Method for detecting concrete strength by using combined core sample beam

Abstract

The invention discloses a method for detecting concrete strength by using a combined core sample beam. The method comprises the following steps: step S1, selecting concrete members and uniformly arranging the positions of the concrete members; s2, scanning the positions of stressed steel bars in the concrete member by using a steel bar scanner, and marking; s3, drilling a core sample of the concrete member needing to be detected through a core drilling instrument to obtain the core sample; step S4, carrying out polishing treatment on the core sample; s5, loading the polished core sample into a shaping steel sleeve to obtain the compressive strength of the core sample; and S6, obtaining the real strength of the entity structure through comprehensive evaluation. The method for detecting the concrete strength through the combined core sample bundle is simple and easy to implement, low in cost and small in difficulty, the damage to an original structure is small when a single core sample with the diameter of 20 mm is drilled, steel bars can be avoided more easily, stress main bars are prevented from being damaged, and due to the fact that the core samples are small in size, the application range of a core drilling method is expanded.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete strength detection, and particularly to a method for detecting concrete strength by using a combined core sample bundle. Background Art

[0002] As the most widely used and important building material, the safety of concrete structure buildings is closely related to the quality of concrete itself. How to control the quality of concrete in all aspects of production and use is an important issue for construction workers. At present, the in-situ detection methods for concrete strength include core drilling method, rebound method, ultrasonic-rebound combined method, pull-out method, artificial intelligence detection and other methods. In the daily inspection work of concrete building structures, it may be restricted by various factors and conditions and it is impossible or very difficult to drill large-diameter core samples that meet the requirements of current specifications. Moreover, many intractable problems encountered in practical work cannot be solved by large-diameter core samples.

[0003] Since the core drilling method requires sampling on the entity, it will inevitably cause certain damage to the component, and may even reduce the stress section and cut off the stressed steel bars. Therefore, the number and position of core samples are often restricted during the detection process. Especially for the inspection and appraisal of existing buildings involved in urban renewal, the most commonly used current inspection method is the core drilling method. However, the minimum core drilling diameter is 75mm, and the damage to the physical project and the impact on residential users after the detection are very large. Restoration also brings new problems at the same time. Therefore, it is very necessary to minimize the damage to existing buildings and accurately determine the compressive strength of concrete.

[0004] Through a large number of experimental studies, it is found that in order to reduce the damage caused by taking cores from the concrete structure entity, by reducing the core sample diameter, when the core sample diameter is reduced to 20mm, the discreteness of the direct measured compressive strength of the core sample is relatively large, and the strength of the in-situ concrete cannot be accurately determined, which does not meet the basic conditions for forming a detection method. Therefore, the method of using a combined core sample bundle for core sample bundle compressive testing is adopted to restore the original state of the compressive core sample to the greatest extent. Using a high-strength steel sleeve as an external restraint, a core sample bundle is composed of three core samples with a diameter of 20mm and a height of 100mm. The mechanical relationship between the three core samples and between the core sample and the sleeve is very clear. The concrete compressive strength is detected in a confined manner, which can greatly reduce the discreteness rate, is simple and easy to operate, has a low detection cost, and the core drilling sampling will not cause great damage to the original structure. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for detecting concrete strength by using a combined core sample bundle, which is simple and easy to operate, has a low cost and small difficulty. Drilling a single core sample with a diameter of 20mm causes less damage to the original structure, is more likely to avoid steel bars so as not to damage the stressed main bars, and due to the small size of the core sample, the application range of the core drilling method is expanded.

[0006] The present invention provides a method for detecting the strength of concrete by using a combined core sample bundle, comprising the following steps:

[0007] Step S1: Select a concrete member and uniformly arrange the position of the concrete member;

[0008] Step S2: Use a steel bar scanner to scan the position of the stressed steel bars in the concrete member and mark them;

[0009] Step S3: Drill core samples from the concrete member to be detected by a core drill to obtain core samples;

[0010] Step S4: Grind the core samples;

[0011] Step S5: Place the ground core samples into a shaped steel sleeve to obtain the compressive strength of the core samples;

[0012] Step S6: Obtain the true strength of the solid structure through comprehensive evaluation.

[0013] In step S6, the comprehensive evaluation formula is as follows:

[0014] f cu,cor = β c F c / A c ;

[0015]

[0016] f cu,e = f cu,cor,m - ks cu ;

[0017] f cu,cor Compressive strength value of the core sample bundle, accurate to 0.1 MPa; f cu,cor,m Average compressive strength of the core sample bundle, accurate to 0.1 MPa; f cu,cor,i Compressive strength value of a single group of core sample bundles, accurate to 0.1 MPa; f cu,e Presumed value of concrete compressive strength, accurate to 0.1 MPa; s cu Standard deviation of the compressive strength sample of the core sample bundle, accurate to 0.01 MPa; F c Failure load of the compressive test of the core sample bundle; A c Compressive cross-sectional area of the core sample bundle; β c Strength conversion coefficient of the core sample bundle; k presumed value coefficient; i number of core sample bundles.

