Compact solid gypsum block produced from high-temperature gypsum and preparation method thereof

Abstract

The invention relates to a compact solid gypsum block produced from high-temperature gypsum and a preparation method thereof, and belongs to the technical field of building materials. The raw material formula of the compact solid gypsum block comprises the following components in parts by weight: 70-90 parts of CaSO4 II-E high-temperature gypsum; 10 to 15 parts of building gypsum; 0.5 to 2 parts of a sulfate activator; 1-4 parts of an alkaline activator; 0-20 parts of aggregate with the particle size less than or equal to 2mm; 0.2 to 0.5 part of a polycarboxylic acid type water reducing agent; 0.1 to 0.3 part of a retarder; and 0-1 part of an organosilicon waterproofing agent. The compact solid gypsum block disclosed by the invention is high in strength and good in water resistance.

Description

Technical Field

[0001] The invention relates to a dense solid gypsum building block produced by using high temperature gypsum and a preparation method thereof, belonging to the technical field of building materials. Background Art

[0002] Gypsum is one of the three traditional cementitious materials. Theoretically, dihydrate gypsum is calcined at 360℃~900℃ to produce type II anhydrous gypsum (CaSO4Ⅱ). Generally, high-temperature gypsum refers to high-temperature gypsum (CaSO4Ⅱ-E) produced at a calcination temperature exceeding 700℃~900℃. Natural gypsum and industrial by-product gypsum are the main raw materials for the production of high-temperature gypsum.

[0003] Types of industrial by-product gypsum include: phosphogypsum, desulfurized gypsum, titanium gypsum, fluorinated gypsum, mirabilite gypsum, citric acid gypsum, salt gypsum, boric gypsum, ceramic waste mold gypsum, waste gypsum board, tartaric acid gypsum, lactic acid gypsum and other organic acid gypsum, etc. Most of these industrial by-product gypsums can be used to produce high-temperature gypsum. The raw materials are widely available, cheap and environmentally friendly.

[0004] Dense solid gypsum blocks are widely used, especially in areas with high fire resistance requirements such as hospitals, schools, underground parking firewalls, industrial plant partitions, data centers, etc. However, there is currently no method for producing dense gypsum blocks using high temperature gypsum (CaSO4Ⅱ-E).

[0005] Patent CN1919781A discloses a gypsum block made of chemical gypsum and industrial waste and a preparation method thereof, which is a gypsum block with strong water resistance and good sound insulation made of chemical gypsum and industrial waste and a preparation method thereof. The special features of the invention are: the chemical gypsum is composed of two components, anhydrous gypsum with different hydration speeds and different crystal structures after hydration and semi-hydrated gypsum prepared by frying, the ratio of anhydrous gypsum to semi-hydrated gypsum is 2:1-3:1; the ratio of cement whose hydration process is a shrinkage process and anhydrous gypsum whose hydration process is a micro-expansion process is 1:12-1:3; the raw materials do not contain lightweight aggregates that reduce the bulk density of the product, and the raw materials are added with air entraining agents that can generate dispersed micro bubbles in the blocks. The invention makes use of a large amount of industrial waste, and the raw materials are cheap and available, which is waste-recycling, energy-saving and environmentally friendly. It overcomes the weakness of poor water resistance of traditional gypsum blocks, and has better strength, heat preservation, heat insulation and sound insulation performance. However, its strength and water resistance are still relatively low. Summary of the invention

[0006] A first object of the present invention is to provide a dense solid gypsum block produced using high temperature gypsum.

[0007] In order to achieve the above first object of the present invention, the raw material formula of the dense solid gypsum block includes by weight:

[0008] CaSO4Ⅱ-E high-temperature gypsum: 70 - 90 parts;

[0009] Building gypsum: 10 - 15 parts;

[0010] Sulfate activator: 0.5 - 2 parts;

[0011] Alkaline activator: 1 - 4 parts;

[0012] Aggregate with particle size ≤ 2mm: 0 - 20 parts;

[0013] Polycarboxylate superplasticizer: 0.2 - 0.5 parts;

[0014] Retarder: 0.1 - 0.3 parts;

[0015] Organosilicon waterproofing agent: 0 - 1 part.

