An ultra-early-strength phosphogypsum self-leveling mortar

Abstract

The application discloses a kind of super early-strength phosphogypsum self-leveling mortar, including water and powder, powder is composed of the following weight parts of raw materials: phosphorus building gypsum 1280~1300 parts, silica powder 0~13 parts, water reducing agent 2.25~7.0 parts, retarder 2.5~3.5 parts, defoaming agent 0.4~0.52 parts, cellulose ether 0.30~0.45 parts, thixotropic agent 0.3~0.4 parts, grey calcium 0~30 parts, by high dosage phosphorus building gypsum, its mass content is greater than 96%, can be a large amount of phosphogypsum, improve the disposal of phosphogypsum, beneficial to waste resource comprehensive utilization, reduce carbon emissions. The obtained phosphogypsum self-leveling mortar, 1d compressive strength is greater than or equal to 20MPa, its mortar water content is low, early strength is high, can realize continuous construction, save the overall construction time of project, reduce construction cost. At the same time, through low water-binder ratio, mortar internal density, under the premise of not internal doping waterproof agent, softening coefficient is greater than or equal to 0.6.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to an ultra-early strength phosphogypsum self-leveling mortar. Background Technology

[0002] Gypsum-based self-leveling mortar is composed of gypsum cementitious materials, aggregates, and chemical additives. It is a dry-mixed mortar material specifically used for floor leveling, which is mixed with water on-site. It has advantages such as convenient construction, thermal insulation, and sound insulation. Currently, the gypsum cementitious materials in gypsum-based leveling mortar mainly consist of α-type high-strength gypsum, β-type building gypsum, and Type II anhydrous gypsum, either alone or in combination.

[0003] Chinese invention patent with publication number CN114163204A discloses a sand-free gypsum-based self-leveling mortar and its preparation method. It uses β-type desulfurized building gypsum as the cementing material and stone powder to replace river sand to prepare a self-leveling mortar with a 28-day compressive strength of 20-25 MPa.

[0004] Chinese invention patent with publication number CN116789432A discloses a self-leveling mortar based on building gypsum and its preparation method. It is prepared by using β-type desulfurized building gypsum or phosphorus building gypsum, supplemented with ordinary silicate cement or lime, microsilica powder and chemical admixtures, and has an oven-dry strength of 22.3-28.7 MPa in 28 days.

[0005] Chinese invention patent CN116621555A discloses a method for preparing self-leveling mortar using phosphorus type II anhydrous gypsum. The method uses phosphorus type II anhydrous gypsum as raw material, adds fly ash to improve its fluidity, and adds plasticizer, surfactant, water-reducing agent, retarder and defoamer. Sulfate is used as a co-activator to prepare the self-leveling mortar precursor. After adding water and stirring thoroughly, the self-leveling mortar is obtained. The 28-day oven-dry compressive strength is ≥20.0 MPa.

[0006] Chinese invention patent CN116409980A discloses a fluorogypsum self-leveling mortar and its preparation method. The mortar is prepared by mixing fluorogypsum, α-type high-strength gypsum and building gypsum as cementing materials, and has a 1-day compressive strength ≥6.0MPa and a 28-day oven-dry compressive strength ≥30.0MPa.

[0007] Chinese invention patent with publication number CN113372081A discloses a high-strength phosphogypsum-based self-leveling mortar, which is prepared by using phosphogypsum and cement as cementing materials to produce a self-leveling mortar with an oven-dry compressive strength ≥20.0MPa.

[0008] Chinese invention patent CN108129122A discloses a method for preparing a phosphorus-based lightweight self-leveling mortar. The composition and mass percentage of this self-leveling mortar are as follows: phosphorus-based building gypsum 70%–90%, dried sand 0%–20%, cement 0%–20%, fly ash 0%–5%, lightweight aggregate 5%–20%, active activator 0%–15%, water repellent 0%–3%, high-performance plasticizer 0.1%–1%, anti-settling agent 0%–0.2%, flocculant 0%–0.2%, gypsum retarder 0.01%–0.4%, polymer 0%–3%, and high-performance defoamer 0.05%–0.3%. The lightweight self-leveling mortar prepared by this invention has a bulk density ≤1000 kg / m³. 3 Compressive strength ≥10MPa.

