CN102830000A - Preparation method of cement concrete scientific research sample - Google Patents

Abstract

The invention discloses a preparation method of a cement concrete scientific research test piece, aiming to make the cement concrete test piece have the same compressive strength index, water-cement ratio and gradation data, and meet the requirements of various test equipment. The technical solution is to select the size of the cement concrete specimen and the maximum crushed stone particle size according to the material testing machine, the triaxial cavity of the triaxial testing machine and the diameter of the Hopkinson pressure bar; according to the maximum particle size of the crushed stone and the strength requirements of hydraulic concrete, According to the national standard JGJ53-92 and JGJ52-92, the gradation data and material mix ratio are selected, and the gradation data and material mix ratio of cement concrete are determined through the standard specimen test specified in GB/T 50081-2002; finally, according to the gradation data and The material mix ratio is used to make test specimens that meet the requirements of relevant test equipment. The invention can ensure that the test pieces used in various test equipments not only have the same grade of cement concrete compressive strength, but also meet the requirements of the respective test equipments, and reduce the human errors in the test piece production process.

Description

Preparation method of cement concrete scientific research specimen

technical field

The invention relates to a preparation method of a scientific research specimen used when determining parameters of a cement concrete dynamic constitutive model by using three kinds of test equipment, a material testing machine, a conventional triaxial testing machine and a Hopkinson compression bar.

Background technique

The airport runway is one of the main targets attacked by the hostile sides in wartime. Due to limited funds and time, its response law under the action of penetrating explosive bombs is mainly obtained through numerical simulation. Cement concrete is the main construction material of airport runways, and its dynamic constitutive parameters are the key to numerical simulation calculations. Therefore, the constitutive parameters of cement concrete materials must be obtained through systematic scientific experiments.

The cement concrete scientific research specimen is the main test object for determining the parameters of the cement concrete constitutive model. The national standard GB/T50081-2002 "Standards for Test Methods of Mechanical Properties of Ordinary Concrete" stipulates the size, shape and tolerance of the test piece when testing cement concrete, test equipment, production and maintenance of the test piece, compressive strength, axial compressive strength, Test requirements and methods for parameters such as static compression modulus of elasticity, splitting tensile strength and flexural strength. These parameters are only part of the static constitutive model parameters. For the static constitutive model parameters included in the dynamic constitutive model, such as cohesive strength, pressure hardening coefficient, pressure hardening exponent and dynamic constitutive model parameters such as strain rate hardening coefficient, etc. It cannot be tested by the test equipment and test methods stipulated in the national standard GB/T50081-2002 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete". As a workaround, at present, the numerical calculation is generally consistent with the results of the cement concrete target invasion explosion test by adjusting the constitutive parameters, but this method is not scientific and is not conducive to revealing the objective law of the dynamic response of cement concrete.

The parameters of the constitutive model of cement concrete can be measured by testing cement concrete specimens with test equipment such as material testing machines, conventional triaxial testing machines, and Hopkinson compression bars. It is relatively simple to prepare cement concrete specimens for the above test equipment. As long as the shape and size of the finished test piece meet the requirements of the respective test equipment. However, the cement concrete specimens produced in this form have differences in the cement concrete compressive strength index, water-cement ratio, and gradation data, which makes the cement concrete specimens used in different test equipment lack internal consistency, resulting in the test measurement The parameters of the obtained constitutive model of cement concrete have large errors, which lead to wrong results when the parameters of the obtained constitutive model are used to evaluate the response of cement concrete under penetration and blast loads.

Contents of the invention

The technical problem to be solved by the present invention is to provide a preparation method for measuring the parameters of the cement concrete dynamic constitutive model scientific research specimens, the cement concrete specimens produced by this method have the same compressive strength index, water-cement ratio and gradation Data to meet the requirements of various testing equipment such as material testing machine, conventional triaxial testing machine and Hopkinson compression bar.

