Low-carbon, unburned fly ash ceramsite concrete and preparation method thereof

Abstract

The present invention discloses a low-carbon, unburned fly ash ceramsite concrete. The components and their weight percentages include: 160-220 parts of cement, 70-130 parts of fly ash, 60-80 parts of mineral powder, 750-950 parts of sand, 550-750 parts of low-carbon, unburned fly ash ceramsite, 130-160 parts of water, and 2-5 parts of a water reducer. The low-carbon, unburned fly ash ceramsite is granulated using cement-based composite cementitious material, modified sodium alginate, and lime water as main raw materials. The low-carbon, unburned fly ash ceramsite of the present invention has the advantages of light weight, high strength, and low porosity. When used to prepare carbon-free, unburned fly ash ceramsite concrete, it can achieve good low density, high strength, and good durability. The preparation method involved is relatively simple, low-cost, environmentally friendly, and suitable for promotion and application.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials, and particularly relates to a low-carbon, unburned fly ash ceramsite concrete and a preparation method thereof. Background Art

[0002] Fly ash, the fine dust captured from the flue gases after coal combustion, is the primary solid waste emitted by coal-fired power plants. It is primarily used in the construction and building materials, transportation, water conservancy, metallurgy, chemical industry, agriculture, and environmental protection sectors. Ceramsite production is a key utilization method for fly ash. Fly ash ceramsite, with its lightweight and high strength, is widely used in lightweight concrete. Fly ash ceramsite can be prepared using two methods: sintered and unsintered. The high cost and low environmental impact of sintered fly ash ceramsite limit its widespread application.

[0003] Unfired porous fly ash ceramsite is a new lightweight aggregate developed in recent years that can significantly reduce energy consumption and realize the resource utilization of fly ash. Furthermore, unfired fly ash ceramsite offers advantages such as thermal insulation, fire resistance, and sound absorption, making it a trend in ceramsite production. However, the strength of existing unfired fly ash ceramsite primarily relies on the effects of additives and curing agents, and its mechanical properties (such as compressive and flexural strength) may be inferior to those of traditional fired ceramsite, limiting its application in certain high-strength construction applications.

[0004] At present, the enhancement technology of fly ash ceramsite mainly focuses on two aspects: (1) alkali activation technology: using alkaline activators (such as sodium hydroxide, sodium silicate, etc.) to activate the active components in fly ash, generating gel-like products through chemical reactions, thereby forming ceramsite with certain strength and stability; however, the cost of alkaline activators such as sodium hydroxide and sodium silicate is high, which increases production costs, and alkaline activators are corrosive, requiring protective measures, increasing process complexity and equipment maintenance costs; in addition, the activation reaction is highly sensitive to raw materials, and fluctuations in raw material quality can easily affect the performance and quality of the final product; (2) polymer modification technology: by adding polymers (such as polyvinyl alcohol, polyacrylic acid, etc.) and mixing them with fly ash, solidifying them at room temperature to form ceramsite with certain strength and durability; however, some polymers may cause aging and degradation during long-term use, affecting the weather resistance and durability of ceramsite. Further exploration of green unfired ceramsite with high strength and low porosity has become a technical problem that needs to be solved urgently. Summary of the Invention

[0005] The main purpose of the present invention is to address the problems and shortcomings of the existing technology, provide a green unburned ceramsite with high strength and low porosity, and apply it to the preparation of carbon-unburned fly ash ceramsite concrete, which can take into account good low density, high strength and good durability; and the preparation method involved is relatively simple, low cost, environmentally friendly, and suitable for promotion and application.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] A low-carbon, unburned fly ash ceramsite concrete comprises the following components and their weight proportions: 160-220 parts of cement, 70-130 parts of fly ash, 60-80 parts of mineral powder, 750-950 parts of sand, 550-750 parts of low-carbon, unburned fly ash ceramsite, 130-160 parts of water, and 2-5 parts of a water reducer. The low-carbon, unburned fly ash ceramsite is obtained by granulating a cement-based composite cementitious material, modified sodium alginate, and lime water as main raw materials.

