Fair-faced concrete, its preparation method and application

Abstract

This invention provides a fair-faced concrete, its preparation method, and its application. The fair-faced concrete of this invention, by weight, comprises: cementitious material: 350-410 parts; coarse aggregate: 900-1000 parts; fine aggregate: 800-1000 parts; compound admixture: 7-10 parts; and water: 140-180 parts. The compound admixture is a mixture of C4 mother liquor, C6 mother liquor, polyvinyl alcohol water-retaining agent, ether-based defoamer, and workability regulator. The fair-faced concrete of this invention, while meeting the appearance requirements of fair-faced concrete, also meets the construction requirements of high-polish self-compacting concrete (possessing good fluidity and anti-segregation properties). This invention also provides a preparation method and application of fair-faced concrete.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to fair-faced concrete, its preparation method, and its application. Background Technology

[0002] Fair-faced concrete is a basic building material widely used in housing, bridges, roads, and other engineering projects. Its main components include cement, sand, aggregate, and water, which are mixed to create a sturdy structural material. The production process of fair-faced concrete is relatively simple. First, appropriate amounts of cement, sand, and aggregate are mixed in a mixer according to a specific ratio. During mixing, admixtures or additives can be added as needed to improve the concrete's properties. Water is gradually added during mixing until the concrete reaches the appropriate moisture and fluidity. After mixing, the concrete needs to be transported to the construction site for pouring as soon as possible. During pouring, it is essential to ensure the concrete is evenly covered in the designated area, and air bubbles should be eliminated by vibration or tapping. The concrete needs to be kept moist after construction to promote its gradual curing and strengthening process. The advantages of fair-faced concrete include: durability, relatively low cost, ease of construction, and a certain degree of impermeability. It can be reinforced and modified to varying degrees according to project needs to meet specific design requirements. However, fair-faced concrete also has some limitations. For example, it may shrink, crack, or be affected by environmental factors. To overcome these problems, improvements can be made by using additives and controlling the construction process.

[0003] High-displacement, non-vibrating concrete is a special type of concrete characterized by the elimination of traditional vibration or tamping during pouring. Compared to conventional concrete, high-displacement, non-vibrating concrete typically requires a longer mixing time to ensure thorough mixing. During pouring, the self-weight and construction method of high-displacement, non-vibrating concrete allow air voids to dissipate during natural settling, resulting in fully compacted and uniformly distributed concrete. This construction method not only saves construction time and labor costs but also reduces noise and vibration impacts on the surrounding environment. After proper curing, high-displacement, non-vibrating concrete exhibits high compressive strength and excellent durability. This special type of concrete is suitable for vibration-sensitive or high-strength projects, such as large bridges and tunnels.

[0004] In recent years, with the continuous changes and progress in the requirements of building functions and appearance, more and more buildings have used fair-faced concrete, such as building structural components with large structure (or formwork) size, complex shape and high requirements for appearance. This requires that the concrete not only have the performance of fair-faced concrete, but also meet the construction process requirements of high-throw and vibration-free compaction.

[0005] Therefore, there is a need to develop a high-throw, vibration-free fair-faced concrete. Summary of the Invention

[0006] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. To this end, the present invention provides a fair-faced concrete that, while meeting the appearance requirements of fair-faced concrete, also meets the construction requirements of high-polish self-compacting concrete (possessing good fluidity and anti-segregation properties).

[0007] The present invention also provides a method for preparing fair-faced concrete.

[0008] The present invention also provides a precast concrete component.

[0009] A first aspect of the present invention provides fair-faced concrete, comprising, by weight:

[0010] Cementitious material: 350-410 parts;

[0011] Coarse aggregate: 900-1000 parts;

[0012] Fine aggregate: 800-1000 parts;

[0013] Compound admixture: 7 to 10 parts;

[0014] Water: 140-180 parts

[0015] The compound additive is a mixture of four-carbon mother liquor, six-carbon mother liquor, polyvinyl alcohol water-retaining agent, ether-based defoamer, and workability regulator.

