KR102556219B1 - Method of Comparison of concrete compressive strength by parameters of apartment building finishing materials using ultrasonic wave velosity test - Google Patents

Abstract

A method for comparing concrete compressive strength by parameter of apartment finishing materials using an ultrasonic speed test according to an embodiment is to prepare concrete specimens having a design compressive strength of 21 MPa and a width, length, and thickness of 500 cm, 500 cm, and 200 cm, respectively; Finishing a first finish sample, a second finish sample, and a third finish sample on the surface of each concrete specimen; Collecting a core of the first finish sample, a core of the second finish sample, and a core of the third finish sample from the concrete specimens on which each of the finish samples is finished through a core collector; measuring ultrasonic velocities of the cores of the first finished sample, the cores of the second finished sample, and the cores of the third finished sample, respectively, through an ultrasonic velocity test; calculating an estimated compressive strength through the measured ultrasonic velocities of each of the core of the first finished sample, the core of the second finished sample, and the core of the third finished sample; Measuring the compressive strength of the cores of the first finished sample, the cores of the second finished sample, and the cores of the third finished sample, respectively, through a compressive strength test; and the calculated estimated compressive strengths of each of the core of the first finish sample, the core of the second finish sample, and the core of the third finish sample and the core of the first finish sample, the core of the second finish sample , and comparing the error rate by comparing the measured compressive strength of the core of the third finished sample.

Description

{Method of Comparison of concrete compressive strength by parameters of apartment building finishing materials using ultrasonic wave velosity test}

The present invention relates to a method for comparing concrete compressive strength by parameter of apartment finishing materials using an ultrasonic speed test.

Regarding Class 1 and 2 facilities in Korea, it is stipulated in the 「Special Act on Facility Maintenance and Management」 to conduct periodic and detailed safety inspections, and companies registered as safety inspection businesses are required to perform safety inspections.

According to the Korea Society of Structure Diagnosis and Maintenance Engineering, as the facility safety inspection market grows by about 14% annually, related companies are entering the market en masse. This is an increasing situation.

According to a survey conducted by the National Land Safety and Security Agency, it was found that the insolvency rate for apartment buildings was the highest among facilities, and low-priced orders accounted for the highest rate as the cause of insolvency. In the case of precise safety inspection and precise safety diagnosis, the on-site rebound hardness method is required to be performed in the concrete durability evaluation item of the facility, but in the case of an apartment complex, it is difficult to conduct a non-destructive test due to dust and noise generated during experiments and people's actual residence. Inspections are made every time in the common area and underground parking lot, and poor inspections are inevitable because the experiment is conducted on the finishing material, not on the concrete surface due to low-priced orders.

In order to respond to low-priced orders for apartment houses and solve poor inspections, the present invention selects finishing materials mainly used in apartment houses and estimates the compressive strength according to the variables of the finishing materials by directly utilizing the rebound hardness method without removing the finishing materials. You want to develop your skills.

Registered Patent No. 10-2190604 (Registration date: 2020.12.09) is a method for manufacturing concrete specimens used for early age, concrete, compressive strength, and early age, concrete's compressive strength. A method of manufacturing a "concrete" specimen, which is a test piece for early predictive evaluation, and a method of predicting the compressive strength of concrete at an early age by a non-destructive test method using the "concrete" specimen manufactured by the above manufacturing method, curing during manufacture of a "concrete" specimen After curing and hardening the concrete by mixing an accelerator or quick-setting agent, the hardened concrete is subjected to a non-destructive test to early predict and evaluate the compressive strength of concrete on the 28th day, which is a general age, as in the present application. The technique of estimating the compressive strength using the rebound hardness method directly on the finishing material without removing the finishing material is not disclosed at all.

Registered Patent No. 10-2190604 (registration date: 2020.12.09)

Accordingly, one embodiment was invented to eliminate the above problems, and by selecting finishing materials mainly used in apartment houses and directly applying the rebound hardness method to the finishing materials without removing the finishing materials, the compressive strength estimation technology according to the variables of the finishing materials It was completed as the technical task with the main focus.