[0009] Phosphate-based building gypsum has a more complex composition, and its product performance fluctuates more significantly compared to building gypsum prepared from other industrial gypsums such as desulfurized gypsum, fluorogypsum, or salt gypsum. Therefore, its application in self-leveling mortars is relatively low. In the disclosed gypsum-based self-leveling mortar patents, the gypsum-based cementitious materials mostly employ a mixture or combination of Type II anhydrous gypsum or Type β building gypsum and Type α high-strength gypsum. However, due to their production methods, the energy consumption for producing Type α high-strength gypsum and Type II anhydrous gypsum is generally higher than that for Type β building gypsum. Therefore, the overall energy consumption of these self-leveling mortars is generally higher than that of phosphate-based building gypsum-based self-leveling mortars. Furthermore, current gypsum-based self-leveling mortars have a high water content, generally between 30-35%, resulting in low early strength and affecting subsequent floor surface construction. Moreover, existing ordinary gypsum-based self-leveling mortars have low waterproofing performance, while existing waterproof gypsum-based self-leveling mortars rely mainly on the addition of waterproofing agents to enhance waterproofing performance, leading to higher material costs. Summary of the Invention

[0010] To address the aforementioned problems, this invention aims to provide an ultra-early strength phosphogypsum self-leveling mortar.

[0011] To achieve the above objectives, the present invention adopts the following technical solution: an ultra-early-strength phosphogypsum self-leveling mortar, comprising water and powder, wherein the powder is composed of the following raw materials in parts by weight: 1280-1300 parts of phosphogypsum, 0-13 parts of silica fume, 2.25-7.0 parts of water-reducing agent, 2.5-3.5 parts of retarder, 0.4-0.52 parts of defoamer, 0.30-0.45 parts of cellulose ether, 0.3-0.4 parts of thixotropic agent, and 0-30 parts of lime, wherein the phosphogypsum accounts for more than 96% of the mass of the powder.

[0012] The pH value of the phosphogypsum self-leveling mortar system controlled by the gray calcium is between 7.0 and 9.0, and the silica powder has a lubricating effect on the phosphogypsum self-leveling mortar system.

[0013] Preferably, the water-reducing agent is an ultra-high performance polycarboxylate water-reducing agent with a water reduction rate greater than 50%; the water is tap water, with a weight of 350-450 parts.

[0014] Preferably, the performance of the phosphorus-containing building gypsum product meets the performance requirements of grade 3.0 in GB / T9776-2022 "Building Gypsum".

[0015] Preferably, the silicon powder is ultrafine silicon powder with a fineness of D50 of 2000-3000 mesh and D90 of 800-1000 mesh.

[0016] Preferably, the retarder is a collagen-based retarder with a retarding time greater than 60 minutes and a strength loss rate of less than 20%.

[0017] Preferably, the defoamer is a polyether-modified polydimethylsiloxane defoamer.

[0018] Preferably, the cellulose ether is hydroxypropyl methylcellulose with a viscosity of 5000-20000 mPa·s.

[0019] Preferably, the thixotropic agent is a magnesium aluminum silicate thixotropic agent.

[0020] Preferably, the CaO content in the ash calcium is greater than 90% by mass.

[0021] Preferably, the ultra-early strength phosphogypsum self-leveling mortar has a 1-day flexural strength greater than or equal to 3.5 MPa, a 1-day compressive strength greater than or equal to 20 MPa, a 28-day oven-dry flexural strength greater than or equal to 9 MPa, a 28-day oven-dry compressive strength greater than or equal to 40 MPa, a kiln-dried tensile bond strength greater than or equal to 1 MPa, and a softening coefficient greater than or equal to 0.6.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] 1. This invention utilizes high-phosphorus building gypsum with a mass content greater than 96%, which can absorb large quantities of phosphogypsum, improve the disposal of phosphogypsum, facilitate the comprehensive utilization of waste resources, benefit the ecological environment, and at the same time help reduce the amount of cement and α-type high-strength gypsum used, thereby reducing carbon emissions.

[0024] 2. Phosphate-containing building gypsum contains impurities such as phosphorus and fluorine, resulting in significant fluctuations in product quality. Preliminary experimental results indicate that the pH level in phosphate-containing building gypsum has a substantial impact on the water-reducing rate of polycarboxylate superplasticizers. An acidic environment significantly reduces the water-reducing rate of polycarboxylate superplasticizers, while excessively high pH values ​​decrease the strength of phosphate-containing building gypsum materials. Therefore, by strictly controlling the pH value of the phosphate-containing self-leveling mortar system between 7.0 and 9.0 using lime, the performance of polycarboxylate superplasticizers in the phosphate-containing self-leveling mortar is ensured, significantly reducing the water consumption of the phosphate-containing self-leveling mortar and improving its strength.

[0025] 3. By adding ultrafine silica powder, the ultrafine silica powder plays a "microsphere" effect in the phosphogypsum self-leveling mortar slurry, which lubricates the slurry, further reduces the water consumption of the slurry, and fills the gaps between crystals in the hardened slurry, thereby enhancing the early 28-day strength of the phosphogypsum self-leveling mortar.

