A waterproofing agent for desulfurized gypsum-based self-leveling mortar, its preparation method and uses

Abstract

The present invention discloses a waterproofing agent for desulfurized gypsum-based self-leveling mortar, its preparation method and uses. The waterproofing agent is an oil-in-water type silicone emulsion; the silicone raw materials are a mixture of polymethyltriethoxysilane and hydroxyl silicone oil in a mass ratio of 3 to 5:1; the emulsifier is a non-ionic composite emulsifier with a hydrophilic-lipophilic balance value (HLB) of 9 to 11. The preparation method is as follows: fully stir and mix polymethyltriethoxysilane and hydroxyl silicone oil evenly to obtain the silicone raw materials; add the non-ionic composite emulsifier to the silicone raw materials and stir and mix evenly to obtain the mixed raw materials; add water to the mixed raw materials while stirring, and continue stirring after the addition of water is completed. Its use is to prepare desulfurized gypsum-based self-leveling mortar using the above-mentioned waterproofing agent for desulfurized gypsum-based self-leveling mortar. The present invention can solve the technical problem that the existing desulfurized gypsum self-leveling mortar is limited in use due to poor water resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of waterproof agents. Specifically, it is a waterproof agent for desulfurized gypsum-based self-leveling mortar, its preparation method and uses. Background Technique

[0002] Desulfurized gypsum is an industrial by-product gypsum with high grade. Its main chemical components are the same as those of natural gypsum, both being calcium sulfate dihydrate. Currently, industries that produce desulfurized gypsum include power, heat production and supply industries, ferrous and non-ferrous metal smelting industries, chemical industries, paper-making industries, etc. Among them, the industry with the largest desulfurized gypsum output is the power, heat production and supply industry.

[0003] Applying desulfurized gypsum to self-leveling mortar has become an effective way to utilize desulfurized gypsum. Currently, desulfurized gypsum-based self-leveling mortar (SLF-FGD) has received extensive attention. There are already some enterprises in China engaged in the production of SLF-FGD and it has been applied in actual projects, and its application prospect is very broad. In 2020, the output of gypsum-based self-leveling mortar in China has reached more than 1 million tons. In northern China, floor heating is often used as a heating method, and SLF-FGD has become an excellent material for backfilling and leveling of floor heating, and can also be used as a leveling layer for floor slabs to facilitate the laying of decorative materials such as floor tiles and wooden floors on its surface. Compared with traditional fine aggregate concrete leveling layers and cement-based self-leveling materials, SLF-FGD has many advantages such as being less likely to produce hollowing and cracking, and having sound insulation and uniform heat transfer. However, gypsum belongs to air-hardening cementitious materials and has relatively poor water resistance, so its application range is limited to a certain extent. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to provide a waterproof agent for desulfurized gypsum-based self-leveling mortar, its preparation method and uses, so as to solve the technical problem that the existing desulfurized gypsum self-leveling mortar is limited due to poor water resistance during use.

[0005] To solve the above technical problems, the present invention provides the following technical solutions:

[0006] A waterproof agent for desulfurized gypsum-based self-leveling mortar is an oil-in-water type silicone emulsion; the silicone raw materials are a mixture of polymethyltriethoxysilane and hydroxy silicone oil in a mass ratio of 3 - 5:1; the emulsifier is a non-ionic composite emulsifier with a hydrophilic-lipophilic balance value HLB of 9 - 11. Ionic emulsifiers are sensitive to ions and pH in the environment and may cause a charge shielding effect, thereby affecting their emulsifying effect and increasing the instability of the emulsion; the non-ionic composite emulsifier with a hydrophilic-lipophilic balance value HLB of 9 - 11 used in the present invention not only has high compatibility and good stability, but the composite emulsifier formed by mixing two or more non-ionic emulsifiers has a better emulsifying effect on the silicone emulsion.

[0007] A preparation method of a waterproof agent for desulfurized gypsum-based self-leveling mortar, comprising the following steps:

[0008] Step (1): Stir and mix polymethyltriethoxysilane and hydroxy silicone oil thoroughly to obtain an organosilicon raw material; the mass ratio of polymethyltriethoxysilane to hydroxy silicone oil is 3-5:1;

[0009] Step (2): Add a non-ionic composite emulsifier to the organosilicon raw material, stir and mix evenly to obtain a mixed raw material; the hydrophilic-lipophilic balance value HLB of the non-ionic composite emulsifier is 9-11;

[0010] Step (3): Add water to the mixed raw material while stirring. After the water is added completely, continue to stir to obtain an oil-in-water type organosilicon emulsion, which is the waterproof agent for desulfurized gypsum-based self-leveling mortar.

