A concrete mix proportion design method capable of quantifying the influence of fiber on workability

Abstract

The application discloses a concrete mix proportion design method capable of quantifying the influence of fiber workability, and comprises the following steps: S1, testing the performances of raw materials; S2, calculating the cement paste specific gravity; S3, determining the fiber water absorption rate; S4, calculating the fiber water absorption rate mass caused by fiber water absorption; S5, calculating the cementitious material mass change amount caused by fiber water absorption according to S4; S6, determining the fiber paste thickness; S7, calculating the cement paste mass change amount caused by fiber paste; S8, calculating the cementitious material mass and water mass change amounts caused by fiber paste according to S7; S9, adding the cement, fly ash, water increase amount and fiber amount into the initial mix proportion to obtain the first adjusted mix proportion; S10, adjusting the first adjusted mix proportion to obtain the second adjusted fiber concrete mix proportion; and S11, performing trial mixing according to the mix proportion of step S10, and if the workability of the obtained concrete meets the requirements, the mix proportion meets the requirements.

Description

Technical Field

[0001] This invention belongs to the field of underground engineering technology, specifically relating to a concrete mix design method that can quantify the influence of fibers on workability. Background Technology

[0002] With the increasing maturity of prefabricated tunnel segment application technology, the overall quality requirements for the tunnel segments themselves in lining structures are also becoming increasingly stringent. Ordinary reinforced concrete tunnel segments are gradually revealing a series of problems, including excessive steel consumption, low production efficiency, and brittleness leading to localized breakage. Fiber-reinforced concrete tunnel segments, on the other hand, offer simple construction processes, sufficient load-bearing capacity, and good crack resistance, significantly increasing the workability of the segments while ensuring adequate load-bearing capacity. To meet the different application environments of the tunnel segments, different fiber-reinforced concrete admixtures are required, ranging from 0.5% to 2% by volume. However, variations in admixture will lead to significant changes in the workability of the fiber-reinforced concrete, often resulting in situations where "too much flour requires too much water, and too much water requires too much flour" during production. The main reason is the lack of research on the impact of fiber admixture on concrete workability, and even more so, the lack of a method for calculating the mix proportion of high-admixture fiber-reinforced concrete suitable for tunnel lining segments. Summary of the Invention

[0003] The purpose of this invention is to solve the above-mentioned problems and provide a concrete mix design method that can quantify the effects of fiber water absorption and fiber coating on cement paste, determine the mix proportion of fiber-reinforced concrete, and quantify the influence of fibers on workability.

[0004] To solve the above-mentioned technical problems, the technical solution of the present invention is: a concrete mix design method that can quantify the influence of fibers on workability, which decomposes the influence of fibers on concrete workability into two parts: fiber water absorption and fiber coating, including the following steps:

[0005] S1. Determine the concrete foundation mix proportion and select raw materials according to requirements, and test the various properties of the raw materials;

[0006] S2. Calculate the unit weight of cement paste;

[0007] S3. Determine the fiber water absorption rate;

[0008] S4. Calculate the mass of water absorbed by the fiber due to fiber water absorption;

[0009] m 11 =m1f1

[0010] m1 is the fiber mass, m 11 f1 is the fiber's water absorption mass, and f1 is the fiber's water absorption rate.

[0011] S5. Calculate the change in mass of cementitious material caused by fiber water absorption based on S4.

[0012] S6. Determine the fiber coating thickness;

[0013] V1=S1D1

[0014] V1 is the fiber coating volume, S1 is the total fiber surface area, and D1 is the fiber coating thickness.

[0015] S7. Calculate the change in cement paste mass caused by fiber coating.

[0016] m2=V1γ

[0017] γ is the unit weight of cement paste, V1 is the volume of paste coating, and m2 is the change in cement paste mass caused by fiber coating.

[0018] S8. Calculate the changes in the mass of cementitious materials and water caused by fiber coating according to S7.

[0019] S9. Based on steps S5 and S8, add the increased amounts of cement, fly ash, and water, as well as the actual required amount of fiber, to the initial mix proportion to obtain the first adjusted mix proportion.

[0020] S10. Based on the principle that the mix proportion after the first adjustment is equal to the original mix proportion, the mix proportion after the first adjustment is adjusted accordingly to obtain the actual fiber concrete mix proportion used.

