Physical and chemical synergistic modified superfine mineral admixture and preparation method thereof

Abstract

The invention provides a physicochemical synergistic modified superfine mineral admixture. The physicochemical synergistic modified superfine mineral admixture is prepared from the following raw materials in percentage by weight: 20-60 parts of granite powder, 5-25 parts of furnace slag, 20-50 parts of fly ash, 4-5 parts of nano silicon dioxide, 2-10 parts of a composite activator, 0.1-3 parts of a reinforced activation material, 1-5 parts of desulfurized gypsum, 0.01-0.05 part of triethanolamine, 0.1-0.5 part of nano C-S-H seed crystal and 0.1-0.5 part of PVA (Polyvinyl Alcohol) fiber, the composite exciting agent is a composition of NaOH, NaSO and sodium metasilicate according to the mass ratio of (1-3): (0.5-2): (0.2-1). The superfine mineral admixture adopts a three-stage particle size compound system of coarse particles, medium particles and superfine particles. The physicochemical synergistic modified superfine mineral admixture provided by the invention has good early strength performance, and the compressive strength and the crack resistance are also greatly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of concrete admixtures, and particularly relates to a physico-chemical synergistically modified superfine mineral admixture and a preparation method thereof. BACKGROUND

[0002] Granite stone powder is a powder produced in the processing of stone sawing, cutting and grinding in stone factories. The powder has uneven particle size distribution and very low recycling rate. Most of the powder is piled up without treatment, polluting the surrounding atmosphere, soil and other environments, causing a large amount of resource waste and restricting the sustainable economic development.

[0003] The chemical composition of granite stone powder is similar to that of industrial fly ash, and the content of silicon dioxide and aluminum oxide is more than 90%. At present, researchers have studied the feasibility of using granite stone powder as a cement admixture. By mixing with silica ash, fly ash and other mineral admixtures, the problem of granite stone powder pollution and resource waste can be solved. Chinese patent CN110903048A discloses a high-activity superfine mineral admixture and a preparation method thereof. The high-activity superfine mineral admixture is composed of the following raw materials by weight percentage: 20-60% of granite stone powder, 5-25% of slag, 20-50% of fly ash, 0.1-10% of an activator, 0.1-3% of an enhanced activation material, and 1-5% of desulfurized gypsum. The existing admixture preparation process in the prior art solves the technical problem of complex preparation process. The preparation process is simple, and the obtained high-activity superfine mineral admixture reaches the S95 level or above. However, in order to increase its application range, higher requirements are put forward for its early strength performance, compressive strength and crack resistance. SUMMARY

[0004] The present application aims to overcome the above technical deficiencies and provides a physico-chemical synergistically modified superfine mineral admixture and a preparation method thereof. The admixture has good early strength performance, and the compressive strength and crack resistance are also greatly improved.

[0005] To achieve the above technical purpose, the first solution of the present application provides a physico-chemical synergistically modified superfine mineral admixture, which is composed of the following raw materials by weight percentage: 20-60 parts of granite stone powder, 5-25 parts of slag, 20-50 parts of fly ash, 4-5 parts of nano-silicon dioxide, 2-10 parts of a composite activator, 0.1-3 parts of an enhanced activation material, 1-5 parts of desulfurized gypsum, 0.01-0.05 parts of triethanolamine, 0.1-0.5 parts of nano C-S-H crystal seeds, and 0.1-0.5 parts of PVA fiber; The composite activator is a combination of NaOH, Na2SO4 and sodium metasilicate in a mass ratio of 1-3:0.5-2:0.2-1; the superfine mineral admixture adopts a three-level particle size compounding system of coarse particles+medium particles+superfine particles, wherein the granite powder and the slag are coarse particles with a D50 of 10-20 microns; the fly ash is medium particles with a D50 of 5-10 microns; and the nano-silicon dioxide is superfine particles with a D50 of 0.05-0.1 micron.

[0006] The second solution of the present application provides a preparation method of the physicochemical synergistically modified superfine mineral admixture, comprising the following steps: (1) drying the granite powder, the slag and the fly ash, and simultaneously ultrasonically dispersing the nano-silicon dioxide and the nano C-S-H crystal seeds into the triethanolamine and an appropriate amount of water reducing agent to obtain a nano-dispersed suspension; (2) coarsely grinding the granite powder, the slag and the fly ash, and adding the composite activator, the reinforcing activated material, the desulfurized gypsum and the PVA fiber during the coarse grinding process; and (3) finely grinding the material after the coarse grinding, and adding the nano-dispersed suspension during the fine grinding process, so that the physicochemical synergistically modified superfine mineral admixture is prepared after the fine grinding is completed.

