CN116177959A - A preparation method of carbonized 3D printing foam concrete - Google Patents

Abstract

The invention belongs to the technical field of building materials, and particularly relates to a preparation method of carbonized 3D printing foam concrete, which comprises the following steps: placing 50-75 parts by weight of phosphorus slag, 150-175 parts by weight of water, 2-5 parts by weight of water reducer and grinding medium into an vertical ball mill for liquid phase grinding to obtain nano slurry A; step two: 10-20 parts by weight of phosphorus slag, 20-40 parts by weight of water and a grinding medium are put into a ball mill, and slurry B is obtained through liquid phase grinding; step three: 6-8 parts by weight of slurry B, 0.5-1 part by weight of synthetic surfactant, 0.2 part by weight of HPMC and 100-150 parts by weight of water are taken, magnetically stirred to prepare foaming agent C, and then foam is prepared by an air compression type foaming machine. The foam of the carbonized 3D printing foam concrete provided by the invention has the characteristics of high stability and higher carbon fixation effect, and the 3D printing material has the advantages of good bubble stability, uniform pore size distribution, high concrete strength, small shrinkage and good printability.

Description

A preparation method of carbonized 3D printing foam concrete

technical field

The invention belongs to the technical field of building materials, in particular to a method for preparing carbonized 3D printed foam concrete.

Background technique

In the past five years, the application of foam concrete technology has entered a new stage of steady growth, with an average annual growth rate of more than 15%. In the same period, 3D printing foam concrete has also become a new hot spot in the research of foam concrete industry. It is used for cement mortar Printing special-shaped wall shells, 3D printing foam concrete microstructure products or non-load-bearing structures, using physical foaming slurry to 3D print complex foam concrete products and buildings, and showing great potential for development, 3D printing foam technology and traditional Compared with the advantages of material preparation technology, on the basis of the advantages of 3D printing technology, it has the advantages of good bubble stability, uniform pore size distribution, high concrete strength, small shrinkage, and good printability.

According to the publication number CN114195463A, a concrete material for building 3D printing is disclosed, which includes powdery cementitious materials and aggregates, and the powdery cementitious materials include cement, mineral admixtures, coagulation regulators, and water reducers , defoamer, polymer powder, thixotropic agent and fiber, the material system in the cement-based composite material used in 3D printing provided by the invention does not coagulate quickly enough, has high requirements for fluidity, and the amount of chemical reagents Complicated, difficult to precisely control, and inconvenient for large-scale production.

According to the publication number CN115196923A, a solid waste-based 3D printing concrete and its preparation method are disclosed, which include 400-500 parts of Portland cement, 450-550 parts of pottery sand, 30-50 parts of fly ash, and 40-60 parts of silica fume. 60-70 parts of chopped basalt fiber, 60-70 parts of recycled coarse aggregate, 60-70 parts of recycled fine aggregate, 1-5 parts of thickener, 10-50 parts of retarder, 3-70 parts of water reducer 8 parts, 200-300 parts of water, 3D printing concrete is prepared by using recycled coarse/fine aggregate. This invention uses a large amount of aggregate, and the material system has a large weight, so the construction advantages of 3D printing cannot be reflected.

However, at present, 3D printing foam technology is still in its infancy, and there is a lack of systematic research on material systems, printing equipment, etc. The currently used 3D printing foam concrete materials have some shortcomings, mainly in: poor foam stability, formed pore distribution Disadvantages such as unevenness, low compressive strength, and large shrinkage lead to problems such as deformation after the printing material is placed, and in the later stage of cement hydration, shrinkage cracks are caused due to the large volume shrinkage of the hardened cement paste, which affects the quality of 3D printed components. Volume stability and durability, and in the selection of material systems, we choose nano phosphorus slag obtained by liquid phase grinding as the bubble stabilizer according to the current global carbon emission status and the stability mechanism of bubbles, which improves the elasticity and strength of bubbles And the pore distribution is more uniform and finer, and the material can also be used to achieve the effect of efficient carbon fixation in the wet grinding process.

