Easy-to-release textured plain concrete and its preparation method and application

Abstract

The present invention relates to the field of concrete technology, and in particular to a textured plain concrete that is easy to demould, and a preparation method and application thereof. The plain concrete uses modified nano-silica as a key component, and through silane coupling agent grafting, sulfonic acid group and carboxylic acid group multiple surface modifications, the efficient dispersion and functional synergy of nano-silica in the concrete system are achieved. The modified nano-silica not only improves the interface characteristics between concrete and formwork, reduces adhesion, makes the demoulding process smoother, avoids surface damage and texture defects, but also improves the density, compressive strength and durability of concrete. This material is particularly suitable for engineering fields with high requirements on aesthetics and structural performance, such as building facades and landscape structures, and has broad application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete, and in particular to an easy-to-release textured plain concrete and a preparation method and application thereof. Background Art

[0002] As a building material requiring no secondary decoration, bare concrete is widely used in modern architecture for its naturally beautiful surface and streamlined construction process. Textured bare concrete, by designing various textures on the formwork, creates a rich, artistic effect on the concrete surface, further enhancing the aesthetic value and personalized expression of the building. However, in practical application, textured bare concrete faces numerous challenges, particularly issues with demolding and surface quality control.

[0003] Traditional textured bare concrete is prone to localized surface damage during demolding due to the strong adhesion between the concrete and the formwork, affecting the clarity of the texture and the smoothness of the concrete surface. Demolding is particularly difficult and poses a higher risk of damage for complex textures. Furthermore, bubbles are prone to forming on the concrete surface during vibration and molding. These bubbles then become pores after demolding, severely impacting the concrete's aesthetics.

[0004] Currently, common solutions in the industry focus on improving release agents and optimizing construction processes. While conventional release agents can reduce the adhesion between concrete and formwork to a certain extent, they are still not ideal for projects with complex textures and high demands for fine surface quality. Especially in large-scale construction, uneven release agent dosage or improper application procedures can lead to inconsistent release results.

[0005] In terms of concrete formulation, traditional concrete design focuses primarily on mechanical properties and durability, with insufficient consideration given to surface quality and demolding properties. While water-reducing agents used in conventional concrete can improve concrete's fluidity, their ability to control air bubbles is limited, making them ineffective in addressing surface porosity. Some projects have incorporated nanomaterials to improve concrete performance, but conventional nanomaterials have high surface energy and are prone to agglomeration, making them difficult to disperse and potentially leading to the formation and retention of more air bubbles.

[0006] Nanosilica, as a concrete admixture, theoretically improves concrete performance through both physical filling and chemical activity. However, in practice, its high surface area and strong surface activity lead to severe agglomeration, hindering its full performance benefits. Furthermore, nanosilica poorly bonds with the cement paste interface, failing to effectively improve concrete's microstructure and the quality of the interfacial transition zone.

[0007] Existing technologies lack systematic solutions tailored to the specific needs of textured bare concrete, particularly those that address the synergistic optimization of demoulding performance and surface quality at the material component level. Therefore, developing textured bare concrete that is easy to demould, has minimal surface porosity, and exhibits excellent mechanical properties is crucial for enhancing architectural aesthetics and construction efficiency. Summary of the Invention

[0008] In view of this, the purpose of the present invention is to provide a textured plain concrete that is easy to demold, and its preparation method and application, in order to solve the problem that textured plain concrete is prone to surface pores during the demolding process, affecting its aesthetics and mechanical properties, and also making demolding difficult.

[0009] Based on the above objectives, the present invention provides a textured plain concrete that is easy to demold, comprising the following raw materials in parts by weight: 310-390 parts of Portland cement, 8-12 parts of modified nano-silica, 60-90 parts of mineral admixture, 750-850 parts of fine aggregate, 900-1000 parts of coarse aggregate, 4-8 parts of polycarboxylate water reducer, and 160-180 parts of water.

[0010] Furthermore, the mineral admixture is one of Class I fly ash and Class II fly ash.

[0011] Furthermore, the fine aggregate is machine-made sand, and the fineness modulus of the machine-made sand is 2.4-3.0 and the mud content is 0.1-1%.

