A foamed concrete and a method of making the same

Abstract

The application discloses a kind of foamed concrete and preparation method thereof.The foamed concrete of the application includes cement, fly ash, water, water reducing agent, foaming agent, foam stabilizer and bubble control agent;The bubble control agent is prepared by mixing water-based pressure-sensitive adhesive and temperature-sensitive adhesive, wherein the phase transition temperature of temperature-sensitive adhesive is controlled at 20-30 DEG C;The foaming agent is hydrogen peroxide.The application realizes the control of bubble volume by the temperature sensitivity and pressure sensitivity of bubble control agent in the foaming process, avoids the generation of interconnected pores;With hydrogen peroxide as foaming agent, pressure-sensitive adhesive and temperature-sensitive adhesive play a role in controlling bubble volume, and the bubble volume is controlled by pressure-sensitive adhesive and temperature-sensitive adhesive during the expansion of bubble;The strength of foamed concrete can be improved by using the ratio of the application, and the water absorption and thermal conductivity can be reduced.

Description

Technical Field

[0001] This invention relates to building materials, specifically to a foamed concrete and its preparation method. Background Technology

[0002] Foamed concrete is a lightweight material made by adding foaming agents and mixing it. It has many advantages and disadvantages. The main advantages include: (1) Lightweight and high strength: Foamed concrete has a low density but high strength, which can effectively reduce the weight of buildings and improve seismic performance. (2) Good thermal insulation performance: Because foamed concrete contains a large number of air bubbles, these air bubbles can effectively block heat transfer and loss, and have good thermal insulation performance. (3) Good sound insulation effect: Due to the porosity of foamed concrete, it can effectively absorb sound and reduce noise. (4) Good fire resistance: Foamed concrete is not a flammable material and can effectively prevent the spread of fire. (5) Environmentally friendly and sustainable: Foamed concrete has abundant raw materials, can be recycled, and is harmless to the environment. Therefore, it has broad application prospects.

[0003] However, besides the advantages mentioned above, it also has significant drawbacks. Foamed concrete generally suffers from uneven bubble size and numerous interconnected pores, resulting in low compressive strength, high water absorption, and high thermal conductivity. The main factor contributing to these adverse effects is the formation of interconnected pores during the preparation process, which increases defects and provides channels for water penetration. Therefore, the main way to improve the performance of foamed concrete during preparation is to control bubble size, prevent pore rupture and fusion, and reduce the formation of interconnected channels. Summary of the Invention

[0004] To address the problems existing in the above-mentioned background technology, the present invention proposes a foamed concrete and its preparation method, which can improve the strength of foamed concrete and reduce its water absorption and thermal conductivity.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0006] A type of foamed concrete comprises the following components, with the following mass percentages:

[0007]

[0008]

[0009] The bubble control agent is prepared by mixing 0.1-0.2 parts by weight of water-based pressure-sensitive adhesive and 0.1-0.3 parts by weight of temperature-sensitive adhesive; wherein the phase change temperature of the temperature-sensitive adhesive is controlled at 20-30℃.

[0010] The foaming agent is hydrogen peroxide, and the mass concentration of hydrogen peroxide is 10-12%.

[0011] The foam stabilizer is calcium stearate.

[0012] The cement is PO 42.5 ordinary Portland cement.

[0013] The fly ash is Class II fly ash.

[0014] The present invention also provides a method for preparing the above-mentioned foamed concrete, comprising the following steps:

[0015] (1) Store all raw materials in a constant temperature curing chamber at a temperature 0.5-2℃ lower than the phase change temperature of the thermosensitive adhesive for more than 4 hours to ensure that the temperature of all raw materials is consistent.

[0016] (2) Mix cement, fly ash, water, water-reducing agent, and bubble control agent and stir evenly to form a neat slurry;

[0017] (3) Pour the foaming agent and foam stabilizer into the neat slurry obtained in step (2), stir quickly for 25-30 seconds, and then pour it into the mold;

[0018] (4) Quickly move the mold described in step (3) into the sealed space, control the pressure of the sealed space to 0.15-0.3 MPa, until the foaming reaction ends, and obtain the foamed concrete of the present invention.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] In the preparation of foamed concrete, a bubble control agent is added. Through the temperature and pressure sensitivity of the bubble control agent during the foaming process, the volume of bubbles is controlled, preventing the formation of interconnected pores. Specifically, hydrogen peroxide is used as the foaming agent. During foaming, it releases heat, gradually raising the temperature of the foamed concrete. When the temperature-sensitive adhesive reaches its phase transition temperature, the adhesive's viscosity increases due to the phase transition, making it difficult for bubbles to grow further. This increases the support force on the bubble walls against bubble growth, reducing the risk of bubbles rupturing and forming interconnected pores. Simultaneously, the reaction occurs in a sealed space under a certain pressure, increasing the pressure on the bubble development and expansion. Under the action of the pressure-sensitive adhesive, as the pressure increases, the adhesive gradually undergoes a phase transition, increasing the mechanical properties of the bubble walls and effectively controlling further bubble expansion.