The technical scheme of the present invention is: according to the material testing machine, triaxial testing machine triaxial chamber and Hopkinson pressure bar rod diameter to select cement concrete specimen size and maximum crushed stone particle size; then, according to the selected crushed stone maximum The particle size and strength requirements of hydraulic concrete are selected according to the national standard JGJ53-92 "Quality Standard and Inspection Method for Gravel or Pebble for Ordinary Concrete" and the national standard JGJ52-92 "Quality Standard and Inspection Method for Ordinary Concrete Sand". Material mix ratio, through the standard specimen test stipulated in GB/T50081-2002 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete", determine the gradation data and material mix ratio of cement concrete; finally, according to the determined gradation data and material mix ratio Make test specimens that meet the requirements of relevant test equipment.

The specific implementation plan is:

The first step is to determine the size of the specimen and the range of the material testing machine and the conventional triaxial testing machine used for the material testing machine, the conventional triaxial testing machine (that is, the triaxial testing machine in which the test specimen is a cylinder) and the Hopkinson bar .

1.1. Determine the compressive strength grade f _c of the cement concrete to be studied according to the needs of scientific research, and determine the working range R of the material testing machine to be used by formula (1);

20% R≤k f _c A≤80% R Formula (1)

d为三轴腔内直径；k为直径为d高度为2d的水泥混凝土圆柱体试件所具有的抗压强度

与水泥混凝土抗压强度等级f_c之间比例系数Here, A is the possible loading area of the cement concrete specimen, which is approximately taken as the cross-sectional area in the loading direction of the triaxial cavity of the conventional triaxial testing machine

d is the inner diameter of the triaxial cavity; k is the compressive strength of a cement concrete cylindrical specimen with a diameter of d and a height of 2d

Proportional coefficient with cement concrete compressive strength grade f _c

$k=\frac{0.352\mathrm{\γ}}{1-1.645{\mathrm{\δ}}_{\mathrm{\α}}}{[1+d/50]}^{1/2}+\frac{0.704\mathrm{\γ}}{1-1.645{\mathrm{\δ}}_{\mathrm{\α}}}$ Formula (2)

Among them, γ is the proportional coefficient, and δ _a is the statistical analysis value of the coefficient of variation. For specific values, see the index value table of concrete axial compressive strength (Fig. —Principle and Application. China Architecture and Building Press, 2004, p32, Table 3-2).

1.2, according to the compressive strength grade f _c of cement concrete, determine the confining pressure p=αf _c (0≤α≤1) of the conventional triaxial testing machine, and determine the range of the selected conventional triaxial testing machine by formula (3) Whether R _s is suitable, if it is suitable, execute 1.3, otherwise go to 1.2;

20%·R _s ≤(k·f _c +p)·A≤80%·R _s formula (3)

1.3. According to the inner diameter d of the triaxial cavity of the conventional triaxial testing machine, determine the size (diameter d _cy , height h) of the cement concrete cylinder specimen used in the material testing machine and triaxial testing machine and make the gradation of the cement concrete specimen The maximum crushed stone particle size d _s requires that the diameter d _cy <d of the cement concrete cylinder specimen used in the material testing machine and the conventional triaxial testing machine, the height is h=2d _cy , and the maximum crushed stone particle size d _s < d _cy /3;

1.4. Calculate the actual loading area of the specimen according to the determined specimen size of the material testing machine and conventional triaxial testing machine And check whether the formula (1) and formula (3) are satisfied, if it is satisfied, go to step 1.5, otherwise go back to step 1.3 to reselect the size of the test piece and the maximum particle size of the crushed stone;

1.5. Determine the diameter d _h of the Hopkinson compression bar of the test equipment, requiring d _h >6d _s , and determine the dimensions (diameter d _hs , height h _hs ) and height of the cylindrical specimen used for the Hopkinson compression bar test For h _hs >3d _s , the diameter is 6d _s <d _h <d _sh .

The second step is to determine the gradation data, water-cement ratio and sand content of cement concrete.