The above tasks are not limited to the technical tasks mentioned above, and other technical tasks not mentioned will be clearly understood by those skilled in the art from the description below.

A method for comparing concrete compressive strength by parameter of apartment finishing materials using an ultrasonic speed test according to an embodiment for solving the above problems is a concrete having a design compressive strength of 21 MPa and a width, length, and thickness of 500 cm, 500 cm, and 200 cm, respectively. Manufacturing specimens; Finishing a first finish sample, a second finish sample, and a third finish sample on the surface of each concrete specimen; Collecting a core of the first finish sample, a core of the second finish sample, and a core of the third finish sample from the concrete specimens on which each of the finish samples is finished through a core collector; measuring ultrasonic velocities of the cores of the first finished sample, the cores of the second finished sample, and the cores of the third finished sample, respectively, through an ultrasonic velocity test; calculating an estimated compressive strength through the measured ultrasonic velocities of each of the core of the first finished sample, the core of the second finished sample, and the core of the third finished sample; Measuring the compressive strength of the cores of the first finished sample, the cores of the second finished sample, and the cores of the third finished sample, respectively, through a compressive strength test; and the calculated estimated compressive strengths of each of the core of the first finish sample, the core of the second finish sample, and the core of the third finish sample and the core of the first finish sample, the core of the second finish sample , and comparing the error rate by comparing the measured compressive strength of the core of the third finished sample.

The calculated estimated compressive strengths of each of the core of the first finish sample, the core of the second finish sample, and the core of the third finish sample and the core of the first finish sample, the core of the second finish sample, And after the step of comparing the error rate by comparing the measured compressive strength of the core of the third finish sample, selecting a finish sample finished with the core of the finish sample having the lowest error rate as a low error rate finishing material. there is.

The first finish sample may include a pattern coat, the second finish sample may include a bone tile, the third finish sample may include a water-based paint, and the low error rate finish may include the water-based paint.

Other embodiment specifics are included in the detailed description and drawings.

According to the above-described embodiment, it is possible to provide a compressive strength estimation technology according to the variables of the finishing material by selecting a finishing material mainly used in an apartment house and directly utilizing the rebound hardness method on the finishing material without removing the finishing material.

Effects according to the embodiments are not limited by the contents exemplified above, and more various effects are included in this specification.

1 is a flowchart of a method for comparing concrete compressive strength by parameter of an apartment finishing material using an ultrasonic speed test according to an embodiment.
2 is a perspective view of a concrete test body according to an embodiment.
3 is a perspective view showing that a first finishing sample is finished on the surface of a concrete test specimen.
4 is a cross-sectional view of a concrete test body finished with a first finished sample according to FIG. 3;
5 is a perspective view showing that a second finishing sample is finished on the surface of a concrete specimen.
6 is a cross-sectional view of a concrete test body finished with a second finishing sample according to FIG. 5;
7 is a perspective view showing that a third finishing sample is finished on the surface of a concrete specimen.
8 is a cross-sectional view of a concrete test body finished with a third finished sample according to FIG. 7 .
Figure 9 is a schematic diagram showing the preparation of the core of the first finished sample.
Figure 10 is a schematic diagram showing the preparation of the core of the second finished sample.
Figure 11 is a schematic diagram showing the preparation of the core of the third finished sample.
12 is a schematic diagram showing a step of measuring the ultrasonic velocity of the core of the first finished sample taken through an ultrasonic velocity test.
13 is a schematic diagram showing a step of measuring the ultrasonic velocity of the core of the second finished sample taken through an ultrasonic velocity test.
14 is a schematic diagram showing a step of measuring the ultrasonic velocity of the core of the third finished sample collected through an ultrasonic velocity test.
FIG. 15 is an enlarged cross-sectional view of area A of FIG. 12 .
FIG. 16 is an enlarged cross-sectional view of area B of FIG. 12 .
FIG. 17 is an enlarged cross-sectional view of area A of FIG. 13 .
FIG. 18 is an enlarged cross-sectional view of area A of FIG. 14 .