[0012] Furthermore, the coarse aggregate is basalt aggregate, and the particle size specification of the basalt aggregate is 5-25 mm.

[0013] Furthermore, the modified nano-silica is prepared by the following steps:

[0014] Step 1: using silane coupling agent KH-560 to graft-modify nano-silica to obtain grafted nano-silica;

[0015] Step 2: Sodium aminobenzenesulfonate and ethylene glycol diglycidyl ether are cross-linked on the surface of the grafted nano-silica through epoxy and amino reactions to obtain aminobenzenesulfonic acid grafted silica;

[0016] Step 3: Aminobenzenesulfonic acid grafted silica and sodium acrylate undergo addition reaction of amino and alkenyl groups to obtain modified silica.

[0017] Furthermore, the average particle size of the nano-silicon dioxide in step 1 is 20-100 nm.

[0018] Furthermore, the sodium aminobenzenesulfonate in step 2 is one of sodium o-aminobenzenesulfonate, sodium m-aminobenzenesulfonate, and sodium p-aminobenzenesulfonate.

[0019] Furthermore, in step 1, the mass ratio of the silane coupling agent KH-560 to the nano-silicon dioxide is 0.2-0.4:4-6.

[0020] Furthermore, in step 2, the mass ratio of sodium aminobenzenesulfonate, ethylene glycol diglycidyl ether and grafted nano-silica is 6-10:2-4:4-6.

[0021] Furthermore, in step 3, the mass ratio of aminobenzenesulfonic acid grafted silica to sodium acrylate is 12-20:3-6.

[0022] A method for preparing textured plain concrete that is easy to demould comprises the following steps:

[0023] Step 1: Weigh each raw material according to mass fraction;

[0024] Step 2: Add Portland cement, modified nano-silica, mineral admixtures, fine aggregate and coarse aggregate into a mixer and stir for 2-30 minutes to obtain dry concrete;

[0025] Step 3: Add water and polycarboxylate water reducer to the dry concrete material, and then continue stirring for 1-3 minutes to obtain concrete slurry;

[0026] Step 4: Apply water-based release agent on the surface of the textured formwork, then fix the formwork and pour concrete slurry. After vibrating and compacting, cover it with plastic film. 48-72 hours after the pouring is completed, remove the formwork and cure it to obtain textured plain concrete that is easy to demold.

[0027] Application of textured plain concrete that is easy to demould, and application of the textured plain concrete that is easy to demould, prepared using the above raw materials and preparation method, in the field of building facades.

[0028] The easy-to-release textured plain concrete of the present invention achieves synergistic optimization of concrete demoulding performance, surface quality and mechanical properties by adopting innovative modified nano-silica technology.

[0029] The modified nano-silica was successfully modified through a carefully designed three-step process, successfully introducing a variety of functional groups onto the nanoparticle surface. First, silane coupling agent grafting improved the organic compatibility of the nanoparticles; second, aminobenzenesulfonic acid grafting imparted sulfonic acid groups to the particle surface; and finally, sodium acrylate modification further introduced carboxylic acid groups. This multi-step surface modification strategy significantly altered the surface properties of the nano-silica, resulting in excellent dispersibility and functionality in concrete paste.

[0030] The modified nano-silica forms a synergistic effect with the polycarboxylate superplasticizer. The sulfonic acid and carboxylic acid groups together enhance the electrostatic repulsion between cement particles, effectively improving the fluidity of the concrete paste. This excellent fluidity ensures that the concrete can fully fill every part of the complex textured formwork, creating a clear and complete texture.

[0031] At the same time, the functional groups on the surface of the modified nanosilica form strong chemical bonds with cement hydration products, significantly enhancing the quality of the interfacial transition zone. This strengthening effect not only increases the overall density of the concrete but also effectively reduces the formation of surface pores. The reduction in surface pores directly improves the aesthetics of the exposed concrete and enhances the quality of the building's exterior.

[0032] During the demolding process, the unique surface structure of modified nano-silica reduces the adhesion between the concrete and the formwork, allowing for smooth demolding even under complex texture conditions, effectively avoiding the surface damage and texture defects commonly encountered with traditional bare concrete demolding. This feature significantly improves construction efficiency and reduces rework rates.