2.1. Determine the water-cement ratio W/C according to the strength grade f _c of cement concrete and formula (4)

$\frac{W}{C}=\frac{0.46\&CenterDot;k_c\&CenterDot;R_c^b}{f_c+0.2392\&Center\; Dot;k_c\&CenterDot;R_c^b}$ Formula (4)

in, is the grade of cement, and _kc is the surplus coefficient of the grade of cement, which is taken as 1.13 under normal conditions.

2.2, according to the maximum particle size of the determined gravel, the national standard JGJ53-92 "Quality Standard and Inspection Method for Gravel or Pebble for Ordinary Concrete" and the national standard JGJ52-92 "Quality Standard and Inspection Method for Ordinary Concrete Sand" select cement concrete gradation data and sand content data h _s .

2.3. Taking the determined sand content data and water-cement ratio data as the center point, adjust the water-cement ratio and sand content ratio by 0.05 and 1%, and obtain three sets of cement concrete ratio data, namely (W/ C, h _s ), (W/C+0.05, h _s +1%) and (W/C-0.05, h _s -1%); according to the three sets of ratio data, three cement concrete standard cubes were made for each group Test piece (150×150×150mm ³ ), according to GB/T50081-2002 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete", after curing for 28 days, measure the compressive strength of 9 standard cubic test pieces on a material testing machine, and the ratio of each group The compressive strength index of the cement concrete corresponding to the data is the average value of the compressive strength test results of the three standard cubic specimens of the cement concrete with the ratio data, and the average value of the compressive strength is the closest to the compressive strength index of the cement concrete to be studied The proportion data of the final gradation data, that is, the final sand content rate data and water-cement ratio data that meet the compressive strength index are obtained.

In the third step, according to the final grading data, sand content data and water-cement ratio data, a plate of cement concrete is stirred, and a cylindrical specimen with a diameter of d _cy and a height of h=2d _cy is made for the material testing machine, Triaxial testing machine test; make a cylindrical specimen with diameter d _hs and height h _hs for Hopkinson compression bar test.

In the fourth step, according to GB/T50081-2002 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete", after curing all kinds of specimens for 28 days, the prepared specimens can be used to determine the parameters of cement concrete dynamic constitutive model tests.

Adopt the present invention can reach following beneficial effect:

1. The present invention is under the situation that test determines cement concrete dynamic constitutive model parameter, proposes a kind of preparation method of cement concrete scientific research specimen. It ensures that the test pieces used in the material testing machine, the conventional three testing machines and the Hopkinson compression bar not only have the same cement concrete compressive strength grade, but also meet the requirements of the respective test equipment.

2. The present invention effectively solves the problem of differences in cement concrete compressive strength grades, water-cement ratios, gradation data, etc. in the test pieces of different test equipment in the process of determining the parameters of the cement concrete dynamic constitutive model, ensuring that the test The parameters of the dynamic constitutive model of cement concrete obtained from the test piece are scientific and reasonable, which reduces the human error in the process of making the test piece.

Description of drawings

Fig. 1 is the flow chart of making cement concrete scientific research specimen;

Figure 2 The index values of concrete axial compressive strength;

Figure 3C25 final mix ratio of concrete specimens;

Figure 4C25 Final dimensions of concrete specimens;

Figure 5C35 final mix proportion of concrete specimen;

Figure 6C35 Final dimensions of concrete specimens;

Figure 7C45 final mix proportion of concrete specimen;

Figure 8C45 Final dimensions of concrete specimens;

Figure 9C25 cement concrete mix ratio selection one;

Figure 10C25 Cement concrete mix ratio option 2;

Figure 11C25 cement concrete mix ratio selection three;

Fig. 12C25 cement concrete mix ratio selects the compressive strength grade test results of a standard specimen;

Fig. 13C25 Cement concrete mix ratio selects the compressive strength grade test results of the second standard specimen;

Figure 14C25 Cement concrete mix ratio selection of three standard test pieces of compressive strength grade test results.

