Retarding geopolymer concrete material and preparation method thereof

Abstract

Relating to the technical field of building materials, the invention provides a delayed coagulation type geopolymer concrete material, which comprises, by weight, 90-110 parts of recycled aggregate, 20-40 parts of a delayed coagulation type geopolymer, and 8-16 parts of water. Wherein the delayed coagulation type geopolymer comprises the following components in parts by weight: 50-70 parts of mineral powder, 30-50 parts of fly ash, 1-3 parts of a retarder and 10-20 parts of an alkali activator capsule; the invention also provides a preparation method of the delayed coagulation type geopolymer concrete material, which comprises the following steps: S1, recycling waste concrete, and crushing to obtain recycled aggregate; s2, filling sodium silicate powder into capsules to obtain alkali activator capsules; s3, mixing mineral powder, fly ash, a retarder and the alkali activator capsule prepared in S2 in proportion to obtain a delayed coagulation type geopolymer; and S4, stirring the recycled aggregate prepared in the S1, the delayed coagulation type geopolymer prepared in the S3 and water according to a ratio, and condensing to obtain the delayed coagulation type geopolymer concrete material.

Description

Technical Field

[0001] The invention relates to the technical field of building materials, and in particular to a slow-setting geopolymer concrete material and a preparation method thereof. Background Art

[0002] With the development of industrialization and urbanization in my country, a large number of old buildings have been demolished, resulting in a large amount of waste concrete, which seriously pollutes the environment. Preparing waste concrete into recycled aggregate and using it as a raw material for concrete can not only solve the problem of waste concrete disposal, but also save a lot of natural resources and achieve sustainable development of resources and environment. However, the surface of recycled aggregate is attached with old mortar, which will produce many cracks during the crushing process, resulting in poor performance of the newly mixed recycled aggregate concrete, making it difficult to achieve widespread application in engineering.

[0003] As the most frequently used cementitious material for concrete at present, the production process of cement is often accompanied by a large amount of energy consumption and a large amount of carbon dioxide emissions. More than 1.2 billion tons of CO2 are generated during the production of cement, accounting for more than 80% of the carbon emissions of China's building materials industry. At present, one of the main ways to solve the problem of excessive carbon emissions in the production of concrete is to use new cementitious materials to replace cement to control carbon emissions from the source. Replacing cement with industrial solid waste-based geopolymers as cementitious materials is a hot topic in current research. For example, industrial by-products such as fly ash, silica fume and slag form geopolymer-based cementitious materials that can replace cement under the action of alkaline or acidic activators. Recycled aggregates and geopolymer-based cementitious materials are combined to form low-carbon geopolymer recycled concrete. Compared with ordinary cement, geopolymer recycled concrete has the advantages of low hydration heat, good frost resistance and strong corrosion resistance. However, due to the action of alkaline activators, the setting time of geopolymer recycled concrete is short, which is not conducive to construction. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a slow-setting geopolymer concrete material and a preparation method thereof, which solves the problems in the prior art that the geopolymer concrete material has a short setting time and is not conducive to construction.

[0005] A slow-setting geopolymer concrete material, comprising, by weight, 90-110 parts of recycled aggregate, 20-40 parts of slow-setting geopolymer and 8-16 parts of water;

[0006] The slow-setting geopolymer comprises, by weight, 50-70 parts of mineral powder, 30-50 parts of fly ash, 1-3 parts of retarder and 10-20 parts of alkali activator capsules.

[0007] Preferably, the retarder is one of sodium polyphosphate, calcium gluconate and calcium sucrose.

[0008] Preferably, the alkali activator capsule is a capsule filled with sodium silicate powder.

[0009] Preferably, the modulus of the sodium silicate powder is 1.0-2.0.

[0010] Preferably, the capsule is a 4# drug capsule.

[0011] The present invention also provides a method for preparing a slow-setting geopolymer concrete material, which is characterized by comprising the following steps:

[0012] S1. Recycle waste concrete and crush it to obtain recycled aggregate;

[0013] S2. The sodium silicate powder is loaded into a capsule to obtain an alkali activator capsule;

[0014] S3. The mineral powder, fly ash, retarder and alkali activator capsules prepared in S2 are mixed in proportion to obtain a slow-setting geopolymer;

[0015] S4. The recycled aggregate prepared in S1, the slow-setting geopolymer prepared in S3 and water are mixed in proportion and then solidified to obtain a slow-setting geopolymer concrete material.

[0016] Preferably, the particle size of the recycled aggregate in step S1 is 0.16-19.5 mm.

[0017] Preferably, the content of sodium silicate powder in step S2 is 0.5 g.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. First, the retarder forms a protective film on the surface of the geopolymer particles to slow down its dissolution and hydration rate; secondly, the alkali activator is wrapped in the drug capsule to further form a slow-release agent. After a period of time, the capsule is dissolved and then released into the geopolymer slurry to solidify the slurry, thereby extending the setting time of the geopolymer cementitious material. It can make full use of the characteristics and advantages of recycled aggregates and geopolymers, so that the geopolymer concrete material has higher mechanical properties, working performance and economic and environmental value.

[0020] 2. The alkali activator used in the present invention is wrapped in food-grade medicine capsules, which further improves the environmental protection and working performance of the geopolymer concrete material.

