Alkali-activated green ultra-high performance concrete and preparation method thereof

Abstract

The invention discloses alkali-activated green ultra-high performance concrete and a preparation method thereof, the alkali-activated green ultra-high performance concrete comprises the following raw materials: a cementing material, steel fiber, fine aggregate, a water reducing agent, an alkali activator and water, and the cementing material comprises the following raw materials: cement, silica fume, quartz powder, calcium powder, mineral powder, fly ash and coal gasification slag. According to the concrete prepared by the invention, the use amount of cement is remarkably reduced and the utilization rate of solid wastes is increased while excellent working performance and compressive strength are met, so that the production cost of UHPC (Ultra High Performance Concrete) is reduced, the environmental pollution is reduced, green UHPC is realized, and the concrete has important value for popularizing the engineering application of UHPC.

Description

Technical Field

[0001] The invention belongs to the technical field of concrete, and in particular relates to an alkali-activated green ultra-high performance concrete and a preparation method thereof. Background Art

[0002] Ultra-high performance concrete (UHPC) is a new type of high-performance cement-based composite material with ultra-high strength (>120MPa), high toughness, excellent durability and long-term stability. It is widely used in civil engineering. However, due to the fact that UHPC does not contain coarse aggregate, has a low water-cement ratio and a fast hydration reaction rate, while having excellent material properties, it is prone to problems such as high hydration heat and shrinkage cracking, which limits its large-scale promotion. The amount of cementitious material in UHPC is as high as 1200kg / m 3 The cement consumption is 900-1100 kg / m 3 , which is about three times that of ordinary concrete, but its cement hydration degree is only about 40%, and most of the cement is filled in the UHPC as expensive filler. Research data shows that the production of one ton of Portland cement releases about 0.82 tons of CO2, and the annual production of Portland cement produces 74-81% of the global CO2 emissions, which is equivalent to about 3.24 billion tons of CO2 emitted into the atmosphere each year. The high use of cement has caused resource waste and high carbon emissions. Therefore, how to reduce the amount of cement used in the UHPC preparation process is of great significance to reducing resource waste and achieving green and low-carbon. Summary of the invention

[0003] The purpose of the present invention is to provide an alkali-activated green ultra-high performance concrete and a preparation method thereof, so as to solve the problems that the ultra-high performance concrete has large cement dosage and has the disadvantages of large hydration heat, shrinkage cracking and the like.

[0004] To achieve the above object, the first aspect of the present invention provides an alkali-activated green ultra-high performance concrete. The alkali-activated green ultra-high performance concrete comprises the following raw materials in parts by weight:

[0005]

[0006] The gelling material includes the following raw materials in parts by weight:

[0007]

[0008] Preferably, the fine aggregate is three types of continuously graded quartz sands of different particle sizes;

[0009] In terms of weight, fine aggregate includes the following raw materials:

[0010] 0.106-0.15mm fine aggregate - 400-600 parts;

[0011] 100 - 300 parts of fine aggregate two with a size of 0.15 - 0.212 mm;

[0012] 200 - 400 parts of fine aggregate three with a size of 0.212 - 0.425 mm.

[0013] Preferably, the steel fiber is a cylindrical fiber with a length of 13 mm and a diameter of 0.2 mm, and the tensile strength is 2300 MPa.

[0014] Preferably, the water reducing agent is a polycarboxylic acid powder water reducing agent, and the water reducing rate is 25%.

[0015] Preferably, the alkali activator is at least one of solid flaky KOH, sodium hydroxide, sodium carbonate, and sodium sulfate.

[0016] Preferably, the cement is P·O 52.5 type ordinary Portland cement with a density of 3.1 g / cm 3 ; the silica fume is 98 silica fume with a density of 2.2 g / cm 3 ; the particle size of the quartz powder is 2000 mesh.

[0017] Preferably, the calcium powder is heavy calcium powder with a density of 2.5 g / cm 3 ; the mineral powder is S95 grade mineral powder with a density of 2.5 g / cm 3 .

[0018] Preferably, the fly ash is Class I fly ash with a density of 2.3 g / cm 3 , the particle size of the coal gasification slag is 0 - 0.045 mm, and the density is 1.8 g / cm 3 .

[0019] The second aspect of the present invention provides a preparation method of alkali-activated green ultra-high performance concrete, comprising the following steps:

[0020] a) Mix cement, silica fume, quartz powder, calcium powder, mineral powder, fly ash, and coal gasification slag to obtain a cementitious material for standby;

[0021] b) Mix the cementitious material, fine aggregate, and water reducing agent to obtain a mixture;

[0022] c) Add the alkali activator to 80% of the total water volume, stir evenly, then add the mixture, continue stirring, add the remaining water, and stir evenly to obtain a slurry;

[0023] d) Add steel fibers to the slurry and stir evenly to obtain a paste;

[0024] e) Pour the paste into the corresponding mold, cover with a film and let it stand for 24 h, then remove the mold and place it in a standard curing room for curing to 28 d.