[0008] In the above solution, the cement is ordinary Portland cement, and its strength grade is above 42.5.

[0009] In the above scheme, the fly ash is of Class F II, with a specific surface area of ​​320-400m 2 / kg.

[0010] In the above scheme, the mineral powder is S75 grade with a specific surface area of ​​500-800m 2 / kg.

[0011] In the above solution, the particle size of the low-carbon, unburned fly ash ceramsite is 5 to 15 mm.

[0012] In the above scheme, the components and their weight proportions in the low-carbon unburned fly ash ceramsite include: 60-75 parts of cement-based composite gelling material, 10-20 parts of modified sodium alginate, and 5-15 parts of lime water.

[0013] In the above solution, the cement-based composite cementitious material includes ordinary Portland cement, silica fume and fly ash; the components and their mass percentages include: ordinary Portland cement 5-8%, silica fume 6-10%, and fly ash 82-89%.

[0014] Furthermore, in the cement-based composite cementitious material, the strength grade of ordinary Portland cement is above 42.5; the specific surface area of ​​silica fume is 13000~30000m 2 / kg, SiO2 content 85-97%; fly ash is F class II, with a specific surface area of ​​320-400m 2 / kg.

[0015] In the above scheme, the modified sodium alginate is obtained by mixing sodium alginate and chitin nanogel, performing ultrasonic dispersion treatment, and then vacuum drying.

[0016] In the above solution, the mass ratio of sodium alginate to chitin nanogel is 1:0.5-1.34.

[0017] In the above solution, the chitin nanogel has a particle size of 50 to 150 nm, a polydispersity index of 0.2 to 0.3, and a Zeta potential of 45 to 50 mV.

[0018] In the above scheme, the ultrasonic dispersion treatment uses an ultrasonic frequency of 1500 to 2000 Hz and a duration of 0.5 to 1 hour. The present invention prepares modified sodium alginate by ultrasonically dispersing sodium alginate and chitin nanogel and then vacuum drying. Ultrasonic dispersion ensures uniform mixing of the two substances while promoting stronger adsorption of the chitin nanogel on the sodium alginate. This results in improved pelletization efficiency for the modified sodium alginate. The incorporation of the chitin nanogel enhances the toughness and strength of the modified sodium alginate, improving the overall strength of the resulting low-carbon, unburned fly ash ceramsite. Simultaneously, drying is performed in a vacuum environment, which, while evaporating water, further enhances the adsorption of the chitin nanogel by the sodium alginate and reduces the density of the modified sodium alginate.

[0019] In the above scheme, the drying adopts a vacuum drying process, the drying temperature adopted is 30-40°C, the drying time is 12-18h, and the vacuum degree is 80-90kPa.

[0020] In the above scheme, the lime water is obtained by mixing lime and water in a mass ratio of 1:1.5 to 4.

[0021] In the above scheme, the granulation step adopts a disc ball forming machine with an inclination angle of 30 to 50 degrees and a rotation speed of 30 to 50 r / min; it stops after the powder is completely formed (10 to 20 minutes) to obtain the low-carbon and unburned fly ash ceramsite.

[0022] Furthermore, after granulation, the obtained ceramsite is cured, specifically, curing at room temperature for 25 to 30 days under the condition of humidity not less than 95%.

[0023] In the above scheme, the sand is natural sand with a fineness modulus of 2.3 to 2.7; it belongs to the medium sand in the second zone.

[0024] In the above solution, the water reducing agent is a polycarboxylic acid water reducing agent with a water reduction rate of 25-35%.

[0025] The method for preparing the low-carbon, unburned fly ash ceramsite concrete comprises the following steps:

[0026] 1) Weighing the raw materials; the raw materials and their weight proportions include: 160-220 parts of cement, 70-130 parts of fly ash, 60-80 parts of mineral powder, 750-950 parts of sand, 550-750 parts of low-carbon unburned fly ash ceramsite, 130-160 parts of water, and 2-5 parts of water reducer;

[0027] 2) The weighed cement, fly ash, mineral powder, low-carbon unburned fly ash ceramsite, sand, water and water reducing agent are mixed evenly to obtain the low-carbon unburned fly ash ceramsite concrete.