[0016] One of the technical solutions of this invention concerning fair-faced concrete has at least the following beneficial effects:

[0017] The fair-faced concrete of this invention not only meets the appearance requirements of fair-faced concrete, but also meets the construction requirements of high-spread self-compacting concrete (with good fluidity and anti-segregation performance). For special requirements such as high appearance quality, complex formwork, and dense rebar spacing, it makes full use of the material characteristics of fair-faced concrete with smooth and flat surface and the construction characteristics of high-spread self-compacting concrete, which can simplify the construction process such as vibration, plastering, and decoration, and has significant economic benefits.

[0018] In the fair-faced concrete of this invention:

[0019] Cementitious materials are the main component of concrete, playing a role in bonding and hardening. Cement reacts chemically with water to form a cementitious matrix, which binds the aggregate together to form a strong concrete structure. During the reaction, cement gradually hydrates and solidifies, giving the concrete sufficient strength and durability.

[0020] Coarse aggregates serve to fill voids and provide mechanical strength. They provide the main skeleton of concrete and its ability to bear loads. Coarse aggregates can also increase the crack resistance of concrete and contribute to its durability.

[0021] Fine aggregates primarily fill the voids between cementitious materials and coarse aggregates, increasing the fluidity and workability of concrete. Their role is to regulate the paste properties of concrete and reduce shrinkage. Fine aggregates can also increase the surface smoothness of concrete and reduce the occurrence of internal cracks.

[0022] The main function of compound admixtures is to improve the workability of concrete materials, specifically including: improving its fluidity at a low water-cement ratio; providing sufficient adhesion during high-layout construction to prevent segregation and stratification; and eliminating air bubbles introduced during mixing and flow (which may affect the appearance quality of fair-faced concrete).

[0023] In compound admixtures:

[0024] Four-carbon mother liquor refers to four-carbon unsaturated isomeric alcohol polyether, which belongs to water-reducing agents.

[0025] Hexacarbon mother liquor refers to hexacarbon unsaturated isomeric alcohol polyether, which belongs to water-reducing agents.

[0026] Polyvinyl alcohol water-retaining agent refers to polyvinyl alcohol.

[0027] Ether-based defoamers include at least one of phenethyl ether, dimethyl ether, and n-butyl ether.

[0028] Workability modifiers include phosphate thickeners. Specifically, they include at least one of potassium dihydrogen phosphate and disodium phosphate.

[0029] In this invention, "high throw" refers to a height greater than 3m, which is greater than the conventional height.

[0030] According to some embodiments of the present invention, fair-faced concrete, by weight, comprises:

[0031] Cementitious material: 380 parts;

[0032] Coarse aggregate: 950 parts;

[0033] Fine aggregate: 900 parts;

[0034] Compound admixture: 8 parts;

[0035] Water: 160 portions.

[0036] According to some embodiments of the present invention, the mass ratio of the four-carbon mother liquor, the six-carbon mother liquor, the polyvinyl alcohol water-retaining agent, the ether-based defoamer, and the workability regulator is 8-12:8-12:2-4:1:1.

[0037] According to some embodiments of the present invention, the mass ratio of the four-carbon mother liquor, the six-carbon mother liquor, the polyvinyl alcohol water-retaining agent, the ether-based defoamer, and the workability regulator is 10:10:3:1:1.

[0038] According to some embodiments of the present invention, the cementing material includes at least one of cement, mineral powder, fly ash and silica fume.

[0039] The fly ash in the cementitious material should be of grade II or above, with a 45μm sieve residue of 25±3%, uniform color, loss on ignition ≤2.0%, and water requirement ≤95%.

[0040] The mineral powder in the cementitious material is of grade S95, and is pure white, uniform, and stable in color.

[0041] According to some embodiments of the present invention, the fine aggregate has a fineness modulus of 2.6 to 2.7, an MB value of <1.0, and a powder content of ≤10%.

