Lightweight high-strength self-cleaning white ultra-high performance concrete and preparation method thereof

Abstract

The invention belongs to the technical field of concrete, and discloses light high-strength self-cleaning white ultra-high performance concrete and a preparation method thereof. The light high-strength self-cleaning white ultra-high performance concrete is prepared from the following raw materials in parts by mass: 35 to 45 parts of white cement, 10 to 15 parts of acetylated modified nano cellulose, 45 to 50 parts of TiO2-loaded white porous ceramic, 0.3 to 0.5 part of cardanol glycidyl ether, 1.0 to 1.5 parts of a polycarboxylic acid water reducing agent, 0.03 to 0.06 part of a de-foaming agent and 12 to 20 parts of water. The light-weight high-strength self-cleaning white ultra-high performance concrete has the characteristics of excellent performance, low energy consumption, high whiteness, high strength, light weight, high stain resistance and the like, and is simple and convenient in process, low in cost and wide in application market prospect.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of concrete, and particularly relates to a light-weight high-strength self-cleaning white ultra-high performance concrete and a preparation method thereof. BACKGROUND

[0002] In the practical application and technical research of white ultra-high performance concrete (UHPC), there are often contradictions between performance optimization, environmental protection requirements and cost control, especially in balancing energy consumption, whiteness, strength and stain resistance. To achieve a white appearance, traditional white UHPC has a high dependence on high-cost mineral raw materials, and white cement, white quartz sand, dolomite and titanium dioxide become core components. However, the production and processing of these raw materials are accompanied by serious high energy consumption problems. In order to ensure the strength, the traditional formula often uses a high amount of cementitious materials, which causes large shrinkage and insufficient toughness, greatly increases the risk of cracking, and requires the addition of a large amount of steel fibers or synthetic fibers to improve toughness, further increasing the material cost and construction complexity. In terms of stain resistance, existing technologies often rely on organic silicon hydrophobic agents or stearic acid modification, which can easily fail over a long period of time, and cannot degrade organic pollutants, affecting the durability of the white appearance and limiting its application in exposed environments such as building facades and landscape decorations.

[0003] In addition, with the promotion of building industrialization and green building concepts, lightweight has become a core requirement for white UHPC to expand its application scenarios. However, traditional white UHPC relies on high-density aggregates such as quartz sand and dolomite, and its overall bulk density is generally high, which cannot meet the lightweight requirement. If the amount of high-density aggregate is reduced and lightweight admixtures are added to reduce the density, new problems often arise. On the one hand, the whiteness of lightweight admixtures is much lower than that of quartz sand and dolomite, which can significantly reduce the whiteness of the concrete and fail to meet the requirements of high-end decoration scenarios for white appearance. On the other hand, the interfacial adhesion between lightweight admixtures and cementitious materials is poor, which affects the strength and toughness of the concrete, and also increases the water absorption of the material, further deteriorating the stain resistance. The dilemma of lightweight, whiteness, strength and stain resistance also restricts the industrial expansion space of white UHPC.

[0004] Therefore, it is particularly important to develop a low-energy, lightweight, high-strength, high-whiteness and self-cleaning white UHPC for building decoration and high-end building materials. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a light-weight high-strength self-cleaning white ultra-high performance concrete and a preparation method thereof, which has excellent performance, low energy consumption, high whiteness, high strength, lightweight, high stain resistance and other characteristics, and is simple in process, low in cost and wide in application market prospect.

[0006] To solve the technical problems proposed in the present application, the present application provides a lightweight high-strength self-cleaning white ultra-high performance concrete, comprising the following mass fractions of raw materials: white cement 35-45 parts, acetylated modified nanocellulose 10-15 parts, white porous ceramic loaded with TiO2 45-50 parts, cardanol glycidyl ether 0.3-0.5 parts, polycarboxylate superplasticizer 1.0-1.5 parts, defoaming agent 0.03-0.06 parts, and water 12-20 parts.

[0007] In the above scheme, the whiteness of the white cement is ≥85%, the strength grade is ≥42.5 grade, and the average particle size is 12-20 μm.

[0008] In the above scheme, the preparation method of the acetylated modified nanocellulose is as follows: nanocellulose is immersed in a mixed solution of acetic anhydride and pyridine, heated and reacted, then washed and dried to obtain acetylated modified nanocellulose.

[0009] Further, the nanocellulose is cellulose nanofiber, the whiteness is ≥90%, the diameter is 10-50 nm, and the length is 1-5 μm.

[0010] Further, the mixed solution of acetic anhydride and pyridine is mixed by acetic anhydride and pyridine in a volume ratio of 1:2.5-1:3.5.

[0011] Further, the mass of the nanocellulose and the volume of the mixed solution of acetic anhydride and pyridine are in a ratio of 1 g:10-20 mL.

[0012] Further, the heating temperature of the heating reaction is 60-70 °C, and the reaction time is 2-3 h.