[0028] The principle of the present invention is:

[0029] 1) The modified alginic acid of the present invention has good compatibility with other powders, can effectively promote the densification and uniformity of the resulting mixture during the molding process, promote the production of fly ash-free ceramsite with excellent mechanical properties and lightweight characteristics, and has good economic and environmental benefits;

[0030] In addition, the modified sodium alginate described in the present invention can promote cement-based composite cementitious materials to achieve a better bonding effect, make it easy for various powders to agglomerate and form, and improve the molding efficiency of fly ash unfired ceramsite; at the same time, the fly ash unfired ceramsite prepared by using modified sodium alginate as the core (modified sodium alginate forms a viscous solution when it meets water, increases the adsorption effect on the cementitious material particles, and promotes the adsorption of the cementitious material particles on the surface of the viscous solution) has higher strength and toughness, which can effectively solve the shortcomings of sodium alginate such as high hardness and brittleness; making the obtained fly ash unfired ceramsite lighter and stronger and tougher.

[0031] 2) The low-carbon, unburned fly ash ceramsite concrete described in the present invention uses cement, fly ash, mineral powder, sand, and low-carbon, unburned fly ash ceramsite as main raw materials. The introduced modified sodium alginate can significantly enhance the bonding properties of cement-based composite cementitious materials, optimize the spacing between particles, and improve the molding efficiency of the obtained fly ash unburned ceramsite; the introduced modified sodium alginate can improve the interfacial bonding force of each powder component, promote the uniform distribution and tight stacking of the powder, and enhance the overall structural stability and density of the material; the ceramsite prepared with modified sodium alginate as the core has significantly improved compressive strength and fracture resistance, while reducing the density of the ceramsite, which can promote the improvement of the bearing capacity and durability of the obtained concrete.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1) The fly ash-free ceramsite prepared by the present invention using modified sodium alginate can significantly improve strength and toughness while maintaining lightweight properties. While solving the problems of traditional sodium alginate such as high hardness and brittleness, it can also give the fly ash-free ceramsite higher lightness and toughness (better compressive and fracture resistance). Furthermore, it does not require calcination, has significant economic and environmental benefits, and has a wide range of applications.

[0034] 2) The modified sodium alginate introduced in the present invention can significantly improve the bonding effect and molding efficiency of cement-based composite cementitious materials, providing a new approach for the preparation of high-performance lightweight aggregates;

[0035] 3) The fly ash unburned ceramsite of the present invention is used to prepare carbon unburned fly ash ceramsite concrete, which can take into account good low density, high strength and good durability, and is suitable for promotion and application. DETAILED DESCRIPTION

[0036] The present invention is further described in detail below through a specific implementation case. This implementation case is specifically implemented based on the technology of the present invention, and a detailed implementation method and specific operation process are now given, but the scope of protection of the present invention is not limited to the implementation case given below.

[0037] In the following examples, the sodium alginate used was provided by Suzhou Wuyi Chemical Technology Co., Ltd., with a molecular weight of 628 and a density of 1.13 g / cm 3 .

[0038] The chitin nanogel used was provided by Suzhou Beike Nanotechnology Co., Ltd., with a particle size of 50 to 150 nm, a polydispersity index of 0.2 to 0.3, and a Zeta potential of 45 to 50 mV.

[0039] The fly ash used was provided by China Construction Western Construction Xinjiang Co., Ltd. and its category was F Class II with a specific surface area of ​​350m 2 / kg.

[0040] In the following examples, the mineral powder used was provided by China Construction Western Construction Xinjiang Co., Ltd., and its grade was S75, with a specific surface area of ​​580m 2 / kg.

