Nanometer ultra-high performance concrete and preparation method thereof

Abstract

The application belongs to the technical field of ultra-high performance concrete, and more particularly relates to a kind of nano ultra-high performance concrete and its preparation method. One of the purposes is to provide a kind of nano ultra-high performance concrete, including the following weight parts of raw materials: general Portland cement 150-400 parts; slag powder 200-450 parts; fly ash modified microbead 100-150 parts; metakaolin 50-100 parts; composite alkali activator 22-50 parts; nano calcium carbonate 7-15 parts; fine aggregate 800-1200 parts; water reducing agent 10-26 parts; steel fiber 40-90 parts; wherein, the water-binder ratio of the nano ultra-high performance concrete is 0.15-0.27. Another purpose of the application is to provide a kind of preparation method of the above-mentioned nano ultra-high performance concrete.

Description

Technical Field

[0001] This invention belongs to the field of ultra-high performance concrete technology, and more specifically, relates to a nano-ultra-high performance concrete and its preparation method. Background Technology

[0002] Geopolymer concrete, prepared by alkali-activated materials rich in silicon and aluminum (such as silica fume, fly ash, and slag powder), is a new type of non-cement-based cementitious material. It is an inorganic aluminosilicate compound with ceramic-like properties. It does not require high-temperature curing and has advantages such as low production energy consumption, low carbon dioxide emissions, low cost, high utilization rate of industrial solid waste, and good durability. However, it also has disadvantages such as short setting and hardening time, poor workability, and high brittleness, which do not meet the increasingly high requirements of construction technology.

[0003] Ultra-high performance concrete (UHPC) is designed based on the theory of close packing of raw materials. By incorporating ultrafine auxiliary cementitious materials and increasing the dosage of high-efficiency water-reducing agents, it achieves a low water-cement ratio and high system density, exhibiting excellent mechanical properties and durability. However, the silicate cement used in the preparation of UHPC reaches 700-1100 kg / m³. 3 The production cost of silicate cement is 2 to 3 times higher than that of ordinary concrete. The production process consumes a large amount of natural resources and energy. According to research, producing one ton of silicate cement consumes 6.6 megajoules of energy and emits 0.82 tons of carbon dioxide, significantly increasing economic costs and environmental burden, which is quite detrimental to sustainable economic development.

[0004] To address the aforementioned issues, by combining the design principles of both, we can develop low-carbon and environmentally friendly ultra-high-performance concrete. This will help to effectively balance material performance indicators with green and low-carbon requirements, meet the new requirements for high-performance civil engineering materials, and have significant practical implications. Summary of the Invention

[0005] The present invention aims to overcome at least one of the defects of the prior art and provides a nano-ultra-high performance concrete and its preparation method to solve the problems of high consumption of natural resources and energy and high carbon emissions in the preparation process of ultra-high performance concrete.

[0006] The technical solution adopted in this invention is first to provide a nano-ultra-high performance concrete, comprising the following raw materials in parts by weight:

[0007] 150-400 parts of general-purpose silicate cement;

[0008] 200-450 parts of slag powder;

[0009] 100-150 parts of fly ash modified microspheres;

[0010] 50-100 parts of metakaolin;

[0011] 22-50 parts of compound alkali activator;

[0012] 7-15 parts of nano-calcium carbonate;

[0013] 800-1200 parts of fine aggregate;

[0014] 10-26 parts of water-reducing agent;

[0015] 40-90 parts steel fiber;

[0016] The water-cement ratio of the nano-ultra-high performance concrete is 0.15 to 0.27.

