A mix design method suitable for PET fiber concrete

Abstract

The present invention relates to the technical field of civil engineering material preparation, and in particular to a mix design method suitable for PET fiber concrete. The compressive strength, splitting tensile strength and slump value of PET fiber concrete are determined according to engineering requirements, and then a relationship model between the compressive strength, splitting tensile strength and slump value of PET fiber concrete and the corresponding performance of ordinary concrete is established. The influence of PET fiber volume dosage and length on concrete performance is considered. When some parameters of PET fiber concrete are known, the compressive strength of ordinary concrete can be calculated, and then the water-binder ratio can be determined; the water consumption is determined after the slump value of PET fiber concrete is converted into the slump value of ordinary concrete; the sand ratio is determined according to relevant conditions, and finally the amount of each component is calculated by a formula. The present invention accurately reflects the influence of fiber characteristics on concrete performance, improves the accuracy of mix design, provides reliable performance expectations for engineering applications, and promotes the development of PET fiber concrete technology.

Description

Technical Field

[0001] The invention relates to the technical field of civil engineering material preparation, in particular to a mix ratio design method suitable for PET fiber concrete. Background Art

[0002] In the field of civil engineering, concrete is an important and widely used building material. Polyethylene terephthalate (PET) fiber concrete has been gradually used in projects such as roads, bridges and tunnels because of its advantages such as enhancing the durability, crack resistance and toughness of concrete. PET fiber is usually made from recycled materials such as recycled waste plastic bottles. Compared with other fibers, it has certain advantages in resource consumption.

[0003] However, the current PET fiber concrete has deficiencies in mix design. The existing "Ordinary Concrete Mix Design Code" (JGJ 55-2011) does not fully consider the influence of fiber characteristic parameters (such as volumetric content and length) on the basic properties of concrete (such as fluidity, compressive strength and splitting tensile strength) when designing the mix of PET fiber concrete. This leads to the fact that in actual projects, the actual performance of PET fiber concrete mix designed according to traditional methods often deviates greatly from the design target.

[0004] This deviation may cause a series of problems, such as insufficient concrete strength affecting the safety of engineering structures and inappropriate fluidity leading to construction difficulties. Therefore, a mix design method suitable for PET fiber concrete is proposed to address the above problems. Summary of the invention

[0005] The object of the present invention is to provide a mix design method suitable for PET fiber concrete to solve the problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A mix design method suitable for PET fiber concrete comprises the following steps:

[0008] Step S1: Determine the compressive strength of PET fiber concrete according to engineering requirements , splitting tensile strength and slump value ;

[0009] Step S2: Establishing the compressive strength of PET fiber concrete , splitting tensile strength and slump value Compared with the compressive strength of ordinary concrete , splitting tensile strength and slump value The relationship model:

[0010] Step S2-1: Ordinary concrete compressive strength Compressive strength of PET fiber concrete The relationship between them satisfies the formula ;in, and are the influence coefficients of PET fiber volume content and length on the compressive strength of PET fiber concrete;

[0011] Step S2-2: Splitting tensile strength of ordinary concrete Splitting tensile strength of PET fiber concrete The relationship between them satisfies the formula ;in, and are the influence coefficients of PET fiber volume content and length on the splitting tensile strength of PET fiber concrete;

[0012] Step S2-3, slump value of ordinary concrete Slump value of PET fiber concrete The relationship between them satisfies the formula ,in, and are the influence coefficients of PET fiber volume content and length on the slump value of PET fiber concrete;

[0013] Step S3: known compressive strength of PET fiber concrete , PET fiber volume content and length , according to the formula Calculating the compressive strength of ordinary concrete , according to the compressive strength of ordinary concrete , cement strength grade , Cement Richness Factor and the gravel regression coefficient and , determine the water-binder ratio The formula should be satisfied:

[0014] ;

[0015] in, It is the measured value of the 28d mortar compressive strength of cementitious materials. ;

