Mix design method of fresh carbon-fixed concrete based on concrete fluidity adjustment

Abstract

The invention discloses a mix design method for freshly mixed solid carbon concrete based on concrete fluidity adjustment, comprising: determining the water-cement mass ratio W of the freshly mixed solid carbon concrete and its dosage, as well as the dosage of sand and gravel aggregate; the ash comprises cement, fly ash and mineral powder; determining the amount of carbon dioxide to be charged as T% of the cement mass; calculating the amount of water reducer as A% of the ash mass according to the target slump h, so as to obtain the calculated mix ratio of the freshly mixed solid carbon concrete; the mix design method of the invention believes that when carbon dioxide is added to the freshly mixed solid carbon concrete, it will quickly react chemically with the components in the cementitious material (ash), generate carbonate and precipitate from the slurry, greatly increasing the water demand of the freshly mixed solid carbon concrete, and adjusting the dosage of the water reducer to ensure the working performance of the slurry under different carbon dioxide fluxes.

Description

Technical Field

[0001] The invention belongs to the field of concrete mix design, and in particular relates to a new carbon-solidified concrete mix design method based on concrete fluidity adjustment. Background Art

[0002] Building materials are the main source of carbon emissions in the construction field and have a certain impact on global warming. It is necessary to analyze the carbon emission characteristics of building materials, deepen the understanding of building materials, and effectively apply carbon reduction and carbon fixation technologies. Carbon reduction and carbon fixation are important methods to improve building materials. It is necessary to analyze the composition of building materials and enhance the carbon fixation effect of building materials.

[0003] When carbon dioxide is added to fresh carbon-fixed concrete, the slurry will quickly react with the carbon dioxide and condense, causing a significant drop in fluidity and greatly reducing the working performance of fresh carbon-fixed concrete. If you want to prepare concrete with excellent working performance and work properly in actual applications, you should not directly apply the conventional mix design process, and you need to improve the concrete mix design process.

[0004] In the conventional mix design process, many parameters are determined based on charts and graphs, which largely rely on experience. However, there is a big difference between carbon-fixing concrete and ordinary concrete, so it is not appropriate to directly apply past experience. Summary of the invention

[0005] The purpose of the present invention is to provide a mix design method for freshly mixed solid carbon concrete based on adjustment of concrete fluidity in view of the deficiencies in the prior art. The method takes into account the incorporation of carbon dioxide in the mix design and its participation in the cement hydration reaction to form a large amount of carbonate, which greatly reduces the fluidity and has a certain gap with ordinary concrete, and should be considered differently.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows: a method for designing the mix ratio of freshly mixed carbon-fixed concrete based on concrete fluidity adjustment, comprising:

[0007] Determine the water-cement mass ratio W and its dosage of the freshly mixed carbon-solidified concrete, as well as the dosage of sand and gravel aggregate; the ash includes cement, fly ash and mineral powder;

[0008] Determine the amount of carbon dioxide to be charged as T% of the cement mass;

[0009] According to the target slump h, calculate the amount of water reducing agent as A% of the ash mass, so as to obtain the calculated mix ratio of the freshly mixed solid carbon concrete;

[0010]

[0011]

[0012]

[0013] Among them, S FA represents the influence coefficient of fly ash on the slump of carbon-fixing concrete, S MP It indicates the influence coefficient of mineral powder on the slump of carbon-fixing concrete.

[0014] Furthermore, the sand and gravel aggregate is subjected to the following screening treatment:

[0015] Screening sand and gravel aggregates with a particle size of less than 9.5 mm and greater than 4.75 mm as coarse aggregates, wherein the moisture content of the coarse aggregates is less than 0.5%;

[0016] Sand and gravel aggregates with a particle size of less than or equal to 4.75 mm are fine aggregates, and the moisture content of the fine aggregates is less than 0.2%.

[0017] Furthermore, the water-cement mass ratio W ranges from 0.4 to 0.5; the cement:fly ash mass ratio ranges from 3.6:1 to 4.4:1; and the cement:slag mass ratio ranges from 13.5:1 to 16.5:1.

[0018] Furthermore, the mass of the fine aggregate is 2 to 2.2 times the mass of cement; and the mass of the coarse aggregate is 3 to 3.2 times the mass of cement.

[0019] Furthermore, the amount of carbon dioxide accounts for 0.5% to 3% of the mass of cement, that is, T is 0.5-3.

[0020] Furthermore, the target slump h is 100 mm to 200 mm.

[0021] Furthermore, the water reducer includes a polycarboxylate water reducer.

[0022] The present invention also provides a new mixed solid carbon concrete adjusted based on concrete fluidity, which is obtained according to the above method.