[0026] 4. The leveling mortar prepared by this formula has high early strength, with a 1-day compressive strength greater than or equal to 20 MPa and a 28-day oven-dry compressive strength greater than or equal to 40 MPa. Furthermore, the use of ultra-high-performance polycarboxylate superplasticizer results in low moisture content in the mortar, enabling continuous construction and saving overall project construction time and reducing construction costs. Simultaneously, the low water-cement ratio ensures a dense internal structure, achieving a softening coefficient greater than or equal to 0.6 without the addition of waterproofing agents. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the specific embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram obtained by scanning electron microscopy of the ultra-early-strength phosphogypsum self-leveling mortar prepared in Example 1 of this invention. Figure 1 ;

[0029] Figure 2 This is a schematic diagram obtained by scanning electron microscopy of the ultra-early-strength phosphogypsum self-leveling mortar prepared in Example 1 of this invention. Figure 2 ;

[0030] Figure 3 This is a schematic diagram obtained by scanning electron microscopy of the ultra-early strength phosphogypsum self-leveling mortar prepared in Example 2 of this invention. Figure 1 ;

[0031] Figure 4 This is a schematic diagram obtained by scanning electron microscopy of the ultra-early strength phosphogypsum self-leveling mortar prepared in Example 2 of this invention. Figure 2 . Detailed Implementation

[0032] The present invention will be further described below through specific embodiments, but it should not be construed that the scope of the subject matter of the present invention is limited to the following embodiments. All modifications, substitutions and alterations made based on ordinary technical knowledge and common practices in the art without departing from the above-described technical concept of the present invention are included within the scope of the present invention.

[0033] An ultra-early-strength phosphogypsum self-leveling mortar comprises water and powder. The water is in the form of 350-450 parts by weight, and the powder is composed of the following raw materials in the indicated weight parts: (See table below for details.)

[0034]

[0035] The gypsum is phosphorus-based building gypsum, and its performance meets the 3.0 grade performance requirements in GB / T9776-2022 "Building Gypsum".

[0036] The silica powder is ultrafine silica powder with a fineness of D50 of 2000-3000 mesh and D90 of 800-1000 mesh. The ultrafine silica powder plays a "microsphere" effect in the phosphogypsum self-leveling mortar slurry, which lubricates the slurry, improves the fluidity of the self-leveling mortar, further reduces the water consumption of the slurry, and fills the intercrystalline gaps in the hardened slurry, thereby enhancing the early 28-day strength of the phosphogypsum self-leveling mortar.

[0037] The water-reducing agent is an ultra-high performance polycarboxylate water-reducing agent with a water reduction rate of over 50%. The water reduction rate specifically refers to its application in phosphorus-based building gypsum, used to reduce water consumption in mortar and improve mortar strength. The water reduction rate test method refers to GB / T 17669.4-1999, "Determination of Physical Properties of Building Gypsum Paste," calculating the water reduction rate based on the water consumption required for the paste to expand to a diameter of 180±5 mm.

[0038] The retarder is a collagen-based retarder with a retarding time of more than 60 minutes and a strength loss rate of less than 20%. It is used to extend the workability of mortar. This retarder specifically refers to the retarder used in phosphorus-based building gypsum.

[0039] The water in question is tap water.

[0040] The defoamer is a polyether-modified polydimethylsiloxane defoamer, used to eliminate foam and increase the smoothness and flatness of the mortar surface.

[0041] The cellulose ether is a hydroxypropyl methylcellulose with a viscosity of 5000-20000 mPa·s, used for water retention and thickening.

[0042] The thixotropic agent is a magnesium aluminum silicate thixotropic agent, used to improve the fluidity of mortar.

[0043] The lime-calcium has a CaO content of over 90% and is used to adjust the pH of the mortar system, improving the compatibility of the water-reducing agent and retarder in the mortar system. The pH in phosphogypsum has a significant impact on the water-reducing rate of polycarboxylate superplasticizers. An acidic environment will significantly reduce the water-reducing rate of polycarboxylate superplasticizers, while an excessively high pH value will reduce the strength of phosphogypsum materials. Therefore, by strictly controlling the pH value of the phosphogypsum self-leveling mortar system between 7.0 and 9.0 using lime-calcium, the performance of polycarboxylate superplasticizers in phosphogypsum self-leveling mortar is guaranteed, significantly reducing the water consumption of phosphogypsum self-leveling mortar and improving its strength.

[0044] The above materials are mixed evenly in a mixer to obtain ultra-early strength phosphogypsum self-leveling mortar powder. Ultra-early strength phosphogypsum self-leveling mortar can be prepared by mixing it with 350-450 parts of water in a high-speed mixer for 3-5 minutes.