[0011] In the above preparation method of the waterproof agent for desulfurized gypsum-based self-leveling mortar, in step (1), the mass ratio of polymethyltriethoxysilane to hydroxy silicone oil is 4:1; at this ratio, the waterproof agent for desulfurized gypsum-based self-leveling mortar prepared has the best waterproof effect. Increasing or decreasing the ratio of hydroxy silicone oil will lead to a decrease in the waterproof effect of the waterproof agent.

[0012] In the above preparation method of the waterproof agent for desulfurized gypsum-based self-leveling mortar, in step (1), the relative molecular weight of hydroxy silicone oil is 900-1800, and the viscosity is 50 cs (50 mm 2 / s); the kinematic viscosity of polymethyltriethoxysilane is 3-8 cs (3-8 mm 2 / s), the density is 0.920-0.995 kg / L, and pH>5.

[0013] In the above preparation method of the waterproof agent for desulfurized gypsum-based self-leveling mortar, in step (2), in the mixed raw material, the mass of the non-ionic composite emulsifier is 6-10 wt% of the mass of the organosilicon raw material; the hydrophilic-lipophilic balance value HLB of the non-ionic composite emulsifier is 10; the non-ionic composite emulsifier is composed of emulsifier A and emulsifier B. The hydrophilic-lipophilic balance value HLB of emulsifier A is 3-7, and the hydrophilic-lipophilic balance value HLB of emulsifier B is 12-16; the composite emulsifier formed by mixing these two non-ionic emulsifiers has a good emulsifying effect on the organosilicon raw material, and the formed emulsion has good stability. When the HLB value of the composite emulsifier is 10, the obtained emulsion has good stability. When the HLB value is greater than 10 or less than 10, the stability of the emulsified emulsion decreases and it is easy to delaminate.

[0014] For the preparation method of the above-mentioned desulfurized gypsum-based self-leveling mortar waterproofing agent, in step (2), among the mixed raw materials, the mass of the non-ionic composite emulsifier is 8 wt% of the mass of the organosilicon raw material; the non-ionic composite emulsifier consists of emulsifier OP-10 and Span-80 (or non-ionic composite emulsifiers such as OP-10 and Span-60, Tween-60 and Span-80, Tween-60 and Span-60 are selected. The waterproofing effects of the waterproofing agents emulsified by different non-ionic composite emulsifiers are somewhat different). When the dosage of the non-ionic composite emulsifier is too much, the emulsified emulsion particles are too small, the interfacial energy is too large, the emulsion is unstable, and a large amount of bubbles will be generated by the excessive emulsifier, which also has a certain impact on the emulsion; when the dosage is too little, the emulsion cannot be fully emulsified.

[0015] For the preparation method of the above-mentioned desulfurized gypsum-based self-leveling mortar waterproofing agent, in step (3), the stirring speed of the mixed raw materials is 1200 - 1800 r / min, and the water is added dropwise within 5 - 15 min; the continuous stirring time is 90 - 120 min; the mass ratio of the water addition amount to the mass of the organosilicon raw material is 1.5 - 2.5:1. When the stirring speed is too slow, the organosilicon is unevenly dispersed, not fully emulsified, and prone to stratification; when the stirring speed is too fast, the adsorption of the emulsifier is hindered, and there are too many collisions and aggregations between the small organosilicon droplets, reducing the stability of the emulsion. If the water addition speed is too fast, on the one hand, it may cause the emulsifier to not be fully dispersed in the water, emulsification is uneven, and emulsification is incomplete; on the other hand, it will generate high shear force, resulting in the aggregation of the emulsifier in the emulsion, particle damage or an increase in the particle size of the dispersed phase. If the water addition is too slow, it will lead to an extended emulsification time, the dispersed phase is prone to aggregating to form large particles, and the stability of the emulsion is reduced. If the continuous stirring time after adding water is too short, it will result in incomplete emulsification, there may be large particles or unstable regions in the emulsion, and even stratification may occur; if the continuous stirring time is too long, due to excessive shearing, the emulsifier will aggregate, the particles will be damaged or the particle size of the dispersed phase will increase.