[0033] Furthermore, modified nanosilica optimizes the microstructure of concrete through its dual effects of physical filling and hydration promotion, reducing internal defects and microcracks, thereby enhancing the concrete's compressive strength and durability. In particular, the carboxylic acid groups introduced onto the nanoparticle surface form stable complexes with calcium ions in cement hydration products, further enhancing the overall performance of concrete.

[0034] The easy-to-release textured plain concrete of the present invention not only solves the technical difficulties encountered in the demolding process of traditional textured plain concrete, but also improves the basic mechanical properties of concrete while ensuring aesthetics, providing a high-quality material option for applications such as high-quality building exterior walls and landscape structures. DETAILED DESCRIPTION

[0035] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to specific embodiments.

[0036] Example 1

[0037] A textured plain concrete that is easy to demould comprises the following raw materials in parts by weight: 310 parts of Portland cement, 8 parts of modified nano-silica, 90 parts of mineral admixture, 750 parts of fine aggregate, 900 parts of coarse aggregate, 4 parts of polycarboxylate water reducer, and 160 parts of water;

[0038] The mineral admixture is Class I fly ash, the fine aggregate is machine-made sand with a fineness modulus of 2.4 and a mud content of 0.1%, the coarse aggregate is basalt aggregate with a particle size of 5-25 mm, and the modified nano-silica is prepared by the following steps:

[0039] Step 1, by weight, 4 parts of nano-silica, 0.2 parts of silane coupling agent KH-560, and 200 parts of toluene were mixed in a four-necked flask, equipped with a condenser and a thermometer, turned on mechanical stirring, and reacted at a temperature of 105 ° C for 6 hours. After the reaction, the solid was filtered out and washed with anhydrous ethanol and deionized water, and then dried to constant weight to obtain grafted nano-silica;

[0040] Step 2: Mix 4 parts of grafted nano-silica, 6 parts of sodium o-aminobenzenesulfonate, 2 parts of ethylene glycol diglycidyl ether, and 50 parts of anhydrous ethanol in a four-necked flask, install a condenser and a thermometer, start mechanical stirring, and react at 75°C for 4 hours. Filter the solid and wash it with anhydrous ethanol and deionized water in sequence, and then dry it to constant weight to obtain aminobenzenesulfonic acid grafted silica;

[0041] Step 3: 12 parts by mass of aminobenzenesulfonic acid grafted silica, 3 parts of sodium acrylate, 0.3 parts of 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, and 150 parts by volume of a 60% ethanol solution were mixed in a four-necked flask, equipped with a condenser and a thermometer, and mechanical stirring was turned on. The mixture was reacted at 35°C for 2 hours. The solid was filtered and washed with anhydrous ethanol and deionized water in sequence, and then dried to constant weight to obtain modified silica;

[0042] The particle size of the nano-silicon dioxide used in this embodiment is 1-100 nm.

[0043] A method for preparing textured plain concrete that is easy to demould comprises the following steps:

[0044] The first step is to weigh each raw material according to mass fraction;

[0045] Step 2: Add Portland cement, modified nano-silica, mineral admixtures, fine aggregate, and coarse aggregate into a mixer and stir for 2 minutes to obtain dry concrete.

[0046] Step 3: Add water and polycarboxylate water reducer to the dry concrete material, and then continue stirring for 1 minute to obtain concrete slurry;

[0047] Step 4: Apply water-based release agent on the surface of the textured formwork, then fix the formwork and pour concrete slurry. After vibrating and compacting, cover it with plastic film. 48 hours after the pouring is completed, remove the formwork and cure it to obtain textured plain concrete that is easy to demold.

