Concrete aggregate uniformity control method

Abstract

The invention discloses a concrete aggregate uniformity control method. The method aims at solving the limitation problem that an existing concrete aggregate uniformity degree control method cannot be combined with specific construction conditions and is lack of systematic integration and analysis of all influence factors. The method comprises the following steps: measuring the layering degree of concrete aggregate under different admixtures and mixing amounts by adopting a layering degree instrument, and determining the mixing amount range of each admixture according to the uniformity degree of the aggregate; based on the mixing amount range of each admixture, the aggregate layering degree of the concrete under different vibration systems is measured, specific vibration methods under different vibration systems are optimized, and the mixing amount range of the admixture under the corresponding vibration system is determined; and determining the correlation degree between each vibrating system and the aggregate uniformity by adopting a grey correlation degree analysis method, and optimizing the vibrating method and the mixing amount of the admixture according to indexes. The method is used for controlling the uniformity of the concrete aggregate.

Description

Technical Field

[0001] This application relates to the technical field of civil engineering, and particularly relates to a method for controlling the uniformity of concrete aggregates. Background Art

[0002] In the field of civil engineering, concrete is one of the most widely used building materials. In recent years, with the development of China's social economy, there have been more and more infrastructure constructions such as various buildings, structures, highways, and railways, and the demand for concrete has also been increasing. The increasing demand for concrete has brought new requirements for its performance. Different rheological properties of concrete and disturbances during pouring or hardening will cause the yield stress of the concrete paste to decrease, resulting in the settlement or floating of aggregates and the segregation of concrete, which not only affects the construction progress, construction quality, and labor intensity, but more importantly, also seriously affects the physical and mechanical properties and durability of concrete in the later stage.

[0003] Currently, the research on the uniformity of concrete aggregates mainly involves aspects such as mix ratio optimization and improvement of mixing technology. The image analysis technology, ultrasonic analysis, gamma-ray attenuation technology, etc. adopted in related research mainly analyze the uniformity of aggregates in concrete test blocks after curing, with a long cycle and high difficulty, and effective control measures for the uniformity of concrete aggregates cannot be obtained. In addition, for the currently widely used segmented screening method, some scholars only optimize the concrete mix ratio through the degree of aggregate stratification, or analyze the uniformity of concrete through a single vibration system, and fail to systematically integrate and analyze various influencing factors. Under different construction environments, the required concrete materials and construction technologies are different, and the specific vibration methods and corresponding admixture ratios cannot be effectively controlled, resulting in uneven distribution of concrete aggregates and seriously affecting the mechanical properties of concrete. Therefore, providing a method for controlling the uniformity of concrete aggregates to ensure the homogeneity of concrete aggregates and the workability of concrete under different construction environments has practical significance. Summary of the Invention

[0004] In order to solve the above deficiencies of the prior art, the purpose of the present invention is to provide a method for controlling the uniformity of concrete aggregates to overcome the defects in the prior art.

[0005] To achieve the above purpose, the present invention provides a method for controlling the uniformity of concrete aggregates, which includes the following steps: S1: Use a slump cone to measure the slump of concrete aggregates under different admixtures and dosages, and determine the dosage range of each admixture according to the degree of aggregate uniformity; S2: Based on the dosage range of each admixture, measure the slump of concrete aggregates under different vibration systems, optimize the specific vibration methods under different vibration systems, and determine the dosage range of admixtures under the corresponding vibration systems; S3: Use the grey relational analysis method to determine the correlation degree between each vibration system and the aggregate uniformity, and optimize the vibration method and admixture dosage according to the index.