[0016] For the preparation method of the above-mentioned desulfurized gypsum-based self-leveling mortar waterproofing agent, in step (3), the stirring speed of the mixed raw materials is 1500 r / min, and the water is added dropwise within 10 min; the continuous stirring time is 100 min; the mass ratio of the water addition amount to the mass of the organosilicon raw material is 2:1. Too much water addition significantly dilutes the oil phase, affecting the consistency of the emulsion; and too much water will cause the emulsion to stratify, reducing the stability. If the water addition amount is too little, it may lead to incomplete emulsification (the emulsifier cannot be fully dispersed in the water, emulsification is uneven), and the viscosity increases, affecting the use performance (too little water will increase the concentration of the oil phase, which may increase the viscosity of the emulsion); too little water enhances the interaction between the oil phase particles, reducing the stability of the emulsion.

[0017] Use of a waterproofing agent for desulfurized gypsum-based self-leveling mortar. Prepare desulfurized gypsum-based self-leveling mortar using the above-mentioned waterproofing agent for desulfurized gypsum-based self-leveling mortar. The desulfurized gypsum-based self-leveling mortar consists of 800 - 900 parts by weight of desulfurized gypsum, 40 - 55 parts by weight of cement, 80 - 110 parts by weight of heavy calcium powder, 10 - 20 parts by weight of the above-mentioned waterproofing agent for desulfurized gypsum-based self-leveling mortar, 2 - 5 parts by weight of water-reducing agent, 0.5 - 1 part by weight of water-retaining agent, 0.3 - 0.8 part by weight of defoaming agent, 0.2 - 0.5 part by weight of retarder, 5 - 10 parts by weight of latex powder, and 400 - 450 parts by weight of water.

[0018] Use of the above-mentioned waterproofing agent for desulfurized gypsum-based self-leveling mortar. The desulfurized gypsum-based self-leveling mortar consists of 850 parts by weight of desulfurized gypsum, 50 parts by weight of cement, 100 parts by weight of heavy calcium powder, 15 parts by weight of the above-mentioned waterproofing agent for desulfurized gypsum-based self-leveling mortar, 3 parts by weight of water-reducing agent, 0.8 part by weight of water-retaining agent, 0.6 part by weight of defoaming agent, 0.4 part by weight of retarder, 6 parts by weight of latex powder, and 440 parts by weight of water.

[0019] The technical solution of the present invention has achieved the following beneficial technical effects:

[0020] The waterproofing agent for desulfurized gypsum-based self-leveling mortar prepared by the preparation method of the present invention exists in the form of an oil-in-water type silicone emulsion, with good stability and not easy to stratify. Incorporating this waterproofing agent into the desulfurized gypsum-based self-leveling mortar can effectively extend the initial setting time and final setting time of the desulfurized gypsum-based self-leveling mortar. Compared with the desulfurized gypsum-based self-leveling mortar without incorporating this waterproofing agent, when the incorporation amount of this waterproofing agent is 1.5 wt%, it can increase its 28-day saturated flexural strength by about 33.3% and its 28-day saturated compressive strength by about 64.0%. And it can significantly reduce the bleeding rate of the desulfurized gypsum-based self-leveling mortar by about 55.7%, and its flexural softening coefficient and compressive softening coefficient are also significantly improved, increasing by 67.4% and 91.7% respectively. This shows that the waterproofing agent for desulfurized gypsum-based self-leveling mortar of the present invention can effectively improve the water resistance of the desulfurized gypsum-based self-leveling mortar. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the preparation process of the waterproofing agent for desulfurized gypsum-based self-leveling mortar in the embodiment of the present invention;

[0022] Figure 2a and Figure 2b is the flowability test diagram of the desulfurized gypsum-based self-leveling mortar in the embodiment of the present invention ( Figure 2a is a tool actual photo, Figure 2b is the actual photo of the specimen test);

[0023] Figure 3Actual picture of the Vicat apparatus used in the embodiments of the present invention;

[0024] Figure 4 Actual picture of the flexural and compressive strength testing apparatus in the embodiments of the present invention;