Detailed ways

Fig. 1 is the flow chart of the present invention making cement concrete scientific research specimen.

The first step is to determine the size of the specimen and the range of the material testing machine and the conventional triaxial testing machine used for the material testing machine, the conventional triaxial testing machine (that is, the triaxial testing machine in which the test specimen is a cylinder) and the Hopkinson bar .

1.1. Determine the compressive strength grade f _c of the cement concrete to be studied according to the needs of scientific research, and determine the working range R of the material testing machine to be used by formula (1);

1.2, according to the compressive strength grade f _c of cement concrete, determine the confining pressure p=αf _c (0≤α≤1) of the conventional triaxial testing machine, and determine the range of the selected conventional triaxial testing machine by formula (3) Whether R _s is suitable, if it is suitable, execute 1.3, otherwise go to 1.2;

1.3. According to the inner diameter d of the triaxial cavity of the conventional triaxial testing machine, determine the size (diameter d _cy , height h) of the cement concrete cylinder specimen used in the material testing machine and triaxial testing machine and make the gradation of the cement concrete specimen The maximum crushed stone particle size d _s requires that the diameter d _cy <d of the cement concrete cylinder specimen used in the material testing machine and the conventional triaxial testing machine, the height is h=2d _cy , and the maximum crushed stone particle size d _s < d _cy /3;

并检验是否满足公式（1）和公式（3），若满足进入1.5步，否则回到1.3步重新选择试件尺寸和最大碎石粒径；1.4. Calculate the actual loading area of the specimen according to the determined specimen size of the material testing machine and conventional triaxial testing machine

And check whether the formula (1) and formula (3) are satisfied, if it is satisfied, go to step 1.5, otherwise go back to step 1.3 to reselect the size of the test piece and the maximum particle size of the crushed stone;

1.5. Determine the diameter d _h of the Hopkinson compression bar of the test equipment, requiring d _h >6d _s , and determine the dimensions (diameter d _hs , height h _hs ) and height of the cylindrical specimen used for the Hopkinson compression bar test For h _hs >3d _s , the diameter is 6d _s <d _h <d _sh .

The second step is to determine the gradation data, water-cement ratio and sand content of cement concrete.

2.1. Determine the water-cement ratio W/C according to the strength grade f _c of cement concrete and formula (4).

2.2, according to the maximum particle size of the determined gravel, the national standard JGJ53-92 "Quality Standard and Inspection Method for Gravel or Pebble for Ordinary Concrete" and the national standard JGJ52-92 "Quality Standard and Inspection Method for Ordinary Concrete Sand" select cement concrete gradation data and sand content data h _s .

2.3. Taking the determined sand content data and water-cement ratio data as the center point, adjust the water-cement ratio and sand content ratio by 0.05 and 1%, and obtain three sets of cement concrete ratio data, namely (W/ C, h _s ), (W/C+0.05, h _s +1%) and (W/C-0.05, h _s -1%); according to the three sets of ratio data, three cement concrete standard cubes were made for each group Test piece (150×150×150mm ³ ), according to GB/T50081-2002 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete", after curing for 28 days, measure the compressive strength of 9 standard cubic test pieces on a material testing machine, and the ratio of each group The compressive strength index of the cement concrete corresponding to the data is the average value of the compressive strength test results of the three standard cubic specimens of the cement concrete with the ratio data, and the average value of the compressive strength is the closest to the compressive strength index of the cement concrete to be studied The ratio data is the final ratio data, that is, the final sand content ratio data and water-cement ratio data that meet the compressive strength index are obtained.

In the third step, according to the final grading data, sand content data and water-cement ratio data, a plate of cement concrete is stirred, and a cylindrical specimen with a diameter of d _cy and a height of h=2d _cy is made for the material testing machine, Triaxial testing machine test; make a cylindrical specimen with diameter d _hs and height h _hs for Hopkinson compression bar test.

