CN114739809A - Method for detecting concrete compressive strength of thin-wall prefabricated part - Google Patents

Method for detecting concrete compressive strength of thin-wall prefabricated part Download PDF

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CN114739809A
CN114739809A CN202210537947.0A CN202210537947A CN114739809A CN 114739809 A CN114739809 A CN 114739809A CN 202210537947 A CN202210537947 A CN 202210537947A CN 114739809 A CN114739809 A CN 114739809A
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core sample
compressive strength
concrete
less
strength
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孙彬
李雪雪
毛诗洋
张晋峰
杨波
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China Construction And Research Institute Testing Center Co ltd
China Academy of Building Research CABR
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China Construction And Research Institute Testing Center Co ltd
China Academy of Building Research CABR
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N1/00—Sampling; Preparing specimens for investigation
    • G01N1/02—Devices for withdrawing samples
    • G01N1/04—Devices for withdrawing samples in the solid state, e.g. by cutting
    • G01N1/08—Devices for withdrawing samples in the solid state, e.g. by cutting involving an extracting tool, e.g. core bit
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N1/00—Sampling; Preparing specimens for investigation
    • G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
    • G01N1/286—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q involving mechanical work, e.g. chopping, disintegrating, compacting, homogenising
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N1/00—Sampling; Preparing specimens for investigation
    • G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
    • G01N1/286—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q involving mechanical work, e.g. chopping, disintegrating, compacting, homogenising
    • G01N2001/2873—Cutting or cleaving
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0001—Type of application of the stress
    • G01N2203/0003—Steady
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0014—Type of force applied
    • G01N2203/0016—Tensile or compressive
    • G01N2203/0019—Compressive
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0058—Kind of property studied
    • G01N2203/0069—Fatigue, creep, strain-stress relations or elastic constants
    • G01N2203/0075—Strain-stress relations or elastic constants
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/02—Details not specific for a particular testing method
    • G01N2203/0202—Control of the test
    • G01N2203/0212—Theories, calculations
    • G01N2203/0218—Calculations based on experimental data
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/02—Details not specific for a particular testing method
    • G01N2203/06—Indicating or recording means; Sensing means
    • G01N2203/067—Parameter measured for estimating the property
    • G01N2203/0676—Force, weight, load, energy, speed or acceleration

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  • Life Sciences & Earth Sciences (AREA)
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  • General Health & Medical Sciences (AREA)
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  • Immunology (AREA)
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  • Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)
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Abstract

The thickness of the thin-wall precast concrete member is generally less than 70mm, and the requirements that the diameter of a core sample test piece is not less than 70mm and the height-diameter ratio is 1 in JGJ/T384-2016 in the technical specification of concrete strength detection by a core drilling method cannot be met, so that the concrete compressive strength cannot be detected by the core drilling method specified by the existing standard. Based on the technical problem, the invention provides a method for detecting the compressive strength of the concrete of the thin-wall prefabricated part, which is used for estimating the concrete solid strength of the thin-wall prefabricated part with the thickness of less than 70mm by drilling a core sample test piece with the processing height-diameter ratio of less than 1 and carrying out a compressive strength test. The method provides a technical means for quality acceptance of the prefabricated part, and has important engineering practical significance for evaluating the quality and safety of the fabricated building.

Description

Method for detecting concrete compressive strength of thin-wall prefabricated part
Technical Field
The invention relates to the technical field of engineering quality detection, in particular to a method for detecting the concrete compressive strength of a thin-wall prefabricated part.
Background
The prefabricated concrete structure is formed by transporting prefabricated components produced in factories to a construction site and then assembling the prefabricated components in a reliable connection mode, and is a main structural form of a prefabricated building. With the continuous progress of production technology, novel precast concrete members have been widely used, in which laminated members such as steel bar truss laminated slabs and laminated shear walls have become the main types of precast members used in fabricated concrete structures. The thickness of the concrete of the prefabricated part of the superposed component is generally between 40mm and 70mm, and the superposed component belongs to a thin-wall prefabricated component. The mechanical property of the concrete is an important factor for evaluating the production quality of the prefabricated part, wherein the compressive strength is a common index for representing the mechanical property of the concrete at present.
