Anti-freezing baking-free brick and preparation method thereof

Abstract

The invention discloses an anti-freezing baking-free brick and a preparation method thereof. The anti-freezing baking-free brick comprises the following components in percentage by mass: 45-60% of granite weathered soil and 40-55% of cement. The granite weathered soil is used for preparing the freezing-resistant baking-free brick, the technological process is simple and convenient, the materials are easy to obtain, energy consumption is reduced, industrial large-scale production is easy, a series of freezing-resistant baking-free brick products covering the two strength grades of MU15 and MU20 can be prepared by adjusting the ratio of the raw materials, and the freezing-resistant baking-free brick has high practicability.

Description

Technical Field

[0001] The invention relates to the technical field of building materials, and in particular to a frost-resistant unburned brick and a preparation method thereof. Background Art

[0002] Unburned bricks are a new type of wall material. They are mainly made of fly ash, coal slag, coal gangue, tailings slag, chemical slag and other waste materials as raw materials. They are manufactured without high-temperature calcination and have the advantages of high material strength, good durability, standard size, complete appearance and convenient construction. However, compared with traditional sintered bricks, unburned bricks have lower strength. In cold areas, when water freezes inside the bricks, the volume expands, destroying the internal structure of the bricks, causing the bricks to crack or be damaged. That is, the freeze-thaw resistance of unburned bricks is relatively poor. As the country's quality requirements for large-scale projects continue to increase, while meeting the strength requirements, the requirements for the frost resistance of unburned bricks are gradually increasing, which has become an important issue that needs to be solved urgently.

[0003] With the rapid development of my country's infrastructure, the excessive use of natural sand in the construction industry has had a serious impact on the safety of water conservancy facilities such as river embankments and the stability of river channels. In addition, due to environmental protection policy requirements, the production of artificial sand has increased, reaching 3 billion tons per year. However, in the process of mining ore, the weathered layer covering the surface of the mine cannot be used as a production raw material. After being stripped, it is placed in a stockpile for processing, which not only occupies a large amount of land resources, but also easily causes dust, landslides and other disasters when it is piled in the open air, seriously threatening the safety of surrounding residents. Therefore, the resource utilization of weathered soil is imminent.

[0004] At present, there are few patents for the preparation of frost-resistant unburned bricks using weathered soil, and the theoretical and practical development is still imperfect. In the prior art, patent CN106082947A discloses an unburned brick with good frost resistance, which uses flue gas dust removal soil, red soil, halloysite, coal gangue, natural sand, alkalized cotton stalks, Kiryu sand, etc. as raw materials, and is formed through grinding, mixing, pressing, curing and other steps to prepare a 28-day compressive strength of 19 MPa, a mass loss of 1.3% after freeze-thaw cycles, and a strength loss of 2.2%. However, the raw materials used in this method are complex, and the dilemma of excessive use of natural sand has not been solved; at the same time, the raw material pretreatment stage must undergo grinding and other processes, and the finished product curing needs to be carried out in a CO2 atmosphere with a purity of 65%, which is complex and costly. Patent CN116082019A discloses an environmentally friendly unburned brick produced using granite mine tailings and a preparation method thereof, which uses granite mine tailings, cement, quicklime and water glass as raw materials, and prepares unburned bricks through mixing, aging, molding, steam curing and other processes. Finally, unburned bricks with a compressive strength of 18.4 MPa are obtained. However, this method has the disadvantages of complex raw material combination and long aging cycle, and steam curing must be carried out at 80~100 ℃. The process is cumbersome and costly, and the antifreeze performance of the bricks has not been studied. Summary of the invention

[0005] In view of the above-mentioned shortcomings, the purpose of the present invention is to provide a frost-resistant unfired brick and a preparation method thereof, so as to solve the technical problems of complex raw materials and high production cost in the prior art for preparing frost-resistant unfired bricks.

[0006] To achieve the above object, the present invention is implemented through the following technical solutions: In a first aspect, the present invention provides a frost-resistant unfired brick, which comprises, by mass percentage, 45-60% of granite weathered soil and 40-55% of cement.

