Prediction method for splitting tensile strength of concrete

Abstract

The invention belongs to the field of concrete, and particularly discloses a method for predicting the splitting tensile strength of concrete. In the prediction method, the formula for calculating and determining the splitting tensile strength of the concrete relates to the maximum particle size of rubber particles in raw material aggregate for preparing the concrete, the minimum particle size of the rubber particles in the aggregate, the volume ratio of the rubber particles in the aggregate, the particle size coefficient of the rubber particles and the maximum particle size coefficient of the rubber particles in the aggregate. According to the prediction method, the synergistic effect of the particle size interval and the substitution rate of the rubber particles in the concrete raw materials can be considered at the same time, a clear strength prediction range can be provided in the design stage, optimization of aggregate selection and material parameter configuration is facilitated, and the design efficiency and the matching reliability are improved.

Description

Technical Field

[0001] This invention belongs to the field of concrete, and specifically relates to a method for predicting the splitting tensile strength of concrete. Background Technology

[0002] In recent years, increasing research has focused on incorporating rubber particles, formed from the grinding of waste tires, into concrete to partially replace natural aggregates, thus preparing rubberized concrete (RC). Experiments have confirmed that the addition of rubber particles helps improve the toughness of concrete, enhancing its impact energy dissipation capacity and crack propagation control, making it particularly suitable for structural components requiring a certain degree of ductility and deformation capacity. However, because different types of natural aggregates and rubber particles are heterogeneous in concrete and are influenced by various factors, the effects of natural aggregates and rubber particles on the mechanical properties of concrete are generally difficult to quantify.

[0003] Splitting tensile strength is one of the key indicators for evaluating the mechanical properties of concrete. It reflects the material's ability to resist transverse tensile stress and has significant engineering implications in structural design, safety assessment, and quality control. Traditional methods for obtaining splitting tensile strength primarily rely on direct physical tests, such as the splitting tensile test (e.g., the Brazilian disc test). While this method serves as a benchmark, it suffers from inherent limitations, including cumbersome specimen preparation, destructive testing procedures, long testing times, high costs, and difficulty in applying it to in-service structures or for rapid screening of large-scale samples.

[0004] To overcome the limitations of direct experiments, researchers have developed various indirect prediction methods. Existing prediction techniques are mainly based on theoretical or semi-theoretical empirical formulas, such as estimating using the statistical relationship between uniaxial compressive strength and splitting tensile strength. However, these methods are typically based on idealized assumptions of material homogeneity and isotropy, and the parameters of the empirical formulas are highly dependent on specific material types and curing conditions, resulting in poor universality and prediction accuracy that often fails to meet high-precision engineering requirements. Furthermore, they generally do not consider the effects of different rubber particle sizes, rubber substitution rates, and interfacial properties, failing to fully explore and integrate material composition, microstructure, and macroscopic physical properties. This limits their adaptability to complex formulation designs and variations in operating conditions and materials, and the model's generalization ability needs improvement.

[0005] In conclusion, there is an urgent need to propose a prediction method that can comprehensively consider the particle size range, substitution rate, and interfacial properties of rubber particles, so as to improve the scientific nature and engineering applicability of the prediction, and at the same time provide theoretical support for the mix design optimization and structural application of rubber concrete. Summary of the Invention

[0006] In view of the fact that the existing models for predicting the splitting tensile strength of concrete containing rubber particles have limited applicability and do not consider the influence of different rubber particle sizes and replacement rate ranges, the present invention will provide a method for predicting the splitting tensile strength of concrete.

[0007] To achieve the above objectives, the following technical solutions are specifically included: This invention provides a method for predicting the splitting tensile strength of concrete, comprising the following steps: S1. Prepare concrete, wherein the raw materials for the concrete include a gel material and aggregates, wherein the aggregates include rubber particles and inorganic aggregates; obtain the volume percentage of rubber particles in the aggregates. The maximum particle size of the rubber particles in the aggregate. and the minimum particle size of the rubber particles in the aggregate. ; S2. Calculate and determine the splitting tensile strength f of the concrete according to the following formulas 1-4. st : (1), (2), (3), (4), In the formula, This represents the splitting tensile strength of concrete, expressed in MPa. This represents the volume percentage of rubber particles in the aggregate. , The particle size coefficient of the rubber particles in the aggregate; This is the maximum particle size coefficient of rubber particles in the aggregate; This represents the maximum particle size of rubber particles in the aggregate, in mm. This represents the minimum particle size of rubber particles in the aggregate, expressed in mm.