[0025] Figure 5 SEM image of the desulfurized gypsum-based self-leveling mortar at 28-day age in the embodiments of the present invention (the incorporation amount of the silicone waterproofing agent is 0%);

[0026] Figure 6 SEM image of the desulfurized gypsum-based self-leveling mortar at 28-day age in the embodiments of the present invention (the incorporation amount of the silicone waterproofing agent is 1.5 wt%);

[0027] Figure 7 Actual picture of the silicone waterproofing agent prepared in the embodiments of the present invention. Detailed implementation manners

[0028] 1. Desulfurized gypsum-based self-leveling mortar waterproofing agent and its preparation

[0029] The preparation method of the desulfurized gypsum-based self-leveling mortar waterproofing agent in this embodiment is as Figure 1 shown, and includes the following steps:

[0030] Step (1): Stir and mix polymethyltriethoxysilane and hydroxyl silicone oil evenly to obtain a silicone raw material; wherein, the mass ratio of polymethyltriethoxysilane to hydroxyl silicone oil is 4:1; the hydroxyl silicone oil, that is, dimethylhydroxyl silicone oil, has a relative molecular weight of 900 - 1800 and a viscosity of 50 cs (50 mm 2 / s); the kinematic viscosity of polymethyltriethoxysilane is 3 - 8 cs (3 - 8 mm 2 / s), the density is 0.920 - 0.995 kg / L, and the acid value pH > 5.

[0031] Step (2): Add a non-ionic composite emulsifier to the silicone raw material, stir and mix evenly to obtain a mixed raw material; the mass of the non-ionic composite emulsifier is 8 wt% of the mass of the silicone raw material; the hydrophilic-lipophilic balance value HLB of the non-ionic composite emulsifier is 10, and it is composed of the emulsifier dodecylphenol polyoxyethylene ether OP-10 and sorbitan fatty acid ester Span-80; the hydrophilic-lipophilic balance value HLB of the emulsifier OP-10 is 14.5, and the hydrophilic-lipophilic balance value HLB of Span-80 is 4.3;

[0032] According to formula (1), determine the mass ratio of the emulsifier OP-10 to Span-80 as 1:0.789.

[0033]

[0034] Step (3): Add water to the mixed raw materials while stirring. After the addition of water is completed, continue stirring to obtain an oil-in-water type silicone emulsion, which is the waterproofing agent for desulfurized gypsum-based self-leveling mortar. In this example, the stirring speed of the mixed raw materials is 1500 r / min, the water is added dropwise within 10 minutes, the continuous stirring time is 100 minutes, and the mass ratio of the added water to the silicone raw materials is 2:1.

[0035] The oil-in-water type (O / W) silicone emulsion prepared by the above method is milky white. As Figure 7 shown, the prepared silicone emulsion does not delaminate after standing for 96 hours and has good stability. When it is used as the waterproofing agent for desulfurized gypsum-based self-leveling mortar, it has a good waterproofing effect.

[0036] 2. Testing on the use of the waterproofing agent for desulfurized gypsum-based self-leveling mortar

[0037] In this example, the oil-in-water type silicone emulsion is prepared by the phase inversion method. Using silicone materials polymethyltriethoxysilane and hydroxyl silicone oil as raw materials, a composite emulsifier composed of OP-10 and Span-80 is mixed with the silicone raw materials, and an appropriate amount of water is added. After sufficient emulsification, a composite emulsion type waterproofing agent for desulfurized gypsum-based self-leveling mortar is prepared, hereinafter referred to as "silicone waterproofing agent" for short. This silicone waterproofing agent is incorporated into the desulfurized gypsum-based self-leveling mortar SLF-FGD to study its effects on the working performance, mechanical properties, and water resistance of SLF-FGD. Specifically as follows:

