Phase change heat storage white ultra-high performance concrete and preparation method thereof

Abstract

The invention discloses phase-change heat-storage white ultra-high-performance concrete and a preparation method thereof, and relates to the field of ultra-high-performance cement-based materials and building energy conservation. The concrete is prepared from water and a premix, wherein the premix is prepared from 30-40 parts of white Portland cement, 25-45 parts of graded sand, 5-20 parts of composite phase change aggregate, 2-10 parts of white silica fume, 5-20 parts of slag powder, 0.3-1.2 parts of a water reducing agent, 0.1-0.6 part of a defoaming agent, 0.5-2 parts of titanium dioxide and 1-8 parts of basalt fiber. The high-activity white silica fume and the modified phase-change aggregate are used, and the framework effect of the basalt fiber grid is combined, so that the working performance of the concrete is improved, the concrete has excellent heat storage capacity and high-strength mechanical property, and compared with an existing decorative ultra-high-performance concrete material, the decorative ultra-high-performance concrete material has the advantages that the construction cost is reduced, and the construction efficiency is improved. And meanwhile, the integrated functions of temperature adjustment, decoration and structure are achieved.

Description

Technical Field

[0001] The present invention relates to the fields of ultra-high performance cement-based materials and building energy conservation, and specifically relates to a phase change heat storage white ultra-high performance concrete and a preparation method thereof. Background Art

[0002] In recent years, ultra-high performance concrete has been undergoing a transformation and breakthrough from traditional structural materials to multifunctional composite materials, resulting in the development of a white ultra-high performance concrete in the direction of decorative concrete. This is a high-performance cement-based material prepared with white Portland cement as the gelling core, compounded with mineral admixtures, light-colored aggregates, and functional admixtures, etc., with both high whiteness and ultra-high mechanical properties, which can significantly improve the aesthetics and stability of building structures.

[0003] Currently, buildings have high energy consumption during operation, while phase change concrete shows great application potential in reducing building operation energy consumption. Therefore, applying the functional core of phase change concrete, the phase change aggregate, to white ultra-high performance concrete can significantly reduce building energy consumption, and a phase change heat storage white ultra-high performance concrete can be prepared, which not only exhibits excellent decorative and structural properties, but also has the ability of heat storage and temperature regulation due to its absorption or release of a large amount of latent heat, and can effectively achieve energy conservation and consumption reduction of concrete structures, reduce structural self-weight, and reduce shrinkage effects. In this process, the phase change aggregate is the key component to achieve the heat storage function. However, the incorporation of the phase change aggregate may have a negative impact on the workability and mechanical properties of the material.

[0004] At present, there is no relevant technology for studying the heat storage performance of decorative white cement-based ultra-high performance concrete. Based on this, the present invention proposes an innovative technology for synergistically improving heat storage and high performance, and can prepare a white ultra-high performance concrete with a phase change heat storage function. Summary of the Invention

[0005] The purpose of the present invention is to propose a phase change heat storage white ultra-high performance concrete and a preparation method thereof, which have the integrated functions of temperature regulation, decoration, and structure.

[0006] In order to achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] A phase change heat storage white ultra-high performance concrete is prepared by mixing according to a mass ratio of water to premix of 0.09 - 0.11:1, wherein the premix consists of 30 - 40 parts of white Portland cement, 25 - 45 parts of graded sand, 5 - 20 parts of composite phase change aggregate, 2 - 10 parts of white silica fume, 5 - 20 parts of slag powder, 0.3 - 1.2 parts of water reducing agent, 0.1 - 0.6 parts of defoaming agent, 0.5 - 2 parts of titanium dioxide, and 1 - 8 parts of basalt fiber.

[0008] As a preferred technical solution of the present invention, in the components of the phase change heat storage white ultra-high performance concrete:

[0009] The strength grade of the white Portland cement is P.W.52.5, and the whiteness ≥ 87%;

[0010] The graded sand is quartz sand, with particle gradations of 0.1mm - 0.3mm, 0.3mm - 0.5mm, and 0.5 - 1.0mm, bulk density of 1600 - 1700g / L, and water absorption rate ≤ 4%;

[0011] The fineness of the white silica fume is 8000 mesh, 28d activity index ≥ 120%, and whiteness ≥ 92%;

[0012] The slag powder is S95 grade slag powder, 28d activity index ≥ 95%, and whiteness ≥ 85%;

[0013] The water reducing agent is a polycarboxylate superplasticizer, and the mortar water reducing rate ≥ 22%;

[0014] The defoaming agent is a mineral oil defoaming agent;

[0015] The titanium dioxide is rutile titanium dioxide, and the whiteness ≥ 96%;

[0016] The basalt fiber is basalt fiber for reinforcement, with a length of 12mm, thermal conductivity coefficient of 0.035W / (m·K), and tensile strength ≥ 3000MPa.

