Marine silt solidifying agent modified by composite of finely ground slag and glass powder and application thereof

Abstract

The application belongs to the technical field of solid waste utilization and marine sludge solidification, and particularly discloses a kind of fine slag and glass powder composite modified marine sludge solidifying agent and application, the marine sludge solidifying agent component is marine cement 10-20 parts, low calcium fine slag 20-40 parts, pretreated waste glass powder 50-80 parts, potassium permanganate 1-2 parts and polypropylene fiber 0.1-1 part.The application utilizes the material characteristics of marine cement, low calcium fine slag and pretreated waste glass powder, and specifically solves the problem that the solidified soil of marine sludge is easy to crack and has low strength due to high water content and salt content.The solidifying agent obtained by the ratio has the characteristics of green economy, and the solidified marine sludge solidified soil has the characteristics of good crack resistance and high strength, and has a wide application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of solid waste utilization and marine sludge solidification, and specifically discloses a fine ground slag and glass powder composite modified marine sludge solidifying agent and application. BACKGROUND

[0002] The construction of coastal cities in the coastal new area is huge, and a large amount of silt soft soil foundation and silt filling land is very weak and not easy to use. At present, the relatively appropriate way to solve the marine sludge generated in the construction process of the coastal city in the coastal new area is to use it in solid geotechnical engineering, but it must be solidified and treated before being applied to engineering. However, the product after the solidification treatment of the marine sludge often has various problems such as low strength and poor durability. The marine sludge is difficult to treat because it has a high water content and contains a large amount of salt substances. Therefore, the solidifying agent commonly used for the solidification of lake and river sludge such as ordinary portland cement and lime cannot achieve good solidification effect, and the large-scale application of ordinary portland cement and other solidifying agents will greatly increase the cost.

[0003] The patent for invention with the number CN105152585 discloses a preparation method of fly ash-waste glass powder inorganic polymer sludge solidifying material, which adopts mixing fly ash and waste glass powder, then adding sodium hydroxide and sodium pyrosulfite composite activator for slow stirring for 1-2 hours, and finally fast stirring for 0.5 hours. The method has the following deficiencies: first, the formula depends on the composite activator with a pH of 12, and the solidification mechanism is alkali activation reaction, that is, the strong alkali is used to activate fly ash and waste glass powder to generate hydration products to solidify the sludge. Although this solidification method can significantly improve the polymerization speed of the inorganic polymer, the shrinkage caused by the alkali activation reaction is often greater than that of cement, which leads to the solidified soil being prone to shrinkage and cracking. The leakage of strong alkali after cracking may affect the ecological balance and cause harm to the surrounding plants, animals and even residents. Second, the solidifying agent has the disadvantage of inconvenient use. On the one hand, the stirring preparation process takes a long time, and it basically takes at least 1-2 hours. On the other hand, the liquid solidifying agent cannot be stored because the alkali activation reaction starts when the composite activator contacts other materials, and the solidifying agent will harden itself if it is not used in time, which further highlights the disadvantage of inconvenient use. Third, to solve the cracking problem, 5 parts of waste polypropylene carpet fibers are added, which are relatively scarce in engineering and have limited acquisition scenarios, limiting the application of the solidifying material. In view of the above problems, the application provides a fine ground slag and glass powder composite modified marine sludge solidifying agent, which does not directly use strong alkali such as sodium hydroxide, has a shorter preparation stirring time, and is a powder solidifying agent, having the advantages of environmental protection and convenient use.

[0004] To achieve the above object, the application provides the following technical solutions:

[0005] The fine slag and glass powder composite modified marine silt solidifying agent, the silt solidifying agent preparation material is: marine cement 10~20 parts, low calcium fine slag 20~40 parts, pretreated waste glass powder 50~80 parts, potassium permanganate 1~2 parts, polypropylene fiber 0.1~1 part.

