Mix proportion design method of rubberized concrete based on compressive strength softening model

Abstract

The application provides a rubber concrete mix proportion design method based on a compressive strength softening model, comprising the following steps: S1, selecting a reference concrete mix proportion; S2, using rubber aggregate to replace ordinary fine aggregate in the reference concrete in an equal volume manner, and carrying out a pre-test on the compressive strength of the concrete with different rubber aggregate contents; S3, performing regression analysis on the test data, and establishing a rubber concrete strength softening model to determine the rubber aggregate content corresponding to the rubber concrete with a required strength grade, or to determine the compressive strength grade of the rubber concrete with the required rubber aggregate content; S4, if the rubber aggregate content or the compressive strength grade of the rubber concrete determined in S3 meets the requirement, the rubber concrete mix proportion design is completed, otherwise, a reference concrete mix proportion is selected again. The application realizes the mix proportion design of the rubber concrete with different compressive strength grades.

Description

Technical Field

[0001] This invention relates to the field of rubber concrete technology, and specifically to a method for designing the mix proportion of rubber concrete based on a compressive strength softening model. Background Technology

[0002] To address the environmental pollution caused by waste rubber tires, researchers processed them into rubber aggregates and used these aggregates to prepare rubber concrete. The study found that incorporating rubber aggregates significantly improved the sustainable plastic deformation bearing capacity, damage tolerance, and toughness of concrete. However, as the amount of rubber aggregates increased, the compressive strength of the concrete decreased.

[0003] To design the mix proportion of rubber-concrete with the required strength grade, researchers first select a benchmark concrete mix proportion with a higher strength grade. Based on this, they replace the ordinary fine aggregate in the benchmark concrete with an equal volume of rubber aggregate and conduct preliminary compressive strength tests on concrete with different rubber aggregate dosages. Subsequently, regression analysis is performed on the test data, and a strength softening model is established to determine the rubber aggregate dosage corresponding to the required strength grade of rubber-concrete, ultimately determining the rubber-concrete mix proportion.

[0004] It should be noted that existing models all use the rubber aggregate replacement rate as the independent variable. However, in reality, the rubber aggregate replacement rate changes with the benchmark concrete mix proportion. In other words, a mathematical model established by one experimenter cannot be used by others, thus existing models lack universality. Furthermore, existing models do not consider the influence of rubber aggregate particle size. In other words, when the rubber aggregate particle size changes (e.g., rubber powder changes to crushed rubber particles), the prediction accuracy of existing models will significantly decrease. Therefore, establishing a universally applicable and highly accurate rubber concrete strength softening model is of practical significance for guiding the mix design of rubber concrete. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to establish a universal and highly accurate compressive strength softening model to achieve the mix design of rubber concrete.

[0006] Specific technical solutions:

[0007] The rubber concrete mix design method based on the compressive strength softening model of the present invention includes the following steps:

[0008] S1. Select a reference concrete mix proportion (the compressive strength grade of the reference concrete should be greater than the compressive strength grade of the rubber concrete);

[0009] S2. Replace ordinary fine aggregate in the reference concrete with rubber aggregate of equal volume, and conduct pre-tests on the compressive strength of concrete with different rubber aggregate admixture contents;

[0010] S3. Perform regression analysis on the test data and establish a rubber concrete strength softening model to determine the rubber aggregate content corresponding to the required strength grade of rubber concrete, or to determine the compressive strength grade of rubber concrete with the required rubber aggregate content.

[0011] S4. If the rubber aggregate content or compressive strength grade of rubber concrete determined in S3 meets the requirements, the rubber concrete mix design is completed; otherwise, a new benchmark concrete mix design is selected.

[0012] Preferably, in S3, the rubber concrete strength softening model is configured to include:

[0013] S31. The volume fraction of rubber aggregate is used to describe the rubber aggregate content. The volume fraction of rubber aggregate can be calculated using the following formula:

[0014]

[0015] Among them, V OR W represents the absolute volume fraction of the rubber aggregate. OR and ρ OR These are the mass and density of the rubber aggregate, respectively; W i ρ and ρi represent the mass and density of other materials, including water, cement, rubber aggregate, ordinary fine aggregate, and ordinary coarse aggregate, respectively.

