A mix design method for C55 concrete with machine-made sand and fluctuating stone powder content

Abstract

The present invention discloses a mix design method for C55 concrete with machine-made sand and stone powder content fluctuations. The method limits the fluctuation range of the stone powder content of machine-made sand for C55 concrete, and then designs the admixture components based on the average stone powder content of the machine-made sand and its corresponding sand ratio; and determines the mix design parameters of machine-made sand concrete with the lowest stone powder content. The present invention uses the lowest stone powder content of machine-made sand as a benchmark to calculate and determine the corresponding sand ratio of machine-made sand concrete with on-site stone powder content and the mix design parameters of on-site machine-made sand concrete. The present invention minimizes the adverse effects of the fluctuation of the stone powder content of machine-made sand on the working performance of concrete while minimizing the fluctuation of the total stone powder content introduced by machine-made sand in a single cubic meter of concrete, solves the technical problem of the incompatibility between admixtures and machine-made sand with stone powder content fluctuations, and provides a new design method for the mix design of C55 concrete with machine-made sand with stone powder content fluctuations.

Description

Technical Field

[0001] The invention relates to the technical field of building materials, and in particular to a mix ratio design method for C55 concrete with machine-made sand and fluctuating stone powder content. Background Art

[0002] Under the background of environmental protection, the replacement of river sand by machine-made sand has become an inevitable trend in the development of concrete materials. Machine-made sand is a kind of artificial sand prepared by processes such as coarse crushing-prescreening-medium crushing-sand making-screening and washing. Due to the different selection of sand making equipment, the stone powder content in the produced machine-made sand fluctuates greatly, which will cause the incompatibility between the stone powder content fluctuation and the admixture and have an adverse effect on the working performance of concrete. Therefore, the "Technical Specifications for the Application of Artificial Sand Concrete" JGJ / T 241 standard stipulates that the maximum stone powder content of machine-made sand for C55 concrete is 7.0 when MB < 1.4 (qualified); 3.0 when MB ≥ 1.4 (unqualified). MB < 1.4 (qualified) indicates that fine particles with a nominal particle size of less than 80 μm are all stone powder with the same mineral composition and chemical composition as the processed parent rock; MB ≥ 1.4 (unqualified) indicates that fine particles with a nominal particle size of less than 80 μm contain some mud in addition to stone powder.

[0003] At present, in view of the adverse effects of machine-made sand with large fluctuation of stone powder content on the initial slump and slump loss control of C55 concrete, some scholars have proposed to design concrete mix proportions by using anti-mud polycarboxylic acid water reducer or mud inhibitor technology, trying to solve the compatibility problem between admixtures and the mechanism of stone powder content fluctuation, but the effect is not significant. Other scholars have proposed a mix design method of increasing unit water consumption to reduce the adverse effects of stone powder content fluctuation on concrete working performance, but this will cause the increase of cementitious materials and bring the risk of concrete cracking. The study found that although the stone powder in machine-made sand has an adverse effect on the fluidity of concrete, it can improve the cohesion of concrete. When the sand ratio is high, the fluidity of concrete deteriorates due to the high stone powder content; when the sand ratio is low, the encapsulation of concrete deteriorates due to the low stone powder content. Therefore, by reasonably selecting the stone powder content and its corresponding sand ratio and designing the admixture components, the mix proportion design of C55 machine-made sand concrete with stone powder content fluctuation is carried out to solve the incompatibility between admixtures and machine-made sand with stone powder content fluctuation. Summary of the invention

[0004] In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a method for designing the mix ratio of C55 concrete with machine-made sand and stone powder content fluctuation, which can solve the problem of incompatibility between the fluctuation of stone powder content in concrete and admixtures.

