and coastal economic development urgently need more effective and beneficial methods of disposing of saline dredged soil; on the other hand, the expansion of dumping areas or offshore dumping brings about problems such as ecological environment deterioration, topographic changes or economic cost constraints, and it is urgent to seek ways to utilize saline resources.

[0003] Dredged soil is usually solidified with cement for resource utilization. For example, CN 105130289 A discloses a method for preparing unburned bricks using dredged mud aggregates, wherein dredged mud ceramsite is used as dredged mud aggregates, and cement, quicklime, gypsum and fly ash are used as cementitious materials. The finished dredged mud unburned bricks are obtained through batching, water addition and stirring, aging of the mixture, pressing and molding by a brick press, and product maintenance.

[0004] However, the salt content in saline dredged soil is high, Na + , Cl - It has high mobility and will precipitate from the surface of cement solidification products, reducing the strength of cement solidification products. If cement is used to solidify saline dredged soil, the saline dredged soil needs to be desalted by leaching, which makes the resource recovery process complicated and increases costs. Studies have shown that the main components of geopolymer cementitious materials are sodium aluminosilicate hydrate (NASH) and calcium aluminosilicate hydrate (CASH), which have high physical strength and a stable silicon-oxygen tetrahedral structure and a three-dimensional network gel structure. Therefore, geopolymer cementitious materials can be used to solidify saline dredged soil, and the stable structure in the geopolymer can be used to reduce Na + , Cl - The migration of salt-containing dredged soil is then obtained, thereby obtaining a high-strength salt precipitation-resistant saline dredged soil polymer material, thereby realizing the resource utilization of the saline dredged soil. At present, there is no relevant technology for utilizing saline dredged soil resources using geopolymer cementitious materials. Summary of the invention

[0005] In view of the defects of salt precipitation and strength reduction faced by the existing resource utilization of saline dredged soil, the present invention provides a high-strength saline dredged soil polymer resistant to salt precipitation and a preparation method thereof, wherein the high-strength saline dredged soil polymer resistant to salt precipitation is prepared by using a gelling material and an alkali activator; the gelling material includes saline dredged soil, fly ash and granulated blast furnace slag, and the alkali activator includes a mixed solution of sodium silicate and sodium hydroxide. The present invention utilizes the silicon-oxygen tetrahedral structure and the three-dimensional mesh gelling structure of the geopolymer to weaken the ion migration ability, thereby reducing the occurrence of salt precipitation, while maintaining a high compressive strength.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] One of the purposes of the present invention is to provide a high-strength salt-containing dredged soil polymer that is resistant to salting-out. The high-strength salt-containing dredged soil polymer that is resistant to salting-out is prepared by using a cementitious material and an alkali activator; the cementitious material includes salt-containing dredged soil, fly ash and granulated blast furnace slag, and the alkali activator includes a mixed solution of sodium silicate and sodium hydroxide.

[0008] The present invention utilizes a strong alkaline environment to break and reorganize the silicon-oxygen bonds and aluminum-oxygen bonds in the gelling material to form a stable silicon-oxygen tetrahedral structure, and finally form a three-dimensional network gel structure, thereby reducing ion migration and enhancing the salt precipitation resistance of the saline dredged soil resource product. The desalination steps such as leaching in the process of saline dredged soil resource utilization can be eliminated, the cost of saline dredged soil resource utilization can be reduced, and a relatively high compressive strength can be maintained.

[0009] As a preferred technical solution of the present invention, the salt content of the saline dredged soil is 0.1-8wt%, for example, 0.1wt%, 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt% or 8wt%.

[0010] As a preferred technical solution of the present invention, the salt-containing dredged soil in the cementitious material accounts for 40-60wt%, for example, 40wt%, 43wt%, 45wt%, 48wt%, 50wt%, 52wt%, 55wt%, 57wt% or 60wt%, etc., and the rest is a mixture of fly ash and granulated blast furnace slag; the fly ash in the mixture of fly ash and granulated blast furnace slag accounts for 65-75wt%, for example, 65wt%, 67wt%, 70wt%, 71wt%, 73wt% or 75wt%, etc.

[0011] As a preferred technical solution of the present invention, the Na2O content in the alkali activator is 4-8wt% of the gelling material, for example, 4wt%, 4.5wt%, 5wt%, 5.5wt%, 6wt%, 6.5wt%, 7wt%, 7.5wt% or 8wt%, etc., and the modulus of the alkali activator is 1.0-1.8, for example, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7 or 1.8, etc.