In the fourth step, after curing for 28 days in accordance with GB/T50081-2002 "Standards for Test Methods of Mechanical Properties of Ordinary Concrete", the prepared specimens can be used for the determination of parameters of cement concrete dynamic constitutive model tests.

The technical scheme proposed by the present invention can be used in principle to prepare cement concrete scientific research specimens with any compressive strength index. The University of National Defense Science and Technology has adopted the present invention to produce cement concrete that is mainly used for airport runways with compressive strength indexes of 25MPa, 35MPa and 45MPa respectively. For the scientific research test piece, see Figure 3 to Figure 8 for relevant parameters. The specific implementation plan will be described below by taking the production of a cement concrete scientific research test piece with a compressive strength index of 25MPa as an example.

The first step is to determine the size of the specimen used for the material testing machine, conventional triaxial testing machine and Hopkinson bar and the range of the material testing machine and conventional triaxial testing machine.

与水泥混凝土抗压强度等级f_c之间比例系数k＝1.29；根据公式（1）确定材料试验机工作量程R为200kN；1.1. Determine the compressive strength grade f _c of the cement concrete to be studied as 25MPa according to the needs of scientific research. Check the index value table of the concrete axial compressive strength to give the proportional coefficient γ=0.76 of the strength index 25MPa cement concrete, and the coefficient of variation Statistical analysis value δ _a =0.16; the inner diameter of the triaxial cavity of the selected conventional triaxial testing machine is 70mm, and the cross-sectional area A in the loading direction is 3848.45mm ² ; according to the formula (2), the diameter is 70mm and the height is 140mm The compressive strength of the cement concrete cylindrical specimen

The proportional coefficient k=1.29 between the compressive strength grade of cement concrete and _fc ; according to the formula (1), the working range R of the material testing machine is determined to be 200kN;

1.2. The compressive strength grade _fc of the cement concrete to be studied is 25MPa, and the confining pressure of the conventional triaxial testing machine is selected as 25MPa (α is taken as 1). According to the formula (3), the range R _s of the conventional triaxial testing machine is determined as 500kN;

1.3. The inner diameter of the three-axis cavity of the selected conventional triaxial testing machine is d=70mm, and the diameter of the cement concrete cylindrical specimen used for the material testing machine and the conventional triaxial testing machine is d _cy =50mm<d=70mm, and the height is h=100mm=2d _cy , the maximum gravel particle size d _s =16mm<d _cy /3=16.67mm.

直径为50mm高度为100mm的水泥混凝土圆柱体试件所具有的抗压强度

与水泥混凝土抗压强度等级f_c之间比例系数k＝1.24，满足公式（1）和公式（3）的不等式条件，进入1.5步。1.4. The size of the test piece used in material testing machine and conventional triaxial testing machine is a cylinder with diameter d _cy =50mm and height h=100mm. Actual loading area

The compressive strength of a cement concrete cylinder specimen with a diameter of 50 mm and a height of 100 mm

The proportional coefficient k=1.24 with the compressive strength grade of cement concrete _fc , satisfying the inequality conditions of formula (1) and formula (3), enter step 1.5.

1.5, the diameter of the Hopkinson compression bar is selected as d _h =120mm, satisfying d _h >6d _s =96mm, the size of the cylindrical specimen used for the Hopkinson compression bar test is diameter d _hs =100mm, height h _hs =50mm, satisfying the inequality conditions h _hs >3d _s and 6d _s <d _h <d _sh .

The second step is to determine the gradation data, water-cement ratio and sand content of cement concrete.

2.1. The cement selected is "Zhaoshan brand" 42.5 grade ordinary Portland cement produced by Hunan Cement Co., Ltd. of Zhaoshan Xinxing Group. The strength of the cement concrete to be studied is 25MPa. The water content of the cement concrete is calculated according to formula (4). The gray ratio W/C is 0.59.