[0016] Step S4: Slump value of known PET fiber concrete , according to the formula Calculating the slump value of ordinary concrete ,when When the water-binder ratio is in the range of 0.40-0.80, the maximum nominal particle size of the crushed stone Divided into 4 levels t, when When t=0; when When t=1; when When t=2; when When t=3, the water consumption per cubic meter of PET fiber concrete It should be determined according to the following formula;

[0017] ;

[0018] in, , when the value range of S is 10-30, K=0, when the value range of S is 30-50, K=1, when the value range of S is 50-70, K=2, when the value range of S is 70-90, K=3, when the value range of S is 90-110, K=4, when the value range of S is 110-130, K=5, when the value range of S is 130-150, K=6, when the value range of S is 150-170, K=7, is the slump value of ordinary concrete;

[0019] Step S5: When the ordinary concrete When the water-binder ratio is in the range of 0.40-0.70, the sand ratio It should be determined as follows: ,in, is the maximum nominal particle size of crushed stone;

[0020] Step S6, calculating the components of PET fiber concrete according to the following formula: in, , , , , The calculation of the amount of cementitious materials, coarse aggregate, fine aggregate, water and PET fiber per cubic meter of PET fiber concrete is as follows: is the assumed mass of each cubic meter of PET fiber concrete, which is taken as 2350 kg / m 3 -2450 kg / m 3 .

[0021] As a preferred solution, in step S2-1, and The following relationship exists:

[0022] ;

[0023] ;

[0024] in, and Here, v is the volume content of PET fiber, l is the length of PET fiber, and the value range of v is 0-0.75%, and the value range of l is 6-19 mm.

[0025] As a preferred solution, in step S2-2, and The following relationship exists:

[0026] ;

[0027] ;

[0028] Among them, the range of PET fiber volume content v is 0-0.75%, and the length of PET fiber The value range is 6-19mm.

[0029] As a preferred solution, in step S2-3, and The following relationship exists:

[0030] ;

[0031] ;

[0032] Among them, the range of PET fiber volume content v is 0-0.75%, and the length of PET fiber The value range is 6-19mm.

[0033] As a preferred solution, in step S3, when the cement strength grade of ordinary concrete is When it is less than C60, the compressive strength is determined by the following formula:

[0034] ;

[0035] in, is the design strength of ordinary concrete, is the standard deviation of concrete strength, when , ;when , ;when , .

[0036] As a preferred solution, in step S3, when the cement strength grade of ordinary concrete is When it is less than C60, the water-cement ratio of concrete should be calculated as follows:

[0037] ;

[0038] in, is the 28d mortar compressive strength of cementitious materials, , .

[0039] It can be seen from the technical solution provided by the present invention that the present invention provides a mix design method suitable for PET fiber concrete, and the beneficial effects are as follows: the invention establishes a correlation model between the volume content and length of PET fiber and the compressive strength, splitting tensile strength and slump value of concrete. Through these models, the influence of the characteristic parameters of PET fiber on the basic properties of concrete can be accurately quantified, and the defect that the existing "Ordinary Concrete Mix Design Code" does not consider the influence of fiber characteristic parameters is overcome, and a scientific basis is provided for the performance prediction of PET fiber concrete. Based on the established correlation model, a slump, compressive strength and splitting tensile strength correction coefficient considering the volume content and length of PET fiber is proposed, and the mix ratio of concrete can be calculated more accurately, so that the designed mix ratio is more in line with the actual needs of the project. The method of the present invention is used for mix design, which can significantly reduce the errors of slump, compressive strength and splitting tensile strength. In the engineering design stage, engineers can accurately predict the various properties of PET fiber concrete according to the method of the present invention, thereby rationally designing the engineering structure and ensuring the quality of the project, which is helpful to standardize and optimize the mix design of PET fiber concrete, promote the promotion and application of this technology in the field of civil engineering, and promote technological progress in the industry. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0041] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with specific implementation methods.