[0006] For the concrete aggregate uniformity control method described above, the concrete aggregate stratification degree under different admixtures and dosages is measured by using a slump cone, specifically including: S101: Pour the stirred concrete into the slump cone, and control the pouring process into the mold to be completed within 1 minute. S102: Treat the concrete in the slump cone by using different vibration methods. After the treatment, pour the concrete in each layer of the slump cone into a standard square-hole sieve within 1 minute, and rinse the cement paste and sand in it with tap water until clean. S103: Then put the aggregates in each layer into a drying oven at 105 °C and dry them for 2 hours to ensure that the aggregates are dried to a completely dry state. After drying, take out the aggregates and cool them to room temperature, and sieve out the materials other than the aggregates with a standard square-hole sieve of 5 mm. S104: Finally, weigh the mass of the aggregates in each layer with an electronic balance, and calculate the concrete mass stratification degree through the following formula: ; In the formula: is the mass ratio of the concrete aggregate in the th layer; is the mass of the th layer of aggregates; is the total mass of all aggregates in the sample; is the concrete mass stratification degree, simply referred to as the stratification degree; is the average value of the mass percentages of the aggregates in each layer.

[0007] For the concrete aggregate uniformity control method described above, in S2, according to the dosage ranges of the respective admixtures, the aggregate stratification degrees of the concrete under different vibration systems are measured, specifically including: S201: Conduct experimental designs on the concrete under different vibration systems and different mix ratios. S202: Take the single vibration system and the admixture mix ratio as variables, measure the aggregate stratification degrees of the concrete respectively, and conduct comparative analysis to obtain different vibration systems and the corresponding admixture mix ratios.

[0008] For the concrete aggregate uniformity control method described above, in S3, the grey relational analysis method is used to determine the correlation degree between each vibration system and the aggregate uniformity, and the vibration method and admixture dosage are optimized according to the index, specifically including: S301: Consider different vibration systems as influencing factors, and use the grey relational analysis method to obtain the contribution of each factor to the degree of aggregate uniformity; S302: Take the slump as the reference sequence, use each factor as the comparison sequence, perform normalization processing on the data by the mean method, and then calculate the grey correlation coefficient and the grey relational degree; S303: Sort the influencing factors through the grey relational degree, and optimize the specific vibration method and the corresponding admixture dosage.

[0009] The described method for controlling the uniformity of concrete aggregates, the grey relational analysis method includes the following steps: Before performing grey relational analysis, first perform normalization processing on the data by the mean method: ; In the formula: is the reference sequence; is the normalized reference sequence; is the comparison sequence; is the normalized comparison sequence; represents different vibration systems, ; The grey correlation coefficient can be obtained from (5): ; In the formula: is the grey correlation coefficient; and are respectively the minimum and maximum values of the absolute values of the differences between the elements corresponding to all comparison sequences and the reference sequence; is the coefficient for controlling the discrimination degree of the grey correlation coefficient, taking 0.5; Multiple grey correlation coefficients can be obtained for each column, and the mean value of multiple grey correlation coefficients needs to be calculated to obtain the grey relational degree , The larger the .

[0010] The described method for controlling the uniformity of concrete aggregates, the vibration system includes different standing times, vibration times, and vibration frequencies.

[0011] Advantages of the present invention: 1. The present invention measures the degree of segregation of concrete aggregates under different admixtures and dosages, determines the dosage range of each admixture according to the uniformity of the aggregates; based on the dosage range of each admixture, measures the degree of segregation of concrete aggregates under different vibration systems, optimizes the specific vibration methods under different vibration systems, and determines the dosage range of the admixture under the corresponding vibration system, effectively controlling the uniformity of concrete aggregates; taking the degree of segregation of aggregates as the reference sequence and the vibration system as the comparison sequence, uses the grey relational analysis method to determine the correlation degree between each vibration system and the uniformity of aggregates, and optimizes the vibration method and the dosage of the admixture according to the index, providing an effective reference for controlling the uniformity of concrete aggregates and having high operability. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a schematic flow chart of the present invention; Figure 2 is a schematic principle diagram of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0013] In order to further understand the structure, characteristics and other purposes of the present invention, the following is a detailed description with reference to the attached preferred embodiments and accompanying drawings. The embodiments described by the drawings are only used to illustrate the technical solutions of the present invention and do not limit the present invention.

[0014] Referring to Figure 1 - Figure 2 , a method for controlling the uniformity of concrete aggregates controls the uniformity of concrete aggregates from two aspects of the dosage of concrete admixtures and the vibration system through experimental design and system optimization.

