A method for targeted elimination of initial defects of large concrete precast

Abstract

The application discloses a large-scale concrete prefabricated part initial defect targeted elimination method, relates to the technical field of concrete prefabricated part initial defect treatment, is suitable for eliminating the initial defect of concrete after being vibrated and before being solidified and formed, and fundamentally improves the stress and anti-leakage performance of the concrete prefabricated part during service. On the basis of a focusing electrode system, in combination with the objective fact that conductive ions exist before the concrete is solidified, the partition detection of the large-scale concrete prefabricated part is realized, so that the initial defect can be eliminated by targeted vibration. The specific steps are as follows: array type focusing electrode systems are arranged on the inner surfaces of concrete pouring molds; the focusing electrode systems are connected with focusing detection equipment; the resistivity of each partition before solidification is obtained; an abnormal area is found, and then the abnormal area is strengthened and vibrated. The application can realize the partition detection and targeted vibration of the large-scale concrete prefabricated part, so that the initial defect of the large-scale concrete prefabricated part is eliminated.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of initial defect treatment of concrete prefabricated parts, and is suitable for eliminating initial defects after concrete is vibrated and before it is solidified and formed, thereby fundamentally improving the stress and anti-leakage performance of concrete prefabricated parts during service. BACKGROUND

[0002] Compared with cast-in-place concrete, prefabricated concrete structures have high forming quality, good stress and water sealing performance due to the standardized process flow of factory mixing, mixing, vibration and steam curing. However, existing prefabrication plants generally lack a complete online monitoring system for concrete vibration and steam curing, resulting in uncertainty about the actual vibration law of the vibration table (or vibrating rod) transmitted to the concrete. In particular, the vibration table (or vibrating rod) will inevitably be mechanically damaged during long-term use, and the vibration parameters of the vibration source will change accordingly. The vibration is attenuated in the vibration table-mold-concrete system, ultimately affecting the concrete density, bubbles, segregation and other characteristics, especially the spatial distribution of coarse aggregate in the concrete, which seriously affects the quality stability of the concrete prefabricated parts, and even causes the quality of some prefabricated parts to deviate from the normal standard, posing a safety hazard to the long-term operation stability of the concrete structure in large-scale engineering.

[0003] Developing a targeted defect elimination technology after concrete is vibrated and before it is solidified and formed is of great significance to improving the initial quality of concrete prefabricated parts and enhancing the stress and anti-leakage performance of support structures in the process of deep space development and utilization in China, and has a broad application prospect. However, although the initial defects of concrete prefabricated parts have a significant impact on the stress and anti-leakage performance of structures during the operation period of underground engineering, there is still no unified standard and mature method for eliminating the defects under targeted guidance. SUMMARY

[0004] To solve the above problems, the present application proposes a method for targeted elimination of initial defects of large concrete prefabricated parts, which is based on the research of the focusing electrode system (application numbers 202310509368.X and 202110088361.6) and combined with the objective fact that there are conductive ions inside the concrete before it is solidified, to realize the partition detection of large concrete prefabricated parts and facilitate the targeted vibration to eliminate initial defects.

[0005] The technical solution of the present application is as follows:

[0006] Step 1), according to the geometric shape of the concrete prefabricated part, a focusing electrode system is arranged on the inner surface of the concrete pouring mold;

[0007] When the concrete precast is in a cylindrical shape, the focusing electrode system comprises a plurality of main detection electrodes, a plurality of loop electrodes and an infinite electrode; the plurality of main detection electrodes are arranged on a straight line close to the inner surface of the mold, and the plurality of loop electrodes are arranged on another straight line close to the inner surface of the mold, both of which are parallel to the axis of the cylindrical concrete precast, the main detection electrodes and the loop electrodes correspond to each other and are arranged symmetrically along the axis of the concrete precast, and the infinite electrode is arranged at a position close to the corner of the surface of the concrete precast;

[0008] When the concrete precast is in a non-cylindrical symmetric shape, the focusing electrode system comprises a whole shielding electrode, a plurality of main detection electrodes, a whole loop electrode and an infinite electrode, the whole shielding electrode is arranged on an inner surface of a concrete pouring mold, the whole loop electrode is arranged on another inner surface of the concrete pouring mold opposite to the shielding electrode, and the array of main detection electrodes is arranged on the surface of the shielding electrode and is provided with an insulating ring between the shielding electrode and the main detection electrodes; the infinite electrode is arranged at a position close to the corner of the surface of the concrete precast;