[0016] The aggregate with particle size ≤ 2mm can be sand or quartz sand.

[0017] In a specific embodiment, the fineness of the CaSO4Ⅱ-E high-temperature gypsum is 80 - 150 mesh.

[0018] In a specific embodiment, the sulfate activator includes at least one of potassium sulfate and sodium sulfate; the alkaline activator includes at least one of lime and cement; the retarder includes at least one of citric acid and tartaric acid.

[0019] In a specific embodiment, the compressive strength of the dense solid gypsum block after 28 days of natural curing is ≥ 20MPa; the flexural strength is ≥ 6.0MPa; preferably, the compressive strength is ≥ 27MPa; the flexural strength is ≥ 8MPa.

[0020] In a specific embodiment, the density of the dense solid gypsum block is ≥ 1.8g / cm 3 ; the softening coefficient (Ks) is ≥ 0.68; preferably, there is no mass loss after 28 freeze-thaw cycles;

[0021] More preferably, the raw material formula of the dense solid gypsum block further includes 1 - 2 parts of organosilicon waterproofing agent by weight, and the softening coefficient Ks is above 0.8.

[0022] In a specific embodiment, the preparation method of the dense solid gypsum block includes:

[0023] a. Dry-mix the CaSO4Ⅱ-E high-temperature gypsum, building gypsum, and aggregate with particle size ≤ 2mm until uniform to obtain a mixed material A;

[0024] b. Add the mixed material A to an aqueous solution containing a superplasticizer, activator, organosilicon waterproofing agent, and retarder, and stir to form a homogeneous body;

[0025] c. The homogeneous body described in step b is formed by vibration pressing, and after forming, it is naturally cured: dried at room temperature for 7 days until the moisture content ≤ 5% to obtain a dense solid gypsum block.

[0026] In a specific embodiment, the dry mixing time in step a is 3 - 5 minutes; the stirring time in step c is preferably 2 - 3 minutes.

[0027] In a specific embodiment, the aqueous solution containing water reducing agent, activator and retarder in step b is: mixing dry materials with water, the addition amount of water is 20 - 30% of the mass of dry materials, and the dry materials are the sum of high-temperature gypsum, building gypsum, sulfate activator, alkaline activator, polycarboxylate water reducing agent and retarder.

[0028] In a specific embodiment, the vibration frequency of the vibration pressing forming in step c is 100 Hz, the amplitude is 0.8 mm, and the pressure ≥ 30 MPa.

[0029] The second object of the present invention is to provide a preparation method of the dense solid gypsum block produced by the above high-temperature gypsum.

[0030] To achieve the second object of the present invention, the preparation method of the dense solid gypsum block includes:

[0031] a. Dry mix CaSO4Ⅱ-E high-temperature gypsum, building gypsum, and aggregate with a particle size ≤ 2 mm until uniform to obtain a mixed material A;

[0032] b. Add the mixed material A to an aqueous solution containing water reducing agent, activator, silicone waterproofing agent and retarder, and stir to form a homogeneous body;

[0033] c. The homogeneous body described in step b is formed by vibration pressing, and after forming, it is naturally cured: dried at room temperature for 7 days until the moisture content ≤ 5% to obtain a dense solid gypsum block;

[0034] Preferably, the dry mixing time in step a is 3 - 5 minutes; the stirring time in step c is preferably 2 - 3 minutes;

[0035] Preferably, the aqueous solution containing water reducing agent, activator and retarder in step b is: mixing dry materials with water, the addition amount of water is 20 - 30% of the mass of dry materials, and the dry materials are the sum of high-temperature gypsum, building gypsum, sulfate activator, alkaline activator, polycarboxylate water reducing agent and retarder;

[0036] Preferably, the vibration frequency of the vibration pressing forming in step c is 100 Hz, the amplitude is 0.8 mm, and the pressure ≥ 30 MPa.

[0037] Beneficial effects:

[0038] The dense solid gypsum block of the present invention has high strength and good water resistance.