Hereinafter, with reference to the accompanying drawings, the configuration of one embodiment and the resulting actions and effects will be collectively described.

Advantages and features of one embodiment, and a method of achieving them, will become clear with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, an embodiment is not limited to the embodiment disclosed below, and may be implemented in various different forms, but this embodiment only makes the disclosure of an embodiment complete, and is common in the art to which an embodiment belongs. It is provided to fully inform the knowledgeable person of the scope of the invention, and one embodiment is only defined by the scope of the claims. And like reference numerals designate like elements throughout the specification.

1 is a flowchart of a method for comparing concrete compressive strength by parameter of an apartment finishing material using an ultrasonic speed test according to an embodiment.

A method for comparing concrete compressive strength by parameter of apartment finishing materials using an ultrasonic speed test according to an embodiment includes the steps of manufacturing concrete specimens having a design compressive strength of 21 MPa and width, length, and thickness of 500 cm, 500 cm, and 200 cm, respectively ( S10), finishing the first finish sample, the second finish sample, and the third finish sample on the surface of each concrete test specimen (S20), each of the finish samples from the finished concrete test specimens through the core collector Taking the core of the first finish sample, the core of the second finish sample, and the core of the third finish sample (S30), the core of the first finish sample, the core of the second finish sample, and the Measuring the ultrasonic velocity of the core of the third finished sample through an ultrasonic velocity test (S40), each of the core of the first finished sample, the core of the second finished sample, and the core of the third finished sample Calculating the estimated compressive strength through the measured ultrasonic velocity (S50), the core of the first finished sample, the core of the second finished sample, and the core of the third finished sample were collected through a compressive strength test, respectively. Measuring the compressive strength (S60) of the estimated compressive strengths of each of the core of the first finished sample, the core of the second finished sample, and the core of the third finished sample and the first finished sample It may include comparing error rates by comparing the measured compressive strengths of the core, the core of the second finished sample, and the core of the third finished sample (S70).

Hereinafter, with reference to FIGS. 2 to 18 in addition to FIG. 1, a method for comparing concrete compressive strength for each parameter of an apartment finishing material using an ultrasonic speed test according to an embodiment will be described in more detail.

2 is a perspective view of a concrete test body according to an embodiment. 3 is a perspective view showing that a first finishing sample is finished on the surface of a concrete test specimen. 4 is a cross-sectional view of a concrete test body finished with a first finished sample according to FIG. 3; 5 is a perspective view showing that a second finishing sample is finished on the surface of a concrete specimen. 6 is a cross-sectional view of a concrete test body finished with a second finishing sample according to FIG. 5; 7 is a perspective view showing that a third finishing sample is finished on the surface of a concrete specimen. 8 is a cross-sectional view of a concrete test body finished with a third finished sample according to FIG. 7 . Figure 9 is a schematic diagram showing the preparation of the core of the first finished sample. Figure 10 is a schematic diagram showing the preparation of the core of the second finished sample. Figure 11 is a schematic diagram showing the preparation of the core of the third finished sample. 12 is a schematic diagram showing a step of measuring the ultrasonic velocity of the core of the first finished sample taken through an ultrasonic velocity test. 13 is a schematic diagram showing a step of measuring the ultrasonic velocity of the core of the second finished sample taken through an ultrasonic velocity test. 14 is a schematic diagram showing a step of measuring the ultrasonic velocity of the core of the third finished sample collected through an ultrasonic velocity test. FIG. 15 is an enlarged cross-sectional view of area A of FIG. 12 . FIG. 16 is an enlarged cross-sectional view of area B of FIG. 12 . FIG. 17 is an enlarged cross-sectional view of area A of FIG. 13 . FIG. 18 is an enlarged cross-sectional view of area A of FIG. 14 .

1 and 2, a step (S10) of manufacturing concrete test specimens 10 having a design compressive strength of 21 MPa and having a width, length, and thickness of 500 cm, 500 cm, and 200 cm, respectively, is performed. Each of the concrete test specimens 10 may have a design compressive strength of 21 MPa and width, length, and thickness of 500 cm, 500 cm, and 200 cm, respectively, but are not limited thereto.

