CN115536292A

CN115536292A - Phosphorus building gypsum-based super-sulfate cement and preparation method thereof

Info

Publication number: CN115536292A
Application number: CN202211220463.XA
Authority: CN
Inventors: 廖宜顺; 李豪; 刘艳玲; 陈迎雪; 张天潇
Original assignee: Wuhan University of Science and Engineering WUSE
Current assignee: Wuhan University of Science and Engineering WUSE
Priority date: 2022-09-28
Filing date: 2022-09-28
Publication date: 2022-12-30

Abstract

The invention discloses a phosphorus building gypsum-based super-sulfate cement and a preparation method thereof. The super-sulfate cement comprises the following components in percentage by mass: 0-20 percent of phosphorus building gypsum, 70-95 percent of superfine slag powder and 5-10 percent of hydrated lime. The cement greatly utilizes the industrial waste residue phosphorus building gypsum and the slag, simultaneously improves the compressive strength of the material, and reduces the adverse effect caused by the self-shrinkage of the cement.

Description

Phosphorus building gypsum-based super-sulfate cement and preparation method thereof

Technical Field

The invention belongs to the technical field of novel cementing materials, and particularly relates to super-sulfate cement and a preparation method thereof.

Background

The phosphogypsum is industrial waste residue generated in the wet-process production of phosphoric acid by taking phosphate ore as a raw material, about 5 tons of phosphogypsum can be generated every 1 ton of phosphoric acid, and the main component of the phosphogypsum is calcium sulfate dihydrate. The super-sulfate cement prepared by utilizing the phosphorus building gypsum, the superfine slag powder and the hydrated lime not only can solve the problem of environmental pollution caused by industrial waste slag, but also can solve the problem of environmental pollution caused by industrial waste slagAnd the emission of carbon dioxide is reduced. Because the production process of the super-sulfate cement does not need high-temperature calcination, the energy consumption and CO are reduced ₂ The amount of discharge of (c). Compared with silicate cement, the super-sulfate cement has the advantages of low hydration heat, excellent chloride ion and sulfate (magnesium sulfate removal) corrosion resistance and the like.

Disclosure of Invention

The invention provides a preparation method of super-sulfate cement, aiming at solving the environmental pollution caused by a large amount of industrial waste residue phosphorus building gypsum and improving the current situation that the early-stage compressive strength of the super-sulfate cement is lower. The technical scheme provided by the invention is as follows:

the early high compressive strength type super-sulfate cement comprises the following components in percentage by mass: 0-20 percent of phosphorus building gypsum, 70-95 percent of superfine slag powder and 5-10 percent of hydrated lime.

In the above technical scheme:

the phosphorus building gypsum is doped into the hydrated lime-slag powder system to generate a new hydration product ettringite, which is beneficial to improving the early compressive strength of the test piece. The proper amount of phosphorus building gypsum can reduce the adverse effect caused by the shrinkage of the test piece. However, the mixing amount should not be too high, otherwise, the test piece is easy to generate too much ettringite, so that the test piece is cracked, and the compressive strength is reduced. Meanwhile, the phosphorus building gypsum is doped into a slaked lime-slag powder system, so that part of soluble phosphorus and fluorine in the phosphorus building gypsum can be solidified, and the pollution to the environment is reduced.

Hydrated lime is used as an alkaline agent activator, and proper alkalinity is beneficial to the hydrolysis of slag and the stability of ettringite. The excessive mixing amount of the hydrated lime can inhibit the generation of ettringite and cause the compression strength of the test piece to be shrunk.

The invention discloses a preparation method of super-sulfate cement, which comprises the following specific operation steps: the weighed superfine slag powder, the phosphorus building gypsum and the hydrated lime are uniformly stirred, then the water is added into a stirring device, the uniformly mixed raw materials are added into the stirring device, and the mixture is stirred at a low speed for 2 minutes. The super-sulfate cement is obtained after stirring.