[0023] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0024] 1. The mix design method of the present invention believes that the addition of carbon dioxide into freshly mixed carbon-fixed concrete will quickly react chemically with the components in the cementitious material (cement), generating a series of carbonates that precipitate from the slurry, greatly increasing the water demand of the freshly mixed carbon-fixed concrete, and adjusting the amount of water reducer to ensure the working performance of the slurry under different carbon dioxide fluxes. The design basis is clear and the operation is simple, and it is more in line with actual engineering applications.

[0025] 2. The polycarboxylic acid water reducer used in the mix of the present invention not only has high water reduction efficiency, but also does not participate in the chemical reaction between carbon dioxide and slurry (water-cement mixture). In addition, it also has the advantages of low cost and wide application range.

[0026] 3. This design can determine the mix ratio of carbon-fixing concrete according to different working performance requirements, and fully considers the difference in the effects of mixing water and water-reducing agent on fluidity in the mix ratio design, so that the slump of carbon-fixing concrete can be obtained more accurately according to the target fluidity. DETAILED DESCRIPTION

[0027] Embodiment 1:

[0028] Prepare raw materials:

[0029] Cement: 42.5 grade ordinary Portland cement, density 3100kg / m 3 ;

[0030] Fly ash: Secondary fly ash, density is 2400kg / m 3 ;

[0031] Water reducing agent: HSC polycarboxylic acid high performance water reducing agent, water reducing rate 30%, specific gravity 1.07, solid content 40%; other water reducing agents that can achieve the same water reducing effect and do not produce additional chemical reactions can be used.

[0032] Carbon dioxide: The pretreated carbon dioxide is in gaseous state, with a temperature of 20°C and a density of 1.997 g / L;

[0033] Sand and gravel aggregate: Sand and gravel aggregate with a particle size of less than 9.5mm and greater than 4.75mm are screened as coarse aggregate, and the moisture content of the coarse aggregate is less than 0.5%; sand and gravel aggregate with a particle size of less than or equal to 4.75mm is fine aggregate, and the moisture content of the fine aggregate is less than 0.2%. In order to meet the moisture content of coarse and fine aggregates, the coarse and fine aggregates are placed in a drying room for 3 to 4 days and the moisture content is measured; the drying room includes a special drying room and various drying devices, and the drying methods include natural drying, hot air drying, microwave drying, etc.

[0034] Three carbon-fixing concretes with different target slumps were selected, the water-cement ratio was determined to be 0.45 through trial mixing, and the carbon dioxide flux was set to 2%.

[0035] Taking the target slump of 100mm as an example, the distribution ratios of each group are given:

[0036] S1: Determine the water-cement mass ratio W to be 0.45;

[0037] S2: The target slump is 100 mm, and the carbon dioxide content (the percentage of carbon dioxide in cement mass) is set to 2% (i.e. T=2); the method of charging carbon dioxide is: the gas tank is placed at room temperature, and the carbon dioxide is introduced into the stirring device during the water-cement mixing, and the mixture is sealed and pressurized.

[0038] S3: Set the cement dosage mc to 270kg / m3;

[0039] S4: fly ash dosage mf is 67.5kg / m3, mineral powder dosage mk is 18kg / m3;

[0040] S5: Calculate S FA =S MP =1;

[0041] S6: Water reducing agent dosage (%)

[0042]

[0043] S7: water consumption is 159.975kg / m3;

[0044] S8: sand (fine aggregate) dosage is 540kg / m3;

[0045] S9: The amount of stone (coarse aggregate) is 810kg / m3.

[0046] The other two groups of ratios are shown in Table 1, and the performance comparison is shown in Table 2:

[0047] Table 1: Mix ratios of different target slump test groups

[0048]

[0049] Table 2: Performance test results of different target slump test groups

[0050]

[0051] Example 2: The difference from Example 1 is that the water-cement mass ratio is 0.4, the water consumption is 142.2 kg / m3; when the target slump is 100 mm, the water reducer dosage is 3.113%; when the target slump is 150 mm, the water reducer dosage is 4.78%; when the target slump is 200 mm, the water reducer dosage is 6.447%; according to these proportions, carbon-fixing concrete with target slump can be obtained.

[0052] Example 3: The difference from Example 1 is that the water-cement mass ratio is 0.5, the water consumption is 142.2 kg / m3; when the target slump is 100 mm, the water reducer dosage is 2.447%; when the target slump is 150 mm, the water reducer dosage is 4.113%; when the target slump is 200 mm, the water reducer dosage is 5.78%; according to these proportions, carbon-fixing concrete with target slump can be obtained.

[0053] Example 4: The difference from Example 1 is that the mass ratio of cement: fly ash is 3.6:1, the mass ratio of cement: mineral powder is 13.5:1, and the amount of cement remains unchanged, that is, the amount of fly ash mf is 75kg / m3, and the amount of mineral powder mk is 20kg / m3, then S FA =S MP =1.11; when the target slump is 100mm, the water reducing agent dosage is 2.152%; when the target slump is 150mm, the water reducing agent dosage is 3.505%; when the target slump is 200mm, the water reducing agent dosage is 4.857%; according to these proportions, the carbon-fixing concrete with the target slump can be obtained.

