A Mix Proportion Design and Preparation Method for Manufactured Sand Concrete

Abstract

The present invention discloses a method for designing and preparing the mix proportion of manufactured-sand concrete, which relates to the technical field of building material preparation. According to the linear regression linear equation of the compressive strength with different replacement rates of manufactured sand, the total amount of cementitious materials and the water-cementitious materials ratio are calculated; the amounts of fine and coarse aggregates with a set sand ratio are calculated; according to the dosages of fly ash and slag powder, the dosages of fly ash, slag powder and cement are calculated to obtain the recommended mix proportion meeting the strength requirements and the recommended mix proportion meeting the durability requirements; the 28-day chloride ion diffusion coefficient of the concrete meeting the engineering durability requirements is calculated; the 28-day chloride ion diffusion coefficient of the concrete is normalized; and in combination with the chloride ion diffusion coefficient equation, the total amount of cementitious materials and the water-cementitious materials ratio are calculated; by combining the recommended mix proportion meeting the strength requirements and the recommended mix proportion meeting the durability requirements, the optimal recommended mix proportion of manufactured-sand concrete for each strength grade is obtained. The present invention can obtain the best mix proportion of manufactured-sand concrete that simultaneously meets various performance indicators.

Description

Technical Field

[0001] The present invention relates to the technical field of building material preparation, and particularly to a mix proportion design and preparation method for manufactured sand concrete. Background Art

[0002] Currently, the design of the mix proportion of manufactured sand concrete mainly still refers to the mix proportion design of ordinary concrete in the "Code for Mix Proportion Design of Ordinary Concrete" JGJ55-2011, including: the preliminary calculated mix proportion, the determination of the reference mix proportion, the determination of the laboratory mix proportion, and the determination of the construction mix proportion. However, there is stone powder in the manufactured sand, which will affect the strength and durability of the concrete, etc., and thus affect the calculation of the mix proportion. Research shows that starting from the perspective of the dual-constraint control of the water-cement ratio and the water-powder ratio to control the performance of high-performance manufactured sand concrete, the integrated design of stone-sand-powder can effectively solve the influence of parameters such as manufactured sand on the workability and strength of the concrete. However, this method mainly uses strength as the control index for the mix proportion design of manufactured sand concrete, and the calculation process is relatively complex. For the mix proportion design with impermeability requirements, it is not specified, that is, this method cannot use quantitative durability indicators as the basis for the mix proportion design of manufactured sand concrete. Summary of the Invention

[0003] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a mix proportion design and preparation method for manufactured sand concrete with a simple calculation. Based on the strength and durability requirements of manufactured sand concrete, the mix proportion design process of manufactured sand concrete is optimized, and the best mix proportion of manufactured sand concrete that can simultaneously meet various performance indicators can be obtained.

[0004] To achieve the above purpose, the present invention is realized through the following technical solutions:

[0005] In the first aspect, an embodiment of the present invention provides a mix proportion design method for manufactured sand concrete, including:

[0006] Calculating the total amount of cementitious materials and the water-cement ratio according to the concrete preparation strength and the linear regression linear equation of the compressive strength with different manufactured sand replacement rates;

[0007] Calculating the amounts of coarse and fine aggregates with a set sand ratio based on the sum of coarse and fine aggregates; calculating the amounts of fly ash, slag powder, and cement according to the dosages of fly ash and slag powder, and obtaining the recommended mix proportion that meets the strength requirements and the recommended mix proportion that meets the durability requirements;

[0008] Calculating the 28-day chloride ion diffusion coefficient of the concrete that meets the engineering durability requirements; normalizing the 28-day chloride ion diffusion coefficient of the concrete through the normalized limit values of the chloride ion diffusion coefficients of each strength grade of concrete; and combining with the chloride ion diffusion coefficient equation, calculating the total amount of cementitious materials and the water-cement ratio;

[0009] According to the regulations of the glue ratio and the dosage of cementitious materials satisfied by concrete of different strength grades, combined with the recommended mix ratios that meet the strength requirements and the recommended mix ratios that meet the durability requirements, the optimal recommended mix ratios of manufactured-sand concrete for each strength grade are obtained.

