Regenerated micro-powder geopolymer and preparation method thereof

Abstract

The invention provides a regenerated micro-powder geopolymer which comprises the following components in parts by mass: 50-60 parts of ground regenerated micro-powder, 10-20 parts of low-temperature calcined regenerated micro-powder, 10-20 parts of slag powder, 10-20 parts of nickel slag powder, 7-10 parts of water glass, 5-10 parts of polymeric aluminum chloride and 30-40 parts of water. The invention also provides a preparation method of the regenerated micro-powder geopolymer. According to the regenerated micro-powder geopolymer and the preparation method thereof provided by the invention, the regenerated micro-powder geopolymer is high in strength, low in dry shrinkage rate and not easy to crack.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials, and particularly relates to a recycled fine powder geopolymer and a preparation method thereof. Background Art

[0002] Among untreated construction waste, there are more than 20 harmful substances. If randomly piled up or landfilled, it will not only damage vegetation, change the soil structure, affect soil microbial activities, but also pollute water bodies, soil and the atmosphere, and it is difficult to be naturally decomposed. To effectively address this challenge and promote the sustainable development of the economic society, in recent years, the Chinese government has provided strong financial, policy and technical support for relevant research, disposal and utilization work. Relevant departments have also actively taken actions and launched the compilation work of standards such as "Terms for Comprehensive Utilization of Construction Waste Resources" and "Recycled Aggregates for Blocks and Bricks".

[0003] However, current research mainly focuses on the large-scale resource utilization of recycled aggregates, and there is still a lack of clear recycling solutions for the fine powders generated in the air separation process of the construction waste crushing process. This is mainly because the micro-powders generated during the crushing and sorting of waste concrete and brick-concrete buildings have low activity and high water absorption, and physical-chemical methods need to be used for solubilization activation. But even after treatment, these micro-powders may still have an adverse impact on the strength development of concrete after replacing part of the cement. Therefore, at present, except for a small amount used for subgrade treatment, most of the recycled fine powders of construction waste have not been effectively utilized. This not only occupies precious land resources, but also may cause dust pollution. After being discharged into the water system, it will cause river siltation, and the fine particles may also pose a serious threat to human and biological health. Therefore, solving the technical bottleneck of low activity and low utilization rate of construction waste micro-powders and realizing their high-value-added and large-scale resource utilization have great social significance and economic benefits. However, existing research shows that the geopolymer cementitious materials prepared from recycled fine powders have the problem of large shrinkage, which to a certain extent hinders their popularization in practical applications.

[0004] Therefore, there is an urgent need for a recycled fine powder geopolymer with high strength, low dry shrinkage rate and not easy to crack to comprehensively improve the level of construction waste resource utilization in China. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a recycled fine powder geopolymer with high strength, low dry shrinkage rate and not easy to crack and a preparation method thereof.

[0006] To solve the above technical problems, the present invention provides a recycled fine powder geopolymers, by mass, comprising 50 - 60 parts of ground recycled fine powder, 10 - 20 parts of low-temperature calcined recycled fine powder, 10 - 20 parts of slag powder, 10 - 20 parts of nickel slag powder, 7 - 10 parts of water glass, 5 - 10 parts of polymeric aluminum chloride, and 30 - 40 parts of water.

[0007] Further, the ground recycled fine powder is obtained by grinding the fine powder collected in the air separation process of the waste concrete crushing process to a residue on a 80μm square hole sieve of 1.8%.

[0008] Further, the low-temperature calcined recycled fine powder is obtained by low-temperature calcining the ground recycled fine powder at a temperature of 650°C - 850°C.

[0009] Further, the water glass is a water glass solution with a modulus of 1.4 - 1.8.

[0010] Further, the polymeric aluminum chloride is a chemical reagent with an alumina content of ≥29%.

[0011] Further, the slag powder is granulated blast furnace slag powder that meets the requirements of the activity index and fluidity ratio of S95 grade specified in GB / T 18046 - 2017 "Granulated Blast Furnace Slag Powder for Cement, Mortar and Concrete".