[0018] Preferably, in step S3, the diameter of the core sample is 20 mm, the failure hole diameter of the core sample is 25 mm, and the height of the core sample is 100 mm.

[0019] Preferably, in step S3, the core drill takes one or two core samples each time, and the drilling depth each time does not exceed 200 mm.

[0020] Preferably, in step S4, the core sample after grinding treatment is a core sample with a height of 100 mm for standby.

[0021] Preferably, in step S5, the core samples are loaded into the sizing steel sleeve in groups of three. After installing the movable pressure plate, they are placed on an automatic press for automatic pressurization, and a pressure curve is formed in real time by a computer to finally obtain the compressive strength of the core samples.

[0022] Preferably, in step S5, the sizing steel sleeve includes a core sample sleeve, a rubber pad, and a movable pressure plate, and the model of the core sample sleeve is No. 45 steel.

[0023] Therefore, the method for detecting the concrete strength by using the above-mentioned combined core sample bundle in the present invention is simple and easy to implement, with low cost and small difficulty. Drilling a single core sample with a diameter of 20 mm causes less damage to the original structure, and it is easier to avoid steel bars so as not to damage the main stressed bars. Moreover, due to the small size of the core samples, the application range of the core drilling method is expanded.

[0024] Next, through the drawings and embodiments, the technical solutions of the present invention will be further described in detail. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is the overall flowchart of the method for detecting the concrete strength by using a combined core sample bundle in the present invention;

[0026] Figure 2 is the structural schematic diagram of the sizing steel sleeve of the method for detecting the concrete strength by using a combined core sample bundle in the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] The technical solutions of the present invention will be further described below through the drawings and embodiments.

[0028] Unless otherwise defined, the technical terms or scientific terms used in the present invention should have the ordinary meanings understood by those with ordinary skills in the field to which the present invention belongs.

[0029] In the present invention, words such as "first", "second" and similar words do not denote any order, quantity or importance, but are only used to distinguish different components. Words such as "comprising" or "including" mean that the elements or objects appearing before this word cover the elements or objects listed after this word and their equivalents, without excluding other elements or objects. Words such as "connected" or "coupled" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Upper", "lower", "left", "right", etc. are only used to represent relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0030] Embodiment 1

[0031] As Figure 1 - Figure 2 shown, a method for detecting the strength of concrete using a combined core sample bundle in the present invention includes the following steps:

[0032] Step S1: Before core drilling, select a certain number of components according to different building structure types and arrange the positions of each component as evenly as possible; select concrete components and arrange the positions of the concrete components evenly;

[0033] Step S2: Use a steel bar scanner to scan the positions of the stressed steel bars on the selected components and mark them on the selected components. Drill core samples at the positions where the steel bars are not damaged. Select the drilling depth according to the component size. Drill 1 or 2 core samples each time, and the drilling depth each time shall not exceed 2 core samples, that is, 200 mm;

[0034] Use a steel bar scanner to scan the positions of the stressed steel bars in the concrete components and mark them;

[0035] Step S3: Use a traditional core drill to take in-situ core samples from the concrete structure to be detected. The sampling diameter is 20 mm, the damaged hole diameter is 25 mm, and the core sample height is 100 mm;

[0036] Obtain core samples by drilling core samples from the concrete components to be detected through a core drill;

[0037] In step S3, the diameter of the core sample is 20 mm, the damaged hole diameter of the core sample is 25 mm, the height of the core sample is 100 mm. The core drill drills one or two core samples each time, and the drilling depth each time does not exceed 200 mm.

[0038] Step S4: Grind the core samples;

[0039] Ensure that the two end faces of the core sample are horizontal and smooth, without obvious damage or corner chipping. The ground core sample with a height of 100 mm is reserved for use.

[0040] Step S5: Load the processed core samples into the sizing steel barrel in groups of three. Place the movable pressure plate directly on the sleeve. After installing the movable pressure plate, place the sized steel sleeve as a whole on the automatic press for automatic pressurization and form a pressure curve in real time through a computer. The loading and pressurization process is continuous and uninterrupted, and the entire duration is approximately 0.5 - 3 minutes depending on the pressure. During the pressurization process, the computer will collect the pressure curve in real time.

[0041] Finally, obtain the compressive strength of the bundle of core samples; it can intuitively obtain the actual strength of the concrete structure, serving as basic data for projects such as reinforcement and renovation. Through this technology, it is possible to conduct strength tests on structural members of different sizes, with simple and easy operation, low testing costs, and relatively accurate test results. It can avoid the drawbacks of the existing specifications where the diameter of the cored core samples is relatively large, the requirements for the size of structural members are relatively strict, and the damage to the physical structure is relatively large.

[0042] Load the polished core samples into the sizing steel sleeve to obtain the compressive strength of the core samples.

[0043] The sizing steel sleeve includes a core sample sleeve, a rubber gasket, and a movable pressure plate. The model of the core sample sleeve is 45 steel.