Contents of the invention

Aiming at the deficiencies of the prior art, the present invention provides a method for preparing carbonized 3D printed foam concrete, which has the advantages of good bubble stability, uniform pore size distribution, high concrete strength, small shrinkage, and good printability, and solves the problems currently used The 3D printed foam concrete material has disadvantages such as poor foam stability, uneven distribution of pores formed, low compressive strength, and large shrinkage, which lead to problems such as easy deformation of the printed material after it is placed.

In order to achieve the above object, the present invention provides the following technical solution: a method for preparing carbonized 3D printed foam concrete, the specific operation process includes the following steps:

Step 1: Put 50-75 parts by weight of phosphorus slag, 150-175 parts by weight of water, 2-5 parts by weight of water reducer and grinding media into a vertical ball mill, and conduct liquid phase grinding with _CO2 gas to obtain nano-slurry A;

Step 2: Put 10-20 parts by weight of phosphorus slag, 20-40 parts by weight of water and grinding media into a ball mill, and grind in liquid phase to obtain slurry B;

Step 3: 6-8 parts by weight of slurry B, 0.5-1 parts by weight of synthetic surfactant, 0.2 parts by weight of HPMC, and 100-150 parts by weight of water are magnetically stirred to prepare foaming agent C, which is then air-compressed. Bubble machine makes foam;

Step 4: Mix and stir 135-165 parts of slurry A, 450-550 parts of Portland cement and the foam prepared in step 3, and send them into the modified 3D printer to obtain carbonized 3D printing foam concrete;

Step 5: Put the printed foam concrete in a large carbonization box for back-end carbon fixation.

Further, the water reducer in step 1 is one or more of SL type early strength water reducer, SJZ-2 early strength water reducer, and GM early strength water reducer.

Further, the parameters of liquid phase grinding in step 1 are: the grinding medium is zirconia, the particle size of zirconia is 0.6-0.8mm, 1.0-1.2mm, 1.4-1.6mm, and the ratio is 1:1: 3. The mass ratio of phosphorus slag to zirconia grinding balls is 1:1-1:3, CO ₂ with a concentration of 15%-35% and a gas velocity of 1-2 parts/h is introduced during the grinding process, and the grinding time is 40-60min , the median particle size of slurry A is not greater than 500nm.

Further, the parameters of the liquid phase grinding in step 2 are: the grinding medium is zirconia, the particle size of zirconia is 0.6-0.8mm, 0.8-1.0mm, 1.0-1.2mm, and the ratio is 1:2: 3. The mass ratio of phosphorus slag to zirconia grinding balls is 1:1-1:2, the grinding time is 40-60min, and the median particle size of slurry B is not greater than 350nm.

Further, the synthetic surfactant described in step 3 is a nano-alumina modified synthetic surfactant (NA-SS) with a hydrocarbon group as a hydrophobic group and a carboxyl group as a hydrophilic group;

Further, the magnetic stirring time in step 3 is 20min-40min.

Furthermore, the Portland cement described in Step 4 is P.O52.5, and the main components of the Portland cement are CaO, SiO ₂ , Al ₂ O ₃ , and MgO.

Further, the modification described in step 4 is to optimize the hopper of the printer, and add a setting accelerator (LSA quick-setting agent, the dosage is 1-5%) outflow device at the discharge port;

Further, the inlet conditions of the large carbonization box mentioned in step five: the superficial gas velocity of the mixed gas (CO ₂ volume fraction 20%) is 0.15m·s ^-1 , the temperature inside the carbonization box is 900±20K, and the carbonization is 3-6h.

Further, the requirements for various indicators of carbonized 3D printing foam concrete mentioned in step five: the static yield stress is 1000-1170Pa, the dynamic yield stress is 70-220Pa, and the wet density is 1510-1810kg/m ³ , so as to ensure the printability of the product sex.

Compared with the prior art, the technical solution of the present application has the following beneficial effects:

(1) It provides a feasible solution for the recycling of industrial solid waste. The industrial waste phosphorus slag is used for three purposes in one grinding, and is used for front-end carbon fixation, foam stabilizer, and concrete admixture respectively. The preparation process is simple and the operation is simple. Convenient, dust-free operating environment, low cost, suitable for large-scale industrial production.

