A special cementitious material for microwave heating concrete and its preparation method and application

Abstract

The invention discloses a special cementitious material for microwave-heated concrete, a preparation method thereof, and an application thereof, relating to the technical field of building materials. The cementitious material comprises components such as fly ash, steel slag, high-iron phase Portland cement clinker, high-belite sulfate cement clinker, gypsum, waste residue, solid waste, graphene, palmitic acid, and a water reducer. The high-iron phase Portland cement clinker contains more than 20% tetracalcium aluminoferrate and less than 3% tricalcium aluminate; the high-belite sulfate cement clinker contains more than 45% dicalcium silicate and 30-50% calcium sulfoaluminate. The cementitious material is made from specific solid waste, has excellent compressive strength, low resistivity, and high microwave heating efficiency, and can be used to prepare microwave-heated concrete.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials, and more particularly to a special gelling material for microwave-heated concrete, a preparation method thereof, and an application thereof. Background Art

[0002] China has a vast territory and complex meteorological conditions. Some areas in the north are in winter for a long time, and some high-altitude areas are also in a freezing period all year round. Due to the influence of long-term low temperatures, the residual rainwater on the road surface condenses into ice, which greatly reduces the friction coefficient of the road surface and puts great pressure on traffic safety. At present, the three commonly used deicing methods in deicing operations are removal, melting and suppression. They have played a certain role in clearing ice from the road surface, but there are also some problems in their use, such as high-temperature airflow causing great damage to the road surface, low energy utilization rate, and serious environmental pollution. Therefore, in order to adapt to the development needs of road traffic in the new era and improve road safety performance, it is imperative to develop a new deicing method.

[0003] Microwave deicing technology is a recently developed new deicing technology. Compared to traditional deicing methods, it offers several advantages: high ice removal rates, effective thick ice removal, and environmentally friendly greening. It holds great promise for winter road deicing. Microwave deicing has been proposed since the 1970s, but has not been widely adopted in practice. This is primarily due to its low efficiency, which makes it difficult to meet the needs of practical deicing operations.

[0004] Therefore, to improve the deicing efficiency of microwave deicing methods, researchers both in China and abroad have conducted extensive research on microwave heating technology and microwave deicing efficiency. Internationally, within the Strategic Highway Research Program (SHRP) of the US Federal Highway Administration, researchers such as Lindroth et al., Ye et al., Gao et al., and the Natural Resources Research Institute (NRRI) in Minnesota have conducted in-depth research on microwave deicing technology. However, due to its low efficiency, it has been rarely used in practical operations. While some research on microwave deicing technology has been conducted in China, most of it has focused on the development of microwave heating devices, with relatively little research on the microwave heating mechanism.

[0005] In 2003, Li Xiao et al., Guan Minghui et al., and others first proposed the concept of using microwave deicing technology for road deicing in China. They designed a microwave deicing vehicle model and applied for two patents for microwave deicing. In 2012, Guo Dedong et al. used magnetite, a mineral with strong microwave absorption, instead of conventional aggregate to study the mix design of magnetite asphalt concrete, the heating mechanism of microwaves and magnetite, and the microwave deicing efficiency and process of magnetite asphalt pavements. In 2016, Lu Song et al. studied the microwave deicing performance of airport concrete pavements, analyzing the effects of microwave frequency and pavement material properties on the efficiency of microwave deicing. In general, existing research has primarily focused on microwave deicing materials, microwave frequencies, and microwave radiator design, but lacks analysis of the practical application of microwave deicing methods. This requires in-depth research on the height of the radiator port. Furthermore, some studies have used relatively simple experimental equipment and lacked systematic design.

[0006] In order to better solve the application difficulties of microwave-heated concrete in road deicing, the present invention provides a special cementitious material for microwave-heated concrete, its preparation method, and application. The cementitious material is made from specific solid waste and has excellent compressive strength, low resistivity, and high microwave heating efficiency, and can be used to prepare microwave-heated concrete. Summary of the Invention

[0007] The purpose of the present invention is to provide a special cementitious material for microwave-heated concrete, and its preparation method and application. The cementitious material is made from specific solid waste and has excellent compressive strength, low resistivity and high microwave heating efficiency, and can be used to prepare microwave-heated concrete.

