High water-resistant phosphogypsum self-leveling mortar and preparation method thereof

Abstract

The application discloses a kind of high water-resistance phosphogypsum self-leveling mortar, it is characterized in that composition is as follows according to weight fraction: phosphogypsum 80-90 parts, cement 2-5 parts, mineral powder 1-3 parts, ethyl cellulose 0.4-0.8 parts, nano silicon dioxide 6-8 parts, microcapsule 12-14 parts, water reducing agent 1.6-1.8 parts, defoaming agent 0.1-0.3 parts, retarder 0.08-0.12 parts, water 26-30 parts;In the application, the hardly soluble hydration product formed by cement and mineral powder in mixture, ethyl cellulose and nano silicon dioxide can form network structure to fill the tiny pore in mortar and prevent water permeation, enhance water resistance, finally by encapsulating waterproof agent in microcapsule prepared by gelatin, when contact with water, it will be pressed and dissolved, release waterproof agent to fill pore and crack, form waterproof barrier, improve the water resistance of gypsum mortar.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of building materials, and particularly relates to high-water-resistance phosphogypsum self-leveling mortar and a preparation method thereof. BACKGROUND

[0002] In the process of building construction, the ground may have unevenness, unevenness or defects, etc. However, with people's increasing requirements for the ground, it is hoped that the ground can present a flat, smooth and beautiful effect. The phosphogypsum self-leveling mortar has good fluidity and self-leveling property, can rapidly and uniformly spread out, reduces the workload and construction time of construction personnel, and compared with traditional ground repair materials, the phosphogypsum self-leveling mortar can provide higher construction efficiency and convenience. In addition, the phosphogypsum self-leveling mortar is usually composed of gypsum, water and other additives, does not contain harmful volatile organic compounds (VOCs), and is friendly to the indoor environment. Overall, due to the high flatness, construction convenience and good decoration of the phosphogypsum self-leveling mortar, it is widely used in building construction and decoration.

[0003] The traditional phosphogypsum self-leveling mortar is prone to cracking, deformation, bubbles, loss of strength and water resistance after being contacted with water. The existing related technologies and methods mainly increase the flexibility and ductility of the mortar by adding a modifier, enhance the water resistance of the mortar by adding inorganic admixtures or waterproof agents, and control the amount of added water, reasonable construction technology and adjustment of construction environment. However, these methods do not significantly improve the water resistance of the phosphogypsum self-leveling mortar, and cannot significantly improve the water resistance.

[0004] In 202110382252.5, a water-resistant gypsum-based self-leveling mortar and a preparation method thereof are adopted, and an epoxy emulsion, a water-soluble amine and a large amount of admixtures are added, and the components need to be configured in proportion, which leads to too complex components and increases the difficulty of actual construction operation. In 202010899497.0, a preparation method of a water-resistant and shock-resistant gypsum-based self-leveling material is adopted, which solves the problem of fluidity, but the activation of anhydrous phosphogypsum is not complete, and the product stability is not high. In 201910674995.2, a new water-resistant gypsum-based self-leveling material is adopted, which solves the problem of poor early water resistance, but cannot resist the humid environment for a long time, and the cost of raw materials is high. SUMMARY

[0005] Microcapsules are solid microparticles prepared by embedding solid, liquid or gaseous active substances in a microcapsule using special methods, which can realize powderization, isolation, slow release and controlled release of the core material while retaining the original properties of the core material. The preparation of microcapsules is mainly realized through the microencapsulation process, that is, the substance to be coated is first refined into solid particles or liquid droplets with extremely small particle size, then the polymer with film-forming property is deposited and coated on the surface of the core material using special methods to form a seamless film, and finally the microcapsules are prepared through separation, drying and other processes.

[0006] Due to the excellent water resistance, sealing property and controllable release of the microcapsules, the additives with water resistance can be carried and released when contacted with water to fill the pores in the gypsum, thereby greatly improving the water resistance of the gypsum.

[0007] The present application aims to provide a high water-resistant phosphogypsum self-leveling mortar and a preparation method thereof. The insoluble hydration products formed by cement and mineral powder in the mixture, ethyl cellulose and nanosilica can form a network structure to fill the small pores in the mortar and prevent water penetration to enhance water resistance. Finally, the waterproof agent is encapsulated in the microcapsules prepared from gelatin, which will be crushed and dissolved when contacted with water to release the waterproof agent to fill the pores and cracks, form a waterproof barrier and improve the water resistance of the gypsum mortar.