[0017] As a preferred technical solution of the present invention, the composite phase change aggregate in the components of the phase change heat storage white ultra-high performance concrete is composed of a phase change core and a coating layer. The phase change core is made by shale ceramsite adsorbing one or more phase change materials such as octadecane, octadecanol, paraffin, and fatty acid. The coating layer is obtained by encapsulating the phase change core with sodium silicate gel and calcium silicate gel to prevent the leakage of the phase change material components.

[0018] As a preferred technical solution of the present invention, the preparation method of the composite phase change aggregate in the phase change heat storage white ultra-high performance concrete components is as follows: Heat the phase change material in a reaction vessel until it melts into a liquid state, then wash and dry the shale ceramsite and put it into the phase change material until it is completely immersed; then put the container filled with ceramsite and phase change material into an oven at 100 °C for 2 h of impregnation treatment, and stir it every 30 min during this period; then adjust the oven to 80 °C and continue to keep it warm for 2 h to form a phase change core with stable morphology; finally, put the prepared phase change core into a coating machine, add Ca(OH)2 powder and a Na2SiO3 solution with a concentration of 30-50%, and stir evenly for 10-30 min; during the stirring process, CaSiO3 generated by the reaction of Na2SiO3 and Ca(OH)2, as well as the unreacted Na2SiO3 jointly coat the phase change core completely, and it is naturally dried to obtain the final composite phase change aggregate.

[0019] As a further preferred technical solution of the present invention, the shale ceramsite is 900-grade shale ceramsite with a particle size of ≤ 3 mm; the addition ratio of the shale ceramsite, phase change material, calcium hydroxide, and sodium silicate solution is 0.681:0.319:1:0.6.

[0020] The present invention also proposes a preparation method of a phase change heat storage white ultra-high performance concrete, including the following steps:

[0021] Weigh the raw materials according to the ratio, stir the premix except for basalt fiber in a mixer for more than 2 min until it is evenly mixed, then add water and continue to mix and stir for 4-5 min until the mixture is close to the target fluidity, and then slowly add basalt fiber again, and stir for more than 2 min until it is evenly dispersed and then use it directly.

[0022] The phase change heat storage white ultra-high performance concrete prepared by the present invention has a thermal conductivity of less than 0.9 W / (m·K); the initial fluidity ≥ 280 mm, and the fluidity after 30 min ≥ 260 mm; the compressive strength at 28 d is not less than 110 MPa, the flexural strength is not less than 20 MPa, and the slurry density is 2300 kg / m 3 -2400 kg / m 3 。

[0023] The present invention adjusts the ratio of white Portland cement, active admixture, fine aggregate, basalt fiber, high-performance water reducer, and defoamer, and uses highly active white silica fume and phase change aggregate treated by modification, and combines with the framework effect of basalt fiber grid, which not only improves the workability of the concrete, but also its excellent heat storage capacity and high-strength mechanical properties, compared with the existing decorative ultra-high performance concrete materials, it has the integrated functions of temperature regulation, decoration, and structure at the same time.

[0024] In the present invention, the white silica fume used in the active admixture contains a large amount of highly active oxides such as SiO2, which reacts with the cement hydration product Ca(OH)2 to form a cementitious C-S-H gel. The S95 slag powder can fill the voids between cement particles, replace the unhydrated cement particles to play a filling role, optimize the particle gradation of the material, and thus improve the density of the concrete. In addition, a high content of slag powder can significantly reduce the cement consumption and reduce the material cost.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] (1) In the steps of preparing the phase change heat storage white ultra-high performance concrete of the present invention, white silica fume with high whiteness (whiteness ≥ 92%) and slag powder (whiteness ≥ 85%) are used, and high whiteness titanium dioxide (whiteness ≥ 96%) is supplemented to enhance the whiteness. And this ratio helps to improve the mechanical properties and fluidity of the phase change heat storage white ultra-high performance concrete, and while maintaining the concrete performance, reduces the usage ratio of white Portland cement.

[0027] (2) For the preparation of the phase change core of the composite phase change aggregate, porous ceramsite is used to adsorb the selected phase change materials, including octadecane, octadecanol, paraffin wax and fatty acids, and then encapsulated with sodium silicate gel and calcium silicate gel to prepare a coating layer to ensure the protection of the core of the phase change material and prevent the leakage of the phase change components. At the same time, it can endow the phase change aggregate with characteristics such as high strength, excellent durability and heat storage performance.