[0048] Example 2

[0049] A textured plain concrete that is easy to demould comprises the following raw materials in parts by weight: 350 parts of Portland cement, 10 parts of modified nano-silica, 75 parts of mineral admixture, 800 parts of fine aggregate, 950 parts of coarse aggregate, 6 parts of polycarboxylate water reducer, and 170 parts of water;

[0050] The mineral admixture is Class II fly ash, the fine aggregate is machine-made sand with a fineness modulus of 2.7 and a mud content of 0.6%, the coarse aggregate is basalt aggregate with a particle size of 5-25 mm, and the modified nano-silica is prepared by the following steps:

[0051] Step 1, by weight, 5 parts of nano-silica, 0.3 parts of silane coupling agent KH-560, and 250 parts of toluene were mixed in a four-necked flask, a condenser and a thermometer were installed, mechanical stirring was turned on, and the reaction was carried out at a temperature of 108 ° C for 7 hours. After the reaction was completed, the solid was filtered out and washed with anhydrous ethanol and deionized water, and then dried to constant weight to obtain grafted nano-silica;

[0052] Step 2: Mix 5 parts of grafted nano-silica, 8 parts of sodium p-aminobenzenesulfonate, 3 parts of ethylene glycol diglycidyl ether, and 90 parts of anhydrous ethanol in a four-necked flask, install a condenser and a thermometer, start mechanical stirring, and react at 78°C for 5 hours. Filter the solid and wash it with anhydrous ethanol and deionized water in sequence, and then dry it to constant weight to obtain aminobenzenesulfonic acid grafted silica;

[0053] Step 3: 16 parts of aminobenzenesulfonic acid grafted silica, 4.5 parts of sodium acrylate, 0.4 parts of 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, and 180 parts of 60% by volume ethanol solution were mixed in a four-necked flask, equipped with a condenser and a thermometer, and mechanical stirring was turned on. The mixture was reacted at a temperature of 38°C for 3 hours. The solid was filtered and washed with anhydrous ethanol and deionized water in sequence, and then dried to constant weight to obtain modified silica;

[0054] The particle size of the nano-silicon dioxide used in this embodiment is 1-100 nm.

[0055] A method for preparing textured plain concrete that is easy to demould comprises the following steps:

[0056] The first step is to weigh each raw material according to mass fraction;

[0057] Step 2: Add Portland cement, modified nano-silica, mineral admixtures, fine aggregate, and coarse aggregate into a mixer and stir for 16 minutes to obtain dry concrete.

[0058] Step 3: Add water and polycarboxylate water reducer to the dry concrete material, and then continue stirring for 2 minutes to obtain concrete slurry;

[0059] Step 4: Apply water-based release agent on the surface of the textured formwork, then fix the formwork and pour concrete slurry. After vibrating and compacting, cover it with plastic film. After 60 hours of pouring, remove the formwork and cure it to obtain textured plain concrete that is easy to demold.

[0060] Example 3

[0061] A textured plain concrete that is easy to demould comprises the following raw materials in parts by weight: 390 parts of Portland cement, 12 parts of modified nano-silica, 60 parts of mineral admixture, 850 parts of fine aggregate, 1000 parts of coarse aggregate, 8 parts of polycarboxylate water reducer, and 180 parts of water;

[0062] The mineral admixture is Class I fly ash, the fine aggregate is machine-made sand with a fineness modulus of 3.0 and a mud content of 1%, the coarse aggregate is basalt aggregate with a particle size of 5-25 mm, and the modified nano-silica is prepared by the following steps:

[0063] Step 1, by weight, 6 parts of nano-silica, 0.4 parts of silane coupling agent KH-560, and 300 parts of toluene were mixed in a four-necked flask, equipped with a condenser and a thermometer, turned on mechanical stirring, and reacted at a temperature of 110 ° C for 8 hours. After the reaction, the solid was filtered out and washed with anhydrous ethanol and deionized water, and then dried to constant weight to obtain grafted nano-silica;

[0064] Step 2: Mix 6 parts of grafted nano-silica, 10 parts of sodium m-aminobenzenesulfonate, 4 parts of ethylene glycol diglycidyl ether, and 100 parts of anhydrous ethanol in a four-necked flask, install a condenser and a thermometer, start mechanical stirring, react at 80°C for 6 hours, filter out the solid, wash with anhydrous ethanol and deionized water in sequence, and then dry to constant weight to obtain aminobenzenesulfonic acid grafted silica;

[0065] Step 3: 20 parts by mass of aminobenzenesulfonic acid grafted silica, 6 parts of sodium acrylate, 0.6 parts of 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, and 200 parts by volume of 60% ethanol solution were mixed in a four-necked flask, equipped with a condenser and a thermometer, and mechanical stirring was turned on. The mixture was reacted at a temperature of 40°C for 4 hours. The solid was filtered and washed with anhydrous ethanol and deionized water in sequence, and then dried to constant weight to obtain modified silica;

[0066] The particle size of the nano-silicon dioxide used in this embodiment is 1-100 nm.