[0008] The present invention is achieved through the following technical solutions:

[0009] A special cementitious material for microwave-heated concrete, comprising the following components in parts by mass:

[0010] 5-10 parts fly ash;

[0011] 30-45 parts of steel slag;

[0012] 30-45 parts of high iron phase Portland cement clinker;

[0013] 5-10 parts of high-belite sulfate cement clinker;

[0014] 5-10 parts of gypsum;

[0015] 2-4 parts of waste residue;

[0016] 3-5 parts of solid waste;

[0017] 0.1-0.5 parts of graphene;

[0018] Palmitic acid 0.5-1.5 parts;

[0019] 0.5-1.5 parts of water reducing agent;

[0020] The high iron phase Portland cement clinker contains more than 20% of tetracalcium aluminate and less than 3% of tricalcium aluminate;

[0021] The dicalcium silicate content in high-belite sulfate cement clinker is greater than 45%, and the calcium sulfoaluminate content is 30-50%.

[0022] Furthermore, the fly ash is the bottom ash collected by the flue gas purification system during the waste incineration process and the bottom ash settled at the bottom of the flue and chimney. The specific surface area of ​​the fly ash is 600-1000m 2 / kg, calcium content is greater than 35%.

[0023] Furthermore, the gypsum is desulfurized gypsum, and the content of calcium sulfate dihydrate in the desulfurized gypsum is greater than 94%, and the content of calcium carbonate is greater than 1%.

[0024] Furthermore, the waste residue is waste residue generated during alkali production or alkali treatment, and the content of sodium hydroxide and potassium hydroxide in the waste residue is greater than 5%.

[0025] Furthermore, the solid waste is dust collected during limestone crushing production, and the specific surface area of ​​the solid waste is 500-800m 2 / kg.

[0026] Furthermore, the graphene is multilayer graphene with a layer number greater than 15, and the particle size of the graphene is 0.05-2 mm.

[0027] Furthermore, the palmitic acid is industrial-grade palmitic acid with a melting point of less than 63° C. and a purity greater than 98%.

[0028] Furthermore, the water reducer is a polycarboxylate water reducer with a water reduction rate greater than 45%.

[0029] A method for preparing the aforementioned microwave-heated concrete cementitious material comprises the following steps:

[0030] Ⅰ. Prepare the raw materials according to the aforementioned composition ratio and set aside;

[0031] Ⅱ. Take steel slag, high iron phase silicate cement clinker, high belite sulfate cement clinker and palmitic acid and put them into steel ball mill for grinding. Grind to a specific gravity of 270-320m 2 / kg, 45μm sieve residue is greater than 15%, to obtain mixed material 1;

[0032] III. Take the waste residue and graphene and mix them thoroughly, add water until the mixed material is covered, stir thoroughly for 8-12 hours, and then directly dry to obtain the second mixed material for standby use;

[0033] IV. Take fly ash, gypsum, solid waste, and water reducer, and fully mix them with mixture 1 and mixture 2 to obtain a special cementitious material for microwave heating.

[0034] The use of a special cementitious material for microwave heating as described in any of the preceding claims in the preparation of microwave-heated concrete.

[0035] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0036] First, the present invention utilizes a large amount of solid waste, such as fly ash, steel slag, desulfurized gypsum, caustic soda waste residue, and limestone crushing dust, significantly reducing the cost of cementitious materials and achieving energy conservation and emission reduction. Furthermore, by controlling the grinding particle size, the energy consumption of clinker grinding is reduced. Using fly ash and limestone crushing dust to supplement the fine particles in the cementitious material achieves continuous gradation of the cementitious material, improves density, reduces harmful pores, and ensures strength while reducing water demand and the amount of water-reducing agent used.