[0009] When the concrete precast is in a non-symmetric shape, the focusing electrode system comprises a whole shielding electrode, a plurality of main detection electrodes, a whole loop electrode and an infinite electrode, the shielding electrode is arranged on any inner surface of a concrete pouring mold, then the loop electrode is arranged on one or two inner surfaces opposite to the shielding electrode, the loop electrodes on each surface are connected as a whole, and the projection area of the loop electrode arrangement surface on the shielding electrode plane is not less than the shielding electrode plane; a plurality of main detection electrodes arranged in an array are arranged on the surface of the shielding electrode, and an insulating ring is arranged between the main detection electrodes and the shielding electrode; the infinite electrode is arranged at a position close to the corner of the surface of the concrete precast;

[0010] Step 2), connect the focusing electrode system with the focusing detection device, and according to the current focusing principle, set the shielding electrode and the transmitting electrode to be equipotential, force the main detection current to propagate in a nearly columnar shape to the loop electrode opposite to the surface, obtain the resistivity detection results on the path opposite to the surface in front of each main detection electrode, and generate a resistivity image;

[0011] Step 3), obtain the resistivity value ρ0 of the concrete precast after pouring and before solidification under the standard vibration process condition;

[0012] Step 4) In the subsequent concrete prefabricated part vibrating forming process, once there are initial defects such as low density, bubbles, segregation in the concrete prefabricated part, the resistivity ρ at the corresponding position on the resistivity image deviates from the resistivity value ρ0 of the concrete prefabricated part after pouring and before solidification under the standard vibrating process condition, the position in the concrete prefabricated part is defined as an abnormal area, and then the abnormal area is strengthened to vibrate until the resistivity value returns to ρ0, so as to eliminate the initial defects in the concrete prefabricated part and improve the solidification forming quality.

[0013] In step 1), for the cylindrical concrete prefabricated part, the circumference is the natural truncation boundary, the electrode is prepared according to the existing mature technology, and the embedding and measurement are carried out; in step 1), for the non-cylindrical concrete prefabricated part, any one surface in the concrete pouring mold is selected, and the integral shielding electrode is arranged, the shielding electrode is a conductive film with a thickness of ≤100 μm, the outer contour of the shielding electrode is the same as the arrangement surface in the prefabricated mold, the shielding electrode is provided with circular holes with a center distance of ≥10 cm in two orthogonal directions, the diameter of the circular hole is greater than the maximum coarse aggregate diameter in the concrete and ≤5 cm, when the center distance of the last circular hole is less than 10 cm from the center distance of the previous circular hole, the last circular hole is arranged close to the prefabricated mold boundary; a Φ4.0 cm circular main detection electrode is arranged in the Φ5 cm circular hole, and the main detection electrode and the shielding electrode are insulated by a 5 mm wide circular ring; one or two surfaces in the opposite direction of the surface where the shielding electrode is arranged are arranged with integral loop electrodes, and the loop electrode is a conductive film with a thickness of ≤100 μm, and the outer contour of the loop electrode is the same as the arrangement surface.

[0014] Further, for the inner surface of the concrete prefabricated mold, insulation is implemented by brushing silicone release agent, the insulation resistance is ≥500 MΩ, the shielding electrode is arranged close to the coating, and the surface of the prefabricated part is a natural current truncation boundary.

[0015] Further, the steel reinforcement cage or steel reinforcement mesh in the concrete prefabricated mold is electrically insulated by spraying 30-50 μm thick insulating paint or three-proof paint, and the insulation resistance is ≥500 MΩ.

[0016] Further, the emission current I of the main detection electrode is fixed, and the emission voltage U of the main detection electrode is measured, and then the resistivity of the main detection electrode in the concrete prefabricated part is

[0017] The beneficial effects of the present application are: after the concrete is poured in the mold, the resistivity response is relatively sensitive due to the objective existence of free water and multiple ion components in the interior of the concrete before hardening and forming, and meanwhile, the principle of current focusing is used, a plurality of nearly columnar current beams are generated, the partition detection of the large concrete prefabricated part is realized, the targeted vibration is facilitated, and the purpose of targeted guiding to eliminate the initial defects of the large concrete prefabricated part is achieved. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the electrode arrangement when processing the cube (rectangular) preform of the present invention.

[0019] Figure 2 This is a schematic diagram of the electrode layout when processing cylindrical preforms according to the present invention. Detailed Implementation

[0020] To clearly illustrate the technical features of this patent, the following detailed description is provided through specific embodiments and in conjunction with the accompanying drawings.