[0010] As a further implementation method, when the designed strength grade is less than C60,

[0011] ;

[0012] wherein, f cu,o is the concrete preparation strength, f cu,k is the standard value of the cube compressive strength of concrete, σ is the standard deviation of concrete strength.

[0013] As a further implementation method, the amounts of coarse and fine aggregates are calculated according to the sand ratio range of 38% - 42%, and the optimal sand ratio is 40%.

[0014] As a further implementation method, the amounts of each material are calculated according to the proportion of mineral admixtures required in the actual project. Among them, the optimal dosages of fly ash and slag powder designed by this method are 30% and 15%.

[0015] As a further implementation method, the method for normalizing the 28-day chloride diffusion coefficient that meets the requirements is:

[0016] ;

[0017] wherein, D 28 is the normalized 28-day chloride diffusion coefficient of concrete, D m is the normalized value of the chloride diffusion coefficient of concrete, D is the 28-day chloride diffusion coefficient of concrete that meets the requirements.

[0018] As a further implementation method, for different concrete strength grades, the value ranges of the 28-day chloride diffusion coefficient of concrete are different.

[0019] As a further implementation method, the linear relationship equations between the 28-day chloride diffusion coefficient of concrete and the manufactured-sand replacement rate, W / B are:

[0020] ① When the manufactured-sand replacement rate is 0: ;

[0021] ② When the manufactured-sand replacement rate is not 0: ;

[0022] Among them, the value range of a is 0.4038 - 0.4464, the value range of b is 0.7025 - 0.7766, the value range of c is 0.0027 - 0.0031, the value range of d is 0.3066 - 0.3389, and the value range of e is 0.5597 - 0.6186;

[0023] r 1 is the replacement rate of manufactured sand, W / B is the glue ratio, B is the total amount of binder.

[0024] The linear relationship equation between the chloride ion diffusion coefficient of concrete at 28 d and the replacement rate of manufactured sand and the binder dosage is:

[0025] ① When the replacement rate of manufactured sand is 0: ;

[0026] ② When the replacement rate of manufactured sand is not 0: ;

[0027] Among them, the value range of f is 0.0003 - 0.0004, the value range of g is 1.0027 - 1.1083, the value range of m is 0.0026 - 0.0029, the value range of n is 0.0003 - 0.0004, and the value range of s is 0.8267 - 0.9138.

[0028] As a further implementation method, the replacement rate of manufactured sand is 0 - 100%, the glue ratio is 0.33 - 0.5, and the total amount of binder is 300 kg / m 3 - 500 kg / m 3 .

[0029] In the second aspect, the embodiments of the present invention also provide a method for preparing manufactured sand concrete. According to the above design method, the optimal recommended mix proportion of manufactured sand concrete is obtained, and manufactured sand concrete is obtained after mixing raw materials.

[0030] As a further implementation method, the strength grade of the manufactured sand concrete is C30 - C50.

[0031] The beneficial effects of the present invention are as follows:

[0032] (1) Different from the cumbersome design method of traditional concrete mix proportion, the present invention is based on the compressive strength of manufactured sand concrete and the chloride ion diffusion coefficient at 28 d that meet the engineering requirements, and can respectively calculate the mix proportion of manufactured sand concrete that meets the strength and durability requirements; finally, the best mix proportion of manufactured sand concrete that meets various performance indicators is obtained in combination with the specification requirements.

