Flame-retardant green concrete added with expandable graphite and preparation method of flame-retardant green concrete

Abstract

The invention discloses flame-retardant green concrete added with expandable graphite and a preparation method of the flame-retardant green concrete, and relates to the technical field of fireproof materials. The expansible graphite cement comprises the following components: cement, aggregate, expansible graphite and water, the mass ratio of the water to the cement is (0.4-0.5): 1, and the addition proportion of the expansible graphite is 1%-10% of the total weight of the cement. According to the expansible graphite flame-retardant concrete provided by the invention, the special material expansible graphite is utilized, the fireproof performance and the heat insulation performance of the concrete can be remarkably improved, and the expansible graphite forms a heat insulation layer through expansion in a high-temperature environment, so that concrete cracking or structural damage caused by a fire disaster is effectively prevented; and the fire resistance and the safety of the building structure are obviously improved. The simple and economical production process is designed, the proportion of the expansible graphite to other raw materials is properly adjusted, so that the production process of the concrete is environment-friendly and efficient, meanwhile, the production cost is effectively reduced, the requirements of modern green buildings are met, and wide application prospects are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of fireproof materials, and particularly to a flame-retardant green concrete added with expandable graphite and a preparation method thereof. Background Art

[0002] Expandable graphite flame-retardant concrete is a new type of fireproof material, which is widely used in industries such as construction, transportation, and energy as an excellent fireproof and heat-insulating material. Concrete itself has certain fire resistance, but its fire retardancy performance has limitations in high-temperature environments and cannot meet the requirements of high-fire-risk places. In order to improve the fire resistance of concrete, researchers have gradually used expandable graphite as an additive to enhance its flame-retardant effect. Expandable graphite is a special material that can rapidly expand and form an insulating layer at high temperatures, which can effectively improve the fire resistance and fireproof and heat-insulating effects of concrete in case of fire.

[0003] Currently, there are already some concrete products on the market that use expandable graphite to enhance the flame-retardant performance, but these products generally have problems such as high production costs, unstable expansion effects, and poor sustainability, which limit their application in large-scale construction and engineering projects. Especially under high-temperature fire conditions, the existing expandable graphite flame-retardant concrete may not be able to effectively prevent the concrete from cracking or structural damage, resulting in the inability to achieve the expected fireproof effect. Therefore, we propose a flame-retardant green concrete added with expandable graphite and a preparation method thereof to solve the problems mentioned above.

[0004] The above information disclosed in this background art is only used to increase the understanding of the background art of the present invention. Therefore, it may include prior art that is not known to those of ordinary skill in the art. Summary of the Invention

[0005] The purpose of the present invention is to provide a flame-retardant green concrete added with expandable graphite and a preparation method thereof to solve the problems raised in the above background art.

[0006] To achieve the above purpose, the present invention provides the following technical solution: A flame-retardant green concrete added with expandable graphite, comprising the following components: cement, aggregate, expandable graphite, and water. The mass ratio of water to cement is 0.4 - 0.5:1, and the addition ratio of expandable graphite is 1% - 10% of the total weight of cement.

[0007] Preferably, the cement is one of Portland cement, low-heat cement, and aluminous cement.

[0008] Preferably, the aggregate includes coarse aggregate and fine aggregate. The particle size of the coarse aggregate is above 5mm, and the particle size of the fine aggregate is between 0.15mm and 5mm.

[0009] Preferably, the particle size of the expandable graphite ranges from 0.1 mm to 3 mm.

[0010] Preferably, the mass ratio of the aggregate to cement is 2-4:1.

[0011] The present invention also provides a method for preparing flame-retardant green concrete with added expandable graphite, comprising the following steps:

[0012] Step 1: Surface modification of expandable graphite using a glycidyloxy silane chemical coating to enhance compatibility with concrete;

[0013] Step 2: Weigh cement, aggregate, expandable graphite and water in proportion, mix them thoroughly, and use mechanical stirring or ultrasonic assisted dispersion until the mixture is uniform to ensure that the expandable graphite is fully and evenly distributed in the concrete;

[0014] Step 3: Pour the mixture into the formwork, pour and vibrate to ensure the compactness of the concrete, and cure at 20-30°C for 7-28 days to ensure that the concrete reaches the required strength.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] (1) The present invention provides an expandable graphite flame-retardant concrete. The use of expandable graphite, a special material, can significantly improve the fire resistance and thermal insulation properties of concrete. In a high-temperature environment, the expandable graphite expands to form a thermal insulation layer, thereby effectively preventing fire from causing concrete cracking or structural damage, thereby significantly improving the fire resistance and safety of building structures.