Drawings

FIG. 1 is a schematic representation of the effect of phosphorus building gypsum and hydrated lime on the compressive strength of a hardened super-sulfate cement slurry according to example 1 of the present invention;

FIG. 2 is a schematic representation of the effect of phosphorus building gypsum and hydrated lime on the self-shrinkage of a hardened super-sulfate cement slurry according to example 1 of the present invention;

FIG. 3 is a schematic representation of the effect of phosphorus building gypsum and hydrated lime on the compressive strength of a hardened super-sulfate cement slurry according to example 2 of the present invention;

FIG. 4 is a schematic representation of the effect of phosphorus building gypsum and hydrated lime on the self-shrinkage of a hardened super-sulfate cement slurry according to example 2 of the present invention;

FIG. 5 is a schematic representation of the effect of phosphorus building gypsum and hydrated lime of comparative example 1 on the compressive strength of a hardened super-sulfate cement slurry according to an embodiment of the present invention;

FIG. 6 is a schematic representation of the effect of comparative example 1 of phosphogypsum and hydrated lime on the self-shrinkage of a hardened super-sulfate cement slurry according to an embodiment of the present invention;

FIG. 7 is a graph showing the influence of phosphogypsum and hydrated lime on the compressive strength of a hardened slurry of super-sulfate cement in comparative example 2 in accordance with the present invention;

FIG. 8 is a graph showing the effect of phosphogypsum and hydrated lime on the self-shrinkage of a hardened slurry of super-sulfate cement according to comparative example 2 in the example of the present invention;

Detailed Description

The principles and features of this invention are described below in conjunction with examples which are set forth to illustrate, but are not to be construed to limit the scope of the invention.

Example 1

Raw material ratio: the phosphorous building gypsum accounts for 10% of the total amount of the cementing material, the superfine slag powder accounts for 80% of the total amount of the cementing material, and the hydrated lime accounts for 10% of the total amount of the cementing material. The blank group sample superfine slag powder accounts for 90% of the total amount of the cementing material, and the hydrated lime accounts for 10% of the total amount of the cementing material.

The preparation method comprises the following steps: firstly, uniformly stirring weighed superfine slag powder, phosphorus building gypsum and hydrated lime, then adding water into a stirring device, adding the uniformly mixed raw materials into the stirring device, and stirring at a low speed for 2 minutes. The super-sulphate cement is obtained after stirring.

Test conditions were as follows: the super-sulphate cement hardened slurries were tested for compressive strength at ages of 3d, 7d, 28d, 90d and 180d respectively. The test piece was tested for self-shrinkage at 30d and the results are shown in fig. 1 and fig. 2, respectively. When the content of the hydrated lime is 10%, the compressive strength of the hardened cement paste is increased by 183.3%, 67.1%, 70.3%, 52.7% and 20.6% compared with the blank group when the content of the phosphorus building gypsum is increased to 10% when the content of the hydrated lime is 3d, 7d, 28d, 90d and 180d respectively. The self-shrinkage reduction rate of the hardened cement paste at 30d was 53.6%.

Example 2

Raw material ratio: the phosphorous building gypsum accounts for 20% of the total amount of the cementing material, the superfine slag powder accounts for 70% of the total amount of the cementing material, and the hydrated lime accounts for 10% of the total amount of the cementing material. The blank group sample superfine slag powder accounts for 90% of the total amount of the cementing material, and the hydrated lime accounts for 10% of the total amount of the cementing material.

Test conditions were as follows: the super-sulphate cement hardened slurries were tested for compressive strength at ages of 3d, 7d, 28d, 90d and 180d respectively. The test pieces were tested for self-shrinkage at 30d, and the results are shown in fig. 3 and 4, respectively. When the amount of the hydrated lime is 10 percent, the compressive strength of the hardened cement slurry is respectively increased by 173.4 percent, 106.9 percent, 114.6 percent, 87.0 percent and 72.8 percent compared with the blank group when the amount of the phosphorus building gypsum is increased to 20 percent when the amount of the hydrated lime is respectively 3d, 7d, 28d, 90d and 180 d. The hardened cement paste exhibited an expansion characteristic of 30d with an expansion ratio of 0.35mm/m.