At present, the detection method for the compressive strength of the concrete on site mainly comprises a rebound method, an ultrasonic rebound synthesis method, a pull-off method, a core drilling method and the like. When the resilience method and the ultrasonic resilience comprehensive method are used for detecting the concrete strength of the thin-wall member, the vibration caused by bounce impact cannot be completely eliminated, and the accuracy of a detection result is greatly reduced; the pull-off method needs to drill into the member in the thickness direction to a depth not less than 44mm, and the thickness of the thin-wall prefabricated member cannot meet corresponding requirements; according to the regulations of the existing standard JGJ/T384-one 2016, when the compressive strength of concrete is detected by a core drilling method, the height-diameter ratio of a core sample test piece is 1.0, and the diameter of the compressive core sample test piece is not less than 70mm and not less than 2 times of the maximum particle size of aggregate. However, the thickness of the thin-wall prefabricated part cannot meet the requirement of the size of the core sample test piece, so that the core drilling method provided by the existing standard cannot detect and evaluate the concrete strength of the thin-wall prefabricated part. From the analysis, the existing concrete compressive strength field detection method cannot be applied to concrete compressive strength detection of the thin-wall prefabricated part.
Invention patent CN1285508AA micro core sample method for detecting the compressive strength of concrete on site is provided, which comprises the following steps: 1-3 measuring areas are arranged at the measured position, 10 micro concrete core samples with the diameter of 15-30mm are drilled in each measuring area by a core drilling machine, the core samples are processed into cylindrical test pieces with the height-diameter ratio of 1.0-2.0 by a grinding machine, and F is utilized according to the average value of the compressive strength of the test pieces in each measuring areacu.j＝A+B(fcor.j)m+C(fcor.j)m2And obtaining the concrete standard compressive strength representative value f of the measured part by using various relational expressionscu. However, first, this method has a core diameter of 15 to 30mm, and does not satisfy the condition that the ratio of the core diameter to the maximum particle diameter of the coarse aggregate should be more than 2. Secondly, the height-diameter ratio of the core sample specimen of the method is 1-2, and the method is not suitable for detecting and evaluating the concrete strength of the thin-wall prefabricated part.
Therefore, a method capable of effectively detecting the compressive strength of the concrete of the thin-wall prefabricated part is needed.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a method for detecting the concrete compressive strength of a thin-wall prefabricated part, and solves the problem that the field detection method for the concrete compressive strength in the prior art cannot be applied to the concrete compressive strength detection of the thin-wall prefabricated part.
The invention provides a technical scheme that: a method for detecting the compressive strength of concrete of a thin-wall prefabricated part comprises the steps of drilling a core sample test piece with the processing height-diameter ratio of less than 1, carrying out a compressive strength test, and calculating and estimating the compressive strength value of the concrete.
Preferably, the diameter and the height of the drilled core sample are determined according to the maximum particle size of the concrete aggregate and the size of the prefabricated part, then the core sample is drilled and cut, and the height-diameter ratio of the processed core sample test piece is more than or equal to 0.5 and less than 1.
Preferably, the determining the diameter and height of the drilled core sample according to the maximum particle size of the concrete aggregate and the size of the prefabricated part includes:
1) when the maximum grain diameter of the concrete aggregate is less than 30mm and the minimum thickness of the prefabricated part is 60-70 mm, drilling a core sample with the diameter of 100 mm;
2) when the maximum grain diameter of the concrete aggregate is less than 20mm and the minimum thickness of the prefabricated part is 40-60 mm, drilling a core sample with the diameter of 70 mm;
wherein, the height of the core sample is not less than 2 times of the maximum grain diameter of the concrete aggregate.
Preferably, the compressive strength test is carried out on the core sample specimen, and then the formula f is adoptedcu，cor，i＝βcFc，i/Ac，iCalculating the compressive strength value f of each core sample specimencu，cor，iWherein F isc，iThe breaking load of the compression test of the ith core sample specimen, Ac，iIs the compressive cross-sectional area, beta, of the ith core sample specimencThe conversion coefficient of the compression strength of the core sample specimen with the height-diameter ratio less than 1 and the standard specimen is obtained.
