Autoclaved aerated concrete block and preparation method thereof

Abstract

The invention provides an autoclaved aerated concrete block and a preparation method thereof. The autoclaved aerated concrete block comprises the following components in parts by mass: 8-15 parts of cement, 10-25 parts of modified lime, 3-8 parts of gypsum, 60-70 parts of fly ash, 0.05-0.1 part of aluminum powder, 0.01-0.05 part of a foam stabilizer and 55-70 parts of water. Wherein the modified lime is obtained by grinding steel slag and waste aerated blocks, then adding blocky lime and continuously grinding. The waste aerated blocks are added in the steel slag grinding process, the grindability of the steel slag is improved, and the steel slag and the lime have a synergistic effect under the guarantee of certain fineness, so that the strength of the autoclaved aerated concrete is ensured while part of the lime is replaced by the steel slag.

Description

Technical Field

[0001] The present invention relates to the technical field of autoclaved aerated concrete blocks, in particular to an autoclaved aerated concrete block and a preparation method thereof. Background Art

[0002] Autoclaved aerated concrete blocks are lightweight, porous silicate products made primarily from calcareous materials like lime, cement, and gypsum, along with siliceous materials like sand and fly ash, along with a foaming agent. These blocks are manufactured through a process that includes batching, mixing, pouring, pre-curing, cutting, autoclaving, and curing. Due to their numerous advantages, including lightweight, thermal insulation, and sound absorption, they are widely used in wall construction. The quality and dosage of cement and lime directly determine the quality and cost of aerated blocks. In actual production, lime is often more expensive than cement. Therefore, finding ways to reduce lime usage is key to lowering the cost of autoclaved aerated concrete.

[0003] Lime in aerated concrete primarily provides effective calcium oxide. The calcium hydroxide produced by hydration reacts with SiO2 and Al2O3 in the siliceous material to form hydrated calcium silicate and hydrated calcium aluminate, thereby imparting strength to the product. Furthermore, lime releases a certain amount of heat when it is digested in water, providing conditions for rapid hydration of the cement in the concrete, promoting hardening and shortening the concrete's stagnation time.

[0004] Steel slag, a byproduct of steelmaking, contains hydraulic minerals such as tricalcium silicate (C3S) and dicalcium silicate (C2S), making it a potentially hydrating cementitious material. However, the presence of iron and iron-containing compounds in steel slag results in poor abrasiveness. Furthermore, the presence of f-CaO and f-MgO in steel slag affects the stability of cement concrete products, resulting in a low overall utilization rate for steel slag. Summary of the Invention

[0005] The present invention provides an autoclaved aerated concrete block and a preparation method thereof. By adding discarded aerated blocks during the steel slag grinding process, the grindability of the steel slag is improved. Under a certain degree of fineness, the steel slag works synergistically with lime, thereby replacing part of the lime with the steel slag while ensuring the strength of the autoclaved aerated concrete.

[0006] The technical solution adopted to achieve the above-mentioned purpose of the present invention is:

[0007] The invention discloses an autoclaved aerated concrete block. The components and mass proportions of the autoclaved aerated concrete block are as follows: 8-15 parts of cement, 10-25 parts of modified lime, 3-8 parts of gypsum, 60-70 parts of fly ash, 0.05-0.1 parts of aluminum powder, 0.01-0.05 parts of foam stabilizer, and 55-70 parts of water. The modified lime is obtained by grinding steel slag and discarded aerated blocks, and then adding block lime and continuing to grind.

[0008] The components and mass ratios in the modified lime are: 10-25 parts of steel slag, 5-10 parts of waste aerated blocks, and 65-90 parts of lump lime.

[0009] The specific surface area of ​​the modified lime is not less than 350m 2 / kg.

[0010] The steel slag and waste aerated blocks are ground for 10 to 25 minutes, and then the lump lime is added and the grinding is continued for 20 to 30 minutes.

[0011] The cement is P·O42.5 cement.

[0012] The fly ash is Class I fly ash, and the 45 μm sieve residue is no more than 12%.

[0013] The gypsum is at least one of natural dihydrate gypsum, desulfurized gypsum and phosphogypsum.

[0014] The solid content of the aluminum powder is not less than 65%, and the residue on a 75 μm sieve is not more than 3%.

[0015] The foam stabilizer is at least one of hydroxypropyl methylcellulose, hydroxyethyl methylcellulose and xanthan gum.