[0025] Preferably, the water-binder ratio of the concrete is 0.15 to 0.18. After curing, the 28-day compressive strength is 130 to 200 MPa, the tensile strength is 7 to 10 MPa, and the chloride ion diffusion coefficient is 0.05×10 -12 ~0.25×10 -12 .

[0026] Therefore, the present invention adopts the above-mentioned alkali-activated green ultra-high performance concrete and its preparation method, and has the following beneficial effects:

[0027] (1) By utilizing an alkali activator to activate the activity of mineral admixtures, the present invention fully exerts the reaction activities of silicon dioxide and alumina in mineral powder, fly ash and gasification slag, and formulates a green ultra-high performance concrete with a low cement content; moreover, the present invention uses mineral powder, fly ash and gasification slag to prepare ultra-high performance concrete, realizing the resource utilization of solid waste and solving the problem of solid waste pollution to the environment.

[0028] (2) By selecting appropriate raw materials and optimizing the ratio, the present invention greatly reduces the cement consumption of ultra-high performance concrete. The proportion of cement in the cementitious material is reduced from 60% - 80% in the prior art to 15% - 25%, reducing carbon emissions and improving the green degree of ultra-high performance concrete.

[0029] (3) The concrete prepared by the present invention has excellent mechanical properties, durability and more excellent workability. The concrete has good fluidity, can fully reach the self-compacting state, and has few internal pores and small pore diameters.

[0030] The technical solution of the present invention will be further described in detail through examples below. Specific Embodiments

[0031] The present invention will be further described below. It should be noted that this embodiment is based on the present technical solution, and gives detailed implementation methods and specific operation processes, but the present invention is not limited to this embodiment.

[0032] The raw material compositions of the alkali-activated green ultra-high performance concrete in Examples 1 to 4 are shown in Table 1.

[0033] Table 1 Concrete composition components and contents in Examples 1 - 3

[0034]

[0035]

[0036] Among them:

[0037] The cement is P·O 52.5 type ordinary Portland cement, and the density is 3.1 g / cm 3 ;

[0038] The silica fume is 98% silica fume with a density of 2.2 g / cm 3 ;

[0039] The quartz powder is 2000-mesh and is added as a filler;

[0040] The calcium powder is heavy calcium powder with a density of 2.5 g / cm 3 ;

[0041] The mineral powder is S95-grade mineral powder with a density of 2.5 g / cm 3 ;

[0042] The fly ash is Class I fly ash with a density of 2.3 g / cm 3 ;

[0043] The coal gasification slag has a fine slag particle size of 0.045 mm and a density of 1.8 g / cm 3 ;

[0044] The steel fiber is a cylindrical fiber with a length of 13 mm and a diameter of 0.2 mm, and its tensile strength is 2300 MPa;

[0045] The fine aggregate is three kinds of continuously graded quartz sands with particle sizes of 0.106 - 0.15 mm, 0.15 - 0.212 mm, and 0.212 - 0.425 mm;

[0046] The water reducing agent is a polycarboxylic acid powder water reducing agent with a water reducing rate of 25%;

[0047] The alkali activator is KOH, in solid flake form.

[0048] The preparation method of the concrete in Examples 1 - 4 includes the following steps:

[0049] a) Mix cement, silica fume, quartz powder, calcium powder, mineral powder, fly ash, and coal gasification slag, and stir at a low speed of 150 r / min for 90 s to obtain a cementitious material for standby;

[0050] b) Mix the cementitious material, fine aggregate, and water reducing agent, and stir at a low speed of 150 r / min for 90 s to obtain a mixture;

[0051] c) Add the alkali activator to 80% of the total water volume, stir at a low speed of 150 r / min for 90 s, then add the mixture, continue stirring, let it stand for 30 s, add the remaining water, stir at a low speed of 150 r / min for 180 s, and then stir at a high speed of 300 r / min for 120 s to obtain a slurry;

[0052] d) Add steel fibers to the slurry and stir at a low speed of 150 r / min for 90 s to obtain a paste;

[0053] e) Pour the slurry into the corresponding mold. After covering it with a film and standing still for 24 h, remove the mold and place it in a standard curing room for curing until 28 d. The temperature in the curing room is 20 ± 2 °C, and the humidity is greater than 95%.

[0054] Comparative Example 1

[0055] The difference between this comparative example and Example 1 is that no alkali activator potassium hydroxide is added.

[0056] Comparative Example 2

[0057] The difference between this comparative example and Example 1 is that 0 parts of silica fume, 310 parts of mineral powder, 240 parts of fly ash and 70 parts of coal gasification slag are added.

[0058] Comparative Example 3

[0059] The difference between this comparative example and Example 1 is that 0 parts of quartz powder, 310 parts of mineral powder, 240 parts of fly ash and 70 parts of coal gasification slag are added.

[0060] Comparative Example 4

[0061] The difference between this comparative example and Example 1 is that 0 parts of calcium powder, 310 parts of mineral powder, 240 parts of fly ash and 70 parts of coal gasification slag are added.