[0039] The dense solid gypsum block of the present invention has good comprehensive performance and is suitable for areas with high fire resistance requirements such as firewalls in hospitals, schools, super high-rise buildings, underground parking lots, partition walls in industrial factories, data centers, etc.; it is also suitable for load-bearing walls and basement walls; when used as a partition wall material, it also meets the requirements of strength and binder compatibility. Specific embodiments

[0040] To achieve the first above-mentioned object of the present invention, the raw material formula of the dense solid gypsum block includes, by weight:

[0041] CaSO4Ⅱ-E high-temperature gypsum: 70 - 90 parts;

[0042] Building gypsum: 10 - 15 parts;

[0043] Sulfate activator: 0.5 - 2 parts;

[0044] Alkaline activator: 1 - 4 parts;

[0045] Aggregate with a particle size ≤ 2mm: 0 - 20 parts;

[0046] Polycarboxylate superplasticizer: 0.2 - 0.5 parts;

[0047] Retarder: 0.1 - 0.3 parts;

[0048] Organosilicon waterproofing agent: 0 - 1 part.

[0049] The aggregate with a particle size ≤ 2mm can be sand or quartz sand.

[0050] In a specific embodiment, the fineness of the CaSO4Ⅱ-E high-temperature gypsum is 80 - 150 mesh.

[0051] In a specific embodiment, the sulfate activator includes at least one of potassium sulfate and sodium sulfate; the alkaline activator includes at least one of lime and cement; the retarder includes at least one of citric acid and tartaric acid.

[0052] In a specific embodiment, the compressive strength of the dense solid gypsum block after 28 days of natural curing ≥ 20MPa; the flexural strength ≥ 6.0MPa; preferably the compressive strength ≥ 27MPa; the flexural strength ≥ 8MPa.

[0053] In a specific embodiment, the density of the dense solid gypsum block ≥ 1.8g / cm 3 ; the softening coefficient (Ks) ≥ 0.68; preferably no mass loss after 28 freeze-thaw cycles;

[0054] More preferably, the raw material formula of the dense solid gypsum block further includes 1 to 2 parts of silicone waterproof agent by weight, and the softening coefficient Ks is above 0.8.

[0055] In a specific embodiment, the preparation method of the dense solid gypsum block includes:

[0056] a. Dry-mix CaSO4Ⅱ-E high-temperature gypsum, building gypsum, and aggregate with a particle size of ≤2 mm until uniform to obtain a mixed material A;

[0057] b. Add the mixed material A to an aqueous solution containing a water reducing agent, an activator, a silicone waterproof agent, and a retarder, and stir to form a homogeneous body;

[0058] c. Subject the homogeneous body in step b to vibration pressure molding, and after molding, perform natural curing: dry at room temperature for 7 days until the moisture content is ≤5% to obtain a dense solid gypsum block.

[0059] In a specific embodiment, the dry-mixing time in step a is 3 to 5 minutes; the stirring time in step c is preferably 2 to 3 minutes.

[0060] In a specific embodiment, the aqueous solution containing a water reducing agent, an activator, and a retarder in step b is: mix dry materials with water, and the addition amount of water is 20 to 30% of the mass of the dry materials, and the dry materials are the sum of high-temperature gypsum, building gypsum, sulfate activator, alkaline activator, polycarboxylate water reducing agent, and retarder.

[0061] In a specific embodiment, the vibration frequency of the vibration pressure molding in step c is 100 Hz, the amplitude is 0.8 mm, and the pressure is ≥30 MPa.