[0016] The present invention also provides a method for preparing an autoclaved aerated concrete block, comprising the steps of: uniformly mixing cement, modified lime, gypsum, fly ash, aluminum powder, a foam stabilizer and water at 50-60° C., and pouring the mixture into a mold; curing the mixture at 60-75° C. for 2-4 hours to obtain a block body; demolding the block body, cutting and grouping the block body, and then curing the block body at a temperature of 180-200° C. and a pressure of 1.1-1.3 MPa for 8-10 hours to obtain an autoclaved aerated concrete block.

[0017] Compared with the prior art, the autoclaved aerated concrete blocks and the preparation method thereof provided by the present invention have the following advantages: 1. In the process of grinding steel slag, the present invention adds discarded aerated blocks, which can improve the grindability of steel slag and effectively increase the grinding fineness of steel slag; and the utilization of discarded aerated blocks can also increase the grinding fineness of lump lime and improve the grinding efficiency; under the guarantee of a certain fineness, f-CaO and f-MgO in steel slag can work synergistically with CaO in lime, thereby reducing the amount of lime used while ensuring that the strength of autoclaved aerated concrete meets the standards.

[0018] 2. The application of the discarded aerated blocks in the present invention also solves the problem of waste disposal in the production process of autoclaved aerated concrete. DETAILED DESCRIPTION

[0019] The following examples further describe the autoclaved aerated concrete blocks and their preparation methods of the present invention. These examples are provided by way of illustration to enable those familiar with the subject matter to understand and implement the present invention. However, these examples in no way limit the scope of protection of the present invention. Any equivalent variations or modifications made in accordance with the spirit and substance of the present invention are intended to fall within the scope of protection of the present invention.

[0020] Example 1

[0021] 10 parts of steel slag and 5 parts of discarded aerated blocks were weighed and added into a ball mill. After grinding for 10 minutes, 85 parts of lump lime were added and the grinding was continued for 20 minutes to obtain modified lime A.

[0022] Weigh 8 parts of cement, 25 parts of modified lime A, 6 parts of natural dihydrate gypsum, 61 parts of fly ash, 0.08 parts of aluminum powder, 0.04 parts of hydroxypropyl methylcellulose, and 62 parts of water, mix them evenly at 52°C, and pour them into a mold; cure them at 68°C for 3 hours to obtain a block body; demold the block body, cut and group it, and then place it at a temperature of 190°C and a pressure of 1.25 MPa for 8 hours to obtain an autoclaved aerated concrete block A.

[0023] Example 2

[0024] Weigh 20 parts of steel slag and 6 parts of discarded aerated blocks, add them into a ball mill, grind for 20 minutes, then add 79 parts of lump lime, and continue grinding for 20 minutes to obtain modified lime B.

[0025] Weigh 10 parts of cement, 20 parts of modified lime B, 5 parts of desulfurized gypsum, 65 parts of fly ash, 0.07 parts of aluminum powder, 0.04 parts of hydroxyethyl methylcellulose, and 60 parts of water, mix them evenly at 56°C, and pour them into a mold; cure them at 70°C for 2.5 hours to obtain a block body; demold the block body, cut and group it, and then place it at a temperature of 193°C and a pressure of 1.3 MPa for 8 hours to obtain an autoclaved aerated concrete block B.

[0026] Example 3

[0027] Weigh 20 parts of steel slag and 8 parts of discarded aerated blocks, add them into a ball mill, grind for 20 minutes, then add 72 parts of lump lime, and continue grinding for 20 minutes to obtain modified lime C.

[0028] Weigh 12 parts of cement, 18 parts of modified lime C, 4 parts of phosphogypsum, 66 parts of fly ash, 0.1 part of aluminum powder, 0.04 part of xanthan gum, and 61 parts of water, mix them evenly at 57°C, and pour them into a mold; cure them at 66°C for 3 hours to obtain a block body; demold the block body, cut and group it, and then place it at a temperature of 195°C and a pressure of 1.2 MPa for 9 hours to obtain an autoclaved aerated concrete block C.

[0029] Example 4

[0030] Weigh 20 parts of steel slag and 10 parts of waste aerated blocks, add them into a ball mill, grind them for 20 minutes, then add 65 parts of lump lime, and continue grinding for 20 minutes to obtain modified lime D.

[0031] 15 parts of cement, 10 parts of modified lime D, 5 parts of natural dihydrate gypsum, 70 parts of fly ash, 0.09 parts of aluminum powder, 0.05 parts of hydroxypropyl methylcellulose, and 55 parts of water were weighed, mixed evenly at 59° C., and poured into a mold; the mixture was cured at 63° C. for 3.5 hours to obtain a block body; the block body was demolded, cut and grouped, and then placed at a temperature of 195° C. and a pressure of 1.25 MPa for 9 hours to obtain an autoclaved aerated concrete block D.