[0042] The embodiment of the present invention provides a mix ratio design method applicable to PET fiber concrete, comprising the following steps:

[0043] Step S1: Determine the compressive strength of PET fiber concrete according to engineering requirements , splitting tensile strength and slump value ;

[0044] Step S2: Establishing the compressive strength of PET fiber concrete , splitting tensile strength and slump value Compared with the compressive strength of ordinary concrete , splitting tensile strength and slump value The relationship model:

[0045] Step S2-1: Ordinary concrete compressive strength Compressive strength of PET fiber concrete The relationship between them satisfies the formula ;in, and are the influence coefficients of PET fiber volume content and length on the compressive strength of PET fiber concrete, and The following relationship exists:

[0046] ;

[0047] ;

[0048] in, and Where v is the volume content of PET fiber, l is the length of PET fiber, and the value range of v is 0-0.75%, and the value range of l is 6-19 mm;

[0049] Step S2-2: Splitting tensile strength of ordinary concrete Splitting tensile strength of PET fiber concrete The relationship between them satisfies the formula ;in, and are the influence coefficients of PET fiber volume content and length on the splitting tensile strength of PET fiber concrete, and The following relationship exists:

[0050] ;

[0051] ;

[0052] Among them, the range of PET fiber volume content v is 0-0.75%, and the length of PET fiber The value range is 6-19mm;

[0053] Step S2-3, slump value of ordinary concrete Slump value of PET fiber concrete The relationship between them satisfies the formula ,in, and are the influence coefficients of PET fiber volume content and length on the slump value of PET fiber concrete, and The following relationship exists:

[0054] ;

[0055] ;

[0056] Among them, the range of PET fiber volume content v is 0-0.75%, and the length of PET fiber The value range is 6-19mm;

[0057] Step S3: known compressive strength of PET fiber concrete , PET fiber volume content and length , according to the formula Calculating the compressive strength of ordinary concrete , according to the compressive strength of ordinary concrete , cement strength grade , Cement Richness Factor and the gravel regression coefficient and , determine the water-binder ratio The formula should be satisfied:

[0058] ;

[0059] in, It is the measured value of the 28d mortar compressive strength of cementitious materials. ;

[0060] When the cement strength grade of ordinary concrete When it is less than C60, the compressive strength is determined by the following formula:

[0061] ;

[0062] in, is the design strength of ordinary concrete, is the standard deviation of concrete strength, when , ;when , ;when , ;

[0063] When the cement strength grade of ordinary concrete When it is less than C60, the water-cement ratio of concrete should be calculated as follows:

[0064] ;

[0065] in, is the 28d mortar compressive strength of cementitious materials, , ;

[0066] Step S4: Slump value of known PET fiber concrete , according to the formula Calculating the slump value of ordinary concrete ,when When the water-binder ratio is in the range of 0.40-0.80, the maximum nominal particle size of the crushed stone Divided into 4 levels t, when When t=0; when When t=1; when When t=2; when When t=3, the water consumption per cubic meter of PET fiber concrete It should be determined according to the following formula;

[0067] ;

[0068] in, , when the value range of S is 10-30, K=0, when the value range of S is 30-50, K=1, when the value range of S is 50-70, K=2, when the value range of S is 70-90, K=3, when the value range of S is 90-110, K=4, when the value range of S is 110-130, K=5, when the value range of S is 130-150, K=6, when the value range of S is 150-170, K=7, is the slump value of ordinary concrete. If fine sand is used, the amount of water per cubic meter of concrete is It can increase 5kg-10kg; when using coarse sand, it can reduce 5kg-10kg;

[0069] Step S5: When the ordinary concrete When the water-binder ratio is in the range of 0.40-0.70, the sand ratio It should be determined as follows: ,in, is the maximum nominal particle size of crushed stone;

[0070] At the same time sand rate The following formula should be satisfied:

[0071]

[0072] in, , and The amount of coarse aggregate, fine aggregate and PET fiber used in each cubic meter of PET fiber concrete is calculated respectively (kg / m 3 );

[0073] Step S6, calculating the components of PET fiber concrete according to the following formula: in, , , , , The calculation of the cementitious material, coarse aggregate, fine aggregate, water and PET fiber dosage (kg / m3) per cubic meter of PET fiber concrete is as follows: is the assumed mass of each cubic meter of PET fiber concrete (kg), which can be taken as 2350kg / m 3 -2450kg / m 3 .