(2) Carbon mineralization technology combined with the liquid phase grinding process of the research group can promote the rapid dissolution of metal cations in phosphorus slag, significantly improve the carbon fixation efficiency of 3D printing foam concrete slurry, and cooperate with the back-end carbon fixation technology for double carbon fixation to achieve Highest carbon sequestration utilization value.

(3) The performance of the application end of the 3D printing material is optimized, and the foamed concrete prepared by using the foaming agent modified by liquid-phase grinding phosphorus slag has good bubble stability, uniform pore size distribution, high concrete strength, small shrinkage, and Good printability and other performance.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present invention more clearly, four examples and a comparative example are listed below to further illustrate the present invention. These examples and comparative examples are only used to explain the present invention, and are not used for To limit the present invention, based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Example 1

Step 1: Put 50 parts by weight of phosphorous slag, 150 parts by weight of water, 2 parts by weight of water reducer and 300 parts by weight of zirconia balls into a vertical ball mill, and conduct liquid phase grinding in conjunction with _CO2 gas to obtain nano slurry A;

Step 2: Put 10 parts by weight of phosphorus slag, 20 parts by weight of water and 200 parts by weight of zirconia balls into a ball mill, and grind in liquid phase to obtain slurry B;

Step 3: Take 6 parts by weight of slurry B, 0.5 parts by weight of synthetic surfactant, 0.2 parts by weight of HPMC, and 100 parts by weight of water, and magnetically stir for 20 minutes to prepare foaming agent C, and then produce foam through an air compression foaming machine;

Step 4: Take 135 parts by weight of slurry A, 450 parts by weight of Portland cement and the foam prepared in step 3, mix and stir evenly, and send it to a modified 3D printer to obtain carbonized 3D printed foam concrete;

Step 5: Put the printed foam concrete in a large carbonization box for back-end carbon fixation.

Example 2

Step 1: Put 55 parts by weight of phosphorous slag, 160 parts by weight of water, 3 parts by weight of water reducing agent and 320 parts by weight of zirconia balls into a vertical ball mill, and liquid phase grinding cooperates with feeding _CO2 gas to obtain nano slurry A;

Step 2: Put 12 parts by weight of phosphorus slag, 25 parts by weight of water and 50 parts by weight of zirconia balls into a ball mill, and grind in liquid phase to obtain slurry B;

Step 3: Take 6 parts by weight of slurry B, 0.6 parts by weight of synthetic surfactant, 0.2 parts by weight of HPMC, and 120 parts by weight of water, and magnetically stir for 30 minutes to prepare foaming agent C, and then produce foam through an air compression foaming machine;

Step 4: Take 140 parts by weight of slurry A, 475 parts by weight of Portland cement and the foam prepared in step 3, mix and stir evenly, and send it to a modified 3D printer to obtain carbonized 3D printed foam concrete;

Step 5: Put the printed foam concrete in a large carbonization box for back-end carbon fixation.

Example 3

Step 1: Put 65 parts by weight of phosphorus slag, 170 parts by weight of water, 4 parts by weight of water reducing agent and 340 parts by weight of zirconia balls into a vertical ball mill, and liquid phase grinding cooperates with feeding _CO2 gas to obtain nano slurry A;

Step 2: Put 15 parts by weight of phosphorus slag, 30 parts by weight of water and 30 parts by weight of zirconia balls into a ball mill, and grind in liquid phase to obtain slurry B;

Step 3: Take 7 parts by weight of slurry B, 0.8 parts by weight of synthetic surfactant, 0.2 parts by weight of HPMC, and 140 parts by weight of water, and magnetically stir for 40 minutes to prepare foaming agent C, and then produce foam through an air compression foaming machine;

Step 4: Take 150 parts by weight of slurry A, 500 parts by weight of Portland cement and the foam prepared in step 3, mix and stir evenly, and send it to a modified 3D printer to obtain carbonized 3D printed foam concrete;

Step 5: Put the printed foam concrete in a large carbonization box for back-end carbon fixation.