[0007] Preferably, the granite weathered soil comprises SiO2, Al2O3, Fe2O3, K2O, Na2O, MgO and CaO, wherein the mass ratio of SiO2, Al2O3, Fe2O3, K2O, Na2O, MgO and CaO is (40~50):(20~30):(5~10):(1~2):(1~2):(1~2):(1~2):(1~2).

[0008] Preferably, the particle size of the granite weathered soil is ≤4.75 mm.

[0009] Preferably, the cement is Portland cement.

[0010] Preferably, the silicate cement is one or more of 52.5 grade silicate cement, 42.5 grade silicate cement, and 32.5 grade silicate cement.

[0011] In a second aspect, the present invention provides a method for preparing frost-resistant unfired bricks, comprising the following steps: S1. Screening the granite weathered soil to obtain a first material; S2, mixing the first material and cement evenly to obtain a second material; S3, mixing the second material and water evenly, and pressing and molding to obtain a brick; S4. Curing the bricks to obtain frost-resistant and unfired bricks.

[0012] Preferably, in step S1, the sieve used for screening is 4 mesh. Preferably, in step S3, the amount of water used is 15-20% of the mass of the second material.

[0013] Preferably, in step S3, the pressure of the pressing molding is 20-25 MPa, and the molding time is 2-5 min.

[0014] Preferably, in step S4, the curing temperature is 20-27° C., the curing humidity is 90%-97%, and the curing time is 28-30 days.

[0015] The beneficial effects of the present invention are: The invention uses granite weathered soil and cement as main raw materials, and the prepared unburned brick has a 28-day compressive strength of 17-25 MPa, a softening coefficient of 87-98%, and a strength loss rate of less than 10% after freeze-thaw cycles, which meets the performance requirements of unburned bricks in JC / T 422-2007 "Non-burned garbage tailings bricks", not only realizes the efficient, harmless and resourceful utilization of weathered soil, but also broadens the raw material source of unburned bricks, and realizes a high degree of unity of environmental benefits, economic benefits and social benefits; at the same time, it has important practical significance for promoting the sustainable green development of the building materials industry.

[0016] The present invention uses granite weathered soil as the main material to prepare frost-resistant unburned bricks, realizing the transformation of weathered soil into treasure. The prepared unburned bricks have higher strength and excellent frost resistance, saving clay raw materials and natural sand. In addition, frost-resistant unburned bricks can be prepared by only mixing, tableting and curing, without lengthy preliminary raw material processing work, abandoning the high-energy consumption sintering step, and having a simple preparation process, mild curing conditions and low production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solution of the embodiment of the present invention, the drawings of the embodiment are briefly introduced below.

[0018] Figure 1 The present invention is a process flow chart of the preparation of frost-resistant unfired bricks. DETAILED DESCRIPTION

[0019] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] The main chemical components of weathered granite soil are SiO2, Al2O3 and Fe2O3, etc. Its main properties are similar to those of building aggregates, and it can be used as an admixture and aggregate to prepare unburned bricks. 3+ During the cement hydration process, Al 3+ Replacement occurs, and then a large amount of ettringite and iron glue (FH3) are generated, which enhances the frost resistance of unfired bricks. Figure 1 As shown, an embodiment of the present invention provides a method for preparing frost-resistant unfired bricks, comprising the following steps: S1. Pass the granite weathered soil through a 4-mesh sieve to obtain the first material; S2. By mass percentage, 45-60% of the first material and 40-55% of cement are mixed evenly to obtain a second material; S3, mixing the second material and water evenly, wherein the amount of water is 15-20% of the mass of the second material, pressing and molding at 20-25 MPa for 2-5 min to obtain a brick; S4. Curing the bricks at 20-27 ℃ and 90%-97% humidity for 28-30 days to obtain frost-resistant unfired bricks.

[0021] The present invention utilizes granite weathered soil to prepare frost-resistant unfired bricks, which not only has a simple process flow, readily available materials, saves energy, and is easy to mass produce, but also can prepare a series of frost-resistant unfired brick products covering two strength grades of MU15 and MU20 by adjusting the raw material ratio, and has high practicality.

[0022] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be described in further detail below.