[0033] (2) The present invention gives the linear relationships between the chloride ion diffusion coefficient of concrete at 28 days and the replacement rate of manufactured sand and W / B, as well as the linear relationships between the chloride ion diffusion coefficient of concrete at 28 days and the replacement rate of manufactured sand and the amount of binder. An accurate mix proportion of manufactured sand concrete can be obtained, and the mix proportion design process of manufactured sand concrete is optimized. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The attached drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0035] Figure 1 It is a diagram showing the linear regression analysis of the compressive strength data of manufactured sand concrete under different replacement rates of manufactured sand according to one or more embodiments of the present invention; Figure 1 In (a), it is a relationship diagram between the 28-day strength and the total amount of binder with the serial number 0%M in Table 1, (b) is a relationship diagram between the 28-day strength and the water-binder ratio with the serial number 0%M in Table 1, (c) is a relationship diagram between the 28-day strength and the total amount of binder with 25%M in Table 1, (d) is a relationship diagram between the 28-day strength and the water-binder ratio with 25%M in Table 1, (e) is a relationship diagram between the 28-day strength and the total amount of binder with 50%M in Table 1, and (f) is a relationship diagram between the 28-day strength and the water-binder ratio with 50%M in Table 1;

[0036] Figure 2 It is a diagram showing the relationship between different concretes D 28 of the present invention and the replacement rate of manufactured sand and W / B;

[0037] Figure 3 It is a diagram showing the relationship between different concretes D28 and the replacement rate of manufactured sand and the total amount of binder according to one or more embodiments of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0039] Example 1:

[0040] This example provides a method for designing the mix proportion of manufactured sand concrete, including the following steps:

[0041] 1) According to the provisions of the "Code for Design of Mix Proportion of Ordinary Concrete" JGJ55-2011, calculate the concrete strength that meets the engineering requirements f cu,o When the designed strength grade is less than C60, the specific calculation method is as shown in Equation (1):

[0042] (1)

[0043] In the formula: f cu,o is the concrete mixing strength, MPa; f cu,k is the standard value of the cube compressive strength of concrete. Here, the design strength grade value of concrete is taken, MPa; σ is the standard deviation of concrete strength, MPa.

[0044] 2) Substitute the f cu,o in step 1) into the linear regression linear equation of the compressive strength with different replacement ratios of manufactured sand as shown in Figure 1 to calculate the total amount of cementitious materials and the water-cement ratio, as shown in Table 1:

[0045] Table 1 Compressive strength data of manufactured sand concrete with different replacement ratios of manufactured sand

[0046]

[0047] 3) Calculate the total amount of coarse and fine aggregates according to the mass method, and then calculate the amounts of coarse and fine aggregates according to a sand ratio of 40%. In addition, according to the admixture amounts of fly ash and slag powder being 30% and 15%, the amounts of fly ash, slag powder, and cement can be calculated, so as to obtain the recommended mix proportion that meets the strength requirements.

[0048] Among them, the mass method is a method for calculating the amounts of coarse and fine aggregates based on the assumption that the mass of each cubic meter of concrete mixture is a certain fixed value.

[0049] 4) According to the provisions of the "Standard for Durability Design of Concrete Structures" GBT 50476-2019, the 28-day chloride ion diffusion coefficient ( D ) of concrete that meets the engineering durability requirements can be obtained. However, there are limitations on the water-cement ratio and the amount of cementitious materials in the linear relationship equation of this embodiment. Therefore, D has a limited value range, and the specific value range is shown in Table 2:

[0050] Table 2 Value range of 28-day chloride ion diffusion coefficient of concrete with different strength grades

[0051]

[0052] 5) Through the normalized limit values of the chloride ion diffusion coefficients of concrete with each strength grade, normalize the 28-day chloride ion diffusion coefficient that meets the requirements in step 4). The specific calculation method is as shown in formula (2):

[0053] (2)

[0054] In formula (2): D 28 is the normalized chloride ion diffusion coefficient of concrete at 28 days (10 -12 m 2 / s); D m is the normalized value of the chloride ion diffusion coefficient of concrete (specifically refer to Table 3, 10 -12 m 2 / s); D is the chloride ion diffusion coefficient of concrete at 28 days that meets the requirements (10 -12 m 2 / s). The chloride ion diffusion coefficient of concrete at 28 days is an important index for evaluating the chloride ion penetration resistance of concrete.