[0042] According to some embodiments of the present invention, the apparent density ρ of coarse aggregate G Apparent density ρ of fine aggregate S Equivalent density ρ of cementitious materials B The following relationships satisfy the following: a) the mass fraction of coarse aggregate in total aggregate; b) the mass fraction of fine aggregate in total aggregate; c) the mass fraction of fine aggregate in the total mass of fine aggregate and binder; and d) the mass fraction of cementitious materials in the total mass of fine aggregate and binder: ρ S / (ρ G ×a+ρ S ×b) is 1.00~1.05, ρ B / (ρ S ×c+ρ B ×d) is 1.10~1.15.

[0043] Concrete is a mixture of stone, sand, cementitious materials, water, etc., and the particle size and density of each material vary considerably. This invention controls the density difference between various individual substances or mixtures by controlling the ratio of sand density to the equivalent density of the sand-stone mixture, and the ratio of the equivalent density of the cementitious material (powder) to the sand-cement mixture. This control of the ratios prevents the mixture from settling and stratifying.

[0044] Equivalent density ρ of cementitious materials B The weighted density of cement, mineral powder, fly ash, and silica fume, calculated by mass.

[0045] The mass fraction of coarse aggregate in the total aggregate, a = mass of coarse aggregate / (mass of coarse aggregate + mass of fine aggregate).

[0046] The mass fraction of fine aggregate in the total aggregate, b = mass of fine aggregate / (mass of coarse aggregate + mass of fine aggregate).

[0047] The mass fraction of fine aggregate in the total mass of fine aggregate and cementitious material is c = mass of fine aggregate / (mass of fine aggregate + mass of cementitious material).

[0048] The mass fraction of cementitious materials in the total mass of fine aggregates and cementitious materials, d = mass of cementitious materials / (mass of fine aggregates + mass of cementitious materials).

[0049] According to some embodiments of the present invention, the ρ G ρ S ρ B The following relationship exists between a, b, c, and d: ρ S / (ρ G ×a+ρ S ×b) is 1.03~1.05, ρ B / (ρ S ×c+ρ B ×d) is 1.10 to 1.13.

[0050] A second aspect of the present invention provides a method for preparing fair-faced concrete, comprising the following steps:

[0051] The cementitious material, the coarse aggregate, and the fine aggregate are mixed evenly to obtain a mixture.

[0052] The compound additive is mixed with some or all of the water, and then divided into at least one portion and added to the mixture for stirring.

[0053] One technical solution of the present invention relating to the preparation method of fair-faced concrete has at least the following beneficial effects:

[0054] The preparation method of the present invention is simple, uses readily available raw materials, has low production costs, and is easy to industrialize.

[0055] According to some embodiments of the present invention, the stirring method includes: stirring twice or more using a forced mixer, wherein the interval time is not less than 30 seconds.

[0056] A third aspect of the present invention provides a precast concrete component prepared from the fair-faced concrete of the present invention.

[0057] One of the technical solutions of the present invention concerning precast concrete components has at least the following beneficial effects:

[0058] Precast components are concrete members manufactured in a factory or prefabrication site. They are prefabricated according to specific design requirements and specifications and then transported to the site for installation. Precast components prepared using the fair-faced concrete of this invention have at least the following beneficial effects:

[0059] In terms of appearance quality, precast components made of fair-faced concrete can meet high requirements for aesthetic quality. Because fair-faced concrete uses fewer additives and pigments, its surface can present a smooth, flat, and uniform appearance. Therefore, precast components made of fair-faced concrete are suitable for projects with high aesthetic requirements, such as building facades and landscape decorations.

[0060] In terms of fluidity and segregation resistance, precast components made with fair-faced concrete exhibit excellent fluidity and segregation resistance. The appropriate amount of cement and high-quality aggregate in fair-faced concrete contributes to its good fluidity, making the molding of precast components smoother. Simultaneously, the mix proportions and construction techniques of fair-faced concrete effectively prevent segregation, ensuring the consistency and quality of the precast components.