[0017] (2) The present invention ensures that the graphite is evenly distributed in the concrete by optimizing the addition amount and mixing process of expandable graphite, thereby improving the overall fire resistance of the concrete. The concrete not only has a good thermal insulation effect, but also can provide stable structural strength at high temperatures, and is suitable for construction projects with high temperatures or high fire risks.

[0018] (3) The present invention designs a simple and economical production process. By appropriately adjusting the ratio of expandable graphite to other raw materials, the production process of concrete is both environmentally friendly and efficient, while effectively reducing the production cost, meeting the needs of modern green buildings and having broad application prospects.

[0019] The above summary is for illustrative purposes only and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments and features described above, further aspects, embodiments and features of the present invention will be readily apparent by reference to the accompanying drawings and the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the preparation process of the present invention. Specific embodiments

[0021] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0022] A flame-retardant green concrete added with expandable graphite comprises the following components: cement, aggregate, expandable graphite and water.

[0023] The cement is one of portland cement, low-heat cement and aluminate cement. The mass ratio of water to cement is 0.4 - 0.5:1, and the specific water-cement ratio is adjusted according to specific construction requirements, environmental conditions such as temperature and humidity.

[0024] The addition ratio of expandable graphite is 1% - 10% of the total weight of the cement, and the particle size range of expandable graphite is 0.1mm - 3mm. The addition amount of expandable graphite is appropriately adjusted according to different usage requirements and fire risk situations to achieve the best flame-retardant effect.

[0025] The aggregate includes coarse aggregate and fine aggregate. The particle size of the coarse aggregate is above 5mm, and the particle size of the fine aggregate is between 0.15mm - 5mm. The mass ratio of aggregate to cement is 2 - 4:1.

[0026] A preparation method of a flame-retardant green concrete added with expandable graphite comprises the following steps:

[0027] Step 1: Perform surface modification treatment on expandable graphite, using epoxypropoxy silane chemical coating to enhance the compatibility with concrete;

[0028] Step 2: Weigh cement, aggregate, expandable graphite and water in proportion, and conduct sufficient mixing, using mechanical stirring or ultrasonic-assisted dispersion until the mixture is uniform to ensure that expandable graphite is evenly distributed in the concrete;

[0029] Step 3: Pour the mixture into a mold, perform pouring and vibration to ensure the compactness of the concrete, cure at 20 - 30°C, and the curing time is 7 - 28 days to ensure that the concrete reaches the required strength.

[0030] Prepare the following raw materials in parts by weight as the preparation raw materials for Examples 1 - 10 respectively.

[0031] Table 1. Parts by weight of each raw material for Examples 1 - 10

[0032] Item Portland cement / part Aggregate / part Expandable graphite / part Water / part Example 1 1 2.5 0.01 0.5 Example 2 1 2.5 0.02 0.5 Example 3 1 2.5 0.03 0.5 Example 4 1 2.5 0.04 0.5 Example 5 1 2.5 0.05 0.5 Example 6 1 2.5 0.06 0.5 Example 7 1 2.5 0.07 0.5 Example 8 1 2.5 0.08 0.5 Example 9 1 2.5 0.09 0.5 Example 10 1 2.5 0.1 0.5

[0033] Examples 1 - 10 were all prepared according to the following preparation method:

[0034] Step 1: Surface modification treatment was carried out on expandable graphite, and epoxypropoxy silane chemical coating was used to enhance the compatibility with concrete;

[0035] Step 2: Cement, aggregate, expandable graphite and water were weighed in proportion and thoroughly mixed. Mechanical stirring or ultrasonic-assisted dispersion was used until the mixture was uniform to ensure that the expandable graphite was evenly distributed in the concrete;

[0036] Step 3: The mixture was poured into a mold, poured and vibrated to ensure the compactness of the concrete. Specimens of different specifications were made according to requirements, cured at 20 ± 2 °C with a humidity ≥ 95% for 28 days to ensure that the concrete reached the required strength.

[0037] Performance test

[0038] 1. Compressive strength test:

[0039] Specimen: 150 mm × 150 mm × 150 mm cube test block was used.

[0040] Testing equipment: Universal material testing machine (range ≥ 2000 kN).

[0041] Loading rate: 0.5 - 1.0 MPa / s until the specimen was damaged.

[0042] Data recording: Record the failure load and calculate the compressive strength ( A is the compression area).

[0043] 2. Flexural strength test:

[0044] Specimen: 150 mm × 150 mm × 600 mm prism test block was used.

[0045] Testing equipment: Universal testing machine equipped with a three-point bending fixture.

[0046] Loading rate: 0.05 - 0.08 MPa / s, span 450 mm.

[0047] Data recording: Record the failure load and calculate the flexural strength ( L is the span, b and h are the width and height of the specimen).

[0048] 3. Differential thermal analysis:

[0049] Instrument: Differential thermal analyzer (such as NETZSCH STA 449).