[0074] The present invention will be described in further detail below in conjunction with specific embodiments:

[0075] Specific Example 1: PET fiber concrete mix ratio with designed compressive strength of 30 MPa

[0076] 1. Determine the performance target of PET fiber concrete

[0077] According to the actual needs of the project, the compressive strength of the PET fiber concrete designed this time needs to be determined. At the same time, considering the construction technology and work performance requirements, the slump value Set it in the range of 50mm-90mm. For the convenience of calculation example, the middle value is selected here ;

[0078] 2. Calculate the compressive strength of ordinary concrete

[0079] Based on the fiber characteristic parameters, it is assumed that the PET fiber volume content is selected , fiber length , this parameter is within the applicable range specified in the present invention (volume dosage of 0-0.75% and length range of 6-19 mm);

[0080] According to the calculation formula given by the present invention ,Will Substituting in, we get:

[0081]

[0082] According to Calculation formula ,Will Substituting in, we get:

[0083]

[0084] Finally, according to the compressive strength of ordinary concrete Compressive strength of PET fiber concrete The relationship formula , we can calculate:

[0085] (Keep two decimal places, more decimal places are kept in the calculation here to ensure accuracy);

[0086] 3. Determine the water-cement ratio

[0087] Considering the material properties and engineering conditions, it is assumed that the cement strength grade , cement richness factor , the gravel regression coefficient , ;

[0088] First, according to the formula Calculation of 28d mortar compressive strength of cementitious materials :

[0089]

[0090] Then according to the water-binder ratio calculation formula ,Will , And the correlation coefficient is substituted into the calculation:

[0091] (Keep three decimal places);

[0092] 4. Calculate the water consumption of PET fiber concrete

[0093] According to the present invention Calculation formula ,Will Substituting in, we get:

[0094]

[0095] According to Calculation formula ,Will Substituting mm into the equation:

[0096]

[0097] Then according to the slump value of ordinary concrete Slump value of PET fiber concrete The relationship formula , we can calculate:

[0098] mm (keep two decimal places);

[0099] Assuming the maximum nominal particle size of the crushed stone mm, and medium sand is used (based on actual conditions, if fine sand or coarse sand is used, the water consumption needs to be adjusted accordingly), refer to Table 1 provided by the present invention to determine the water consumption , can be obtained ;

[0100] Table 1 shows the water consumption of PET fiber concrete (kg / m 3 )

[0101]

[0102] 5. Determine the sand ratio

[0103] According to the sand rate calculation formula given by the present invention ,in, ;

[0104] First calculate (Keep two decimal places);

[0105] Substituting the above values ​​into the sand ratio calculation formula, we can get:

[0106] (Keep two decimal places);

[0107] 6. Calculate the amount of each component

[0108] Assumed mass per cubic meter of PET fiber concrete ;

[0109] Known , according to the density of PET fiber 1380kg / m 3 , first calculate the amount of PET fiber per cubic meter ,but , and then calculate:

[0110] (Keep two decimal places).

[0111] Specific Example 2: PET fiber concrete mix ratio with designed compressive strength of 35 MPa and high slump

[0112] 1. Determine the performance target of PET fiber concrete

[0113] Determine the compressive strength of PET fiber concrete according to project-specific requirements At the same time, in order to meet the high requirements for concrete fluidity during construction, the slump value Set in the range of 110mm-150mm, select As a calculation example;

[0114] 2. Calculate the compressive strength of ordinary concrete

[0115] Select the volume content of PET fiber ,length (all within the prescribed range);

[0116] according to The calculation formula is

[0117]

[0118] according to The calculation formula is Substituting in, we get:

[0119]

[0120] in accordance with Formula calculation :

[0121] (keep two decimal places);

[0122] 3. Determine the water-cement ratio

[0123] Assumed cement strength grade , cement richness factor , the gravel regression coefficient , ;

[0124] Calculate first ;