[0061] In terms of simplifying the construction process, the precast components made of fair-faced concrete have a smooth and flat surface and inherent self-compacting properties, eliminating the need for traditional construction vibration and finishing during installation. This simplifies the construction process, reduces labor and time costs, and improves construction efficiency. Furthermore, to meet special requirements, such as complex structural shapes and dense rebar spacing, precast components can be precisely processed in the factory, ensuring accuracy and consistency.

[0062] In terms of economic benefits, using precast components made from fair-faced concrete offers significant advantages. Due to factory manufacturing and standardized production, the production cost of precast components is relatively low. Furthermore, the high quality and accuracy of precast components reduce waste and repair work during construction, thereby reducing the overall project cost.

[0063] Therefore, precast components made from fair-faced concrete offer advantages such as high appearance quality, good fluidity, strong anti-segregation properties, simplified construction process, and significant economic benefits. This makes them an ideal choice for projects requiring high aesthetic appeal and specialized construction techniques, such as building facades, landscaping, complex formwork, and densely spaced rebar. Detailed Implementation

[0064] The following are specific embodiments of the present invention, and the technical solutions of the present invention will be further described in conjunction with the embodiments, but the present invention is not limited to these embodiments.

[0065] In some embodiments of the present invention, the present invention provides fair-faced concrete, comprising, by weight:

[0066] Cementitious material: 350-410 parts;

[0067] Coarse aggregate: 900-1000 parts;

[0068] Fine aggregate: 800-1000 parts;

[0069] Compound admixture: 7 to 10 parts;

[0070] Water: 140-180 parts

[0071] The compound additives are a mixture of four-carbon mother liquor, six-carbon mother liquor, polyvinyl alcohol water-retaining agent, ether-based defoamer, and workability regulator.

[0072] It is understood that the fair-faced concrete of the present invention, while meeting the appearance requirements of fair-faced concrete, can also meet the construction requirements of high-polish self-compacting concrete (with good fluidity and anti-segregation performance). For special requirements such as high appearance quality, complex formwork, and dense rebar spacing, it makes full use of the material characteristics of smooth and flat fair-faced concrete surface and the construction characteristics of high-polish self-compacting concrete, which can simplify the construction process such as vibration, plastering, and decoration, and has significant economic benefits.

[0073] In the fair-faced concrete of this invention:

[0074] Cementitious materials are the main component of concrete, playing a role in bonding and hardening. Cement reacts chemically with water to form a cementitious matrix, which binds the aggregate together to form a strong concrete structure. During the reaction, cement gradually hydrates and solidifies, giving the concrete sufficient strength and durability.

[0075] Coarse aggregates serve to fill voids and provide mechanical strength. They provide the main skeleton of concrete and its ability to bear loads. Coarse aggregates can also increase the crack resistance of concrete and contribute to its durability.

[0076] Fine aggregates primarily fill the voids between cementitious materials and coarse aggregates, increasing the fluidity and workability of concrete. Their role is to regulate the paste properties of concrete and reduce shrinkage. Fine aggregates can also increase the surface smoothness of concrete and reduce the occurrence of internal cracks.

[0077] The main function of compound admixtures is to improve the workability of concrete materials, specifically including: improving its fluidity at a low water-cement ratio; providing sufficient adhesion during high-layout construction to prevent segregation and stratification; and eliminating air bubbles introduced during mixing and flow (which may affect the appearance quality of fair-faced concrete).

[0078] In compound admixtures:

[0079] Four-carbon mother liquor refers to four-carbon unsaturated isomeric alcohol polyether, which belongs to water-reducing agents.

[0080] Hexacarbon mother liquor refers to hexacarbon unsaturated isomeric alcohol polyether, which belongs to water-reducing agents.

[0081] Polyvinyl alcohol water-retaining agent refers to polyvinyl alcohol.

[0082] Ether-based defoamers include at least one of phenethyl ether, dimethyl ether, and n-butyl ether.

[0083] Workability modifiers include phosphate thickeners. Specifically, they include at least one of potassium dihydrogen phosphate and disodium phosphate.