[0021] It should be noted that the exothermic reaction of hydrogen peroxide can rapidly increase the overall temperature of foamed concrete. This temperature increase further accelerates the release of gas from the hydrogen peroxide, increasing the reaction rate and promoting the formation and expansion of pores. Thermosensitive adhesive, through its own phase change during this temperature rise, increases the hardening strength of the bubble walls, thereby controlling the disorderly expansion of bubbles. This ensures that the foaming agent not only meets the bubble requirements of the foamed concrete but also avoids the adverse effects of excessive foaming on the foamed concrete structure.

[0022] Meanwhile, the foaming process with hydrogen peroxide further increases the internal pressure of the foamed concrete, stimulating the pressure-sensitive adhesive to gradually undergo phase change hardening, which is beneficial for controlling the bubble volume. Because larger bubbles withstand greater pressure, and the higher the viscosity of the pressure-sensitive adhesive, the greater the restraining force. Therefore, the pressure-sensitive adhesive can increase the difficulty of further disorderly expansion of bubbles, effectively controlling their volume.

[0023] In general, the synergistic effect of pressure-sensitive adhesive and temperature-sensitive adhesive—both can control bubble volume—further enhances bubble growth by controlling its expansion during the enlargement process, while temperature-sensitive adhesive controls bubble volume. However, the temperature-sensitive adhesive works at higher temperatures, leading to faster bubble reaction, fusion, and volume increase. Its adhesive strength increases with temperature, thus controlling the bubbles; the faster the temperature rises, the more pronounced the constraint effect. It primarily controls and constrains the bubbles as the reaction rate and temperature increase. In contrast, the pressure-sensitive adhesive controls bubble volume as pressure increases during bubble growth. One is related to reaction temperature, and the other to reaction pressure. Through the synergistic effect of temperature and pressure, the disorderly growth of bubbles is controlled, reducing volume defects in foamed concrete, improving its mechanical properties, and decreasing its water absorption and thermal conductivity. Detailed Implementation

[0024] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0025] The number of components used in each implementation and comparative example is expressed in parts by mass.

[0026] Example 1

[0027] A type of foamed concrete comprises the following components, with the following mass percentages:

[0028]

[0029] The bubble control agent is prepared by mixing 0.1 parts of water-based pressure-sensitive adhesive and 0.1 parts of temperature-sensitive adhesive; wherein the phase change temperature of the temperature-sensitive adhesive is controlled at 30°C.

[0030] The hydrogen peroxide concentration is 10%;

[0031] The above-mentioned method for preparing foamed concrete includes:

[0032] (1) Store all raw materials at 28℃ until the internal and external temperatures are consistent;

[0033] (2) Mix cement, fly ash, water, water-reducing agent, and bubble control agent and stir evenly to form a neat slurry;

[0034] (3) Pour the foaming agent hydrogen peroxide into the clean slurry in (2), stir quickly for 30 seconds, and then pour it into the mold;

[0035] (4) Quickly move the mold from (3) into the sealed space and control the pressure of the sealed space to 0.15 MPa until the foaming reaction ends.

[0036] Example 2

[0037] A type of foamed concrete comprises the following components, with the following mass percentages:

[0038]

[0039] The bubble control agent is prepared by mixing 0.15 parts of water-based pressure-sensitive adhesive and 0.15 parts of thermosensitive adhesive. The phase change temperature of the thermosensitive adhesive is controlled at 20℃.

[0040] The hydrogen peroxide concentration is 12%;

[0041] The above-mentioned method for preparing foamed concrete includes:

[0042] (1) Store all raw materials at 19.5℃ until the internal and external temperatures are consistent;

[0043] (2) Mix cement, fly ash, water, water-reducing agent, and bubble control agent and stir evenly to form a neat slurry;

[0044] (3) Pour the foaming agent hydrogen peroxide into the clean slurry in (2), stir quickly for 25 seconds, and then pour it into the mold;

[0045] (4) Quickly move the mold from (3) into the sealed space and control the pressure of the sealed space to 0.3 MPa until the foaming reaction ends.

[0046] Example 3

[0047] A type of foamed concrete comprises the following components, with the following mass percentages:

[0048]

[0049] The bubble control agent is prepared by mixing 0.2 parts of water-based pressure-sensitive adhesive and 0.3 parts of temperature-sensitive adhesive; wherein the phase change temperature of the temperature-sensitive adhesive is controlled at 25°C.