[0062] To achieve the second object of the present invention, the preparation method of the dense solid gypsum block includes:

[0063] a. Dry-mix CaSO4Ⅱ-E high-temperature gypsum, building gypsum, and aggregate with a particle size of ≤2 mm until uniform to obtain a mixed material A;

[0064] b. Add the mixed material A to an aqueous solution containing a water reducing agent, an activator, a silicone waterproof agent, and a retarder, and stir to form a homogeneous body;

[0065] c. Subject the homogeneous body in step b to vibration pressure molding, and after molding, perform natural curing: dry at room temperature for 7 days until the moisture content is ≤5% to obtain a dense solid gypsum block;

[0066] Preferably, the dry-mixing time in step a is 3 to 5 minutes; the stirring time in step c is preferably 2 to 3 minutes;

[0067] Preferably, the aqueous solution containing a water reducing agent, an activator, and a retarder in step b is prepared by mixing dry materials with water, where the amount of water added is 20-30% of the mass of the dry materials. The dry materials are the sum of high-temperature gypsum, building gypsum, sulfate activator, alkaline activator, polycarboxylate water reducing agent, and retarder.

[0068] Preferably, for the vibration pressing molding in step c, the vibration frequency is 100 Hz, the amplitude is 0.8 mm, and the pressure is ≥30 MPa.

[0069] The following describes the specific implementation manners of the present invention in conjunction with embodiments, and the present invention is not limited to the scope of the described embodiments.

[0070] Example 1

[0071] Dihydrate gypsum is calcined at 700-900 °C, rapidly cooled, and then modified and ground into high-temperature gypsum (CaSO4Ⅱ-E) with a fineness of 80-150 mesh. Weigh 84 parts of high-temperature gypsum (CaSO4Ⅱ-E), 12 parts of building gypsum, 0.8 part of potassium sulfate activator, add 1% silicone waterproofing agent, 1 part of lime, 2 parts of cement, and the addition amounts of polycarboxylate water reducing agent and citric acid are 0.25 part and 0.15 part respectively.

[0072] Dry mixing: Mix the high-temperature gypsum and building gypsum dry for 4 minutes until uniform.

[0073] Wet mixing: Add an aqueous solution containing a water reducing agent, an activator, and a retarder (water consumption: 26% of the dry materials), and stir for 3 minutes to form a homogeneous body.

[0074] The molding process is as follows:

[0075] Use vibration (frequency 100 Hz, amplitude 0.8 mm) to press at 30 MPa for molding, and use vibration to assist in exhausting air. The unit volume mass reaches ≥2.01.8 g / cm 3 (required by the GB / T 23451-2023 standard); after molding, carry out natural curing: dry at room temperature for 7 days until the moisture content ≤5%.

[0076] Measure after molding according to the aforementioned process formula, vibration pressing molding, and natural curing for a total of 28 days.

[0077] Reference standards: Requirements of GB / T 23451-2023 standard, EN 1795-1:2020 "Building Gypsum Products - Part 1: Classification, Specifications and Performance Requirements", GB8239-2014 "Ordinary Small Concrete Blocks", TCBMF36-2018 "Gypsum Blocks", GB 50204-2015 "Code for Acceptance of Construction Quality of Concrete Structures", Beijing DB11 / T 874-2012 "Technical Specification for Application of Building Gypsum Products", Shanghai JGJ / T 26-2015 "Technical Specification for Application of Building Gypsum in Shanghai". See Table 1 for reference performance indicators

[0078] Table 1 Reference Performance Indicators

[0079] Index Standard Requirements (Comprehensive Reference) Compressive Strength (28d) ≥20MPa Flexural Strength (28d) ≥6MPa Density <![CDATA[≥1.8g / cm 3 > Thermal Conductivity (28d) ≤0.18W / (m·K) Mass Loss of Frost Resistance (28 Freeze-Thaw Cycles) ≤5％ Shear Strength ≥0.7MPa Thermal Resistance Value (100mm) <![CDATA[≥0.22(m 2 ·K) / W]]>

[0080] After testing, the products of Examples 1-3 all meet the requirements of Table 1.

[0081] Example 2

[0082] Dihydrate gypsum is calcined at 700-900 °C, rapidly cooled, modified and ground into high-temperature gypsum (CaSO4Ⅱ-E) with a fineness of 80-150 mesh; 74 parts of high-temperature gypsum (CaSO4Ⅱ-E), 12 parts of building gypsum, 0.7 part of potassium sulfate activator, 1 part of lime, 2 parts of cement, 10 parts of sand are weighed, and the addition amounts of polycarboxylate-based water reducer and citric acid are 0.2 part and 0.1 part respectively. Press and form by vibration according to the foregoing process formula, and measure after natural curing for 28 days.