[0045] The properties of the obtained ultra-early strength phosphogypsum self-leveling mortar are shown in the table below:

[0046]

[0047] Example 1: An ultra-early-strength phosphogypsum self-leveling mortar, comprising 1300 parts phosphogypsum, 5 parts silica fume, 4.5 parts water-reducing agent, 3.5 parts retarder, 0.52 parts defoamer, 0.4 parts cellulose ether, 0.32 parts thixotropic agent, and 20 parts lime. The above materials are mixed evenly in a mixer to obtain ultra-early-strength phosphogypsum self-leveling mortar powder. This powder is then mixed with 350 parts water in a high-speed mixer for 3-5 minutes to prepare the ultra-early-strength phosphogypsum self-leveling mortar. The prepared ultra-early-strength phosphogypsum self-leveling mortar is observed and analyzed using a scanning electron microscope, referring to... Figure 1 and Figure 2 The resulting product has a dense surface structure and excellent waterproof performance. The properties of this ultra-early-strength phosphogypsum self-leveling mortar are shown in the table below:

[0048]

[0049]

[0050] Example 2: An ultra-early-strength phosphogypsum self-leveling mortar, comprising 1290 parts phosphogypsum, 10 parts silica fume, 6.5 parts water-reducing agent, 3.5 parts retarder, 0.42 parts defoamer, 0.4 parts cellulose ether, 0.31 parts thixotropic agent, and 25 parts lime. The above materials are mixed evenly in a mixer to obtain ultra-early-strength phosphogypsum self-leveling mortar powder. This powder is then mixed with 300 parts water in a high-speed mixer for 3-5 minutes to prepare the ultra-early-strength phosphogypsum self-leveling mortar. The prepared ultra-early-strength phosphogypsum self-leveling mortar is observed and analyzed using a scanning electron microscope, referring to... Figure 3 and Figure 4This results in a product with a dense surface structure and excellent waterproof performance. The properties of this ultra-early-strength phosphogypsum self-leveling mortar are shown in the table below:

[0051]

[0052] The above provides a detailed description of the ultra-early-strength phosphogypsum self-leveling mortar provided by the present invention. Specific examples have been used to illustrate the structure and working principle of the invention. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A self-leveling mortar made of ultra-early-strength phosphogypsum, characterized in that: The product includes water and powder. The powder is composed of the following raw materials in parts by weight: 1280-1300 parts of phosphate building gypsum, 5-10 parts of silica fume, 2.25-7.0 parts of water-reducing agent, 2.5-3.5 parts of retarder, 0.4-0.52 parts of defoamer, 0.30-0.45 parts of cellulose ether, 0.3-0.4 parts of thixotropic agent, and 0-30 parts of lime. The phosphate building gypsum accounts for more than 96% of the powder by weight. The pH value of the phosphogypsum self-leveling mortar system controlled by the gray calcium is between 7.0 and 9.0, and the silica powder has a lubricating effect on the phosphogypsum self-leveling mortar system. The silicon powder is ultrafine silicon powder with a fineness of D50 of 2000-3000 mesh and D90 of 800-1000 mesh. The CaO content in the lime is greater than 90%.

2. The ultra-early strength phosphogypsum self-leveling mortar according to claim 1, characterized in that: The water-reducing agent is an ultra-high performance polycarboxylate water-reducing agent with a water reduction rate of more than 50%; the water is tap water with a weight of 350-450 parts.

3. The ultra-early strength phosphogypsum self-leveling mortar according to claim 1, characterized in that: The performance of the phosphorus-containing building gypsum product meets the performance requirements of grade 3.0 in GB / T9776-2022 "Building Gypsum".

4. The ultra-early strength phosphogypsum self-leveling mortar according to claim 1, characterized in that: The retarder is a collagen-based retarder with a retarding time of more than 60 minutes and a strength loss rate of less than 20%.

5. The ultra-early strength phosphogypsum self-leveling mortar according to claim 1, characterized in that: The defoamer is a polyether-modified polydimethylsiloxane defoamer.

6. The ultra-early strength phosphogypsum self-leveling mortar according to claim 1, characterized in that: The cellulose ether is hydroxypropyl methylcellulose with a viscosity of 5000-20000 mPa·s.

7. The ultra-early strength phosphogypsum self-leveling mortar according to claim 1, characterized in that: The thixotropic agent is magnesium aluminum silicate thixotropic agent.

8. The ultra-early strength phosphogypsum self-leveling mortar according to claim 1, characterized in that: The ultra-early strength phosphogypsum self-leveling mortar has a 1-day flexural strength greater than or equal to 3.5 MPa, a 1-day compressive strength greater than or equal to 20 MPa, a 28-day oven-dry flexural strength greater than or equal to 9 MPa, a 28-day oven-dry compressive strength greater than or equal to 40 MPa, a kiln-dried tensile bond strength greater than or equal to 1 MPa, and a softening coefficient greater than or equal to 0.6.

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