Example 4

Step 1: Put 75 parts by weight of phosphorous slag, 175 parts by weight of water, 5 parts by weight of water reducing agent and 525 parts by weight of zirconia balls into a vertical ball mill, and liquid phase grinding cooperates with feeding _CO2 gas to obtain nano slurry A;

Step 2: Put 20 parts by weight of phosphorus slag, 40 parts by weight of water and 80 parts by weight of zirconia balls into a ball mill, and grind in liquid phase to obtain slurry B;

Step 3: Take 8 parts by weight of slurry B, 1 part by weight of synthetic surfactant, 0.2 parts by weight of HPMC, and 150 parts by weight of water, and magnetically stir for 40 minutes to prepare foaming agent C, and then produce foam through an air compression foaming machine;

Step 4: Take 165 parts by weight of slurry A, 550 parts by weight of Portland cement and the foam prepared in step 3, mix and stir evenly, and send it to a modified 3D printer to obtain carbonized 3D printed foam concrete;

Step 5: Put the printed foam concrete in a large carbonization box for back-end carbon fixation.

Comparative example 1

This comparative example is used to compare with Example 4, which shows that the 3D printing material prepared by the preparation method of carbonized 3D printing foam concrete provided by the present invention has good bubble stability, uniform pore size distribution, high concrete strength, small shrinkage, and Good printability and other performance.

The raw material component and consumption that adopt in this comparative example are all identical with embodiment 4, difference is, in this comparative example, do not prepare slurry B, but directly use slurry A, and divide for preparing slurry The concrete material is prepared by mixing other raw materials other than the raw materials of A, and the specific method is as follows:

Step 1: Put 75 parts by weight of phosphorous slag, 175 parts by weight of water, 5 parts by weight of water reducing agent and 525 parts by weight of zirconia balls into a vertical ball mill, and liquid phase grinding cooperates with feeding _CO2 gas to obtain nano slurry A;

Step 2: Take 1 part by weight of synthetic surfactant, 0.2 parts by weight of HPMC, and 150 parts by weight of water, and magnetically stir for 40 minutes to prepare foaming agent C, and then obtain foam through an air compression foaming machine;

Step 3: Take 165 parts by weight of slurry A, 550 parts by weight of Portland cement and the foam prepared in step 2, mix and stir evenly, and send it to a modified 3D printer to obtain carbonized 3D printed foam concrete;

Step 4: Put the printed foam concrete in a large carbonization box for back-end carbon fixation.

Carry out performance test to the mixture E1-E4 and EE1 of the carbonized foam stabilizing 3D printing that obtain in embodiment 1-4 and comparative example 1 respectively below, and test item is as follows: blowing agent viscosity, average bubble diameter, foam density, strength test, Shrinkage, cumulative carbon fixation and porosity.

The above test results are shown in Table 1 below.

Test items E1 E2 E3 E4 EE1 Blowing agent viscosity (mPa.s) 2.96 4.35 5.86 7.94 2.l3 Average bubble diameter (μm) 84.86 84.11 82.98 81.37 87.22 foam density 65.23 65.46 65.79 66.38 65.11 7d strength (MPa) 4.29 4.35 4.47 4.61 4.21 14d strength (MPa) 5.67 5.82 6.18 6.34 5.41 28d strength (MPa) 7.03 7.27 7.55 7.98 6.92 Shrinkage 0.25% 0.31% 0.34% 0.21% 0.38% Cumulative carbon fixation rate 9% 12% 14% 18% 7% Porosity(%) 59.12 58.92 58.75 58.32 59.31

Foaming agent viscosity test: Foaming agent characteristics Use a digital display viscometer to measure the viscosity of the prepared foaming agent. It is required that the measurement range of the digital viscometer used is 1-10000mPa.s, and the measurement error should be controlled within ±2%.

Bubble average diameter test: pour the 3D printed foam concrete slurry into the mold (diameter: 50mm; length: 1000mm), after curing for 7 days, cut the sample into several 30mm cylinders at intervals of 250mm, observe through a digital microscope and The microstructure of the cylinder at the position of 1000mm was photographed, the diameter of the bubbles was measured by a nanometer, and the data of the average particle diameter of the foam was obtained.

Foam density: The data obtained by X-ray micro-computed tomography were used to characterize the microstructure of the 3D printed foam concrete test block.