[0037] 2. In the present invention, the energy consumption of grinding is further reduced by adding palmitic acid to aid grinding during the grinding process. As the temperature rises during the grinding process, the palmitic acid undergoes phase change and absorbs heat, thereby reducing the material temperature, ensuring grinding efficiency, and reducing safety hazards. Palmitic acid can also help concrete prevent corrosion, improve sealing performance, and enhance the comprehensive performance of concrete.

[0038] 3. In the present invention, calcium sulfoaluminate in high-belite sulfoaluminate cement clinker is used to provide early strength, reducing curing time and curing cost; high-iron phase Portland cement clinker is used to improve durability and supplement late strength; sulfate excitation and alkali excitation are used together to act on fly ash and steel slag to supplement strength; graphene is combined to form fibers to improve crack resistance and overall strength, thereby achieving a cementitious material with high early strength, guaranteed late strength, good durability and strong crack resistance; in addition, high-belite sulfoaluminate cement data and high-iron phase ordinary Portland cement clinker both have good high temperature resistance, and can also ensure overall stability during the heating process.

[0039] 4. In the present invention, graphene is intercalated with caustic soda waste residue, so that sodium hydroxide, sodium carbonate, sodium chloride and oxides such as iron and aluminum in the caustic soda waste residue enter the graphene interlayer. The treated graphene has ionic polarity. In addition, fly ash, high-iron phase ordinary Portland cement clinker, high-belite sulfoaluminate cement clinker, steel slag, desulfurization gypsum, and caustic soda waste residue are all polar materials, which can be used to achieve self-heating of concrete, melt ice and snow, or be used in other scenarios requiring heating through microwaves.

[0040] 5. In the present invention, graphene itself can achieve good electrical conductivity through electronic conduction, and after combined with oxidation intercalation treatment, it has ionic conductivity. Fly ash, limestone powder, etc. enter the graphite layer, and react with the alkali between the layers to produce alkaline excitation reaction, which can also fix the interlayer ions and achieve conductive stability. Other substances such as steel slag and fly ash also have certain electrical conductivity. The prepared gel material has good electrical conductivity, and electric heating can be used as compensation to ensure the heating performance of the material together with microwave heating.

[0041] Sixth, the present invention also reduces energy consumption and ensures long-term concrete stability during the heating process through the phase transition of palmitic acid. During off-peak periods, heating causes the palmitic acid to melt, absorbing and storing a large amount of heat. During peak periods, the palmitic acid solidifies and releases heat, reducing operating time during peak periods. Furthermore, at higher temperatures, the palmitic acid melts, leaving room for deformation during concrete heating and preventing concrete cracking. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 Schematic diagram of the structure of graphite intercalation. DETAILED DESCRIPTION

[0043] The present invention will be further described in detail below with reference to the examples, but the embodiments of the present invention are not limited thereto.

[0044] In the present invention, the high-iron phase Portland cement clinker has a tetracalcium aluminoferrate content greater than 20% and a tricalcium aluminate content less than 3%. In the following examples, ordinary Portland cement clinker having a tetracalcium aluminoferrate content of 22% and a tricalcium aluminate content of 2.8% is used as an example of the high-iron phase Portland cement clinker.

[0045] In the present invention, the dicalcium silicate content in the high-belite sulfate cement clinker is greater than 45%, and the calcium sulfoaluminate content is 30-50%. In the following embodiments, the high-belite sulfate cement clinker is illustrated by taking the high-belite sulfoaluminate cement clinker produced by Jiahua Special Cement Co., Ltd. as an example.

[0046] In the present invention, the fly ash is the bottom ash collected by the flue gas purification system during the waste incineration process and the bottom ash settled at the bottom of the flue and chimney. The specific surface area of ​​the fly ash is 600-1000m 2 / kg, and the calcium content is greater than 35%. In the following examples, fly ash is taken as fly ash produced by Everbright Environmental Energy (Leshan) Co., Ltd.