[0021] S11. Conduct a trial mix according to the mix proportion in step S10. If the workability of the concrete obtained from the trial mix meets the requirements, then the mix proportion meets the requirements. If the workability does not meet the requirements, adjust the existing fiber coating thickness and continue from step S6 to step S11 until the workability of the concrete meets the requirements.

[0022] Furthermore, the raw materials in step S1 include: cement, fly ash, sand, gravel, water, water-reducing agent, and fiber;

[0023] M1 = M 11 +M 12 +M 13 +M 14 +M 15 +M 16 ;

[0024] M1 is the mass of the base concrete mix proportion; M 11 For cement quality, M 12 For fly ash quality, M 13 For sand quality, M 14 For the mass of the stones, M 15 For water quality, M 16 The water-reducing agent content is 0, and the fiber content is 0.

[0025] Furthermore, the calculation method in step S2 is as follows:

[0026]

[0027] γ is the unit weight of cement paste, and ρ1 is the density of cement (g / cm³). 3 K represents the water-cement ratio of the concrete.

[0028] Furthermore, step S3 includes the following sub-steps:

[0029] S31. Wipe the fibers clean and weigh W1;

[0030] S32. Take out a certain amount of purified water using a container and soak the fiber in the purified water;

[0031] S33. Remove the fibers, absorb the water from the surface of the fibers with paper towels or towels, and weigh W2.

[0032] S34. Calculate the water absorption rate f1 of the fiber;

[0033]

[0034] Furthermore, the calculation process in step S5 is as follows:

[0035] m 12 =m 11 / K;

[0036]

[0037] m 11 For the water absorption mass of the fiber, m 12 The change in mass of cementitious materials due to water absorption by fibers, K is the water-cement ratio of concrete, and m 121 Change in cement mass caused by fiber water absorption, in m 122 Changes in fly ash mass caused by fiber water absorption.

[0038] Furthermore, the calculation process in step S8 is as follows:

[0039]

[0040] m 21 m represents the change in mass of cementitious materials caused by fiber coating. 211 The change in cement mass caused by fiber coating is expressed in m. 212 The change in fly ash mass caused by fiber coating is expressed in m. 22 K represents the change in water mass caused by fiber coating, and K is the water-cement ratio of the concrete.

[0041] Further, the mixing ratio in step S9 is calculated as follows:

[0042] M 21 =M 11 +m 121 +m 211 ;

[0043] M 22 =M 12 +m 122 +m 212 ;

[0044] M 24 =M 14 +m 11 +m 22 ;

[0045] M2 = M 21 +M 22 +M 23 +M 24 +M 25 +M 26 +M7;

[0046] M2 represents the concrete quality after the first adjustment of the concrete mix proportions. 21 For the cement quality after the first adjustment of the mix proportion, M 22 For the first adjustment of the fly ash mix ratio, M 23 The sand quality after the first adjustment of the mix ratio, M 24 For the first adjustment of the aggregate mix ratio, M 25 For the water quality after the first adjustment of the mix ratio, M 26 M7 represents the mass of the water-reducing agent after the first adjustment of the mixing ratio, and M7 represents the mass of the fiber after the first adjustment of the mixing ratio.

[0047] Further, the mixing ratio in step S10 is calculated as follows:

[0048]

[0049] n = 1 to 6

[0050] Where M 3n To determine the quality of concrete materials after the second adjustment of the mix proportions, M 2n This refers to the quality of concrete materials after the first adjustment of the mix proportions.

[0051] The beneficial effects of this invention are: the concrete mix design method provided by this invention can quantify the influence of fibers on workability, quantifies the influence of fiber water absorption and fiber coating on cement paste, can more rationally determine the mix proportion of fiber-reinforced concrete, solves the workability problem in the production process of fiber-reinforced concrete segments, and thus provides a basis for the production of fiber-reinforced concrete segments. Attached Figure Description

[0052] Figure 1 This is a flowchart of a concrete mix design method that can quantify the influence of fibers on workability according to the present invention; Detailed Implementation

[0053] The present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0054] like Figure 1 As shown, the present invention provides a concrete mix design method that can quantify the influence of fibers on workability, comprising the following steps:

[0055] S1. Determine the concrete foundation mix proportion and select raw materials according to requirements, and test the various properties of the raw materials.