[0055] Table 3 Limiting values of normalized chloride ion diffusion coefficients of concrete under different strength grades

[0056]

[0057] 6) As shown in Figure 2 and Figure 3 , substitute the D 28 in step 5) into the linear relationship equation between the chloride ion diffusion coefficient of concrete at 28 days, the replacement rate of manufactured sand, and W / B (or the amount of binder) (chloride ion diffusion coefficient equation) to calculate the total amount of binder and the water-binder ratio. The specific calculation methods are as shown in formulas (3), (4), (5), and (6):

[0058] (3)

[0059] (4)

[0060] (5)

[0061] (6)

[0062] In the formulas: the value range of a is 0.4038 - 0.4464, the value range of b is 0.7025 - 0.7766, the value range of c is 0.0027 - 0.0031, the value range of d is 0.3066 - 0.3389, the value range of e is 0.5597 - 0.6186, the value range of f is 0.0003 - 0.0004, the value range of g is 1.0027 - 1.1083, the value range of m is 0.0026 - 0.0029, the value range of n is 0.0003 - 0.0004, and the value range of s is 0.8267 - 0.9138; D28 is the normalized chloride ion diffusion coefficient of concrete at 28 days (10 -12 m 2 / s); r 1 is the replacement rate of manufactured sand (0 - 100%); W / B is the glue ratio (0.33 - 0.53); B is the total amount of binder (300 kg / m 3 - 500 kg / m 3 ).

[0063] 7) Calculate the dosage of each material according to the method in step 3) to obtain the recommended mix proportion that meets the durability requirements.

[0064] 8) According to the "Code for Durability Design of Highway Concrete" JTG / T 3310, the concrete of different strength grades should meet the specified values of glue ratio and binder dosage (as shown in Table 4). Combining the mix proportions in step 3) and step 7), obtain the optimal recommended mix proportion of manufactured sand concrete for each strength grade.

[0065] Table 4 Maximum glue ratio and binder dosage of concrete with different strength grades (kg / m 3 )

[0066]

[0067] In this embodiment, the fine aggregate used is manufactured sand with a fineness modulus of 3.13 and a stone powder content of 5%; the cement used is P·O42.5 cement; the mineral admixtures used are S95 grade blast furnace slag powder and Class F fly ash of Grade I.

[0068] This embodiment is different from the traditional complicated design method of concrete mix proportion. It can calculate the recommended mix proportion of manufactured sand concrete by obtaining the compressive strength that meets the engineering requirements, and can also calculate the recommended mix proportion of manufactured sand concrete by obtaining the 28-day chloride ion diffusion coefficient that meets the requirements, optimizing the mix proportion design process of manufactured sand concrete.

[0069] Example 2:

[0070] This embodiment provides a method for preparing manufactured sand concrete. According to the design method described in Example 1, obtain the optimal recommended mix proportion of manufactured sand concrete, and obtain manufactured sand concrete after mixing the raw materials.

[0071] Among them, the strength grade of manufactured sand concrete is C30 - C50.

[0072] Example 3:

[0073] Based on the design method described in Embodiment 1, in this embodiment, it is assumed that the mix proportion of C40 manufactured-sand concrete is designed according to the compressive strength, and the specific calculation method is as follows:

[0074] (1) Calculate according to Equation 1 f cu,o = 48.225 MPa;

[0075] (2) Substitute f cu,o = 48.225 MPa into the linear regression linear equation of the compressive strength with different manufactured-sand replacement ratios as shown in Figure 1 to calculate the total amount of cementitious materials and the water-cement ratio, as shown in Table 1:

[0076] ① The total amount of cementitious materials with a replacement ratio of 0% is 452.44 kg / m 3 , and the water-cement ratio is 2.75;

[0077] ② The total amount of cementitious materials with a replacement ratio of 25% is 408.47 kg / m 3 , and the water-cement ratio is 2.45;

[0078] ③ The total amount of cementitious materials with a replacement ratio of 50% is 343.43 kg / m 3 , and the water-cement ratio is 2.15;

[0079] ④ The total amount of cementitious materials with a replacement ratio of 75% is 364.7 kg / m 3 , and the water-cement ratio is 2.26;

[0080] ⑤ The total amount of cementitious materials with a replacement ratio of 100% is 423.17 kg / m 3 , and the water-cement ratio is 2.52.