[0015] Step S1, use a slump cone to measure the degree of segregation of concrete aggregates under different admixtures and dosages, and determine the dosage range of each admixture according to the uniformity of the aggregates; Referring to JGJ 55-2011 "Code for Design of Mix Proportions of Ordinary Concrete" and JGJ / T 12-2019 "Technical Standard for Application of Lightweight Aggregate Concrete", the mix proportion design is carried out by the absolute volume method: first, set the dosage of water reducer at 0%, 0.3%, 0.5%, 0.7% (the ratio of the solid content of the water reducer to the total mass of the cementitious materials) to obtain mortars with different fluidities; in order to improve the segregation and bleeding of the aggregates and the mortar and increase the fluidity of the aggregates and the mortar, the present invention uses fly ash at 0%, 10%, 20%, 30% (the mass ratio of fly ash to the cementitious materials) to replace cement; in order to increase the viscosity of the aggregates and the mortar and reduce the floating degree of the aggregates, silica fume or cellulose is incorporated into the cementitious materials, the dosage of silica fume is 0%, 3%, 6%, 9% (mass ratio) of the cementitious materials, and the dosage of cellulose is 0%, 0.02%, 0.04% (mass ratio) of the cementitious materials.

[0016] According to the operation method of the slump cone, measure the degree of segregation of concrete aggregates under different mix proportions, as shown in Table 1 below:

[0017] According to this aggregate segregation degree table, the admixture range for each dosage is determined. When the aggregate segregation degree is closer to 1, the aggregate is more uniform. Therefore, when the water reducer is controlled within 0.3% - 0.7%, fly ash is controlled within 0% - 10%, silica fume is controlled within 0.3% - 0.9%, and hydroxypropyl methylcellulose is controlled within 0% - 0.02%, the uniformity of concrete aggregates is good.

[0018] Step S2: Based on the admixture dosage ranges of the respective admixtures, measure the aggregate segregation degree of concrete under different vibration systems, optimize the specific vibration methods under different vibration systems, and determine the admixture dosage ranges corresponding to the vibration systems. An experimental design is carried out for concrete with different vibration systems and different mix ratios. The vibration systems adopted in the present invention include different vibration times (5s, 10s, 15s, 25s), standing times (0min, 3min, 6min), and vibration frequencies (50Hz, 100Hz, 200Hz). To introduce the embodiments in detail, the present invention only takes the silica fume dosages of 0.3% and 0.9% (mass ratio) as variables, measures the aggregate segregation degree of concrete respectively, and through comparative analysis, obtains the relatively optimal vibration system and the corresponding admixture ratio, as shown in Table 2 below:

[0019]

[0020] According to this aggregate segregation degree table, when the vibration time is controlled at 10s, the standing time is controlled at 3min, and the vibration frequency is controlled at 200Hz, the uniformity of concrete aggregates is good. And when the vibration time is 10s, the standing time is 3min, and the vibration frequency is 200Hz, with the silica fume dosage controlled at 9%, the aggregate uniformity is relatively excellent.

[0021] Step S3: Use the grey relational analysis method to determine the correlation degree between each vibration system and the aggregate uniformity, and optimize the vibration method and admixture dosage according to the index.

[0022] According to the three vibration systems and the segregation degree in Table 2, taking the segregation degree as the reference sequence and the three vibration systems as the comparison sequences, the data is normalized using the mean method, and then the grey correlation coefficient and grey correlation degree are calculated.

[0023] According to the above steps, the grey correlation degrees of each factor are respectively: (vibration time) = 0.894, (standing time) = 0.646, (vibration frequency) = 0.817. The order of the influence of these three factors on the aggregate uniformity from large to small is: vibration time > vibration frequency > standing time. The vibration time is one of the main factors determining the severity of aggregate settlement. Therefore, it is necessary to strictly control the vibration time at 10s, the vibration frequency at 200Hz, the standing time at 3min, and the silica fume dosage at 3%.

[0024] It should be noted that the above-mentioned invention content and specific implementation manners are intended to prove the practical application of the technical solution provided by the present invention, and should not be construed as a limitation on the protection scope of the present invention. Those skilled in the art can make various modifications, equivalent substitutions or improvements within the spirit and principle of the present invention. The protection scope of the present invention shall be subject to the appended claims.