[0008] To achieve the above-mentioned purpose, the technical scheme is as follows:

[0009] The high water-resistant phosphogypsum self-leveling mortar comprises the following components by weight fraction:

[0010] Phosphogypsum 80-90 parts, cement 2-5 parts, mineral powder 1-3 parts, ethyl cellulose 0.4-0.8 parts, nanosilica 6-8 parts, microcapsules 12-14 parts, water reducing agent 1.6-1.8 parts, defoaming agent 0.1-0.3 parts, retarder 0.08-0.12 parts, and water 26-30 parts.

[0011] According to the above scheme, the phosphogypsum is alpha-type phosphorus building gypsum with a pH value of 6-7 and an average particle size of 30-40 μm.

[0012] According to the above scheme, the cement is ordinary portland cement with a strength grade of 42.5.

[0013] According to the above scheme, the mineral powder is S95 grade mineral powder.

[0014] According to the above scheme, the ethyl cellulose is white powder with a viscosity of 200 mpa.s and a density of 1.45 g / m3.

[0015] According to the above scheme, the nanosilica is white powder with a particle size of 10-20 nm.

[0016] According to the above scheme, the water reducing agent is a polycarboxylic acid high-performance water reducing agent, and the water reducing rate is 28-30%.

[0017] According to the above scheme, the defoaming agent is one of P803, A240, DEE FO 1015, and BYK-012, and the pH value is 5-7.

[0018] According to the above scheme, the retarder is a degraded polyamide calcium salt.

[0019] According to the above scheme, the preparation method of the microcapsule comprises the following steps:

[0020] 10-15 parts of gelatin are dissolved in 10-12 parts of propylene glycol, heated to above 80 DEG C; 8-14 parts of expanded graphite are added, stirred at a low speed of 100 r / min for 3 min, and then stirred at a high speed of 3000 r / min for 10 min; after cooling to room temperature, solid-liquid separation is carried out, and after washing and drying, the microcapsule is obtained.

[0021] According to the above scheme, the gelatin is colorless particles, the pH value is 5.5-7, the Brookfield viscosity is 6.8 mpa.s, the moisture content is 5%, and the density is 1.37 g / m 3 .

[0022] According to the above scheme, the expanded graphite is in a powdery form, the carbon content is 95%-98%, the expansion ratio is 200-300 times, the pH value is 3-8, and the particle size is 0.2-0.3 mm.

[0023] According to the above scheme, the propylene glycol is a transparent viscous liquid, the viscosity is 86 mpa.s, and the density is 1.04 g / m 3 .

[0024] The preparation method of the high-water-resistance phosphogypsum self-leveling mortar comprises the following steps:

[0025] (1) first, phosphogypsum, cement, mineral powder and nano silicon dioxide are mixed and stirred to obtain uniform powder; ethyl cellulose, water reducing agent, defoaming agent and retarder are dissolved in water to obtain a solution;

[0026] (2) the obtained solution and the powder are mixed and stirred to obtain a flowable slurry;

[0027] (3) the microcapsule is scattered on the surface of the slurry, and is allowed to sink into the slurry by gravity to obtain the high-water-resistance phosphogypsum self-leveling mortar.

[0028] Compared with the prior art, the application has the following beneficial effects:

[0029] The insoluble hydration products formed by the cement and the mineral powder in the mixture fill the larger pores in the gypsum mortar, so that the large pores are reduced, and the water resistance is improved.

[0030] Ethyl cellulose and nano-silica can form a network structure to fill the small pores in the gypsum mortar, prevent further penetration of water, and thus enhance water resistance.

[0031] The waterproofing agent is encapsulated in the microcapsules prepared from gelatin, which will be crushed and dissolved when in contact with water, releasing the waterproofing agent to fill the pores and cracks, forming a waterproof barrier, and improving the water resistance of the gypsum mortar.

[0032] The above three functions complement each other, first making the internal large pores smaller, then forming a network structure in the small pores to further improve the water resistance of the gypsum mortar, and finally adding the microcapsules attached to the network structure, which release the waterproofing agent to eliminate the effect of water when the surface of the gypsum component is damp or encounters water, achieving long-term waterproofing purposes. After the synergistic effect of the three waterproofing mechanisms, the water resistance of the gypsum mortar is greatly improved. DETAILED DESCRIPTION

[0033] The following examples further illustrate the technical solutions of the present application, but do not limit the scope of protection of the present application.

