JP2007240249A - Evaluating method of breakage caused by cutting processing of concrete, and cutting method of concrete based on the evaluation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an evaluating method that can quantitatively evaluate the degree of breakage by cutting, and can serve as a useful basis for selecting an appropriate cutting method according to the strength and property of concrete. <P>SOLUTION: The characteristic amount of a crack of a concrete cut part and the adhesion strength of repair/reinforcement material constructed in this cut part establish an associated relation, depending on the strength or material (mixed component) of the concrete. Therefore, data for evaluation where the characteristic amount of the crack generated by cutting is matched with the adhesion strength is previously stored, the surface of existing concrete is cut by repair/reinforcement engineering work, then a sample in the cut part is extracted, the characteristic amount of a crack existing in a smooth observation surface formed by cutting the existing concrete in the depth direction is measured, and the breakage by cutting the existing concrete is quantitatively evaluated by collating the measured data with the data for evaluation. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for quantitatively evaluating the degree of damage caused by a cutting process performed in repair / reinforcement work of a concrete structure, and a concrete cutting method based on the evaluation result.

  As a method of repairing and reinforcing concrete structures such as tunnel structures, bridge slabs and piers, pile foundations, underground structures, piers and revetments, dams and embankments, etc., the deteriorated parts of concrete are removed by cutting (cutting). Newly known methods such as transferring concrete and repairing / reinforcing materials are known. For the cutting process, a water jet method for cutting by water pressure, a breaker method or a spiky hammer method for cutting by attaching a cutting device to a large machine, or a manual cutting operation using an electric pick is adopted. .

Depending on the method of cutting treatment as described above, there is a problem that the existing concrete structure may be damaged, such as cracks, adversely affecting the adhesive properties between the existing concrete structure and the concrete that has been handed over. (For example, refer to Patent Document 1). However, at present, it is not performed to grasp the degree of damage caused by the cutting process and quantitatively evaluate the influence on the adhesion property after joining.
JP 2002-121901 A

  The present invention has been made in view of the problems as described above, and the technical problem is that the degree of damage due to cutting can be quantitatively evaluated, and depending on the strength and properties of the concrete. It is another object of the present invention to provide an evaluation method that can be a useful basis for selecting an appropriate cutting method, and to provide a method for cutting concrete with less damage based on the evaluation result.

  As a means for effectively solving the technical problems described above, the method for evaluating damage caused by the concrete cutting process of the present invention is to cut a surface of the existing concrete, and then sample a sample of the cut portion of the existing concrete. By collecting the sample and measuring the feature quantity of cracks existing on a smooth observation surface formed by cutting the sample in the depth direction of the existing concrete, and comparing the measurement data with the evaluation data, Quantitatively evaluate the damage caused by cutting, and the data for evaluation is the characteristic amount of cracks in the concrete cutting part measured in the same manner as described above, and the adhesion strength between the repaired / reinforcing material inherited in this cutting part. Are stored in association with each other. The repair / reinforcement material is, for example, concrete or mortar.

  That is, the feature amount of the crack at the concrete cutting location and the adhesion strength of the repair / reinforcement material inherited to this cutting location have a corresponding relationship depending on the strength and material (mixing component) of the concrete. For this reason, if database for evaluation is created by associating the characteristics of the cracks generated by cutting with the bond strength, a database will be created, and in the construction of repairing / reinforcing existing concrete structures, the degraded parts of the concrete will be removed. When cutting, a part of it is first cut experimentally, a sample of the cut portion is taken, and the characteristics of cracks existing on the smooth observation surface formed by cutting this sample in the depth direction of the existing concrete Since the amount of damage can be measured and the degree of damage to the concrete surface layer part can be quantitatively grasped by the correspondence with the adhesion strength by searching and collating the data for evaluation, an appropriate cutting method considering the required adhesion strength, etc. Can be used as a basis for selecting

  In the evaluation method of the present invention, the feature amount of the crack to be measured is at least one of the number, density, width, and length. In addition, if the sample is collected after applying protective mortar on the cut surface of the existing concrete and curing it, new cracks can be prevented from occurring during sample collection, processing, and mirror polishing. When the crack is measured, it is preferable that the observation surface is mirror-polished and a flaw detection liquid is applied to the observation surface.

  Further, the concrete cutting method according to the present invention cuts the surface of existing concrete to an appropriate depth by a mechanical cutting method selected based on the evaluation result by the above-described evaluation method, and then by a water jet method to a predetermined depth. To cut. In this case, examples of the machine cutting method that can be selected include a breaker method, a spiky hammer method, and a manual cutting method. In addition, the cutting depth by each method is calculated in consideration of data such as crack distribution, number, length, degree of progress, influence range, and maximum size of coarse aggregate.