[0081] (3) Assume that the apparent density of the concrete is 2400 kg / m 3 , the sand ratio is 40%, and the dosages of fly ash and slag powder are 30% and 15% respectively. Using the mass method in the "Code for Design of Mix Proportions of Ordinary Concrete" JGJ55-2011, calculate the dosages of each material as follows:

[0082] ① The cement dosage with a replacement ratio of 0% is 248.84 kg / m 3 , the fly ash dosage is 135.73 kg / m 3 , the slag powder dosage is 67.87 kg / m 3 , the fine aggregate dosage is 713.46 kg / m 3 , the coarse aggregate dosage is 1069.74 kg / m 3 , and the water dosage is 164.36 kg / m 3 ;

[0083] ② When the replacement rate is 25%, the cement dosage is 224.66 kg / m 3 , the fly ash dosage is 122.54 kg / m 3 , the slag powder dosage is 61.27 kg / m 3 , the fine aggregate dosage is 729.92 kg / m 3 , the coarse aggregate dosage is 1094.89 kg / m 3 , the water dosage is 166.72 kg / m 3 ;

[0084] ③ When the replacement rate is 50%, the cement dosage is 188.89 kg / m 3 , the fly ash dosage is 103.03 kg / m 3 , the slag powder dosage is 51.51 kg / m 3 , the fine aggregate dosage is 758.74 kg / m 3 , the coarse aggregate dosage is 1138.1 kg / m 3 , the water dosage is 159.73 kg / m 3 ;

[0085] ④ When the replacement rate is 75%, the cement dosage is 200.58 kg / m 3 , the fly ash dosage is 109.41 kg / m 3 , the slag powder dosage is 54.71 kg / m 3 , the fine aggregate dosage is 749.57 kg / m 3 , the coarse aggregate dosage is 1124.36 kg / m 3 , the water dosage is 161.37 kg / m 3 ;

[0086] ⑤ When the replacement rate is 100%, the cement dosage is 232.74 kg / m 3 , the fly ash dosage is 126.95 kg / m 3 , the slag powder dosage is 63.48 kg / m 3 , the fine aggregate dosage is 723.56 kg / m 3 , the coarse aggregate dosage is 1085.35 kg / m 3 , the water dosage is 167.92 kg / m 3 .

[0087] (4) It can be known from the provisions in the "Standard for Durability Design of Concrete Structures" GBT 50476-2019 that for concrete with a designed service life of 100 years and a service environment of Ⅲ-D, the 28-day chloride ion diffusion coefficient of the concrete should be 7×10 -12 m 2 / s. Assume that for a certain project, the chloride ion diffusion coefficient of C40 concrete at 28 days is 2.5×10 -12 m 2 / s. According to Equation (2), the normalized chloride ion diffusion coefficient of the concrete at 28 days is calculated as D 28 =0.85×10 -12 m 2 / s;

[0088] (5) Substitute D 28 into the linear relationship equation between the chloride ion diffusion coefficient of the concrete at 28 days, the replacement rate of manufactured sand, and W / B (or the amount of binder) to calculate:

[0089] ① The total amount of binder with a replacement rate of 0% is 394 kg / m 3 , and the water-binder ratio is 0.44;

[0090] ② The total amount of binder with a replacement rate of 25% is 395 kg / m 3 , and the water-binder ratio is 0.44;

[0091] ③ The total amount of binder with a replacement rate of 50% is 396 kg / m 3 , and the water-binder ratio is 0.44;

[0092] ④ The total amount of binder with a replacement rate of 75% is 397 kg / m 3 , and the water-binder ratio is 0.44;

[0093] ⑤ The total amount of binder with a replacement rate of 100% is 398 kg / m 3 , and the water-binder ratio is 0.44.