[0017] In this invention, by adding the general-purpose silicate cement in the above-mentioned proportions, the early hydration rate and heat of hydration are reduced, thus prolonging the setting time of the mixture; the early strength and early hardening rate of the mixture are adjusted, thereby regulating the setting time. By adding the nano-calcium carbonate in the above-mentioned proportions, it acts as a nucleation agent, promoting cement hydration and alkali-activated reactions; on the other hand, it acts as a filler, making the nano-ultra-high performance concrete more dense and improving its mechanical and durability properties. By adding the water-reducing agent in the above-mentioned proportions, it has dispersing, lubricating, steric hindrance, and slow-release effects of grafted copolymer branches, improving the fluidity and slump retention of the mixture. By adding the composite alkali activator in the above-mentioned proportions, the initial setting time of ultra-high performance concrete can be shortened, and ultra-high performance concrete can have very high early strength. By adding the modified fly ash microspheres in the above-mentioned proportions, it participates in the alkali-activated reaction, improving hardening strength; on the other hand, it acts as a lubricant, improving the fluidity of the mixture. The ultra-high performance concrete provided by this invention, compared with ultra-high performance concrete prepared using silicate cement, reduces carbon dioxide emissions by more than 50% under the same cubic volume conditions, has a high utilization rate of industrial solid waste, low cost, simple production, does not require high-temperature curing, has high compressive strength, good durability, and also has excellent characteristics such as long setting time and good toughness. It can meet the requirements of reliability and structural strength in actual use, and also meet the social requirements of low carbon and environmental protection.

[0018] The water-cement ratio refers to the ratio of water consumption per cubic meter of concrete to the total amount of cementitious materials. In this invention, the weight of the cementitious materials is the sum of the weights of cement, slag powder, fly ash modified microspheres, and metakaolin. Based on this water-cement ratio, water that meets the requirements is added to obtain high-performance nano-ultra-high-performance concrete.

[0019] The present invention further provides a method for preparing the aforementioned nano-ultra-high performance concrete:

[0020] The composite alkali activator is prepared into a solution and left to stand for a preset time; the corresponding weight parts of nano-ultra-high performance concrete raw materials are obtained and stirred and mixed in a preset order to obtain nano-ultra-high performance concrete mixture; the nano-ultra-high performance concrete mixture is poured into a mold to obtain the nano-ultra-high performance concrete.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) Compared with ultra-high performance concrete prepared by silicate cement, the nano-ultra-high performance concrete provided by the present invention has a carbon dioxide emission reduction of more than 50% under the same cubic volume conditions, high utilization rate of industrial solid waste, low cost, simple production, no need for high temperature curing, compressive strength of 130-200MPa, and good durability; 2) Compared with traditional geopolymer concrete, the nano-ultra-high performance concrete provided by the present invention has the characteristics of good workability, long setting time, and good toughness. Attached Figure Description

[0022] Figure 1 This is a process flow diagram for preparing the nano-ultra-high performance concrete of the present invention in some embodiments. Detailed Implementation

[0023] One objective of this invention is to provide a nano-ultra-high performance concrete, comprising the following raw materials in parts by weight:

[0024] 150-400 parts of general-purpose silicate cement;

[0025] 200-450 parts of slag powder;

[0026] 100-150 parts of fly ash modified microspheres;

[0027] 50-100 parts of metakaolin;

[0028] 22-50 parts of compound alkali activator;

[0029] 7-15 parts of nano-calcium carbonate;

[0030] 800-1200 parts of fine aggregate;

[0031] 10-26 parts of water-reducing agent;

[0032] 40-90 parts steel fiber;

[0033] The water-cement ratio of the nano-ultra-high performance concrete is 0.15 to 0.27.

[0034] Based on the above formula composition and proportion, the prepared nano-ultra-high performance concrete can have superior performance in many aspects such as scalability, compressive strength, flexural toughness ratio, and electrical flux, and greatly reduce carbon dioxide emissions, meeting the requirements of green environmental protection.

[0035] In a preferred embodiment, the nano-ultra-high performance concrete comprises the following raw materials in parts by weight:

[0036] General-purpose Portland cement, 212.5–337.5 parts;

[0037] Slag powder 262.5–387.5 parts;

[0038] 112.5–137.5 parts of modified fly ash microspheres;

[0039] Parts 62.5–87.5 of metakaolin;

[0040] 29-43 parts of compound alkali activator;

[0041] 9-13 parts of nano-calcium carbonate;

[0042] 900-1100 parts of fine aggregate;

[0043] 14-22 parts of water-reducing agent;

[0044] 52.5–77.5 parts steel fiber;

[0045] The water-cement ratio of the nano-ultra-high performance concrete is 0.18 to 0.24.

[0046] Based on the above-mentioned optimized formula, the performance of nano-ultra-high performance concrete in terms of compressive strength, durability, toughness and other aspects can be further improved.