[0047] In the present invention, the gypsum is desulfurized gypsum, wherein the calcium sulfate dihydrate content in the desulfurized gypsum is greater than 94% and the calcium carbonate content is greater than 1%. In the following embodiments, the desulfurized gypsum produced by Sichuan Desheng Iron and Steel Co., Ltd. is used as an example for illustration.

[0048] In the present invention, the waste residue is waste residue generated during alkali production or alkali treatment, and the content of sodium hydroxide and potassium hydroxide in the waste residue is greater than 5%. In the following embodiments, the waste residue is illustrated by taking waste residue with a sodium hydroxide and potassium hydroxide content of about 8% as an example.

[0049] In the present invention, the solid waste is dust collected during the limestone crushing production process, and the specific surface area of ​​the solid waste is 500-800m 2 In the following examples, the solid waste has a specific surface area of ​​about 750m 2 / kg of limestone dust as an example.

[0050] In the present invention, the graphene is multilayer graphene with a number of layers greater than 15, and the particle size of the graphene is 0.05-2 mm. In the following embodiments, the graphene is illustrated by taking the multilayer graphene produced by Nantong Qiangsheng Graphene Technology Co., Ltd. as an example.

[0051] In the present invention, the palmitic acid is industrial-grade palmitic acid having a melting point of less than 63° C. and a purity of greater than 98%. In the following examples, the palmitic acid is industrial-grade palmitic acid supplied by Shanghai Kabo Industry and Trade Co., Ltd., for example.

[0052] In the present invention, the water reducing agent is a polycarboxylate water reducing agent having a water reducing rate greater than 45%. In the following embodiments, Sika 556P is used as an example of the water reducing agent to illustrate the effect of this solution.

[0053] Example 1

[0054] A special cementitious material for microwave-heated concrete relates to the technical field of building materials. Calculated by mass fraction of each group in Table 1, the material comprises the following components.

[0055] The preparation method of a special cementitious material for microwave heating concrete comprises the following steps:

[0056] Ⅰ. Prepare the raw materials according to the composition ratio of each group in Table 1 and set aside;

[0057] II. Steel slag, high iron phase Portland cement clinker, high belite sulfate cement clinker, and palmitic acid were put into a steel ball mill for grinding until the specific surface area and 45 μm sieve residue were as shown in Table 2, thereby obtaining a mixture 1;

[0058] III. Take the waste residue and graphene and mix them thoroughly, add water until the mixed material is covered, stir for a certain time (see Table 2), and then directly dry to obtain the second mixed material for standby use;

[0059] IV. Take fly ash, gypsum, solid waste, and water reducer, and fully mix them with mixture 1 and mixture 2 to obtain a special cementitious material for microwave heating.

[0060] Table 1

[0061]

[0062] Table 2

[0063]

[0064] Comparative Example 1

[0065] Compared with the first group of Example 1, the only difference between this comparative example and the first group of Example 1 is that

[0066] The fly ash and solid waste were replaced with steel slag of equal mass, and the rest of the process conditions remained unchanged.

[0067] Comparative Example 2

[0068] Compared with the first group of Example 1, the only difference between this comparative example and the first group of Example 1 is that

[0069] Palmitic acid was replaced by high-belite sulphoaluminate cement clinker of equal mass, and the other process conditions remained unchanged.

[0070] Comparative Example 3

[0071] Compared with the first group of Example 1, the only difference between this comparative example and the first group of Example 1 is that

[0072] The high-belite sulphoaluminate cement clinker and high-iron phase Portland cement clinker were replaced with steel slag of equal mass, and the other process conditions remained unchanged.

[0073] Comparative Example 4

[0074] Compared with the first group of Example 1, the only difference between this comparative example and the first group of Example 1 is that

[0075] The caustic soda waste residue was replaced by solid waste of the same mass, and the other process conditions remained unchanged.

