Daytime radiant cooling Portland cement and method of making same

Abstract

The application provides a daytime radiative cooling Portland cement and a preparation method thereof. The application is prepared by mixing granularly graded fused quartz powder, silane coupling agent modified nano titanium dioxide, triethanolamine and polycarboxylic acid water reducing agent with ordinary Portland cement. In the preparation, the three fused quartz powders with different particle sizes are first mixed, then the nano titanium dioxide is modified by the silane coupling agent, and then the cement is dry mixed, finally, the aqueous solution containing triethanolamine and water reducing agent is added and stirred to form. The application has the advantages of wide raw material sources and simple process, and the preparation process is carried out at normal temperature and pressure, which is suitable for the existing cement construction process. The solar reflectivity and thermal emissivity of the obtained cement both reach more than 80%, the attenuation after 500 hours of accelerated aging is less than 5%, the compressive strength meets the requirements of structural materials, and efficient daytime passive cooling can be realized. The material has good application prospect when used for radiative cooling of building outer walls, ground and other scenes.

Description

Technical Field

[0001] This invention relates to the field of silicate cement technology, specifically to a daytime radiation-cooled silicate cement and its preparation method. Background Technology

[0002] Radiative cooling technology transfers surface heat to outer space via atmospheric windows in the form of infrared radiation, achieving passive cooling without energy input. It has significant application value in areas such as building energy conservation and mitigation of urban heat islands. Gray silicate cement, as the world's most widely used building material, accounts for a very high proportion of existing buildings. Imparting efficient radiative cooling capabilities to it would have a profound impact on reducing building cooling energy consumption and contributing to carbon neutrality goals. However, due to the presence of hydration products (such as CSH gel) and iron-containing phases (such as Fe2O3), gray silicate cement exhibits strong absorption of visible-near-infrared sunlight. Its intrinsic light reflectivity and mid-infrared emissivity are both low, making it difficult to directly meet the needs of daytime radiative cooling.

[0003] Patent CN120574005A, entitled "A Boron-Reinforced Cement-Based Radiative Cooling Composite Material," discloses a technical solution that uses an ice template method for low-temperature freezing to construct a directional porous structure, combined with high-temperature calcination to induce an oxidative phase transformation of boride ceramic micropowder, thereby generating a highly reflective mineral phase. While this method can achieve radiative cooling, its preparation process is complex and energy-intensive, making it unsuitable for on-site cast-in-place construction. Furthermore, its excellent radiative cooling performance is difficult to achieve under ordinary ambient temperature curing conditions, severely limiting its application scenarios and hindering large-scale promotion.

[0004] Patent CN118006149A, "A Recycled Milky White Glass Powder Radiation-Coating Polymer Cement Coating," discloses a method of constructing micro-nano structures on the cement surface to achieve superhydrophobicity and radiation cooling by compounding two types of modified milky white glass powder with modified silicone-acrylic emulsion. However, the coating inevitably faces problems such as weathering, peeling, and wear during long-term service, leading to a rapid decline in optical properties over time. Furthermore, the system incorporates a large amount of organic emulsion and various modifying additives, which sacrifices the inherent mechanical properties of the cement matrix.

[0005] In summary, existing technologies that reconstruct the microstructure of cement through special processes or apply functional coatings to the cement surface both have unavoidable drawbacks: the former relies on complex and energy-intensive processes, making it incompatible with existing production and construction systems; the latter suffers from poor coating durability and the weakening of matrix properties by organic components. Therefore, developing a silicate cement material that combines high radiative cooling performance, good process compatibility, and long-term service stability is of great significance. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a daytime radiation-cooled silicate cement and its preparation method, solving the technical problem that "existing silicate cement is difficult to achieve synergistic improvement of light reflectivity and emissivity".