[0047] In some embodiments, the general-purpose silicate cement specifically adopts any one or a mixture of two of slag cement and fly ash cement. Fly ash cement is processed from fly ash and ordinary clinker. The former is an industrial waste, used in large quantities, and can be recycled, helping to save raw material costs and meeting green environmental protection requirements. Furthermore, fly ash cement has a uniform texture, stable quality, and is easy to construct. Slag cement is mixed and blended from cement clinker and slag. The slag comes from metallurgical industry waste and is used in large quantities, helping to save raw material costs and meeting green environmental protection requirements. In addition, slag cement has a high calcium aluminate content, which can accelerate the cement reaction and further improve the cement's compressive strength and other mechanical properties.

[0048] In a preferred embodiment, the strength of the slag cement and fly ash cement used is not less than 32.5 MPa, so that the resulting nano-ultra-high performance concrete has higher strength.

[0049] To further improve performance, in a preferred embodiment, the average particle size of the slag powder is 5–30 μm; and / or, the average particle size of the fly ash modified microspheres is 5–30 μm; and / or, the average particle size of the metakaolin is 5–30 μm; and / or, the average particle size of the fine aggregate is 0.15–4.755 mm; and / or, the water-reducing agent is specifically a polycarboxylate water-reducing agent; and / or, the aspect ratio of the steel fiber is 60–120.

[0050] In some embodiments, the slag powder comprises the following raw materials by weight percentage: 10-30% slag powder with an activity index of 75%, 30-70% slag powder with an activity index of 95%, and 0-60% slag powder with an activity index of 105%. Using slag powder with this formula can significantly improve the compressive strength and flexural toughness ratio of the prepared nano-ultra-high performance concrete, while ensuring good scalability and lower electrical flux, thereby improving overall performance.

[0051] In a preferred embodiment, the slag powder comprises the following raw materials by weight percentage: 15-25% slag powder with an activity index of 75%, 40-60% slag powder with an activity index of 95%, and 15-45% slag powder with an activity index of 105%. Using slag powder with this formula ratio can further improve the compressive strength, scalability, flexural toughness ratio, electrical conductivity, and other properties of nano-ultra-high performance concrete.

[0052] In some embodiments, the fine aggregate is one or more of river sand, quartz sand, waste ceramic aggregate, and waste glass aggregate.

[0053] In a preferred embodiment, the water absorption rate of the waste ceramic aggregate is less than 3%.

[0054] In some embodiments, the composite alkali activator is a mixture of sodium hydroxide and sodium carbonate.

[0055] In a preferred embodiment, the composite alkali activator comprises the following raw materials by weight percentage: 50-80% sodium hydroxide and 20-50% sodium carbonate. Using the composite alkali activator of this formulation, the prepared nano-ultra-high performance concrete can have better scalability, compressive strength and flexural toughness ratio, and has a smaller electrical flux, resulting in superior overall performance.

[0056] More preferably, the composite alkali activator comprises the following raw materials by weight percentage: 60-70% sodium hydroxide and 30-40% sodium carbonate. Using this formula ratio of composite alkali activator can further improve the scalability, compressive strength, flexural toughness ratio and electrical flux of nano-ultra-high performance concrete.

[0057] Another objective of this invention is to provide a method for preparing nano-ultra-high performance concrete: a composite alkali activator is prepared into a solution and left to stand for a preset time; the corresponding weight proportions of nano-ultra-high performance concrete raw materials are obtained and stirred and mixed in a preset order to obtain a nano-ultra-high performance concrete mixture; the nano-ultra-high performance concrete mixture is poured into a mold to obtain the nano-ultra-high performance concrete.

[0058] In some embodiments, since the composite alkali activator needs to be left to stand for a preset time after being prepared into a solution, this step can be pre-processed in order to better connect the various processes, and then the various raw materials of nano-ultra-high performance concrete can be mixed.

[0059] In some other embodiments, considering that the process of mixing the various raw materials of nano-ultra-high performance concrete takes a certain amount of time, a composite alkali activator can also be prepared into a solution and left to stand for a preset time during the process of mixing the various raw materials of nano-ultra-high performance concrete.

[0060] The preset time can be 8-48 hours, and in some embodiments, the preset time is 24 hours.