[0013] Further, the washing is first washed with a 5-8% mass fraction of sodium carbonate aqueous solution, and then repeatedly washed with water until the pH is 6.5-7.0. Further, the sodium carbonate aqueous solution washing is performed by magnetic stirring at a rate of 300-500 r / min for 25-35 min. The sodium carbonate aqueous solution washing can dissolve the unreacted pyridine in the system, and at the same time remove the unreacted acetic anhydride hydrolysis generated in the system, such as acetic acid and other acidic residues, to avoid the abnormal pH of the modified nanocellulose, and further affect the interfacial compatibility with the white cement.

[0014] Further, the drying temperature is 60-80 °C, and the drying time is 4-8 h.

[0015] In the above scheme, the preparation method of the white porous ceramic loaded with TiO2 is as follows: white porous ceramic is immersed in a titanium tetrabutoxide ethanol solution, taken out and hydrolyzed by heating, then dried and calcined to obtain white porous ceramic loaded with TiO2.

[0016] Further, the white porous ceramic has a whiteness of ≥ 88%, a particle size of ≤ 0.075 mm, a density of 1.8-2.0 g / cm 3 , a specific surface area of 800-1000 m 2 / kg, a porosity of 40%-60%, and an average pore size of 50-200 nm.

[0017] Further, the white porous ceramic is preferably waste white porous ceramic.

[0018] Further, the white porous ceramic is sequentially cleaned with water and anhydrous ethanol by ultrasonic cleaning, and then dried to remove surface impurities, with a total ultrasonic cleaning time of 10-20 min.

[0019] Further, the titanium tetrabutoxide ethanol solution is prepared by mixing titanium tetrabutoxide and anhydrous ethanol at a volume ratio of 1:8-1:12, and the mixture is stirred for 20-40 min until a uniform transparent solution is formed.

[0020] Further, the mass of the white porous ceramic and the volume of the titanium tetrabutoxide ethanol solution are in a ratio of 1 g:10-20 mL.

[0021] Further, the white porous ceramic is immersed in the titanium tetrabutoxide ethanol solution for 20-40 min to ensure that the solution fully penetrates the pores.

[0022] Further, the heating temperature for the hydrolysis is 70-90°C, and the hydrolysis time is 1.5-2.5 h, so that the titanium tetrabutoxide is hydrolyzed to form amorphous TiO2, and the hydrolysis is considered complete when there are no oily droplets on the surface of the white porous ceramic.

[0023] Further, the drying temperature is 70-90°C, and the drying time is 10-14 h, to remove residual solvents and organic matter.

[0024] Further, the calcination temperature is 450-550°C, and the holding time is 1.5-2.5 h, so that the amorphous TiO2 is converted into anatase TiO2.

[0025] Further, the heating rate for the calcination is 3-7°C / min.

[0026] Further, the TiO2 loaded on the surface of the white porous ceramic is anatase nano-TiO2 with a particle size of 10-50 nm, a density of 4.0-4.3 g / cm 3 , and a Mohs hardness of 6-7.

[0027] In the above scheme, the cardanol glycidyl ether has a viscosity of 30-50 mPa•s and an epoxy value of 0.20-0.28 eq / 100 g.

[0028] In the scheme, the water-reducing rate of the polycarboxylic acid water-reducing agent is 35-45%.

[0029] In the scheme, the defoaming agent is a polyether defoaming agent.

[0030] The application also provides a preparation method of the lightweight high-strength self-cleaning white ultra-high performance concrete. 1) After uniformly stirring the white cement and the acetylated modified nanocellulose, a part of water and a water-reducing agent are added and stirred; 2) After sequentially adding the white porous ceramic loaded with TiO2, the remaining water and the water-reducing agent, a bio-based hydrophobic agent and a defoaming agent are added and uniformly stirred to obtain the ultra-high performance concrete.

[0031] In step 1), the stirring rate is 60-90 r / min, the white cement and the nanocellulose are mixed and stirred for 4-6 min, and after the water and the water-reducing agent are added, the stirring is performed for 1-2 min.

[0032] In step 1), the amount of the water and the water-reducing agent added is 45-55% of the total amount.

[0033] In step 2), the stirring rate is 90-120 r / min, and the stirring time is 4-5 min.

[0034] In the scheme, when the ultra-high performance concrete is cured, first, ultraviolet light with a wavelength of 350-380 nm and an irradiance of 8-12 W / m 2 is used for irradiation for 1.5-2.5 h to induce TiO2 to catalyze early hydration, and then standard curing (temperature 20±2℃, relative humidity ≥95%) is performed until a predetermined age is reached.

[0035] In the scheme, the density of the ultra-high performance concrete is 1.9-2.3 g / cm 3 , the whiteness is ≥87%, the water absorption is ≤1.0%, the 28d compressive strength is ≥128 MPa, the 28d dry shrinkage is ≤0.06%, the 28d surface organic matter content is ≤0.1 g / cm 2 , and the CO2 emission is ≤200 kg / m 3 .