[0094] (6) Assume that the apparent density of the concrete is 2400 kg / m 3 , the sand ratio is 40%, and the dosages of fly ash and slag powder are 30% and 15% respectively. Using the mass method in the "Code for Design of Mix Proportions of Ordinary Concrete" JGJ55-2011, the dosages of each material are calculated as follows:

[0095] ① The cement dosage with a replacement rate of 0% is 217 kg / m 3 , the fly ash dosage is 118 kg / m 3 , the slag powder dosage is 59 kg / m 3 , the fine aggregate dosage is 733 kg / m 3 , the coarse aggregate dosage is 1099.5 kg / m 3 , and the water dosage is 173.5 kg / m 3 ;

[0096] ② The cement dosage with a substitution rate of 25% is 217 kg / m 3 , the fly ash dosage is 119 kg / m 3 , the slag powder dosage is 59 kg / m 3 , the fine aggregate dosage is 732.57 kg / m 3 , the coarse aggregate dosage is 1098.87 kg / m 3 , the water dosage is 173.56 kg / m 3 ;

[0097] ③ The cement dosage with a substitution rate of 50% is 218 kg / m 3 , the fly ash dosage is 119 kg / m 3 , the slag powder dosage is 59 kg / m 3 , the fine aggregate dosage is 732.16 kg / m 3 , the coarse aggregate dosage is 1098.24 kg / m 3 , the water dosage is 173.63 kg / m 3 ;

[0098] ④ The cement dosage with a substitution rate of 75% is 218 kg / m 3 , the fly ash dosage is 119 kg / m 3 , the slag powder dosage is 60 kg / m 3 , the fine aggregate dosage is 731.73 kg / m 3 , the coarse aggregate dosage is 1097.6 kg / m 3 , the water dosage is 173.69 kg / m 3 ;

[0099] ⑤ The cement dosage with a substitution rate of 100% is 219 kg / m 3 , the fly ash dosage is 119 kg / m 3 , the slag powder dosage is 60 kg / m 3 , the fine aggregate dosage is 731.32 kg / m 3 , the coarse aggregate dosage is 1096.68 kg / m 3 , the water dosage is 173.76 kg / m 3 .

[0100] (7) According to the requirements of "Code for Durability Design of Highway Concrete" JTG / T 3310, the concrete with different strength grades should meet the specified values of the water-binder ratio and the binder dosage (see Table 4 for details). Combining the above mix ratio and the economic cost of the mixing plant, the optimal recommended mix ratio of C40 manufactured sand concrete is:

[0101] ① The cement dosage with a substitution rate of 0% is 217 kg / m 3, the dosage of fly ash is 118 kg / m 3 , the dosage of slag powder is 59 kg / m 3 , the dosage of fine aggregate is 733 kg / m 3 , the dosage of coarse aggregate is 1099.5 kg / m 3 , the dosage of water is 173.5 kg / m 3 ;

[0102] ② For a replacement rate of 25%, the dosage of cement is 217 kg / m 3 , the dosage of fly ash is 119 kg / m 3 , the dosage of slag powder is 59 kg / m 3 , the dosage of fine aggregate is 732.57 kg / m 3 , the dosage of coarse aggregate is 1098.87 kg / m 3 , the dosage of water is 173.56 kg / m 3 ;

[0103] ③ For a replacement rate of 50%, the dosage of cement is 188.89 kg / m 3 , the dosage of fly ash is 103.03 kg / m 3 , the dosage of slag powder is 51.51 kg / m 3 , the dosage of fine aggregate is 758.74 kg / m 3 , the dosage of coarse aggregate is 1138.1 kg / m 3 , the dosage of water is 159.73 kg / m 3 ;

[0104] ④ For a replacement rate of 75%, the dosage of cement is 218 kg / m 3 , the dosage of fly ash is 119 kg / m 3 , the dosage of slag powder is 60 kg / m 3 , the dosage of fine aggregate is 731.73 kg / m 3 , the dosage of coarse aggregate is 1097.6 kg / m 3 , the dosage of water is 173.69 kg / m 3 ;