[0012] As a preferred technical solution of the present invention, the water required for the salting-out resistant high-strength salt-containing dredged land polymer is provided by an alkali activator, and the mass ratio of water to cementitious material in the alkali activator is 0.3-0.5, such as 0.3, 0.35, 0.4, 0.45 or 0.5.

[0013] The second object of the present invention is to provide a method for preparing the anti-salting out high-strength salt-containing dredged land polymer according to the first object, the preparation method comprising the following steps:

[0014] (1) According to a target ratio, the pretreated saline dredged soil is mixed with fly ash and granulated blast furnace slag to obtain a cementitious material, and water, sodium silicate and sodium hydroxide are mixed to obtain an alkali activator;

[0015] (2) adding an alkali activator to the gelling material and stirring the mixture to obtain a salt-containing dredged land polymer slurry;

[0016] (3) pouring the salt-containing dredged land polymer slurry into a mold and curing it to obtain a salting-out resistant high-strength salt-containing dredged land polymer.

[0017] As a preferred technical solution of the present invention, the pretreatment includes: drying, crushing, screening and ball milling the saline dredged soil in sequence to reduce the particle size to less than 110 μm.

[0018] Preferably, the particle size of the fly ash is less than 40 μm, and the particle size of the granulated blast furnace slag is less than 25 μm.

[0019] As a preferred technical solution of the present invention, the stirring time of step (2) is 1 to 2 minutes, for example, 1 minute, 1.1 minutes, 1.3 minutes, 1.5 minutes, 1.7 minutes, 1.8 minutes or 2 minutes.

[0020] As a preferred technical solution of the present invention, the curing includes constant temperature curing with mold and natural curing after demolding.

[0021] As a preferred technical solution of the present invention, the temperature of the constant temperature curing with mold is 50-60°C, for example, 50°C, 51°C, 52°C, 54°C, 55°C, 56°C, 58°C or 60°C, and the time is 20-30h, for example, 20h, 21h, 23h, 25h, 26h, 28h or 30h, and the time of the demolding natural curing is 6-8d, for example, 6d, 6.5d, 7d, 7.5d or 8d.

[0022] Compared with the prior art solutions, the present invention has at least the following beneficial effects:

[0023] The present invention uses a mixture of saline dredged soil, fly ash and granulated blast furnace slag as a cementitious material, and utilizes a strong alkaline environment to break and reorganize the silicon-oxygen bonds and aluminum-oxygen bonds in the cementitious material to form a stable silicon-oxygen tetrahedral structure, and finally form a three-dimensional network gel structure, thereby reducing ion migration and enhancing the salt precipitation resistance of the saline dredged soil resource product. The desalination steps such as leaching in the process of saline dredged soil resource utilization can be eliminated, reducing the cost of saline dredged soil resource utilization, while maintaining a relatively high compressive strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a scanning electron microscope image of the salting-out resistant high-strength salt-containing dredged land polymer prepared in Example 1 of the present invention.

[0025] Figure 2 This is a performance comparison chart of the unfired bricks described in Example 1 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is further described below with reference to the accompanying drawings and through specific implementation methods.

[0027] To better illustrate the present invention and facilitate understanding of the technical solution of the present invention, typical but non-limiting embodiments of the present invention are as follows:

[0028] Example 1

[0029] This embodiment provides a method for preparing a salting-out resistant high-strength salt-containing dredged land polymer for preparing unburned bricks, the preparation method comprising the following steps:

[0030] (1) drying, crushing, screening, and ball milling the saline dredged soil in sequence, and crushing the saline dredged soil into saline dredged soil with a particle size of less than 110 μm by the ball mill, wherein the saline dredged soil has a salt content of 4 wt%; preparing a mixture of fly ash and granulated blast furnace slag in a mass ratio of 7:3, wherein the particle size of the fly ash is less than 40 μm, and the particle size of the granulated blast furnace slag is less than 25 μm; mixing the mixture of the saline dredged soil, the fly ash, and the granulated blast furnace slag in a mass ratio of 1:1 to obtain a cementitious material;