[0061] In some embodiments, the mixing and blending are carried out in a preset order as follows: first, fine aggregate and steel fiber are mixed and blended, then general silicate cement, slag powder, fly ash modified microspheres, metakaolin and nano calcium carbonate are added and mixed and blended, and finally alkali activator solution, water and water-reducing agent are added and mixed and blended.

[0062] In a preferred embodiment, the mixing time for fine aggregate and steel fiber is 2-4 minutes, and / or the mixing time after adding general silicate cement, slag powder, fly ash modified microspheres, metakaolin and nano calcium carbonate is 4-6 minutes, and / or the mixing time after adding alkali activator solution, water and water-reducing agent is 5-8 minutes, and / or the spread of the nano ultra-high performance concrete mixture is 500-750 mm, and / or the setting time of the nano ultra-high performance concrete mixture is 2-6 hours.

[0063] In some embodiments, the compressive strength of the prepared nano-ultra-high performance concrete is 130-200 MPa after 28 days of room temperature curing.

[0064] In some embodiments, the preparation method of nano-ultra-high performance concrete is as follows: Figure 1 As shown, it includes the following steps:

[0065] S1. Prepare a solution of the composite alkali activator and let it stand for 24 hours for later use;

[0066] S2. Calculate the amount of each raw material according to the proportion of nano-ultra-high performance concrete, mix the fine aggregate and steel fiber evenly; then add slag cement and / or fly ash cement, as well as slag powder, fly ash modified microspheres, metakaolin and nano calcium carbonate, and mix evenly; finally add alkali activator solution, water and water-reducing agent and mix evenly to obtain nano-ultra-high performance concrete mixture.

[0067] S3. The nano-ultra-high performance concrete mixture obtained in step S2 is poured into a mold to obtain the nano-ultra-high performance concrete.

[0068] Preferably, the fine aggregate and steel fiber are mixed for 2 to 4 minutes.

[0069] Preferably, the mixing time after adding slag cement and / or fly ash cement, as well as slag powder, fly ash modified microspheres, metakaolin and nano calcium carbonate is 4 to 6 minutes.

[0070] Preferably, the mixing time after adding the alkali activator solution, water, and water-reducing agent is 5 to 8 minutes.

[0071] Based on the above control of mixing time, it is possible to ensure thorough mixing while avoiding excessive stirring time, thus shortening the preparation period of nano-ultra-high performance concrete.

[0072] In a preferred embodiment, the spread of the obtained nano-ultra-high performance concrete mixture is 500-750 mm.

[0073] In addition, by setting the setting time of the nano-ultra-high performance concrete mixture in step S2 to 2 to 6 hours, it is ensured that the next process can produce nano-ultra-high performance concrete with the required performance.

[0074] In a preferred embodiment, the compressive strength of the nano-ultra-high performance concrete obtained in step S3 after 28 days of room temperature curing is 130-200 MPa.

[0075] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0076] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0077] Example 1

[0078] This embodiment provides a nano-ultra-high performance concrete, comprising the following raw materials in parts by weight:

[0079] A total of 150 parts of slag cement with a strength of not less than 32.5 MPa and / or fly ash cement with a strength of not less than 32.5 MPa;

[0080] 200 parts of slag powder with an average particle size of 5-30 μm, including 10% slag powder with an activity index of 75%, 30% slag powder with an activity index of 95%, and 60% slag powder with an activity index of 105%.

[0081] 100 parts of fly ash modified microspheres with an average particle size of 5-30 μm;

[0082] 50 parts of metakaolin with an average particle size of 5-30 μm;

[0083] 22 parts of a compound alkali activator, wherein the mass percentage of sodium hydroxide is 50% and the mass percentage of sodium carbonate is 50%;

[0084] 7 parts of nano-calcium carbonate;

[0085] 800 parts of fine aggregate with an average particle size of 0.15–4.755 mm;

[0086] 10 parts of polycarboxylate superplasticizer;

[0087] 40 parts of steel fiber with an aspect ratio of 60 to 120;

[0088] Water-to-binder ratio: 0.15.