[0008] The prediction method of this invention uses a calculation model that directly relates to the maximum particle size of rubber particles in the aggregate of concrete raw material formulations. Minimum particle size of rubber particles in aggregate Volume ratio of rubber particles in aggregate Average particle size coefficient of rubber particles , and the maximum particle size coefficient of rubber particles in aggregates. The proposed improved prediction method overcomes the limitation of existing studies that cannot consider the combined influence of coarse rubber aggregate size and replacement rate on the splitting tensile strength of concrete. Furthermore, since coarse rubber particles can slightly enhance the splitting tensile strength of concrete within a specific particle size range and at a lower replacement rate, this method introduces three coarse rubber aggregate size coefficients. This allows for accurate prediction of the splitting tensile strength of rubber concrete given a known coarse rubber aggregate size range and replacement rate, resulting in greater applicability and operability, and adaptability to engineering needs under different particle size combinations and replacement methods.

[0009] Preferably, the The volume percentage of rubber particles in the aggregate is 1-25%, with a further preferred value of 5-20%. The volume percentage Q of rubber particles in the aggregate, i.e., the replacement rate of rubber particles, is obtained by replacing inorganic aggregates with an equal volume of rubber particles. The large range of the volume percentage of rubber particles in the aggregate of this invention indicates that the prediction method of this invention is suitable for a wide range of rubber particle replacement schemes for inorganic aggregates, making the prediction method of this invention more adaptable and better suited to practical engineering needs.

[0010] Preferably, the concrete satisfies the following relationship: > ≥4.75mm. In the prediction method of the present invention, the preferred particle size of the rubber particles is coarse rubber particles, which is beneficial to improving the accuracy of the splitting tensile strength of concrete obtained by the prediction method of the present invention.

[0011] Preferably, the The thickness is 4.75-20mm, and further preferably 4.75-19mm.

[0012] Preferably, the The thickness is 4.75-20mm, and further preferably 4.75-19mm.

[0013] Preferably, in step S1, the length of the concrete is 50-500mm, the width is 50-500mm, and the height is 50-500mm, and the shape of the concrete includes at least one of cuboid, cube, or cylinder.

[0014] More preferably, in step S1, the concrete is cylindrical concrete with a height of 100-300mm and a diameter of 50-150mm.

[0015] Preferably, in step S1, the inorganic aggregate includes at least one of a first inorganic aggregate and a second inorganic aggregate; the particle size of the first inorganic aggregate is 4.75-9.6 mm, and the particle size of the second inorganic aggregate is 9.6-19 mm.

[0016] Preferably, in step S1, the rubber particles include at least one of a first rubber particle, a second rubber particle, and a third rubber particle, wherein the particle size of the first rubber particle is 4.75-9.6 mm, the particle size of the second rubber particle is 9.6-19 mm, and the particle size of the third rubber particle is 4.75-19 mm.

[0017] Using two or more aggregates of different particle sizes can improve aggregate packing density, interfacial transition zone characteristics, and overall stress distribution, thereby enhancing the mechanical properties of concrete. Furthermore, the prediction method of this invention is suitable for aggregate systems with two different particle sizes, demonstrating its broader applicability.

[0018] Preferably, in step S1, the method for preparing concrete includes the following steps: batching according to the raw material formula of concrete, and then mixing, casting and curing to obtain the concrete.

[0019] More preferably, the curing period is 10-40 days. Concrete can be prepared using the method described above, or other methods may be employed.

[0020] Preferably, the raw material formula of the concrete includes the following components in parts by weight: 500-700 parts of gel material, 500-1500 parts of aggregate, 1-10 parts of water-reducing agent, and 100-300 parts of water.

[0021] Preferably, the water-cement ratio of the raw material formula of the concrete is 0.2-0.5.

[0022] Preferably, the volume percentage of rubber particles in the aggregate is 1-25%.

[0023] Preferably, the gel material comprises cement, and the cement comprises silicate cement.

[0024] Preferably, the water-reducing agent includes a polycarboxylate water-reducing agent.

[0025] Preferably, the inorganic aggregate includes at least one of natural crushed stone and natural river sand.

[0026] More preferably, the inorganic aggregate includes a first inorganic aggregate and a second inorganic aggregate, wherein the first inorganic aggregate has a weight of 195-420 parts and the second inorganic aggregate has a weight of 510-680 parts.

[0027] More preferably, the rubber particles include at least one of a first rubber particle, a second rubber particle, and a third rubber particle, wherein the first rubber particle has a weight of 22-90 parts, the second rubber particle has a weight of 22-90 parts, and the third rubber particle has a weight of 22-90 parts.