[0021] The specific steps in this case are as follows:

[0022] Step 1) Based on the geometry of the precast concrete component, a focusing electrode system consisting of a main detection electrode, a shielding electrode, a loop electrode, and an infinity electrode is set up;

[0023] For non-cylindrical symmetrical shapes, such as cube precast components, the specific steps are as follows: Select one surface inside the concrete casting mold and install a shielding electrode. The shielding electrode is a conductive film with a thickness of ≤100μm. The outer contour of the shielding electrode is the same as the surface on which it is installed inside the precast mold. The shielding electrode has circular holes with a center-to-center distance of ≥10cm in two orthogonal directions. The diameter of the circular holes is larger than the diameter of the largest coarse aggregate in the concrete and ≤5cm. When the center of the last circular hole is less than 10cm from the center of the previous circular hole, the last circular hole is installed close to the boundary of the precast mold. A Φ4.0cm circular main detection electrode is arrayed in the Φ5cm circular hole. A 5mm wide circular ring is used for insulation between the main detection electrode and the shielding electrode. A loop electrode is installed on the inner surface of the precast mold on the opposite side of the surface where the shielding electrode is located. The loop electrode is a conductive film with a thickness of ≤100μm. The outer contour of the loop electrode is the same as the surface on which it is installed. An infinity electrode is installed near the corner of the surface of the concrete precast component.

[0024] Step 2) Connect the focusing electrode system to the focusing detection device. According to the principle of current focusing, set the shielding electrode and the emitting electrode to be at the same potential, so that the main detection current propagates in a near columnar shape to the opposite loop electrode, obtain the resistivity detection results on the path directly opposite each main detection electrode, and generate a resistivity image.

[0025] Step 3) Obtain the resistivity value ρ0 of the precast concrete component before curing after pouring under standard vibration process conditions.

[0026] Step 4) In the subsequent processing of precast concrete components, if there are initial defects such as low density, air bubbles, or segregation in the precast concrete components, the resistivity ρ at the corresponding position on the resistivity image will deviate from the resistivity value ρ0 of the precast concrete component after pouring and before curing under standard vibration process conditions. This position in the precast concrete component will be defined as an abnormal area. Then, the abnormal area will be vibrated more vigorously until its resistivity value returns to ρ0, thereby eliminating the initial defects in the precast concrete component and improving the curing quality.

[0027] Before laying the shielding electrode in step 1), the inner surface of the precast concrete mold is insulated by applying a silicone oil-based release agent with an insulation resistance ≥500MΩ. The shielding electrode is placed close to the coating, while the surface of the precast part is a natural current cutoff boundary.

[0028] In step 1), the steel cage or steel mesh inside the precast concrete mold and the ring between the main detection electrode and the shielding electrode are electrically insulated by spraying an insulating coating or three-proof paint with a thickness of 30-50μm, with an insulation resistance ≥500MΩ.

[0029] If the emission current I of the main detection electrode is fixed, and the emission voltage U of the main detection electrode is measured, then the resistivity of the path directly opposite the main detection electrode in the precast concrete component is...

[0030] Regarding the appendix Figure 2 The elongated cylindrical prefabricated mold shown, such as a precast pile, has different depth sections serving as detection zones under these conditions. After the inner surface of the mold is coated with an insulating layer, it naturally becomes the current focusing and cutting-off boundary. No separate shielding electrode is needed; only the main detection electrode, loop electrode, and infinity electrode are required, and these electrodes can be fabricated using existing technology. For other special-shaped prefabricated molds, the layout methods for the cuboid and cylindrical shapes described above can be used, and these methods are also within the scope of this invention.

[0031] For asymmetrical precast concrete components, the focusing electrode system also includes an integral shielding electrode, several main detection electrodes, an integral loop electrode, and an infinity electrode. The shielding electrode is arranged on any one of the inner surfaces of the concrete casting mold. Several main detection electrodes are arranged in an array on the surface of the shielding electrode. An insulating ring is provided between the main detection electrodes and the shielding electrode.

[0032] Unlike non-cylindrical symmetrical shapes, for asymmetrical precast concrete components, one or two inner surfaces facing the shielding electrode need to be equipped with loop electrodes. The loop electrodes on each surface are connected as a whole, and the projected area of ​​the loop electrode surface on the shielding electrode plane is not less than the plane where the shielding electrode is located. The infinity electrode is also arranged at the corner of the surface of the precast concrete component.

[0033] The present application has many specific embodiments and the foregoing merely preferred embodiments and, it will be apparent to those skilled in the art that numerous modifications can be made without departing from the principles of the present application and these modifications are intended to be included within the scope of the application.