Preferably, the compression strength conversion coefficient beta of the core sample specimen with the height-diameter ratio smaller than 1 and the standard specimen is establishedcThe method comprises the following steps:
1) manufacturing not less than 5 concrete strength grade members, drilling and processing a standard test piece with the diameter of 100mm and the height-diameter ratio of 1 and a core sample test piece with the height-diameter ratio of less than 1 on each strength grade member, wherein the sampling number of the two test pieces is not less than 15 under each strength grade;
2) performing compressive strength tests on all standard test pieces and core sample test pieces, and calculating the average value f of the compressive strength of the standard test pieces under each strength gradecuAnd the average value f of the compressive strength of the core sample with the height-diameter ratio less than 1corAccording to fcu＝βcfcorThe least square method is used for grouping the average value f of the compressive strength of the core sample test piece with the aspect ratio less than 1 under j different strength gradescor，jThe mean value f of the compressive strength of the standard test piececu，jFitting to obtain a conversion coefficient betac。
Preferably, if detect single thin-walled member concrete intensity, effectual core appearance test piece quantity is no less than 3, if detect a batch of thin-walled member concrete intensity, effectual core appearance test piece quantity is no less than 12.
Preferably, the concrete compressive strength of the single thin-wall prefabricated part is detectedAverage value f of compressive strength values of compressive strength estimated value coring sample test piececu，cor，m。
Preferably, if the compressive strength of the concrete of a batch of thin-wall prefabricated parts is detected, the compressive strength estimation interval needs to be calculated, and the upper limit value of the interval is fcu，e1＝fcu，cor，m-k1scuThe lower limit of the interval is fcu，e2＝fcu，cor，m-k2scuWherein k is1And k2For an estimated coefficient associated with the number n of core samples, scuThe standard deviation of the compression strength value of the core sample specimen is shown.
Aiming at the defects of the prior art, the invention provides the method for detecting the compressive strength of the concrete of the thin-wall prefabricated part by drilling the core sample test piece with the height-diameter ratio smaller than 1, provides a technical means for quality acceptance of the thin-wall prefabricated part, fills the technical blank of effectively detecting the compressive strength of the concrete of the thin-wall prefabricated part, and has important engineering practical significance for evaluating the quality and the safety of the fabricated building.
The method is provided for determining the strength conversion relation of the core sample with the height-diameter ratio smaller than 1, so that the detection result is accurate and quick, and objective and accurate data support is provided for engineering quality acceptance.
Drawings
The foregoing will be more readily understood from the following description of exemplary embodiments of the invention taken in conjunction with the accompanying drawings, in which:
FIG. 1 shows an example of a core sample having a diameter of 70mm and an aspect ratio of 0.71 after processing.
FIG. 2 is a fitting curve diagram of the correlation between the compressive strength of the core sample specimen shown in FIG. 1 and the compressive strength of the standard specimen.
FIG. 3 shows an example of a core sample having a diameter of 100mm and an aspect ratio of 0.5 after machining.
FIG. 4 is a fitting curve diagram of the correlation between the compressive strength of the core sample specimen shown in FIG. 3 and the compressive strength of the standard specimen.
Detailed Description
The technical solutions of the present invention will be described in detail and clearly with reference to the accompanying drawings and specific embodiments, but the scope of the present invention is not limited thereto.
The terms are explained herein as follows:
core sample preparation: a cylindrical concrete sample, drilled from the prefabricated part, is called a core sample before it is uncut.
Core sample test piece: the core sample was cut to a predetermined height to form a test piece for a compressive strength test, which was referred to as a core sample test piece.
Standard test pieces: core specimen, 100mm in diameter and height, is referred to as a standard specimen.