[0067] A method for preparing textured plain concrete that is easy to demould comprises the following steps:

[0068] The first step is to weigh each raw material according to mass fraction;

[0069] Step 2: Add Portland cement, modified nano-silica, mineral admixtures, fine aggregate, and coarse aggregate into a mixer and stir for 30 minutes to obtain dry concrete.

[0070] Step 3: Add water and polycarboxylate water reducer to the dry concrete material, and then continue stirring for 3 minutes to obtain concrete slurry;

[0071] Step 4: Apply water-based release agent on the surface of the textured formwork, then fix the formwork and pour concrete slurry. After vibrating and compacting, cover it with plastic film. 72 hours after the pouring is completed, remove the formwork and cure it to obtain textured plain concrete that is easy to demold.

[0072] Comparative Example 1

[0073] The difference between Comparative Example 1 and Example 2 is that the modified nano-silica is replaced by nano-silica; the specific contents are as follows:

[0074] A concrete comprising the following raw materials in parts by weight: 350 parts of Portland cement, 10 parts of nano-silica, 75 parts of mineral admixture, 800 parts of fine aggregate, 950 parts of coarse aggregate, 6 parts of polycarboxylate water reducer, and 170 parts of water;

[0075] The mineral admixture is grade II fly ash, the fine aggregate is machine-made sand with a fineness modulus of 2.7 and a mud content of 0.6%, and the coarse aggregate is basalt aggregate with a particle size of 5-25 mm.

[0076] The particle size of the nano-silicon dioxide used in this comparative example is 1-100 nm.

[0077] A method for preparing concrete comprises the following steps:

[0078] The first step is to weigh each raw material according to mass fraction;

[0079] Step 2: Add Portland cement, nano-silica, mineral admixtures, fine aggregate, and coarse aggregate into a mixer and stir for 16 minutes to obtain dry concrete.

[0080] Step 3: Add water and polycarboxylate water reducer to the dry concrete material, and then continue stirring for 2 minutes to obtain concrete slurry;

[0081] Step 4: Apply water-based release agent on the surface of the textured formwork, then fix the formwork and pour concrete slurry. After vibrating and compacting, cover it with plastic film. After 60 hours of pouring, remove the formwork and cure to obtain concrete.

[0082] Comparative Example 2

[0083] The difference between Comparative Example 2 and Example 2 is that no modified nano-silica is added; the specific contents are as follows:

[0084] A concrete comprising the following raw materials in parts by weight: 350 parts of Portland cement, 75 parts of mineral admixture, 800 parts of fine aggregate, 950 parts of coarse aggregate, 6 parts of polycarboxylate water reducer, and 170 parts of water;

[0085] The mineral admixture is grade II fly ash, the fine aggregate is machine-made sand with a fineness modulus of 2.7 and a mud content of 0.6%, and the coarse aggregate is basalt aggregate with a particle size of 5-25 mm.

[0086] A method for preparing concrete comprises the following steps:

[0087] The first step is to weigh each raw material according to mass fraction;

[0088] Step 2: Add Portland cement, mineral admixtures, fine aggregate and coarse aggregate into a mixer and mix for 16 minutes to obtain dry concrete;

[0089] Step 3: Add water and polycarboxylate water reducer to the dry concrete material, and then continue stirring for 2 minutes to obtain concrete slurry;

[0090] Step 4: Apply water-based release agent on the surface of the textured formwork, then fix the formwork and pour concrete slurry. After vibrating and compacting, cover it with plastic film. After 60 hours of pouring, remove the formwork and cure to obtain concrete.