[0023] The main chemical composition of the weathered granite soil used in the following examples and comparative examples is: SiO2: 48.88%, Al2O3: 28.03%, Fe2O3: 8.68%, K2O: 1.86%, Na2O: 1.70%, MgO: 1.68%, and CaO: 1.57%.

[0024] Example 1 A frost-resistant unfired brick, the preparation method is as follows: S1. Pass the granite weathered soil through a 4-mesh square hole standard sieve to obtain the undersize material, which is the first material.

[0025] S2. Evenly mix 45 wt% of the first material and 55 wt% of PO 525 Portland cement to obtain a second material.

[0026] S3. Add municipal water accounting for 15 wt% of the second material to the second material, mix well and place in a mold, press and form on a tablet press with a molding pressure of 20 MPa and a molding time of 2 min to obtain a brick.

[0027] S4. Curing the bricks in a constant temperature and humidity curing box at a temperature of 25°C and a humidity of 95% for 28 days to obtain frost-resistant unfired bricks.

[0028] Example 2 A frost-resistant unfired brick, the preparation method is as follows: S1. Pass the granite weathered soil through a 4-mesh square hole standard sieve to obtain the undersize material, which is the first material.

[0029] S2. Evenly mix 50 wt % of the first material and 50 wt % of PO 525 Portland cement to obtain a second material.

[0030] S3. Add municipal water accounting for 15 wt% of the second material to the second material, mix well and place in a mold, press and form on a tablet press with a molding pressure of 20 MPa and a molding time of 2 min to obtain a brick.

[0031] S4. Curing the bricks in a constant temperature and humidity curing box at a temperature of 25°C and a humidity of 95% for 28 days to obtain frost-resistant unfired bricks.

[0032] Example 3 A frost-resistant unfired brick, the preparation method is as follows: S1. Pass the granite weathered soil through a 4-mesh square hole standard sieve to obtain the undersize material, which is the first material.

[0033] S2. Evenly mix 55 wt% of the first material and 45 wt% of PO 525 Portland cement to obtain a second material.

[0034] S3. Add municipal water accounting for 15 wt% of the second material to the second material, mix well and place in a mold, press and form on a tablet press with a molding pressure of 20 MPa and a molding time of 2 min to obtain a brick.

[0035] S4. Curing the bricks in a constant temperature and humidity curing box at a temperature of 25°C and a humidity of 95% for 28 days to obtain frost-resistant unfired bricks.

[0036] Example 4 A frost-resistant unfired brick, the preparation method is as follows: S1. Pass the granite weathered soil through a 4-mesh square hole standard sieve to obtain the undersize material, which is the first material.

[0037] S2. Evenly mix 60 wt % of the first material and 40 wt % of PO 525 Portland cement to obtain a second material.

[0038] S3. Add municipal water accounting for 15 wt% of the second material to the second material, mix well and place in a mold, press and form on a tablet press with a molding pressure of 20 MPa and a molding time of 2 min to obtain a brick.

[0039] S4. Curing the bricks in a constant temperature and humidity curing box at a temperature of 25°C and a humidity of 95% for 28 days to obtain frost-resistant unfired bricks.

[0040] Comparative Example 1 A frost-resistant unfired brick, the preparation method is as follows: S1. Pass the granite weathered soil through a 4-mesh square hole standard sieve to obtain the undersize material, which is the first material.

[0041] S2. Evenly mix 65 wt % of the first material and 35 wt % of PO 525 Portland cement to obtain a second material.

[0042] S3. Add municipal water accounting for 15 wt% of the second material to the second material, mix well and place in a mold, press and form on a tablet press with a molding pressure of 20 MPa and a molding time of 2 min to obtain a brick.

[0043] S4. Curing the bricks in a constant temperature and humidity curing box at a temperature of 25°C and a humidity of 95% for 28 days to obtain frost-resistant unfired bricks.

[0044] Comparative Example 2 The difference between this comparative example and Example 2 is that the granite weathered soil was subjected to magnetic separation and iron removal operation. The main chemical components of the granite weathered soil after magnetic separation are SiO2: 45.66%, Al2O3: 26.53%, Fe2O3: 4.45%, K2O: 1.51%, Na2O: 1.46%, MgO: 1.23%, and CaO: 1.04%.