[0089] The method for preparing nano-ultra-high performance concrete in this embodiment is carried out according to the following steps:

[0090] S11 The composite alkali activator is prepared into a solution and left to stand for 24 hours for later use;

[0091] S21 calculates the amount of each raw material according to the mix proportion of nano-ultra-high performance concrete, puts fine aggregate and steel fiber into the mixer and mixes for 2-4 minutes; then adds slag cement and / or fly ash cement, as well as slag powder, fly ash modified microspheres, metakaolin and nano calcium carbonate, and mixes for 4-6 minutes; finally adds alkali activator solution, water and polycarboxylate superplasticizer and mixes for 5-8 minutes to obtain nano-ultra-high performance concrete mixture;

[0092] S31 The nano-ultra-high performance concrete mixture obtained in step S21 is poured into a mold to obtain nano-ultra-high performance concrete.

[0093] Example 2

[0094] Except for the different formulation of the nano-ultra-high performance concrete, the other conditions in this embodiment are the same as in Embodiment 1.

[0095] The nano-ultra-high performance concrete provided in this embodiment comprises the following raw materials in parts by weight:

[0096] 400 parts of slag cement with a strength of not less than 32.5 MPa and / or fly ash cement with a strength of not less than 32.5 MPa;

[0097] 450 parts of slag powder with an average particle size of 5-30 μm, including 30% slag powder with an activity index of 75%, 70% slag powder with an activity index of 95%, and 0% slag powder with an activity index of 105%.

[0098] 50 parts of fly ash modified microspheres with an average particle size of 5-30 μm;

[0099] 100 parts of metakaolin with an average particle size of 5-30 μm;

[0100] 50 parts of a compound alkali activator, wherein the mass percentage of sodium hydroxide is 80% and the mass percentage of sodium carbonate is 20%;

[0101] 15 parts of nano-calcium carbonate;

[0102] 1200 parts of fine aggregate with an average particle size of 0.15–4.755 mm;

[0103] 26 parts of polycarboxylate superplasticizer;

[0104] 90 parts of steel fiber with an aspect ratio of 60 to 120;

[0105] Water-to-binder ratio: 0.27.

[0106] Example 3

[0107] Except for the different formulation of the nano-ultra-high performance concrete, the other conditions in this embodiment are the same as in Embodiment 1.

[0108] The nano-ultra-high performance concrete provided in this embodiment comprises the following raw materials in parts by weight:

[0109] A total of 212.5 parts of slag cement with a strength of not less than 32.5 MPa and / or fly ash cement with a strength of not less than 32.5 MPa;

[0110] 262.5 parts of slag powder with an average particle size of 5-30 μm, including 15% slag powder with an activity index of 75%, 40% slag powder with an activity index of 95%, and 45% slag powder with an activity index of 105%.

[0111] 112.5 parts of fly ash modified microspheres with an average particle size of 5-30 μm;

[0112] 62.5 parts of metakaolin with an average particle size of 5–30 μm;

[0113] 29 parts of a compound alkali activator, wherein the mass percentage of sodium hydroxide is 60% and the mass percentage of sodium carbonate is 40%;

[0114] 9 parts of nano-calcium carbonate;

[0115] 900 parts of fine aggregate with an average particle size of 0.15–4.755 mm;

[0116] 14 parts of polycarboxylate superplasticizer;

[0117] 52.5 parts of steel fiber with an aspect ratio of 60–120;

[0118] Water-to-binder ratio: 0.18.

[0119] Example 4

[0120] Except for the different formulation of the nano-ultra-high performance concrete, the other conditions in this embodiment are the same as in Embodiment 1.

[0121] The nano-ultra-high performance concrete provided in this embodiment comprises the following raw materials in parts by weight:

[0122] A total of 337.5 parts of slag cement with a strength of not less than 32.5 MPa and / or fly ash cement with a strength of not less than 32.5 MPa;

[0123] 387.5 parts of slag powder with an average particle size of 5-30 μm, including 25% slag powder with an activity index of 75%, 60% slag powder with an activity index of 95%, and 15% slag powder with an activity index of 105%.

[0124] 137.5 parts of fly ash modified microspheres with an average particle size of 5-30 μm;

[0125] 87.5 parts of metakaolin with an average particle size of 5–30 μm;

[0126] 43 parts of a compound alkali activator, wherein the mass percentage of sodium hydroxide is 70% and the mass percentage of sodium carbonate is 30%;

[0127] 13 parts of nano-calcium carbonate;

[0128] Fine aggregate with an average particle size of 0.15–4.755 mm, approximately 1100 parts;

[0129] 22 parts of polycarboxylate superplasticizer;

[0130] 77.5 parts of steel fiber with an aspect ratio of 60–120;

[0131] Water-to-binder ratio: 0.24.