[0038] 2.1 Preparation of desulfurized gypsum-based self-leveling mortar

[0039] A homemade desulfurized gypsum-based self-leveling mortar waterproofing agent (also known as a "silicone waterproofing agent") was incorporated into a desulfurized gypsum-based self-leveling mortar (SLF-FGD) to study the effects of the "silicone waterproofing agent" on the performance of the desulfurized gypsum-based self-leveling mortar (SLF-FGD). The experimental formulations are shown in Table 1. The water-in-oil "silicone waterproofing agent" was incorporated into the desulfurized gypsum-based self-leveling mortar (SLF-FGD) at 0% and 1.5% by weight of the total mass of desulfurized gypsum, cement, and heavy calcium carbonate. The ratio of water added to the total mass of desulfurized gypsum, cement, and heavy calcium carbonate was 0.44. In Table 1, R0 represents the incorporation level of the silicone waterproofing agent at 0%, and R1.5 represents the incorporation level of the silicone waterproofing agent at 1.5% by weight. The incorporation level here refers to the incorporation level of the silicone waterproofing agent relative to the total mass of the desulfurized gypsum, cement, and heavy calcium carbonate. In this embodiment, the water reducer (polycarboxylate water reducer produced by Tianjin Weihe Technology Development Co., Ltd.), the water retaining agent (produced by Beijing Kelly Tianwei Science and Technology Trade Co., Ltd., with a viscosity of 400 MPa·s), the defoamer (801P defoamer produced by Beijing Jiahe Ruilian Technology Co., Ltd.), the retarder (HN302 gypsum retarder produced by Hebei Xietong Chemical Co., Ltd.), and the latex powder (produced by Jinzhou Baoyi Building Materials Technology Co., Ltd.) are all common commercial products for desulfurized gypsum-based self-leveling mortar; the cement is Jidong brand ordinary Portland cement with a designation of P.O.42.5.

[0040] Table 1 Test mix ratio of single-doped silicone waterproofing agent (g)

[0041]

[0042] The mass ratio of desulfurized gypsum, cement, and heavy calcium carbonate powder affects the water resistance and mechanical properties of self-leveling mortar. Adding 5% cement can leverage its hydraulic properties, improving mechanical and water resistance. However, excessive cement addition should be avoided, as it may cause cracking. Adding 10% heavy calcium carbonate powder improves the mortar's crack resistance. Heavy calcium carbonate has excellent filling properties, filling micropores and cracks in the mortar. However, adding too much can reduce the mortar's mechanical properties.

[0043] Adding an appropriate amount of water reducer can reduce water demand and improve the water resistance and mechanical properties of self-leveling mortar. If too little water reducer is added, the self-leveling mortar will have poor fluidity, requiring more water to meet fluidity requirements, which will reduce strength and water resistance. If too much water reducer is added, fluidity may not increase significantly, but segregation and bleeding may occur.

[0044] Water retention agents can delay the evaporation of water in mortar, prevent the surface of mortar from cracking, and improve the fluidity and plasticity of mortar. An appropriate amount of water retention agent can enhance the water resistance and mechanical properties of mortar. When the dosage of the water retention agent is too low: 1. It reduces the water retention performance of mortar, and the water in the mortar evaporates too quickly, so the surface of the mortar may crack. 2. It is not conducive to construction. The water retention agent can improve the fluidity and plasticity of mortar, and it is not conducive to construction when the dosage is too low. When the dosage of the water retention agent is too high: 1. It affects the development of strength. Excessive water retention agent will make the water in the mortar too much, delaying the hydration. 2. It is not conducive to setting and hardening. Excessive water retention agent makes the water in the mortar too much, prolonging the setting time of the mortar and extending the construction period.

[0045] Adding an appropriate amount of defoamer can improve the water resistance and mechanical properties of mortar. When the dosage of the defoamer is too low: There will be too many bubbles in the mortar, affecting the appearance, and the water resistance and mechanical properties will also decrease. Excessive defoamer will weaken the bonding force between mortar particles and reduce the mechanical properties.

[0046] The dosage of the retarder has a certain impact on the water resistance and mechanical properties of mortar. When the dosage of the retarder is too low, the setting time of the mortar will be too short to meet the requirements of the specification and construction. When the dosage of the retarder is too high, it will prolong the setting time and also cannot meet the requirements of construction, and will lead to a decrease in mechanical properties.

[0047] The dosage of the latex powder has an impact on the water resistance and mechanical properties of mortar. When the dosage of the latex powder is too low: The bonding property decreases, the flexibility of the mortar decreases, and cracking may occur. When the dosage of the latex powder is too high: The fluidity decreases. Excessive latex powder will increase the viscosity of the mortar.

[0048] In this embodiment, components such as water reducing agent, water retention agent, defoamer, retarder, and latex powder can play a synergistic role with the waterproof agent in improving the water resistance of mortar.