[0012] Further, the nickel slag powder meets the requirements of the activity index and fluidity ratio of G90 grade specified in JC / T 2503 - 2018 "Nickel Ferrous Slag Powder for Cement and Concrete".

[0013] The present invention also provides a preparation method of a recycled fine powder geopolymers, comprising the following steps:

[0014] Grind the fine powder collected in the air separation process of the waste concrete crushing process to a residue on an 80μm square hole sieve of ≤1.8% to obtain ground recycled fine powder;

[0015] Place the ground recycled fine powder in a muffle furnace and calcine it at 650°C - 850°C for 20min - 40min to obtain low-temperature calcined recycled fine powder;

[0016] By mass, mix 50 - 60 parts of ground recycled fine powder, 10 - 20 parts of low-temperature calcined recycled fine powder, 10 - 20 parts of slag powder, 10 - 20 parts of nickel slag powder, 7 - 10 parts of water glass, 5 - 10 parts of polymeric aluminum chloride, and 30 - 40 parts of water to prepare a slurry;

[0017] Pour the slurry into a mold and cure it in a curing box until the specified age to obtain a geopolymer cementitious material.

[0018] A recycled fine powder geopolymers and its preparation method provided by the present invention uses the fine powder collected in the air separation process of the waste concrete crushing process as the main raw material to prepare recycled fine powder geopolymers, which can realize the large-scale resource utilization of recycled fine powder, reduce land occupation, save natural resources and improve the environment.

[0019] Moreover, a recycled fine powder geopolymers and its preparation method provided by the present invention uses the ground recycled fine powder obtained by grinding and screening the fine powder collected in the air separation process of the waste concrete crushing process as the main raw material, supplemented by the ground recycled fine powder obtained by low-temperature calcination and two solid wastes of granulated blast furnace slag powder and nickel slag powder. The prepared recycled fine powder geopolymers not only have the advantages of good fluidity and high strength, but also have the advantages of good durability and low dry shrinkage rate.

[0020] At the same time, a preparation method of recycled fine powder geopolymers provided by the present invention does not require large-scale equipment and complex processes, does not require cement clinker, nor harsh preparation conditions such as high-temperature calcination. It not only has a simple preparation method, high utilization rate of recycled fine powder and low preparation cost, but also the prepared recycled fine powder geopolymers have the advantages of good fluidity, high strength, good durability and low dry shrinkage rate. Brief Description of the Drawings

[0021] Figure 1 It is a flow chart of a preparation method of recycled fine powder geopolymers provided by an embodiment of the present invention. Detailed Embodiments

[0022] A recycled fine powder geopolymers provided by an embodiment of the present invention, in parts by mass, includes 50-60 parts of ground recycled fine powder, 10-20 parts of low-temperature calcined recycled fine powder, 10-20 parts of slag powder, 10-20 parts of nickel slag powder, 7-10 parts of sodium silicate, 5-10 parts of polymeric aluminum chloride, and 30-40 parts of water.

[0023] Among them, the ground recycled fine powder is obtained by grinding the fine powder collected in the air separation process of the waste concrete crushing process until the residue on a 80μm square hole sieve is 1.8%. The components of the ground recycled fine powder are usually SiO 2 , CaCO 3 , Ca(OH) 2 , hydrated calcium silicate and calcium aluminate, etc. And the surface pores of the ground recycled fine powder are more, the water absorption rate is higher, and it has no self-cementing hydration ability. In the present invention, the fine powder collected in the air separation process of the waste concrete crushing process is ground until the residue on a 80μm square hole sieve is 1.8% to obtain the ground recycled fine powder, and the ground recycled fine powder is mechanically activated (i.e., ground) treatment.

[0024] Among them, the low-temperature calcined recycled fine powder is obtained by low-temperature calcining the ground recycled fine powder at a temperature of 650°C to 850°C.

