Preparation method and application of self-fire-resistant aggregate

Abstract

The present application relates to a kind of preparation method and application of self-fire-resistant aggregate, belong to building material technical field.The preparation method of the present application includes the following steps: (1) fireproof material is placed in paraffin wax, stirring, paraffin wax-wrapped fireproof material can be obtained;(2) paraffin wax-wrapped fireproof material obtained in step (1) is sequentially cooled, air-dried, finally using cement and epoxy resin to paraffin wax-wrapped fireproof material is secondly encapsulated and wrapped, and self-fire-resistant aggregate is prepared.The preparation method of the present application is simple, has good application prospect, and the cement and epoxy resin used in the prepared self-fire-resistant aggregate as the shell of aggregate, can guarantee that the fireproof material in the interior of aggregate does not leak out at room temperature, and can be discharged from aggregate under fire, to form carbon layer on the surface of UHPC to insulate heat and oxygen, to play the function of fire prevention, improve the fire resistance of UHPC structure.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, and specifically relates to a method for preparing and applying a self-fire-resistant aggregate. Background Technology

[0002] Fire safety in building structures remains a significant and ongoing challenge in the field of civil engineering. Although UHPC is a non-combustible material, the rapid temperature rise during a fire can lead to mechanical property degradation and cracking, seriously threatening the integrity and safety of the structure. High-temperature cracking of UHPC originates from the enormous vapor pressure generated by the heating and vaporization of pore water within it. When this pressure exceeds the tensile strength of the UHPC, it causes sudden rupture of the UHPC surface, directly exposing critical reinforcing steel bars to the fire and drastically accelerating the structural failure process.

[0003] Currently, most technical means to improve the fire resistance of UHPC structures are "passive" defense or "post-event" mitigation strategies, which have significant limitations. For example, coating the structural surface with fire-retardant paint or wrapping it with fire-resistant boards. This method is complex to implement, affects the building's aesthetics, and the paint is prone to aging and peeling. Furthermore, the durability of its protective effectiveness is questionable, and maintenance costs are high.

[0004] In recent years, some studies have attempted to improve the high-temperature resistance of UHPC by introducing phase change materials to absorb heat. However, the core function of these "heat-absorbing" aggregates lies in the storage and delayed release of heat; their effect is essentially a passive temperature buffer, and they do not fundamentally change the material's behavior in flames. They cannot actively construct a physical barrier to isolate oxygen, block heat flow, and strengthen themselves and the surrounding matrix in the extreme environment of a fire.

[0005] Therefore, there is an urgent need in this field for an "active" fire-resistant solution, namely, the development of a self-fire-resistant aggregate. This aggregate should not only possess the mechanical properties of conventional aggregates, but more importantly, it should be able to spontaneously and intelligently undergo a series of physicochemical reactions upon reaching a specific critical temperature: for example, rapidly decomposing to produce non-combustible gases to isolate oxygen, thereby achieving a "self-fire-resistant" function—self-expanding to isolate heat and oxygen, and self-reinforcing structural protection. This shift from "passively enduring" to "actively resisting" will fundamentally improve the survivability of UHPC structures in fires.

[0006] Existing conventional artificial aggregate preparation technologies cannot achieve this goal, lacking microstructural design and functional modification to generate active fire-resistant effects in aggregates at high temperatures. Developing a simple, cost-effective, and stable method for preparing self-fire-resistant aggregates, and applying it to the preparation of self-fire-resistant UHPCs, is of great significance for improving the disaster prevention and mitigation capabilities of lifeline projects such as critical infrastructure, super high-rise buildings, and offshore platforms. Summary of the Invention

[0007] To address the aforementioned shortcomings of existing technologies, the present invention aims to provide a method for preparing self-resistant fire-resistant aggregate, comprising the following steps: (1) The fireproof material is placed in molten paraffin and stirred to coat it, thus obtaining a paraffin-coated fireproof material; (2) Cool and air dry the fireproof material wrapped in paraffin obtained in step (1), and finally encapsulate the fireproof material wrapped in paraffin with cement and epoxy resin to obtain self-fire-resistant aggregate.

[0008] Preferably, the fireproof material in step (1) is mainly composed of a carbon source, an acid source, and a gas source mixed in a mass ratio of 2-5:2-3:1-3.

[0009] Preferably, the carbon source is one or more of pentaerythritol, starch, sucrose, and phenolic resin, and the acid source is one or more of ammonium polyphosphate, ammonium phosphate, and zinc borate.

[0010] Preferably, the gas source is one or more of melamine, dicyandiamide, and urea.

[0011] Preferably, the cooling process in step (2) uses water cooling for 1-3 minutes at room temperature; the air drying process takes 6-10 hours.

[0012] Preferably, the method of encapsulating the paraffin-coated fireproof material with cement and epoxy resin in step (2) includes the following steps: (A) Add the paraffin-coated fire-retardant material to the epoxy resin and stir; (B) Pour the paraffin-coated fireproof material obtained in step (A) into the cement powder, stir, and perform a second coating; the cement is ordinary Portland cement as specified in the national standard GB 175-2020 "General Portland Cement".