[0091] Comparative Example 3

[0092] The difference between Comparative Example 3 and Example 2 is that ethylene glycol diglycidyl ether is not added in step 2;

[0093] A concrete comprising the following raw materials in parts by weight: 350 parts of Portland cement, 10 parts of modified nano-silica, 75 parts of mineral admixture, 800 parts of fine aggregate, 950 parts of coarse aggregate, 6 parts of polycarboxylate water reducer, and 170 parts of water;

[0094] The mineral admixture is Class II fly ash, the fine aggregate is machine-made sand with a fineness modulus of 2.7 and a mud content of 0.6%, the coarse aggregate is basalt aggregate with a particle size of 5-25 mm, and the modified nano-silica is prepared by the following steps:

[0095] Step 1, by weight, 5 parts of nano-silica, 0.3 parts of silane coupling agent KH-560, and 250 parts of toluene were mixed in a four-necked flask, a condenser and a thermometer were installed, mechanical stirring was turned on, and the reaction was carried out at a temperature of 108 ° C for 7 hours. After the reaction was completed, the solid was filtered out and washed with anhydrous ethanol and deionized water, and then dried to constant weight to obtain grafted nano-silica;

[0096] Step 2: Mix 5 parts of grafted nano-silica, 8 parts of sodium p-aminobenzenesulfonate, and 90 parts of anhydrous ethanol in a four-necked flask, install a condenser and a thermometer, start mechanical stirring, and react at 78°C for 5 hours. Filter the solid and wash it with anhydrous ethanol and deionized water in sequence, and then dry it to constant weight to obtain aminobenzenesulfonic acid grafted silica;

[0097] Step 3: 16 parts of aminobenzenesulfonic acid grafted silica, 4.5 parts of sodium acrylate, 0.4 parts of 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, and 180 parts of 60% by volume ethanol solution were mixed in a four-necked flask, equipped with a condenser and a thermometer, and mechanical stirring was turned on. The mixture was reacted at a temperature of 38°C for 3 hours. The solid was filtered and washed with anhydrous ethanol and deionized water in sequence, and then dried to constant weight to obtain modified silica;

[0098] The particle size of the nano-silicon dioxide used in this comparative example is 1-100 nm.

[0099] A method for preparing concrete comprises the following steps:

[0100] The first step is to weigh each raw material according to mass fraction;

[0101] Step 2: Add Portland cement, modified nano-silica, mineral admixtures, fine aggregate, and coarse aggregate into a mixer and stir for 16 minutes to obtain dry concrete.

[0102] Step 3: Add water and polycarboxylate water reducer to the dry concrete material, and then continue stirring for 2 minutes to obtain concrete slurry;

[0103] Step 4: Apply water-based release agent on the surface of the textured formwork, then fix the formwork and pour concrete slurry. After vibrating and compacting, cover it with plastic film. After 60 hours of pouring, remove the formwork and cure to obtain concrete.

[0104] Comparative Example 4

[0105] The difference between Comparative Example 4 and Example 2 is that the modified nano-silica is replaced with aminobenzenesulfonic acid grafted silica;

[0106] The specific steps are as follows:

[0107] A concrete comprising the following raw materials in mass fractions: 350 parts of Portland cement, 10 parts of aminobenzenesulfonic acid grafted silica, 75 parts of mineral admixture, 800 parts of fine aggregate, 950 parts of coarse aggregate, 6 parts of polycarboxylate water reducer, and 170 parts of water;

[0108] The mineral admixture is Class II fly ash, the fine aggregate is machine-made sand with a fineness modulus of 2.7 and a mud content of 0.6%, the coarse aggregate is basalt aggregate with a particle size of 5-25 mm, and the aminobenzenesulfonic acid grafted silica is prepared by the following steps:

[0109] Step 1, by weight, 5 parts of nano-silica, 0.3 parts of silane coupling agent KH-560, and 250 parts of toluene were mixed in a four-necked flask, a condenser and a thermometer were installed, mechanical stirring was turned on, and the reaction was carried out at a temperature of 108 ° C for 7 hours. After the reaction was completed, the solid was filtered out and washed with anhydrous ethanol and deionized water, and then dried to constant weight to obtain grafted nano-silica;

[0110] Step 2: Mix 5 parts of grafted nano-silica, 8 parts of sodium p-aminobenzenesulfonate, 3 parts of ethylene glycol diglycidyl ether, and 90 parts of anhydrous ethanol in a four-necked flask, install a condenser and a thermometer, start mechanical stirring, and react at 78°C for 5 hours. Filter the solid and wash it with anhydrous ethanol and deionized water in sequence, and then dry it to constant weight to obtain aminobenzenesulfonic acid grafted silica;

[0111] The particle size of the nano-silicon dioxide used in this comparative example is 1-100 nm.