[0132] Example 5

[0133] Except for the different formulation of the nano-ultra-high performance concrete, the other conditions in this embodiment are the same as in Embodiment 1.

[0134] The nano-ultra-high performance concrete provided in this embodiment comprises the following raw materials in parts by weight:

[0135] A total of 275 parts of slag cement with a strength of not less than 32.5 MPa and / or fly ash cement with a strength of not less than 32.5 MPa;

[0136] 325 parts of slag powder with an average particle size of 5-30 μm, including 20% ​​slag powder with an activity index of 75%, 50% slag powder with an activity index of 95%, and 30% slag powder with an activity index of 105%.

[0137] 125 parts of fly ash modified microspheres with an average particle size of 5-30 μm;

[0138] 75 portions of metakaolin with an average particle size of 5–30 μm;

[0139] 36 parts of a compound alkali activator, wherein the mass percentage of sodium hydroxide is 65% and the mass percentage of sodium carbonate is 35%;

[0140] 11 parts of nano-calcium carbonate;

[0141] 1000 parts of fine aggregate with an average particle size of 0.15–4.755 mm;

[0142] 18 parts of polycarboxylate superplasticizer;

[0143] 65 parts of steel fiber with an aspect ratio of 60 to 120;

[0144] Water-to-binder ratio: 0.21.

[0145] Comparative Example 1

[0146] The difference in this comparative example is that the number of parts of the composite alkali activator added is 10 parts, and the other conditions are the same as in Example 1. The formula of the composite alkali activator in this comparative example is also the same as in Example 1, that is, 50% by mass of sodium hydroxide and 50% by mass of sodium carbonate.

[0147] Comparative Example 2

[0148] The difference in this comparative example is that the amount of nano-calcium carbonate added is 3 parts, while other conditions are the same as in Example 1.

[0149] Comparative Example 3

[0150] The difference in this comparative example is that the number of parts of the composite alkali activator added is 60 parts, and the other conditions are the same as in Example 1. The formulation of the composite alkali activator in this comparative example is also the same as in Example 1, that is, 50% by mass of sodium hydroxide and 50% by mass of sodium carbonate.

[0151] Comparative Example 4

[0152] The number of composite alkali activators added in this comparative example is the same as that in Example 1, which is 22 parts. The difference is that the formula of the composite alkali activator is: sodium hydroxide by mass percentage is 30% and sodium carbonate by mass percentage is 70%. Other conditions are the same as in Example 1.

[0153] Comparative Example 5

[0154] The number of composite alkali activators added in this comparative example is the same as that in Example 1, which is 22 parts. The difference is that the formula of the composite alkali activator is: 90% sodium hydroxide and 10% sodium carbonate by mass. Other conditions are the same as in Example 1.

[0155] Comparative Example 6

[0156] The comparative example also used 200 parts of slag powder with an average particle size of 5-30 μm. The only difference was the specific composition of the slag powder. Except for 60% slag powder with an activity index of 75%, 20% slag powder with an activity index of 95%, and 20% slag powder with an activity index of 105%, the other conditions were the same as in Example 1.

[0157] Comparative Example 7

[0158] The comparative example also used 200 parts of slag powder with an average particle size of 5-30 μm. The only difference was the specific composition of the slag powder. Except for 5% slag powder with an activity index of 75%, 90% slag powder with an activity index of 95%, and 5% slag powder with an activity index of 105%, the other conditions were the same as in Example 1.

[0159] Comparative Example 8

[0160] This comparative example is C150 ultra-high performance concrete prepared using silicate cement, wherein 700 kg of silicate cement is used for one cubic meter of C150 ultra-high performance concrete.

[0161] Comparative Example 9

[0162] This comparative example is traditional geopolymer concrete.