2.2. In step 1.3, determine the maximum particle size of crushed stone d _s =16mm, according to the national standard JGJ53-92 "Quality Standard and Inspection Method of Gravel or Pebble for Ordinary Concrete" and the national standard JGJ52-92 "Quality Standard and Inspection of Ordinary Concrete Sand Method "The gradation data of selected cement concrete is particle size 16mm, dosage 7%; particle size 9.5mm, dosage 52%; particle size 4.75mm, dosage 41%; sand content h _s =35%.

2.3. Taking the sand content rate data and water-cement ratio data determined in 2.2 as the center point, adjust the water-cement ratio and sand content rate in the range of 0.05 and 1%, and obtain three sets of cement concrete ratio data, namely (35 %, 0.59), (36%, 0.64) and (34%, 0.54), see Figure 9 to Figure 11 for details; according to the three sets of ratio data, three cement concrete standard cube specimens (150×150× 150mm ³ ), according to GB/T50081-2002 "Standards for Test Methods of Mechanical Properties of Ordinary Concrete", after 28 days of curing, the strength of three cement concrete standard cube specimens with ratio data of (35%, 0.59) was measured on the material testing machine, and the result As shown in Figure 12, the average compressive strength is 31.0MPa; the ratio data measured on the material testing machine is (36%, 0.64) the strength of three cement concrete standard cube specimens, the results are shown in Figure 13, the average compressive strength The strength is 23.3MPa; the ratio data measured on the material testing machine is (34%, 0.54) the strength of three cement concrete standard cube specimens, the results are shown in Figure 14, the average compressive strength is 35.3MPa; the ratio data is (36%, 0.64) The average compressive strength of the cement concrete standard cube is 23.3MPa, which is the closest to the compressive strength index of the cement concrete to be studied, 25MPa. Therefore, the final proportion data is 36% sand content, and the water-cement ratio is 0.64.

The third step is based on the final grading data (particle size 16mm, dosage 7%; particle size 9.5mm, dosage 52%; particle size 4.75mm, dosage 41%), sand content rate data (36%) and Water-cement ratio data (0.64), mix a plate of cement concrete, make a cylindrical specimen with a diameter of d _cy =50mm and a height of h=2d _cy =100mm for material testing machine and triaxial testing machine test; the production size is A cylindrical specimen with diameter d _hs =100mm and height h _hs =50mm is used for the Hopkinson compression bar test.

The fourth step, in accordance with GB/T50081-2002 "Standards for Test Methods of Mechanical Properties of Ordinary Concrete", respectively test specimens with a size of φ50mm×100mm for material testing machines and triaxial testing machines and for Hopkinson compression bar tests After 28 days of curing for the specimens with a size of φ100mm×50mm, the specimens can be used for the determination of the parameters of the dynamic constitutive model of cement concrete.

Claims (2)

1. a preparation method of cement concrete scientific research specimen, is characterized in that comprising the following steps: The first step is to determine the test piece size and material testing machine, conventional triaxial testing machine range for material testing machine, conventional triaxial testing machine and Hopkinson bar, and said conventional triaxial testing machine means that the test specimen is A triaxial testing machine for a cylinder, the method is: 1.1. Determine the compressive strength grade f _c of the cement concrete to be studied according to the needs of scientific research, and determine the working range R of the material testing machine to be used by formula (1); 20% R≤k f _c A≤80% R Formula (1) Here, A is the possible loading area of the cement concrete specimen, which is approximately taken as the cross-sectional area in the loading direction of the triaxial cavity of the conventional triaxial testing machine d is the inner diameter of the triaxial cavity; k is the compressive strength of a cement concrete cylindrical specimen with a diameter of d and a height of 2d