[0006] Preferably, the low calcium fine slag is power plant furnace slag and fly ash of out of grade, after grinding, the specific surface area is greater than or equal to 400 m 2 ·kg -1 , and the chemical composition CaO is less than or equal to 10%.

[0007] Preferably, the pretreated waste glass powder is waste glass generated in the process of old building demolition and renovation, impurities are removed first, and then the waste glass is crushed into waste glass particles with a particle size of less than or equal to 5 mm, then the waste glass particles are ground for more than or equal to 20 minutes to obtain waste glass powder with an average particle size of less than or equal to 20 microns, the waste glass powder is then soaked in 1 mol of sodium hydroxide solution for 1~3 hours to increase the amorphous SiO2 content, then the waste glass powder is taken out from the sodium hydroxide solution and washed with clean water to ensure that the pH is less than or equal to 10, and finally the waste glass is dried to constant weight to obtain the final waste glass powder.

[0008] As an application of the fine slag and glass powder composite modified marine silt solidifying agent, the application also provides a marine silt solidified soil, that is, the fine slag and glass powder composite modified marine silt solidifying agent is added to marine silt at a proportion of 4%-10% of the mass of the silt, and after being fully stirred and uniformly mixed, the marine silt is left to stand for 24 hours to obtain the marine silt solidified soil.

[0009] Compared with the fly ash-waste glass powder inorganic polymer silt solidifying material in the prior art, the solidifying agent disclosed by the application has the following differences: first, the composition of the solidifying agent does not directly use a substance with extremely strong alkalinity, and there is no risk of strong alkali leakage damaging the environment, and in addition, the solidifying mechanism of the application is mainly cement hydration reaction and pozzolanic reaction, which has smaller shrinkage and is less likely to crack compared with alkali-activated reaction. Second, when the solidifying agent is prepared, only the various dry materials need to be fully mixed and stirred to obtain the powder solidifying agent, and the overall stirring time is about 5~10 minutes. The chemical reaction of the solidifying agent only occurs when it contacts with water, and the solidifying agent has the advantage of being very convenient to use. Third, the components of the solidifying agent are all common materials in the building material field, so the solidifying agent has the advantage of being easy to popularize. Finally, it is worth noting that although fly ash is a waste material, its commercial application has been very successful, and there is basically no situation of being piled up and unused. The low calcium fine slag used in the application is a waste slag that is piled up near a thermal power plant and is unused, which occupies a large amount of land resources. Therefore, the use of low calcium fine slag instead of fly ash in the application has higher environmental value and social significance.

[0010] The present application also has the following advantages:

[0011] 1) The main components of the marine silt solidifying agent of the present application are finely ground slag and waste glass powder. Therefore, it has the characteristics of low cost and large-scale disposal of waste, which avoids environmental pollution and occupation of limited land resources caused by waste, and has the advantages of low carbon and environmental protection, which is very consistent with the current requirement of sustainable development.

[0012] 2) The marine silt has high salt content. The solidified soil prepared by using ordinary Portland cement as the solidifying agent is prone to sulfate corrosion damage. That is, the sulfate ions in the marine silt react with some components of the cement to generate some insoluble salt substances such as ettringite and gypsum, which expand in volume, causing the solidified soil to crack and damage, and eventually deteriorating the strength. The present application uses marine cement, low-calcium finely ground slag and pretreated waste glass powder to improve the cracking problem of the marine silt solidified soil, and thus ensure the strength of the solidified soil. The C3A and C3S mineral contents of marine cement are lower than those of ordinary Portland cement. These minerals are the prerequisites for generating expansion products, so the use of marine cement can reduce the amount of expansion products generated; the use of low-calcium finely ground slag and glass powder can reduce the possibility of chemical reaction between alkaline substances in the cement and sulfates, thereby inhibiting the generation of expansion products.