[0163] Test case

[0164] The spread, setting time, compressive strength, electrical flux and flexural toughness ratio of the nano-ultra-high performance concrete prepared in Examples 1-5 and Comparative Examples 1-7, as well as the C150 ultra-high performance concrete in Comparative Example 8 and the monopolymer concrete in Comparative Example 9, were tested. The carbon dioxide emissions of Example 1 and Comparative Example 6 were also compared. The experimental data are shown in Table 1.

[0165] Table 1. Test data of ultra-high performance concrete

[0166]

[0167]

[0168] Based on the test results in Table 1, we can see that:

[0169] In Comparative Example 1, only the amount of composite alkali activator added was lower than that in Example 1. Compared with Example 1, the nano-ultra-high performance concrete prepared in this example had slightly lower expansion and setting time, significantly lower compressive strength and flexural toughness, and significantly higher electrical flux.

[0170] In Comparative Example 2, only the amount of nano-calcium carbonate added was lower than that in Example 1. Compared with Example 1, the nano-ultra-high performance concrete prepared in this example had basically the same spread, a slightly lower setting time, a greater decrease in compressive strength and flexural toughness, and a greater increase in electrical flux.

[0171] In Comparative Example 3, only the amount of composite alkali activator added was higher than that in Example 1. Compared with Example 1, the nano-ultra-high performance concrete prepared in this example showed a significant decrease in spread, setting time, compressive strength, and flexural toughness ratio, while the electrical flux increased significantly.

[0172] In Comparative Example 4, the amount of composite alkali activator added was 22 parts. Only the composition of the composite alkali activator was different from that in Example 1. The mass percentage of sodium hydroxide was 30% and the mass percentage of sodium carbonate was 70%. Compared with Example 1, the nano-ultra-high performance concrete prepared by it had a greater decrease in expansion, compressive strength and flexural toughness, a slight decrease in setting time and a greater increase in electrical flux.

[0173] In Comparative Example 5, the amount of composite alkali activator added was 22 parts. Only the composition of the composite alkali activator was different from that in Example 1. The mass percentage of sodium hydroxide was 90% and the mass percentage of sodium carbonate was 10%. Compared with Example 1, the nano-ultra-high performance concrete prepared by it had a significant decrease in expansion, setting time, flexural toughness ratio and compressive strength, and a significant increase in electrical flux.

[0174] In Comparative Example 6, only the composition of the slag powder was different. Specifically, it consisted of 60% slag powder with an activity index of 75%, 20% slag powder with an activity index of 95%, and 20% slag powder with an activity index of 105%. Compared with Example 1, the expansion and setting time decreased slightly, the compressive strength and flexural toughness decreased significantly, and the electrical flux increased significantly.

[0175] In Comparative Example 7, only the composition of the slag powder is different. Specifically, it contains 5% slag powder with an activity index of 75%, 90% slag powder with an activity index of 95%, and 5% slag powder with an activity index of 105%. Compared with Example 1, the expansion and setting time are slightly reduced, the compressive strength and flexural toughness are significantly reduced, and the electrical flux is significantly increased.

[0176] In Comparative Example 8, C150 ultra-high performance concrete was prepared using silicate cement. Compared with Example 1, the amount of cement used increased significantly. The spread, setting time, compressive strength, flexural toughness ratio and electrical flux were basically the same, but the carbon dioxide emissions increased significantly, by about 125%.

[0177] In Comparative Example 9, traditional geopolymer concrete was used. Compared with Example 1, the spread, setting time and flexural toughness ratio decreased significantly, the compressive strength decreased slightly, and the electrical flux increased significantly.

[0178] Based on the above tests, it can be seen that the composite alkali activator, slag powder and nano calcium carbonate selected in this invention are the best raw materials; the nano ultra-high performance concrete of this invention can significantly reduce carbon dioxide emissions, improve the utilization rate of industrial solid waste, and also show advantages in many key technical indicators such as expansion, compressive strength, flexural toughness and electrical flux.

[0179] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the technical solution of the present invention, and are not intended to limit the specific implementation of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the claims of the present invention should be included within the protection scope of the claims of the present invention.