Claims

1. A method for controlling uniformity of concrete aggregate, characterized in that: The method comprises the following steps: S1: Use a stratification meter to measure the stratification of concrete aggregates under different admixtures and dosages, and determine the dosage range of each admixture based on the uniformity of the aggregates; S2: Based on the dosage range of each admixture, the aggregate stratification degree of concrete under different vibration systems is determined, the specific vibration method under different vibration systems is optimized, and the dosage range of the admixture under the corresponding vibration system is determined; S3: Use grey correlation analysis to determine the correlation between each vibration system and aggregate uniformity, and optimize the vibration method and admixture dosage based on the indicators.

2. A method for controlling uniformity of concrete aggregate according to claim 1, characterized in that: The method of using a stratification meter to measure the stratification degree of concrete aggregate under different admixtures and admixture amounts specifically includes: S101: The mixed concrete is loaded into a layering instrument, and the mold loading process is controlled to be completed within 1 minute; S102: using different vibration methods to treat the concrete in the layering meter, and within 1 minute after the completion, pour each layer of concrete in the layering meter into a standard square hole sieve, and rinse the cement slurry and sand therein with tap water; S103: Then put the aggregates in each layer into a drying oven at 105°C for 2 hours to ensure that the aggregates are completely dried. After the drying is completed, take out the aggregates and cool them to room temperature, and use a 5 mm standard square hole sieve to sieve out materials other than aggregates; S104: Finally, the mass of each layer of aggregate is weighed with an electronic balance, and the concrete mass stratification degree is calculated by the following formula; ； Where: is the mass ratio of the first layer of concrete aggregate; is the mass of the first layer of aggregate; is the total mass of all aggregates in the sample; It is the quality stratification degree of concrete, referred to as stratification degree; It is the average value of the mass percentage of aggregate in each layer.

3. A method for controlling uniformity of concrete aggregate according to claim 2, characterized in that: In the step S2, the aggregate stratification degree of concrete under different vibration systems is determined according to the dosage range of each admixture, which specifically includes: S201: Experimental design of concrete under different vibration systems and different mix ratios; S202: Taking a single vibration system and admixture ratio as variables, the aggregate stratification degree of concrete is measured respectively, and different vibration systems and corresponding admixture ratios are obtained by comparative analysis.

4. A method for controlling uniformity of concrete aggregate according to claim 3, characterized in that: In the above S3, the grey correlation analysis method is used to determine the correlation between each vibration system and aggregate uniformity, and the vibration method and admixture dosage are optimized according to the indicators, specifically including: S301: Considering different vibration systems as influencing factors, the grey correlation analysis method is used to obtain the contribution of each factor to the uniformity of aggregate; S302: Taking the stratification degree as the reference sequence and each factor as the comparison sequence, the data is normalized by using the mean value method, and then the grey correlation coefficient and grey correlation degree are obtained; S303: Sort the influencing factors by grey correlation, and optimize the specific vibration method and the corresponding admixture dosage.

5. A method for controlling uniformity of concrete aggregate according to claim 4, characterized in that: The grey relational analysis method comprises the following steps: Before conducting grey relational analysis, the data is first normalized using the mean value method: ； Where: is the reference sequence; is the normalized reference sequence; To compare the sequences; is the normalized reference sequence; Represents different vibration systems, ; The grey correlation coefficient can be obtained by (5): ； Where: is the grey correlation coefficient; and are the minimum and maximum absolute values ​​of the differences between the elements of all comparison sequences and the reference sequence respectively; To control the coefficient of discrimination of grey relational coefficient, take 0.5; Each column can get multiple grey correlation coefficients, and it is necessary to calculate the average of multiple grey correlation coefficients to get the grey correlation degree. , The larger the value, the greater the influence of this factor on the floating degree of aggregate: 。 6. A method for controlling uniformity of concrete aggregate according to claim 5, characterized in that: The vibration system includes different standing time, vibration time and vibration frequency.

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