[0045] The performance tests were performed on the unfired bricks obtained in Examples 1 to 4 and Comparative Examples 1 to 2, and the results are shown in Table 1.

[0046] Table 1 Test results of Examples 1 to 4 and Comparative Examples 1 to 2

[0047] It can be seen from Table 1 that the unfired bricks prepared in Examples 1 to 4 of the present invention have excellent compressive strength, water absorption, frost resistance and softening coefficient, meet the requirements of JC / T 422-2007 "Non-fired garbage tailings bricks", cover two strength grades of MU15 and MU20, and after 15 freeze-thaw cycles, the brick structure is stable and there is no obvious defect in appearance.

[0048] Compared with Example 1, Comparative Example 1 uses a higher weathered soil content. The compressive strength, water absorption rate, softening coefficient and frost resistance of the prepared unfired brick are not as good as those of the example. The compressive strength even drops sharply to 12.04 MPa after freeze-thaw, and the strength loss rate reaches 16.33%. This is because the weathered soil particle size is large. With the increase of weathered soil content, the porosity of the internal structure of the brick increases, resulting in a decrease in density and an increase in water absorption rate. During the freeze-thaw cycle, a higher water absorption rate means a larger expansion volume of water during freeze-thaw, that is, the brick structure is more easily destroyed, which is manifested macroscopically as a decrease in the compressive strength of the brick.

[0049] Compared with Example 2, Comparative Example 2 showed a higher strength loss after freeze-thaw. This is due to the fact that Fe 3+ It can promote the hydration activity of cement during the hydration process and react with Al 3+ Replacement occurs, generating a large amount of ettringite and iron glue (FH3), making the brick structure denser, thereby increasing the compressive strength of the brick, reducing water absorption, increasing density and making the antifreeze performance better. 3+ A decrease in the content has a negative impact on these properties.

[0050] It should be noted that the above embodiments all belong to the same inventive concept, and the description of each embodiment has its own focus. For matters that are not described in detail in some embodiments, reference may be made to the description in other embodiments.

[0051] The above-mentioned embodiments only express the implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the attached claims.

Claims

1. A frost-resistant unfired brick, characterized in that: Calculated by mass percentage, it includes 45~60% granite weathered soil and 40~55% cement.

2. The frost-resistant unburned brick according to claim 1, characterized in that: The granite weathered soil includes SiO2, Al2O3, Fe2O3, K2O, Na2O, MgO and CaO, wherein the mass ratio of SiO2, Al2O3, Fe2O3, K2O, Na2O, MgO and CaO is (40~50):(20~30):(5~10):(1~2):(1~2):(1~2):(1~2):(1~2).

3. The frost-resistant unburned brick according to claim 1, characterized in that: The particle size of the granite weathered soil is ≤4.75 mm.

4. The frost-resistant unburned brick according to claim 1, characterized in that: The cement is silicate cement.

5. The frost-resistant unburned brick according to claim 4, characterized in that: The silicate cement is one or more of 52.5 grade silicate cement, 42.5 grade silicate cement and 32.5 grade silicate cement.

6. A method for preparing the frost-resistant unburned brick according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1. Screening the granite weathered soil to obtain a first material; S2, mixing the first material and cement evenly to obtain a second material; S3, mixing the second material with water evenly, and pressing and molding to obtain a brick; S4, curing the bricks to obtain frost-resistant unfired bricks.

7. The method for preparing frost-resistant unburned bricks according to claim 6, characterized in that: In step S1, the sieve used for screening is 4 mesh.

8. The method for preparing frost-resistant unburned bricks according to claim 6, characterized in that: In step S3, the amount of water used is 15-20% of the mass of the second material.

9. The method for preparing the frost-resistant unburned brick according to claim 6, characterized in that: In step S3, the pressing pressure is 20-25 MPa, and the pressing time is 2-5 min.

10. The method for preparing frost-resistant unburned bricks according to claim 6, characterized in that: In step S4, the curing temperature is 20-27°C, the curing humidity is 90%-97%, and the curing time is 28-30 days.

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