[0084] In this invention, "high throw" refers to a height greater than 3m, which is greater than the conventional height.

[0085] In some embodiments of the present invention, the fair-faced concrete, by weight, comprises:

[0086] Cementitious material: 380 parts;

[0087] Coarse aggregate: 950 parts;

[0088] Fine aggregate: 900 parts;

[0089] Compound admixture: 8 parts;

[0090] Water: 160 portions.

[0091] In some embodiments of the present invention, the mass ratio of the four-carbon mother liquor, the six-carbon mother liquor, the polyvinyl alcohol water-retaining agent, the ether-based defoamer, and the workability regulator is 8-12:8-12:2-4:1:1.

[0092] In some embodiments of the present invention, the mass ratio of the four-carbon mother liquor, the six-carbon mother liquor, the polyvinyl alcohol water-retaining agent, the ether-based defoamer, and the workability regulator is 10:10:3:1:1.

[0093] In some embodiments of the present invention, the cementing material includes at least one of cement, mineral powder, fly ash, and silica fume.

[0094] The fly ash in the cementitious material should be of grade II or above, with a 45μm sieve residue of 25±3%, uniform color, loss on ignition ≤2.0%, and water requirement ≤95%.

[0095] The mineral powder in the cementitious material is of grade S95, and is pure white, uniform, and stable in color.

[0096] In some embodiments of the present invention, the fineness modulus of the fine aggregate is 2.6 to 2.7, the MB value is <1.0, and the powder content is ≤10%.

[0097] In some embodiments of the present invention, the apparent density ρ of coarse aggregate is... G Apparent density ρ of fine aggregate S Equivalent density ρ of cementitious materials B The following relationships satisfy the following: a) the mass fraction of coarse aggregate in total aggregate; b) the mass fraction of fine aggregate in total aggregate; c) the mass fraction of fine aggregate in the total mass of fine aggregate and binder; and d) the mass fraction of cementitious materials in the total mass of fine aggregate and binder: ρS / (ρ G ×a+ρ S ×b) is 1.00~1.05, ρ B / (ρ S ×c+ρ B ×d) is 1.10~1.15.

[0098] Concrete is a mixture of stone, sand, cementitious materials, water, etc., and the particle size and density of each material vary considerably. This invention controls the density difference between various individual substances or mixtures by controlling the ratio of sand density to the equivalent density of the sand-stone mixture, and the ratio of the equivalent density of the cementitious material (powder) to the sand-cement mixture. This control of the ratios prevents the mixture from settling and stratifying.

[0099] Equivalent density ρ of cementitious materials B The weighted density of cement, mineral powder, fly ash, and silica fume, calculated by mass.

[0100] The mass fraction of coarse aggregate in the total aggregate, a = mass of coarse aggregate / (mass of coarse aggregate + mass of fine aggregate).

[0101] The mass fraction of fine aggregate in the total aggregate, b = mass of fine aggregate / (mass of coarse aggregate + mass of fine aggregate).

[0102] The mass fraction of fine aggregate in the total mass of fine aggregate and cementitious material is c = mass of fine aggregate / (mass of fine aggregate + mass of cementitious material).

[0103] The mass fraction of cementitious materials in the total mass of fine aggregates and cementitious materials, d = mass of cementitious materials / (mass of fine aggregates + mass of cementitious materials).

[0104] In some embodiments of the present invention, ρ G ρ S ρ B The following relationship exists between a, b, c, and d: ρ S / (ρ G ×a+ρ S ×b) is 1.03~1.05, ρ B / (ρ S ×c+ρ B ×d) is 1.10 to 1.13.

[0105] In other embodiments of the present invention, a method for preparing fair-faced concrete is provided, comprising the following steps:

[0106] Mix the cementitious materials, coarse aggregates, and fine aggregates evenly to obtain a mixture;

[0107] After mixing the compound additive with some or all of the water, divide it into at least one portion and add it to the mixture while stirring.