[0041] The cement used is ordinary Portland cement with a P·O 42.5 grade; the sand is natural sand with a fineness modulus of 2.3-2.7, belonging to zone II medium sand; the coarse aggregate used is the low-carbon fly ash unburned ceramsite prepared by the present invention, with a particle size of 5-15 mm; the water reducer used is ZJC-02 polycarboxylate water reducer provided by China Construction Western Construction New Materials Technology Co., Ltd., with a solid content of 17% and a water reduction rate of 28%.

[0042] Example 1

[0043] A low-carbon, unburned fly ash ceramsite concrete, the preparation method of which comprises the following steps:

[0044] 1) Preparation of low-carbon unburned fly ash ceramsite:

[0045] Sodium alginate and chitin nanogel (mass ratio 1:1) were weighed and placed in an ultrasonic disperser, ultrasonically dispersed at a frequency of 1500 Hz for 0.5 h, and then taken out and placed in a vacuum drying oven at a vacuum degree of 85 kPa and a temperature of 35°C for 12 h to obtain modified sodium alginate;

[0046] 5wt% cement, 10wt% silica fume, and 85wt% fly ash are weighed, added to a mixer, and mixed for 4 minutes to obtain a cement-based composite cementitious material; lime and water are weighed and mixed in a mass ratio of 1:1.5 to obtain lime water; 70 parts of the cement-based composite cementitious material, 15 parts of modified sodium alginate, and 8 parts of lime water are weighed and added to a disc-type pelletizer. The disc-type pelletizer has an inclination angle of 30° and a rotation speed of 40r / min. After rotating and pelletizing for 20 minutes, the pelletizer is taken out and placed in a curing chamber with a humidity of not less than 95% and a temperature of 20°C for 28 days to obtain low-carbon, unburned fly ash ceramsite;

[0047] 2) Preparation of low-carbon, unburned fly ash ceramsite concrete

[0048] Weigh 160 parts of cement, 130 parts of fly ash, 80 parts of mineral powder, 800 parts of sand, 600 parts of low-carbon unburned fly ash ceramsite, 140 parts of water, and 3 parts of high-performance water reducer, add them to a single-horizontal shaft forced mixer and stir for 1 minute. After pouring, put them into a test mold of 100mm*100mm*100mm (compressive strength) and 150mm*150mm*600mm (flexural strength), vibrate mechanically for 10s, remove the mold 24 hours after the surface is collected, and put it into a curing environment with a humidity of not less than 95% and a temperature of 20°C for 28 days to obtain low-carbon ceramsite concrete.

[0049] The density of the low-carbon, unburned fly ash ceramsite obtained in this embodiment is 850 kg / m 3 The particle size is 5-15 mm, the porosity is 14.3%, the crushing index is 14.6%, and the cylinder compressive strength is 25.6 MPa; the measured density of the obtained low-carbon ceramsite concrete is 1350 kg / m 3 , the electric flux after 28 days is 780 coulombs, the flexural strength after 28 days is 7.9 MPa, and the compressive strength after 28 days is 45.8 MPa.

[0050] Example 2

[0051] A low-carbon, unburned fly ash ceramsite concrete, the preparation method of which comprises the following steps:

[0052] 1) Preparation of low-carbon unburned fly ash ceramsite:

[0053] Sodium alginate and chitin nanogel (mass ratio 1:0.8) were weighed and placed in an ultrasonic disperser, and ultrasonically dispersed at a frequency of 1800 Hz for 1.0 h. The mixture was then taken out and placed in a vacuum drying oven at a vacuum degree of 85 kPa and a temperature of 40° C. for 16 h to obtain modified sodium alginate.

[0054] 8wt% of cement, 8wt% of silica fume and 84wt% of fly ash are weighed, added into a mixer and mixed for 4min to obtain a cement-based composite cementitious material; lime and water are weighed and mixed in a mass ratio of 1:4 to obtain lime water; 60 parts of cement-based composite cementitious material, 10 parts of modified sodium alginate and 10 parts of lime water are weighed and added into a disc-type pelletizing machine, the disc-type pelletizing machine has an inclination angle of 50° and a rotation speed of 50r / min, and the pellets are rotated and granulated for 10min, then taken out and placed in a curing machine with a humidity of not less than 95% and a temperature of 20°C for 28 days to obtain low-carbon and unburned fly ash ceramsite.