[0028] Compared with the prior art, the present invention has the following beneficial effects: In the prediction method of the present invention, the formula for calculating and determining the splitting tensile strength of concrete involves the maximum particle size of rubber particles in the aggregate during the concrete preparation process. Minimum particle size of rubber particles in aggregate Volume ratio of rubber particles in aggregate Particle size coefficient of rubber particles , and the maximum particle size coefficient of rubber particles in aggregates. This method can simultaneously consider the synergistic effect of the particle size range of rubber particles in concrete and the replacement rate. Compared with existing prediction methods that only establish empirical relationships based on the replacement rate, it has stronger applicability and operability, and can adapt to engineering needs under different combinations of rubber particle sizes and replacement methods. It can be directly used in the mix design process of concrete containing coarse rubber aggregates, and can provide a clear strength prediction range in the design stage, which helps to optimize aggregate selection and material parameter configuration, and improve design efficiency and mix design reliability. Attached Figure Description

[0029] Figure 1 The figures show the predicted and measured splitting tensile strengths of concrete in Examples 1-12 and the control group. Detailed Implementation

[0030] To better illustrate the purpose, technical solution, and advantages of this invention, specific embodiments will be used to further explain the invention below. Unless otherwise specified, the test methods used in the embodiments and / or comparative examples are conventional methods; the materials and reagents used, unless otherwise specified, are commercially available.

[0031] Examples 1-12 and Control Group A method for predicting the splitting tensile strength of concrete includes the following steps: S1. Under the same water-cement ratio of 0.3, the raw materials are prepared according to the formula in Table 1-2 below, mixed by a forced mixer, and then cast and cured to obtain concrete. The volume of the cast test specimen is a cylindrical block with a height of 200 mm and a diameter of 100 mm. The curing time is 28 days, and the curing temperature and humidity are 22℃ and 98%, respectively.

[0032] Following the above method, a total of 12 different concretes containing coarse rubber aggregate were prepared, including a control group without coarse rubber aggregate, as shown in Table 1-2.

[0033] The cement used is commercially available ordinary Portland cement with a grade of PO42.5.

[0034] Meanwhile, the aggregate is defined to include rubber granules and inorganic aggregates. The inorganic aggregates are natural inorganic aggregates, which include two types: a first inorganic aggregate and a second inorganic aggregate. The first inorganic aggregate is commercially available natural river sand with a particle size of 4.75-9.6 mm; the second inorganic aggregate is commercially available natural crushed stone with a particle size of 9.6-19 mm. A commercially available polycarboxylate superplasticizer is used. The rubber granules include three different particle sizes: a first rubber granule, a second rubber granule, and a third rubber granule, with particle sizes ranging from 4.75-9.6 mm, 9.6-19 mm, and 4.75-19 mm, respectively. These three types of rubber granules are amorphous waste rubber granules prepared by cutting, grinding, and screening waste tires using a vibrating screen. The maximum particle size S of the rubber granules is... max and minimum particle size S min The sieving method is determined with reference to GB / T14685-2022.

[0035] S2. The splitting tensile strength test uses a cylindrical specimen with a height of 50mm and a diameter of 100mm. The cast cylindrical specimen needs to be cut in advance. The actual splitting tensile strength test is carried out in accordance with GB / T 50081-2019 standard, with a loading rate of 0.08MPa / s, to obtain the actual measured splitting tensile strength of concrete for each sample.

[0036] S3. Based on the volume ratio Q of rubber particles in the aggregate during concrete preparation in step S1, and the maximum particle size S of the rubber particles in the aggregate... max The minimum particle size S of rubber particles in aggregate min Then, calculate according to the following formulas 1-4 to obtain... , , And the predicted splitting tensile strength of concrete The data is listed in Table 3: (1), (2), (3), (4), In the formula, This represents the splitting tensile strength of concrete, expressed in MPa. This represents the volume percentage of rubber particles in the aggregate. , The particle size coefficient of the rubber particles in the aggregate; This is the maximum particle size coefficient of rubber particles in the aggregate; This represents the maximum particle size of rubber particles in the aggregate, in mm. This represents the minimum particle size of rubber particles in the aggregate, expressed in mm.

[0037] S4. The predicted splitting tensile strength of concrete and the actual measured splitting tensile strength of concrete are shown in Table 4. The predicted splitting tensile strength of concrete and the actual measured splitting tensile strength of concrete are compared and analyzed to evaluate the accuracy of the prediction method.

[0038] Table 1 Table 2 Table 3 Table 4 As shown in Table 4, when predicting the splitting tensile strength of concrete, the absolute error between the predicted and measured values ​​is controlled within 0.28 MPa, and the relative error is within 5.34%. The minimum absolute error is only 0.05 MPa, and the minimum relative error is only 1.01%. The average absolute error is 0.14 MPa, and the average relative error is 2.63%.