Claims

1. A method for targeted elimination of initial imperfections in large concrete precast elements, characterized by, The specific steps are as follows: Step 1) Based on the geometry of the precast concrete component, a focusing electrode system is arranged on the inner surface of the concrete casting mold; When the precast concrete component is cylindrical, the focusing electrode system includes several main detection electrodes, several loop electrodes, and an infinity electrode. The main detection electrodes are arranged on a straight line close to the inner surface of the mold, and the loop electrodes are arranged on another straight line close to the inner surface of the mold. Both straight lines are parallel to the axis of the cylindrical precast concrete component. The main detection electrodes and loop electrodes correspond one-to-one and are arranged symmetrically along the axis of the precast concrete component. The infinity electrode is located at a corner of the surface of the precast concrete component. When the precast concrete component is non-cylindrical symmetrical, the focusing electrode system includes an integral shielding electrode, several main detection electrodes, an integral loop electrode, and an infinity electrode. The integral shielding electrode is arranged on one inner surface of the concrete casting mold, and the integral loop electrode is arranged on another inner surface of the concrete casting mold, directly opposite the shielding electrode. The main detection electrode array is arranged on the surface of the shielding electrode, and an insulating ring is provided between it and the shielding electrode. The infinity electrode is arranged at a corner of the surface of the precast concrete component. When the precast concrete component is asymmetrical, the focusing electrode system includes an integral shielding electrode, several main detection electrodes, an integral loop electrode, and an infinity electrode. The shielding electrode is arranged on any one of the inner surfaces of the concrete casting mold. Then, one or two inner surfaces facing the shielding electrode are selected to arrange the loop electrodes. The loop electrodes on each surface are connected as a whole, and the projected area of ​​the loop electrode arrangement surface on the shielding electrode plane is not less than the plane where the shielding electrode is located. Several main detection electrodes are arranged in an array on the surface of the shielding electrode, and an insulating ring is provided between the main detection electrodes and the shielding electrode. The infinity electrode is arranged at a corner position on the surface of the precast concrete component. Step 2) Connect the focusing electrode system to the focusing detection device. According to the principle of current focusing, when the precast concrete component is not cylindrical, set the shielding electrode and the main detection electrode to be at the same potential, so that the main detection current can be forced to propagate in a near-cylindrical shape to the opposite loop electrode, obtain the resistivity detection results on the path directly in front of each main detection electrode, and generate a resistivity image. Step 3) Obtain the resistivity value ρ0 of the precast concrete component after pouring and before curing under standard vibration process conditions. Step 4) During the subsequent vibration molding process of precast concrete components, if initial defects such as low density, air bubbles, or segregation exist in the precast concrete components, the resistivity ρ at the corresponding position on the resistivity image will deviate from the resistivity value ρ0 of the precast concrete component after pouring and before curing under standard vibration process conditions. This position in the precast concrete component will be defined as an abnormal area. Then, the abnormal area will be vibrated more vigorously until its resistivity value returns to ρ0, thereby eliminating the initial defects in the precast concrete components and improving the curing quality.

2. The method for targeted elimination of initial defects in large precast concrete components according to claim 1, characterized in that, In step 1), for cylindrical precast concrete components, the circumference is the natural truncated boundary. Electrodes are prepared, embedded, and measured. For non-cylindrical precast concrete components, in step 1), an integral shielding electrode is placed on any surface within the concrete casting mold. The shielding electrode is a conductive film with a thickness ≤100μm. The outer contour of the shielding electrode is the same as the surface within the precast mold. The shielding electrode has circular holes with a center-to-center distance ≥10cm in two orthogonal directions. The diameter of the circular holes is larger than the diameter of the largest coarse aggregate in the concrete and ≤5. When the distance between the center of the last circular hole and the center of the previous circular hole is less than 10cm, the last circular hole is arranged close to the boundary of the precast mold; when the circular hole is Φ5cm, a Φ4.0cm circular main detection electrode is arranged in the Φ5cm circular hole, and a 5mm wide circular ring is set between the main detection electrode and the shielding electrode for insulation treatment; an integral loop electrode is arranged on one or two surfaces in the direction directly opposite to the surface where the shielding electrode is located. The loop electrode is a conductive film with a thickness ≤100μm, and the outer contour of the loop electrode is the same as that of its arrangement surface.

3. The method for targeted elimination of initial defects in large precast concrete components according to claim 1, characterized in that, For the inner surface of the precast concrete mold, insulation is achieved by applying a silicone oil-based release agent with an insulation resistance ≥500MΩ. The shielding electrode is placed close to the coating, while the surface of the precast component is a natural current cutoff boundary.

4. The method for targeted elimination of initial defects in large precast concrete components according to claim 1, characterized in that, Electrical insulation is achieved by spraying a 30-50μm thick insulating coating or conformal coating inside the precast concrete mold for the steel reinforcement cage or mesh, with an insulation resistance ≥500MΩ.

5. The method for targeted elimination of initial defects in large precast concrete components according to claim 1, characterized in that, If the emission current I of the main detection electrode is fixed, and the emission voltage U of the main detection electrode is measured, then the resistivity of the path directly opposite the main detection electrode in the precast concrete component is...

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