Shrinkage rate: test with reference to JGJ70-2009 "Basic Performance Test Method of Building Mortar".

Strength test: refer to GB/T17671-1999.

Carbon sequestration rate: Calculate with reference to "Calculation Method of Carbon Sequestration Capacity of Building Concrete Whole Life Cycle".

As can be seen from the data in Table 1, the stability and carbon fixation rate of the foam made in this printing material, due to the use of the preferred wet-grinding phosphorous slag and other relevant raw materials in different dosages in the present invention, all properties can be obtained. Various degrees of optimization. For example, the performance indicators of the 3D printed foam concrete obtained in Examples 1-4 are better than those of the comparative example, but it is not difficult to find that compared with Example 4, Examples 1-3 and Comparative Example 1, although the construction operation feasibility Better, but the performance and actual effect are far inferior to the latter, especially in the carbon fixation rate and shrinkage performance.

Therefore, it is obvious from the above table 1 that the preparation method of carbonized 3D printing foam concrete provided by the present invention can make the 3D printing material have good bubble stability, uniform pore size distribution, and concrete strength when used in 3D printing. High, small shrinkage, good printability and other properties.

In addition, the preparation method of a carbonized 3D printing foam concrete provided by the present invention is also superior to the existing common 3D printing cement-based materials. First, the foam strength and viscosity of the existing common 3D printing foam concrete are not high, resulting in Bubbles are unstable, which in turn affects shrinkage and other properties, but the invention can improve its shrinkage rate and optimize pore distribution. Moreover, the preparation method of carbonized 3D printing foam concrete provided by the present invention can be achieved through the selection of raw materials and preparation processes. Realize quick setting, reduce the demand for using a large amount of admixtures, reduce the use of admixtures, and reduce costs. Therefore, the preparation method of a carbonized 3D printing foam concrete provided by the present invention provides a new idea for 3D printing foam concrete buildings , the overall benefit is remarkable.

Mechanism of the present invention is as follows:

(1) Carbonization mechanism: The front-end carbon fixation technology utilizes the characteristics of phosphorus slag rich in calcium and magnesium active minerals, and undergoes carbon mineralization reaction with carbonate radicals generated by feeding carbon dioxide during the liquid phase grinding process, realizing CO ₂ sequestration and utilization, and the reaction The product can be used as a 3D printing cement admixture in step 3; the back-end carbon fixation technology uses the Ca(OH) ₂ in the water hydration product to react with the carbon dioxide provided by the large carbonization box, which improves the strength and strength of the 3D printing product surface. stability.

(2) Mechanism of stable bubbles: use wet grinding process to process phosphorus slag to accelerate the dissolution of calcium and magnesium ions, promote carbon mineralization reaction, use the severe mechanical force in the wet grinding process to control the particle size range of the liquid slurry after carbon mineralization, Using HPMC and nano-scale phosphorus slag slurry as foam stabilizer and thixotropic agent, the nano-scale particles obtained by liquid phase grinding have a particle size much smaller than that of cement and have a high specific surface area, so some phosphorus slag particles with water adsorbed on their surface Inevitably adsorbed on the surface of the bubbles, improving the stress environment of the bubbles, making the particle size of the bubbles tend to be uniform, the diameter of the bubbles is reduced, the pore distribution and pore size are optimized, the volume shrinkage is improved, and the rheological properties of 3D printed concrete can be improved. In order to improve its printing performance; moreover, the wet-milled phosphorous slag is rich in Ca(OH) ₂ , and the reaction of aluminum oxide on the surface of the bubbles with Ca(OH) ₂ can delay the disproportionation and coalescence of the bubbles, thereby hindering physical drainage. Improve the stability of the foam; wet grinding phosphorus slag can absorb a large amount of free energy of the liquid film, and the foam is more stable in the slurry.

(3) Strength improvement mechanism: the wet-milled phosphorus slag after carbon fixation is added to the cement, so that the foamed concrete mixed with wet-ground phosphorus slag has an excellent filling effect, which can improve the compactness of the matrix around the air bubbles, thereby improving its compression resistance strength.

The scope of protection of the present invention is not limited to the above-mentioned embodiments. Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the scope and spirit of the present invention. If these changes and modifications fall within the scope of the claims of the present invention and their equivalent technologies, the intent of the present invention is also to include these changes and modifications.