[0039] A predicted curve for the splitting tensile strength of concrete is plotted with the substitution rate Q of rubber particles as the x-axis and the splitting tensile strength of concrete as the y-axis. Simultaneously, the measured splitting tensile strength data points of concrete within the corresponding rubber particle size range are also represented in the graph. The results are as follows: Figure 1 As shown. Among them, Figure 1 The dots, squares, and triangles in the figures represent the measured values ​​of the splitting tensile strength of concrete containing the first (4.75-9.6 mm), second (9.6-19 mm), and third (4.75-19 mm) rubber particles, respectively, in Examples 1-12. The long dashed line, double-dotted line, and straight line represent the predicted splitting tensile strength curves of concrete containing the first (4.75-9.6 mm), second (9.6-19 mm), and third (4.75-19 mm) rubber particles, respectively, in Examples 1-12. The model of the predicted curves fits the actual measured data to a degree of R0. 2 =0.94, which not only shows a high correlation, but also demonstrates excellent prediction accuracy and precision.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for predicting the splitting tensile strength of concrete, characterized in that, Includes the following steps: S1. Prepare concrete, wherein the raw materials for the concrete include a gel material and aggregates, wherein the aggregates include rubber particles and inorganic aggregates; obtain the volume percentage of rubber particles in the aggregates. The maximum particle size of the rubber particles in the aggregate. and the minimum particle size of the rubber particles in the aggregate. ; S2. Calculate and determine the splitting tensile strength f of the concrete according to the following formulas 1-4. st : （1）， （2）， （3）， （4）， In the formula, This represents the splitting tensile strength of concrete, expressed in MPa. This represents the volume percentage of rubber particles in the aggregate. , The particle size coefficient of the rubber particles in the aggregate; This is the maximum particle size coefficient of rubber particles in the aggregate; This represents the maximum particle size of rubber particles in the aggregate, in mm. This represents the minimum particle size of rubber particles in the aggregate, expressed in mm.

2. The method for predicting the splitting tensile strength of concrete as described in claim 1, characterized in that, The It ranges from 1% to 25%.

3. The method for predicting the splitting tensile strength of concrete as described in claim 1, characterized in that, The following relationship must be satisfied: > ≥4.75mm.

4. The method for predicting the splitting tensile strength of concrete as described in claim 1, characterized in that, In step S1, the inorganic aggregate includes at least one of a first inorganic aggregate and a second inorganic aggregate; the particle size of the first inorganic aggregate is 4.75-9.6 mm, and the particle size of the second inorganic aggregate is 9.6-19 mm.

5. The method for predicting the splitting tensile strength of concrete as described in claim 1, characterized in that, In step S1, the rubber particles include at least one of a first rubber particle, a second rubber particle, and a third rubber particle, wherein the particle size of the first rubber particle is 4.75-9.6 mm, the particle size of the second rubber particle is 9.6-19 mm, and the particle size of the third rubber particle is 4.75-19 mm.

6. The method for predicting the splitting tensile strength of concrete as described in claim 1, characterized in that, In step S1, the method for preparing concrete includes the following steps: batching the raw materials according to the concrete formula, and then mixing, casting and curing to obtain the concrete.

7. The method for predicting the splitting tensile strength of concrete as described in claim 6, characterized in that, The raw material formula of the concrete includes the following components in parts by weight: 500-700 parts of gel material, 500-1500 parts of aggregate, 1-10 parts of water-reducing agent, and 100-300 parts of water.

8. The method for predicting the splitting tensile strength of concrete as described in claim 7, characterized in that, Includes at least one of the following I-IV: I. The volume percentage of rubber particles in the aggregate is 1-25%; II. The gel material includes cement, and the cement includes silicate cement; III. The water-reducing agent includes polycarboxylate water-reducing agents; IV. The inorganic aggregate includes at least one of natural crushed stone and natural river sand.

9. The method for predicting the splitting tensile strength of concrete as described in claim 7, characterized in that, The inorganic aggregate includes a first inorganic aggregate and a second inorganic aggregate, wherein the first inorganic aggregate has a weight ratio of 195-420 parts and the second inorganic aggregate has a weight ratio of 510-680 parts.

10. The method for predicting the splitting tensile strength of concrete as described in claim 7, characterized in that, The rubber particles include at least one of a first rubber particle, a second rubber particle, and a third rubber particle, wherein the first rubber particle has a weight of 22-90 parts, the second rubber particle has a weight of 22-90 parts, and the third rubber particle has a weight of 22-90 parts.

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