[0125] Then calculate according to the water-cement ratio formula:

[0126] (Keep three decimal places)

[0127] 4. Calculate the water consumption of PET fiber concrete

[0128] according to The calculation formula is Direct substitution gives:

[0129]

[0130] according to The calculation formula is Substituting in, we get:

[0131]

[0132] in accordance with Formula calculation :

[0133] (keep two decimal places);

[0134] Assuming the maximum nominal particle size of the crushed stone (Use medium sand), refer to Table 1 to determine the water consumption , can be obtained;

[0135] ;

[0136] 5. Determine the sand ratio

[0137] According to the sand ratio calculation formula, ;

[0138] Calculate first (keep two decimal places);

[0139] Substituting into the sand ratio calculation formula, we can get:

[0140] (keep two decimal places);

[0141] 6. Calculate the amount of each component

[0142] Assumptions ; Known , according to the density of PET fiber It is 1380kg / m3. First calculate the amount of PET fiber per cubic meter. ,but , and then calculate:

[0143] (Keep two decimal places).

[0144] Specific Example 3: PET fiber concrete mix ratio with designed compressive strength of 45 MPa, splitting tensile strength of 4.7 MPa and high slump;

[0145] Determine the compressive strength of PET fiber concrete according to project-specific requirements and splitting tensile strength At the same time, in order to meet the high requirements for concrete fluidity during construction, the slump value Set in the range of 110mm-150mm, select As a specific comparative example;

[0146] 2. Calculate the compressive strength of ordinary concrete

[0147] Select the volume content of PET fiber ,length (all within the prescribed range);

[0148] according to The calculation formula is Direct substitution gives:

[0149] ;

[0150] according to The calculation formula is Substituting in, we get:

[0151]

[0152] in accordance with Formula calculation :

[0153] (keep two decimal places);

[0154] 3. Calculation of splitting tensile strength of ordinary concrete

[0155] Select the volume content of PET fiber ,length (all within the prescribed range);

[0156] according to The calculation formula is Direct substitution gives:

[0157]

[0158] according to The calculation formula is Substituting in, we get:

[0159]

[0160] in accordance with Formula calculation :

[0161] (keep two decimal places);

[0162]

[0163] The ratio of splitting tensile strength to compressive strength is in the range of 1 / 9-1 / 18, so the design is based on ordinary concrete with a design compressive strength of 49.2MPa.

[0164] 3. Determine the water-cement ratio

[0165] Considering the material properties and engineering conditions, it is assumed that the cement strength grade , cement richness factor , the gravel regression coefficient , ;

[0166] First, according to the formula Calculation of 28d mortar compressive strength of cementitious materials :

[0167]

[0168] Then according to the water-binder ratio calculation formula ,Will , And the correlation coefficient is substituted into the calculation:

[0169] (keep two decimal places);

[0170] 4. Calculate the water consumption of PET fiber concrete

[0171] According to the present invention Calculation formula ,Will Direct substitution gives:

[0172]

[0173] According to Calculation formula ,Will Substituting in, we get:

[0174]

[0175] Then according to the slump value of ordinary concrete Slump value of PET fiber concrete The relationship formula , we can calculate:

[0176] (keep two decimal places);

[0177] Assuming the maximum nominal particle size of the crushed stone , and medium sand is used (based on actual conditions, if fine sand or coarse sand is used, the water consumption needs to be adjusted accordingly), refer to Table 1 provided by the present invention to determine the water consumption , can be obtained ;

[0178] 5. Determine the sand ratio

[0179] According to the sand rate calculation formula given by the present invention ,in, ;

[0180] First calculate (keep two decimal places);

[0181] Substituting the above values ​​into the sand ratio calculation formula, we can get:

[0182] ;

[0183] 6. Calculate the amount of each component

[0184] Assumed mass per cubic meter of PET fiber concrete ;

[0185] Known , according to the density of PET fiber It is 1380kg / m3. First calculate the amount of PET fiber per cubic meter. ,but , and then calculate:

[0186] (Keep two decimal places).