In FIG. 2 , the first direction DR1 , the second direction DR2 , and the third direction DR3 are illustrated. The first direction DR1 , the second direction DR2 , and the third direction DR3 may cross each other. The first direction DR1 is the width direction of the concrete specimen 10, the second direction DR2 is the longitudinal direction of the concrete specimen 10, and the third direction DR3 is the thickness direction of the concrete specimen 10. can

1, 3 to 8, a step (S20) of finishing a first finish sample, a second finish sample, and a third finish sample on the surface of each concrete specimen is performed.

3 and 4 show a first finish sample 20, FIGS. 5 and 6 show a second finish sample 21, and FIGS. 7 and 8 show a third finish sample 22. are showing

The first finish sample 20 may include a pattern coat, the second finish sample 21 may include a bone tile, and the third finish sample 22 may include water-based paint.

Each of the first finishing sample 20, the second finishing sample 21, and the third finishing sample 22 may be completely finished on the surface of each concrete specimen 10. Each of the first finish sample 20, the second finish sample 21, and the third finish sample 22 may have different oil content and different surface roughness. For example, in terms of the amount of oil, the amount of oil may be decreased in the order of the first finish sample 20, the second finish sample 21, and the third finish sample 22, and also in terms of surface roughness, the first finish sample ( 20), the second finish sample 21, and the third finish sample 22 may have smaller surface roughness in that order.

Meanwhile, as shown in FIGS. 4, 6, and 8, each of the first finish sample 20, the second finish sample 21, and the third finish sample 22 has a predetermined thickness d1. can have Each of the first finish sample 20, the second finish sample 21, and the third finish sample 22 will be described later together while explaining the length of the core of the finish sample with respect to a predetermined thickness d1.

Then, referring to FIGS. 1 and 9 to 11, each of the finished samples (20, 21, 22) from the finished concrete specimens 10 through the core collector 100 of the first finished sample A step (S30) of collecting the core (S1), the core (S2) of the second finished sample, and the core (S3) of the third finished sample is performed.

The core of the first finish sample (S1) and the core of the second finish sample (S2) through the core extractor 100 from the concrete specimens 10 where each of the finish samples 20, 21, and 22 are finished. ), and in the step (S30) of collecting the core (S3) of the third finished sample, as shown in FIGS. 9 to 11, respectively, based on the core collector 100, the finished samples (20, 21 , 22) is located closest and the concrete specimen 100 is placed therein, the cores S1, S2, and S3 can be sampled. That is, in the process of calculating the estimated compressive strength through the ultrasonic speed test to be described later, the cores (S1, S2, and S3) as samples are not made of only the concrete specimen 100, as shown in FIGS. 9 to 11 , which includes even the finished samples 20, 21, and 22.

Typically, in measuring the compressive strength of the concrete specimen 10, the compressive strength may be measured with the finish sample finished on the surface of the concrete specimen 10 removed. In measuring the compressive strength of the existing concrete specimen 10, the reason for measuring the compressive strength with the finished sample finished on the surface of the concrete specimen 10 removed is that the finished sample is naturally of the concrete specimen 10. It was thought to have an effect on the compressive strength. However, it is not easy to remove the finishing sample (or finishing material) from the concrete specimen 10. For example, in the process of removing the finishing material, dust and noise are generated, and since a separate removal process must be accompanied, cost and time consumption are not small.

However, according to the concrete compressive strength comparison method for each parameter of apartment finishing materials using an ultrasonic speed test according to an embodiment, in general, in measuring the compressive strength of the concrete specimen 10, the surface of the concrete specimen 10 is finished. By measuring the compressive strength of the finished sample in a removed state, cost and time consumption can be greatly reduced because it is free from dust and noise generated in the process of removing the finishing material and does not involve a separate finishing material removal process. Preemptively, in order to measure the compressive strength with the finish sample finished on the surface of the concrete test object 10 removed, as in the present invention, to some extent the compressive strength of the concrete test object 10 for each finish material (or finish sample) There is a need to find out if the effect of

Subsequently, referring to FIGS. 1 and 12 to 14, the core (S1) of the first finished sample, the core (S2) of the second finished sample, and the core (S3) of the third finished sample were collected. A step (S40) of measuring the ultrasonic velocity through the ultrasonic velocity test is performed, respectively.