[0007] To achieve the above objectives, the present invention is implemented using the following technical solution: This invention provides a method for preparing daytime radiation-cooled silicate cement, comprising the following steps: (1) Mix the first-size fused silica powder, the second-size fused silica powder and the third-size fused silica powder in proportion to obtain fused silica powder with particle size distribution; (2) The nano-titanium dioxide was surface modified with a silane coupling agent to obtain modified nano-titanium dioxide; (3) First, dry mix the ordinary silicate cement and the particle size distribution of the fused silica powder prepared in step (1) for the first time. Then, add the modified nano titanium dioxide prepared in step (2) for the second dry mix. After the dry mix is ​​completed, add an aqueous solution containing triethanolamine and water-reducing agent within 30 to 60 seconds. Continue to add water for wet mixing and stir to obtain cement slurry. (4) Pour the above cement slurry into the mold, vibrate to form, cover with film and let stand, cure according to standard and dry, take out and cool naturally to room temperature to obtain day radiation cooled silicate cement.

[0008] As a preferred embodiment, the cement slurry, by weight, comprises 100 parts of ordinary Portland cement and 3-10 parts of particle-graded fused silica powder, which are first dry-mixed at a speed of 50-100 r / min for 0.5-1.5 min, followed by the addition of 5.4-12 parts of modified nano-titanium dioxide for a second dry-mixing, and then 0.3-0.8 parts of triethanolamine, 0.1-0.3 parts of water-reducing agent, and a total of 29-39 parts of mixing water.

[0009] As a preferred embodiment, the mass percentages of the first-size fused silica powder, the second-size fused silica powder, and the third-size fused silica powder are 20-30%: 60-70%: 10-20%.

[0010] As a preferred embodiment, the mass ratio of the nano-titanium dioxide to the silane coupling agent is 1:(1~5%).

[0011] As a preferred embodiment, the nano-titanium dioxide is anatase phase. By utilizing the high refractive index and broad-spectrum absorption characteristics of nano-titanium dioxide in the ultraviolet-visible region, an optical heterogeneous interface is constructed in the cement matrix to enhance the solar reflectivity.

[0012] As a preferred embodiment, the first particle size of the particle-graded fused silica powder is 1~5μm, the second particle size is 8~15μm, and the third particle size is 20~30μm; the particle size of the nano-titanium dioxide is 20~50nm; the mass ratio of the particle-graded fused silica powder to the modified nano-titanium dioxide is 1:(1.2~1.8). By optimizing the particle size matching and mass ratio relationship between the two, multi-level light scattering and radiation channels can be constructed.

[0013] As a preferred embodiment, the rotation speed of the first dry mixing is 50~100 r / min and the time is 0.5~1.5 min; the time of the second dry mixing is 1~2 min.

[0014] As a preferred embodiment, the injection time of the aqueous solution containing triethanolamine and water-reducing agent is 10-20 seconds, which can reduce the risk of bubble aggregation and abnormal slow coagulation caused by excessively high local concentration.

[0015] As a preferred embodiment, the wet mixing speed is 60~80 r / min and the time is 2~4 min, so that triethanolamine can be introduced after the cement particles are initially wetted, which can effectively adsorb onto the surface of the newly generated hydration products, and avoid premature participation in the reaction, which would prolong the induction period.

[0016] As a preferred embodiment, the heating rate of the drying process in step (4) is 5~10℃ / h, the temperature is 55~65℃, and the holding time is 3~5h.

[0017] Compared with the prior art, the beneficial effects achieved by the present invention are: (1) The invention uses a multi-particle-size graded fused silica powder combined with a silane-modified nano-titanium dioxide composite system to construct multi-level light scattering and infrared radiation channels in the cement matrix, thereby synergistically improving solar reflectivity and atmospheric window thermal emissivity.

[0018] (2) Under simulated constant temperature irradiation conditions, the average and maximum temperatures of the sample surface are significantly lower than those of the reference cement. The average temperature is reduced by 6.4℃ and the maximum temperature is reduced by 7.1℃ compared with ordinary gray cement, thus achieving a stable and efficient daytime passive radiation cooling effect.

[0019] (3) After 500 hours of accelerated UV aging, the solar reflectance and thermal emissivity of the sample decreased by less than 5%, the optical performance retention rate was high, the long-term service stability and aging resistance were outstanding, and it was highly compatible with the existing cement production and cast-in-place construction system, and had good engineering application and industrial promotion value. Attached Figure Description

[0020] Figure 1 The curves show the changes in reflectance and emissivity of the samples of this invention under different aging times.

