Preparation method of single-component alkali slag-regenerated micropowder cement

Abstract

The invention provides a preparation method of single-component alkali slag-regenerated micropowder cement. The method comprises the following steps: mixing regenerated micro powder, slag, nickel slag and a solid alkali activator, and carrying out ball milling to prepare the single-component alkali slag-regenerated micro powder cement. Potential volcanic ash activity in the regenerated micro powder is activated through two activation means of mechanochemistry and alkali excitation, the particle morphology is improved by adjusting the proportion of RBP and RCP in the regenerated micro powder, the alkalinity of a system is increased through nickel slag, the alkali excitation reaction process is promoted, and macroscopic performance is improved. The invention aims to realize resource utilization of the building solid waste regenerated micro powder, the regenerated micro powder is introduced, the mechanical property of the cement is improved, and greenization of a cementing material, an admixture and a production process is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials, and in particular relates to a method for preparing single-component alkali slag-regenerated micro-powder cement. Background Art

[0002] As a major construction country, my country's infrastructure construction volume has far exceeded that of Western countries. With the increasing pace of urban and rural modernization, the construction industry has also developed rapidly. At the same time, a large number of old buildings and illegal buildings are also facing demolition, and the construction waste generated is also increasing day by day.

[0003] Geopolymer is a gel material with a three-dimensional network structure composed of silicon-oxygen tetrahedron and aluminum-oxygen tetrahedron. Compared with ordinary Portland cement, geopolymer has the advantages of excellent mechanical properties, high temperature resistance, good durability, and good acid and alkali corrosion resistance. In terms of environmental protection and economy, the raw materials of geopolymer are mostly low-calcium industrial waste such as fly ash and slag, and the cost is low.

[0004] Recycled micro powder is mainly mortar micro powder, sintered brick powder and some natural aggregate debris in construction solid waste, which contain a large amount of alkaline substances. When recycled micro powder is added to silicate cement as an admixture, it can increase the OH content in the slurry. - Concentration will promote the early strength of cement. Recycled micro powder contains a large amount of silicon and aluminum substances with potential volcanic ash activity, which has the potential to prepare alkali-activated geopolymers.

[0005] The differences in the raw material sources of recycled fired brick powder (RBP) and recycled concrete powder (RCP) determine the differences in their chemical composition and properties. Recycled fired brick powder is made from the crushing of waste fired bricks formed by high-temperature calcination of clay, fly ash, coal gangue, shale and other raw materials. It has a soft and porous texture. Recycled concrete powder is obtained from waste concrete mixed with sand, gravel and cement. Its particles are hard, complex in composition and have many microcracks. Sintered brick powder can react with Ca(OH)2 to form CSH gels. These gels will refine the pore structure, reduce the porosity of mortar and block the connection between pores, which is beneficial to enhancing durability. The chemical composition of recycled fired brick powder and recycled concrete powder is mainly SiO2, CaO and Al2O3, and they have the potential to be made into alkali-activated cementitious materials, but the chemical composition of the two is different and needs to be distinguished in practical applications. The two can obtain the composite advantage of "1+1>2" through moderate compounding.

[0006] Since nickel slag is produced by water quenching and rapid cooling, although the calcium content is low, the content of active SiO2 and amorphous glass in the system is high, and it has certain potential excitation activity. Many scholars use nickel slag as a precursor to prepare geopolymers to explore various properties in order to promote the utilization rate of nickel slag.

[0007] Alkaline activators can chemically react with the active ingredients in the recycled micropowder to generate new mineral structures. These newly generated mineral structures have higher strength and stability, thereby improving the overall performance of cement.

[0008] Mechanochemical activation of regenerated micro powder mainly involves mechanical grinding of the regenerated micro powder to stimulate the potential activity of the regenerated micro powder, refine the regenerated micro powder, remove irregular edges and corners, and make the particle shape more regular. Under the action of mechanical force, the regenerated micro powder crystals have defects such as dislocation and vacancies, forming new activation points, which improves the activity of the regenerated micro powder.