[0025] Among them, the sodium silicate is a sodium silicate solution with a modulus of 1.4 to 1.8.

[0026] Among them, the polyaluminum chloride is a chemical reagent with an alumina content of ≥29%.

[0027] Among them, the slag powder is granulated blast furnace slag powder that meets the requirements of the activity index and fluidity ratio of S95 grade specified in GB / T 18046-2017 "Granulated Blast Furnace Slag Powder for Cement, Mortar and Concrete". Granulated blast furnace slag powder is a powder material obtained by grinding water-quenched granulated blast furnace slag to a certain fineness. Its particle surface is relatively rough, and the active SiO 2 content is relatively high, and it has hydraulicity.

[0028] Among them, the nickel slag powder meets the requirements of the activity index and fluidity ratio of G90 grade specified in JC / T 2503-2018 "Nickel Iron Slag Powder for Cement and Concrete". Nickel slag powder is a powder material obtained by grinding the waste slag generated in the steelmaking process to a certain fineness, and the particle surface is relatively rough. Among them, the chemical composition of the steelmaking waste slag mainly includes MgO, SiO 2 , Al 2 O 3 , Fe 2 O 3 , and its composition is similar to that of cement clinker. Therefore, a recycled fine powder geopolymer provided by the present invention does not need to add cement during use.

[0029] For the recycled fine powder geopolymer provided by the present invention, the ground recycled fine powder in its composition destroys the surface layer of the original C-S-H gel structure in the recycled fine powder due to the mechanical activation effect, changes the particle size distribution of the recycled fine powder and the polymerization degree and mode of the Si-O bond and Al-O bond therein, further increases the specific surface area of the recycled fine powder, and improves the activity of the recycled fine powder. Moreover, the ground recycled fine powder has certain alkali activity and can react with sodium silicate through alkali activation reaction to make the recycled fine powder geopolymer form a certain strength.

[0030] Furthermore, for the recycled fine powder geopolymer provided by the present invention, slag powder and nickel slag powder are added. The siliceous and aluminous minerals in the slag powder and nickel slag powder can accelerate and strengthen the reaction in an alkaline environment, and can significantly improve the strength of the recycled fine powder geopolymer.

[0031] At the same time, for the recycled fine powder geopolymer provided by the present invention, polymeric aluminum chloride is used as a coagulant, and the polymeric aluminum chloride can complexly activate the ground recycled fine powder and accelerate its dissolution-precipitation process.

[0032] Therefore, for the recycled fine powder geopolymers provided by the present invention, under the action of polyaluminum chloride and sodium silicate, the original C-S-H gel of cement hydration products and the Si-O bonds and Al-O bonds of calcium aluminate hydrate in the mechanically activated ground recycled fine powder, low-temperature calcined recycled fine powder, granulated blast furnace slag powder and nickel slag powder will undergo structural fracture and recombination to generate new cementitious products. As the age increases, the structure of the solidified body becomes denser and the strength gradually increases.

[0033] However, for the recycled fine powder geopolymers provided by the present invention, there are problems of relatively large shrinkage in the reactions between raw materials. Therefore, the present invention also adds low-temperature calcined recycled fine powder with shrinkage-reducing properties to the recycled fine powder geopolymers. The main components of the low-temperature calcined recycled fine powder are calcium oxide and calcium silicate, etc. Calcium oxide and calcium silicate have a certain micro-expansion effect during the hydration process, and the low-temperature calcined recycled fine powder generates β-C 2 S and C 12 A 7 which has a good shrinkage-reducing effect.

[0034] Therefore, adding low-temperature calcined recycled fine powder with shrinkage-reducing properties to the recycled fine powder geopolymers of the present invention can significantly reduce the shrinkage of the recycled fine powder geopolymers, greatly reduce the dry shrinkage rate of the recycled fine powder geopolymers, and reduce the risk of cracking of the recycled fine powder geopolymer cementitious materials during use.