As shown in FIG. 12, the thickness d1 (or width d1) of the first finish sample 20 of the core S1 of the first finish sample taken, and the first finish sample 20 The length d2 of the excluded core S1 is shown. Further, the length h in the thickness direction of the core S1 is shown. For the step (S40) of measuring the smooth ultrasonic velocity, the thickness (d1) (or width (d1)) of the first finished sample 20 of the core (S1) of the first finished sample taken, and the first finish It is preferable that the sum of the lengths d2 of the core S1 excluding the sample 20 be about 3 to about 5 times the length h of the core S1 in the thickness direction. For example, the thickness d1 (or width d1) of the first finished sample 20 of the core S1 of the first finished sample taken, and the thickness of the core S1 excluding the first finished sample 20 The sum of the lengths (d2) is about 3 times or more than the length (h) in the thickness direction of the core (S1), so that the ultrasonic pulse (kHz) (about 24 kHz to about 150 kHz), the reliability of the ultrasonic speed test can be secured. That is, internal cracks or reinforcing bars may be additionally formed inside the core S1 of the first finish sample taken, and the first finish of the core S1 of the first finish sample taken The sum of the thickness d1 (or width d1) of the sample 20 and the length d2 of the core S1 excluding the first finished sample 20 is the length of the core S1 in the thickness direction ( h), there is an advantage in that the overall ultrasonic velocity of the core S1 can be calculated considering the internal uniformity or members such as reinforcing bars.

Furthermore, the thickness d1 (or width d1) of the first finished sample 20 of the core S1 of the first finished sample taken, and the core S1 excluding the first finished sample 20 The sum of the lengths d2 of is about 5 times or less than the length h of the core S1 in the thickness direction, thereby reducing the time and cost required for collecting the core S1.

Furthermore, the thickness d1 (or width d1) of the first finish sample 20 of the core S1 of the first finish sample taken is the core S1 excluding the first finish sample 20 It is preferably about 5% to about 10% of the length (d2) of . The thickness d1 (or width d1) of the first finish sample 20 of the core S1 of the first finish sample taken is the length of the core S1 excluding the first finish sample 20 ( By being about 5% or more of d2), it is possible to precisely determine whether or not the first finished sample 20 affects the compressive strength of the core S1 in the core S1, and The thickness d1 (or width d1) of the first finish sample 20 of the core S1 is about 10% or less of the length d2 of the core S1 excluding the first finish sample 20 As a result, since the length of the finishing material (or finishing sample) compared to the length of the entire concrete structure in an actual building (eg, apartment) is about 10% or less, conditions similar to the length of the finishing material compared to the length of the concrete structure in the actual building can be formed. There is an advantage to being able to

In the above, only the core (S1) with the first finished sample (20) has been described, but the same is true for the core (S2) of the second finished sample and the core (S3) of the third finished sample. Of course, it can be applied.

Measuring the ultrasonic velocity of each of the core (S1) of the first finished sample, the core (S2) of the second finished sample, and the core (S3) of the third finished sample through an ultrasonic velocity test (S40). ) As shown in FIGS. 12 to 14, it may be made through the oscillator 210, the receiver 220, and the control unit of the ultrasonic speed testing device. As shown in FIGS. 12 to 14 , the control unit may include a pulse generating circuit 230, a time measurement circuit 240, an amplifier 250, and a display unit 260. More specifically, a pulse (eg, about 24 kHz to about 150 kHz) generated by the pulse generator circuit 230 may be provided to the oscillator 210 . The pulse provided to the oscillator 210 may pass through each of the finished samples 20, 21, and 22 and additionally pass through the concrete test body 10 to be provided to the examiner 220. Information on the time at which the pulse generated from the oscillator 210 reaches the receiver 220 may be specified through the amplifier 250 and calculated through the time measurement circuit 240 .