[0007] Compared with the prior art, the present application has the following beneficial effects: The present application has better early strength performance, compressive strength and crack resistance by the physicochemical synergistic modification, in particular: (1) the composite activator in the present application adopts a compounding system of NaOH, Na2SO4 and sodium metasilicate, wherein the NaOH destroys the glass body structure of the granite powder, the Na2SO4 promotes the generation of AFt, and the sodium metasilicate is used to improve the dissolution rate of the silicon-aluminum phase; the added triethanolamine acts as an organic catalyst to accelerate the complexation and transmission of calcium ions; and the nano C-S-H crystal seeds are further added as a hydration product template to reduce the nucleation barrier. Through the synergistic effect of the above components, the early strength can be increased by 20%-30%. (2) The PVA fiber is added in the present application to inhibit the expansion of microcracks and improve the crack resistance of the material by more than 40%; and through the three-level particle size compounding optimization system of coarse particles+medium particles+superfine particles, the most compact packing is achieved, the porosity is reduced (porosity < 26%), and thus the compressive strength of the material is improved. DETAILED DESCRIPTION

[0008] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0009] For the first solution of the present application, the present application provides a physicochemical synergistically modified superfine mineral admixture, which is composed of the following raw materials in weight percentage: Granite powder 20~60 parts, slag 5~25 parts, fly ash 20~50 parts, nano silicon dioxide 4~5 parts, composite activator 2~10 parts, enhanced activation material 0.1~3 parts, desulfurization gypsum 1~5 parts, triethanolamine 0.01~0.05 parts, nano C-S-H crystal seed 0.1~0.5 parts, PVA fiber 0.1~0.5 parts;The composite activator is a composition of NaOH, Na2SO4 and sodium metasilicate in a mass ratio of 1~3:0.5~2:0.2~1. The superfine mineral admixture adopts a three-level particle size compounding system of coarse particles+medium particles+superfine particles, wherein the granite powder and the slag are coarse particles with a D50 of 10~20 μm; the fly ash is medium particles with a D50 of 5~10 μm; and the nano silicon dioxide is superfine particles with a D50 of 0.05~0.1 μm. The enhanced activation material is one or more of calcium formate, silica ash or sodium silicate.

[0010] The mass percentage of each component in the granite powder is: SiO2 75~90%, Al2O3 8~15%, Fe2O3 0.1~3%, CaO 0.1~3%, MgO 2~5%, loss on ignition 0.1~1%; the initial water content of the granite powder is 15~20%, and the water content of the granite powder after drying is about 0.8%; before grinding, the D50 of the granite powder is 15 μm, and the specific surface area is 300~500 m 2 / kg; the mass percentage of each component in the slag is: SiO2 50~60%, Al2O3 15~25%, Fe2O3 3~5%, CaO 3~8%, MgO 0.1~5%, SO3 0.1~0.5%, loss on ignition 5~15%; the initial water content of the slag is 25~30%, and the water content of the slag after drying is about 0.8%; before grinding, the specific surface area of the slag is 300~500 m 2 / kg; the mass percentage of each component in the fly ash is: SiO2 53~65%, Al2O3 20~30%, Fe2O3 2~5%, CaO 2~5%, MgO 1~3%, SO3 0.1~0.5%, loss on ignition 1~5%; before grinding, the specific surface area of the fly ash is 300~400 m² / kg; the content of calcium sulfate dihydrate in the desulfurization gypsum is 85~95%; before grinding, the specific surface area of the desulfurization gypsum is 80~120 m 2 / kg; the D50 of the nano silicon dioxide is 50 nm, and the specific surface area is 300~500 m² / kg.

[0011] For the second solution of the present invention, a method for preparing a physicochemically modified ultrafine mineral admixture is provided, comprising the following steps: (1) drying granite powder, slag and fly ash, drying granite powder, slag and fly ash at 105°C to a moisture content of <1%, and simultaneously ultrasonically dispersing nano-silica and nano-CSH seeds into triethanolamine and an appropriate amount of water-reducing agent, the ultrasonic dispersion frequency being 40 kHz and the processing time being 15 min, to obtain a nano-dispersed suspension; (2) coarsely grinding granite powder, slag and fly ash, adding composite activator, reinforcing and activating material, desulfurized gypsum and PVA fiber during the coarse grinding process, the specific surface area of ​​the mixture after coarse grinding being ≥600m². 2 / kg; (3) Fine grinding is performed on the coarsely ground material. During the fine grinding process, a nano-dispersed suspension is added. After the fine grinding is completed, the physicochemically modified ultrafine mineral admixture is obtained. The specific surface area of ​​the finely ground ultrafine mineral admixture is ≥800m². 2 / kg. Because nanomaterials are added to the raw materials in this invention, the specific surface area of ​​the resulting ultrafine mineral admixture is significantly improved.

[0012] Examples 1-3 Examples 1-3 provide three different physicochemically synergistically modified ultrafine mineral admixtures, which were prepared using the methods described above. The raw material proportions of the physicochemically synergistically modified ultrafine mineral admixtures provided in Examples 1-3 are shown in the table below:

[0013] As can be seen from the table above, by using the raw materials and process parameters of this invention, and through the addition of nanomaterials and the optimization of three-level particle size distribution, a specific surface area ≥800m² can be obtained. 2 / kg of physicochemically modified ultrafine mineral admixtures are used to improve product activity.