[0187] 7. Measured performance of PET fiber concrete

[0188] PET fiber concrete was tested according to the "Standard for Test Methods for Physical and Mechanical Properties of Concrete" (GB / T 50081-2019). The results showed that the measured compressive strength of PET fiber concrete was 45.1MPa, the measured splitting tensile strength was 4.7MPa, and the measured slump value was 100mm, which met the specific requirements of the project.

[0189] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A mix design method suitable for PET fiber concrete, characterized in that: The following steps are involved: Step S1: Determine the compressive strength of PET fiber concrete according to engineering requirements , splitting tensile strength and slump value ; Step S2: Establishing the compressive strength of PET fiber concrete , splitting tensile strength and slump value Compared with the compressive strength of ordinary concrete , splitting tensile strength and slump value The relationship model: Step S2-1: Ordinary concrete compressive strength Compressive strength of PET fiber concrete The relationship between them satisfies the formula ;in, and are the influence coefficients of PET fiber volume content and length on the compressive strength of PET fiber concrete, and The following relationship exists: ； ； in, and Where v is the volume content of PET fiber, l is the length of PET fiber, and the value range of v is 0-0.75%, and the value range of l is 6-19 mm; Step S2-2: Splitting tensile strength of ordinary concrete Splitting tensile strength of PET fiber concrete The relationship between them satisfies the formula ;in, and are the influence coefficients of PET fiber volume content and length on the splitting tensile strength of PET fiber concrete, and The following relationship exists: ； ； Step S2-3, slump value of ordinary concrete Slump value of PET fiber concrete The relationship between them satisfies the formula ,in, and are the influence coefficients of PET fiber volume content and length on the slump value of PET fiber concrete, and The following relationship exists: ； ； Step S3: known compressive strength of PET fiber concrete , PET fiber volume content and length , according to the formula Calculating the compressive strength of ordinary concrete , according to the compressive strength of ordinary concrete , cement strength grade , Cement Richness Factor and the gravel regression coefficient and , determine the water-cement ratio of ordinary concrete The formula should be satisfied: ； in, It is the measured value of the 28d mortar compressive strength of cementitious materials. ; Step S4: Slump value of known PET fiber concrete , according to the formula Calculating the slump value of ordinary concrete ,when When the water-binder ratio is in the range of 0.40-0.80, the maximum nominal particle size of the crushed stone Divided into 4 levels t, when When t=0; when When t=1; when When t=2; when When t=3, the water consumption per cubic meter of PET fiber concrete It should be determined according to the following formula; ； Among them, when When k=0, When k=1, When k=2, When k=3, When k=4, When k=5, When k=6, When k=7, is the slump value of ordinary concrete; Step S5: When the ordinary concrete When the water-binder ratio is in the range of 0.40-0.70, the sand ratio It should be determined as follows: ,in, is the maximum nominal particle size of crushed stone; Step S6, calculating the components of PET fiber concrete according to the following formula: in, , , , , The calculation of the amount of cementitious materials, coarse aggregate, fine aggregate, water and PET fiber per cubic meter of PET fiber concrete is as follows: is the assumed mass of each cubic meter of PET fiber concrete, which is taken as 2350 kg / m 3 -2450 kg / m 3 ; Known and , and then according to calculate , the density of PET fiber is known , calculate the amount of PET fiber per cubic meter ; Known ,Will , , and Substitution Medium Calculation , and finally by calculate , complete the calculation of the amount of each component in the PET fiber concrete mix ratio.

2. A mix design method suitable for PET fiber concrete according to claim 1, characterized in that: In step S3, when the cement strength grade of ordinary concrete is When it is less than C60, the compressive strength is determined by the following formula: ； in, is the design strength of ordinary concrete, is the standard deviation of concrete strength, when , ;when , ;when , .

3. A mix design method suitable for PET fiber concrete according to claim 2, characterized in that: In step S3, when the cement strength grade of ordinary concrete is When it is less than C60, the water-cement ratio of ordinary concrete should be calculated as follows: ； in, is the 28d mortar compressive strength of cementitious materials, , .

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