[0035] See Figure 1 , a preparation method of a recycled fine powder geopolymer provided by an embodiment of the present invention includes the following steps:

[0036] Step 1) Grind the fine powder collected in the air separation process during the waste concrete crushing process to a residue on a 80μm square hole sieve of ≤1.8% to obtain ground recycled fine powder.

[0037] Step 2) Place the ground recycled fine powder in a muffle furnace and calcine it at 650°C to 850°C for 20 min to 40 min to obtain low-temperature calcined recycled fine powder.

[0038] Step 3) By mass, mix 50 - 60 parts of ground recycled fine powder, 10 - 20 parts of low-temperature calcined recycled fine powder, 10 - 20 parts of slag powder, 10 - 20 parts of nickel slag powder, 7 - 10 parts of sodium silicate, 5 - 10 parts of polymeric aluminum chloride and 30 - 40 parts of water to prepare a slurry;

[0039] Step 4) Pour the slurry into a mold and cure it in a curing box until the specified age to obtain a geopolymer cementitious material.

[0040] The following specifically describes a recycled fine powder geopolymer and its preparation method provided by the present invention through examples and comparative examples.

[0041] Example 1

[0042] A low-shrinkage geopolymer cementitious material (by mass) contains the following components:

[0043]

[0044] Mix 50 parts of recycled fine powder (obtained by grinding the fine powder collected in the air separation process of the waste concrete crushing process to a residue on a 80μm square hole sieve of 1.8%), 20 parts of low-temperature calcined recycled fine powder, 15 parts of granulated blast furnace slag powder, 15 parts of nickel slag powder, 10 parts of water glass, 10 parts of polyaluminum chloride, and 20 parts of water evenly to prepare a recycled fine powder geopolymer.

[0045] Measure the dry shrinkage rate of the recycled fine powder geopolymer prepared in the examples of the present invention, and the measured results are shown in Table 1.

[0046] Example 2

[0047] A low-shrinkage geopolymer cementitious material (by mass) contains the following components:

[0048]

[0049] Mix 60 parts of recycled fine powder (obtained by grinding the fine powder collected in the air separation process of the waste concrete crushing process to a residue on a 80μm square hole sieve of 1.8%), 20 parts of low-temperature calcined recycled fine powder, 10 parts of granulated blast furnace slag powder, 10 parts of nickel slag powder, 10 parts of water glass, 10 parts of polyaluminum chloride, and 20 parts of water evenly to prepare a recycled fine powder geopolymer.

[0050] Measure the dry shrinkage rate of the recycled fine powder geopolymer prepared in the examples of the present invention, and the measured results are shown in Table 1.

[0051] Comparative Example 1

[0052]

[0053] Mix 50 parts of recycled fine powder (obtained by grinding the fine powder collected in the air separation process of the waste concrete crushing process to a residue on a 80μm square hole sieve of 1.8%), 25 parts of granulated blast furnace slag powder, 25 parts of nickel slag powder, 10 parts of water glass, 10 parts of polyaluminum chloride, and 20 parts of water evenly to prepare a recycled fine powder geopolymer.

[0054] Measure the dry shrinkage rate of the recycled fine powder geopolymer prepared in the comparative examples of the present invention, and the measured results are shown in Table 1.

[0055] Table 1 Dry shrinkage performance determination results of low-shrinkage geopolymer cementitious materials

[0056]

[0057] By comparing the dry shrinkage rates of the recycled micro-powder geopolymers prepared from the comparative examples and the examples, it can be seen that, with other components unchanged, the low-temperature calcined recycled micro-powder was not added in the comparative examples, and its dry shrinkage rate was significantly higher than that of Examples 1-2 with the addition of low-temperature calcined recycled micro-powder. It can be seen that the low-temperature calcined recycled micro-powder has an obvious shrinkage-reducing effect. This is because the ground recycled micro-powder has alkali activity. After being compounded with slag and nickel slag, it undergoes an alkali activation reaction under the action of water glass to form strength. As a coagulant, polymeric aluminum chloride can accelerate its dissolution-precipitation process and significantly improve the early strength. However, the biggest problem with geopolymers is their large shrinkage and easy cracking. The main components of the low-temperature calcined recycled micro-powder are calcium oxide and calcium silicate, etc. During its hydration process, it can have a certain micro-expansion effect, reducing its shrinkage and the risk of cracking.