[0050] The hydrogen peroxide concentration is 11%.

[0051] The above-mentioned method for preparing foamed concrete includes:

[0052] (1) Store all raw materials at 24℃ until the internal and external temperatures are consistent;

[0053] (2) Mix cement, fly ash, water, water-reducing agent, and bubble control agent and stir evenly to form a neat slurry;

[0054] (3) Pour the foaming agent hydrogen peroxide into the clean slurry in (2), stir quickly for 28 seconds, and then pour it into the mold;

[0055] (4) Quickly move the mold from (3) into the sealed space and control the pressure of the sealed space to 0.2 MPa until the foaming reaction ends.

[0056] Comparative Example 1

[0057] The difference from Example 3 is that the amount of hydrogen peroxide added is 10 parts.

[0058] Comparative Example 2

[0059] The difference from Example 3 is that the amount of hydrogen peroxide added is 2 parts.

[0060] Comparative Example 3

[0061] The difference from Example 3 is that the amount of temperature-sensitive adhesive in the bubble control agent is 0.5 parts.

[0062] Comparative Example 4

[0063] The difference from Example 3 is that the pressure-sensitive adhesive content in the bubble control agent is 0.5 parts.

[0064] Comparative Example 5

[0065] The difference from Example 3 is that the hydrogen peroxide concentration is 20%.

[0066] Comparative Example 6

[0067] The difference from Example 3 is that the raw materials are stored at 20°C until the internal and external temperatures are consistent.

[0068] Comparative Example 7

[0069] The difference from Example 3 is that the foaming agent hydrogen peroxide is poured into the slurry in (2), and after being quickly stirred for 60 seconds, it is poured into the mold.

[0070] Comparative Example 8

[0071] The difference from Example 3 is that the mold in (3) is not transferred to the sealed space until the foaming reaction is over.

[0072] Comparative Example 9

[0073] The difference from Example 3 is that the mold in (3) is quickly moved into the sealed space and the pressure of the sealed space is controlled at 0.5 MPa until the foaming reaction ends.

[0074] Comparative Example 10

[0075] The difference from Example 3 is that no bubble control agent is added.

[0076] Comparative Example 11

[0077] The difference from Example 3 is that no bubble control agent is added, and the amount of foaming agent is adjusted so that the dry density after foaming is the same as that in Example 3.

[0078] Comparative Example 12

[0079] The difference from Example 3 is that the mold in (2) is not transferred to the sealed space, and the amount of foaming agent is adjusted so that the dry density of the foamed concrete is the same as that in Example 3.

[0080] The dry density, compressive strength, volume water absorption rate, and thermal conductivity of the foamed concrete test blocks in the various embodiments and comparative examples of the present invention were performed in accordance with the provisions of JC / T 1062-2022 "Foamed Concrete Blocks", and the results are shown in Table 1.

[0081] Table 1 Performance of Foamed Concrete in Each Example and Comparative Example

[0082]

[0083]

[0084] The following conclusions can be drawn from the data in Table 1:

[0085] Compared with Example 3, the amount of hydrogen peroxide foaming agent in Comparative Example 1 was too high, resulting in too many bubbles, forming a large number of interconnected pores and large air pores, which led to a decrease in compressive strength, an increase in thermal conductivity, and an increase in water absorption.

[0086] Compared with Example 3, the amount of hydrogen peroxide foaming agent in Comparative Example 2 was too low, resulting in too few bubbles being generated. Although the strength increased and the water absorption rate decreased, the thermal conductivity increased and the density was too high.

[0087] Compared to Example 3, Comparative Example 3 product has higher compressive strength and lower water absorption, but higher thermal conductivity and higher density. This is because the excessive amount of temperature-sensitive adhesive forms a strong gel network structure within the foamed concrete, which exerts a higher constraint on bubble development, resulting in smaller bubbles.

[0088] Compared to Example 3, Comparative Example 4 showed higher compressive strength and lower water absorption, but higher thermal conductivity and density. This was because the excessive amount of pressure-sensitive adhesive resulted in a stronger gel network structure forming within the bubble walls during the bubble formation process in the foamed concrete, exerting a higher constraint on bubble development and causing the bubbles to become smaller.

[0089] Compared to Example 3, the foamed concrete in Comparative Example 5 exhibited lower compressive strength, higher water absorption, and higher thermal conductivity. This is because the excessively high hydrogen peroxide concentration caused the bubble formation reaction to be too rapid, resulting in a large number of interconnected pores and large air pores, which in turn led to a decrease in compressive strength, an increase in thermal conductivity, and an increase in water absorption.