[0009] There are two significant advantages to combining recycled micropowder with alkali-activated cementitious materials. First, single-component alkali slag-recycled micropowder cement is expected to be used as a substitute for conventional silicate cement, which can reduce the exploitation of natural resources, reduce the damage to land resources, and protect limited natural resources; secondly, single-component alkali slag-recycled micropowder cement can effectively solve the pollution problem of solid materials in construction waste, recycle waste resources, and save production costs. Therefore, preparing recycled micropowder from construction solid waste into single-component alkali slag-recycled micropowder cement meets the strategic requirements of sustainable development and recycling, and is conducive to achieving the green development goals of the construction industry. It has good ecological and economic benefits and great social significance. Summary of the invention

[0010] The purpose of the present invention is to provide a method for preparing single-component alkali slag-regenerated micro-powder cement.

[0011] In order to achieve the above object, the present invention adopts the following technical solution: A method for preparing a single-component alkali-slag-regenerated micro-powder cement comprises the following steps: (1) First, the recycled micropowder, slag and nickel slag are respectively ball-milled at 250 r / min-300 r / min for 20 min-60 min, and then the slag, recycled micropowder, nickel slag and an alkali activator with an alkali equivalent of 2%-7% in a mass ratio of 3-5:3-4:1-4 are put into a ball mill and ball-milled for 5 min-15 min to obtain a mixed powder; the recycled micropowder includes recycled sintered brick powder and recycled concrete micropowder, and the recycled sintered brick powder accounts for 40%-60% of the total mass of the recycled micropowder.

[0012] (2) The mixed powder obtained in step (1) is mixed with sand, and then water is added to stir evenly. The mixture is then poured into a mold and placed in a constant temperature water curing box for curing for 24 hours. The mold is then removed, and the mortar test block is then placed in a constant temperature curing room for water curing and taken out after reaching the desired age.

[0013] Furthermore, the mass ratio of the recycled sintered brick powder to the recycled concrete powder in the recycled powder is 1:1.

[0014] Furthermore, the mass ratio of the slag, the recycled micropowder and the nickel slag is 4:4:2.

[0015] Furthermore, the particle size of the recycled concrete powder in the recycled powder is less than 2.36 mm, and the particle size of the recycled sintered brick powder is less than 40 mm.

[0016] Furthermore, the slag is one of S75, S95 or S105 grade granulated blast furnace slag.

[0017] Furthermore, the solid base activator is one of NaOH, Ca(OH)2, and Na2SiO3.

[0018] Furthermore, the nickel slag is one of blast furnace nickel slag and electric furnace nickel slag.

[0019] Furthermore, the ratio of the mixed powder, sand and water is 2:6:1.

[0020] Mechanism: During the ball milling process, the grinding balls transfer their own energy (mainly kinetic energy) to the powder through impact, friction, heat energy, etc. The energy inside the powder is constantly accumulated, which causes the powder to undergo physical and chemical changes, stimulates the potential activity of the regenerated micropowder, refines the regenerated micropowder, removes irregular edges and corners, makes its particle shape more regular, better fills the pores of the cement paste, improves the microstructure of the cement gel, increases the density of the mortar, and thus improves the strength of the cement. At the same time, the alkali activator can provide a higher concentration of OH for the cementitious material paste. - In an alkaline environment, the surface inactive bonds of the regenerated micropowder are easily converted into free unsaturated active bonds, that is, the Si-O and Al-O bonds in the surface SiO2 and Al2O3 are broken to form Si-O-Al network polymers, the degree of polymerization decreases, and it is easy to react with the active ingredients in the system to form C-(A)-SH gel with high strength and water hardness, so as to achieve the effect of alkali-activated micropowder activity, thereby improving the mechanical properties of cement-based materials. At the same time, nickel slag and slag generate mineral phases with strength characteristics, such as calcium silicate (CSH), calcium aluminum silicate (CASH), etc., which refine the particle structure, promote hydration reaction to form hydration products, reduce the porosity of mortar and block the connection between pores, improve the material density, enhance strength, and are beneficial to enhance durability.

[0021] The beneficial effects of the present invention are: (1) The present invention activates the potential activity in the recycled micropowder and nickel slag of construction waste under two activation methods: mechanochemical and alkali excitation. Nickel slag is added to the recycled micropowder (RBP and RCP) to exert its activity and optimize the particle grading. When used together with slag, their hydration reactions can complement each other and provide a longer-term strength improvement. The reaction products are cross-linked and condensed into a network structure with a large amount of flocculent phase filling with slag, which better fills the pores of cement paste, improves the microstructure of cement gel, and thus improves cement strength.