[0031] The alkali activator is prepared by mixing water, sodium silicate and sodium hydroxide, wherein the content of Na2O in the alkali activator is controlled to be 5wt% of the cementitious material, the modulus of the alkali activator is 1.5, and the mass ratio of water in the alkali activator to the cementitious material is 0.3, so as to provide the water required in the preparation process of the high-strength salt-containing dredged land polymer with resistance to salting out; (2) the alkali activator is added to the cementitious material, and the mixture is rapidly stirred for 2 minutes by a stirrer, and the speed of the stirrer is set to 500 r / min, so as to obtain a salt-containing dredged land polymer slurry;

[0032] (3) The salt-containing dredged land polymer slurry is poured into an unfired brick mold, placed in a constant temperature box, and maintained at a constant temperature of 55°C for 24 hours to allow the slurry to take shape. The demolded blank is placed under natural conditions for curing for 7 days to obtain a salt-resistant, high-strength salt-containing dredged land polymer unfired brick.

[0033] The prepared anti-salting high-strength salt-containing dredged land polymer unfired bricks were tested by scanning electron microscope with a magnification of 1000 times. Figure 1 A scanning electron microscope image is shown, showing that a dense geopolymer structure is formed.

[0034] Example 2

[0035] This embodiment provides a method for preparing a salting-out resistant high-strength salt-containing dredged land polymer for preparing unburned bricks, the preparation method comprising the following steps:

[0036] (1) drying, crushing, screening and ball milling the saline dredged soil in sequence, and crushing the saline dredged soil into saline dredged soil with a particle size of less than 110 μm by the ball mill, wherein the saline dredged soil has a salt content of 8 wt%; preparing a mixture of fly ash and granulated blast furnace slag in a mass ratio of 7:3, wherein the particle size of the fly ash is less than 40 μm, and the particle size of the granulated blast furnace slag is less than 25 μm; mixing the mixture of the saline dredged soil, the fly ash and the granulated blast furnace slag in a mass ratio of 1:1 to obtain a cementitious material;

[0037] Mixing water, sodium silicate and sodium hydroxide to prepare an alkali activator, controlling the Na2O content in the alkali activator to be 5wt% of the cementitious material, the modulus of the alkali activator to be 1.5, and the mass ratio of water in the alkali activator to the cementitious material to be 0.3, so as to provide the water required in the preparation process of the high-strength salt-containing dredged land polymer with resistance to salting out;

[0038] (2) adding an alkali activator to the gelling material, and rapidly stirring the material with a stirrer for 2 minutes, with the stirrer speed set at 500 r / min, to obtain a salt-containing dredged land polymer slurry;

[0039] (3) The salt-containing dredged land polymer slurry is poured into an unfired brick mold, placed in a constant temperature box, and maintained at a constant temperature of 55°C for 30 hours to allow the slurry to take shape. The demolded blank is placed under natural conditions for curing for 7 days to obtain a salt-resistant, high-strength salt-containing dredged land polymer unfired brick.

[0040] Example 3

[0041] This embodiment provides a method for preparing a salting-out resistant high-strength salt-containing dredged land polymer for preparing unburned bricks, the preparation method comprising the following steps:

[0042] (1) drying, crushing, screening, and ball milling the saline dredged soil in sequence, and crushing the saline dredged soil into saline dredged soil with a particle size of less than 110 μm by the ball mill, wherein the saline dredged soil has a salt content of 4 wt%; preparing a mixture of fly ash and granulated blast furnace slag in a mass ratio of 7:3, wherein the particle size of the fly ash is less than 40 μm, and the particle size of the granulated blast furnace slag is less than 25 μm; mixing the mixture of the saline dredged soil, the fly ash, and the granulated blast furnace slag in a mass ratio of 1:1 to obtain a cementitious material;

[0043] The alkali activator is prepared by mixing water, sodium silicate and sodium hydroxide, wherein the content of Na2O in the alkali activator is controlled to be 8wt% of the cementitious material, the modulus of the alkali activator is 1.5, and the mass ratio of water in the alkali activator to the cementitious material is 0.5, so as to provide the water required in the preparation process of the high-strength salt-containing dredged land polymer with resistance to salting out; (2) the alkali activator is added to the cementitious material, and the mixture is rapidly stirred for 2 minutes by a stirrer, and the speed of the stirrer is set to 500 r / min to obtain a salt-containing dredged land polymer slurry;

[0044] (3) The salt-containing dredged land polymer slurry is poured into an unfired brick mold, placed in a constant temperature box, and maintained at a constant temperature of 55°C for 20 hours to allow the slurry to take shape. The demolded blank is placed under natural conditions for curing for 7 days to obtain a salt-resistant, high-strength salt-containing dredged land polymer unfired brick.