[0036] Compared with the prior art, the application has the following beneficial effects: (1) This invention utilizes the high strength, low density and natural white properties of nanocellulose to partially replace white cement and reduce the amount of cementitious materials. The nanocellulose is acetylated and modified. After modification, the interfacial bonding strength between nanocellulose and white cement and porous ceramics is significantly improved, which solves the negative impact on concrete performance caused by insufficient interfacial bonding between nanocellulose and cementitious materials. At the same time, the problem of nanocellulose being prone to agglomeration is also solved. Finally, it forms a synergistic effect of "strengthening and toughening + whiteness retention + lightweighting" with other raw materials, which significantly improves the compressive strength and flexural strength of UHPC and greatly reduces drying shrinkage.

[0037] (2) The present invention uses lightweight aggregate white porous ceramic, which can preferentially select waste white porous ceramic to reduce energy consumption. Nano TiO2 is loaded on its surface, realizing the integration of "lightweight aggregate + long-term photocatalysis self-cleaning"; the porosity (40%~60%) and pore size (50~200nm) of the white porous ceramic used are precisely matched with TiO2 nanoparticles (10~30nm), and the specific surface area (800~1000m² / kg) is 2~3 times that of zeolite. The TiO2 loading is significantly improved to promote photocatalytic efficiency; through in-situ loading, the hydrolysis temperature and calcination temperature are optimized, so that TiO2 and ceramic support form chemical bonds, solving the problem of easy detachment of TiO2 loaded on zeolite, thereby improving photocatalytic stability.

[0038] (3) This invention uses cashew phenol glycidyl ether as a bio-based hydrophobic agent to replace traditional organosilicon hydrophobic agents or stearic acid modification technology. Through the bonding of epoxy groups with cement hydration products, a long-lasting hydrophobic layer is formed and intertwined with the three-dimensional network of nanocellulose. The weather resistance of the formed hydrophobic layer is significantly improved, solving the problem of easy failure of traditional organosilicon hydrophobic agents. In synergy with TiO2 photocatalysis, the hydrophobic layer reduces the adhesion of pollutants, and TiO2 degrades residual organic matter, realizing "superhydrophobic + photocatalysis" dual self-cleaning, further improving the stain resistance performance.

[0039] (4) The curing process of concrete in this invention is more low-carbon and environmentally friendly. By using ultraviolet light curing, the curing time is shortened, and energy consumption is further reduced compared with traditional steam curing. Detailed Implementation

[0040] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0041] In the following examples, the raw materials used include: 42.5 grade white cement, with a whiteness ≥85% and an average particle size of 12~20μm; cellulose nanofibers, with a whiteness ≥90%, a diameter of 10~50nm, and a length of 1~5μm; and waste white porous ceramics, with a whiteness ≥88%, a particle size ≤0.075mm, and a density of 1.8~2.0g / cm³. 3Specific surface area 800-1000 m 2 / kg, porosity 40-60%, average pore size 50-200 nm, and the surface of the white porous ceramic is loaded with TiO2 in the form of anatase nano-TiO2 with a particle size of 20 nm and a density of 4.1 g / cm3and a Mohs hardness of 6.5.

[0042] Example 1 The lightweight high-strength self-cleaning white ultra-high performance concrete of this example comprises the following mass fractions of raw materials: white cement 35 parts, acetylated modified nanocellulose 15 parts, white porous ceramic loaded with TiO2 50 parts, cardanol glycidyl ether 0.5 part, polycarboxylic acid water reducer 1.0 part, defoaming agent 0.03 part, and water 12 parts. Among them: The preparation method of the acetylated modified nanocellulose is as follows: nanocellulose is immersed in a mixed solution of acetic anhydride and pyridine at a volume ratio of 1:2.5, the mass of the nanocellulose and the volume of the mixed solution are in a ratio of 1 g:10 mL, heated to 60°C for 2 h, then washed with a 5% by mass sodium carbonate aqueous solution at a stirring speed of 300 r / min for 25 min, then repeatedly washed with deionized water until the pH is 6.5, and finally dried at 60°C for 4 h to obtain the acetylated modified nanocellulose.

[0043] The preparation method of the white porous ceramic loaded with TiO2 is as follows: the white porous ceramic is immersed in a mixed solution of tetrabutyl titanate and anhydrous ethanol at a volume ratio of 1:10, the mass of the white porous ceramic and the volume of the mixed solution are in a ratio of 1 g:10 mL, immersed for 30 min, then taken out, hydrolyzed at 80°C for 2 h until there are no oily droplets on the surface of the white porous ceramic, then dried at 80°C for 12 h, and finally heated at a rate of 5°C / min to 500°C and calcined for 2 h to obtain the white porous ceramic loaded with TiO2. The TiO2 loaded on the surface of the white porous ceramic is anatase nano-TiO2 with a particle size of 20 nm and a density of 4.1 g / cm3and a Mohs hardness of 6.5. 3

[0044] The preparation method of the lightweight high-strength self-cleaning white ultra-high performance concrete of this example comprises the following steps: 1) The white cement and the acetylated modified nanocellulose are stirred at a speed of 70 r / min for 5 min, then 50% water and 50% water reducer are added, and the stirring is continued at a speed of 70 r / min for 1.5 min; ​2) Continue to add the white porous ceramic loaded with TiO2, the remaining water and the water reducing agent, then add the bio-based water repellent and the defoaming agent, stir at a speed of 100 r / min for 4.5 min, and obtain the ultra-high performance concrete.