[0005] The purpose of the present invention is achieved by the following technical solutions:

[0006] A method for designing a mix ratio of C55 concrete with fluctuating stone powder content and machine-made sand, comprising the following steps:

[0007] Step (1) limits the range of fluctuation of the content of machine-made sand and gravel powder for C55 concrete, requiring:

[0008] When MB value is less than 1.4, the content of machine-made sand and gravel powder fluctuates from 1.0% to 7.0%;

[0009] When MB value is ≥1.4, the content of machine-made sand and gravel powder fluctuates from 1.0% to 3.0%;

[0010] Step (2), taking the machine-made sand and stone powder content of 1% as the benchmark, determining the corresponding sand ratio of the machine-made sand C55 concrete under different machine-made sand and stone powder contents, designing the admixture components according to the corresponding sand ratio of the machine-made sand C55 concrete with an average stone powder content, and finally calculating and determining the mix design parameters of the machine-made sand C55 concrete with a stone powder content of 1% by the mass method;

[0011] Step (3), testing and determining the on-site machine-made sand and gravel powder content n%, taking the machine-made sand and gravel powder content of 1% as the benchmark, calculating the corresponding sand ratio of the on-site machine-made sand C55 concrete, and then calculating the on-site machine-made sand C55 concrete mix ratio design parameters according to the corresponding sand ratio of the on-site machine-made sand C55 concrete, and completing a stone powder content fluctuation machine-made sand C55 concrete mix ratio design.

[0012] Furthermore, in the step (2), based on the content of 1% of the machine-made sand and stone powder, the method for determining the corresponding sand ratio of the machine-made sand C55 concrete is as follows:

[0013] First, the corresponding sand ratio β of C55 concrete with 1% artificial sand is determined by the artificial sand fineness modulus. s Then, the corresponding sand ratio β of machine-made sand C55 concrete under the corresponding stone powder content is calculated by the method that the sand ratio decreases by 1% when the stone powder content increases by 1%. / s .

[0014] Furthermore, in step (2), according to the average stone powder content, the corresponding sand ratio β of the machine-made sand C55 concrete / / s , with β / / s As a benchmark, design the admixture components.

[0015] Furthermore, in the step (2), the mass method is used to calculate and determine the mix ratio design parameters of the benchmark machine-made sand concrete with a stone powder content of 1% as follows:

[0016] Cement dosage m c0 , fly ash dosage m f0 、Mineral powder dosage m k0, Sand dosage m s0 , Stone dosage m g0 , water consumption m w0 、Amount of admixture m a0 .

[0017] Furthermore, in step (3), the calculation method of the corresponding sand ratio of the on-site machine-made sand C55 concrete is:

[0018] Taking the machine-made sand and stone powder content of 1% as the benchmark, the corresponding sand rate when the on-site machine-made sand and stone powder content is n% is calculated according to the method that the sand rate decreases by 1% for every 1% increase in the stone powder content. The calculation formula for the corresponding sand rate of the on-site machine-made sand C55 concrete is β s / =β s -(n-1)%;

[0019] The β s The corresponding sand ratio of C55 concrete with artificial sand and stone powder content of 1% is determined for the artificial sand fineness modulus.

[0020] Furthermore, in step (3), the mix design parameters of the on-site machine-made sand C55 concrete are:

[0021] Cement dosage m / c0 =m c0 , fly ash dosage m / f0 =m f0 、Mineral powder dosage m / k0 =m k0 , Sand dosage m / s0 =β / s ×(m s0 +m g0 ), Stone dosage m / g0 =(m s0 +m g0 -m / s0 ), water consumption m / w0 =m w0 、Amount of admixture m / a0 =m a0 .

[0022] Furthermore, in the step (2), the principle is to minimize the fluctuation of the stone powder content of a single cubic meter of concrete, and the method is as follows:

[0023] When MB is less than 1.4, the highest corresponding sand ratio is taken when the content of machine-made sand and gravel powder is 1.0%, and the lowest corresponding sand ratio is taken when the content of machine-made sand and gravel powder is 7.0%;

[0024] When MB≥1.4, the highest corresponding sand ratio is taken when the content of machine-made sand and gravel powder is 1.0%, and the lowest corresponding sand ratio is taken when the content of machine-made sand and gravel powder is 3.0%.

[0025] Furthermore, the content of the machine-made sand and gravel powder is determined using the JGJ 52 test method of the Standard for Quality and Inspection Methods of Sand and Stone for Ordinary Concrete.