[0055] 2) Preparation of low-carbon, unburned fly ash ceramsite concrete

[0056] Weigh 160 parts of cement, 130 parts of fly ash, 80 parts of mineral powder, 800 parts of sand, 600 parts of low-carbon unburned fly ash ceramsite, 140 parts of water, and 3 parts of high-performance water reducer, add them to a single-horizontal shaft forced mixer and stir for 1 minute. After pouring, put them into a test mold of 100mm*100mm*100mm (compressive strength) and 150mm*150mm*600mm (flexural strength), vibrate mechanically for 10s, remove the mold 24 hours after the surface is collected, and put it into a curing environment with a humidity of not less than 95% and a temperature of 20°C for 28 days to obtain low-carbon ceramsite concrete.

[0057] After testing, the density of the low-carbon, unburned fly ash ceramsite obtained in this embodiment is 830 kg / m 3 The particle size is 5-15 mm, the porosity is 15.2%, the crushing index is 15.8%, and the cylinder pressure strength is 22.3 MPa; the measured density of the obtained low-carbon ceramsite concrete is 1410 kg / m 3 , the electric flux after 28 days is 850 coulombs, the flexural strength after 28 days is 7.2MPa, and the compressive strength after 28 days is 42.3MPa.

[0058] Example 3

[0059] A low-carbon, unburned fly ash ceramsite concrete, the preparation method of which comprises the following steps:

[0060] 1) Preparation of low-carbon unburned fly ash ceramsite:

[0061] Sodium alginate and chitin nanogel (mass ratio 1:1.34) were weighed and placed in an ultrasonic disperser, ultrasonically dispersed at a frequency of 2000 Hz for 1.0 h, and then taken out and placed in a vacuum drying oven at a vacuum degree of 85 kPa and a temperature of 35°C for 18 h to obtain modified sodium alginate;

[0062] Weigh 5wt% of cement, 6wt% of silica fume, and 89wt% of fly ash, add them to a mixer and mix them for 4 minutes to obtain a cement-based composite cementitious material; weigh lime and water in a mass ratio of 1:3 to obtain lime water; weigh 75 parts of the cement-based composite cementitious material, 20 parts of modified sodium alginate, and 5 parts of lime water, add them to a disc-type pelletizer, the disc-type pelletizer has an inclination angle of 45° and a rotation speed of 30r / min, rotates and granulates for 20 minutes, then takes them out and puts them into a curing machine with a humidity of not less than 95% and a temperature of 20°C for 28 days to obtain low-carbon, unburned fly ash ceramsite;

[0063] 2) Preparation of low-carbon, unburned fly ash ceramsite concrete

[0064] Weigh 160 parts of cement, 130 parts of fly ash, 80 parts of mineral powder, 800 parts of sand, 600 parts of low-carbon unburned fly ash ceramsite, 140 parts of water, and 3 parts of high-performance water reducer, add them to a single-horizontal shaft forced mixer and stir for 1 minute. After pouring, put them into a test mold of 100mm*100mm*100mm (compressive strength) and 150mm*150mm*600mm (flexural strength), vibrate mechanically for 10s, remove the mold 24 hours after the surface is collected, and put it into a curing environment with a humidity of not less than 95% and a temperature of 20°C for 28 days to obtain low-carbon ceramsite concrete.

[0065] After testing, the density of the low-carbon, unburned fly ash ceramsite obtained in this embodiment is 810 kg / m 3 The particle size is 5-15 mm, the porosity is 13.4%, the crushing index is 12.8%, and the cylinder pressure strength is 26.7 MPa; the measured density of the obtained low-carbon ceramsite concrete is 1320 kg / m 3 , the electric flux after 28 days is 710 coulombs, the flexural strength after 28 days is 8.5MPa, and the compressive strength after 28 days is 51.3MPa.