Claims

1. A nano-ultra-high performance concrete, characterized in that, The ingredients include the following parts by weight: 150-400 parts of general-purpose silicate cement; 200-450 parts of slag powder; 100-150 parts of fly ash modified microspheres; 50-100 parts of metakaolin; 22-50 parts of compound alkali activator; 7-15 parts of nano-calcium carbonate; 800-1200 parts of fine aggregate; 10-26 parts of water-reducing agent; 40-90 parts steel fiber; The water-cement ratio of the nano-ultra-high performance concrete is 0.15~0.27; The general-purpose silicate cement is any one or a mixture of two of slag cement and fly ash cement, and the strength of the general-purpose silicate cement is not less than 32.5 MPa. The composite alkali activator is composed of the following raw materials by weight percentage: 50-80% sodium hydroxide and 20-50% sodium carbonate.

2. The nano-ultra-high performance concrete according to claim 1, characterized in that, The ingredients include the following parts by weight: General-purpose Portland cement, 212.5~337.5 parts; Slag powder 262.5~387.5 parts; 112.5~137.5 parts of modified fly ash microspheres; Parts 62.5–87.5 of metakaolin; 29-43 parts of compound alkali activator; 9-13 parts of nano-calcium carbonate; 900-1100 parts fine aggregate; 14-22 parts of water-reducing agent; 52.5~77.5 parts steel fiber; The water-cement ratio of the nano-ultra-high performance concrete is 0.18~0.

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3. The nano-ultra-high performance concrete according to claim 1 or 2, characterized in that, The average particle size of the slag powder is 5~30μm; and / or, the average particle size of the fly ash modified microspheres is 5~30μm; and / or, the average particle size of the metakaolin is 5~30μm; and / or, the average particle size of the fine aggregate is 0.15~4.755mm; and / or, the water-reducing agent is a polycarboxylate water-reducing agent; and / or, the aspect ratio of the steel fiber is 60~120.

4. The nano-ultra-high performance concrete according to claim 1 or 2, characterized in that, The slag powder comprises the following raw materials by weight percentage: 10-30% slag powder with an activity index of 75%, 30-70% slag powder with an activity index of 95%, and 0-60% slag powder with an activity index of 105%.

5. The nano-ultra-high performance concrete according to claim 4, characterized in that, The slag powder comprises the following raw materials by weight percentage: 15-25% slag powder with an activity index of 75%, 40-60% slag powder with an activity index of 95%, and 15-45% slag powder with an activity index of 105%.

6. The nano-ultra-high performance concrete according to claim 1 or 2, characterized in that, The fine aggregate is one or more of river sand, quartz sand, waste ceramic aggregate, and waste glass aggregate.

7. The nano-ultra-high performance concrete according to claim 6, characterized in that, The water absorption rate of the waste ceramic aggregate is less than 3%.

8. The nano-ultra-high performance concrete according to claim 1 or 2, characterized in that, The composite alkali activator comprises the following raw materials by weight percentage: 60-70% sodium hydroxide and 30-40% sodium carbonate.

9. A method for preparing nano-ultra-high performance concrete according to any one of claims 1-8, characterized in that, The composite alkali activator is prepared into a solution and left to stand for a preset time; the corresponding weight parts of nano-ultra-high performance concrete raw materials are obtained and stirred and mixed in a preset order to obtain nano-ultra-high performance concrete mixture; the nano-ultra-high performance concrete mixture is poured into a mold to obtain the nano-ultra-high performance concrete.

10. The preparation method according to claim 9, characterized in that, The mixing method according to the preset order is as follows: First, fine aggregate and steel fiber are mixed evenly. Then, general silicate cement, slag powder, fly ash modified microspheres, metakaolin and nano calcium carbonate are added and mixed evenly. Finally, alkali activator solution, water and water-reducing agent are added and mixed evenly.

11. The preparation method according to claim 10, characterized in that, The mixing time for fine aggregate and steel fiber is 2-4 minutes, and / or the mixing time after adding general silicate cement, slag powder, fly ash modified microspheres, metakaolin and nano calcium carbonate is 4-6 minutes, and / or the mixing time after adding alkali activator solution, water and water-reducing agent is 5-8 minutes, and / or the spread of the nano ultra-high performance concrete mixture is 500-750 mm, and / or the setting time of the nano ultra-high performance concrete mixture is 2-6 hours.

12. The preparation method according to claim 9, characterized in that, The prepared nano-ultra-high performance concrete has a compressive strength of 130~200MPa after 28 days of room temperature curing.

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