[0083] Example 3

[0084] Dihydrate gypsum is calcined at 700-900 °C, rapidly cooled, modified and ground into high-temperature gypsum (CaSO4Ⅱ-E) with a fineness of 80-150 mesh; 70 parts of high-temperature gypsum (CaSO4Ⅱ-E), 11 parts of building gypsum, 0.6 part of potassium sulfate activator, 1 part of lime, 2 parts of cement, 15 parts of sand are weighed, and the addition amounts of polycarboxylate-based water reducer and citric acid are 0.25 part and 0.15 part respectively. Press and form by vibration according to the foregoing process formula, and measure after natural curing for 28 days.

[0085] Comparative Example 1

[0086] The dihydrate gypsum is calcined at 700 - 900 °C, rapidly cooled, modified, ground into high-temperature gypsum (CaSO4Ⅱ-E), with a fineness of 80 - 150 mesh; weigh 84.4 parts of high-temperature gypsum (CaSO4Ⅱ-E), 12 parts of building gypsum, 0.4 part of potassium sulfate activator, 3 parts of alkaline activator (1 part of lime + 2 parts of cement), add 1% silicone waterproofing agent, 0.4 part of admixture (the addition amounts of polycarboxylate superplasticizer and citric acid are 0.25 part and 0.15 part respectively). Press and form by vibration according to the aforementioned process formula, and measure after natural curing for 28 days.

[0087] Comparative Example 2

[0088] The dihydrate gypsum is calcined at 700 - 900 °C, rapidly cooled, modified, ground into high-temperature gypsum (CaSO4Ⅱ-E), with a fineness of 80 - 150 mesh; weigh 74 parts of high-temperature gypsum (CaSO4Ⅱ-E), 7 parts of building gypsum, 0.7 part of potassium sulfate activator, 3 parts of alkaline activator (1 part of lime + 2 parts of cement), 15 parts of sand, 0.3 part of admixture (the addition amounts of polycarboxylate superplasticizer and citric acid are 0.2 part and 0.1 part respectively). Press and form by vibration according to the aforementioned process formula, and measure after natural curing for 28 days.

[0089] Comparative Example 3

[0090] The dihydrate gypsum is calcined at 700 - 900 °C, rapidly cooled, modified, ground into high-temperature gypsum (CaSO4Ⅱ-E), with a fineness of 80 - 150 mesh; weigh 60 parts of high-temperature gypsum (CaSO4Ⅱ-E), 21 parts of building gypsum, 15 parts of sand, 0.6 part of potassium sulfate activator, 3 parts of alkaline activator (1 part of lime + 2 parts of cement), 0.4 part of admixture (the addition amounts of polycarboxylate superplasticizer and citric acid are 0.25 part and 0.15 part respectively). Press and form by vibration according to the aforementioned process formula, and measure after natural curing for 28 days.

[0091] The measurement results of Examples 1 - 3 and Comparative Examples 1 - 3 are shown in Table 2 in detail.

[0092] Table 2 Experiment on Producing Dense Solid Gypsum Blocks with High-temperature Gypsum

[0093]

Claims

1. A dense solid gypsum block produced from high-temperature gypsum, characterized in that, The raw material formula of the dense solid gypsum block includes, by weight: CaSO4Ⅱ-E high-temperature gypsum: 70 - 90 parts; Building gypsum: 10 - 15 parts; Sulfate activator: 0.5 - 2 parts; Alkaline activator: 1 - 4 parts; Aggregate with a particle size ≤ 2mm: 0 - 20 parts; Polycarboxylate superplasticizer: 0.2 - 0.5 parts; Retarder: 0.1 - 0.3 parts; Organosilicon waterproofing agent: 0 - 1 part.

2. The dense solid gypsum block produced with high-temperature gypsum according to claim 1, characterized in that, The fineness of the CaSO4Ⅱ-E high-temperature gypsum is 80 - 150 mesh.