[0066] Comparative Example 1

[0067] A low-carbon, unburned fly ash ceramsite concrete, the preparation method of which comprises the following steps:

[0068] 1) Preparation of low-carbon unburned fly ash ceramsite:

[0069] Sodium alginate and chitin nanogel (mass ratio 1:1) were weighed, placed in a blender and mixed for 4 min to obtain modified sodium alginate;

[0070] 5wt% cement, 10wt% silica fume, and 85wt% fly ash are weighed, added to a mixer, and mixed for 4 minutes to obtain a cement-based composite cementitious material; lime and water are weighed and mixed in a mass ratio of 1:1.5 to obtain lime water; 70 parts of the cement-based composite cementitious material, 15 parts of modified sodium alginate, and 8 parts of lime water are weighed and added to a disc-type pelletizer. The disc-type pelletizer has an inclination angle of 30° and a rotation speed of 40r / min. After rotating and pelletizing for 20 minutes, the pelletizer is taken out and placed in a curing chamber with a humidity of not less than 95% and a temperature of 20°C for 28 days to obtain low-carbon, unburned fly ash ceramsite;

[0071] 2) Preparation of low-carbon, unburned fly ash ceramsite concrete

[0072] Weigh 160 parts of cement, 130 parts of fly ash, 80 parts of mineral powder, 800 parts of sand, 600 parts of low-carbon unburned fly ash ceramsite, 140 parts of water, and 3 parts of high-performance water reducer, add them to a single-horizontal shaft forced mixer and stir for 1 minute. After pouring, put them into a test mold of 100mm*100mm*100mm (compressive strength) and 150mm*150mm*600mm (flexural strength), vibrate mechanically for 10s, remove the mold 24 hours after the surface is collected, and put it into a curing environment with a humidity of not less than 95% and a temperature of 20°C for 28 days to obtain low-carbon ceramsite concrete.

[0073] After testing, the density of the low-carbon, unburned fly ash ceramsite obtained in this embodiment is 980 kg / m 3 The particle size is 5-15 mm, the porosity is 21.3%, the crushing index is 25.6%, and the cylinder pressure strength is 12.3 MPa; the measured density of the obtained low-carbon ceramsite concrete is 1650 kg / m 3 , the electric flux after 28 days is 1025 coulombs, the flexural strength after 28 days is 4.7MPa, and the compressive strength after 28 days is 32.3MPa.

[0074] Comparative Example 2

[0075] A low-carbon, unburned fly ash ceramsite concrete, the preparation method of which comprises the following steps:

[0076] 1) Preparation of low-carbon unburned fly ash ceramsite:

[0077] Weigh sodium alginate and chitin nanogel (mass ratio 1:0.8) and put them into an ultrasonic disperser, use a frequency of 1800 Hz for ultrasonic dispersion for 1.0 h, then take them out and put them into a drying oven at 35°C for 18 h to obtain modified sodium alginate;

[0078] 8wt% of cement, 8wt% of silica fume and 84wt% of fly ash are weighed, added into a mixer and mixed for 4min to obtain a cement-based composite cementitious material; lime and water are weighed and mixed in a mass ratio of 1:4 to obtain lime water; 60 parts of cement-based composite cementitious material, 10 parts of modified sodium alginate and 10 parts of lime water are weighed and added into a disc-type pelletizing machine, the disc-type pelletizing machine has an inclination angle of 50° and a rotation speed of 50r / min, and the pellets are rotated and granulated for 10min, then taken out and placed in a curing machine with a humidity of not less than 95% and a temperature of 20°C for 28 days to obtain low-carbon and unburned fly ash ceramsite.