[0022] (2) The invention has a simple formula and strong practicality, and realizes the greening of cementitious materials, admixtures, and production processes. Its raw materials are nearly 100% from waste, and the recycled micro-powder of construction solid waste can be recycled and utilized as resources, effectively solving the pollution problem of construction waste solids, enabling the recycling of waste resources, saving production costs, and meeting the strategic requirements of sustainable development and recycling. In addition, the alkaline substances in the recycled micro-powder may promote the activation of slag-type cementitious properties, which can not only save the amount of alkali activator, but also help improve material performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the XRD pattern of slag.

[0024] Figure 2 SEM images of RBP (left: before ball milling; right: after ball milling).

[0025] Figure 3 SEM images of RCP (left: before ball milling; right: after ball milling).

[0026] Figure 4 This is the XRD pattern of nickel slag.

[0027] Figure 5 This is the XRD pattern of 28d in Example 3.

[0028] Figure 6 This is the SEM image of 28d of Example 3.

[0029] Figure 7 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0030] In order to make the contents of the present invention easier to understand, the technical solution of the present invention is further described below in conjunction with specific implementation methods, but the present invention is not limited thereto.

[0031] A method for preparing a single-component alkali slag-regenerated micro-powder cement, the preparation comprising the following steps: (1) Recycling and storage of slag, recycled powder (RBP, RCP) and nickel slag.

[0032] (2) The chemical composition of the recovered slag, recycled powder (RBP, RCP) and nickel slag was tested, and the results are shown in Table 1. The XRD patterns of slag and nickel slag are shown in Figure 1 and Figure 4 .

[0033] Table 1 Composition analysis of slag, RBP, RCP and nickel slag

[0034] (3) The regenerated powder (RBP, RCP), slag and nickel slag are respectively ball-milled at 250 r / min-300 r / min for 20 min-60 min. Then, the slag, regenerated powder, nickel slag in a mass ratio of 3-5:3-4:1-4 and an alkali activator with an alkali equivalent of 2%-7% are put into a ball mill and ball-milled for 5 min-15 min to obtain a mixed powder.

[0035] (4) The mixed powder obtained in (3) is mixed with the mixed sand and water and stirred evenly. The mixture is then poured into a mold and placed in a constant temperature water curing box for curing for 24 hours. The mold is then removed and the mortar specimen is placed in a constant temperature curing room for water curing. The specimen is then taken out after reaching the desired age.

[0036] Example 1 (1) Recycled powder (RBP / RCP=50:50) was ball-milled at 270 r / min for 40 min, slag and nickel slag were ball-milled at 270 r / min for 20 min, then slag, recycled powder, nickel slag and Ca(OH)2 with a mass ratio of 3:3:4 were put into a ball mill and ball-milled at 270 r / min for 5 min to obtain a mixed powder with a ball-to-material ratio of 5:1. The slag grade was S75, the nickel slag was blast furnace nickel slag, the particle size of recycled concrete powder in the recycled powder was less than 2.36 mm, and the particle size of recycled sintered brick powder was less than 40 mm.

[0037] (2) Mix 450 g of the mixed powder with 1350 g of sand and 225 g of water, stir evenly, then inject into the mold and place it in a 25°C constant temperature water curing box for curing for 24 hours before removing the mold. Then place the mortar specimen in a constant temperature curing room for water curing and take it out after reaching the age.

[0038] Example 2 (1) Recycled powder (RBP / RCP=50:50) was ball-milled at 270r / min for 40min, slag and nickel slag were ball-milled at 270r / min for 20min, and then slag, recycled powder, nickel slag and Ca(OH)2 with a mass ratio of 3:4:3 were put into a ball mill and ball-milled for 5min to obtain a mixed powder with a ball-to-material ratio of 5:1. The slag grade was S75, the nickel slag was blast furnace nickel slag, the particle size of recycled concrete powder in the recycled powder was less than 2.36mm, and the particle size of recycled sintered brick powder was less than 40mm.

[0039] (2) Mix 450 g of the mixed powder with 1350 g of sand and 225 g of water, stir evenly, then inject into the mold and place in a 25°C constant temperature water curing box for curing for 24 h. Then remove the mold and place the mortar specimen in a constant temperature curing room for water curing. Take it out after reaching the age.