[0108] It is understood that the preparation method of the present invention is simple, the raw materials are readily available, the production cost is low, and it is easy to industrialize.

[0109] In some embodiments of the present invention, the stirring method includes: stirring twice or more using a forced mixer, wherein the interval time is not less than 30 seconds.

[0110] In some other embodiments of the present invention, the present invention provides a precast concrete component prepared from the fair-faced concrete of the present invention.

[0111] It is understood that precast components are concrete members manufactured in a factory or prefabrication site. They are prefabricated according to specific design requirements and specifications, and then transported to the site for installation. Precast components prepared using the fair-faced concrete of this invention have at least the following beneficial effects:

[0112] In terms of appearance quality, precast components made of fair-faced concrete can meet high requirements for aesthetic quality. Because fair-faced concrete uses fewer additives and pigments, its surface can present a smooth, flat, and uniform appearance. Therefore, precast components made of fair-faced concrete are suitable for projects with high aesthetic requirements, such as building facades and landscape decorations.

[0113] In terms of fluidity and segregation resistance, precast components made with fair-faced concrete exhibit excellent fluidity and segregation resistance. The appropriate amount of cement and high-quality aggregate in fair-faced concrete contributes to its good fluidity, making the molding of precast components smoother. Simultaneously, the mix proportions and construction techniques of fair-faced concrete effectively prevent segregation, ensuring the consistency and quality of the precast components.

[0114] In terms of simplifying the construction process, the precast components made of fair-faced concrete have a smooth and flat surface and inherent self-compacting properties, eliminating the need for traditional construction vibration and finishing during installation. This simplifies the construction process, reduces labor and time costs, and improves construction efficiency. Furthermore, to meet special requirements, such as complex structural shapes and dense rebar spacing, precast components can be precisely processed in the factory, ensuring accuracy and consistency.

[0115] In terms of economic benefits, using precast components made from fair-faced concrete offers significant advantages. Due to factory manufacturing and standardized production, the production cost of precast components is relatively low. Furthermore, the high quality and accuracy of precast components reduce waste and repair work during construction, thereby reducing the overall project cost.

[0116] Therefore, precast components made from fair-faced concrete offer advantages such as high appearance quality, good fluidity, strong anti-segregation properties, simplified construction process, and significant economic benefits. This makes them an ideal choice for projects requiring high aesthetic appeal and specialized construction techniques, such as building facades, landscaping, complex formwork, and densely spaced rebar.

[0117] The technical solution of the present invention will be better understood below with reference to specific embodiments and comparative examples.

[0118] In the examples and comparative examples:

[0119] Ordinary Portland cement was purchased from Shuangfeng Conch Cement.

[0120] Grade II fly ash was purchased from Yiyang Xingtai;

[0121] S90 mineral powder was purchased from Fanyi Xianggang;

[0122] The coarse aggregate was purchased from Chenglin, Taojiang.

[0123] The fine aggregate was purchased from Hunan Jukaixin;

[0124] The C4 and C6 mother liquors are produced by China Construction Western Construction New Materials Technology Co., Ltd.

[0125] Polyvinyl alcohol water-retaining agent, ether-based defoamer, and workability modifier were purchased from Shanghai WaiDian International Trade Co., Ltd.

[0126] The concrete prepared in the embodiments (including examples and comparative examples) is all of grade C40.

[0127] Example 1

[0128] A type of fair-faced concrete, by weight, is composed of 380 parts of cementitious materials, 950 parts of coarse aggregate, 900 parts of fine aggregate, 8 parts of compound admixture, and 160 parts of water.

[0129] The cementitious material is composed of cement, mineral powder and fly ash in a ratio of 7:2:1.

[0130] The compound additive is prepared by mixing four-carbon mother liquor, six-carbon mother liquor, polyvinyl alcohol water-retaining agent, ether defoamer, and workability regulator in a ratio of 5:5:1.5:0.5:0.5.