Comparative example 1

Raw material ratio: the phosphorous building gypsum accounts for 10% of the total amount of the cementing material, the superfine slag powder accounts for 85% of the total amount of the cementing material, and the hydrated lime accounts for 5% of the total amount of the cementing material. The superfine slag powder in the blank group sample accounts for 95% of the total amount of the cementing material, and the hydrated lime accounts for 5% of the total amount of the cementing material.

Test conditions were as follows: the super-sulphate cement hardened slurries were tested for compressive strength at ages of 3d, 7d, 28d, 90d and 180d respectively. The test pieces were tested for self-shrinkage at 30d, and the results are shown in fig. 5 and 6, respectively. When the content of the hydrated lime is 5%, the compressive strength of the hardened cement paste is increased by 131.8%, 96.8%, 43.4%, 55.4% and 40.3% compared with the blank group when the content of the phosphorus building gypsum is increased to 10% when the content of the hydrated lime is 3d, 7d, 28d, 90d and 180d respectively. The self-shrinkage reduction rate of the hardened cement paste at 30d was 65.5%.

Comparative example 2

Raw material ratio: the phosphorus building gypsum accounts for 20% of the total amount of the cementing material, the superfine slag powder accounts for 75% of the total amount of the cementing material, and the hydrated lime accounts for 5% of the total amount of the cementing material. The superfine slag powder in the blank group sample accounts for 95% of the total amount of the cementing material, and the hydrated lime accounts for 5% of the total amount of the cementing material.

The preparation method comprises the following steps: firstly, uniformly stirring weighed superfine slag powder, phosphorus building gypsum and hydrated lime, then adding water into a stirring device, adding the uniformly mixed raw materials into the stirring device, and stirring at a low speed for 2 minutes. The super-sulfate cement is obtained after stirring.

Test conditions were as follows: the super-sulphate cement hardened slurries were tested for compressive strength at ages of 3d, 7d, 28d, 90d and 180d respectively. The test pieces were tested for self-shrinkage at 30d, and the test results are shown in fig. 7 and fig. 8, respectively. When the content of the hydrated lime is 5%, the compressive strength of the hardened cement paste is increased by 240.9%, 181.0%, 91.4%, 111.6% and 64.2% at ages of 3d, 7d, 28d, 90d and 180d respectively when the content of the phosphorus building gypsum is increased to 20%. The self-shrinkage reduction rate of the hardened cement paste at 30d was 77.7%.

Claims

1. The phosphorus building gypsum-based super-sulfate cement is characterized by comprising superfine slag powder, phosphorus building gypsum and hydrated lime, wherein the components in percentage by mass are as follows: 0-20 percent of phosphorus building gypsum, 70-95 percent of superfine slag powder and 5-10 percent of hydrated lime.

2. The super sulfate cement according to claim 1, wherein the ultrafine slag powder has a specific surface area of 967m ² Kg, median particle size 2.151 microns, activity index of 127% and 106% for 7 days and 28 days, respectively.

3. The super sulfate cement of claim 1, wherein the phosphorous building gypsum is hemihydrate gypsum having a pH of 5.6 as a main component.

4. The super sulfate cement of claim 1, wherein the hydrated lime calcium hydroxide content is 95.15%.

5. A method for the preparation of a super sulphate cement according to claims 1 to 4, comprising the steps of: and (3) uniformly stirring the weighed superfine slag powder, the phosphorus building gypsum and the hydrated lime, adding water into a stirring device, adding the uniformly mixed raw materials into the stirring device, and stirring at a low speed for 2 minutes. The super-sulfate cement is obtained after stirring.