[0016] S32. The compressive strength of rubber concrete can be calculated using the following formula:

[0017] f RC =f C ·S * (2)

[0018] Among them, f RC f is the compressive strength of rubber concrete; C S is the benchmark concrete compressive strength; * A model for the strength softening of rubber concrete;

[0019] Preferably, in S32, the rubber concrete strength softening model is configured to include:

[0020] S321. When the rubber aggregate is rubber powder (the nominal particle size of the rubber aggregate is less than 1 mm), the strength softening model of rubber concrete can be calculated by the following formula:

[0021]

[0022] in, The model parameters are 7.66 to 8.58. Within this range, the rubber concrete strength softening model will have good predictability; conversely, the predictability of the model will decrease if the parameters are outside this range.

[0023] S322. When the rubber aggregate is crushed rubber particles (nominal particle size of rubber aggregate is 1-5mm), the strength softening model of rubber concrete can be calculated by the following formula:

[0024] S * =(1-V OR ) λ (4)

[0025] Wherein, λ is the model parameter, with a value of 8.41 to 9.07; within this parameter range, the rubber concrete strength softening model will have good predictability, and conversely, the predictability of the model will decrease.

[0026] The beneficial effects of this invention are as follows:

[0027] 1. This invention, based on a rubber concrete strength softening model, enables the design of mix proportions for rubber concrete with different compressive strength grades. Benefiting from using the volume fraction of rubber aggregate as the independent variable, the rubber concrete strength softening model can be used as a benchmark concrete mix proportion for different testers, thus exhibiting strong universality. Specifically, even without conducting preliminary tests, different testers can accurately calculate the compressive strength of concrete with different rubber aggregate contents. This significantly reduces the working time of testers in this field, improves work efficiency, and saves labor and material costs.

[0028] 2. This invention provides corresponding model parameter values ​​for rubber aggregates of different particle sizes (including rubber powder and crushed rubber particles), achieving higher accuracy in predicting compressive strength, so as to better guide the mix design of rubber concrete. Attached Figure Description

[0029] Figure 1 The test values ​​of compressive strength of rubber concrete with strength grades of C45, C30 and C25 in Example 1 and the calculated values ​​based on the rubber concrete strength softening model are shown.

[0030] Figure 2 The values ​​are the test values ​​of the compressive strength of rubber concrete with strength grades of C40, C30 and C20 in Example 2 and the calculated values ​​based on the rubber concrete strength softening model. Detailed Implementation

[0031] The specific technical solutions of the present invention will be described with reference to the embodiments.

[0032] The present invention will now be described in further detail:

[0033] Example 1

[0034] (1) Select a reference concrete with a strength grade of C55 (compressive strength test value of 60.29MPa), and its mix proportion is: 621kg / m³ of natural fine aggregate. 3 1394 kg / m³ of natural coarse aggregate 3 Cement 405kg / m 3 Water 158kg / m 3 The densities of natural fine aggregate, natural coarse aggregate, cement, and water are 2650, 2630, 3150, and 1000 kg / m³, respectively. 3 .

[0035] (2) Rubber powder was selected as the rubber aggregate, with a density of 1120 kg / m³. 3 , The value is 8.12. Rubber powder was used to replace the natural fine aggregate in the reference concrete by equal volume, with replacement rates of 15%, 30%, and 45%, respectively, corresponding to absolute volume fractions of 3.345%, 6.690%, and 10.035%.

[0036] (3) Based on the rubber concrete strength softening model, the compressive strength of rubber concrete with rubber aggregate volume fraction of 3.345%, 6.690% and 10.035% was calculated, and the values ​​were 45.76, 34.37 and 25.56 MPa, respectively. The corresponding rubber concrete strength grades were C45, C30 and C25, respectively.

[0037] like Figure 1 As shown, Figure 1 The test values ​​of compressive strength of rubber concrete with strength grades of C45, C30 and C25 and the calculated values ​​based on the rubber concrete strength softening model are shown. It can be seen that the test values ​​and the calculated values ​​are in good agreement, and the average error is less than 1.4%.