[0014] Experimental groups 1-3 Referring to GB / T18046-2017 "Granulated Blast Furnace Slag Powder for Cement, Mortar and Concrete", concrete performance tests were conducted on the physicochemically modified ultrafine mineral admixtures in Examples 1-3 of this invention. Early plastic crack resistance tests were performed using the GB / T 50082-2009 circular restraint method. The reference cement was PO42.5 ordinary Portland cement, and the sand used was Chinese ISO standard sand. The proportions of all ingredients were: cement 225g, standard sand 450g, physicochemically modified ultrafine mineral admixture 225g, and water 225g. The standard control group consisted of cement 450g, standard sand 450g, and water 225g. The test results are shown in the table below. The physicochemically modified ultrafine mineral admixtures from Examples 1-3 were used in test groups 1-3, respectively.

[0015]

[0016] As shown in the table above, the 7-day activity index of the physicochemically modified ultrafine mineral admixtures in Examples 1-3 of this invention is greater than 90%, indicating a significant improvement in early strength performance. This is mainly due to the synergistic effect of the composite activator and nano-CSH seeds. Because a three-level particle size optimization system was adopted to achieve the densest packing, the 28-day compressive strength activity index reached 100-110%, meeting or exceeding the S95 standard. Furthermore, the addition of PVA fibers in this invention inhibits microcrack propagation. As shown in the table above, the initial cracking time is significantly extended, and the crack width and number of cracks are significantly reduced, resulting in a crack resistance improvement of over 40%.

Claims

1. A physicochemically synergistically modified ultrafine mineral admixture, characterized in that, It consists of the following parts by weight of raw materials: 20-60 parts granite powder, 5-25 parts slag, 20-50 parts fly ash, 4-5 parts nano silica, 2-10 parts composite activator, 0.1-3 parts reinforcing and activating material, 1-5 parts desulfurized gypsum, 0.01-0.05 parts triethanolamine, 0.1-0.5 parts nano CSH seed crystals, and 0.1-0.5 parts PVA fiber; The composite activator is a composition of NaOH, Na2SO4 and sodium metasilicate in a mass ratio of 1~3:0.5~2:0.2~1; The ultrafine mineral admixture adopts a three-level particle size compound system of coarse particles, medium particles, and ultrafine particles. Among them, granite powder and slag are coarse particles with a D50 of 10~20μm; fly ash is a medium particle with a D50 of 5~10μm; and nano silica is an ultrafine particle with a D50 of 0.05~0.1μm.

2. The physicochemically modified ultrafine mineral admixture according to claim 1, characterized in that: The enhancing and activating material is one or more of calcium formate, silica fume, or sodium silicate.

3. The physicochemically modified ultrafine mineral admixture according to claim 1, characterized in that: The granite powder and slag have a D50 of 15 μm and a specific surface area of ​​300~500 m² / kg.

4. The physicochemically modified ultrafine mineral admixture according to claim 1, characterized in that: The fly ash has a D50 of 8 μm and a specific surface area of ​​300~400 m² / kg.

5. The physicochemically modified ultrafine mineral admixture according to claim 1, characterized in that: The nano-silica has a D50 of 50 nm and a specific surface area of ​​300~500 m² / kg.

6. The physicochemically modified ultrafine mineral admixture according to claim 1, characterized in that: The desulfurized gypsum contains 85-95% calcium sulfate dihydrate and has a specific surface area of ​​80-120 m². 2 / kg.

7. A method for preparing a physicochemically synergistically modified ultrafine mineral admixture, characterized in that, The process includes the following steps: (1) Drying granite powder, slag and fly ash, and simultaneously ultrasonically dispersing nano-silica and nano-CSH seeds into triethanolamine and an appropriate amount of water-reducing agent to obtain a nano-dispersed suspension; (2) Co-grinding granite powder, slag and fly ash, adding composite activator, reinforcing and activating material, desulfurized gypsum and PVA fiber during the coarse grinding process; (3) Fine grinding the coarsely ground material, adding the nano-dispersed suspension during the fine grinding process, and obtaining the physicochemically modified ultrafine mineral admixture after the fine grinding is completed.

8. The method for preparing the physicochemically synergistically modified ultrafine mineral admixture according to claim 7, characterized in that: In step (1), the granite powder, slag and fly ash are dried at 105℃ to a moisture content of <1%; the ultrasonic dispersion frequency is 40 kHz and the processing time is 15 min.

9. The method for preparing the physicochemically synergistically modified ultrafine mineral admixture according to claim 7, characterized in that: The specific surface area of ​​the mixture after coarse grinding in step (2) is ≥600m². 2 / kg.

10. The method for preparing the physicochemically synergistically modified ultrafine mineral admixture according to claim 7, characterized in that: Step (3) The specific surface area of ​​the finely ground ultrafine mineral admixture is ≥800m². 2 / kg.

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