[0021] Figure 2 This is a comparison chart of the average and maximum surface temperatures of the silicate cement of this invention and ordinary gray cement. Detailed Implementation

[0022] 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.

[0023] This invention provides a method for preparing daytime radiation-cooled silicate cement, comprising the following steps: (1) The first particle size fused silica powder, the second particle size fused silica powder and the third particle size fused silica powder are mixed in mass percentage (20~30%): (60~70%): (10~20%) to obtain fused silica powder with particle size distribution; this step constructs a continuous microcrystalline phase structure in the cement matrix through the distribution of three particle sizes, and lays the foundation for high thermal emissivity by utilizing the intrinsic infrared emission characteristics of fused silica powder in the 8-13μm atmospheric window. At the same time, the multi-particle size distribution can form a multi-level scattering interface to help improve the solar reflectivity; (2) Disperse nano-titanium dioxide in ethanol, add 1-5% by mass of nano-titanium dioxide silane coupling agent KH-550, stir at 25-30℃ for 1-2 hours, filter and dry to obtain modified nano-titanium dioxide; This step modifies the surface of nano-titanium dioxide by silane coupling agent, inhibits particle agglomeration, and makes it uniformly dispersed in cement paste. With its high refractive index, it significantly enhances the light scattering of visible-near infrared bands, thereby improving the solar reflectivity. (3) By mass, 100 parts of ordinary gray silicate cement and 3-10 parts of particle-graded fused silica powder are placed in a mixer and dry-mixed at 50-100 r / min for 0.5-1.5 min. Then, 5.4-12 parts of modified nano titanium dioxide are added and dry-mixed for 1-2 min. 0.3-0.8 parts of triethanolamine and 0.1-0.3 parts of polycarboxylate superplasticizer are dissolved in 25-30 parts of water and injected into the mixer within 30-60 seconds after dry mixing. The injection time is controlled within 10-20 seconds. Then, 4-9 parts of the remaining water are added and stirred at 60-80 r / min for 2-4 min to obtain cement slurry. This step uses triethanolamine to regulate the early hydration of cement, improve the interface bonding between nanoparticles and cement matrix, prevent the agglomeration of functional fillers, and work with the superplasticizer to refine the pore structure. The delayed injection method after dry mixing is adopted to ensure that triethanolamine is uniformly introduced in the early stage of hydration, thereby ensuring the uniform dispersion and long-term stability of the optical functional phase. (4) Pour the above cement slurry into the mold, vibrate to form, cover with film and let stand, cure for 1~3 hours and dry, take out and cool naturally to room temperature to obtain day radiation cooled silicate cement.

[0024] Preferably, the first particle size is 1~5μm, the second particle size is 8~15μm, and the third particle size is 20~30μm.

[0025] Preferably, the particle size of the nano-titanium dioxide is 20~50nm.

[0026] Preferably, the mass ratio of the particle-graded fused silica powder to the modified nano-titanium dioxide is 1:(1.2~1.8).

[0027] Preferably, the drying process involves heating the temperature to 55-65°C at a rate of 5-10°C / h to avoid excessive evaporation of moisture causing an imbalance of internal and external stresses. After reaching the target temperature, the temperature is maintained for 3-5 hours to complete dehydration and hardening. This dynamic temperature control curve conforms to the development process of moisture migration rate and skeleton strength, and can effectively inhibit surface cracking and the formation of internal interconnecting pores.