[0021] 3. The slow-setting geopolymer concrete material provided by the present invention can have a setting time of more than 4 hours. DETAILED DESCRIPTION

[0022] In order to make the technical means, creative features, objectives and functions of the present invention clearer and easier to understand, the present invention is further described below in conjunction with specific embodiments:

[0023] Example 1

[0024] S1. Recycle the waste concrete from construction projects and crush it into recycled aggregate with a particle size of 0.16mm;

[0025] S2. 0.5 g of sodium silicate powder having a modulus of 1.0 was loaded into a 4# drug capsule to form an alkali activator capsule;

[0026] S3. Mix 50 parts of mineral powder, 50 parts of fly ash, 1 part of sodium polyphosphate and 20 parts of alkali activator capsules to form a slow-setting geopolymer;

[0027] S4. 100 parts of recycled aggregate, 40 parts of slow-setting geopolymer and 16 parts of water are continuously mixed in a mixer to obtain a slow-setting geopolymer concrete material after solidification.

[0028] Example 2

[0029] S1. Recycle the waste concrete from construction projects and crush it into recycled aggregate with a particle size of 10mm;

[0030] S2. 0.5 g of sodium silicate powder having a modulus of 1.5 was loaded into a 4# drug capsule to form an alkali activator capsule;

[0031] S3. 70 parts of mineral powder, 30 parts of fly ash, 3 parts of calcium gluconate and 10 parts of alkali activator capsules are mixed to form a slow-setting geopolymer;

[0032] S4. 90 parts of recycled aggregate, 20 parts of slow-setting geopolymer and 8 parts of water are continuously mixed in a mixer to obtain a slow-setting geopolymer concrete material after solidification.

[0033] Example 3

[0034] S1. Recycle the waste concrete from construction projects and crush it into recycled aggregate with a particle size of 19.5mm;

[0035] S2. 0.5 g of sodium silicate powder having a modulus of 2.0 was loaded into a 4# drug capsule to form an alkali activator capsule;

[0036] S3. 60 parts of mineral powder, 40 parts of fly ash, 2 parts of calcium sucrose and 15 parts of alkali activator capsules were mixed to form a slow-setting geopolymer;

[0037] S4. 110 parts of recycled aggregate, 30 parts of slow-setting geopolymer and 12 parts of water are continuously mixed in a mixer to obtain a slow-setting geopolymer concrete material after solidification.

[0038] Comparative Example 1

[0039] S1. Recycle the waste concrete from construction projects and crush it into recycled aggregate with a particle size of 19.5mm;

[0040] S2. 60 parts of mineral powder, 40 parts of fly ash, 2 parts of calcium sucrose and 15 parts of 0.5g of an alkali activator having a modulus of 2.0 are mixed to form a slow-setting geopolymer;

[0041] S3. 110 parts of recycled aggregate, 30 parts of slow-setting geopolymer and 12 parts of water are continuously mixed in a mixer to obtain a slow-setting geopolymer concrete material after solidification.

[0042] Comparative Example 2

[0043] S1. Recycle the waste concrete from construction projects and crush it into recycled aggregate with a particle size of 19.5mm;

[0044] S2. 60 parts of mineral powder, 40 parts of fly ash and 15 parts of 0.5g of an alkali activator having a modulus of 2.0 are mixed to form a slow-setting geopolymer;

[0045] S3. 110 parts of recycled aggregate, 30 parts of slow-setting geopolymer and 12 parts of water are continuously mixed in a mixer to obtain a slow-setting geopolymer concrete material after solidification.

[0046] The slow-setting geopolymer concrete materials prepared in Examples 1-3 and Comparative Examples 1-2 were cast in a 100mm×100mm×100mm test mold, demolded after 24 hours, and then placed in a standard curing room (temperature 25°C, humidity greater than 95%) for 28 days.

[0047] The setting time and compressive strength of Examples 1-3 and Comparative Examples 1-2 are shown in the following table:

[0048] Compressive strength MPa Initial setting time min Final setting time min Example 1 65.6 220 260 Example 2 68.5 250 290 Example 3 65.2 230 270 Comparative Example 1 67.3 45 62 Comparative Example 2 63.4 5 9

[0049] It can be seen from the above table that the slow-setting geopolymer concrete materials prepared in Examples 1-3 can have a long setting time while ensuring good compressive strength, thereby improving their construction performance, being more conducive to on-site construction, and being able to replace premixed natural concrete to achieve wide application.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A slow-setting geopolymer concrete material, characterized in that: In parts by weight, it comprises 90-110 parts of recycled aggregate, 20-40 parts of slow-setting geopolymer and 8-16 parts of water; The slow-setting geopolymer comprises, by weight, 50-70 parts of mineral powder, 30-50 parts of fly ash, 1-3 parts of retarder and 10-20 parts of alkali activator capsules.

2. The slow-setting geopolymer concrete material according to claim 1, characterized in that: The retarder is one of sodium polyphosphate, calcium gluconate and calcium sucrose.

3. The slow-setting geopolymer concrete material according to claim 1, characterized in that: The alkali activator capsule is a capsule filled with sodium silicate powder.

4. The slow-setting geopolymer concrete material according to claim 3, characterized in that: The modulus of the sodium silicate powder is 1.0-2.

0.

5. The slow-setting geopolymer concrete material according to claim 3, characterized in that: The capsule is a 4# medicine capsule.

6. The method for preparing a slow-setting geopolymer concrete material according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1. Recycle waste concrete and crush it to obtain recycled aggregate; S2. The sodium silicate powder is loaded into a capsule to obtain an alkali activator capsule; S3. The mineral powder, fly ash, retarder and alkali activator capsules prepared in S2 are mixed in proportion to obtain a slow-setting geopolymer; S4. The recycled aggregate prepared in S1, the slow-setting geopolymer prepared in S3 and water are mixed in proportion and then solidified to obtain a slow-setting geopolymer concrete material.

7. The method for preparing a slow-setting geopolymer concrete material according to claim 6, characterized in that: The particle size of the recycled aggregate in step S1 is 0.16-19.5 mm.

8. The method for preparing a slow-setting geopolymer concrete material according to claim 6, characterized in that: The content of sodium silicate powder in step S2 is 0.5 g.