[0034] The specific embodiment provides a preparation method of microcapsules:

[0035] According to weight parts, 10-12 parts of propylene glycol are taken in a beaker, then 10-15 parts of gelatin are dissolved in the propylene glycol, heated to 80℃ and kept at constant temperature. 8-14 parts of expanded graphite are added, first stirred at a low speed of 100 r / min for 3 min, then stirred at a high speed of 3000 r / min for 10 min, to promote the microcapsule wall to gather around the core material, and finally form the microcapsules. The solution is slowly cooled to 30℃ at a speed of 10℃ / h, at which time the microcapsules can be solidified and precipitated, then the newly formed microcapsules are washed with anhydrous ethanol solution to remove impurities in the solvent, and finally dried in a 40℃ oven to constant weight. A grading device is used to control the particle size of the microcapsules and perform grading packaging, and stored in a dry environment to ensure its stability.

[0036] Specifically, the gelatin is colorless particles, with a pH value of 5.5-7, a Brookfield viscosity of 6.8 mpa.s, a moisture content of 5%, and a density of 1.37 g / m 3 .

[0037] Specifically, the expanded graphite is in powder form, with a carbon content of 95%-98%, an expansion ratio of 200-300 times, a pH value of 3-8, and a particle size of 0.2-0.3 mm.

[0038] Specifically, the propylene glycol is a transparent viscous liquid, with a viscosity of 86 mpa.s and a density of 1.04 g / m 3 .

[0039] The specific embodiment further provides a preparation method of the high-water-resistance phosphogypsum self-leveling mortar, comprising the following steps:

[0040] (1) first, mix phosphogypsum, cement, mineral powder and nano-silicon dioxide to obtain uniform powder; dissolve ethyl cellulose, water-reducing agent, defoaming agent and retarder in water to obtain a solution;

[0041] (2) mix the solution and the powder to obtain a flowable slurry;

[0042] (3) sprinkle microcapsules on the surface of the slurry, and then allow the microcapsules to sink into the slurry by gravity to obtain the high-water-resistance phosphogypsum self-leveling mortar.

[0043] Specifically, the raw material composition is as follows in terms of weight fraction:

[0044] Phosphogypsum 80-90 parts, cement 2-5 parts, mineral powder 1-3 parts, ethyl cellulose 0.4-0.8 parts, nano-silicon dioxide 6-8 parts, microcapsules 12-14 parts, water-reducing agent 1.6-1.8 parts, defoaming agent 0.1-0.3 parts, retarder 0.08-0.12 parts, and water 26-30 parts.

[0045] Specifically, the phosphogypsum is α-type phospho building gypsum, the pH value is 6-7, and the average particle size is 30-40 μm.

[0046] Specifically, the cement is ordinary Portland cement with a strength grade of 42.5, and the mineral powder is S95 grade mineral powder.

[0047] Specifically, the ethyl cellulose is white powder, the viscosity is 200 mpa.s, and the density is 1.45 g / m3.

[0048] Specifically, the nano-silicon dioxide is white powder, and the particle size is 10-20 nm.

[0049] Specifically, the water-reducing agent is a polycarboxylic acid high-performance water-reducing agent, the water-reducing rate is 28-30%, the defoaming agent is one of P803, A240, DEE FO 1015 and BYK-012, the pH value is 5-7, and the retarder is a degraded polyamide calcium salt.

[0050] The raw material composition of the high-water-resistance phosphogypsum self-leveling mortar in the specific embodiment is shown in Table 1.

[0051] After the self-leveling mortar obtained in each example and the comparative example is constructed, the self-leveling mortar is maintained under the conditions of a temperature of 20±2 ℃ and a humidity of 70%-80% for 28 days, and then is dried to constant weight, and then the water resistance of the self-leveling mortar is tested after soaking in water.

[0052] Table 1

[0053]

[0054] Table 2

[0055]

[0056]

[0057] According to JC / T698-2010 "Gypsum Block", the oven-dried test piece is taken out of the oven, and the oven-dry compressive strength of the test piece is measured after being lowered to room temperature. Then the test piece is soaked in water at 20°C for 1h, 24h, 48h and 96h respectively. After the corresponding time, the test piece is taken out of the water and the surface water is wiped off with a towel, and the wet compressive strength of the test piece is measured. The softening coefficient is the ratio of the wet compressive strength to the oven-dry compressive strength of the test piece with the same proportion and the same age.