[0013] 3) The marine silt has high water content, which easily leads to low strength of the marine silt solidified soil after being solidified by the solidifying agent. The present application improves the solidification effect by adding high specific surface area low-calcium finely ground slag and pretreated waste glass powder. The specific analysis is as follows: for low-calcium finely ground slag, its rich pore structure can promote the secondary hydration reaction of marine cement to generate more cementitious products, thereby improving the solidification effect of the silt; on the other hand, the large specific surface area of low-calcium finely ground slag can not only absorb a large amount of water in the silt to reduce the water content of the silt, but also provide a basis for complex physical and chemical reactions in the system, such as providing a site, promoting the nucleation and growth of hydration products in the pores, increasing the amount of hydration products, and further improving the strength of the silt solidification. For pretreated waste glass powder, first, the glass powder can act as aggregate and fill between the silt to enhance the strength of the silt solidified soil; second, the pretreated glass powder after ball milling has a certain activity and can generate hydration products through pozzolanic reaction, thereby improving the strength of the solidified soil to some extent; finally, the fine particles of the glass powder can also provide crystal nuclei for the hydration products of the low-calcium finely ground slag and cement, promote the crystallization process of the hydration products, and thus generate more hydration products to improve the solidification strength of the silt. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 A solidified soil formed by using the marine silt and the solidifying agent of the present application.

[0015] Figure 2 Comparison chart of marine silt before and after using the solidifying agent of the present application. DETAILED DESCRIPTION

[0016] In order to make the objectives, technical solutions and advantages of the present application clearer, the technical solutions in the present application are described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0017] Example 1: The marine silt solidifying agent is modified by composite of ground slag and glass powder. The preparation materials of the silt solidifying agent are as follows in terms of weight parts: marine cement 11 parts, low calcium ground slag 20 parts, pretreated waste glass powder 50 parts, potassium permanganate 1.0 part, polypropylene fiber 0.1 part.

[0018] Example 2: The marine silt solidifying agent is modified by composite of ground slag and glass powder. The preparation materials of the silt solidifying agent are as follows in terms of weight parts: marine cement 15 parts, low calcium ground slag 30 parts, pretreated waste glass powder 65 parts, potassium permanganate 1.5 parts, polypropylene fiber 0.5 part.

[0019] Example 3: The marine silt solidifying agent is modified by composite of ground slag and glass powder. The preparation materials of the silt solidifying agent are as follows in terms of weight parts: marine cement 14 parts, low calcium ground slag 36 parts, pretreated waste glass powder 57 parts, potassium permanganate 1.3 parts, polypropylene fiber 0.4 part. This embodiment is the best embodiment of the present application.

[0020] Example 4: The marine silt solidifying agent is modified by composite of ground slag and glass powder. The preparation materials of the silt solidifying agent are as follows in terms of weight parts: marine cement 20 parts, low calcium ground slag 40 parts, pretreated waste glass powder 80 parts, potassium permanganate 2 parts, polypropylene fiber 1 part.

[0021] Example 5: The marine silt solidifying agent is modified by composite of ground slag and glass powder. The preparation materials of the silt solidifying agent are as follows in terms of weight parts: marine cement 11 parts, low calcium ground slag 50 parts, pretreated waste glass powder 90 parts, potassium permanganate 1.3 parts, polypropylene fiber 0.4 part.

[0022] Comparative Example 1: The formula of this comparative example is the same as that of Example 3, except that the low calcium slag in this comparative example is not treated by ball milling, and the low calcium slag particles are relatively coarse.

[0023] Comparative Example 2: Fly ash 30 parts, waste glass powder 70 parts, water 40 parts, sodium hydroxide 3.2 parts, sodium pyrosulfite 1.28 parts, waste polypropylene carpet fiber 5 parts.