[0056] In this step, based on the design compressive strength of the tunnel lining segments, the basic mix proportion of C50 fiber-reinforced concrete is determined according to the "Specification for Mix Proportion Design of Ordinary Concrete" (JGJ55). PO52.5 ordinary Portland cement is selected, with an apparent density of 3100 kg / m³. 3 Grade I fly ash has an apparent density of 2450 kg / m³. 3 The product is a polycarboxylate superplasticizer with a solid content of 30% and a water reduction rate of 30%. The mixing water is clean tap water. The fine aggregate is graded river sand with a fineness modulus of 2.5–2.7 and an apparent density of 2650 kg / m³. 3 The coarse aggregate consists of crushed stone with a particle size of 5–16 mm and an apparent density of 2700 kg / m³. 3 The basic combinations are shown in the table below.

[0057]

[0058] The raw materials in step S1 include: cement, fly ash, sand, gravel, water, water-reducing agent and fiber.

[0059] M1 = M 11 +M 12 +M 13 +M 14 +M 15 +M 16 ;

[0060] M1 is the mass of the base concrete mix proportion; M 11 Based on the cement mass of the mix proportion, M 12 Based on the mix proportion and fly ash quality, M 13 Based on the quality of the sand in the mix proportion, M 14 Based on the aggregate mass of the mix proportion, M 15 Based on the water mass of the mix proportion, M 16 The basic formula is based on the water-reducing agent mass, with fiber content of 0.

[0061] Calculate the water-cement ratio:

[0062]

[0063] S2. Calculate the unit weight of cement paste.

[0064] The calculation method in step S2 is as follows:

[0065]

[0066] γ is the unit weight of cement paste, and ρ1 is the density of cement (g / cm³). 3 K represents the water-cement ratio of the concrete.

[0067] S3. Determine the fiber water absorption rate.

[0068] Step S3 includes the following sub-steps:

[0069] S31. Wipe the fibers clean and weigh W1.

[0070] S32. Take out a certain amount of purified water using a container and soak the fiber in the purified water.

[0071] S33. Remove the fibers, absorb the water from the surface of the fibers with paper towels or towels, and weigh them W2.

[0072] S34. Calculate the water absorption rate f1 of the fiber;

[0073]

[0074] In this embodiment, existing cellulose fibers were selected, with a fiber diameter of 0.016 mm, a length of 2.1 mm, and a density of 1300 kg / m³. 3 The fiber volume fraction is 0.5%. Based on this, the fiber mass can be calculated to be 5.50 kg.

[0075] Surface area of ​​a single fiber: s1=π×0.0021×0.000016=1.055×10 -7 m 2

[0076] Volume of a single fiber: v1=π×0.0021×(8×10 -6 ) 2 =4.22×10 -13 m 3

[0077] Number of fibers: root

[0078] Total fiber surface area: S1=j1s1=1250m 2 .

[0079] S4. Calculate the mass of fiber water absorption rate caused by fiber water absorption.

[0080] m 11 =m1f1

[0081] m1 is the fiber mass, m 11 f1 represents the water absorption mass of the fiber, and f1 represents the water absorption rate of the fiber.

[0082] In this invention, step S4 further includes the following sub-steps:

[0083] S41. Wipe the fibers clean and weigh 20g.

[0084] S42. Take out a certain amount of purified water using a container and soak the fiber in the purified water.

[0085] S43. Remove the fibers, absorb the water from the surface of the fibers with paper towels or towels, and weigh 99.6g.

[0086] S44. Calculate the water absorption rate f1 of the fiber:

[0087]

[0088] W2 is the mass of the fiber after absorbing water, and W1 is the mass before absorbing water.

[0089] S45. Calculate the mass of fiber water absorption caused by fiber water absorption:

[0090] m 11 =m1f1=21.89kg.

[0091] S5. Calculate the change in mass of cementitious material caused by fiber water absorption based on S4.

[0092] The calculation process in step S5 is as follows:

[0093] m 12 =m 11 / K = 70kg;

[0094]

[0095] m 11 m represents the change in water mass caused by fiber water absorption. 12 K represents the change in mass of cementitious materials caused by water absorption by fibers, and K is the water-cement ratio of concrete.