The invention discloses a method for detecting the concrete compressive strength of a thin-wall prefabricated part, which comprises the following steps of drilling a core sample test piece with the processing height-diameter ratio of less than 1, carrying out a compressive strength test, and calculating and estimating the concrete compressive strength value:
s1, determining the diameter and height of a drilled core sample test piece according to the maximum particle size of concrete aggregate and the size of a prefabricated member, wherein the diameter and height of the drilled core sample test piece are limited by the thickness of a thin-wall member, the height of the core sample test piece cannot meet the requirements of the current specification, namely the thickness of the thin-wall prefabricated concrete member is less than 70mm, the core sample diameter which cannot meet the requirements of the current specification is not less than 70mm, and the height-diameter ratio is preferably 1, and the core sample size cannot be less than 2 times of the maximum particle size of the aggregate according to the existing research result, so that the height value of the core sample can only be taken between the maximum particle size of the aggregate which is 2 times and the thickness of the thin-wall member; the larger the core diameter, the smaller the dispersion of the compressive strength test results, so that the core sample having the largest diameter is used as far as possible under the allowable conditions, and the requirement of the aspect ratio of 0.5 or more, which is required in the present invention, is satisfied. The method comprises the following specific steps:
1) when the maximum grain diameter of the concrete aggregate is less than 30mm and the minimum thickness of the prefabricated part is 60-70 mm, drilling a core sample with the diameter of 100 mm;
2) when the maximum grain diameter of the concrete aggregate is less than 20mm and the minimum thickness of the prefabricated part is 40-60 mm, drilling a core sample with the diameter of 70 mm;
wherein, the height of the core sample is not less than 2 times of the maximum grain diameter of the concrete aggregate.
S2, determining the number of the core sample test pieces, wherein if the concrete strength of a single thin-wall member is detected, the number of effective core sample test pieces is not less than 3, and if the concrete strength of a batch of thin-wall members is detected, the number of effective core sample test pieces is not less than 12.
S3, selecting the height-diameter ratio of the core sample drilling pieces according to the diameter and the height determined in the step S1, and selecting the number of the core sample drilling pieces according to the step S2; the aspect ratio of the core sample specimen is preferably 0.5 or more and less than 1.
S4, carrying out a compression strength test on the core sample specimen obtained by drilling and processing in the S3, and carrying out a formula fcu，cor，i＝βcFc，i/Ac，iCalculating the compressive strength value f of each core sample specimencu，cor，i；
In the formula, Fc，iThe breaking load of the compression test of the ith core sample specimen, Ac，iIs the compressive cross-sectional area, beta, of the ith core sample specimencThe conversion coefficient of the compression strength of the core sample specimen with the height-diameter ratio less than 1 and the standard specimen is obtained.
Wherein, establishing the compression strength conversion coefficient beta of the core sample test piece with the height-diameter ratio less than 1 and the standard test piececThe method comprises the following steps:
1) manufacturing not less than 5 concrete strength grade members, drilling and processing a standard test piece with the diameter of 100mm and the height-diameter ratio of 1 and a core sample test piece with the height-diameter ratio of less than 1 on each strength grade member, wherein the sampling number of the two test pieces is not less than 15 under each strength grade;
2) performing compressive strength tests on all standard test pieces and core sample test pieces, and calculating the average value f of the compressive strength of the standard test pieces under each strength gradecuAnd the average value f of the compressive strength of the core sample with the height-diameter ratio less than 1corAccording to fcu＝βcfcorThe least square method is used for grouping the average value f of the compression strength of the core sample test piece with the height-diameter ratio less than 1 under j in different strength gradescor，jThe mean value f of the compressive strength of the standard test piececu，jFitting is carried out to obtain a conversion coefficient betac。
Wherein if the concrete strength of a single thin-wall component is detected, the average value f of the compressive strength values of the core sample test piececu，cor，mNamely the estimated value of the compressive strength;
if the strength of a batch of thin-wall member concrete is detected, calculating to give an estimated interval of the compressive strength, wherein the upper limit value of the interval is fcu，e1＝fcu，cor，m-k1scuThe lower limit of the interval is fcu，e2＝fcu，cor，m-k2scuWherein k is1And k2For the estimated coefficient correlated with the number n of core samples, the coefficient is obtained by looking up the table A.0.2 in appendix A of JGJ/T384-one 2016 technical Specification for concrete Strength detection by core drilling methodcuThe standard deviation of the compression strength value of the core sample specimen is shown.
And comparing the calculated estimation result of the compressive strength of the thin-wall prefabricated member concrete with the corresponding required value to realize the evaluation of the mechanical property of the prefabricated thin-wall member concrete for the fabricated building.
The method provides a new and effective technical means for quality acceptance of the thin-wall prefabricated part, and provides a method for performing a compressive strength test by drilling a core sample test piece with a machining height-diameter ratio smaller than 1, wherein the detection result is accurate and rapid, and the method has important engineering practical significance for evaluating the quality and safety of the fabricated building.