[0045] The ultra-high performance concrete prepared in this example is first irradiated with ultraviolet light with a wavelength of 365 nm and an irradiance of 10 W / m 2 for 2 h, and then is standardly cured under the condition of a temperature of 20±2 ℃ and a relative humidity of ≥95% to a predetermined age.

[0046] Example 2 The lightweight high-strength self-cleaning white ultra-high performance concrete of this example comprises the following mass fractions of raw materials: white cement 38 parts, acetylated modified nanocellulose 13 parts, white porous ceramic loaded with TiO2 49 parts, cardanol glycidyl ether 0.5 parts, polycarboxylic acid water reducing agent 1.2 parts, defoaming agent 0.03 parts, and water 14 parts. Among them: The preparation method of the acetylated modified nanocellulose is as follows: nanocellulose is immersed in a mixed solution of acetic anhydride and pyridine at a volume ratio of 1:2.8, the mass of the nanocellulose and the volume of the mixed solution are in a ratio of 1 g:12 mL, heating to 63 ℃ for 2.2 h, first using a 8% mass fraction of sodium carbonate aqueous solution to stir magnetically at a speed of 500 r / min for 35 min, then repeatedly washing with deionized water until pH 7, and finally drying at 65 ℃ for 5 h to obtain acetylated modified nanocellulose.

[0047] The preparation method of the white porous ceramic loaded with TiO2 is as follows: the white porous ceramic is immersed in a mixed solution of tetrabutyl titanate and anhydrous ethanol at a volume ratio of 1:8, the mass of the white porous ceramic and the volume of the mixed solution are in a ratio of 1 g:12 mL, immersed for 25 min, then taken out, hydrolyzed at 75 ℃ for 1.5 h until there are no oily droplets on the surface of the white porous ceramic, then dried at 75 ℃ for 10 h, and finally heated at a rate of 4 ℃ / min to 480 ℃ and calcined for 1.5 h to obtain the white porous ceramic loaded with TiO2. The TiO2 loaded on the surface is anatase type nano-TiO2 with a particle size of 15 nm and a density of 4.0 g / cm 3 , a Mohs hardness of 6.2.

[0048] The preparation method of the lightweight high-strength self-cleaning white ultra-high performance concrete of this example comprises the following steps: 1) Stir the white cement and the acetylated modified nanocellulose at a speed of 65 r / min for 4 min, then add 45% of the water and 45% of the water reducing agent, and continue to stir at a speed of 65 r / min for 1.2 min; 2) Continue to add the white porous ceramic loaded with TiO2, the remaining water and the water reducing agent, then add the bio-based water repellent and the defoaming agent, stir at a speed of 95 r / min for 4 min, and obtain the ultra-high performance concrete.

[0049] The ultra-high performance concrete prepared in this example is first irradiated with ultraviolet light with a wavelength of 350 nm and an irradiance of 8 W / m 2 for 1.5 h, and then is standardly cured under the condition of a temperature of 20±2℃ and a relative humidity of ≥95% to a predetermined age.

[0050] Example 3 The lightweight high-strength self-cleaning white ultra-high performance concrete of this example comprises the following mass fractions of raw materials: white cement 40 parts, acetylated modified nanocellulose 12 parts, white porous ceramic loaded with TiO2 48 parts, cardanol glycidyl ether 0.4 parts, polycarboxylic acid water reducing agent 1.3 parts, defoaming agent 0.05 parts, and water 16 parts. Among them: The preparation method of the acetylated modified nanocellulose is as follows: nanocellulose is immersed in a mixed solution of acetic anhydride and pyridine at a volume ratio of 1:3, the mass of the nanocellulose and the volume of the mixed solution are in a ratio of 1g:15mL, heating to 65℃ for 2.6h, first using a 7% mass fraction of sodium carbonate aqueous solution to stir at a speed of 400 r / min for 30 min, then repeatedly washing with deionized water until pH 6.8, and finally drying at 70℃ for 6h to obtain acetylated modified nanocellulose.