[0096] S6. Determine the fiber coating thickness:

[0097] V1=S1D1

[0098] V1 is the fiber coating volume, S1 is the total fiber surface area, and D1 is the fiber coating thickness.

[0099] The initial determination of the sizing thickness for a single fiber is 1.5 times its diameter, therefore the sizing thickness is 0.024 mm. The fiber sizing volume is: V1 = S1D1 = 1250 × 2.4 × 10⁻⁶ mm. -5 =0.03m 3 .

[0100] S7. Calculate the change in cement paste quality caused by fiber coating.

[0101] m2=V1γ=62kg

[0102] γ is the unit weight of cement paste, V1 is the volume of paste coating, and m2 is the change in cement paste mass caused by fiber coating.

[0103] S8. Calculate the changes in the mass of cementitious materials and water caused by fiber coating according to S7.

[0104] The calculation process in step S8 is as follows:

[0105]

[0106] m 21 m represents the change in mass of cementitious materials caused by fiber coating. 211 The change in cement mass caused by fiber coating is expressed in m. 212 The change in fly ash mass caused by fiber coating is expressed in m. 22 K represents the change in water mass caused by fiber coating, and K is the water-cement ratio of the concrete.

[0107] S9. Based on steps S5 and S8, add the increased amounts of cement, fly ash, and water, as well as the actual required amount of fiber, to the initial mix proportion to obtain the first adjusted mix proportion. The mix proportion is shown in the table below:

[0108]

[0109]

[0110] The mixing ratio in step S9 is calculated as follows:

[0111] M 21 =M 11 +m 121 +m 211 ;

[0112] M 22 =M 12 +m 122 +m 212 ;

[0113] M 24 =M 14 +m 11 +m22 ;

[0114] M2 = M 21 +M 22 +M 23 +M 24 +M 25 +M 26 +M7;

[0115] M2 represents the concrete quality after the first adjustment of the concrete mix proportions. 21 For the cement quality after the first adjustment of the mix proportion, M 22 For the first adjustment of the fly ash mix ratio, M 23 The sand quality after the first adjustment of the mix ratio, M 24 For the first adjustment of the aggregate mix ratio, M 25 For the water quality after the first adjustment of the mix ratio, M 26 M7 represents the mass of the water-reducing agent after the first adjustment of the mixing ratio, and M7 represents the mass of the fiber after the first adjustment of the mixing ratio.

[0116] S10. Based on the principle of equal mass between the first adjusted mix proportion and the original mix proportion, the first adjusted mix proportion is adjusted accordingly to obtain the actual fiber-reinforced concrete mix proportion. The mix proportion is shown in the table below:

[0117]

[0118] The mixing ratio calculation in step S10 is as follows:

[0119]

[0120] n = 1 to 6

[0121] Where M 3n To determine the quality of concrete materials after the second adjustment of the mix proportions, M 2n This refers to the quality of concrete materials after the first adjustment of the mix proportions. M 31 To ensure the quality of cement after the second adjustment of the mix proportions, M 32 To determine the quality of fly ash after the second adjustment of the mix proportion, M 33 For the sand quality after the second adjustment of the mix proportion, M 34 For the second adjustment of the aggregate mix ratio, M 35 For the water quality after the second adjustment of the mix ratio, M 36 M7 represents the mass of the water-reducing agent after the second adjustment of the blending ratio, and M7 represents the mass of the fiber after the second adjustment of the blending ratio.

[0122] S11. Conduct a trial mix design based on the mix proportion from step S10. If the workability of the concrete obtained from the trial mix meets the requirements, then the mix proportion meets the requirements. If the workability does not meet the requirements, adjust the existing fiber coating thickness and continue from step S6 to step S11 until the workability of the concrete meets the requirements.

[0123] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of this invention.