[0026] Furthermore, in the step (2), the method of determining the sand ratio corresponding to the stone powder content of 1% by the machine-made sand fineness modulus, and the method of selecting the design parameters of the machine-made sand concrete mix ratio under the benchmark condition of 1% stone powder content, both adopt the provisions of the "Ordinary Concrete Mix Ratio Design Code" JGJ 55.

[0027] Furthermore, in step (2), each thousand parts of the admixture includes the following mass components:

[0028] 280-330 parts of polycarboxylic acid water-reducing masterbatch with a solid content of 40%, 200-260 parts of polycarboxylic acid collapse-preventing masterbatch with a solid content of 40%, 10-20 parts of sodium gluconate, 10-20 parts of white sugar, 0.2-0.3 parts of sodium dodecylbenzene sulfonate, 0.2-0.4 parts of warm wheel glue, 0.15-0.26 parts of silicone defoaming agent, and the rest is water.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. The present invention provides a method for designing a mix ratio of C55 concrete with artificial sand and stone powder content fluctuation, which can dynamically adjust the sand ratio of concrete according to the fluctuation of artificial sand and stone powder content, so as to minimize the fluctuation of total stone powder content introduced by artificial sand in a single cubic meter of concrete, thereby minimizing the adverse effect of the fluctuation of artificial sand and stone powder content on the working performance of concrete.

[0031] 2. The method for designing the mix ratio of C55 concrete with machine-made sand and fluctuating stone powder content of the present invention also includes an admixture component designed according to the average content of machine-made sand and stone powder and its corresponding sand ratio, and timely fine-adjusts the mix ratio of concrete according to the actual stone powder content of the machine-made sand, so that the admixture has good adaptability to the machine-made sand with fluctuating stone powder content, and at the same time, the advantages of stone powder in improving the encapsulation and water retention of concrete can be brought into play. DETAILED DESCRIPTION

[0032] The technical solution of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only partial embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0033] The raw materials used in the following Examples 1 to 2 are: cement is P.Ⅱ42.5R cement produced by Yingde Conch Co., Ltd.; fly ash is Class F Class I ash produced by Shenhua Guangdong Guohua Taishan Power Generation Co., Ltd.; mineral powder is S95 mineral powder produced by Tangshan Caofeidian Dunshi New Building Materials Co., Ltd.; machine-made sand is two types of sand provided by Jiangmen Xinhui District Biyuan Building Materials Co., Ltd.: when the fineness modulus is 2.9 and MB is less than 1.4, the stone powder content fluctuates in the range of 1.0% to 7.0%; when the fineness modulus is 2.8 and MB≥1.4, the stone powder content fluctuates in the range of 1.0% to 3.0%; coarse aggregate is 5 to 20 mm continuously graded crushed stone produced by Gucheng Mining Development Investment Co., Ltd.; polycarboxylic acid water reducer is compounded and designed according to the average stone powder content of machine-made sand and its corresponding sand ratio, and is provided by Guangdong Qiangshi Building Materials Technology Co., Ltd.; mixing water is groundwater.

[0034] Below, in conjunction with specific implementation modes, the present invention is further described:

[0035] Example 1

[0036] Taking strength grade C55, initial slump 220mm, 2h slump retention value 200mm machine-made sand concrete as an example, the concrete mix design is carried out according to the following steps:

[0037] (1) According to the test method of JGJ 52 of the Standard for Quality and Inspection Methods of Sand and Stone for Ordinary Concrete, the machine-made sand is tested and determined: when MB is less than 1.4, the fluctuation range of stone powder content is 1.0% to 7.0%;

[0038] (2) Based on the 1% artificial sand and stone powder content, determine the corresponding sand ratio of C55 artificial sand concrete: First, determine the corresponding sand ratio β of 1% stone powder content according to the "Ordinary Concrete Mix Design Code" JGJ 55 based on the artificial sand fineness modulus 2.9. s =42%, and then the sand ratio β corresponding to the average stone powder content of 4% is calculated by the method that the sand ratio decreases by 1% when the stone powder content increases by 1%. / / s =39%;