  According to the evaluation method of the present invention, the degree of damage of the concrete surface layer portion caused by cutting can be quantitatively grasped in association with the adhesion strength with the repair / reinforcement material, so that the desired adhesion strength can be ensured. It is possible to select an appropriate cutting method and, in turn, a rational cutting method that matches the strength, construction site, and construction cost of the existing concrete.

  According to the cutting method of the present invention, first, after performing mechanical cutting that is large in damage to the existing concrete but low in cost, by adopting a water jet method that is high in cost but small in damage to the existing concrete. Finally, damage to the cutting surface can be reduced, and further, the construction period can be prolonged and the cost can be prevented from rising.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a flowchart showing a work flow in the present invention, FIG. 2 is a cross-sectional view showing a part of an existing concrete structure, and FIG. 3 is a state in which the surface of the existing concrete structure is cut (suspended). FIG. 4 is a sectional view showing a sample taken from a cutting point of an existing concrete structure, FIG. 5 is a perspective view showing the sample of FIG. 4, and FIG. 6 is a cutting of the existing concrete structure. FIG. 7 is an explanatory view showing a method for measuring the adhesion strength, and FIG. 8 is an explanatory view showing a method for selecting a cutting method.

  First, in FIG. 2, reference numeral 1 is an existing concrete structure to be repaired consisting of cement and sand concrete paste 11 and coarse aggregate 12, and 11 a is unhealthy due to deterioration or damage occurring in the surface layer of concrete paste 11. Part.

  The unhealthy portion 11a in the surface layer portion of the existing concrete structure 1 is first cut (suspended) by a method arbitrarily selected from a water jet method, a breaker method, a spiky hammer method, and the like (step S1). And by such a cutting process, as shown in FIG. 3, the crack 1b has generate | occur | produced in the surface layer part of the concrete structure 1 from the cutting surface 1a.

  Next, the protective mortar 13 is applied to the cutting surface 1a of the concrete structure 1 (step S2). The protective mortar 13 is applied for the purpose of preventing damage such as new cracks from occurring during sample collection, processing, and mirror polishing described later. Moreover, it is also possible to perform the below-mentioned adhesion strength test using this protective mortar 13.

  Next, in order to grasp the degree of damage of the concrete surface layer portion due to the cutting, a part of the concrete surface layer portion after the cutting is cut as shown by a broken line in FIG. 3, and the sample 10 as shown in FIG. Collect (step S3). In this case, it is desirable to collect a cylindrical core sample with a diameter of about 100 mm by core boring or a cubic sample with a side of about 100 mm by a concrete cutter. The cutting surface 1a is preliminarily coated with the protective mortar 13 as described above. However, when the concrete surface layer for cutting the sample 10 is cut, a new crack is generated. It is desirable to set the cutting speed and the like appropriately so that there is no problem.

  The collected sample 10 is divided into half (split) as shown in FIG. 5 to form a flat observation surface 10a (step S4). FIG. 5 shows a half-cut columnar core sample. The observation surface 10a of the sample 10 is mirror-polished so as to be easily observed to eliminate surface irregularities (step S5). Mirror polishing of the observation surface 10a is extremely effective for improving observation accuracy and reliability. Of course, care should be taken not to damage the observation surface 10a during the halving operation or polishing operation, and the cutting speed and polishing speed should be set appropriately.

  Next, a flaw detection liquid is applied to the observation surface 10a (step S6). The application of the flaw detection liquid soaks into fine cracks (microcracks) that cannot be visually observed and makes these microcracks clear, so that it is extremely effective in improving observation accuracy and reliability.

  Next, the observation surface 10a is observed at a magnification of about 50 to 100 times using a microscope (not shown), and the number, width, and length (development depth) of cracks (including microcracks) 1b generated near the cutting surface 1a. ) Is measured (step S7).

  Further, as shown in FIG. 6, the repair / reinforcement material 2 such as mortar is handed over to the cutting surface 1 a of the existing concrete structure 1, and after a predetermined curing period, the adhesion strength with the existing concrete structure 1 is increased. Measurement is performed (step S8), and the data is accumulated in a database of a personal computer (not shown) as evaluation data in which the state of the crack 1b measured in step S7 is associated with the adhesion strength (step S9).