[0058] As can be seen from Table 2, when the cement and mineral powder addition amount changes little, the softening coefficient of the phosphogypsum self-leveling mortar continuously increases with the increase of the content of the expanded graphite in the microcapsule. The 1h softening coefficient of Example 3 reaches 0.89. The 1h softening coefficient of Comparative Example 1 is reduced by 5.7% compared with Example 1, and the 1h softening coefficient of Comparative Example 2 is reduced by 19.5% compared with Example 2. Obviously, the addition of cement and mineral powder has a more obvious effect on improving the water resistance of the phosphogypsum self-leveling mortar. This is because, after the addition of cement and mineral powder, on the one hand, the internal voids of the gypsum are filled, and on the other hand, CSH gel and other hydraulic substances with more stable crystal form than gypsum are formed by hydration, thereby better improving the water resistance. The 1h softening coefficient of Comparative Example 3 is the lowest, indicating that the water resistance of the phosphogypsum self-leveling mortar is very limited without the addition of microcapsules, but only relying on inorganic admixtures and fibers. In addition, from the change trend of the 24h, 48h and 96h softening coefficients of Example 3 and Comparative Example 4, it can be seen that the 96h softening coefficient of Example 3 after the addition of microcapsules has little difference with the 48h softening coefficient, and can still reach 0.76, and only decreases by 2.6%. However, the 96h softening coefficient after the direct addition of an equal amount of expanded graphite powder is only 0.54, which is reduced by 16.9% compared with the 48h softening coefficient. This shows that the special sealing and controllable slow-release effect of the microcapsule significantly improves the long-acting water resistance of the phosphogypsum self-leveling mortar.

Claims

1. High water-resistant phosphogypsum self-leveling mortar, characterized in that The components are as follows in parts by weight: Phosphogypsum 80-90 parts, cement 2-5 parts, mineral powder 1-3 parts, ethyl cellulose 0.4-0.8 parts, nano-silica 6-8 parts, microcapsule 12-14 parts, water reducing agent 1.6-1.8 parts, defoaming agent 0.1-0.3 parts, retarder 0.08-0.12 parts, and water 26-30 parts; The preparation method of the microcapsule comprises the following steps: Dissolve 10-15 parts of gelatin in 10-12 parts of propylene glycol, heat to above 80°C; add 8-14 parts of expanded graphite, stir at a low speed of 100 r / min for 3 min, and then stir at a high speed of 3000 r / min for 10 min; cool to room temperature, separate the solid and the liquid, wash, and dry to obtain the microcapsule.

2. The high water resistant phosphogypsum self-leveling mortar according to claim 1, characterized in that The phosphogypsum is α-type phospho building gypsum with a pH value of 6-7 and an average particle size of 30-40 µm.

3. The highly water-resistant phosphogypsum self-leveling mortar according to claim 1, characterized in that The cement is ordinary Portland cement with a strength grade of 42.5; and the mineral powder is S95 grade mineral powder.

4. The high water resistant phosphogypsum self-leveling mortar according to claim 1, characterized in that The ethyl cellulose is in white powder form, viscosity 200 mpa.s, density 1.45 g / m 3 .

5. The high water resistant phosphogypsum self-leveling mortar according to claim 1, characterized in that The nano-silica is white powder with a particle size of 10-20 nm.

6. The highly water-resistant phosphogypsum self-leveling mortar according to claim 1, characterized in that The water reducing agent is polycarboxylic acid high-performance water reducing agent with a water-reducing rate of 28-30%; the defoaming agent is one of P803, A240, DEE FO 1015, and BYK-012 with a pH value of 5-7; and the retarder is degradable polyamide calcium salt.

7. The high water resistant phosphogypsum self-leveling mortar according to claim 1, characterized in that The gelatin is colorless granule, pH value 5.5-7, Brookfield viscosity 6.8 mpa.s, moisture content 5%, density 1.37 g / m 3 .

8. The high water resistant phosphogypsum self-leveling mortar according to claim 1, characterized in that The expanded graphite is in powder form with a carbon content of 95%-98%, an expansion ratio of 200-300 times, a pH value of 3-8, and a particle size of 0.2-0.3 mm.

9. Process for the preparation of the high water-resistant phosphogypsum self-levelling mortar according to any one of claims 1 to 8, characterized in that Comprise the following steps: (1) First, mix and stir the phosphogypsum, cement, mineral powder, and nano-silica to obtain uniform powder; dissolve the ethyl cellulose, water reducing agent, defoaming agent, and retarder in water to obtain a solution; (2) Mix and stir the obtained solution and the powder to obtain a flowable slurry; (3) Sprinkle the microcapsule on the surface of the slurry, and rely on gravity to sink into the slurry to obtain high-water-resistance phosphogypsum self-leveling mortar.

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