[0028] Example 1; (1) Mix the first particle size fused silica powder, the second particle size fused silica powder and the third particle size fused silica powder in a mass percentage of 30%:60%:10% to obtain fused silica powder with particle size distribution; (2) Disperse nano-titanium dioxide in ethanol, add 1% by mass of nano-titanium dioxide silane coupling agent KH-550, stir at 25℃ for 1h, filter and dry to obtain modified nano-titanium dioxide. (3) By weight, 100 parts of ordinary gray silicate cement and 5 parts of particle size distribution fused silica powder are placed in a mixer and dry-mixed at 50 r / min for 0.5 min. Then, 7.5 parts of modified nano titanium dioxide are added and dry-mixed for another 1 min. 0.3 parts of triethanolamine and 0.1 parts of polycarboxylate superplasticizer are dissolved in 25 parts of water and injected into the mixer at 30 seconds after dry mixing is completed. The injection time is controlled within 10 seconds. Then, the remaining 9 parts of water are added and stirred at 60 r / min for 2 min to obtain cement slurry. (4) Pour the above cement slurry into the mold, vibrate to form, cover with film and let stand, standard curing for 1 hour, transfer to the drying oven, heat to 55°C at a rate of 5°C / h, keep warm for 3 hours, take out and cool naturally to room temperature to obtain daytime radiation-cooled silicate cement.

[0029] Example 2; (1) The first particle size fused silica powder, the second particle size fused silica powder and the third particle size fused silica powder are mixed in a mass percentage of 23%:64%:13% to obtain fused silica powder with particle size distribution; (2) Disperse nano-titanium dioxide in ethanol, add 3% by mass of nano-titanium dioxide silane coupling agent KH-550, stir at 25℃ for 1.5h, filter and dry to obtain modified nano-titanium dioxide; (3) By weight, 100 parts of ordinary gray silicate cement and 5 parts of particle size distribution fused silica powder are placed in a mixer and dry-mixed at 70 r / min for 1 min. Then, 7.5 parts of modified nano titanium dioxide are added and dry-mixed for another 1.5 min. 0.5 parts of triethanolamine and 0.2 parts of polycarboxylate superplasticizer are dissolved in 27 parts of water and injected into the mixer at 40 seconds after dry mixing is completed. The injection time is controlled within 15 seconds. Then, the remaining 7 parts of water are added and stirred at 70 r / min for 3 min to obtain cement slurry. (4) Pour the above cement slurry into the mold, vibrate to form, cover with film and let stand, standard curing for 2 hours, transfer to the drying oven, heat to 60°C at a rate of 8°C / h, keep warm for 4 hours, take out and cool naturally to room temperature to obtain day radiation cooled silicate cement.

[0030] Example 3; (1) Mix the first particle size fused silica powder, the second particle size fused silica powder and the third particle size fused silica powder in a mass percentage of 20%:70%:10% to obtain fused silica powder with particle size distribution; (2) Disperse nano-titanium dioxide in ethanol, add 5% by mass of nano-titanium dioxide silane coupling agent KH-550, stir at 30℃ for 2h, filter and dry to obtain modified nano-titanium dioxide. (3) By weight, 100 parts of ordinary gray silicate cement and 5 parts of particle size distribution fused silica powder are placed in a mixer and dry-mixed at 100 r / min for 1.5 min. Then, 7.5 parts of modified nano titanium dioxide are added and dry-mixed for another 2 min. 0.8 parts of triethanolamine and 0.3 parts of polycarboxylate superplasticizer are dissolved in 30 parts of water and injected into the mixer within 60 seconds after dry mixing is completed. The injection time is controlled within 20 seconds. Then, the remaining 4 parts of water are added and stirred at 80 r / min for 4 min to obtain cement slurry. (4) Pour the above cement slurry into the mold, vibrate to form, cover with film and let stand, standard curing for 3 hours, transfer to the drying oven, heat to 65°C at a rate of 10°C / h, keep warm for 5 hours, take out and cool naturally to room temperature to obtain daytime radiation-cooled silicate cement.

[0031] Example 4; (1) Mix the first particle size fused silica powder, the second particle size fused silica powder and the third particle size fused silica powder in a mass percentage ratio of 20%:60%:20% to obtain fused silica powder with particle size distribution; (2) Disperse nano-titanium dioxide in ethanol, add 3% by mass of nano-titanium dioxide silane coupling agent KH-550, stir at 25℃ for 1.5h, filter and dry to obtain modified nano-titanium dioxide; (3) By weight, 100 parts of ordinary gray silicate cement and 3 parts of particle size distribution fused silica powder are placed in a mixer and dry-mixed at 70 r / min for 1 min. Then, 5.4 parts of modified nano titanium dioxide are added and dry-mixed for another 1.5 min. 0.5 parts of triethanolamine and 0.2 parts of polycarboxylate superplasticizer are dissolved in 27 parts of water and injected into the mixer at 40 seconds after dry mixing is completed. The injection time is controlled within 15 seconds. Then, the remaining 7 parts of water are added and stirred at 70 r / min for 3 min to obtain cement slurry. (4) Pour the above cement slurry into the mold, vibrate to form, cover with film and let stand, standard curing for 2 hours, transfer to the drying oven, heat to 60°C at a rate of 8°C / h, keep warm for 4 hours, take out and cool naturally to room temperature to obtain day radiation cooled silicate cement.