Proportional coefficient with cement concrete compressive strength grade f _c $k=\frac{0.352\mathrm{\&gamma;}}{1-1.645{\mathrm{\&delta;}}_{\mathrm{\&alpha;}}}{[1+d/50]}^{1/2}+\frac{0.704\mathrm{\&gamma;}}{1-1.645{\mathrm{\&delta;}}_{\mathrm{\&alpha;}}}$ Formula (2) Among them, γ is the proportional coefficient, and δ _a is the statistical analysis value of the coefficient of variation. For the specific values, see the index value table of concrete axial compressive strength published in the document "Strength and Constitutive Relationship of Concrete-Principle and Application"; 1.2. According to the compressive strength grade f _c of cement concrete, determine the confining pressure p=αf _c of the conventional triaxial testing machine, 0≤α≤1, and determine the range R of the selected conventional triaxial testing machine by formula (3) Whether _s is suitable, if it is suitable, execute 1.3, otherwise go to 1.2; 20%·R _s ≤(k·f _c +p)·A≤80%·R _s formula (3) 1.3. Determine the size of the cement concrete cylinder specimen used in the material testing machine and triaxial testing machine according to the inner diameter d of the triaxial cavity of the conventional triaxial testing machine, that is, the diameter _dcy , the height h and the gradation of the cement concrete specimen The maximum crushed stone particle size d _s requires that the diameter d _cy <d of the cement concrete cylinder specimen used in the material testing machine and the conventional triaxial testing machine, the height is h=2d _cy , and the maximum crushed stone particle size d _s < d _cy /3; 1.4. Calculate the actual loading area of the specimen according to the determined specimen size of the material testing machine and conventional triaxial testing machine

And check whether the formula (1) and formula (3) are satisfied, if it is satisfied, go to step 1.5, otherwise go back to step 1.3; 1.5. Determine the diameter d _h of the Hopkinson compression bar of the test equipment, requiring d _h >6d _s , and determine the dimensions of the cylindrical specimen used for the Hopkinson compression bar test, namely the diameter d _hs and height h _hs , requiring h _hs >3d _s , 6d _s < d _h < d _sh ; The second step is to determine the gradation data, water-cement ratio and sand content of cement concrete: 2.1. Determine the water-cement ratio W/C according to the strength grade f _c of cement concrete and formula (4) $\frac{W}{C}=\frac{0.46\&Center\; Dot;k_c\&CenterDot;R_c^b}{f_c+0.2392\&Center\; Dot;k_c\&Center\; Dot;R_c^b}$ Formula (4) in,

is the grade of cement, k _c is the surplus coefficient of the grade of cement; 2.2, according to the maximum particle size of the determined gravel, the national standard JGJ53-92 "Quality Standard and Inspection Method for Gravel or Pebble for Ordinary Concrete" and the national standard JGJ52-92 "Quality Standard and Inspection Method for Ordinary Concrete Sand" select cement concrete The gradation data and sand content data h _s of 2.3. Taking the determined sand content data and water-cement ratio data as the center point, adjust the water-cement ratio and sand content ratio by 0.05 and 1%, and obtain three sets of cement concrete ratio data, namely (W/ C, h _s ), (W/C+0.05, h _s +1%) and (W/C-0.05, h _s -1%); according to the three sets of ratio data, three cement concrete standard cubes were made for each group The test piece, with a size of 150×150×150mm ³ , was cured for 28 days in accordance with GB/T50081-2002 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete", and the compressive strength of 9 standard cubic test pieces was measured on a material testing machine. The compressive strength index of the cement concrete corresponding to the ratio data is the average value of the compressive strength test results of the three standard cube specimens of the cement concrete with the ratio data, and the average value of the compressive strength is the closest to the compressive strength of the cement concrete to be studied The ratio data of the index is the final gradation data, that is, the final sand content data and water-cement ratio data that meet the compressive strength index are obtained; In the third step, according to the final grading data, sand content data and water-cement ratio data, a plate of cement concrete is stirred, and a cylindrical specimen with a diameter of d _cy and a height of h=2d _cy is made for the material testing machine, Triaxial testing machine test; make a cylindrical specimen with diameter d _hs and height h _hs for Hopkinson compression bar test; The fourth step is to cure all kinds of test pieces for 28 days according to GB/T50081-2002 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete". 2. The preparation method of a kind of cement concrete research specimen as claimed in claim 1, characterized in that said _kc is 1.13.

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