[0028] (3) By optimizing the volume content of basalt fiber to 1.0% and incorporating up to 20% of the composite phase change aggregate, this ratio helps to improve the heat storage capacity of the white ultra-high concrete, reduce the carbon emissions during the preparation and use of the white ultra-high performance concrete, and conforms to the green and environmental protection preparation concept of ultra-high performance concrete.

[0029] (4) Compared with the similar white ultra-high performance concrete, the present invention uses low-cost slag powder as an auxiliary cementitious material, combines white silica fume with a relatively high composite activity index and uses basalt fiber for synergistic reinforcement to improve the mechanical properties of the white ultra-high performance concrete. Through the optimized preparation of the phase change aggregate core, the heat storage performance of the white ultra-high performance concrete is optimized, and it has both high fluidity and whiteness. Description of the Drawings

[0030] Figure 1 It is the heating infrared thermal image of the phase change heat storage white ultra-high performance concrete.

[0031] Figure 2 It is the cooling infrared thermal image of the phase change heat storage white ultra-high performance concrete. Detailed Embodiments

[0032] The present invention will be further described in detail below in conjunction with embodiments and the accompanying drawings.

[0033] Preparation of composite phase change aggregate:

[0034] Put the container filled with shale ceramsite and paraffin into an oven at 100 °C for 2 h of impregnation treatment, and stir once every 30 min during this period. Adjust the oven to 80 °C and continue to keep warm for 2 h to form a phase change ceramsite core with stable morphology. Then, put the prepared phase change core into a coating machine, add Ca(OH)2 powder and a Na2SiO3 solution with a concentration of 43.5%, and stir evenly for 20 min. During the stirring process, CaSiO3 generated by the reaction of Na2SiO3 and Ca(OH)2, as well as the unreacted Na2SiO3 together completely coat the phase change core, and it is naturally dried to obtain the final phase change aggregate. During its encapsulation process, the weight ratio of shale ceramsite, paraffin, calcium hydroxide, and sodium silicate solution is 0.681:0.319:1:0.6.

[0035] Comparative Example 1

[0036] A phase change heat storage white ultra-high performance concrete is composed of water and a premix in a mass ratio of 0.107:1. The premix includes the following raw materials in parts by weight: 769 g of white Portland cement, 878 g of quartz sand, 0 g of composite phase change aggregate, 231.8 g of slag powder, 52.6 g of white silica fume, 10.6 g of water reducing agent, 3.2 g of defoaming agent, 31.6 g of titanium dioxide, and 23.2 g of basalt fiber.

[0037] Weigh the raw materials according to the ratio, stir the premix except basalt fiber in a mixer for 5 min to mix evenly, then add water and continue to mix and stir for 5 min until the mixture is close to the target fluidity, and then slowly add basalt fiber again and stir for 5 min until it is evenly dispersed and then use directly.

[0038] Comparative Example 2

[0039] A phase change heat storage white ultra-high performance concrete is composed of water and a premix in a mass ratio of 0.107:1. The premix includes the following raw materials in parts by weight: 769 g of white Portland cement, 834 g of quartz sand, 44 g of composite phase change aggregate, 231.8 g of slag powder, 52.6 g of white silica fume, 10.6 g of water reducing agent, 3.2 g of defoaming agent, 31.6 g of titanium dioxide, and 23.2 g of basalt fiber.

[0040] The preparation method is the same as that of Comparative Example 1.

[0041] Comparative Example 3

[0042] A phase change heat storage white ultra-high performance concrete is composed of water and a premix in a mass ratio of 0.107:1. The premix includes the following raw materials in parts by weight: 769 g of white Portland cement, 790.2 g of quartz sand, 87.8 g of composite phase change aggregate, 231.8 g of slag powder, 52.6 g of white silica fume, 10.6 g of water reducing agent, 3.2 g of defoaming agent, 31.6 g of titanium dioxide, and 23.2 g of basalt fiber.

[0043] The preparation method is the same as that of Comparative Example 1.

[0044] Comparative Example 4

[0045] A phase change heat storage white ultra-high performance concrete is composed of water and a premix in a mass ratio of 0.107:1. The premix includes the following raw materials in parts by weight: 769 g of white Portland cement, 746.2 g of quartz sand, 131.8 g of composite phase change aggregate, 231.8 g of slag powder, 52.6 g of white silica fume, 10.6 g of water reducing agent, 3.2 g of defoaming agent, 31.6 g of titanium dioxide, and 23.2 g of basalt fiber.

[0046] The preparation method is the same as that of Comparative Example 1.