[0062] Comparative Example 5

[0063] The difference between this comparative example and Example 1 is that 200 parts of mineral powder, 200 parts of fly ash and 110 parts of coal gasification slag are added.

[0064] Comparative Example 6

[0065] The difference between this comparative example and Example 1 is that no alkali activator potassium hydroxide is added, and 200 parts of mineral powder, 200 parts of fly ash and 110 parts of coal gasification slag are added.

[0066] Comparative Example 7

[0067] The difference between this comparative example and Example 1 is that 770 parts of P·O 52.5 ordinary Portland cement, 110 parts of silica fume, 110 parts of quartz powder, 110 parts of calcium powder, 550 parts of fine aggregate 1, 220 parts of fine aggregate 2, 330 parts of fine aggregate 3, 6 parts of polycarboxylic acid powder water reducer and 170 parts of water are added.

[0068] Test the compressive strength, tensile strength and chloride ion diffusion coefficient of the concrete in Examples 1 - 4 and Comparative Examples 1 - 7. The test results are shown in Table 2.

[0069] Table 2 Test Results of Concrete Properties in Examples 1 - 4 and Comparative Examples 1 - 7

[0070]

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. An alkali-activated green ultra-high performance concrete, characterized in that, By weight parts, the alkali-activated green ultra-high performance concrete comprises the following raw materials: 1100 parts of cementitious material; 120 - 160 parts of steel fiber; 1100 parts of fine aggregate; 5 - 10 parts of water reducing agent; 1 - 5 parts of alkali activator; 150 - 180 parts of water; By weight parts, the cementitious material comprises the following raw materials: 150 - 300 parts of cement; 50 - 150 parts of silica fume; 50 - 150 parts of quartz powder; 50 - 150 parts of calcium powder; 200 - 300 parts of mineral powder; 200 - 300 parts of fly ash; 50 - 100 parts of coal gasification slag.

2. The alkali-activated green ultra-high performance concrete according to claim 1, characterized in that, The fine aggregate is three continuously graded quartz sands with different particle sizes; By weight parts, the fine aggregate comprises the following raw materials: 400 - 600 parts of fine aggregate one with a particle size of 0.106 - 0.15mm; 100 - 300 parts of fine aggregate two with a particle size of 0.15 - 0.212mm; 200 - 400 parts of fine aggregate three with a particle size of 0.212 - 0.425mm.

3. The alkali-activated green ultra-high performance concrete according to claim 1, wherein The steel fiber is a cylindrical fiber with a length of 13mm and a diameter of 0.2mm, and the tensile strength is 2300MPa.

4. An alkali-activated green ultra-high performance concrete according to claim 1, characterized in that, The water reducing agent is a polycarboxylic acid powder water reducing agent, and the water reducing rate is 25%.

5. The alkali-activated green ultra-high performance concrete according to claim 1, wherein The alkali activator is at least one of solid flaky KOH, sodium hydroxide, sodium carbonate, and sodium sulfate.

6. The alkali-activated green ultra-high performance concrete according to claim 1, characterized in that, The cement is P•O 52.5 ordinary Portland cement with a density of 3.1 g / cm 3 ; the silica fume is 98 silica fume with a density of 2.2 g / cm 3 ; the particle size of the quartz powder is 2000 mesh.

7. The alkali-activated green ultra-high performance concrete according to claim 1, characterized in that The calcium powder is heavy calcium powder with a density of 2.5 g / cm 3 ; the mineral powder is S95 grade mineral powder with a density of 2.5 g / cm 3 .

8. An alkali-activated green ultra-high performance concrete according to claim 1, characterized in that, The fly ash is Class I fly ash with a density of 2.3 g / cm 3 , the particle size of the coal gasification slag is 0 - 0.045 mm, and the density is 1.8 g / cm 3 .

9. A preparation method of an alkali-activated green ultra-high performance concrete according to any one of claims 1 to 8, characterized in that, It includes the following steps: a) Mix cement, silica fume, quartz powder, calcium powder, mineral powder, fly ash, and coal gasification slag to obtain a cementitious material for standby; b) Mix the cementitious material, fine aggregate, and water reducing agent to obtain a mixture; c) Add the alkali activator to 80% of the total water amount, stir evenly, then add the mixture, continue to stir, add the remaining water, and stir evenly to obtain a slurry; d) Add steel fiber to the slurry and stir evenly to obtain a paste; e) Pour the paste into the corresponding mold, cover with a film and let it stand for 24h, then remove the mold and place it in a standard curing room for curing until 28d.

10. The preparation method of an alkali-activated green ultra-high performance concrete according to claim 9, characterized in that, The water-binder ratio of the concrete is 0.15 to 0.

18. After curing, the compressive strength at 28 days is 130 to 200 MPa, the tensile strength is 7 to 10 MPa, and the chloride ion diffusion coefficient is 0.05×10 -12 ~0.25×10 -12 .

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