In some embodiments, a zero correction method may be determined to use the ultrasonic velocity testing device. In order not to interfere with the display value from influencing factors, time delay adjustment is required. Time delay adjustment can be performed by connecting transducers (oscillator 210 and receiver 220 of FIGS. 12 to 14) in pairs to opposite surfaces of a reference bar whose transfer time is accurately known. A method of installing the transducers (oscillator 210 and transducer 220 of FIGS. 12 to 14) to the reference bar may always be constant. A minimum amount of contact medium is used and the transducer (oscillator 210 and receiver 220 in FIGS. 12 to 14) must be firmly pressed to the end of the bar. Sliding the transducer (oscillator 210 and receiver 220 in FIGS. 12 to 14) on the reference bar causes zero correction error and should be avoided. Furthermore, for accurate zero calibration of the ultrasonic speed test device, time delay adjustment is performed whenever the test device or transducer (oscillator 210 or receiver 220 in FIGS. 12 to 14) is replaced, or when cables with different lengths are used. It should run every time. In addition, it is necessary to recheck zero calibration from time to time to check the stability of electronic circuits or cables.

Meanwhile, as shown in FIG. 15, a separate first medium M11 is interposed between the oscillator 210 and the first finished sample 20. The first medium M11 may serve to smooth the contact of the oscillator 210 to the first finish sample 20 . As shown in FIG. 16, a separate second medium (M12) is interposed between the examiner 220 and the concrete test body 10. The second medium (M12) may serve to smooth the contact of the examiner 220 to the concrete test body 10.

As shown in FIG. 17, a separate first medium M21 is interposed between the oscillator 210 and the second finish sample 21. The first medium M21 may serve to smooth the contact of the oscillator 210 with the second finishing sample 21 .

As shown in FIG. 18, a separate first medium M31 is interposed between the oscillator 210 and the third finish sample 22. The third medium M31 may play a role of smooth contact of the oscillator 210 with the third finishing sample 22 .

As described above, each of the first finish sample 20, the second finish sample 21, and the third finish sample 22 may have different oil content and different surface roughness. For example, in terms of the amount of oil, the amount of oil may be decreased in the order of the first finish sample 20, the second finish sample 21, and the third finish sample 22, and also in terms of surface roughness, the first finish sample ( 20), the second finish sample 21, and the third finish sample 22 may have smaller surface roughness in that order. Accordingly, the amount of oil in the first medium M11 may be greater than the amount of oil in the first medium M21 and the amount of oil in the first medium M31, and the amount of oil in the first medium M21 is the amount of oil in the first medium M31. There can be more. The amount of oil in the first medium M11 may be greater than the amount of oil in the first medium M21 and the amount of oil in the first medium M31, and the amount of oil in the first medium M21 is greater than the amount of oil in the first medium M31 As a result, the oil content of the medium (M11, M21, M31) is adjusted according to the different oil content of the finished samples (20, 21, 22) to facilitate contact between the oscillator 210 and the finished samples (20, 21, 22) can play a role Furthermore, the viscosity of the first medium M11 may be greater than the oil content of the first medium M21 and the viscosity of the first medium M31, and the viscosity of the first medium M21 may be greater than that of the first medium M31. viscosity may be greater. The viscosity of the first medium M11 may be greater than the viscosity of the first medium M21 and the viscosity of the first medium M31, and the viscosity of the first medium M21 is greater than the viscosity of the first medium M31. As a result, the viscosity of the medium (M11, M21, M31) is adjusted according to the different surface roughness of the finished samples (20, 21, 22) so that the contact between the oscillator 210 and the finished samples (20, 21, 22) is smooth. can play a role in

Then, the estimated compressive strength is calculated through the measured ultrasonic velocities of each of the core (S1) of the first finished sample, the core (S2) of the second finished sample, and the core (S2) of the third finished sample Step S50 is performed. Calculating an estimated compressive strength through each measured ultrasonic velocity of the core (S1) of the first finished sample, the core (S2) of the second finished sample, and the core (S2) of the third finished sample ( S50), the core (S1) of the first finished sample, the core (S2) of the second finished sample, and the core (S3) of the third finished sample taken simultaneously with, before, or after A step (S60) of measuring the compressive strength through a compressive strength test is performed.