[0112] A method for preparing concrete comprises the following steps:

[0113] The first step is to weigh each raw material according to mass fraction;

[0114] Step 2: Add Portland cement, modified nano-silica, mineral admixtures, fine aggregate, and coarse aggregate into a mixer and stir for 16 minutes to obtain dry concrete.

[0115] Step 3: Add water and polycarboxylate water reducer to the dry concrete material, and then continue stirring for 2 minutes to obtain concrete slurry;

[0116] Step 4: Apply water-based release agent on the surface of the textured formwork, then fix the formwork and pour concrete slurry. After vibrating and compacting, cover it with plastic film. After 60 hours of pouring, remove the formwork and cure to obtain concrete.

[0117] The concrete obtained in Examples 1-3 and Comparative Examples 1-4 was subjected to performance tests. The slump of each component concrete was measured with reference to the national standard GB / T 50080-2016 "Test method for slump of concrete", and the surface porosity of each component concrete after demolding was recorded. After curing, the compressive strength of each component concrete specimen was tested with reference to the national standard GB / T 50081-2019 "Standard for test methods for physical and mechanical properties of concrete". The test results are shown in Table 1:

[0118] Table 1 Performance test results

[0119]

[0120] Data Analysis:

[0121] As can be seen from the data trends of Examples 1-3 in Table 1, slump, compressive strength, and pore count exhibit a synergistic optimization relationship. The negative charge generated by the hydrolysis of the sulfonic acid groups on the surface of the modified nanosilica may form an electrostatic synergistic effect with the negative charge of the polycarboxylate superplasticizer, enhancing the repulsion between cement particles and thus improving the fluidity of the slurry. At the same time, the surface carboxyl groups and calcium ions in the cement hydration products form a dense interfacial transition zone through complexation, effectively filling the microporous structure and reducing pore connectivity. This dual effect may optimize the aggregate-paste interface bonding strength, improving density while maintaining high fluidity.

[0122] Example 2 exhibits superior fluidity, compactness, and mechanical properties compared to Comparative Example 1. Unmodified nanosilica is prone to agglomeration due to its high surface energy, potentially hindering its uniform dispersion in the slurry and leading to localized water encapsulation and the formation of pores. However, the sulfonic acid groups on the surface of the modified nanoparticles inhibit agglomeration through charge repulsion and simultaneously form a steric hindrance synergistic effect with the water reducer, potentially optimizing the nucleation and growth of the hydration products and forming a more uniform microstructure.

[0123] Comparative Example 2 exhibits a significant performance drop due to the absence of the nanocomposite. Modified nanosilica may improve performance through a dual mechanism: on the one hand, the nanoparticles act as crystal nuclei to accelerate the hydration reaction and shorten the setting time; on the other hand, their surface functional groups selectively bond with cement minerals, potentially suppressing the concentration of early hydration heat. This regulatory effect can reduce microcracks caused by thermal stress and simultaneously reduce capillary porosity through a physical filling effect.

[0124] Comparative Example 3 lacks the crosslinker ethylene glycol diglycidyl ether during the modification process, resulting in insufficient grafting density. The grafting of ethylene glycol diglycidyl ether helps introduce appropriate polarity and steric hindrance to the nanosilica surface, improving the nanoparticles' dispersibility and compatibility with organic water-reducing agents, thereby optimizing the overall dispersion and interface structure. During concrete pouring and molding, this molecular structure modification significantly reduces the risk of particle self-aggregation and pore formation, enhancing the density and smoothness of the finished surface, and indirectly improving compressive strength.