[0131] Where ρ S / (ρ G ×a+ρ S ×b) is 1.03, ρ B / (ρ S ×c+ρ BThe particle size distribution (×d) is 1.12, the fineness modulus of the fine aggregate is 2.6, the MB value is 0.8, the powder content is 7.5%, the fly ash in the cementitious material is grade II, the residue on the 45μm sieve is 26%, the color is uniform, the loss on ignition is 0.8%, the water requirement ratio is 90%, and the mineral powder in the cementitious material is grade S95, with a pure white color that is uniform and stable.

[0132] The specific preparation method is as follows:

[0133] Mix the cementitious materials, coarse aggregates, and fine aggregates evenly to obtain a mixture;

[0134] After mixing the compound additive with some or all of the water, divide it into at least one portion and add it to the mixture while stirring.

[0135] The high-strength, vibration-free fair-faced concrete is obtained by mixing with a forced mixer for 30 seconds, pausing for 30 seconds, and then mixing for 20 seconds.

[0136] Forced mixers are vibratory mixers.

[0137] Example 2

[0138] A type of fair-faced concrete, by weight, is composed of 390 parts of cementitious materials, 920 parts of coarse aggregate, 890 parts of fine aggregate, 9 parts of compound admixture, and 170 parts of water.

[0139] The cementitious material is composed of cement, mineral powder and fly ash in a ratio of 7:2:1.

[0140] The compound additive is prepared by mixing four-carbon mother liquor, six-carbon mother liquor, polyvinyl alcohol water-retaining agent, ether defoamer, and workability regulator in a ratio of 6:5:1.5:0.5:0.5.

[0141] Where ρ S / (ρ G ×a+ρ S ×b) is 1.05, ρ B / (ρ S ×c+ρ B The particle size distribution (×d) is 1.12, the fineness modulus of the fine aggregate is 2.7, the MB value is 0.8, the powder content is 8.5%, the fly ash in the cementitious material is grade II, the residue on the 45μm sieve is 24%, the color is uniform, the loss on ignition is 0.6%, the water requirement ratio is 88%, and the mineral powder in the cementitious material is grade S95, with a pure white color that is uniform and stable.

[0142] The specific preparation method is as follows:

[0143] Mix the cementitious materials, coarse aggregates, and fine aggregates evenly to obtain a mixture;

[0144] After mixing the compound additive with some or all of the water, divide it into at least one portion and add it to the mixture while stirring.

[0145] The high-strength, vibration-free fair-faced concrete is obtained by mixing with a forced mixer for 30 seconds, pausing for 30 seconds, and then mixing for 20 seconds.

[0146] Forced mixers are vibratory mixers.

[0147] Comparative Example 1

[0148] Except for the compound additives being prepared in the ratio of C4 mother liquor, C6 mother liquor, polyvinyl alcohol water-retaining agent, ether defoamer, and workability regulator in a ratio of 3:5:0.5:0.5:0.5, everything else is the same as in Example 1.

[0149] Comparative Example 2

[0150] Except for the compound additives being prepared in the ratio of C4 mother liquor, C6 mother liquor, polyvinyl alcohol water-retaining agent, ether defoamer, and workability regulator in a ratio of 3:5:0.5:0.7:0.3, everything else is the same as in Example 1.

[0151] Comparative Example 3

[0152] Except for raw material parameter ρ S / (ρ G ×a+ρ S ×b) is 1.05, ρ B / (ρ S ×c+ρ B The value of ×d) is 1.20, and everything else is the same as in Example 1.

[0153] Comparative Example 4

[0154] Except for raw material parameter ρ S / (ρ G ×a+ρ S ×b) is 1.10, ρ B / (ρ S ×c+ρ B The value of ×d) is 1.13, and everything else is the same as in Example 1.

[0155] Performance testing

[0156] To evaluate the performance of the concrete prepared in Examples 1-2 and Comparative Examples 1-4 of this invention, specimens were prepared and cured, and relevant indicators were tested, in accordance with JGJ / T283-2012 "Technical Specification for Application of Self-Compacting Concrete" and GB / T50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete". The test results are shown in Table 1.