[0051] The preparation method of the white porous ceramic loaded with TiO2 is as follows: the white porous ceramic is immersed in a mixed solution of tetrabutyl titanate and anhydrous ethanol at a volume ratio of 1:12, the mass of the white porous ceramic and the volume of the mixed solution are in a ratio of 1g:15mL, immersed for 35 min, then taken out, hydrolyzed at 85℃ for 2.5h until there are no oily droplets on the surface of the white porous ceramic, then dried at 85℃ for 14h, and finally heated at a rate of 6℃ / min to 520℃ and calcined for 2.5h to obtain the white porous ceramic loaded with TiO2. The TiO2 loaded on the surface is anatase type nano-TiO2 with a particle size of 25nm and a density of 4.3 g / cm 3 , a Mohs hardness of 6.8.

[0052] The preparation method of the lightweight high-strength self-cleaning white ultra-high performance concrete of this example comprises the following steps: 1) Stir the white cement and the acetylated modified nanocellulose at a speed of 85 r / min for 6 min, then add 55% water and 55% water reducing agent, and continue to stir at a speed of 85 r / min for 1.8 min; 2) Continue to add the white porous ceramic loaded with TiO2, the remaining water and the water reducing agent, then add the bio-based water repellent and the defoaming agent, stir at a speed of 115 r / min for 5 min, to obtain the ultra-high performance concrete.

[0053] The ultra-high performance concrete prepared in this example is first irradiated with ultraviolet light with a wavelength of 370 nm and an irradiance of 12 W / m 2 for 2.5 h, and then standard curing is performed under the conditions of a temperature of 20±2℃ and a relative humidity of ≥95% to the predetermined age.

[0054] Example 4 The lightweight high-strength self-cleaning white ultra-high performance concrete of this example comprises the following mass fractions of raw materials: white cement 43 parts, acetylated modified nanocellulose 11 parts, white porous ceramic loaded with TiO2 46 parts, cardanol glycidyl ether 0.4 parts, polycarboxylic acid water reducing agent 1.4 parts, defoaming agent 0.05 parts, and water 18 parts. Among them: The preparation method of the acetylated modified nanocellulose is as follows: nanocellulose is immersed in a mixed solution of acetic anhydride and pyridine at a volume ratio of 1:3.2, the mass of the nanocellulose and the volume of the mixed solution are in a ratio of 1g:18mL, heating to 68℃ for 2.8h, first using a 6% mass fraction of sodium carbonate aqueous solution to stir magnetically at a speed of 350 r / min for 28 min, then repeatedly washing with deionized water until the pH is 6.8, and finally drying at 75℃ for 7h to obtain acetylated modified nanocellulose.

[0055] The preparation method of the white porous ceramic loaded with TiO2 is as follows: the white porous ceramic is immersed in a mixed solution of tetrabutyl titanate and anhydrous ethanol at a volume ratio of 1:9, the mass of the white porous ceramic and the volume of the mixed solution are in a ratio of 1g:11mL, immersed for 28 min, then removed, hydrolyzed at 70℃ for 1.8h until there are no oily droplets on the surface of the white porous ceramic, then dried at 78℃ for 11h, and finally heated at a rate of 4.5℃ / min to 470℃ and calcined for 1.8h to obtain the white porous ceramic loaded with TiO2. The TiO2 loaded on the surface is anatase type nano-TiO2 with a particle size of 12 nm and a density of 4.15 g / cm 3 , a Mohs hardness of 6.0.

[0056] The preparation method of the lightweight high-strength self-cleaning white ultra-high performance concrete of this example comprises the following steps: 1) The white cement and the acetylated modified nanocellulose are stirred at a speed of 60 r / min for 4.5 min, then 48% water and 48% water reducing agent are added, and stirring is continued at a speed of 60 r / min for 1 min; 2) Continue to add TiO2-loaded white porous ceramic, the remaining water and water-reducing agent in sequence, then add bio-based water-repellent agent and defoamer, and stir at a rate of 90 r / min for 4.2 min to obtain ultra-high performance concrete.

[0057] The ultra-high performance concrete prepared in this embodiment was first subjected to an irradiance of 9W / m at a wavelength of 360nm. 2 Irradiate with ultraviolet light for 1.8 hours, and then cure under standard conditions at a temperature of 20±2℃ and relative humidity ≥95% until the predetermined age.

[0058] Example 5 The lightweight, high-strength, self-cleaning, white, ultra-high-performance concrete of this embodiment comprises the following raw materials in parts by weight: 45 parts white cement, 10 parts acetylated modified nanocellulose, 45 parts white porous ceramic loaded with TiO2, 0.3 parts cashew phenol glycidyl ether, 1.5 parts polycarboxylate superplasticizer, 0.06 parts defoamer, and 20 parts water. Wherein: The preparation method of acetylated modified nanocellulose is as follows: Nanocellulose is immersed in a mixed solution of acetic anhydride and pyridine at a volume ratio of 1:3.5, and the mass ratio of nanocellulose to the volume of the mixed solution is 1g:20mL. After heating to 70℃ and reacting for 3h, it is first washed with a 6% sodium carbonate aqueous solution at a speed of 450r / min with magnetic stirring for 32min, then repeatedly washed with deionized water until pH 6.9, and finally dried at 80℃ for 8h to obtain acetylated modified nanocellulose.