[0044] In step S5, the core samples are loaded into the sizing steel sleeve in groups of three. After installing the movable pressure plate, place it on the automatic press for automatic pressurization, and form a pressure curve in real time through a computer to finally obtain the compressive strength of the core samples.

[0045] Step S6: After collecting and summarizing the compressive strength of each bundle of core samples, obtain the true strength of the physical structure through the comprehensive evaluation conversion formula.

[0046] The comprehensive evaluation formula is as follows:

[0047] f cu,cor =β c F c / A c ;

[0048]

[0049] f cu,e =f cu,cor,m -ks cu ;

[0050] f cu,cor The compressive strength value of the core sample bundle (MPa), accurate to 0.1 MPa; f cu,cor,m The average compressive strength of the core sample test bundle (MPa), accurate to 0.1 MPa; f cu,cor,i The compressive strength value of a single group of core sample test bundles (MPa), accurate to 0.1 MPa; f cu,eConcrete compressive strength estimation value (MPa), accurate to 0.1MPa; s cu Standard deviation of the compressive strength of the core specimen bundle (MPa), accurate to 0.01MPa; F c Failure load of the core specimen bundle compression test (N); A c The cross-sectional area of ​​the core specimen bundle in compression (mm2); β c Conversion factor for core sample bundle strength; k estimated value coefficient; i number of core sample bundle groups.

[0051] The true strength of the entity structure is obtained through comprehensive evaluation.

[0052] In step S6, the compressive strength of the core samples is collected and summarized, and the real strength of the entity structure is obtained through a comprehensive evaluation conversion formula.

[0053] Therefore, the present invention adopts the above-mentioned method of detecting concrete strength by a combined core sample bundle, which is simple and easy, low in cost and difficulty. Drilling a single core sample with a diameter of 20 mm causes less damage to the original structure, and is easier to avoid steel bars so as not to damage the main stress-bearing bars. Moreover, due to the small size of the core sample, it is more operable for small-sized concrete components, and the scope of use of the core drilling method is expanded. The detection method of the combined core sample bundle greatly improves the detection accuracy, avoids the problem of low accuracy of the currently used non-destructive testing method, and can provide a final judgment result for the structural entity strength. Two core samples are formed by drilling the core once, which can reduce the overall number of drilling holes, reduce the on-site workload, and improve work efficiency. The instruments, machinery, and appliances involved in the entire core drilling process, the core sample processing process, and the pressure test process are all mature products, and there is no high investment in new equipment. Moreover, the durability and reliability can be guaranteed, and long-term repeated tests can be carried out to achieve economic benefits.

[0054] The above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for testing concrete strength using a combined core sample bundle, characterized in that: The following steps are involved: Step S1, selecting concrete components and evenly arranging the positions of the concrete components; Step S2, using a steel bar scanner to scan the position of the stressed steel bars in the concrete component and mark them; Step S3, drilling a core sample from the concrete component to be inspected by using a core drill to obtain a core sample; Step S4, grinding the core sample; Step S5, placing the polished core sample into a shaped steel sleeve to obtain the compressive strength of the core sample; Step S6, obtaining the real strength of the entity structure through comprehensive evaluation; In step S6, the comprehensive evaluation formula is as follows: f cu,cor =b c F c / A c ; f cu,e =f cu,cor,m -ks cu ; f cu,cor The compressive strength value of the core sample bundle is accurate to 0.1MPa; f cu,cor,m The average compressive strength of the core sample bundle is accurate to 0.1MPa; f cu,cor,i The compressive strength value of a single core sample bundle is accurate to 0.1MPa; f cu,e Concrete compressive strength estimation value, accurate to 0.1MPa;s cu Standard deviation of the core specimen bundle compressive strength sample, accurate to 0.01MPa; F c Failure load of the core specimen bundle compression test; A c The compressive cross-sectional area of ​​the core specimen bundle; β c Conversion factor for core sample bundle strength; k estimated value coefficient; i number of core sample bundle groups.

2. A method for detecting concrete strength using a combined core sample bundle according to claim 1, characterized in that: In step S3, the diameter of the core sample is 20 mm, the destruction hole diameter of the core sample is 25 mm, and the height of the core sample is 100 mm.

3. The method for detecting concrete strength using a combined core sample bundle according to claim 1, characterized in that: In step S3, the core drill drills one or two core samples each time, and the drilling depth each time does not exceed 200 mm.

4. The method for detecting concrete strength using a combined core sample bundle according to claim 1, characterized in that: In step S4, the core sample after grinding is prepared as a core sample with a height of 100 mm.

5. The method for detecting concrete strength using a combined core sample bundle according to claim 1, characterized in that: In step S5, the core samples are loaded into a standard steel sleeve in groups of three, a movable pressure plate is installed, and the sleeve is placed on an automatic press for automatic pressurization. A pressure curve is formed in real time by a computer to finally obtain the compressive strength of the core samples.

6. The method for detecting concrete strength using a combined core sample bundle according to claim 1, characterized in that: In step S5, the shaped steel sleeve includes a core sample sleeve, a rubber pad and a movable pressure plate, and the model of the core sample sleeve is 45# steel.

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