[0013] (C) The self-fire-resistant aggregate after secondary encapsulation in step (B) is cured at room temperature to complete the encapsulation.

[0014] Preferably, in step (A), the mass ratio of epoxy resin to paraffin-coated fireproof material is 1:2-1:5, and the stirring time is 2-5 minutes.

[0015] Preferably, the curing time at room temperature in step (C) is 1-3 days.

[0016] Preferably, the self-fire-resistant aggregate prepared by the above method is used in the preparation of UHPC.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention uses fire-retardant materials as raw materials, performs a primary encapsulation with molten paraffin, and then a secondary encapsulation with cement and epoxy resin to prepare self-fire-resistant aggregate. The preparation method is simple and has good application prospects. The cement and epoxy resin used in the prepared self-fire-resistant aggregate serve as the outer shell of the aggregate, ensuring that the fire-retardant material inside the aggregate does not leak out at room temperature and can be expelled from the aggregate in the event of a fire. This forms a char layer on the UHPC surface to insulate against heat and oxygen, thus providing fire protection and improving the fire resistance of the UHPC structure. Attached Figure Description

[0018] Figure 1 The temperature curves are shown for the self-refractory aggregate in Example 1 and the ordinary aggregate in Comparative Example 1. Detailed Implementation

[0019] The following is a description of the principles and features of this invention. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer should be followed. Reagents or instruments used, unless otherwise specified, are all commercially available products. Example 1:

[0020] A method for preparing self-fire-resistant aggregate includes the following steps: (1) The purchased fireproof materials (pentaerythritol, ammonium polyphosphate and melamine in a mass ratio of 2:2:1) were ground and sieved. (2) Place the granular paraffin in a water bath and heat it until it melts. Then place the fireproof material from step (1) into the molten paraffin, stir it, and encapsulate it to obtain the paraffin-coated fireproof material. (3) Quickly put the fireproof material wrapped in paraffin wax in step (2) into a water-cooled bucket and treat it at room temperature for 2 minutes. Then place the fireproof material wrapped in paraffin wax after water cooling in an indoor environment to air dry for 8 hours so that the paraffin wax can completely wrap the fireproof material.

[0021] (4) The fireproof material coated with paraffin obtained in step (3) is immersed in epoxy resin. The mass ratio of epoxy resin to fireproof material coated with paraffin is 1:2. Stir thoroughly for 3 minutes to ensure that the epoxy resin completely coats the surface of the paraffin.

[0022] (5) Pour the epoxy resin-coated paraffin from step (4) into the cement powder, stir, and effectively separate the fireproof material with epoxy resin by filtration. Then cure at room temperature for 2 days to obtain the self-fire-resistant aggregate. Example 2:

[0023] A method for preparing self-fire-resistant aggregate includes the following steps: (1) The purchased fireproof materials (pentaerythritol, ammonium polyphosphate and melamine in a mass ratio of 5:2:3) were ground and sieved. (2) Place the granular paraffin in a water bath and heat it until it melts. Then place the fireproof material from step (1) into the molten paraffin, stir it, and encapsulate it to obtain the paraffin-coated fireproof material. (3) Quickly put the fireproof material wrapped in paraffin wax in step (4) into a water-cooled bucket and treat it at room temperature for 1 minute. Then place the fireproof material wrapped in paraffin wax after water cooling in an indoor environment to air dry for 10 hours so that the paraffin wax can fully wrap the fireproof material.

[0024] (4) The fireproof material coated with paraffin obtained in step (3) is immersed in epoxy resin. The mass ratio of epoxy resin to fireproof material coated with paraffin is 1:3. Stir thoroughly for 2 minutes to ensure that the epoxy resin completely coats the surface of the paraffin.

[0025] (5) Pour the epoxy resin-coated paraffin from step (4) into the cement powder, stir, and effectively separate the fireproof material with epoxy resin by filtration, and then cure at room temperature for 3 days to obtain self-fire-resistant aggregate. Example 3:

[0026] A method for preparing self-fire-resistant aggregate includes the following steps: (1) The purchased fireproof materials (pentaerythritol, ammonium polyphosphate and melamine in a mass ratio of 3:3:1) were ground and sieved. (2) Place the granular paraffin in a water bath and heat it until it melts. Then place the fireproof material from step (1) into the molten paraffin, stir it, and encapsulate it to obtain the paraffin-coated fireproof material. (3) Quickly put the fireproof material wrapped in paraffin wax in step (2) into a water-cooled bucket and treat it at room temperature for 3 minutes. Then place the fireproof material wrapped in paraffin wax after water cooling in an indoor environment to air dry for 6 hours so that the paraffin wax can completely wrap the fireproof material.

[0027] (4) The fireproof material coated with paraffin obtained in step (3) is immersed in epoxy resin. The mass ratio of epoxy resin to fireproof material coated with paraffin is 1:5. Stir thoroughly for 5 minutes to ensure that the epoxy resin completely coats the surface of the paraffin.

[0028] (5) Pour the epoxy resin-coated paraffin from step (4) into the cement powder, stir, and effectively separate the fireproof material with epoxy resin by filtration, and then cure at room temperature for 1 day to obtain self-fire-resistant aggregate.