[0032] Example 5; (1) The first particle size fused silica powder, the second particle size fused silica powder and the third particle size fused silica powder are mixed in a mass percentage of 26%:62%:12% to obtain fused silica powder with particle size distribution; (2) Disperse nano-titanium dioxide in ethanol, add 3% by mass of nano-titanium dioxide silane coupling agent KH-550, stir at 25℃ for 1.5h, filter and dry to obtain modified nano-titanium dioxide; (3) By weight, 100 parts of ordinary gray silicate cement and 10 parts of particle size distribution fused silica powder are placed in a mixer and dry-mixed at 70 r / min for 1 min. Then, 12 parts of modified nano titanium dioxide are added and dry-mixed for another 1.5 min. 0.5 parts of triethanolamine and 0.2 parts of polycarboxylate superplasticizer are dissolved in 27 parts of water and injected into the mixer at 40 seconds after dry mixing is completed. The injection time is controlled within 15 seconds. Then, the remaining 7 parts of water are added and stirred at 70 r / min for 3 min to obtain cement slurry. (4) Pour the above cement slurry into the mold, vibrate to form, cover with film and let stand, standard curing for 2 hours, transfer to the drying oven, heat to 60°C at a rate of 8°C / h, keep warm for 4 hours, take out and cool naturally to room temperature to obtain day radiation cooled silicate cement.

[0033] Comparative Example 1; The difference between Comparative Example 1 and Example 2 is that step (1) is omitted, and step (3) is changed to: by mass, 100 parts of ordinary gray silicate cement and 5 parts of fused silica powder are placed in a mixer and dry-mixed at 70 r / min for 1 min, and then 7.5 parts of modified nano titanium dioxide are added and dry-mixed for another 1.5 min; 0.5 parts of triethanolamine and 0.2 parts of polycarboxylate superplasticizer are dissolved in 27 parts of water, and injected into the mixer at 40 seconds after dry mixing is completed, with the injection time controlled within 15 seconds, and then the remaining 7 parts of water are added and stirred at 70 r / min for 3 min to obtain cement slurry; the remaining steps are the same as in Example 2.

[0034] Comparative Example 2; The difference between Comparative Example 2 and Example 2 is that step (1) is omitted, and step (3) is changed to: by mass, 100 parts of ordinary gray silicate cement and 7.5 parts of modified nano titanium dioxide are dry-mixed for 1.5 min; 0.5 parts of triethanolamine and 0.2 parts of polycarboxylate superplasticizer are dissolved in 27 parts of water, and injected into the mixer at 40 seconds after dry mixing is completed, with the injection time controlled within 15 seconds, and then the remaining 7 parts of water are added, and stirred at 70 r / min for 3 min to obtain cement slurry; the remaining steps are the same as in Example 2.

[0035] Comparative Example 3; The difference between Comparative Example 3 and Example 2 is that step (2) is omitted, and step (3) is changed to: by mass, 100 parts of ordinary gray silicate cement and 5 parts of particle-graded fused silica powder are placed in a mixer and dry-mixed at 70 r / min for 1 min, and then 7.5 parts of nano titanium dioxide are added and dry-mixed for another 1.5 min; 0.5 parts of triethanolamine and 0.2 parts of polycarboxylate superplasticizer are dissolved in 27 parts of water, and injected into the mixer at 40 seconds after dry mixing is completed, with the injection time controlled within 15 seconds, and then the remaining 7 parts of water are added, and stirred at 70 r / min for 3 min to obtain cement slurry; the remaining steps are the same as in Example 2.