[0040] Example 3 (1) Recycled powder (RBP / RCP=50:50) was ball-milled at 270r / min for 40min, slag and nickel slag were ball-milled at 270r / min for 20min, and then slag, recycled powder, nickel slag and Ca(OH)2 with a mass ratio of 4:4:2 were put into a ball mill and ball-milled for 5min to obtain a mixed powder with a ball-to-material ratio of 5:1. The slag grade was S75, the nickel slag was blast furnace nickel slag, the particle size of recycled concrete powder in the recycled powder was less than 2.36mm, and the particle size of recycled sintered brick powder was less than 40mm.

[0041] (2) Mix 450 g of the mixed powder with 1350 g of sand and 225 g of water, stir evenly, then inject into the mold and place in a 25°C constant temperature water curing box for curing for 24 h. Then remove the mold and place the mortar specimen in a constant temperature curing room for water curing. Take it out after reaching the age.

[0042] Example 4 (1) Recycled micro powder (RBP / RCP=50:50) was ball milled at 270 r / min for 40 min, slag and nickel slag were ball milled at 270 r / min for 20 min, and then slag, recycled micro powder, nickel slag and Ca(OH)2 with a mass ratio of 4:3:3 were put into a ball mill and ball milled for 5 min to obtain a mixed powder, and the ball-to-material ratio was 5:1. The slag grade was S75, the nickel slag was blast furnace nickel slag, the particle size of recycled concrete micro powder in the recycled micro powder was less than 2.36 mm, and the particle size of recycled sintered brick powder was less than 40 mm.

[0043] (2) Mix 450 g of the mixed powder with 1350 g of sand and 225 g of water, and mix them evenly. Then pour them into the mold and place them in a constant temperature water curing box for curing for 24 hours. Then remove the mold and place the mortar specimen in a constant temperature curing room at 25°C for water curing. Take them out after they reach the required age.

[0044] Example 5 (1) Recycled powder (RBP / RCP=50:50) was ball-milled at 270 r / min for 40 min, slag and nickel slag were ball-milled at 270 r / min for 20 min, and then slag, recycled powder, nickel slag and Ca(OH)2 with a mass ratio of 5:4:1 were put into a ball mill and ball-milled for 5 min to obtain a mixed powder with a ball-to-material ratio of 5:1. The slag grade was S75, the nickel slag was blast furnace nickel slag, the particle size of recycled concrete powder in the recycled powder was less than 2.36 mm, and the particle size of recycled sintered brick powder was less than 40 mm.

[0045] (2) Mix 450 g of the mixed powder with 1350 g of sand and 225 g of water, stir evenly, then inject into the mold and place in a 25°C constant temperature water curing box for curing for 24 h. Then remove the mold and place the mortar specimen in a constant temperature curing room for water curing. Take it out after reaching the age.

[0046] Comparative Example 1 (1) Recycled powder (RBP / RCP=50:50) was ball-milled at 270r / min for 40min, slag and nickel slag were ball-milled at 270r / min for 20min, and then slag, recycled powder, nickel slag and Ca(OH)2 with a mass ratio of 5:5:0 were put into a ball mill and ball-milled for 5min to obtain a mixed powder with a ball-to-material ratio of 5:1. The slag grade was S75, the nickel slag was blast furnace nickel slag, the particle size of recycled concrete powder in the recycled powder was less than 2.36mm, and the particle size of recycled sintered brick powder was less than 40mm.

[0047] (2) Mix 450 g of the mixed powder with 1350 g of sand and 225 g of water, stir evenly, then inject into the mold and place in a 25°C constant temperature water curing box for curing for 24 h. Then remove the mold and place the mortar specimen in a constant temperature curing room for water curing. Take it out after reaching the age.

[0048] According to the provisions of GB / T 17671-2021 "Test method for strength of cement mortar (ISO method)", the strength of cement after standard curing for 28 days is measured, and its performance test is shown in Table 2.

[0049] Table 2 Mechanical properties test results of different single-component alkali-slag-recycled micro-powder cement

[0050] It can be seen from Table 2 that when nickel slag is added in an appropriate proportion, the slag plays a role in increasing the alkalinity, thereby promoting the reaction rate of nickel slag alkali activation, and fully stimulating the volcanic ash activity of the regenerated micropowder. The composite blending of nickel slag and slag optimizes the particle grading, and a small amount of unreacted nickel slag fills the pores and plays a certain skeleton role. The toughness of the overall structure sample is improved to a certain extent, and the reaction products fill each other to make up for the gaps, reduce the porosity, and further improve the compressive / flexural strength of the cement. Among them, Example 3 has the best effect.