[0039] The average stone powder content of machine-made sand is 4% and its corresponding sand ratio β / / s39% is taken as the benchmark, and the designed admixture components (water reduction rate is 30% when the dosage is 1.0%) include, by thousand parts by mass: 330 parts of polycarboxylic acid water-reducing masterbatch with solid content of 40%, 200 parts of polycarboxylic acid collapse-preserving masterbatch with solid content of 40%, 10 parts of sodium gluconate, 20 parts of white sugar, 0.2 parts of sodium dodecylbenzene sulfonate, 0.4 parts of Wenlun glue, 0.26 parts of silicone defoamer, and the rest is water;

[0040] (3) Then, taking the artificial sand and stone powder content of 1% and its corresponding sand ratio of 42% as the benchmark, and in accordance with the provisions of the "Ordinary Concrete Mix Design Code" JGJ 55 (wherein the fly ash content is 27% and the mineral powder content is 17%), the mass method is used to calculate the design parameters of the artificial sand concrete mix ratio with a stone powder content of 1%: cement content m c0 285kg, fly ash dosage m f0 140kg, mineral powder dosage m k0 85kg, sand consumption m s0 734kg, stone consumption m g0 1013kg, water consumption m w0 153kg, admixture dosage (i.e. total dosage of compound admixture components) m a0 When the actual powder content of machine-made sand is 7.0%, the sand ratio corresponding to the stone powder content of 7.0% is 36% according to the method that the sand ratio decreases by 1% for every 1% increase in the stone powder content. Then the mix ratio design parameters of machine-made sand concrete are calculated: cement dosage m / c0 285kg, fly ash dosage m / f0 140kg, mineral powder dosage m / k0 85kg, sand consumption m / s0 629kg, stone consumption m / g0 1118kg, water consumption m / w0 153kg, admixture dosage m / a0 is 1.0%.

[0041] The mix ratio, working performance and strength test results of the machine-made sand concrete of Example 1 are shown in Tables 1 and 2.

[0042] Example 2

[0043] Taking strength grade C55, initial slump 220mm, 2h slump retention value 200mm machine-made sand concrete as an example, the concrete mix design is carried out according to the following steps:

[0044] (1) According to the test method of JGJ 52 of the Standard for Quality and Inspection Methods of Sand and Stone for Ordinary Concrete, the machine-made sand is tested and determined: when MB ≥ 1.4, the fluctuation range of stone powder content is 1.0% to 3.0%;

[0045] (2) Based on the 1% content of manufactured sand and stone powder, determine the corresponding sand ratio of C55 manufactured sand concrete: First, determine the sand ratio β corresponding to 1% stone powder content according to the "Ordinary Concrete Mix Design Code" JGJ 55 based on the fineness modulus of manufactured sand of 2.8. s =41%, and then the sand ratio β corresponding to the average stone powder content of 2% is calculated by the method that the sand ratio decreases by 1% when the stone powder content increases by 1%. / / s =40%;

[0046] The average stone powder content of machine-made sand is 2% and its corresponding sand ratio β / / s 40% is taken as the benchmark, and the designed admixture components (water reduction rate is 28% when the dosage is 1.0%) include, by thousand parts by mass: 280 parts of polycarboxylic acid water-reducing masterbatch with solid content of 40%, 260 parts of polycarboxylic acid collapse-preserving masterbatch with solid content of 40%, 20 parts of sodium gluconate, 10 parts of white sugar, 0.3 parts of sodium dodecylbenzene sulfonate, 0.2 parts of Wenlun glue, 0.15 parts of silicone defoamer, and the rest is water;

[0047] (3) Then, taking the artificial sand and stone powder content of 1% and its corresponding sand ratio of 41% as the benchmark, and in accordance with the provisions of the "Ordinary Concrete Mix Design Code" JGJ 55 (wherein the fly ash content is 27% and the mineral powder content is 17%), the mass method is used to calculate the design parameters of the artificial sand concrete mix ratio with a stone powder content of 1%: cement content m c0 285kg, fly ash dosage m f0 140kg, mineral powder dosage m k0 85kg, sand consumption m s0 716kg, stone consumption m g0 1031kg, water consumption m w0 153kg, admixture dosage (i.e. total dosage of compound admixture components) m a0 When the actual powder content of machine-made sand is 3.0%, the sand ratio corresponding to the stone powder content of 3.0% is calculated to be 39% according to the method that the sand ratio decreases by 1% for every 1% increase in the stone powder content. Then the mix ratio design parameters of the machine-made sand concrete are calculated: cement dosage m / c0 285kg, fly ash dosage m / f0 140kg, mineral powder dosage m / k0 85kg, sand consumption m / s0 681kg, stone consumption m / g0 1066kg, water consumption m / w0 153kg, admixture dosage m / a0 is 1.0%.