[0059] The preparation method of TiO2-loaded white porous ceramic is as follows: White porous ceramic is immersed in a mixed solution of tetrabutyl titanate and anhydrous ethanol at a volume ratio of 1:11 (1 g:13 mL). After immersion for 32 min, the ceramic is removed and heated to 90℃ for 2.2 h for hydrolysis until no oily droplets remain on the surface. It is then dried at 82℃ for 13 h, and finally calcined at 530℃ for 2.2 h at a rate of 5.5℃ / min to obtain TiO2-loaded white porous ceramic. Testing showed that the TiO2 loaded on its surface is anatase nano-TiO2 with a particle size of 28 nm and a density of 4.2 g / cm³. 3 Its Mohs hardness is 7.0.

[0060] The preparation method of lightweight, high-strength, self-cleaning, white, ultra-high-performance concrete in this embodiment includes the following steps: 1) After stirring the white cement and acetylated modified nanocellulose at a speed of 90 r / min for 5.5 min, add 52% water and 52% water-reducing agent, and continue stirring at a speed of 90 r / min for 2 min. 2) Continue to add TiO2-loaded white porous ceramic, the remaining water and water-reducing agent in sequence, then add bio-based water-repellent agent and defoamer, and stir at a rate of 120 r / min for 4.8 min to obtain ultra-high performance concrete.

[0061] The ultra-high performance concrete prepared in this embodiment was first subjected to an irradiance of 11 W / m at a wavelength of 380 nm. 2 Irradiate with ultraviolet light for 2.2 hours, and then cure under standard conditions at a temperature of 20±2℃ and relative humidity ≥95% until the predetermined age.

[0062] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the acetylated modified nanocellulose was replaced with an equal mass of white cement.

[0063] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the white porous ceramic supported on TiO2 was replaced with an equal mass of conventional quartz sand, which has a Mohs hardness of 7 and a bulk density of 1.7 g / cm³. 3 .

[0064] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that the acetylated modified nanocellulose was replaced with an equal mass of white cement, and the TiO2-loaded white porous ceramic was replaced with an equal mass of conventional quartz sand, the properties of which were the same as those in Comparative Example 2.

[0065] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that cashew phenol glycidyl ether was replaced with an equal mass of conventional organosilicon hydrophobic agent KH-550.

[0066] Comparative Example 5 The difference between Comparative Example 5 and Example 1 is that Comparative Example 5 uses a white porous ceramic with TiO2 supported by a non-in-situ loading method. The specific preparation method is as follows: Anatase nano-TiO2 (particle size 20 nm, density 4.1 g / cm³) 3 TiO2 was mixed with anhydrous ethanol at a mass ratio of 1:50 and ultrasonically dispersed in an ultrasonic cleaner for 30 min to obtain a uniform and stable TiO2 ethanol dispersion. The same white porous ceramic as in Example 1 was immersed in the above dispersion for 60 min, and stirred once every 15 min to promote the adhesion of TiO2 particles. After being taken out, it was placed in an 80℃ forced-air drying oven for 12 h to remove residual ethanol. Finally, it was placed in a muffle furnace and heated to 500℃ at a heating rate of 5℃ / min, held for 2 h, and naturally cooled to obtain a white porous ceramic with non-in-situ TiO2 loading.

[0067] Comparative Example 6 The difference between Comparative Example 6 and Example 1 is that the acetylated modified nanocellulose was replaced with an equal mass of unmodified nanocellulose.

[0068] The performance of the examples and comparative examples was tested. The compressive strength and density were tested according to GB / T 50081 "Test Method for Mechanical Properties of Ordinary Concrete", the drying shrinkage was tested according to GB / T 50082-2009 "Test Method for Long-term Performance and Durability of Ordinary Concrete", the whiteness was tested according to the R457 method in GB / T 2015-2017 "White Silicate Cement", the water absorption rate was tested according to the immersion method in GB / T11969-2020 "Test Method for Performance of Autoclaved Aerated Concrete", and the surface organic matter content was tested according to the extraction method in GB / T42898-2023 "Test for Emission of Semi-volatile Organic Compounds (SVOC) in Building Materials". The CO2 emission was calculated based on the carbon emissions of the raw materials used to prepare UHPC.

[0069] Table 1

[0070] Table 2

[0071] Comparative Example 1, without the addition of acetylated modified nanocellulose, showed decreased compressive strength, increased drying shrinkage, decreased whiteness, and increased density compared to the examples. This is because the three-dimensional network formed by acetylated modified nanocellulose can fill microcracks, reducing drying shrinkage. Simultaneously, its high whiteness reduces dependence on white cement, synergistically improving both strength and whiteness. Comparative Example 2, without the addition of TiO2-loaded white porous ceramic, showed increased surface organic matter content, increased density, and decreased whiteness compared to the examples. This is because TiO2-loaded white porous ceramic possesses both photocatalytic degradation of organic matter (self-cleaning) and lightweight properties, while quartz sand lacks this function and has a higher density. Comparative Example 3, without the addition of acetylated modified nanocellulose and TiO2-loaded white porous ceramic, showed comprehensive deterioration in all properties compared to the examples, confirming the synergistic effect of acetylated modified nanocellulose and TiO2-loaded white porous ceramic. Together, they achieve a comprehensive innovative performance of "high strength + lightweight + high whiteness + self-cleaning".