[0049] 2.2 Test methods for evaluating the properties of desulfurized gypsum-based self-leveling mortar

[0050] 2.2.1 Test of initial fluidity water rate and 30 min fluidity

[0051] According to the requirements in the standard "Gypsum Self-Leveling Mortar" (JC / T 1023-2021), weigh an appropriate amount of the sample and water, mix and stir the sample and water evenly, then pour it into a fluidity test mold with an inner diameter of 30 mm and a height of 50 mm. After scraping off the excess slurry in the test mold, lift the test mold vertically and let the slurry flow freely on the fluidity plate (a square glass plate with a side length not less than 30 cm). After the flow stops, measure the diameters in two mutually perpendicular directions and calculate the average value to make it within the range of 145 ± 5 mm, obtaining the initial fluidity. The ratio of the water consumption to the mass of the sample is the water consumption rate of the initial fluidity. Let the slurry stand for 30 min and then conduct appropriate stirring, and then measure its fluidity, which is the 30-min fluidity. The water consumption rate of the initial fluidity is calculated according to formula (2):

[0052]

[0053] In the formula: P—the water consumption rate of the initial fluidity (%); M1—the water consumption (g); M2—the mass of the sample (g).

[0054] 2.2.2 Determination of setting time

[0055] According to "Gypsum-Based Self-Leveling Mortar" (JC / T 1023-2007) and "Determination of Physical Properties of Building Gypsum Paste" (GB / T 17669.4-1999), weigh 300 g of the sample, mix it with the measured water and stir evenly, then pour it into the ring mold, and use a Vicat apparatus with a steel needle (as shown) to measure the setting time. Start timing from the moment when the sample and water are mixed. Make the steel needle contact the surface of the slurry and freely fall. The time elapsed when the steel needle does not touch the bottom for the first time is the initial setting time, and the time elapsed when the falling depth of the steel needle ≤ 1 mm is the final setting time. Figure 3 as shown

[0056] 2.2.3 Flexural and compressive strength tests

[0057] According to the requirements of the standard "Gypsum Self-Leveling Mortar" (JC / T 1023-2021), after the specimens are placed for 24 h under standard test conditions, remove the molds and test the 24-h flexural strength and compressive strength of one group of SLF-FGD. After the other group of specimens are placed for 28 d under standard test conditions, put them into an electrothermal blast drying oven at (40 ± 2) °C and dry them to a constant weight, and then test the 28-d absolute dry flexural strength and absolute dry compressive strength of the specimens.

[0058] 2.2.4 Water absorption test

[0059] After the test specimens reach 28 days of age, measure the masses of three test blocks of a group of specimens, then place them in water at (20±3)°C, take them out after soaking for 24 hours, dry the water on the surface, weigh the mass of the specimens after soaking, and the ratio of the mass of the specimens after soaking (m2) minus the mass of the specimens before soaking (m1) to the mass of the specimens before soaking (m1) is the water absorption rate of the specimens. The result is the arithmetic mean of the three test blocks. The water absorption rate (W) is calculated according to formula (3):

[0060]

[0061] In the formula: W—water absorption rate (%); m1—mass of the specimen before soaking (g); m2—mass of the specimen after soaking (g).

[0062] 2.2.5 Softening coefficient test

[0063] Referring to the test method of softening coefficient in the reference specification "Gypsum Blocks" (JC / T 698-2010), after placing the specimens at 28 days of age in water at (20±3)°C and soaking for 24 hours, take them out, dry the water on the surface of the test blocks, and then test their saturated flexural strength and compressive strength. The ratios of the saturated flexural and compressive strengths to the corresponding dry flexural and compressive strengths are the flexural softening coefficient and compressive softening coefficient respectively. The softening coefficient is determined according to formula (4):

[0064]

[0065] In the formula: f—flexural softening coefficient or compressive softening coefficient; R2—saturated flexural strength or saturated compressive strength (MPa); R3—dry flexural strength or dry compressive strength (MPa).