[0036] Comparative Example 4; The difference between Comparative Example 4 and Example 2 is the difference in step (3). Step (3) is changed to: by mass, 100 parts of ordinary gray silicate cement and 5 parts of particle-graded fused silica powder are placed in a mixer and dry-mixed at 70 r / min for 1 min, and then 7.5 parts of modified nano titanium dioxide are added and dry-mixed for another 1.5 min; 0.2 parts of polycarboxylate superplasticizer are dissolved in 27 parts of water and injected into the mixer at 40 seconds after dry mixing is completed, with the injection time controlled within 15 seconds, and then the remaining 7 parts of water are added and stirred at 70 r / min for 3 min to obtain cement slurry.

[0037] Test and Results Analysis The cement slurry prepared in Examples 1-5 and Comparative Examples 1-4 were cast and molded using the same process (sample size 40mm×40mm×160mm). After standard curing for 28 days at 20±2℃ and relative humidity ≥95%, performance tests were conducted. The results are shown in Table 1.

[0038] Solar reflectance (0.3-2.5 μm) was measured using a UV-Vis-NIR spectrophotometer (Lambda1050+), thermal emissivity (8-13 μm) was measured using a Fourier transform infrared spectrometer (NICOLETIS20), and compressive strength was tested using a universal testing machine (UTM5105X) according to the JGJ / T70-2009 method. Three specimens were tested in each group, and the average value was taken. The results are shown in Table 1.

[0039] The ultraviolet aging test chamber (irradiation intensity 0.68W / m²) was used. 2 Accelerated aging tests were conducted at 340nm, blackboard temperature 60±2℃, with a cycle of 8h UV irradiation followed by 4h condensation. After aging for 500h, solar reflectance and thermal emissivity (8-13μm) were tested again. The results are shown in Table 1.

[0040] Surface cooling performance test: The cured specimens of Example 2 and the comparative specimens of ordinary gray silicate cement were placed in a constant temperature environment of 25℃, using a simulated solar radiation source (irradiance 1kW / m²). 2 The surface of the specimen was continuously irradiated for 30 minutes. During the irradiation, the surface temperature of the specimen was monitored synchronously using an infrared thermal imager and a thermocouple temperature sensor. The average surface temperature and the highest temperature point of the specimen were recorded. Each test was repeated 3 times, and the average value was taken as the test result.

[0041] Table 1

[0042] As shown in Table 1, the initial solar reflectance of Examples 1-5 all reached over 81.5%, and the thermal emissivity all reached over 82.7%. Among them, Example 2 showed the best solar reflectance and thermal emissivity, indicating that the synergistic doping of particle-graded fused silica powder and modified nano-titanium dioxide in this invention can effectively improve the optical properties of gray silicate cement, enabling it to meet the requirements of daytime radiative cooling. After 500 hours of accelerated aging, the solar reflectance of Examples 1-5 decreased by 4.25-4.93%, and the emissivity decreased by 4.52-4.96%, demonstrating good long-term stability.

[0043] Comparative Example 1, which used fused silica powder without particle size distribution but instead used a single particle size, had lower initial solar reflectance and thermal emissivity than Example 2, and its compressive strength also decreased. This indicates that optimizing the particle size distribution of fused silica powder helps to further improve optical and mechanical properties.

[0044] Comparative Example 2, which did not contain fused silica powder, had significantly lower initial reflectivity and thermal emissivity than Example 2, with the decrease in thermal emissivity being particularly pronounced, demonstrating that fused silica powder is a key component for ensuring high thermal emissivity.

[0045] Comparative Example 3 did not modify the nano-titanium dioxide with a silane coupling agent, indicating that modification of titanium dioxide with a silane coupling agent helps to suppress particle aggregation, enhance light scattering effect, and improve solar reflectivity.

[0046] Comparative Example 4, which did not contain triethanolamine, had lower reflectivity and emissivity than Example 2, and its compressive strength was also significantly reduced. This indicates that triethanolamine not only improves optical performance through dispersion, but also regulates the hydration process and improves the mechanical strength of the hardened body.