[0076] Comparative Example 5

[0077] The only difference between this comparative example and the second group of Example 1 is that

[0078] The fly ash and solid waste were replaced by steel slag of equal mass, the water reducer was replaced by desulfurization gypsum of equal mass, and the other process conditions remained unchanged.

[0079] Referring to the national standard GB 175-2023 "General Portland Cement", the relevant properties of the special cementitious material for microwave-heated concrete and the cementitious materials of Comparative Examples 1-5 were tested, and the microwave heating efficiency and resistivity of the formed slurry were tested.

[0080] The microwave heating efficiency is to prepare the gelling material into a 100*100*100mm pure pulp block, and place the pure pulp block into a KQ6000 adjustable industrial box-type microwave heating device with a power of 20kW and a frequency of 2.45GHz. The temperature is recorded after heating for ten minutes. The results are shown in the following table.

[0081] Table 3

[0082]

[0083] As shown in Table 3, the cementitious material obtained by adopting this scheme has excellent properties such as high early strength, high late strength, good electrical conductivity, high microwave heating efficiency, and good construction performance.

[0084] By comparing the first group of Example 1 with Comparative Example 1, it can be seen that fly ash and solid waste can make the particle gradation of the cementitious material denser, improve the early and late strength, and the fine powder as the crystal nucleus can improve the early strength and reduce the setting time. At the same time, fly ash can also reduce the resistivity of the material and improve the conductivity.

[0085] From the comparison between the first group of Example 1 and Comparative Example 2, it can be seen that palmitic acid can improve the grinding efficiency and improve the particle gradation, and the voids after the palmitic acid is heated and melted can increase the microwave heating performance.

[0086] From the comparison of the first group of Example 1 and Comparative Example 3, it can be seen that the combination of high-belite sulphoaluminate cement clinker and high-iron phase Portland cement clinker can effectively shorten the setting time, improve the early strength, and at the same time reduce the water demand of the cementitious material.

[0087] From the comparison between the first group of Example 1 and Comparative Example 4, it can be seen that caustic soda waste slag can stimulate the activity of steel slag to improve the early and late strength, and caustic soda waste slag can also reduce the resistivity by intercalating graphene or conducting its own polarity.

[0088] From the comparison between the first group of Example 1 and Comparative Example 5, it can be seen that the fly ash, solid waste and cementitious material form a relatively complete gradation. By further reducing the water demand of the material by the water reducer, the setting time can be effectively shortened and the early and late strengths can be improved.

[0089] Application Example 1

[0090] Concrete was prepared using the cementitious materials from each group in Example 1 and Comparative Examples 1-5, along with aggregate and water. The mix proportions are shown in Table 4. The compressive strength of the concrete after a standard 28-day curing period was tested in accordance with GB / T 50107-2010, "Standard for Testing and Assessment of Concrete Strength." The air content and slump of the concrete were tested in accordance with GB 50204-2015, "Code for Acceptance of Construction Quality of Concrete Structures." The resistivity of the concrete was tested in accordance with ASTM C177-18. The microwave heating performance was tested by placing a standard test block after a standard 28-day curing period in a KQ6000 adjustable industrial box-type microwave heating device at a power of 20 kW and a frequency of 2.45 GHz. The temperature was recorded after ten minutes of heating. The test results are shown in Table 5.

[0091] Table 4: Concrete mix proportions

[0092]

[0093] The coarse aggregate is a continuously graded limestone aggregate with a particle size of 2-5 mm; the fine aggregate is a continuously graded limestone sand with a particle size of 0-2 mm; and the water is tap water.