Then, the calculated estimated compressive strengths of each of the core S1 of the first finished sample, the core S2 of the second finished sample, and the core S3 of the third finished sample and the first finished sample Comparing error rates by comparing the measured compressive strengths of the core (S1) of the second finished sample (S2), and the core (S3) of the third finished sample (S70) is performed.

The measured ultrasonic velocity, the estimated compressive strength, and the first, respectively, of the core (S1) of the first finished sample, the core (S2) of the second finished sample, and the core (S2) of the third finished sample described above. The measured compressive strengths and error rates of the core of the finished sample (S1), the core of the second finished sample (S2), and the core of the third finished sample (S3) are shown in Table 1 below.

Specimen UPV
(m/s) Compressive
Strength
(MPa) Estimated compressive strength (MPa) (One) (2) (3) (4) (5) (6) Error Ratio (%) (One) (2) (3) (4) (5) (6) Core of unfinished sample 3,774 19.3 19.1 17.3 9.0 9.5 15.6 19.0 5.7 10.1 53.5 50.7 18.7 6.6 Core (S1) of the first finished sample 3,998 16.9 24.0 24.9 21.8 17.7 24.0 22.4 45.7 51.2 32.3 16.8 45.8 36.2 Core of the second finished sample (S2) 3,930 19.1 22.5 22.6 18.0 15.3 21.5 21.4 21.5 22.9 22.1 19.3 19.8 17.3 Core of the third finished sample (S3) 3,891 18.5 21.7 21.2 15.7 13.8 20.0 20.8 17.2 15.0 17.4 25.3 8.3 12.4 Average of error ratio - - 22.5 24.8 31.3 28.0 23.2 18.1 Estimation formula of compressive strength (Fc, MPa) by ultrasonic velocity (Vp, Km/s) (1) Fc = 21.5Vp - 62.0 (2) Fc = 33.91Vp - 110.7 (3) Fc = 56.974Vp- 206 (4) Fc = 36.72Vp - 129.077 (5) Fc= (372.7Vp - 1250.2)Х0.1 (6) Fc = (152Vp - 383.9 )Х0.1

Furthermore, the estimation formula of the compressive strength (MPa) through the ultrasonic velocity (Km/s) is as follows.

[Equation 1]

Fc = 21.5V - 62.0

[Equation 2]

Fc = 33.91V - 110.7

[Equation 3]

Fc = 56.974V- 206

[Equation 4]

Fc = 36.72Vp - 129.077

[Equation 5]

Fc= (372.7Vp - 1250.2)Х0.1

[Equation 6]

Fc = (152Vp - 383.9)Х0.1

Referring to Table 1, the conclusion of evaluating the reliability of the estimated compressive strength of concrete according to the type of finishing material using the ultrasonic speed test is as follows. When diagnosing a structure without removing the finishing material, it was confirmed that the error rate range of the compressive strength estimation formula using the previously proposed ultrasonic velocity method showed a wide range of fluctuation, ranging from 8.3% to 51.2%. In the case of the core (S1) of the first finished sample, the error was larger by 13.8% compared to the core of the unfinished sample, and in the case of the core (S2) of the second finished sample, the error was smaller than that of the core specimen of the unfinished sample by about 5.1%. all. In the case of the core (S3) of the third finished sample, the error was smaller by about 8.3% compared to the core of the non-finished sample. Among finishing materials, it was confirmed that finishing by painting (or water-based paint) did not affect the reliability of concrete compressive strength estimation.

Subsequently, a step of selecting a finished sample finished on the core of the finished sample having the lowest error rate as a low error rate finishing material may be further performed. According to Table 1, the low error rate finishing material may be the third finishing sample 22.