[0072] Comparative Example 4 used a traditional organosilicon hydrophobic agent. Compared to the example, the surface organic matter content increased, and the hydrophobic layer failed after 6 months of UV irradiation (the example still remained hydrophobic). This is because cashew phenol glycidyl ether can bond with cement hydration products to form a long-lasting hydrophobic layer and synergistically with TiO2 photocatalysis, solving the problem of easy failure of traditional hydrophobic agents. Furthermore, the strength and drying shrinkage were negatively affected after replacement because the epoxy groups of cashew phenol glycidyl ether can form chemical bonds with cement hydration products and intertwine with the three-dimensional network of acetylated modified nanocellulose, enhancing interfacial adhesion, filling microcracks, and improving overall mechanical properties. In contrast, traditional organosilicon hydrophobic agents only adhere to the surface through physical adsorption, failing to form stable chemical bonds and exhibiting poor compatibility with the nanocellulose network, resulting in weak interfacial adhesion, decreased internal density of the concrete structure, and ultimately reduced strength.

[0073] Comparative Example 5, using a non-in-situ loading method to prepare white porous ceramics with TiO2 loading, showed increased surface organic matter content and decreased photocatalytic stability. This is because in-situ loading allows TiO2 to form chemical bonds with the ceramic support, increasing the loading and binding force of TiO2, thereby improving photocatalytic stability. In-situ loading, through the hydrolysis and calcination of tetrabutyl titanate, allows TiO2 to form chemical bonds with the white porous ceramic, uniformly covering the ceramic surface and pores. This enhances the interfacial adhesion between the ceramic and the cementitious material, and also utilizes the high strength of TiO2 to improve the aggregate's own properties. In contrast, non-in-situ loading involves TiO2 particles physically dispersed and attached to the ceramic surface, relying solely on van der Waals forces for bonding. This results in easy detachment and uneven dispersion. On the one hand, the detached TiO2 cannot play a reinforcing role; on the other hand, the exposed pores on the ceramic surface are not effectively filled, leading to increased interfacial defects and thus a decrease in the overall strength of the concrete. TiO2 loaded in situ tends to agglomerate, forming local dark agglomeration areas and disrupting the uniformity of whiteness of the system. TiO2 loaded in situ has a low loading amount and is easy to fall off, so it cannot fully utilize the high whiteness of TiO2. Areas on the ceramic surface that are not uniformly covered may have uneven light scattering due to exposed pores, further reducing whiteness. Therefore, the whiteness is reduced.

[0074] Comparative Example 6, which directly used unmodified nanocellulose, showed a decrease in compressive strength and an increase in drying shrinkage compared to the Example. This is because unmodified nanocellulose has poor interfacial adhesion to cementitious materials and is prone to agglomeration, failing to form an effective three-dimensional network reinforcement structure. Acetylation modification, on the other hand, improved its dispersibility and interfacial adhesion. While nanocellulose itself has a whiteness ≥90%, unmodified nanocellulose is prone to agglomeration. The localized dense areas formed by these agglomerates alter the light reflection path (agglomerates scatter light differently than uniformly dispersed nanofibers), leading to an overall decrease in whiteness. Furthermore, the poor interfacial adhesion between unmodified nanocellulose and white cement or ceramics (lacking the bridging effect of acetylated groups) creates micropores at the interface. These pores absorb light more effectively than dense structures, further reducing whiteness. Agglomerated nanocellulose cannot fully utilize its high whiteness-filling and brightening effect, and the agglomerates may not mix evenly with other raw materials, resulting in uneven whiteness distribution and thus a decrease in the overall whiteness test value.

[0075] The above embodiments are merely examples for clear illustration and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations, and any obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A lightweight high-strength self-cleaning white ultra-high performance concrete, characterized in that, The raw materials include the following mass fractions: white cement 35-45 parts, acetylated modified nanocellulose 10-15 parts, white porous ceramic loaded with TiO2 45-50 parts, cardanol glycidyl ether 0.3-0.5 parts, polycarboxylic acid water reducing agent 1.0-1.5 parts, defoaming agent 0.03-0.06 parts, and water 12-20 parts; The preparation method of the acetylated modified nanocellulose is as follows: nanocellulose is immersed in a mixed solution of acetic anhydride and pyridine, heated for reaction, washed, and dried to obtain acetylated modified nanocellulose.