[0032] Comparative Example 1

[0033] Weigh 20 parts of steel slag, add it into a ball mill, grind it for 20 minutes, then add 80 parts of lump lime, and continue grinding for 20 minutes to obtain modified lime E.

[0034] The specific surface areas of the modified limes obtained in Examples 1-4 and Comparative Example 1 are shown in the following table:

[0035] name Modified lime A Modified lime B Modified lime C Modified lime D Modified lime E <![CDATA[Specific surface area (m 2 / kg)]]> 433 403 379 355 440

[0036] When grinding steel slag, adding waste aerated blocks can improve the grindability of steel slag and effectively increase the grinding fineness of steel slag; and the use of waste aerated blocks can also increase the grinding fineness of lump lime and improve grinding efficiency.

[0037] Comparative Example 2

[0038] 12 parts of cement, 18 parts of lime, 5 parts of natural dihydrate gypsum, 70 parts of fly ash, 0.08 parts of aluminum powder, 0.03 parts of hydroxypropyl methylcellulose, and 65 parts of water were weighed, mixed evenly at 55°C, and poured into a mold; the mixture was cured at 70°C for 3 hours to obtain a block body; the block body was demolded, cut and grouped, and then placed at a temperature of 190°C and a pressure of 1.25 MPa for 8 hours to obtain an autoclaved aerated concrete block E.

[0039] The bulk density and absolute dry strength data of the autoclaved aerated concrete blocks prepared in Examples 1-4 and Comparative Example 2 are shown in the following table.

[0040] name Example 1 Example 2 Example 3 Example 4 Comparative Example 2 <![CDATA[Unit weight (kg / m 3 )]]> 612 597 588 572 602 Absolute dry strength / MPa 3.8 3.7 3.9 4.2 3.8

[0041] As shown in the table above, the autoclaved aerated concrete blocks produced in Examples 1-4 all meet the requirements for A3.5B05 grade aerated concrete blocks. This is because the f-CaO and f-MgO in the steel slag, while ensuring a certain fineness, can synergize with the CaO in the lime to enhance the strength of the autoclaved aerated concrete. This reduces lime usage while meeting the requirements for autoclaved aerated concrete blocks.

Claims

1. An autoclaved aerated concrete block, characterized by: The components and mass proportions of the autoclaved aerated concrete blocks are: 8-15 parts of cement, 10-25 parts of modified lime, 3-8 parts of gypsum, 60-70 parts of fly ash, 0.05-0.1 parts of aluminum powder, 0.01-0.05 parts of foam stabilizer, and 55-70 parts of water; the modified lime is obtained by grinding steel slag and discarded aerated blocks, and then adding block lime and continuing to grind.

2. The autoclaved aerated concrete block according to claim 1, characterized in that: The components and mass ratios in the modified lime are: 10-25 parts of steel slag, 5-10 parts of waste aerated blocks, and 65-90 parts of lump lime.

3. The autoclaved aerated concrete block according to claim 1, characterized in that: The specific surface area of ​​the modified lime is not less than 350m 2 / kg.

4. The autoclaved aerated concrete block according to claim 1, characterized in that: The steel slag and waste aerated blocks are ground for 10 to 25 minutes, and then the lump lime is added and the grinding is continued for 20 to 30 minutes.

5. The autoclaved aerated concrete block according to claim 1, characterized in that: The cement is P·O42.5 cement.

6. The autoclaved aerated concrete block according to claim 1, characterized in that: The fly ash is Class I fly ash, and the 45 μm sieve residue is no more than 12%.

7. The autoclaved aerated concrete block according to claim 1, characterized in that: The gypsum is at least one of natural dihydrate gypsum, desulfurized gypsum and phosphogypsum.

8. The autoclaved aerated concrete block according to claim 1, characterized in that: The solid content of the aluminum powder is not less than 65%, and the residue on a 75 μm sieve is not more than 3%.

9. The autoclaved aerated concrete block according to claim 1, characterized in that: The foam stabilizer is at least one of hydroxypropyl methylcellulose, hydroxyethyl methylcellulose and xanthan gum.

10. A method for preparing the autoclaved aerated concrete block according to claim 1, characterized in that: Cement, modified lime, gypsum, fly ash, aluminum powder, foam stabilizer and water are uniformly mixed at 50-60°C and poured into a mold; the blocks are cured at 60-75°C for 2-4 hours to obtain a block body; the block body is demoulded, cut and grouped, and then placed at a temperature of 180-200°C and a pressure of 1.1-1.3 MPa for curing for 8-10 hours to obtain an autoclaved aerated concrete block.