Example 1
The embodiment provides a method for detecting the compressive strength of a batch of thin-wall precast concrete, the maximum particle size of the concrete aggregate of the thin-wall precast concrete to be detected is less than 20mm, the minimum thickness of the precast concrete is 40-60 mm, the designed strength grade of the concrete is C30, and the method comprises the following steps:
s1, determining to drill a core sample test piece with the diameter of 70mm and the height of not less than 40mm according to the maximum particle size of the concrete aggregate and the size of the prefabricated part;
s2, the number of the core sample drilling test pieces is 15;
s3, selecting the height-diameter ratio to be 0.71, and processing the core sample specimen as shown in figure 1;
s4, carrying out a compressive strength test according to the formula fcu，cor，i＝βcFc，i/Ac，iCalculating the compressive strength value f of each core sample specimencu，cor，iThe 15 core sample specimens have compressive strengths of 42.0MPa, 44.5MPa, 42.9MPa, 43.3MPa, 44.3MPa, 39.3MPa, 43.4MPa, 41.6MPa, 41.9MPa, 43.3MPa, 42.0MPa, 41.0MPa, 41.9MPa, 41.1MPa and 39.9MPa, respectively;
wherein the conversion coefficient beta of the compressive strengthcThe fitted curve is shown in FIG. 2, i.e. βcThe value was 0.91.
Calculating the average value of the compressive strength of the core sample test piece to be 42.2MPa and the standard deviation to be 1.48 MPa; according to the number of the test pieces being 15, looking up the table A.0.2 in the JGJ/T384-one 2016 appendix A of the technical Specification for testing concrete strength by the core drilling method to obtain k1＝1.11397，k22.32898. The upper limit value and the lower limit value of the estimated interval of the concrete compressive strength of the thin-wall precast element of the embodiment are calculated to be 40.6MPa and 38.8MPa respectively. According to the requirements of the design drawing, the concrete design strength grade is C30, the lower limit value of the presumptive interval 38.8MPa is greater than the requirement (30MPa) of the design strength grade C30 on the compressive strength, so that the compressive strength of the concrete of the batch of thin-wall prefabricated parts meets the design requirement.
Example 2
The embodiment provides a method for detecting the concrete compressive strength of a single thin-wall prefabricated part, the maximum particle size of concrete aggregate of the thin-wall prefabricated part to be detected is 25mm, the minimum thickness of the prefabricated part is in the range of 60-70 mm, the designed strength grade of concrete is C50, and the method comprises the following steps of
S1, determining to drill a core sample test piece with the diameter of 100mm and the height of not less than 50mm according to the maximum particle size of the concrete aggregate and the size of the prefabricated part;
s2, the number of the core sample drilling test pieces is 3;
s3, selecting the height-diameter ratio to be 0.5, and processing the core sample specimen as shown in figure 3;
s4, carrying out a compressive strength test according to the formula fcu，cor，i＝βcFc，i/Ac，iCalculating the compressive strength value f of each core sample specimencu，cor，i(ii) a The compressive strength of 3 core sample test pieces is 57.3MPa, 62.6MPa and 61.6M respectivelyPa。
Wherein the compressive strength conversion coefficient betacThe fitted curve is shown in FIG. 4, i.e. βcThe value was 0.75.
The average value of the compressive strength of the core sample test piece is calculated to be 60.5MPa, and the estimated value of the compressive strength of the concrete of the thin-wall prefabricated part in the embodiment is 60.5 MPa. According to the requirements of design drawings, the concrete design strength grade is C50, the concrete compressive strength estimation value of 60.5MPa is greater than the requirement (50MPa) of the design strength grade C50 on the compressive strength, so that the concrete compressive strength of the single thin-wall prefabricated part meets the design requirement.
The thickness of the thin-wall precast concrete member is generally less than 70mm, and the requirements that the diameter of a core sample test piece is not less than 70mm and the height-diameter ratio is 1 in JGJ/T384-2016 of the technical specification for detecting the concrete strength by a core drilling method cannot be met, so that the concrete compressive strength cannot be detected by the core drilling method specified by the current standard. Aiming at the problem that the prior art can not detect the solid strength of the assembled prefabricated thin-wall component with the thickness of only 40-70 mm, the invention provides a method for detecting the concrete compressive strength of the thin-wall prefabricated component by drilling a test piece with the processing height-diameter ratio smaller than 1 core sample, thereby filling the blank of the prior detection technology. The inspection method is convenient and quick, has small destructiveness, and provides technical support for quality acceptance of the thin-wall prefabricated part for the fabricated concrete building.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (8)

1. A method for detecting the compressive strength of concrete of a thin-wall prefabricated part is characterized in that a core sample test piece with the processing height-diameter ratio of less than 1 is drilled, a compressive strength test is carried out, and the compressive strength value of the concrete is calculated and estimated.