2. The lightweight high-strength self-cleaning white ultra-high-performance concrete according to claim 1, characterized in that, The mixed solution of acetic anhydride and pyridine is prepared by mixing acetic anhydride and pyridine at a volume ratio of 1:2.5-1:3.5; the mass of the nanocellulose and the volume of the mixed solution of acetic anhydride and pyridine are in a ratio of 1g:10-20mL; the heating temperature of the heating reaction is 60-70℃, and the reaction time is 2-3h.

3. The lightweight high-strength self-cleaning white ultra-high-performance concrete according to claim 1, characterized in that, The nanocellulose is cellulose nanofiber, with a whiteness of ≥90%, a diameter of 10-50nm, and a length of 1-5μm; the washing is first performed using a 5-8% mass fraction sodium carbonate aqueous solution, and then repeated using water until the pH is 6.5-7.0; the drying temperature is 60-80℃, and the drying time is 4-8h.

4. The lightweight high-strength self-cleaning white ultra-high-performance concrete according to claim 1, characterized in that, The preparation method of the white porous ceramic loaded with TiO2 is as follows: the white porous ceramic is immersed in a tetrabutyl titanate ethanol solution, taken out, hydrolyzed by heating, and then dried and calcined to obtain the white porous ceramic loaded with TiO2; the TiO2 loaded on the surface of the white porous ceramic is anatase nano-TiO2 with a particle size of 10-50 nm and a density of 4.0-4.3 g / cm 3 , and a Mohs hardness of 6-7.

5. The lightweight high-strength self-cleaning white ultra-high-performance concrete according to claim 4, characterized in that, The ethanol solution of tetrabutyl titanate is prepared by mixing tetrabutyl titanate and anhydrous ethanol at a volume ratio of 1:8-1:12; the mass of the white porous ceramic and the volume of the ethanol solution of tetrabutyl titanate are in a ratio of 1g:10-20mL, and the impregnation time is 20-40min; the heating temperature of the hydrolysis is 70-90℃, and the hydrolysis time is 1.5-2.5h; the drying temperature is 70-90℃, and the drying time is 10-14h; the calcination temperature is 450-550℃, and the holding time is 1.5-2.5h.

6. The lightweight high-strength self-cleaning white ultra-high-performance concrete according to claim 4, characterized in that, The white porous ceramic has whiteness ≥ 88%, particle size ≤ 0.075 mm, density of 1.8-2.0 g / cm 3 , specific surface area of 800-1000 m 2 / g, porosity of 40%-60%, and average pore size of 50-200 nm; the white porous ceramic is sequentially cleaned by ultrasonic cleaning with water and anhydrous ethanol, and the total ultrasonic cleaning time is 10-20 min, and then dried; the heating rate of the calcination is 3-7 ℃ / min.

7. The lightweight high-strength self-cleaning white ultra-high-performance concrete according to claim 1, characterized in that, The white cement has a whiteness of ≥85%, a strength grade of ≥42.5 grade, and an average particle size of 12-20μm; the cardanol glycidyl ether has a viscosity of 30-50mPa·s and an epoxy value of 0.20-0.28eq / 100g; the polycarboxylic acid water reducing agent has a water reducing rate of 35-45%; and the defoaming agent is a polyether defoaming agent.

8. A method of producing a lightweight high-strength self-cleaning white ultra-high performance concrete according to any one of claims 1 to 7, characterized in that, The method comprises the following steps: 1) After the white cement and the acetylated modified nanocellulose are uniformly stirred, a part of the water and the water reducing agent are added and stirred; 2) After the white porous ceramic loaded with TiO2, the remaining water and the water reducing agent are continuously added, the bio-based hydrophobic agent and the defoaming agent are added and uniformly stirred, to obtain the ultra-high performance concrete.

9. The method of manufacturing a lightweight high-strength self-cleaning white ultra-high performance concrete according to claim 8, characterized in that, The ultrahigh performance concrete is first irradiated by ultraviolet light with a wavelength of 350-380 nm and an irradiance of 8-12 W / m 2 for 1.5-2.5 h during curing, and then cured to a predetermined age; the density of the ultrahigh performance concrete is 1.9-2.3 g / cm 3 , the whiteness is greater than or equal to 87%, the water absorption is less than or equal to 1.0%, the 28d compressive strength is greater than or equal to 128 MPa, the 28d dry shrinkage is less than or equal to 0.06%, the 28d surface organic matter content is less than or equal to 0.1 g / cm 2 , and the CO2 emission is less than or equal to 200 kg / m 3 .

10. The method of producing a lightweight high-strength self-cleaning white ultra-high performance concrete according to claim 8, characterized in that, In step 1), the stirring rate is 60-90r / min, the white cement and the nanocellulose are stirred for 4-6min after being mixed, the water and the water reducing agent are stirred for 1-2min after being added, and the amount of the water and the water reducing agent added is 45-55% of the total amount; in step 2), the stirring rate is 90-120r / min, and the stirring time is 4-5min.

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