  As a method of measuring the adhesion strength of the existing concrete structure 1 and the repair / reinforcing material 2 such as mortar that has been handed over to the cutting surface 1a, a sample 10 taken from the existing concrete structure 1 as shown in FIG. The repairing / reinforcing material 2 is applied to the cutting surface 1a with an appropriate layer thickness, and a steel jig 3 is joined thereto, and the repairing / reinforcing material 2 reaches a surface layer portion of the sample 10 with a certain size. A notch C having a thickness (for example, φ40 mm) is made, and a tensile load P is applied through the jig 3.

  When the data accumulated as described above is analyzed, as shown in FIG. 8A, depending on what cutting method is adopted, cracks (including microcracks) generated in the vicinity of the cutting surface are detected. The more the number of cracks (and the width and depth of progress), the more cracks that have occurred, the greater the damage caused by cutting. It can be seen that it tends to be lower than the tensile strength of 1. Moreover, there is a similar tendency with respect to the width of cracks and the depth of progress.

  Therefore, as shown in FIG. 8B, it is determined that it is appropriate to select the cutting method D or the cutting method E with a small degree of damage to the existing concrete in order to ensure the required adhesion strength s. Is done.

  However, in the case of the water jet method, for example, it is excellent in that there is little damage to the existing concrete, but the cost is significantly increased, such as using a large amount of water for cutting and treating the cutting water containing cement. To do. Therefore, with the exception of the parts where damage is expected to increase with respect to the cutting depth, a method that performs cutting with an easy and economical method, and performs the remaining cutting with a method that has little damage even at high cost. It is preferable to select a combination of rational cutting methods in consideration of the total cost required for cutting.

Table 1 below shows an example of the result of measuring the bond strength between the existing concrete and the repair / reinforcement material using the method shown in FIG. It is shown together.

Therefore, from the above test results, in order to reduce damage caused by cutting and ensure high adhesion strength and to reduce costs, when the cutting depth is 100 mm, for example, up to 80 mm is performed by the B method, and the remaining It is preferable to carry out 20 mm by the C method. This is because the maximum size of the coarse aggregate is generally about 20 mm, and the occurrence of microcracks is limited to the vicinity of the coarse aggregate on the surface. In addition, when securing an adhesive strength of 1.0 N / mm ² or more, it is preferable to implement a cutting depth of 100 mm by the B method unless cost reduction is considered.

It is a flowchart which shows the flow of the operation | work in this invention. It is sectional drawing which shows a part of existing concrete structure. It is sectional drawing which shows the state which cut | disconnected (hanging) the surface of the existing concrete structure. It is sectional drawing which shows the sample extract | collected from the cutting location of the existing concrete structure. It is a perspective view which shows the sample of FIG. It is sectional drawing which shows the state which handed over repair and reinforcement material to the cutting surface of the existing concrete structure. It is explanatory drawing which shows the measuring method of adhesion strength. It is explanatory drawing which shows the method of selecting a cutting method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Existing concrete structure 1a Cutting surface 1b Crack 10 Sample 10a Observation surface 11 Concrete paste 12 Coarse aggregate 2 Repair and reinforcement material

Claims (6)

  After cutting the surface of the existing concrete, a sample of the cut portion of the existing concrete is collected, and the feature amount of the crack existing on the smooth observation surface formed by cutting the sample in the depth direction of the existing concrete is measured. Then, by collating the measurement data with the evaluation data, the damage due to the cutting of the existing concrete is quantitatively evaluated, and the evaluation data is characterized by the crack of the concrete cutting portion measured in the same manner as described above. A method for evaluating damage caused by a cutting process of concrete, characterized in that the amount and the adhesion strength of the repair / reinforcement material handed over to this cutting location are accumulated in association with each other.   The method for evaluating damage caused by a concrete cutting process according to claim 1, wherein the feature quantity of the crack to be measured is one or more of the number, density, width, and length.   2. The method for evaluating damage caused by a concrete cutting process according to claim 1, wherein the sample is collected after a protective mortar is applied to a cutting surface of existing concrete and cured.   The method for evaluating damage caused by the concrete cutting process according to claim 1, wherein the observation surface is mirror-polished.   2. The method for evaluating damage caused by a concrete cutting process according to claim 1, wherein a flaw detection liquid is applied to the observation surface when the crack is measured.   The surface of the existing concrete is cut to an appropriate depth by a mechanical cutting method selected based on the evaluation result according to any one of claims 1 to 4, and then cut to a predetermined depth by a water jet method. And concrete cutting method.

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