[0125] Comparison of Example 2 and Comparative Example 4 reveals the necessity of modification in Step 3. Comparative Example 4, which only grafted silica with aminobenzenesulfonic acid (without Step 3), exhibited degraded performance, indicating that the absence of carboxylic acid groups was a key factor. While the aminobenzenesulfonic acid graft provided sulfonic acid groups to improve dispersibility, the lack of carboxylic acid groups weakened effective complexation with calcium ions, resulting in insufficient interfacial bonding. In contrast, the introduction of sodium acrylate in Example 2 imparted carboxylic acid groups to the particle surface via a Michael addition reaction. These groups may strengthen the cement-nanoparticle interface through chemical bonding, optimizing pore-filling efficiency and thus improving density and mechanical properties.

[0126] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present invention is limited to these examples. Within the scope of the present invention, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

Claims

1. A textured plain concrete that is easy to demould, characterized in that: Contains the following raw materials in parts by mass: 310-390 parts of Portland cement, 8-12 parts of modified nano-silica, 60-90 parts of mineral admixture, 750-850 parts of fine aggregate, 900-1000 parts of coarse aggregate, 4-8 parts of polycarboxylate water reducer, and 160-180 parts of water; The modified nano-silica is prepared by the following steps: Step 1: using silane coupling agent KH-560 to graft-modify nano-silica to obtain grafted nano-silica; Step 2: Sodium aminobenzenesulfonate and ethylene glycol diglycidyl ether are cross-linked on the surface of the grafted nano-silica through epoxy and amino reactions to obtain aminobenzenesulfonic acid grafted silica; Step 3: Aminobenzenesulfonic acid grafted silica and sodium acrylate undergo addition reaction of amino and alkenyl groups to obtain modified silica; In the step 2, the mass ratio of sodium aminobenzenesulfonate, ethylene glycol diglycidyl ether and grafted nano-silica is 6-10:2-4:4-6.

2. The easy-to-release textured plain concrete according to claim 1, characterized in that: The mineral admixture is one of Class I fly ash and Class II fly ash.

3. The easy-to-release textured plain concrete according to claim 1, characterized in that: The fine aggregate is machine-made sand, and the fineness modulus of the machine-made sand is 2.4-3.0 and the mud content is 0.1-1%.

4. The easy-to-release textured plain concrete according to claim 1, characterized in that: The coarse aggregate is basalt aggregate, and the particle size specification of the basalt aggregate is 5-25 mm.

5. The easy-to-release textured plain concrete according to claim 1, characterized in that: The average particle size of the nano-silicon dioxide in step 1 is 20-100 nm.

6. The easy-to-release textured plain concrete according to claim 1, characterized in that: In the step 2, the sodium aminobenzenesulfonate is one of sodium o-aminobenzenesulfonate, sodium m-aminobenzenesulfonate and sodium p-aminobenzenesulfonate.

7. The easy-to-release textured plain concrete according to claim 1, characterized in that: In the step 1, the mass ratio of the silane coupling agent KH-560 to the nano-silicon dioxide is 0.2-0.4:4-6.

8. The easy-to-release textured plain concrete according to claim 1, characterized in that: In the step 3, the mass ratio of aminobenzenesulfonic acid grafted silica to sodium acrylate is 12-20:3-6.

9. A method for preparing the easily demoulding textured plain concrete according to any one of claims 1 to 8, characterized in that: The following steps are involved: Step 1: Weigh each raw material according to mass fraction; Step 2: Add Portland cement, modified nano-silica, mineral admixtures, fine aggregate and coarse aggregate into a mixer and stir for 2-30 minutes to obtain dry concrete; Step 3: Add water and polycarboxylate water reducer to the dry concrete material, and then continue stirring for 1-3 minutes to obtain concrete slurry; Step 4: Apply water-based release agent on the surface of the textured formwork, then fix the formwork and pour concrete slurry. After vibrating and compacting, cover it with plastic film. 48-72 hours after the pouring is completed, remove the formwork and cure it to obtain textured plain concrete that is easy to demold.

10. An application of the easily demouldable textured plain concrete according to any one of claims 1 to 8, characterized in that: Used for building facades.

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