[0045] Example 4

[0046] This embodiment provides a method for preparing a high-strength salt-containing dredged soil polymer that is resistant to salting-out. Compared with Example 1, the only difference is that a mixture of salt-containing dredged soil, fly ash and granulated blast furnace slag is mixed in a mass ratio of 3:7 to obtain a cementitious material, that is, the proportion of salt-containing dredged soil in the cementitious material is reduced to 30wt%.

[0047] Example 5

[0048] This embodiment provides a method for preparing a high-strength salt-containing dredged soil polymer that is resistant to salting-out. Compared with Example 1, the only difference is that a mixture of salt-containing dredged soil, fly ash and granulated blast furnace slag is mixed in a mass ratio of 7:3 to obtain a cementitious material, that is, the proportion of salt-containing dredged soil in the cementitious material is increased to 70wt%.

[0049] Example 6

[0050] This embodiment provides a method for preparing a high-strength salt-containing dredged land polymer that is resistant to salting-out. Compared with Example 1, the only difference is that a mixture of fly ash and granulated blast furnace slag with a mass ratio of 6:4 is prepared, that is, the proportion of fly ash in the mixture of fly ash and granulated blast furnace slag is reduced to 60wt%.

[0051] Example 7

[0052] This embodiment provides a method for preparing a high-strength salt-containing dredged land polymer that is resistant to salting-out. Compared with Example 1, the only difference is that a mixture of fly ash and granulated blast furnace slag with a mass ratio of 8:2 is prepared, that is, the proportion of fly ash in the mixture of fly ash and granulated blast furnace slag is increased to 80wt%.

[0053] Comparative Example 1

[0054] This comparative example provides a method for preparing unburned bricks using salt-containing dredged soil, the method comprising the following steps:

[0055] (1) drying, crushing, screening, and ball milling the saline dredged soil in sequence, and grinding the saline dredged soil into saline dredged soil with a particle size of less than 110 μm by a ball mill, wherein the saline dredged soil has a salt content of 4 wt %; mixing the saline dredged soil with cement in a mass ratio of 1:1 to obtain a cementitious material;

[0056] Mixing water, sodium silicate and sodium hydroxide to prepare an alkali activator, controlling the Na2O content in the alkali activator to be 5wt% of the gelling material, the modulus of the alkali activator to be 1.5, and the mass ratio of water in the alkali activator to the gelling material to be 0.3, so as to provide the water required in the preparation process;

[0057] (2) adding an alkali activator to the gelling material, and rapidly stirring the material with a stirrer for 2 minutes, with the stirrer speed set at 500 r / min, to obtain a salt-containing dredged land polymer slurry;

[0058] (3) The salt-containing dredged soil polymer slurry is poured into an unfired brick mold, placed in a constant temperature box, and maintained at a constant temperature of 55° C. for 24 hours to allow the slurry to be shaped. The demolded blank is placed under natural conditions for curing for 7 days to obtain a salt-containing dredged soil unfired brick.

[0059] The unfired bricks prepared by the above-mentioned embodiments and comparative examples were subjected to compressive strength test and 7-day bottom immersion salting-out test, respectively. The method of the 7-day bottom immersion salting-out test is as follows: In an open environment with an ambient temperature of 25°C and a relative humidity of 65%, the bottom of the unfired brick sample with a cutting size of 2.5cm×2.5cm×2.5cm was immersed in 2 mm of water for 7 days. After the immersion test was completed, the precipitate sample was collected from the surface of the sample unfired brick, and then dried and weighed to obtain the precipitate mass. The specific test results are summarized in Table 1. Figure 2 A performance comparison chart of the unfired bricks described in Example 1 and Comparative Example 1 is shown.