3. The dense solid gypsum block produced with high-temperature gypsum according to claim 1 or 2, characterized in that, The sulfate activator includes at least one of potassium sulfate and sodium sulfate; the alkaline activator includes at least one of lime and cement; the retarder includes at least one of citric acid and tartaric acid.

4. The dense solid gypsum block produced with high-temperature gypsum according to claim 1 or 2, characterized in that, The compressive strength of the dense solid gypsum block after 28 days of natural curing is ≥ 20 MPa; the flexural strength is ≥ 6.0 MPa; preferably, the compressive strength is ≥ 27 MPa; the flexural strength is ≥ 8 MPa.

5. The dense solid gypsum block produced with high-temperature gypsum according to claim 1 or 2, characterized in that, The density of the dense solid gypsum block ≥ 1.8 g / cm 3 ; the softening coefficient Ks ≥ 0.68; preferably, there is no mass loss after 28 freeze-thaw cycles; More preferably, the raw material formula of the dense solid gypsum block further includes 1 - 2 parts of organosilicon waterproofing agent by weight, and the softening coefficient Ks is above 0.

8.

6. The dense solid gypsum block produced with high-temperature gypsum according to claim 1 or 2, characterized in that, The preparation method of the dense solid gypsum block includes: a. Dry-mix the CaSO4Ⅱ-E high-temperature gypsum, building gypsum, and aggregate with a particle size ≤ 2mm until uniform to obtain a mixed material A; b. Add the mixed material A to an aqueous solution containing a superplasticizer, activator, organosilicon waterproofing agent, and retarder, and stir to form a homogeneous body; c. Subject the homogeneous body obtained in step b to vibration pressure molding, and after molding, perform natural curing: dry at room temperature for 7 days until the moisture content ≤ 5% to obtain a dense solid gypsum block.

7. The dense solid gypsum block produced with high-temperature gypsum according to claim 6, characterized in that, The dry-mixing time in step a is 3 - 5 minutes; the stirring time in step c is preferably 2 - 3 minutes.

8. The dense solid gypsum block produced with high-temperature gypsum according to claim 6, characterized in that, The aqueous solution containing a superplasticizer, activator, and retarder in step b is: mix the dry materials with water, and the addition amount of water is 20 - 30% of the mass of the dry materials. The dry materials are the sum of high-temperature gypsum, building gypsum, sulfate activator, alkaline activator, polycarboxylate superplasticizer, and retarder.

9. The dense solid gypsum block produced with high-temperature gypsum according to claim 6, characterized in that, The vibration frequency of the vibration pressure molding in step c is 100 Hz, the amplitude is 0.8 mm, and the pressure is ≥ 30 MPa.

10. The preparation method of the dense solid gypsum block produced with high-temperature gypsum as described in any one of claims 1 to 9, characterized in that, The preparation method of the dense solid gypsum block includes: a. Dry-mix the CaSO4Ⅱ-E high-temperature gypsum, building gypsum, and aggregate with a particle size ≤ 2mm until uniform to obtain a mixed material A; b. Add the mixed material A to an aqueous solution containing a superplasticizer, activator, organosilicon waterproofing agent, and retarder, and stir to form a homogeneous body; c. Subject the homogeneous body obtained in step b to vibration pressure molding, and after molding, perform natural curing: dry at room temperature for 7 days until the moisture content ≤ 5% to obtain a dense solid gypsum block; Preferably, the dry-mixing time in step a is 3 - 5 minutes; the stirring time in step c is preferably 2 - 3 minutes; Preferably, the aqueous solution containing a superplasticizer, activator, and retarder in step b is: mix the dry materials with water, and the addition amount of water is 20 - 30% of the mass of the dry materials. The dry materials are the sum of high-temperature gypsum, building gypsum, sulfate activator, alkaline activator, polycarboxylate superplasticizer, and retarder; Preferably, the vibration frequency of the vibration-assisted pressing forming in step c is 100 Hz, the amplitude is 0.8 mm, and the pressure is ≥30 MPa.

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