[0066] 2.3 Test results and analysis of desulfurized gypsum-based self-leveling mortar performance

[0067] 2.3.1 Macroscopic test results

[0068] Table 2 Test results of desulfurized gypsum-based self-leveling mortar performance

[0069]

[0070] The index requirements corresponding to grade G20 in the specification "Gypsum-based Self-leveling Mortar" JC / T1023-2021 are: 30min fluidity ≥ 140mm; 24h flexural strength ≥ 2.0MPa, 24h compressive strength ≥ 6.0MPa; 28d compressive strength in dry state ≥ 20.0MPa, 28d flexural strength in dry state ≥ 5.0MPa.

[0071] 2.3.2 SEM analysis

[0072] The SEM images of the desulfurized gypsum-based self-leveling mortar SLF-FGD specimens with single addition of silicone waterproof agent at 28 days of age are as follows Figure 5 and Figure 6 shown Figure 5 The specimen without silicone waterproof agent is shown. It can be seen that the gypsum crystals are mostly columnar, relatively regular, with distinct edges and corners, and there are also more pores Figure 6 The image shows the specimen with 1.5 wt% of silicone waterproof agent added. It can be seen from the figure that the gypsum crystals become irregular, the appearance becomes more rounded, the length of the crystals is shortened, and the number of plate-like crystals increases. This is because the polysiloxane film formed by the silicone waterproof agent wraps around the surface of the gypsum crystals, which has a certain impact on the hydration growth of the gypsum crystals. The contact points between the gypsum crystals are reduced, resulting in a certain decrease in the mechanical properties of the mortar

[0073] 3. Conclusions

[0074] (1) The silicone waterproof agent prepared by the preparation method of this embodiment has good stability and is not easy to delaminate

[0075] (2) Adding the silicone waterproof agent of this embodiment to the desulfurized gypsum-based self-leveling mortar SLF-FGD will increase the fluidity and setting time of the mortar. When the dosage of the silicone waterproof agent is 1.5 wt%, the initial fluidity and 30-minute fluidity are increased by about 15.6% and 13.1% respectively compared with the control group (the group with 0% dosage of the silicone waterproof agent). The initial setting time and final setting time are increased by about 34.4% and 62.9% respectively compared with the control group. The specification "Gypsum-based Self-leveling Mortar" JC / T 1023-2007 stipulates that the initial setting fluidity of the mortar shall not be less than 1 h and the final setting shall not exceed 6 h. The specification "Gypsum-based Self-leveling Mortar" JC / T 1023-2021 cancels this performance index requirement

[0076] (3) After adding the self-made silicone waterproof agent, the 24-hour strength and 28-day absolute dry strength of the desulfurized gypsum-based self-leveling mortar SLF-FGD are reduced to a certain extent. When the dosage is 1.5 wt%, the 24-hour flexural and compressive strengths are reduced by 21.4% and 14.7% respectively, and the 28-day absolute dry flexural and compressive strengths are reduced by 20.8% and 13.9% respectively; but its 28-day saturated water flexural and compressive strengths are increased by about 33.3% and 64.0% respectively

[0077] (4) Adding the silicone waterproof agent can significantly reduce the water absorption rate of the desulfurized gypsum-based self-leveling mortar SLF-FGD. When the dosage of the silicone waterproof agent is 1.5 wt%, the water absorption rate of the mortar is decreased by about 55.7% compared with the control group. When the dosage of the silicone waterproof agent is 1.5 wt%, the flexural softening coefficient and compressive softening coefficient of the mortar are increased by 67.4% and 91.7% respectively compared with the control group

[0078] (5) Silicone waterproofing agent can reduce the porosity of the desulfurized gypsum-based self-leveling mortar SLF-FGD. However, due to the air-entraining effect, the proportion of large pores increases. The silicone waterproofing agent can form a polysiloxane hydrophobic film on the surface of gypsum crystals and the pore walls, so that water is difficult to penetrate into the interior of the hardened body, and the water resistance is significantly increased.

Claims

1. A desulfurized gypsum-based self-leveling mortar waterproofing agent, characterized in that: It is an oil-in-water silicone emulsion; the silicone raw material is a mixture of polymethyltriethoxysilane and hydroxy silicone oil in a mass ratio of 3 to 5:1; the emulsifier is a non-ionic composite emulsifier with a hydrophilic-lipophilic balance value HLB of 9 to 11; the non-ionic composite emulsifier is composed of emulsifiers OP-10 and Span-80.