Claims (10)

1. The preparation method of the carbonized 3D printing foam concrete is characterized by comprising the following steps of:

step one: placing 50-75 parts by weight of phosphorus slag, 150-175 parts by weight of water, 2-5 parts by weight of water reducer and grinding medium into an vertical ball mill, and cooperatively introducing CO through liquid phase grinding ₂ The gas is used for obtaining nano slurry A;

step two: 10-20 parts by weight of phosphorus slag, 20-40 parts by weight of water and a grinding medium are put into a ball mill, and slurry B is obtained through liquid phase grinding;

step three: 6-8 parts by weight of slurry B, 0.5-1 part by weight of synthetic surfactant, 0.2 part by weight of HPMC and 100-150 parts by weight of water are magnetically stirred to prepare a foaming agent C, and then foam is prepared by an air compression type foaming machine;

step four: mixing 135-165 parts of slurry A,450-550 parts of silicate cement and the foam prepared in the step three, uniformly stirring, and sending the mixture into a modified 3D printer to obtain carbonized 3D printing foam concrete;

step five: and placing the printed foam concrete in a large carbonization box for rear end carbon treatment.

2. The method for preparing carbonized 3D printing foam concrete according to claim 1, wherein: the water reducer in the first step is one or more of SL-type early strength water reducer, SJZ-2-type early strength water reducer and GM-type early strength water reducer.

3. The method for preparing carbonized 3D printing foam concrete according to claim 1, wherein: the liquid phase grinding parameters in the first step are as follows: the grinding medium is zirconia, the grain diameter of the zirconia is 0.6-0.8mm, 1.0-1.2mm and 1.4-1.6mm, and the proportion is 1:1:3, the mass ratio of the phosphorus slag to the zirconia grinding ball is 1:1-1:3, introducing CO with the concentration of 15-35% and the gas speed of 1-2 parts/h in the grinding process ₂ Grinding time is 40-60min, and the median particle diameter of slurry A is not more than 500nm.

4. The method for preparing carbonized 3D printing foam concrete according to claim 1, wherein: the liquid phase grinding parameters in the second step are as follows: the grinding medium is zirconia, the grain diameter of the zirconia is 0.6-0.8mm, 0.8-1.0mm and 1.0-1.2mm, and the proportion is 1:2:3, the mass ratio of the phosphorus slag to the zirconia grinding ball is 1:1-1:2, grinding time is 40-60min, and median particle size of slurry B is not more than 350nm.

5. The method for preparing carbonized 3D printing foam concrete according to claim 1, wherein: and in the third step, the synthetic surfactant is a nano alumina modified synthetic surfactant (NA-SS) with a hydrocarbon group as a hydrophobic group and a carboxyl group as a hydrophilic group.

6. The method for preparing carbonized 3D printing foam concrete according to claim 1, wherein: and in the third step, the magnetic stirring time is 20-40 min.

7. The method for preparing carbonized 3D printing foam concrete according to claim 1, wherein: in the fourth step, the silicate cement is P.O52.5, and the main components of the silicate cement are CaO and SiO ₂ 、Al ₂ O ₃ 、MgO。

8. The method for preparing carbonized 3D printing foam concrete according to claim 1, wherein: in the fourth step, the modification is to optimize the hopper of the printer, and a coagulant (LSA accelerator, the mixing amount is 1-5%) is added at the discharge port to flow out of the device.

9. The method for preparing carbonized 3D printing foam concrete according to claim 1, wherein: in the fifth step, the inlet condition of the large carbonization box is as follows: mixed gas (CO) ₂ 20% by volume) apparent gas velocity of 0.15 mS ^－1 The temperature in the carbonization box is 900+/-20K, and the carbonization is carried out for 3-6 hours.

10. The method for preparing carbonized 3D printing foam concrete according to claim 1, wherein: in the fifth step, the carbonized 3D printing foam concrete has various index requirements: the static yield stress is 1000-1170Pa, the dynamic yield stress is 70-220 Pa, and the wet density is 1510-1810kg/m ³ To ensure printability of the product.