[0058] Therefore, a recycled micro-powder geopolymer and its preparation method provided by the present invention use the ground recycled micro-powder obtained by grinding and screening the fine powder collected in the air separation process of the waste concrete crushing process as the main raw material, supplemented by two solid wastes of low-temperature calcined ground recycled micro-powder, granulated blast furnace slag powder and nickel slag powder, as well as raw materials such as water glass and polymeric aluminum chloride. The prepared recycled micro-powder geopolymer does not require the addition of cement during use, and has the characteristics of good fluidity, high strength, good durability and low dry shrinkage rate. Moreover, it can also achieve the large-scale resource utilization of recycled micro-powder, reduce land occupation, save natural resources and improve the environment. At the same time, its preparation method does not require large equipment and complex processes, does not require cement clinker, and does not require harsh preparation conditions such as high-temperature calcination. Not only is the preparation method simple, but also the utilization rate of recycled micro-powder is high, the preparation cost is low, and the economic benefit is high.

[0059] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the examples, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A regenerated micro-powder geopolymer, characterized in that: Calculated by mass, it includes 50-60 parts of ground regenerated micropowder, 10-20 parts of low-temperature calcined regenerated micropowder, 10-20 parts of slag powder, 10-20 parts of nickel slag powder, 7-10 parts of water glass, 5-10 parts of polymerized aluminum chloride, and 30-40 parts of water.

2. The regenerated micro-powder geopolymer according to claim 1, characterized in that: The ground regenerated micro powder is obtained by grinding the fine powder collected in the air selection process in the waste concrete crushing process to a residue of 1.8% on an 80 μm square hole sieve.

3. The regenerated micro-powder geopolymer according to claim 2, characterized in that: The low-temperature calcined regenerated micropowder is obtained by low-temperature calcining the ground regenerated micropowder at a temperature of 650°C to 850°C.

4. The regenerated micro-powder geopolymer according to claim 1, characterized in that: The water glass is a water glass solution with a modulus of 1.4 to 1.

8.

5. The regenerated micro-powder geopolymer according to claim 1, characterized in that: The polyaluminium chloride is a chemical reagent with an aluminium oxide content of ≥29%.

6. The regenerated micro-powder geopolymer according to claim 1, characterized in that: The slag powder is granulated blast furnace slag powder that meets the S95 grade activity index and fluidity ratio requirements specified in GB / T18046-2017 "Granulated blast furnace slag powder for cement, mortar and concrete".

7. The regenerated micro-powder geopolymer according to claim 1, characterized in that: The nickel slag powder meets the requirements of G90 grade activity index and fluidity ratio specified in JC / T 2503-2018 "Nickel-iron slag powder used in cement and concrete".

8. A method for preparing the regenerated micro-powder geopolymer according to any one of claims 1 to 7, characterized in that: The steps include: Grind the fine powder collected in the air separation process of the waste concrete crushing process to a residue of 80 μm square hole sieve ≤ 1.8% to obtain finely ground recycled fine powder; The ground regenerated micropowder is placed in a muffle furnace and calcined at 650° C. to 850° C. for 20 min to 40 min to obtain low-temperature calcined regenerated micropowder; By weight, 50-60 parts of ground regenerated micro powder, 10-20 parts of low-temperature calcined regenerated micro powder, 10-20 parts of slag powder, 10-20 parts of nickel slag powder, 7-10 parts of water glass, 5-10 parts of polymerized aluminum chloride and 30-40 parts of water are mixed to prepare a slurry; The slurry is injection molded and cured in a curing box to a specified age to obtain a geopolymer cementitious material.

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