[0090] Compared to Example 3, the foamed concrete in Comparative Example 6 exhibited lower compressive strength, higher water absorption, and higher thermal conductivity. This indicates that when the temperature of the raw materials differs significantly from the phase transition temperature of the thermosensitive adhesive, during the heat generation process of hydrogen peroxide, the thermosensitive adhesive cannot undergo phase transition to constrain the bubble volume before reaching its phase transition temperature. Therefore, relying solely on the pressure-sensitive adhesive cannot achieve a satisfactory improvement. Consequently, the raw materials should be stored at a temperature 0.5–2°C below the phase transition temperature of the thermosensitive adhesive until the internal and external temperatures are consistent.

[0091] Compared to Example 3, the foamed concrete in Comparative Example 7 exhibited higher compressive strength, higher thermal conductivity, and lower water absorption. This is because prolonged stirring caused the foaming agent to react prematurely and release heat, resulting in gas loss. Simultaneously, the heat generated by the hydrogen peroxide reaction raised the temperature of the foamed concrete, causing it to reach the phase transition temperature of the thermosensitive adhesive at a lower foaming level, thus hindering further bubble growth.

[0092] Compared to Example 3, the foamed concrete in Comparative Example 8 exhibits lower compressive strength, higher water absorption, and higher thermal conductivity. This is because the purpose of pressurizing the sealed space is to increase the external environmental pressure of the foamed concrete reactant, which facilitates control of pore size. When removed from the sealed pressurized air, the external pressure decreases, which is detrimental to internal air pressure control. Furthermore, under these conditions, the excessively rapid foaming speed prevents the temperature-sensitive adhesive and pressure-sensitive adhesive from effectively controlling the bubbles, leading to bubble rupture and fusion, and an increase in internal defects.

[0093] Compared to Example 3, the foamed concrete in Comparative Example 9 exhibits higher compressive strength, higher thermal conductivity, lower water absorption, and higher density. Due to the higher spatial pressure, gas struggles to escape and form stable air bubbles, resulting in a denser structure.

[0094] Compared to Example 3, the foamed concrete in Comparative Example 10 exhibited lower compressive strength, higher thermal conductivity, higher water absorption, and lower density. Without the addition of a bubble control agent, the disordered growth and fusion of bubbles resulted in uneven bubble distribution, increased internal defects, a significant decrease in mechanical properties, and a substantial increase in water absorption.

[0095] Compared to Example 3, the foamed concrete in Comparative Example 11 had lower compressive strength and higher water absorption. This indicates that the bubble control agent, by controlling bubble development, can reduce internal defects, improve compressive strength, and reduce water absorption.

[0096] Compared to Example 3, the foamed concrete in Comparative Example 12 exhibited lower compressive strength and higher water absorption. This indicates that controlling the pressure within the foaming space helps the pressure-sensitive adhesive participate in regulating the bubble size and improving the performance of the foamed concrete.

Claims

1. A foamed concrete, characterized in that, It contains the following components, and the mass fractions of each component are as follows: The bubble control agent is prepared by mixing water-based pressure-sensitive adhesive and temperature-sensitive adhesive, wherein the phase change temperature of the temperature-sensitive adhesive is controlled at 20-30℃. The foaming agent is hydrogen peroxide, and the mass concentration of hydrogen peroxide is 10-12%.

2. A foamed concrete according to claim 1, characterised in that, The amounts of the two components in the bubble control agent are as follows: 0.1-0.2 parts by weight of water-based pressure-sensitive adhesive. 0.1 to 0.3 parts by weight of thermosensitive adhesive.

3. A foamed concrete according to claim 1 or 2, characterised in that, The foam stabilizer is calcium stearate.

4. A foamed concrete according to claim 1 or 2, characterised in that, The cement is PO 42.5 ordinary Portland cement.

5. A foamed concrete according to claim 1 or 2, characterised in that, The fly ash is Class II fly ash.

6. A method of making a foamed concrete according to any one of claims 1 to 5, characterised in that, Includes the following steps: (1) Store all raw materials in a constant temperature curing chamber at a temperature 0.5-2℃ lower than the phase change temperature of the thermosensitive adhesive for more than 4 hours to ensure that the temperature of all raw materials is consistent. (2) Mix cement, fly ash, water, water-reducing agent, and bubble control agent and stir evenly to form a neat slurry; (3) Pour the foaming agent and foam stabilizer into the neat slurry obtained in step (2), stir quickly for 25-30 seconds, and then pour it into the mold; (4) Quickly move the mold described in step (3) into the sealed space, control the pressure of the sealed space to 0.15-0.3 MPa, until the foaming reaction ends, and obtain the foamed concrete.

Images