[0038] Example 2

[0039] (1) Select a reference concrete with a strength grade of C55 (compressive strength test value of 60.29MPa), and its mix proportion is: 621kg / m³ of natural fine aggregate. 3 1394 kg / m³ of natural coarse aggregate 3 Cement 405kg / m 3 Water 158kg / m 3 The densities of natural fine aggregate, natural coarse aggregate, cement, and water are 2650, 2630, 3150, and 1000 kg / m³, respectively. 3 .

[0040] (2) Crushed rubber particles were selected as rubber aggregate with a density of 1120 kg / m³.3 , The value was 8.73. Crushed rubber particles were used to replace the natural fine aggregate in the reference concrete at equal volume rates of 15%, 30%, and 45%, with corresponding absolute volume fractions of 3.345%, 6.690%, and 10.035%, respectively.

[0041] (3) Based on the rubber concrete strength softening model, the compressive strength of rubber concrete with rubber aggregate volume fraction of 3.345%, 6.690% and 10.035% was calculated. The values ​​were 44.80, 32.92 and 23.94 MPa, respectively, and the corresponding rubber concrete strength grades were C40, C30 and C20.

[0042] like Figure 2 As shown, Figure 2 The test values ​​of compressive strength of rubber concrete with strength grades of C40, C30 and C20 and the calculated values ​​based on the rubber concrete strength softening model are shown. It can be seen that the test values ​​and the calculated values ​​are in good agreement, and the average error is less than 2.8%.

Claims

1. A method for designing the mix proportion of rubber concrete based on a compressive strength softening model, characterized in that, Includes the following steps: S1. Select a benchmark concrete mix proportion; S2. Replace ordinary fine aggregate in the reference concrete with rubber aggregate of equal volume, and conduct pre-tests on the compressive strength of concrete with different rubber aggregate admixture contents; S3. Perform regression analysis on the test data and establish a rubber concrete strength softening model to determine the rubber aggregate content corresponding to the required strength grade of rubber concrete, or to determine the compressive strength grade of rubber concrete with the required rubber aggregate content. The rubber concrete strength softening model is configured to include: S31. The volume fraction of rubber aggregate is used to describe the rubber aggregate content; the volume fraction of rubber aggregate is calculated using the following formula: （1） Among them, V OR W represents the absolute volume fraction of the rubber aggregate. OR and ρ OR These are the mass and density of the rubber aggregate, respectively; W i ρ and ρi are the mass and density of other materials, including water, cement, rubber aggregate, ordinary fine aggregate and ordinary coarse aggregate, respectively; S32. The compressive strength of rubber concrete is calculated using the following formula: （2） Among them, f RC f is the compressive strength of rubber concrete; C S is the benchmark concrete compressive strength; * A model for the strength softening of rubber concrete; The rubber concrete strength softening model is configured to include: S321: Rubber aggregate with a nominal particle size of less than 1 mm is rubber powder; S322: Rubber aggregate with a nominal particle size of 1~5 mm is crushed rubber particles. When the rubber aggregate is rubber powder, the strength softening model of rubber concrete is calculated using the following formula: （3） Wherein, φ is a model parameter with a value of 7.66~8.58; within this parameter range, the rubber concrete strength softening model will have good predictability, and conversely, the predictability of the model will decrease. S322. When the rubber aggregate is crushed rubber particles, the rubber concrete strength softening model is calculated using the following formula: （4） Wherein, λ is the model parameter, with a value of 8.41~9.07; within this parameter range, the rubber concrete strength softening model will have good predictability, and conversely, the predictability of the model will decrease. S4. If the rubber aggregate content or compressive strength grade of rubber concrete determined in S3 meets the requirements, the rubber concrete mix design is completed; otherwise, a new benchmark concrete mix design is selected.

2. The method for designing the mix proportion of rubber concrete based on the compressive strength softening model according to claim 1, characterized in that, The aforementioned benchmark concrete compressive strength grade is greater than that of rubber concrete compressive strength grade.

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