[0054] Example 5: Different from Example 1, the mass ratio of cement to fly ash is 4.4:1, the mass ratio of cement to mineral powder is 16.5:1, and the amount of cement remains unchanged, that is, the amount of mineral powder mk is 16.36 kg / m3, then S FA =S MP =0.91; when the target slump is 100mm, the water reducing agent dosage is 3.472%; when the target slump is 150mm, the water reducing agent dosage is 5.485%; when the target slump is 200mm, the water reducing agent dosage is 7.497%; according to these proportions, the carbon-fixing concrete with the target slump can be obtained.

[0055] Example 6: The difference from Example 1 is that the amount of sand is 594 kg / m3 and the amount of stone is 864 kg / m3; according to this ratio, carbon-fixing concrete with various target slumps can be obtained.

[0056] Example 7: The difference from Example 1 is that when the carbon dioxide dosage is 0.5%, the carbon dioxide dosage is 1.35 kg / m3; when the target slump is 100 mm, the water reducer dosage is 0.945%; when the target slump is 150 mm, the water reducer dosage is 2.612%; when the target slump is 200 mm, the water reducer dosage is 4.278%; according to these proportions, carbon-fixing concrete with target slump can be obtained.

[0057] Example 8: The difference from Example 1 is that when the carbon dioxide dosage is 3%, the carbon dioxide dosage is 8.1 kg / m3; when the target slump is 100 mm, the water reducer dosage is 4.003%; when the target slump is 150 mm, the water reducer dosage is 5.67%; when the target slump is 200 mm, the water reducer dosage is 7.337%; according to these proportions, carbon-fixing concrete with target slump can be obtained.

[0058] The present invention starts from the target slump, gives the required carbon dioxide dosage, comprehensively considers the difference between mixing water and water reducer for the hydration reaction and carbon fixation reaction of carbon fixation concrete, obtains the mix ratio through design calculation, and the obtained slump is very close to the target slump. Compared with the existing method, this method can determine the mix ratio of carbon fixation concrete according to different slump requirements, and directly obtains the fluidity required by the design under compression. The design idea is clear and definite, the operation is simple, the controllability is better, and it is more conducive to practical application. In terms of working performance, when the target slump is greater than 100mm, it can be applied to actual engineering.

[0059] The above is only an embodiment of the patent of the present invention, but the protection scope of the patent of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solution and inventive concept of the present invention within the scope disclosed by the patent of the present invention, which shall fall within the protection scope of the patent of the present invention.

Claims

1. A method for designing the mix ratio of freshly mixed carbon-fixed concrete based on concrete fluidity adjustment, characterized in that: include: Determine the water-cement mass ratio W and its dosage of freshly mixed carbon-solidified concrete, as well as the dosage of sand and gravel aggregate; The ash includes cement, fly ash and mineral powder; Determine the amount of carbon dioxide to be charged as T% of the cement mass; According to the target slump h, calculate the amount of water reducing agent as A% of the ash mass, so as to obtain the calculated mix ratio of the freshly mixed solid carbon concrete; Among them, S FA represents the influence coefficient of fly ash on the slump of carbon-fixing concrete, S MP It indicates the influence coefficient of mineral powder on the slump of carbon-fixing concrete.

2. The method according to claim 1, characterized in that The sand and gravel aggregate is screened as follows: Screening sand and gravel aggregates with a particle size of less than 9.5 mm and greater than 4.75 mm as coarse aggregates, wherein the moisture content of the coarse aggregates is less than 0.5%; Sand and gravel aggregates with a particle size of less than or equal to 4.75 mm are fine aggregates, and the moisture content of the fine aggregates is less than 0.2%.

3. The method according to claim 1, characterized in that The water-cement mass ratio W ranges from 0.4 to 0.5; the cement:fly ash mass ratio ranges from 3.6:1 to 4.4:1; the cement:slag mass ratio ranges from 13.5:1 to 16.5:

1.

4. The method according to claim 1, characterized in that: The mass of fine aggregate is 2 to 2.2 times the mass of cement; the mass of coarse aggregate is 3 to 3.2 times the mass of cement.

5. The method according to claim 1, characterized in that The amount of carbon dioxide accounts for 0.5% to 3% of the mass of cement, that is, T is 0.5 to 3.

6. The method according to claim 1, characterized in that The target slump h is 100 mm to 200 mm.

7. The method according to claim 1, characterized in that The water reducing agent includes a polycarboxylate water reducing agent.

8. A freshly mixed carbon-solidified concrete based on concrete fluidity adjustment, characterized in that: Obtained according to the method according to any one of claims 1 to 7.

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