[0105] ⑤ For a replacement rate of 100%, the dosage of cement is 219 kg / m 3 , the dosage of fly ash is 119 kg / m 3 , the dosage of slag powder is 60 kg / m 3 , the dosage of fine aggregate is 731.32 kg / m 3 , the dosage of coarse aggregate is 1096.68 kg / m 3 , the dosage of water is 173.76 kg / m 3 。

[0106] The above are only the preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A method for designing mix proportion of machine-made sand concrete, characterized in that: include: A linear regression equation of cementitious material dosage, cementitious-water ratio and compressive strength under different machine-made sand replacement rates was given. The total amount of cementitious material and cementitious-water ratio were calculated based on the concrete mix strength and the linear regression equation of compressive strength under different machine-made sand replacement rates. The amount of coarse and fine aggregates for setting the sand ratio is calculated based on the sum of coarse and fine aggregates; the amount of fly ash, mineral powder and cement is calculated based on the amount of fly ash and mineral powder added to obtain the recommended mix ratio that meets the strength requirements and the recommended mix ratio that meets the durability requirements; Calculate the 28d chloride ion diffusion coefficient of concrete that meets engineering durability requirements; The 28d chloride diffusion coefficient of concrete is normalized by the limit value of chloride diffusion coefficient of concrete of each strength grade; and the total amount of cementitious materials and water-cement ratio are calculated by combining the chloride diffusion coefficient equation. According to the specified values ​​of water-binder ratio and cementitious material dosage of concrete of different strength grades, combined with the recommended mix ratio that meets the strength requirements and the recommended mix ratio that meets the durability requirements, the optimal recommended mix ratio of machine-made sand concrete of each strength grade is obtained; The linear relationship equation between the chloride ion diffusion coefficient of concrete at 28 days, the machine-made sand replacement rate, and W / B is: When the machine-made sand replacement rate is 0: ; When the machine-made sand replacement rate is not 0: ; Among them, a, b, c, d, and e are constants within the set range. r 1 is the replacement rate of machine-made sand, W / B is the water-to-binder ratio, B is the total amount of rubber material; the value range of a is 0.4038-0.4464, the value range of b is 0.7025-0.7766, the value range of c is 0.0027-0.0031, the value range of d is 0.3066-0.3389, and the value range of e is 0.5597-0.6186; The linear relationship equation between the chloride ion diffusion coefficient of concrete at 28 days, the replacement rate of machine-made sand, and the amount of adhesive is: When the machine-made sand replacement rate is 0: ; When the machine-made sand replacement rate is not 0: ; Among them, f, g, m, n, and s are constants with values ​​within the set range; The method for normalizing the 28d chloride ion diffusion coefficient that meets the requirements is: ； in, D 28 is the normalized chloride ion diffusion coefficient of concrete at 28 days, D m is the normalized value of chloride ion diffusion coefficient of concrete, D To meet the requirement of chloride ion diffusion coefficient of concrete at 28 days; For different concrete strength grades, the range of chloride ion diffusion coefficient of concrete at 28 days is different; The replacement rate of machine-made sand is 0-100%, the water-binder ratio is 0.33-0.5, and the total amount of glue is 300kg / m 3 -500kg / m 3 ; The optimal recommended mix ratio of machine-made sand concrete is obtained according to the design method, and the machine-made sand concrete is obtained after mixing the raw materials; The strength grade of the machine-made sand concrete is C30-C50.

2. The method for designing mix ratio of machine-made sand concrete according to claim 1, characterized in that: When the design strength grade is less than C60, ； in, f cu,o To prepare the strength of concrete, f cu,k is the standard value of concrete cube compressive strength, σ is the standard deviation of concrete strength.

3. The method for designing mix ratio of machine-made sand concrete according to claim 1, characterized in that: The amount of coarse and fine aggregate is calculated based on the sand ratio of 38%-42%.

4. A method for preparing machine-made sand concrete, characterized in that: According to the design method described in any one of claims 1 to 3, the optimal recommended mix ratio of machine-made sand concrete is obtained, and the machine-made sand concrete is obtained after mixing the raw materials.

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