Claims

1. A method for concrete mix design based on the quantitative effect of fibers on workability, characterized in that, The effect of fibers on concrete workability is broken down into two parts: fiber water absorption and fiber coating, including the following steps: S1. Determine the concrete foundation mix proportion and select raw materials according to requirements, and test the various properties of the raw materials; S2. Calculate the unit weight of cement paste; S3. Determine the fiber water absorption rate; S4. Calculate the mass of fiber water absorption rate caused by fiber water absorption; ； For fiber quality, The water absorption capacity of the fiber; This refers to the fiber's water absorption rate. S5. Calculate the change in mass of cementitious material caused by fiber water absorption based on S4. S6. Determine the fiber coating thickness; ； For fiber-coated volume, This represents the total surface area of ​​the fibers. The thickness of the fiber coating; S7. Calculate the change in cement paste mass caused by fiber coating. ； The density of cement grout is [not specified]. For the volume of the coating, The change in cement paste quality caused by fiber coating; S8. Calculate the mass change of cementitious materials and the mass change of water caused by fiber coating according to S7. S9. Based on steps S5 and S8, add the increased amounts of cement, fly ash, and water, as well as the actual required amount of fiber, to the initial mix proportion to obtain the first adjusted mix proportion. S10. Based on the principle that the mix proportion after the first adjustment is equal to the original mix proportion, the mix proportion after the first adjustment is adjusted accordingly to obtain the actual fiber concrete mix proportion used. S11. Conduct a trial mix according to the mix proportion in step S10. If the workability of the concrete obtained from the trial mix meets the requirements, then the mix proportion meets the requirements. If the workability does not meet the requirements, adjust the existing fiber coating thickness and continue from step S6 to step S11 until the workability of the concrete meets the requirements.

2. The concrete mix design method for quantifying the influence of fibers on workability according to claim 1, characterized in that: The raw materials in step S1 include: cement, fly ash, sand, gravel, water, water-reducing agent, and fiber; ； The mass of the base concrete mix proportion; M 11 For cement quality, M 12 For fly ash quality, M 13 For sand quality, M 14 For the mass of the stones, M 15 For water quality, M 16 The water-reducing agent content is 0, and the fiber content is 0.

3. The concrete mix design method for quantifying the influence of fibers on workability according to claim 1, characterized in that, The calculation method in step S2 is as follows: ； The density of cement grout is [not specified]. Cement density, in g / cm³. This refers to the water-cement ratio of concrete.

4. The concrete mix design method for quantifying the influence of fibers on workability according to claim 1, characterized in that, S3 includes the following steps: S31. Wipe the fibers clean and weigh W1; S32. Take out a certain amount of purified water using a container and soak the fiber in the purified water; S33. Remove the fibers, absorb the water from the surface of the fibers with paper towels or towels, and weigh W2. S34. Calculate the water absorption rate of the fiber. ; 。 5. The concrete mix design method for quantifying the influence of fibers on workability according to claim 1, characterized in that, The calculation process in step S5 is as follows: ； ； ； For fiber water absorption quality, This represents the change in mass of the cementitious material caused by water absorption by the fibers. The water-cement ratio of concrete. Changes in cement quality caused by fiber water absorption. Changes in fly ash mass caused by fiber water absorption.

6. The concrete mix design method for quantifying the influence of fibers on workability according to claim 1, characterized in that, The calculation process in step S8 is as follows: ； ； ； ； This refers to the change in cement paste quality caused by fiber coating. This represents the change in cement quality caused by fiber coating. This represents the change in fly ash mass caused by fiber coating. This represents the change in water mass caused by fiber sizing. This refers to the water-cement ratio of concrete.

7. The concrete mix design method for quantifying the influence of fibers on workability according to claim 1, characterized in that, The mixing ratio in step S9 is calculated as follows: ； ； ； ； To determine the concrete quality after the first adjustment of the concrete mix proportions, M 21 For the cement quality after the first adjustment of the mix proportion, M 22 For the first adjustment of the fly ash mix ratio, M 23 The sand quality after the first adjustment of the mix ratio, M 24 For the first adjustment of the aggregate mix ratio, M 25 For the water quality after the first adjustment of the mix ratio, M 26 M7 represents the mass of the water-reducing agent after the first adjustment of the mixing ratio, and M7 represents the mass of the fiber after the first adjustment of the mixing ratio.

8. The concrete mix design method for quantifying the influence of fibers on workability according to claim 1, characterized in that, The mixing ratio calculation in step S10 is as follows: ； Where M 3n To determine the quality of concrete materials after the second adjustment of the mix proportions, M 2n This refers to the quality of concrete materials after the first adjustment of the mix proportions.

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