[0094] Table 5

[0095]

[0096] Table 5 shows that fly ash and solid waste can effectively fill the fine voids within concrete, forming a precise accumulation, reducing water demand and increasing concrete strength and workability. Furthermore, fly ash particles are small and can hydrate quickly. The hydration products and solid waste together serve as crystal nuclei to improve early strength. Palmitic acid can effectively improve grinding efficiency and make the particle size distribution of the powder more reasonable, thereby increasing concrete strength. A combination of high-belite sulfoaluminate cement clinker and high-iron silicate cement clinker can effectively shorten the setting time and is also the main source of strength. Compared with steel slag, they can also reduce the water demand of the cementitious material, reduce the porosity in the concrete, and thus reduce the resistivity. Caustic soda waste slag can stimulate the activity of steel slag, improving early and late strength. Caustic soda waste slag can also reduce resistivity through graphene intercalation or its own polar conductivity. Caustic soda waste slag can also improve microwave heating performance. Water reducers are crucial in the material, effectively reducing the water demand and significantly reducing porosity. Combined with the filling benefits of fly ash and solid waste, they can significantly increase concrete strength and reduce resistivity.

[0097] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A special cementitious material for microwave heating concrete, characterized in that: Calculated by mass, it includes the following components: 5-10 parts fly ash; 30-45 parts of steel slag; 30-45 parts of high iron phase Portland cement clinker; 5-10 parts of high-belite sulphoaluminate cement clinker; 5-10 parts of gypsum; 2-4 parts of waste residue; 3-5 parts of solid waste; 0.1-0.5 parts of multilayer graphene with more than 15 layers; Palmitic acid 0.5-1.5 parts; 0.5-1.5 parts of water reducing agent; The high iron phase Portland cement clinker contains more than 20% of tetracalcium aluminate and less than 3% of tricalcium aluminate; The dicalcium silicate content in high-belite sulphoaluminate cement clinker is greater than 45%, and the calcium sulphoaluminate content is 30-50%; The solid waste is dust collected during the limestone crushing production process; The waste residue is waste residue generated during alkali production or alkali treatment.

2. The special cementitious material for microwave-heated concrete according to claim 1, characterized in that: The fly ash is collected by the flue gas purification system during the waste incineration process, and the specific surface area of ​​the fly ash is 600-1000m 2 / kg, calcium content is greater than 35%.

3. The special cementitious material for microwave-heated concrete according to claim 1, characterized in that: The gypsum is desulfurized gypsum, and the content of calcium sulfate dihydrate in the desulfurized gypsum is greater than 94%, and the content of calcium carbonate is greater than 1%.

4. The special cementitious material for microwave-heated concrete according to claim 1, characterized in that: The content of sodium hydroxide and potassium hydroxide in the waste residue is greater than 5%.

5. The special cementitious material for microwave-heated concrete according to claim 1, characterized in that: The specific surface area of ​​the solid waste is 500-800m 2 / kg.

6. The special cementitious material for microwave-heated concrete according to claim 1, characterized in that: The palmitic acid is industrial-grade palmitic acid with a melting point of less than 63° C. and a purity of more than 98%.

7. The special cementitious material for microwave-heated concrete according to claim 1, characterized in that: The water reducer is a polycarboxylate water reducer with a water reduction rate greater than 45%.

8. A method for preparing a special cementitious material for microwave heating concrete as claimed in claim 1, characterized in that: The steps include: I. Prepare the raw materials according to the composition ratio of claim 1 and set aside; Ⅱ. Take steel slag, high iron phase silicate cement clinker, high belite sulphoaluminate cement clinker and palmitic acid and put them into steel ball mill for grinding until the specific surface area is 270-320m 2 / kg, 45μm sieve residue is greater than 15%, to obtain mixed material 1; III. Take the waste residue and multilayer graphene with more than 15 layers and mix them thoroughly, add water until the mixed material is covered, stir thoroughly for 8-12 hours, and then directly dry to obtain a second mixed material for standby use; IV. Take the fly ash, gypsum, the solid waste, and the water reducer, and fully mix them with the mixture 1 and the mixture 2 to obtain a special cementitious material for microwave-heated concrete.

9. Use of the cementitious material according to any one of claims 1 to 7 or the cementitious material obtained by the preparation method according to claim 8 in preparing microwave-heated concrete.

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