[0050] Parameter settings:

[0051] Heating rate: 10 °C / min, temperature range: room temperature - 1000 °C.

[0052] Reference material: α-Al2O3, sample mass: 10 - 20 mg.

[0053] Atmosphere: nitrogen or air (flow rate 50 mL / min).

[0054] Record key indicators: decomposition temperature (initial weight loss temperature), exothermic peak temperature (reflecting the intensity of combustion).

[0055] 4. Oxygen index test:

[0056] Specimen size: 100 mm × 10 mm × 4 mm long strip specimen, with a flat surface and no cracks.

[0057] Testing equipment: oxygen index tester (such as JF-3 type).

[0058] Testing process:

[0059] Ignite the top of the specimen in a nitrogen-oxygen mixed gas stream, adjust the oxygen concentration, and record the lowest oxygen concentration (i.e., oxygen index, LOI) when the specimen continues to burn for 3 min or the damaged length ≤ 50 mm.

[0060] Test 5 specimens in each group and take the average value.

[0061] The results of each test are shown in the following table.

[0062] Item Compressive strength / MPa Flexural strength / MPa Decomposition temperature / °C Reduction of exothermic peak area / % Oxygen index / % Example 1 49 5.6 280 ≥30％ 25.7 Example 2 50 5.9 293 ≥30％ 27.3 Example 3 51 6.1 302 ≥30％ 28.2 Example 4 49 6.1 307 ≥30％ 29.4 Example 5 47 5.9 305 ≥30％ 30.1 Example 6 46 5.8 304 ≥30％ 30.5 Example 7 44 5.8 306 ≥30％ 30.8 Example 8 43 5.7 302 ≥30％ 30.4 Example 9 42 5.6 303 ≥30％ 30.2 Example 10 42 5.5 304 ≥30％ 30.1

[0063] As can be seen from the above, the compressive strength of the concrete of the present invention can reach 42 MPa and above, indicating that the compressive strength is relatively excellent, and when the addition amount of expandable graphite is 0.03, the compressive strength reaches the highest; the flexural strength can reach 5.5 MPa and above, indicating that the flexural strength is relatively excellent, and when the addition amount of expandable graphite is 0.03 - 0.04, the flexural strength reaches the highest; the decomposition temperature of ordinary concrete is about 250 °C, the decomposition temperature of the concrete of the present invention can reach 280 °C and above, and when the addition amount of expandable graphite is 0.03 - 0.1, the decomposition temperature can reach above 300 °C, indicating that the thermal stability of the material is good; the reduction of the exothermic peak area is more than 30% compared with ordinary concrete, indicating that the present invention can effectively inhibit combustion heat release; the oxygen index of ordinary concrete ≈ 23% (oxygen concentration in air 21%, flammable), the oxygen index of the concrete of the present invention can reach 25.7, and when the addition amount of expandable graphite is 0.05 - 0.1, the oxygen index ≥ 30%, meeting the UL94 V-0 level flame retardant standard (self-extinguishing from fire, no melting droplets).

[0064] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", "examples", "specific examples", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0065] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A flame-retardant green concrete added with expandable graphite, characterized in that, The invention comprises the following components: cement, aggregate, expandable graphite and water, wherein the mass ratio of water to cement is 0.4-0.5:1, and the adding ratio of expandable graphite is 1%-10% of the total weight of cement.

2. The flame-retardant green concrete adding expandable graphite according to claim 1, wherein: The cement is one of silicate cement, low heat cement and aluminate cement.

3. A flame-retardant green concrete adding expandable graphite according to claim 1, characterized in that: The aggregate includes coarse aggregate and fine aggregate. The particle size of the coarse aggregate is above 5 mm, and the particle size of the fine aggregate is between 0.15 mm and 5 mm.

4. A flame-retardant green concrete added with expandable graphite according to claim 1, characterized in that: The particle size of the expandable graphite ranges from 0.1 mm to 3 mm.

5. A flame-retardant green concrete adding expandable graphite according to claim 1, characterized in that: The mass ratio of the aggregate to cement is 2-4:

1.

6. The preparation method of a flame-retardant green concrete added with expandable graphite according to any one of claims 1-5, characterized in that, The steps include: Step 1: Surface modification of expandable graphite using a glycidyloxy silane chemical coating to enhance compatibility with concrete; Step 2: Weigh cement, aggregate, expandable graphite and water in proportion, mix them thoroughly, and use mechanical stirring or ultrasonic assisted dispersion until the mixture is uniform to ensure that the expandable graphite is fully and evenly distributed in the concrete; Step 3: Pour the mixture into the formwork, pour and vibrate to ensure the compactness of the concrete, and cure at 20-30°C for 7-28 days to ensure that the concrete reaches the required strength.

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