[0051] Depend on Figure 1 and Figure 5 It can be found that the phases of different raw materials are quite different. The main phases of pure slag are quartz and calcite ( Figure 1 ), while the recycled micro powder is mainly composed of quartz, calcite, hydrotalcite, and albite, and it can be clearly found that compared with pure slag, Example 3 ( Figure 5 ) has a higher quartz diffraction peak, indicating that its quartz crystallinity and content are higher, and albite diffraction peaks are newly added. Albite is an alkali-tolerant substance. Aluminosilicates with a framework structure of sodium can be dissolved in alkaline solutions to release alkaline silicon cations (Si-O-) and intermediate silanols (Si-OH), which then undergo condensation reactions with other silicon-aluminum monomers or oligomers to form a three-dimensional network gel composed of [SiO4] and [AlO4] tetrahedrons. Figure 5 In the range of 20°~40°, it can be found that there are many broad diffuse peaks or "steamed bun" peaks, indicating the existence of amorphous gel. The gel in this area is mainly CSH and CASH.

[0052] Figure 2 , Figure 3 These are the SEM images of RBP and RCP before ball milling. It can be seen from the figure that the powder particles are large and have sharp edges and corners, and the surfaces of some large particles are rough and soft, and some particles have microcracks. After ball milling, the particles of RBP and RCP are gradually refined, and the particle morphology changes from irregular to spherical. The irregular edges and corners are weakened, the morphology is optimized, and the overall specific surface area is increased, which increases the hydration reaction rate of RBP and RCP.

[0053] Figure 6 It can be seen that under the activation means of the alkaline activator Ca(OH)2, slag, recycled micropowder and nickel slag can react well to generate a large amount of gel, which is tightly bonded with some inert slag particles to form a skeleton, making its microstructure more dense and helping to improve the strength of cement.

[0054] Therefore, the best example of the single-component alkali slag-recycled micropowder cement prepared by mechanochemistry in the present invention is that RBP in the recycled micropowder accounts for 50% of the total mass of the recycled micropowder, the mass ratio of slag, recycled micropowder and nickel slag is 4:4:2, and the alkali equivalent of Ca(OH)2 is 4%. This mix ratio can maximize the activity of the recycled micropowder and nickel slag and improve the mechanical properties.

[0055] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a single-component alkali slag-regenerated micro-powder cement, characterized in that: The following steps are involved: (1) First, the recycled micropowder, slag and nickel slag are respectively ball-milled at 250 r / min-300 r / min for 20 min-60 min, and then the slag, recycled micropowder, nickel slag and an alkali activator with an alkali equivalent of 2%-7% in a mass ratio of 3-5:3-4:1-4 are put into a ball mill and ball-milled for 5 min-15 min to obtain a mixed powder; the recycled micropowder includes recycled sintered brick powder and recycled concrete micropowder, and the recycled sintered brick powder accounts for 40%-60% of the total mass of the recycled micropowder; (2) The mixed powder obtained in step (1) is mixed with sand, and then water is added to stir evenly. The mixture is then poured into a mold and placed in a constant temperature water curing box for curing for 24 hours. The mold is then removed, and the mortar test block is then placed in a constant temperature curing room for water curing and taken out after reaching the desired age.

2. The preparation method according to claim 1, characterized in that: The mass ratio of the recycled sintered brick powder to the recycled concrete powder in the recycled powder is 1:

1.

3. The preparation method according to claim 1, characterized in that: The mass ratio of the slag, the recycled micro powder and the nickel slag is 4:4:

2.

4. The preparation method according to claim 1, characterized in that: The particle size of the recycled concrete powder in the recycled powder is less than 2.36 mm, and the particle size of the recycled sintered brick powder is less than 40 mm.

5. The preparation method according to claim 1, characterized in that: The slag is one of S75, S95 or S105 grade granulated blast furnace slag.

6. The method for preparing the single-component alkali-slag-regenerated micro-powder cement according to claim 1, characterized in that: The solid base activator is one of NaOH, Ca(OH)2, and Na2SiO3.

7. The preparation method according to claim 1, characterized in that: The nickel slag is one of blast furnace nickel slag and electric furnace nickel slag.

8. The preparation method according to claim 1, characterized in that: The ratio of the mixed powder, sand and water is 2:6:1.

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