[0047] Example 1

[0048] A phase change heat storage white ultra-high performance concrete is composed of water and a premix in a mass ratio of 0.107:1. The premix includes the following raw materials in parts by weight: 769 g of white Portland cement, 702.4 g of quartz sand, 175.6 g of composite phase change aggregate, 231.8 g of slag powder, 52.6 g of white silica fume, 10.6 g of water reducing agent, 3.2 g of defoaming agent, 31.6 g of titanium dioxide, and 23.2 g of basalt fiber.

[0049] The preparation method is the same as that of Comparative Example 1.

[0050] The raw materials used in the preparation processes of Example 1 and Comparisons 1 - 4 are as follows:

[0051] The strength grade of the white Portland cement used is P.W. 52.5, and the whiteness is ≥87%. The graded sand used is quartz sand, with particle size gradations of 0.1mm - 0.3mm, 0.3mm - 0.5mm, and 0.5 - 1.0mm, bulk density of 1600 - 1700g / L, and water absorption rate ≤4%. The fineness of the white silica fume used is 8000 mesh, 28-day activity index ≥120%, and whiteness ≥92%. The slag powder used is S95 grade slag powder, 28-day activity index ≥95%, and whiteness ≥85%. The water reducer used is a polycarboxylate superplasticizer, and the mortar water reduction rate ≥22%. The defoamer used is a mineral oil defoamer. The titanium dioxide used is rutile titanium dioxide, and the whiteness ≥96%. The basalt fiber used is basalt fiber for reinforcement, with a length of 12mm, thermal conductivity coefficient of 0.035W / (m·K), and tensile strength ≥3000MPa.

[0052] The component proportions of Phase Change Heat Storage White Ultra-High Performance Concrete prepared in Example 1 and Comparative Examples 1 - 4 are shown in Table 1.

[0053] Table 1 Component Proportions of Phase Change Heat Storage White Ultra-High Performance Concrete

[0054]

[0055] Note:

[0056] WPC: White Portland Cement; SP: Slag Powder; WSF: White Silica Fume; the corresponding percentages represent the proportions in the cementitious materials. PCM: Composite Phase Change Aggregate; QS: Quartz Sand; the corresponding percentages represent the proportions in the aggregate. PCE: Water Reducer; DF: Defoamer; TD: Titanium Dioxide; the corresponding percentages represent the proportions by weight of the cementitious materials. BF: Basalt Fiber, the corresponding percentage represents the proportion in the total volume of the concrete. W / B: Water-cement ratio 0.2. B / S: Cement-sand ratio.

[0057] The test methods for the Phase Change Heat Storage White Ultra-High Performance Concrete prepared in Example 1 and Comparative Examples 1 - 4 are as follows, and the test results are shown in Table 2.

[0058] ① Fluidity test: GB / T 2419-2016 "Test Method for Fluidity of Cement Mortar" (without starting the vibrating table).

[0059] ② Flexural strength test: GBT17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)".

[0060] ③ Compressive strength test: GBT17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)".

[0061] ④ Whiteness test: T / CECS1420-2023 "Technical Specification for Application of White Concrete".

[0062] ⑤ Thermal conductivity test: GB / T 10294-2008 Determination of Steady-State Thermal Resistance and Related Properties of Thermal Insulation Materials - Guarded Hot Plate Method.

[0063] Table 2 Test results of various properties of phase change heat storage white ultra-high performance concrete

[0064]

[0065] The test results of the above-mentioned phase change heat storage white ultra-high performance concrete show that it has excellent fluidity. In Example 1, after adding 20% of the phase change aggregate, the compressive strength of the concrete reaches over 110 MPa.

[0066] Figure 1 It shows the surface temperature distribution image of the sample captured by the infrared thermal imager after the heating ends. When the heating terminates, the temperature of Comparative Example 1 is 38.2 °C, while the temperature of Example 1 is 37.5 °C, and both show red. As time goes by, after natural cooling for 30 min, the surface temperature of Example 1 reaches the highest, which is 3.7 °C higher than that of Control Group 1 ( Figure 2 as shown).

[0067] Generally speaking, with the increase of the content of the composite phase change aggregate, the cooling rate of the phase change heat storage white ultra-high performance concrete decreases. Therefore, after adding the phase change aggregate, the thermophysical properties of the material are double-optimized: on the one hand, the overall thermal conductivity is significantly reduced, and on the other hand, the heat capacity energy storage density is increased. This synergistic effect leads to a decrease in the temperature response rate of the material surface to the change of the thermal environment, specifically manifested as an obvious decrease in the slope of the temperature curve during the heating / cooling process. Among them, the white ultra-high performance concrete containing the phase change aggregate has a lower heating / cooling rate compared with the white ultra-high performance concrete without the phase change aggregate, because the phase change latent heat of the phase change aggregate is higher, making the phase change heat storage white ultra-high performance concrete prepared from this material have stronger heat storage capacity.