[0048] The mix ratio, working performance and strength test results of the machine-made sand concrete of Example 2 are shown in Tables 1 and 2.

[0049] Table 1C55 machine-made sand concrete mix ratio

[0050]

[0051] Table 2 Working performance and strength of machine-made sand concrete

[0052]

[0053] Examples 1 and 2 show that for machine-made sand with fluctuating stone powder content that meets the standard, the mix design method of the present invention can effectively solve the incompatibility problem between admixtures and machine-made sand with fluctuating stone powder content, and the concrete strength meets the C55 strength grade requirement, which has certain technical and economic rationality and significant social and economic benefits.

[0054] Comparative Example 3

[0055] Taking strength grade C55, initial slump 220mm, 2h slump retention value 200mm machine-made sand concrete as an example, the concrete mix design is carried out according to the following steps:

[0056] (1) According to the test method of JGJ 52 of the Standard for Quality and Inspection Methods of Sand and Stone for Ordinary Concrete, the machine-made sand is tested and determined: when MB is less than 1.4, the fluctuation range of stone powder content is 1.0% to 7.0%;

[0057] (2) According to the fineness modulus of machine-made sand of 2.9, the sand ratio corresponding to the stone powder content of 1.0% is determined as β according to the provisions of the "Ordinary Concrete Mix Design Code" JGJ 55. s =42%, the designed admixture components (water reduction rate of 27% when the dosage is 1.0%) include, by thousand parts by mass: 290 parts of polycarboxylic acid water-reducing masterbatch with a solid content of 40%, 210 parts of polycarboxylic acid collapse-preventing masterbatch with a solid content of 40%, 15 parts of sodium gluconate, 15 parts of white sugar, 0.2 parts of sodium dodecylbenzene sulfonate, 0.25 parts of Wenlun glue, 0.2 parts of organic silicon defoaming agent, and the rest is water. According to the provisions of "Ordinary Concrete Mix Design Code" JGJ 55 (including 27% fly ash and 17% mineral powder), the mass method is used to calculate the design parameters of the machine-made sand concrete mix ratio with a stone powder content fluctuation range of 1.0% to 7.0%: cement dosage mc0 285kg, fly ash dosage m f0 140kg, mineral powder dosage m k0 85kg, sand consumption m s0 734kg, stone consumption m g0 1013kg, water consumption m w0 153kg, admixture dosage (i.e. total dosage of compound admixture components) m a0 is 1.0%.

[0058] The mix proportion and working performance of C55 machine-made sand concrete of Comparative Example 3 are shown in Tables 3 and 4.

[0059] Table 3C55 machine-made sand concrete mix ratio

[0060]

[0061] Table 4 Working performance of C55 machine-made sand concrete

[0062]

[0063] It can be seen from Comparative Example 3 that: for the machine-made sand with fluctuating stone powder content, the concrete sand ratio is not adjusted accordingly according to the fluctuation of the actual stone powder content of the machine-made sand, and the admixture components are not designed based on the average stone powder content of the machine-made sand and its corresponding sand ratio, which will cause serious incompatibility between the admixture and the machine-made sand, making it extremely difficult to control the initial slump and slump loss of C55 machine-made sand concrete.

[0064] For those skilled in the art, various other corresponding changes and deformations can be made according to the technical solutions and concepts described above, and all of these changes and deformations should fall within the protection scope of the claims of the present invention.