[0047] Figure 1 The figures show the reflectance and emissivity changes of the samples from Example 2 of this invention at different aging times. Figure 1 As shown, the solar reflectance and emissivity of the sample of this invention show a continuous decreasing trend with the extension of aging time. In the early stage of aging (0-100h), the rate of decrease in reflectance and emissivity is relatively fast. With the further increase of aging time, the rate of decrease of the two performance indicators slows down. Finally, at 500h, the reflectance drops to about 80.5% and the emissivity drops to about 81.6%, indicating that the optical performance of the sample of this invention decays synchronously during the aging process, and still maintains a high level of reflectance and emissivity after 500h aging, demonstrating good aging resistance.

[0048] Figure 2 This is a comparison chart of the average and maximum surface temperatures of the silicate cement of this invention and ordinary gray cement. (See attached image.) Figure 2 As shown, under the same test conditions, the average surface temperature of the sample of the present invention was 42.3℃, and the highest temperature point was 44.1℃; the average surface temperature of ordinary gray cement was 48.7℃, and the highest temperature point was 51.2℃. Compared with ordinary gray cement, the average surface temperature of the sample of the present invention was reduced by 6.4℃, and the highest temperature was reduced by 7.1℃, indicating that the daytime radiation-cooled silicate cement of the present invention has a significant cooling effect and can effectively reduce the surface temperature, verifying its excellent radiation cooling performance.

[0049] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No markings in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for preparing daytime radiation-cooled silicate cement, characterized in that, Includes the following steps: (1) Mix the first-size fused silica powder, the second-size fused silica powder and the third-size fused silica powder in proportion to obtain fused silica powder with particle size distribution; (2) The nano-titanium dioxide was surface modified with a silane coupling agent to obtain modified nano-titanium dioxide; (3) First, dry mix the ordinary silicate cement and the particle size distribution of the fused silica powder prepared in step (1) for the first time. Then, add the modified nano titanium dioxide prepared in step (2) for the second dry mix. After the dry mix is ​​completed, add an aqueous solution containing triethanolamine and water-reducing agent within 30 to 60 seconds. Continue to add water for wet mixing and stir to obtain cement slurry. (4) Pour the above cement slurry into the mold, vibrate to form, cover with film and let stand, cure according to standard and dry, take out and cool naturally to room temperature to obtain day radiation cooled silicate cement.

2. The method according to claim 1, characterized in that, In step (1), the first particle size is 1~5μm, the second particle size is 8~15μm, and the third particle size is 20~30μm.

3. The method according to claim 1, characterized in that, In step (1), the mass percentages of the first-size fused silica powder, the second-size fused silica powder, and the third-size fused silica powder are 20-30%: 60-70%: 10-20%.

4. The method according to claim 1, characterized in that, The mass ratio of nano-titanium dioxide and silane coupling agent in step (2) is 1:(1~5%); the particle size of nano-titanium dioxide is 20~50nm.

5. The method according to claim 1, characterized in that, The cement slurry mentioned in step (3) includes, by weight, 100 parts of ordinary Portland cement, 3 to 10 parts of particle size distribution fused silica powder, 5.4 to 12 parts of modified nano titanium dioxide, 0.3 to 0.8 parts of triethanolamine, 0.1 to 0.3 parts of water-reducing agent, and a total of 29 to 39 parts of mixing water.

6. The method according to claim 1, characterized in that, The mass ratio of the particle-graded fused silica powder and the modified nano-titanium dioxide in step (3) is 1:(1.2~1.8).

7. The method according to claim 1, characterized in that, In step (3), the rotation speed of the first dry mixing is 50~100 r / min and the time is 0.5~1.5 min; the time of the second dry mixing is 1~2 min.

8. The method according to claim 1, characterized in that, The injection time of the aqueous solution containing triethanolamine and water-reducing agent in step (3) is 10-20 seconds.

9. The method according to claim 1, characterized in that, The wet mixing speed in step (3) is 60~80 r / min, and the time is 2~4 min.

10. The method according to claim 1, characterized in that, The heating rate for drying in step (4) is 5~10℃ / h, the temperature is 55~65℃, and the holding time is 3~5h.

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