[0079] 2) Preparation of low-carbon, unburned fly ash ceramsite concrete

[0080] Weigh 160 parts of cement, 130 parts of fly ash, 80 parts of mineral powder, 800 parts of sand, 600 parts of low-carbon unburned fly ash ceramsite, 140 parts of water, and 3 parts of high-performance water reducer, add them to a single-horizontal shaft forced mixer and stir for 1 minute. After pouring, put them into a test mold of 100mm*100mm*100mm (compressive strength) and 150mm*150mm*600mm (flexural strength), vibrate mechanically for 10s, remove the mold 24 hours after the surface is collected, and put it into a curing environment with a humidity of not less than 95% and a temperature of 20°C for 28 days to obtain low-carbon ceramsite concrete.

[0081] After testing, the density of the low-carbon, unburned fly ash ceramsite obtained in this embodiment is 940 kg / m 3 The particle size is 5-15 mm, the porosity is 19.6%, the crushing index is 22.3%, and the cylinder pressure strength is 15.6 MPa; the measured density of the obtained low-carbon ceramsite concrete is 1520 kg / m 3 , the electric flux after 28 days is 1100 coulombs, the flexural strength after 28 days is 4.9 MPa, and the compressive strength after 28 days is 35.4 MPa.

[0082] Those skilled in the art will readily be able to make improvements and modifications to the present invention without departing from the techniques of the present invention, and such improvements and modifications are also within the scope of protection of the present invention. The present invention is not limited to the above-described embodiments, and any changes that do not depart from the scope of the claims of the present invention are encompassed by the scope of protection.

Claims

1. A low-carbon, unburned fly ash ceramsite concrete, characterized in that: The components and their weight proportions include: 160-220 parts of cement, 70-130 parts of fly ash, 60-80 parts of mineral powder, 750-950 parts of sand, 550-750 parts of low-carbon and unburned fly ash ceramsite, 130-160 parts of water, and 2-5 parts of water reducer; the low-carbon and unburned fly ash ceramsite is obtained by granulation using cement-based composite cementitious material, modified sodium alginate, and lime water as main raw materials; The low-carbon unburned fly ash ceramsite comprises the following components and their weight proportions: 60-75 parts of cement-based composite gelling material, 10-20 parts of modified sodium alginate, and 5-15 parts of lime water; The cement-based composite cementitious material comprises ordinary Portland cement, silica fume and fly ash; the components and their mass percentages include: ordinary Portland cement 5-8%, silica fume 6-10%, fly ash 82-89%; The modified sodium alginate is obtained by mixing sodium alginate and chitin nanogel, performing ultrasonic dispersion treatment, and then vacuum drying. The modified sodium alginate is obtained by mixing sodium alginate and chitin nanogel, performing ultrasonic dispersion treatment, and then vacuum drying.

2. The low-carbon, unburned fly ash ceramsite concrete according to claim 1, characterized in that: The cement used is ordinary Portland cement with a strength grade of 42.5 or above; the fly ash is Class F II with a specific surface area of ​​320-400 m 2 / kg; the mineral powder is S75 grade, with a specific surface area of ​​500~800 m 2 / kg.

3. The low-carbon, unburned fly ash ceramsite concrete according to claim 1, characterized in that: The particle size of the low-carbon, unburned fly ash ceramsite is 5-15 mm; the sand is natural sand with a fineness modulus of 2.3-2.

7.

4. The low-carbon, unburned fly ash ceramsite concrete according to claim 1, characterized in that: The water reducing agent is a polycarboxylic acid water reducing agent with a water reduction rate of 25-35%.

5. The method for preparing the low-carbon, unburned fly ash ceramsite concrete according to any one of claims 1 to 4, characterized in that: The steps include: 1) Weighing the raw materials; the raw materials and their weight percentages include: 160-220 parts of cement, 70-130 parts of fly ash, 60-80 parts of mineral powder, 750-950 parts of sand, 550-750 parts of low-carbon unburned fly ash ceramsite, 130-160 parts of water, and 2-5 parts of water reducer; 2) The weighed cement, fly ash, mineral powder, low-carbon unburned fly ash ceramsite, sand, water, and water reducing agent are mixed evenly to obtain the low-carbon unburned fly ash ceramsite concrete.