[0024] The mixture in Examples 1-5 and Comparative Examples 1-2 was used as a modified marine silt solidifying agent by compounding fine slag with glass powder. 0.4 kg of the marine silt solidifying agent in Examples 1-5 and Comparative Examples 1-2 was placed into 10 kg of marine silt, respectively. The moisture content and the sulfate ion concentration in water of the marine silt are shown in the table below. Then, the two were mixed and stirred to obtain a marine silt solidified soil. The unconfined compressive strength, the drying shrinkage value and the permeability coefficient of the solidified soil were tested after 7 days of curing. The test results are shown in the table below.

[0025]

[0026] As shown by the unconfined compressive strength, Examples 1-4 all showed good solidification effects on marine silt at different moisture contents and sulfate contents. The unconfined compressive strength of Examples 1-4 was all more than 3 MPa, and the solidification effect of Example 3 was the best. As shown by Examples 2 and 3, increasing the moisture content and the sulfate content caused a certain decrease in the unconfined compressive strength of the marine silt solidified soil. The decrease in Example 2 was 10.7%, and the decrease in Example 3 was 3.6%. It can be seen that Example 3 showed better solidification effects at different moisture contents and sulfate contents of marine silt, which indicated that the solidification effect was less affected by the change of marine silt and had stable solidification effects.

[0027] Examples 1-4 all showed good resistance to shrinkage deformation and low permeability coefficients at different moisture contents and sulfate contents. The drying shrinkage value of Examples 1-4 was all less than 0.030%, which indicated that the solidified soil had good resistance to cracking. The permeability coefficient of Examples 1-4 was all less than 1.00 x 10 -7 cm / s, which indicated that the solidified soil had high density. The high resistance to cracking and high density of the solidified soil explained the high unconfined compressive strength. Further, similar to the unconfined compressive strength, Example 3 showed the lowest drying shrinkage value and permeability coefficient.

[0028] As shown by Example 5, when part of the components of the marine silt solidifying agent was not within the scope of the present application, the unconfined compressive strength was significantly reduced, the drying shrinkage value and the permeability coefficient were significantly increased, and the solidification effect was significantly deteriorated.

[0029] As shown by Example 3 and Comparative Example 1, Comparative Example 1 used the optimal formula of Example 3, but if the low calcium slag was not subjected to ball milling treatment, the unconfined compressive strength of the solidified soil was significantly reduced, the drying shrinkage value and the permeability coefficient were significantly increased, compared with Example 3. This indicated that the ball milling treatment process of the low calcium slag was a key parameter affecting the solidification effect of the solidifying agent.

[0030] From the embodiment 3 and the comparative example 2, it can be seen that the unconfined compressive strength of the embodiment 3 is better than that of the comparative example 2, the drying shrinkage value and the permeability coefficient of the embodiment 3 are both less than those of the comparative example 2, and it is indicated that the solidified agent has a better effect on solidifying the silt than the solidified agent in the CN105152585 patent.

Claims

1. The application of a ground granulated blast furnace slag and glass powder composite modified marine silt curing agent in marine silt, characterized in that, The sludge solidifying agent is prepared from the following materials by weight parts: 10-20 parts of marine cement, 20-40 parts of low calcium ground slag, 50-80 parts of pretreated waste glass powder, 1-2 parts of potassium permanganate, and 0.1-1 parts of polypropylene fiber; The marine cement has a mineral composition with a C3A content of ≤5%; The low-calcium ground slag has a specific surface area ≥ 400 m 2 · kg -1 , chemical composition CaO ≤ 10%; The pretreated waste glass powder is obtained by removing impurities from waste glass, crushing, and grinding to obtain waste glass powder with an average particle size of ≤20 μm, and then soaking the waste glass powder in 1 mol of sodium hydroxide solution for 1-3 h, washing the waste glass with clean water to ensure that the pH is ≤10, and finally drying the waste glass to a constant weight to obtain the final waste glass powder; The application is characterized in that the marine sludge is mixed with a solidifying agent in an amount of 4%-10% of the mass of the sludge, and then stirred uniformly and left to stand for 24 h to obtain marine sludge solidified soil.

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