2. The method according to claim 1, wherein the diameter and height of the drilled core sample are determined according to the maximum particle size of the concrete aggregate and the size of the prefabricated part, then the core sample is drilled and cut, and the height-diameter ratio of the processed core sample specimen is more than or equal to 0.5 and less than 1.
3. The method of claim 2, wherein determining the diameter and height of the drilled core sample comprises:
1) when the maximum grain diameter of the concrete aggregate is less than 30mm and the minimum thickness of the prefabricated part is 60-70 mm, drilling a core sample with the diameter of 100 mm;
2) when the maximum grain diameter of the concrete aggregate is less than 20mm and the minimum thickness of the prefabricated part is 40-60 mm, drilling a core sample with the diameter of 70 mm;
wherein, the height of the core sample is not less than 2 times of the maximum grain diameter of the concrete aggregate.
4. A method according to any one of claims 1 to 3, characterized in that the core specimen is subjected to a compression strength test in accordance with the formula fcu，cor，i＝βcFc，i/Ac，iCalculating the compressive strength value f of each core sample specimencu，cor，iWherein F isc，iThe breaking load of the compression test of the ith core sample specimen, Ac，iIs the compressive cross-sectional area, beta, of the ith core sample specimencThe conversion coefficient of the compression strength of the core sample specimen with the height-diameter ratio less than 1 and the standard specimen is obtained.
5. The method according to claim 4, wherein the compression strength conversion factor β of the core sample specimen having the aspect ratio of less than 1 and the standard specimen is establishedcThe method comprises the following steps:
1) manufacturing members with not less than 5 concrete strength grades, drilling and processing a standard test piece with the diameter of 100mm and the height-diameter ratio of 1 and a core sample test piece with the height-diameter ratio of less than 1 on the member with each strength grade, wherein the sampling number of the two test pieces under each strength grade is not less than 15;
2) all the standard test pieces and the core sample test pieces were subjected to a compressive strength test,calculating the average value f of the compressive strength of the standard test piece under each strength gradecuAnd the average value f of the compressive strength of the core sample with the height-diameter ratio less than 1corAccording to fcu＝βcfcorThe least square method is used for grouping the average value f of the compressive strength of the core sample test piece with the aspect ratio less than 1 under j different strength gradescor，jWith the mean value f of the compressive strength of the standard test piececu，jFitting to obtain a conversion coefficient betac。
6. The method according to claim 5, wherein the number of effective core sample pieces is not less than 3 if the strength of concrete of a single thin-walled member is tested, and not less than 12 if the strength of concrete of a batch of thin-walled members is tested.
7. The method as claimed in claim 6, wherein if the concrete compressive strength of the single thin-wall prefabricated member is detected, the average value f of the compressive strength values of the core sample specimen is taken as the estimated compressive strength valuecu，cor，m。
8. The method as claimed in claim 6, wherein if the compressive strength of the concrete of the thin-walled prefabricated parts is detected, the compressive strength estimation interval is calculated, and the upper limit value of the interval is fcu，e1＝fcu，cor，m-k1scuThe lower limit of the interval is fcu，e2＝fcu，cor，m-k2scuWherein k is1And k2For an estimated coefficient, s, associated with the number n of core samplescuAnd the standard deviation of the compressive strength value of the core sample test piece is shown.
CN202210537947.0A 2022-05-17 2022-05-17 Method for detecting concrete compressive strength of thin-wall prefabricated part Pending CN114739809A (en)

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Publication number Priority date Publication date Assignee Title
CN117074164A (en) * 2023-06-08 2023-11-17 广州市盛通建设工程质量检测有限公司 Dry-hard concrete detection method and system for water conservancy construction site

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117074164A (en) * 2023-06-08 2023-11-17 广州市盛通建设工程质量检测有限公司 Dry-hard concrete detection method and system for water conservancy construction site

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