One embodiment described above has been described with reference to one embodiment shown in the drawings, but this is only exemplary, and those skilled in the art can make various modifications and equivalent other embodiments therefrom. point should be made clear. Therefore, the true technical protection scope of an embodiment should be interpreted according to the appended claims, and all technical ideas within the equivalent range should be construed as being included in the scope of rights of an embodiment.

10: Concrete test subject
20: first finish sample
21: second finish sample
22: third finish sample

Claims (3)

Manufacturing concrete specimens having a design compressive strength of 21 MPa and width, length, and thickness of 500 cm, 500 cm, and 200 cm, respectively;
Finishing a first finish sample, a second finish sample, and a third finish sample on the surface of each concrete specimen;
Collecting a core of the first finish sample, a core of the second finish sample, and a core of the third finish sample from the concrete specimens on which each of the finish samples is finished through a core collector;
measuring ultrasonic velocities of the cores of the first finished sample, the cores of the second finished sample, and the cores of the third finished sample, respectively, through an ultrasonic velocity test;
calculating an estimated compressive strength through the measured ultrasonic velocities of each of the core of the first finished sample, the core of the second finished sample, and the core of the third finished sample;
Measuring the compressive strength of the cores of the first finished sample, the cores of the second finished sample, and the cores of the third finished sample, respectively, through a compressive strength test; and
The calculated estimated compressive strengths of each of the core of the first finish sample, the core of the second finish sample, and the core of the third finish sample and the core of the first finish sample, the core of the second finish sample, and comparing the error rates by comparing the measured compressive strengths of the cores of the third finished samples;
The calculated estimated compressive strengths of each of the core of the first finish sample, the core of the second finish sample, and the core of the third finish sample and the core of the first finish sample, the core of the second finish sample, and comparing the error rates by comparing the measured compressive strengths of the cores of the third finished samples;
Further comprising selecting a finished sample finished on the core of the finished sample having the lowest error rate as a low error rate finishing material,
wherein the first finish sample comprises a pattern coat;
The second finish sample includes this tile,
The third finish sample includes water-based paint,
The low error rate finishing material includes the water-based paint,
The thickness d1 of the first finishing sample 20 of the core S1 including the first finishing sample 20 taken, and the length d2 of the core S1 excluding the first finishing sample 20 The sum of ) is 3 to 5 times the length h in the thickness direction of the core S1,
The thickness d1 of the first finishing sample 20 of the core S1 including the first finishing sample 20 taken is the length of the core S1 excluding the first finishing sample 20 ( 5% to 10% of d2),
The thickness d1 of the second finishing sample 21 of the core S2 including the second finishing sample 21 taken, and the length d2 of the core S2 excluding the second finishing sample 21 The sum of ) is 3 to 5 times the length h in the thickness direction of the core S2,
The thickness d1 of the second finishing sample 21 of the core S2 including the second finishing sample 21 taken is the length of the core S2 excluding the second finishing sample 21 ( 5% to 10% of d2),
The thickness d1 of the third finishing sample 22 of the core S3 including the third finishing sample 22 taken, and the length d2 of the core S3 excluding the third finishing sample 22 The sum of ) is 3 to 5 times the length h in the thickness direction of the core S3,
The thickness d1 of the third finishing sample 22 of the core S3 including the third finishing sample 22 taken is the length of the core S3 excluding the third finishing sample 22 ( 5% to 10% of d2),
In the step of measuring the ultrasonic velocity of the core of the first finished sample, the core of the second finished sample, and the core of the third finished sample, respectively, through an ultrasonic velocity test,
The pulse generated from the pulse generator circuit 230 is provided to the oscillator 210,
The pulse provided to the oscillator 210 passes through each of the finished samples 20, 21, and 22 and additionally passes through each concrete test body 10 and is provided to the examiner 220,
Information on the time at which the pulse generated from the oscillator 210 reaches the receiver 220 is materialized through the amplifier 250 and calculated through the time measuring circuit 240 for each parameter of the apartment finishing material using the ultrasonic speed test. Method for Comparing Compressive Strength of Concrete.

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