[0060] Table 1

[0061]

[0062]

[0063] From Table 1, we can see the following points:

[0064] (1) The present invention uses a mixture of saline dredged soil, fly ash and granulated blast furnace slag as a cementitious material, and utilizes a strong alkaline environment to break and reorganize the silicon-oxygen bonds and aluminum-oxygen bonds in the cementitious material to form a stable silicon-oxygen tetrahedral structure, and finally form a three-dimensional network gel structure, thereby reducing ion migration and enhancing the salt precipitation resistance of the saline dredged soil resource product. The desalination steps such as leaching in the process of saline dredged soil resource utilization can be eliminated, reducing the cost of saline dredged soil resource utilization, while maintaining a high compressive strength;

[0065] (2) Comparing Example 1 with Example 4 and Example 5, Example 4 reduces the proportion of salt-containing dredged soil in the cementitious material to 30wt%. Although it can still maintain a high compressive strength and anti-salting ability, the resource utilization degree of the salt-containing dredged soil is reduced, and the economic efficiency is reduced. Example 5 increases the proportion of salt-containing dredged soil in the cementitious material to 70wt%, resulting in a decrease in both compressive strength and anti-salting ability. Therefore, the addition amount of salt-containing dredged soil should not be too high;

[0066] (3) Example 1 is compared with Example 6 and Example 7. In Example 6, the proportion of fly ash in the mixture of fly ash and granulated blast furnace slag is reduced to 60wt%, resulting in excessive calcium content from the granulated blast furnace slag, forming inactive and unreacted components, and inhibiting the formation of geopolymer gel. In Example 7, the proportion of fly ash in the mixture of fly ash and granulated blast furnace slag is increased to 80wt%, resulting in a decrease in the silicon / aluminum ratio in the cementitious material, so that the density of the formed geopolymer is reduced.

[0067] The present invention illustrates the detailed structural features of the present invention through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the components selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0068] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0069] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0070] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A high-strength salt-containing dredged land polymer with resistance to salting out, characterized in that: The anti-salting out high-strength saline dredged soil polymer is prepared by using a cementitious material and an alkali activator; the cementitious material comprises saline dredged soil, fly ash and granulated blast furnace slag, and the alkali activator comprises a mixed solution of sodium silicate and sodium hydroxide.

2. The anti-salting out high-strength salt-containing dredged land polymer according to claim 1, characterized in that: The salt content of the saline dredged soil is 0.1-8 wt %.

3. The anti-salting out high-strength salt-containing dredged land polymer according to claim 1, characterized in that: The salt-containing dredged soil accounts for 40-60wt% of the cementitious material, and the rest is a mixture of fly ash and granulated blast furnace slag; the fly ash accounts for 65-75wt% of the mixture of fly ash and granulated blast furnace slag.

4. The anti-salting out high-strength salt-containing dredged land polymer according to claim 1, characterized in that: The content of Na2O in the alkali activator is 4-8wt% of the gelling material, and the modulus of the alkali activator is 1.0-1.

8.

5. The anti-salting out high-strength salt-containing dredged land polymer according to claim 1, characterized in that: The water required for the salting-out resistant high-strength salt-containing dredged land polymer is provided by an alkali activator, and the mass ratio of water to gelling material in the alkali activator is 0.3-0.

5.

6. A method for preparing the salting-out resistant high-strength salt-containing dredged land polymer according to any one of claims 1 to 5, characterized in that: The preparation method comprises the following steps: (1) According to a target ratio, the pretreated saline dredged soil is mixed with fly ash and granulated blast furnace slag to obtain a cementitious material, and water, sodium silicate and sodium hydroxide are mixed to obtain an alkali activator; (2) adding an alkali activator to the gelling material and stirring the mixture to obtain a salt-containing dredged land polymer slurry; (3) pouring the salt-containing dredged land polymer slurry into a mold and curing it to obtain a salting-out resistant high-strength salt-containing dredged land polymer.

7. The preparation method according to claim 6, characterized in that: The pretreatment comprises: drying, crushing, screening and ball milling the salt-containing dredged soil in sequence to make the particle size below 110 μm; Preferably, the particle size of the fly ash is less than 40 μm, and the particle size of the granulated blast furnace slag is less than 25 μm.

8. The preparation method according to claim 6, characterized in that: The stirring time of step (2) is 1 to 2 minutes.

9. The preparation method according to claim 6, characterized in that: The curing includes constant temperature curing with mold and natural curing after demoulding.

10. The preparation method according to claim 9, characterized in that: The temperature of the constant temperature curing with mold is 50-60° C., and the time is 20-30 hours; the time of the demoulding natural curing is 6-8 days.

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