Claims

1. A method for designing the mix ratio of C55 concrete with fluctuating stone powder content machine-made sand, characterized in that: The following steps are involved: Step (1) limits the range of fluctuation of the content of machine-made sand and gravel powder for C55 concrete, requiring: When the fineness modulus is 2.9 and the MB value is less than 1.4, the content of machine-made sand and gravel powder fluctuates from 1.0% to 7.0%; When the fineness modulus is 2.8 and the MB value is ≥1.4, the content of machine-made sand and gravel powder fluctuates within the range of 1.0% to 3.0%; Step (2): first determine the corresponding sand ratio β of C55 concrete with 1% stone powder content by the fineness modulus of the machine-made sand. s , as the benchmark, and then the corresponding sand ratio β of machine-made sand C55 concrete under the corresponding stone powder content is calculated by the method that the sand ratio decreases by 1% when the stone powder content increases by 1%. / s ; According to the average stone powder content, the corresponding sand ratio of C55 concrete is β / / s Based on the above, the admixture components are designed. Every thousand parts of admixture includes the following mass components: 280-330 parts of polycarboxylic acid water-reducing masterbatch with a solid content of 40%, 200-260 parts of polycarboxylic acid collapse-preserving masterbatch with a solid content of 40%, 10-20 parts of sodium gluconate, 10-20 parts of white sugar, 0.2-0.3 parts of sodium dodecylbenzene sulfonate, 0.2-0.4 parts of warm wheel glue, 0.15-0.26 parts of silicone defoamer, and the rest is water; Finally, the mass method was used to calculate the design parameters of the C55 concrete mix ratio with a stone powder content of 1% as follows: cement dosage m c0 , fly ash dosage m f0 、Mineral powder dosage m k0 , Sand dosage m s0 , Stone dosage m g0 , water consumption m w0 、Amount of admixture m a0 ; Step (3), test and determine the on-site machine-made sand and gravel content n%, take the machine-made sand and gravel content 1% as the benchmark, and calculate the corresponding sand rate of the on-site machine-made sand C55 concrete when the stone powder content is n% according to the method that the sand rate decreases by 1% for every 1% increase in the stone powder content. The calculation formula for the corresponding sand rate of the on-site machine-made sand C55 concrete is β / s =β s -(n-1)%, the β s Determine the corresponding sand ratio of C55 concrete with 1% stone powder content for the fineness modulus of manufactured sand; Calculate the mix design parameters of C55 concrete with on-site machine-made sand. The mix design parameters of C55 concrete with on-site machine-made sand are: Cement dosage m / c0 =m c0 , fly ash dosage m / f0 =m f0 、Mineral powder dosage m / k0 =m k0 , Sand dosage m / s0 =β / s ×(m s0 +m g0 ), Stone dosage m / g0 =(m s0 +m g0 -m / s0 ), water consumption m / w0 =m w0 、Amount of admixture m / a0 =m a0 , completed the mix design of C55 concrete with fluctuating stone powder content and machine-made sand.

2. The method for designing the mix ratio of C55 concrete with fluctuating stone powder content according to claim 1 is characterized in that: In the step (2), the principle is to minimize the fluctuation of the stone powder content in a single cubic meter of concrete, and the method is as follows: When MB is less than 1.4, the highest corresponding sand ratio is taken when the content of machine-made sand and gravel powder is 1.0%, and the lowest corresponding sand ratio is taken when the content of machine-made sand and gravel powder is 7.0%; When MB≥1.4, the highest corresponding sand ratio is taken when the content of machine-made sand and gravel powder is 1.0%, and the lowest corresponding sand ratio is taken when the content of machine-made sand and gravel powder is 3.0%.

3. A method for designing a mix ratio of C55 concrete with fluctuating stone powder content according to claim 1 or 2, characterized in that: The content of the machine-made sand and gravel powder is determined using the JGJ52 test method of the Standard for Quality and Inspection Methods of Sand and Stone for Ordinary Concrete.

4. The method for designing the mix ratio of C55 concrete with fluctuating stone powder content according to claim 1 is characterized in that: In the step (2), the method of determining the sand ratio corresponding to 1% stone powder content by the machine-made sand fineness modulus, and the method of selecting the design parameters of the machine-made sand concrete mix ratio under the benchmark condition of 1% stone powder content, both adopt the provisions of "Ordinary Concrete Mix Ratio Design Code" JGJ 55.

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