[0029] Comparative Example 1: A method for preparing self-fire-resistant aggregate includes the following steps: (1) Place the granular paraffin in a water bath and heat it until it melts. Stir it to obtain aggregate-like paraffin (particle size of about 1 mm). (2) Quickly place the aggregate-like paraffin into a water-cooled tank and treat it at room temperature for 2 minutes. Then, place the water-cooled aggregate-like paraffin in an indoor environment to air dry for 8 hours to ensure that the aggregate-like paraffin hardens.

[0030] (3) The aggregate-like paraffin obtained in step (2) is immersed in epoxy resin. The mass ratio of epoxy resin to aggregate-like paraffin is 1:2. Stir thoroughly for 3 minutes to ensure that the epoxy resin completely coats the surface of the paraffin.

[0031] (4) The epoxy resin-coated paraffin in step (3) is evenly sprinkled into the cement powder. The mixture is stirred and the fireproof material with epoxy resin adhering to it is effectively separated by filtration. Then it is cured at room temperature for 2 days to obtain ordinary aggregate.

[0032] Test Example: High Temperature Test Results High-temperature tests were conducted on the self-fire-resistant aggregates prepared in Example 1 and Comparative Example 1.

[0033] Test method: (1) Replace the fine aggregate in the UHPC with the obtained self-resistant aggregate in the same proportion to prepare a 150*150*50mm material. 3 A rectangular block was prepared, with a temperature sensor embedded in the center beforehand. The block was then compacted by vibration and cured to the designated age. In Examples 1 and 1, the self-refractory aggregate was replaced with fine aggregate at a replacement rate of 50%.

[0034] (2) Wrap the cubic test block with thermal insulation cotton, except for the temperature measuring surface. Then place it in a muffle furnace for high-temperature treatment. The heating rate is 5℃ / min, and the target temperature is 800℃. Stop heating after the temperature reaches 800℃.

[0035] (3) Draw the temperature curve of the self-fire-resistant aggregate during the heating period.

[0036] Experimental results are as follows Figure 1 As shown.

[0037] Figure 1The graph shows the temperature curves of the self-refractory aggregate in Example 1 and the ordinary aggregate in Comparative Example 1. According to the results, when the furnace temperature rises to 800℃, the center temperature of the UHPC containing the self-refractory aggregate in Example 1 is only about 300℃, while the center temperature of the UHPC containing the ordinary aggregate in Comparative Example 1 is 700℃. Compared to Example 1, the temperature difference between the two is about 400℃ (when the target temperature is reached). This indicates that the fire-retardant material in the self-refractory aggregate can overflow from the aggregate after high temperature, forming a char layer on the surface of the UHPC, hindering temperature transfer and thus providing fire protection.

[0038] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing self-fire-resistant aggregate, characterized in that, Includes the following steps: (1) The fireproof material is placed in molten paraffin and stirred to coat it, thus obtaining a paraffin-coated fireproof material; (2) Cool and air dry the fireproof material wrapped in paraffin obtained in step (1), and finally encapsulate the fireproof material wrapped in paraffin with cement and epoxy resin to obtain self-fire-resistant aggregate.

2. The method for preparing a self-resistant fire-resistant aggregate according to claim 1, characterized in that, In step (1), the fireproof material is mainly composed of a mixture of carbon source, acid source and gas source in a mass ratio of 2-5:2-3:1-3.

3. The method for preparing a self-resistant fire-resistant aggregate according to claim 1, characterized in that, The carbon source is one or more of pentaerythritol, starch, sucrose, and phenolic resin, and the acid source is one or more of ammonium polyphosphate, ammonium phosphate, and zinc borate.

4. The method for preparing a self-resistant fire-resistant aggregate according to claim 1, characterized in that, The gas source is one or more of melamine, dicyandiamide, and urea, mixed together.

5. The method for preparing a self-resistant fire-resistant aggregate according to claim 1, characterized in that, The cooling process in step (2) uses water cooling for 1-3 minutes at room temperature; the air drying process takes 6-10 hours.

6. The method for preparing a self-resistant fire-resistant aggregate according to claim 1, characterized in that, The method of encapsulating the paraffin-coated fireproof material with cement and epoxy resin in step (2) is as follows: (A) Add the paraffin-coated fire-retardant material to the epoxy resin and stir; (B) Pour the paraffin-coated fireproof material obtained in step (A) into the cement powder, stir, and perform a second coating; (C) The self-fire-resistant aggregate after secondary encapsulation in step (B) is cured at room temperature to complete the encapsulation.

7. The method for preparing a self-resistant fire-resistant aggregate according to claim 1, characterized in that, In step (A), the mass ratio of epoxy resin to paraffin-coated fireproof material is 1:2-1:5, and the stirring time is 2-5 minutes.

8. The method for preparing a self-resistant fire-resistant aggregate according to claim 1, characterized in that, The curing time at room temperature in step (C) is 1-3 days.

9. A self-fire-resistant aggregate, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.

10. The application of the self-fire-resistant aggregate according to claim 9 in the preparation of UHPC.

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