[0157] Table 1

[0158]

[0159]

[0160] As can be seen from Table 1, the concrete of Examples 1 and 2 implemented according to the technical solution of the present invention has good mechanical properties (compressive strength), workability (slump spread, spread time T500, difference between slump spread and J-ring spread), segregation resistance (segregation rate), and self-compacting properties (U-shaped box height difference). While meeting the appearance requirements of fair-faced concrete, it can also meet the construction requirements of high-splash self-compacting concrete.

[0161] Comparative Examples 1 and 2 showed a decline in workability and anti-segregation performance due to changes in the compound additive formulation.

[0162] Compared with Examples 3 and 4, due to the large density difference between the raw materials and the mixture, the anti-segregation performance decreased, and the segregation phenomenon was more likely to occur, which could not meet the construction requirements of high-throw self-compacting without vibration.

[0163] The present invention has been described in detail above with reference to the embodiments. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A type of fair-faced concrete, characterized in that, The components, by weight, include: Cementitious material: 350-410 parts; Coarse aggregate: 900-1000 parts; Fine aggregate: 800-1000 parts; Compound admixture: 7 to 10 parts; Water: 140-180 parts The compound additive is a mixture of four-carbon mother liquor, six-carbon mother liquor, polyvinyl alcohol water-retaining agent, ether-based defoamer, and workability regulator; Four-carbon mother liquor refers to four-carbon unsaturated isomeric alcohol polyether, which belongs to water-reducing agents; Hexacarbon mother liquor refers to hexacarbon unsaturated isomeric alcohol polyether, which belongs to water-reducing agents; The ether-based defoamer is at least one of phenethyl ether, dimethyl ether, and n-butyl ether, and the workability regulator is at least one of potassium dihydrogen phosphate and disodium phosphate. The mass ratio of the four-carbon mother liquor, six-carbon mother liquor, polyvinyl alcohol water-retaining agent, ether defoamer, and workability regulator is 8-12:8-12:2-4:1:1; apparent density ρ of coarse aggregate G Apparent density ρ of fine aggregate S Equivalent density ρ of cementitious materials B The following relationships satisfy the following: a) the mass fraction of coarse aggregate in total aggregate; b) the mass fraction of fine aggregate in total aggregate; c) the mass fraction of fine aggregate in the total mass of fine aggregate and binder; and d) the mass fraction of cementitious materials in the total mass of fine aggregate and binder: ρ S / (ρ G ×a+ρ S ×b) is 1.00~1.05, ρ B / (ρ S ×c+ρ B The effective density ρ of the cementitious material is 1.10 to 1.15 (×d). B The weighted density of cement, mineral powder, fly ash, and silica fume, calculated by mass.

2. The fair-faced concrete according to claim 1, characterized in that, The mass ratio of the four-carbon mother liquor, six-carbon mother liquor, polyvinyl alcohol water-retaining agent, ether-based defoamer, and workability regulator is 10:10:3:1:

1.

3. The fair-faced concrete according to claim 1, characterized in that, The fine aggregate has a fineness modulus of 2.6 to 2.7, an MB value of <1.0, and a powder content of ≤10%.

4. The fair-faced concrete according to claim 1, characterized in that, The ρ G ρ S ρ B The following relationships exist between a, b, c, and d: ρ S / (ρ G ×a+ρ S ×b) is 1.03~1.05, ρ B / (ρ S ×c+ρ B ×d) is 1.10 to 1.

13.

5. A method for preparing fair-faced concrete as described in any one of claims 1 to 4, characterized in that, Includes the following steps: The cementitious material, the coarse aggregate, and the fine aggregate are mixed evenly to obtain a mixture; The compound additive is mixed with some or all of the water, and then divided into at least one portion and added to the mixture for stirring.

6. The method according to claim 5, characterized in that, The mixing method includes: mixing twice or more using a forced mixer, with an interval of not less than 30 seconds between each mixing.

7. A precast concrete component, characterized in that, It is prepared from any one of claims 1 to 4.

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