2. The method for preparing a desulfurized gypsum-based self-leveling mortar waterproofing agent according to claim 1, wherein: The steps include: Step (1) fully stirring and mixing polymethyltriethoxysilane and hydroxy silicone oil to obtain an organic silicon raw material; the mass ratio of polymethyltriethoxysilane to hydroxy silicone oil is 3 to 5:1; the relative molecular weight of the hydroxy silicone oil is 900 to 1800, and the viscosity is 50 cs; the kinematic viscosity of the polymethyltriethoxysilane is 3 to 8 cs, the density is 0.920 to 0.995 kg / L, and the pH is greater than 5; Step (2) adding a nonionic composite emulsifier to the organosilicon raw material, stirring and mixing uniformly to obtain a mixed raw material; the hydrophilic-lipophilic balance (HLB) value of the nonionic composite emulsifier is 9 to 11; in the mixed raw material, the mass of the nonionic composite emulsifier is 6 to 10 wt% of the mass of the organosilicon raw material; Step (3) adding water to the mixed raw materials while stirring, and continuing to stir after the water is added to obtain an oil-in-water type silicone emulsion, which is a desulfurized gypsum-based self-leveling mortar waterproofing agent.

3. The preparation method of the desulfurized gypsum-based self-leveling mortar waterproofing agent according to claim 2, characterized in that: In step (1), the mass ratio of polymethyltriethoxysilane to hydroxy silicone oil is 4:

1.

4. The method for preparing the desulfurized gypsum-based self-leveling mortar waterproofing agent according to claim 2, characterized in that: In step (2), the hydrophilic-lipophilic balance value HLB of the nonionic composite emulsifier is 10; the nonionic composite emulsifier is composed of emulsifier A and emulsifier B, the hydrophilic-lipophilic balance value HLB of emulsifier A is 3 to 7, and the hydrophilic-lipophilic balance value HLB of emulsifier B is 12 to 16.

5. The method for preparing the desulfurized gypsum-based self-leveling mortar waterproofing agent according to claim 4, characterized in that: In step (2), in the mixed raw materials, the mass of the nonionic composite emulsifier is 8 wt% of the mass of the organic silicon raw material.

6. The method for preparing the desulfurized gypsum-based self-leveling mortar waterproofing agent according to claim 2, characterized in that: In step (3), the stirring speed of the mixed raw materials is 1200-1800 r / min, and the water is added dropwise within 5-15 minutes; the stirring time is continued for 90-120 minutes; and the ratio of the amount of water added to the mass of the organic silicon raw material is 1.5-2.5:

1.

7. The method for preparing the desulfurized gypsum-based self-leveling mortar waterproofing agent according to claim 6, characterized in that: In step (3), the stirring speed of the mixed raw materials is 1500 r / min, and the water is added dropwise within 10 minutes; the stirring time is continued for 100 minutes; and the ratio of the amount of water added to the mass of the organic silicon raw material is 2:

1.

8. A use of a desulfurized gypsum-based self-leveling mortar waterproofing agent, characterized in that: Desulfurized gypsum-based self-leveling mortar waterproofing agent according to claim 1 is used to prepare desulfurized gypsum-based self-leveling mortar; the desulfurized gypsum-based self-leveling mortar is composed of 800-900 parts by weight of desulfurized gypsum, 40-55 parts by weight of cement, 80-110 parts by weight of heavy calcium powder, 10-20 parts by weight of the desulfurized gypsum-based self-leveling mortar waterproofing agent according to claim 1, 2-5 parts by weight of water reducer, 0.5-1 part by weight of water retaining agent, 0.3-0.8 part by weight of defoaming agent, 0.2-0.5 part by weight of retarder, 5-10 parts by weight of latex powder and 400-450 parts by weight of water.

9. The use of the desulfurized gypsum-based self-leveling mortar waterproofing agent according to claim 8, characterized in that: The desulfurized gypsum-based self-leveling mortar is composed of 850 parts by weight of desulfurized gypsum, 50 parts by weight of cement, 100 parts by weight of heavy calcium powder, 15 parts by weight of the desulfurized gypsum-based self-leveling mortar waterproofing agent as claimed in claim 1, 3 parts by weight of water reducer, 0.8 parts by weight of water retaining agent, 0.6 parts by weight of defoaming agent, 0.4 parts by weight of retarder, 6 parts by weight of latex powder and 440 parts by weight of water.

Images