[0068] The above content is only an example and explanation of the concept of the present invention. Those skilled in the art of this technology can make various modifications or supplements to the described specific embodiments or use similar methods for substitution, as long as they do not deviate from the concept of the invention or exceed the scope defined by this claim book, they should all belong to the protection scope of the present invention.

Claims

1. A phase-change heat storage white ultra-high performance concrete, prepared by mixing water and premix at a mass ratio of 0.09-0.11:1, characterized in that: The premix consists of 30-40 parts of white silicate cement, 25-45 parts of graded sand, 5-20 parts of composite phase change aggregate, 2-10 parts of white silica fume, 5-20 parts of slag powder, 0.3-1.2 parts of water reducer, 0.1-0.6 parts of defoamer, 0.5-2 parts of titanium dioxide and 1-8 parts of basalt fiber.

2. The phase-change heat storage white ultra-high performance concrete according to claim 1, characterized in that: The strength grade of the white silicate cement is PW52.5, and the whiteness is ≥87%; The graded sand is quartz sand with a particle size of 0.1mm-0.3mm, 0.3mm-0.5mm and 0.5-1.0mm, a bulk density of 1600-1700g / L, and a water absorption rate of ≤4%; The white silica fume has a fineness of 8000 mesh, a 28d activity index of ≥120%, and a whiteness of ≥92%; The slag powder is S95 grade slag powder, with a 28d activity index of ≥95% and a whiteness of ≥85%; The water reducing agent is a polycarboxylic acid high-efficiency water reducing agent, and the water reducing rate of the mortar is ≥22%; The defoamer is a mineral oil defoamer; The titanium dioxide is rutile titanium dioxide with a whiteness of ≥96%; The basalt fiber is a reinforcing basalt fiber with a length of 12 mm, a thermal conductivity coefficient of 0.035 W / (m·K), and a tensile strength of ≥3000 MPa.

3. The phase-change heat storage white ultra-high performance concrete according to claim 1, characterized in that: The composite phase change aggregate consists of a phase change core and a coating layer. The phase change core is made of shale ceramsite adsorbing one or more phase change materials such as octadecane, octadecyl alcohol, paraffin and fatty acid. The coating layer is made by encapsulating the phase change core by coating the phase change core with sodium silicate gel and calcium silicate gel. The composite phase change aggregate prevents leakage of phase change material components.

4. The phase-change heat storage white ultra-high performance concrete according to claim 3, characterized in that: The preparation method of the composite phase change aggregate is as follows: heating and melting the phase change material into a liquid in a reaction container, then washing and drying the shale expanded clay, and then putting it into the phase change material to completely immerse it; then putting the container containing the expanded clay and the phase change material into an oven at 100°C for 2 hours of immersion treatment, stirring once every 30 minutes; then adjusting the oven to 80°C and continuing to keep warm for 2 hours to form a phase change core with a stable morphology; finally putting the prepared phase change core into a coating machine, adding Ca(OH)2 powder and a 30-50% concentration of Na2SiO3 solution, and stirring evenly for 10-30 minutes; during the stirring process, the CaSiO3 generated by the reaction of Na2SiO3 and Ca(OH)2, and the unreacted Na2SiO3 together completely cover the phase change core, and naturally drying to obtain the final composite phase change aggregate.

5. The phase-change heat storage white ultra-high performance concrete according to claim 3 or 4, characterized in that: The shale ceramsite is 900-grade shale ceramsite with a particle size of ≤3 mm; the addition ratio of the shale ceramsite, phase change material, calcium hydroxide and sodium silicate solution is 0.681:0.319:1:0.

6.

6. A method for preparing the phase-change heat storage white ultra-high performance concrete according to any one of claims 1 to 5, characterized in that: The following steps are involved: Weigh the raw materials according to the ratio, stir the premix except basalt fiber in a mixer for more than 2 minutes to mix evenly, then add water and continue mixing and stirring for 4-5 minutes until the mixture is close to the target fluidity, slowly add basalt fiber again, stir for more than 2 minutes to disperse evenly, and then use it directly.

7. The method according to claim 6, characterized in that The prepared phase change heat storage white ultra-high performance concrete has a thermal conductivity of less than 0.9W / (m·K); an initial fluidity of ≥280mm, and a 30min fluidity of ≥260mm; 28d compressive strength is not less than 110MPa, flexural strength is not less than 20MPa, slurry bulk density is 2300kg / m 3 -2400kg / m 3 .

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