JP2535177B2 - Deterioration determination method for reinforced concrete structure - Google Patents

Description

TECHNICAL FIELD The present invention relates to a deterioration determination method for a reinforced concrete structure.

(Prior art) Reinforced concrete structures undergo a potential process of permeation and diffusion of corrosion factors such as chloride and oxygen, and rusting of the reinforcing bar, which leads to deterioration of the concrete and corrosion of the reinforcing bar, resulting in a covered part on the concrete surface. Defects such as cracking and peeling.

Generally, maintenance and repair of reinforced concrete structures have been taken only at such a stage, but repair and reinforcement at this point requires a considerable cost.

Therefore, it is important to detect and predict signs of deterioration as early as possible and to take appropriate measures such as suppressing the infiltration of corrosion factors.

Therefore, conventionally, as a method of early detection and prediction of signs of deterioration of reinforced concrete structures, generally a method of regularly visual inspection of the appearance, partial destruction of the structure to analyze the concrete salt content and neutralization There is a method of investigating and the self potential method.

The visual inspection method is to visually inspect the concrete surface of the structure to draw out features such as cracks, exfoliation of cover concrete, and elution of rust juice.

In addition, salinity analysis and neutralization investigation methods are possible for corrosiveness and rusting of reinforcing bars depending on the chloride content and neutralization depth of samples taken at appropriate intervals by core boring from the concrete surface to the reinforcing bar position. It is to estimate the sex.

Furthermore, the self-potential method estimates the degree of corrosion of the reinforcing bar by the value of the potential of the reinforcing bar in the concrete, which was estimated using the reference electrode.

(Problems to be solved by the invention) However, the method of visually inspecting the appearance in the above method is easily judged to be sound if cracks, peeling, rust, etc. cannot be visually confirmed on the concrete surface. It is difficult to make a qualitative judgment and a quantitative judgment because it has a certain nature and tends to be subjective.

In addition, in the salinity analysis and neutralization survey methods, since the structure is partially surveyed, deterioration of the entire structure cannot be grasped, and it takes time for survey analysis and the cost of core boring and analysis is expensive. was there.

Furthermore, since the self-potential method estimates the degree of corrosion of internal rebar using the standard value for determining the degree of corrosion of rebar, it did not match the actual degree of corrosion and was difficult to quantitatively grasp.

The present invention has been made in view of the problems as described above, and an object thereof is reinforced concrete that can early and accurately find and predict signs of deterioration of reinforced concrete structures due to deterioration of concrete and corrosion of reinforcing bars. A method of inspecting deterioration of a structure is provided.

(Means for Solving Problems) Means of the present invention for solving the above problems is to measure the natural potential of reinforcing bars in a desired range of a concrete structure by the natural potential method and to calculate the average natural potential of the natural potentials. Along with drawing a self-potential distribution map based on the electric potential, measure the specific resistance of the concrete in the desired range by the electrical resistance method and draw a specific resistance distribution map based on the specific resistance, and compare these with the self-potential distribution map. It is a deterioration determination method for a reinforced concrete structure that determines a corrosion area of a reinforcing bar by superimposing it on a resistance distribution map.

(Operation) Therefore, according to the above configuration, the corrosion range of the rebar (−25
(0 mV or less) and the electric potential distribution map, and the resistivity distribution map showing the deterioration range (35000 Ω · cm or less) of concrete drawn based on the resistivity measured by the electric resistance method are superposed. Corrosion that causes the strength of the reinforcing bars to decrease in the range where they match each other (-250 mV or less, 35000 Ω · cm
The following) is considered to be the range.

(Embodiment) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view showing the measurement of the average spontaneous potential of the present invention. As the potentiometer 1, an input resistance of 11Ω or more and a sensitivity of 10 mV or less is used, and one terminal is provided with a conductor wire 2 such as a lead wire. It is connected to the reinforcing bar m in the reinforced concrete structure M and the other terminal is connected to the reference electrode 3.

In addition, if all the reinforcing bars to be connected to the reinforcing bar m are electrically continuous with each other, at one place, otherwise, with alligator clips or welding at one continuous group. Connecting.

The reference electrode 3 is a saturated silver chloride electrode, a saturated copper sulfate electrode, or a saturated calomel electrode having a relatively stable potential that does not depend on the environment, and a water absorbing material 4 containing an aqueous solution at its tip, such as sponge, filter paper, waste cloth, etc. Is fitted.

This is because the solution penetrates into the concrete when the matching electrode 3 is brought into contact with the measurement point on the concrete surface,
On the contrary, this is to prevent the salt in the concrete from contaminating the reference electrode, and its aqueous solution is tap water or river water.

 Next, a method of measuring the average spontaneous potential will be described.

First of all, as shown in FIG. 2, the concrete surface n
Set grid-like measurement points P at intervals of 5 to 10 cm at measurement points at arbitrary points.

This measurement interval should be set small when the potential difference between adjacent measurement points is 20 mV or more.

Further, the electric potential of the reinforcing bar n in the concrete may greatly vary depending on the water content of the concrete, so that the measurement point P part is wet with water or the like in advance.

Then, the reference electrode 3 is brought into contact with each measurement point P for about 5 minutes, and the average spontaneous potential (value obtained by averaging the measured potentials in a certain representative range) of all the measurement points P is measured. A potential distribution map a for the target member as shown in FIG. 3 is created.

In this average spontaneous potential measurement, the vicinity of −250 mV is the boundary of the corrosion of the rebar, so −25 in this potential distribution map a
The range a _{1 of} 0 mV or less can be defined as the range where the reinforcing bars are corroded.

 Next, a method of measuring the specific resistance will be described.

The electrical resistance of concrete is related to the ease with which a corrosion current flows, and when the water content or salt content increases, the value decreases and corrosion is promoted.

Therefore, for the resistivity measurement, as shown in FIG. 4, four electrodes (iron nails) 5 were inserted into the surface layer of the concrete surface n on which the spontaneous potential was measured, and an alternating current of 10 mA, 3 HZ was applied to both electrodes. By doing so, the voltages for the two inner electrodes are measured, and the specific resistance ρ is obtained by the formula ρ = 2πaV / I (a: electrode interval, I: current).

Then, based on the specific resistance ρ, a resistance distribution map b for the target member is created as shown in FIG.

In this specific resistance measurement, since the boundary of rusting of the reinforcing bar is around 35000 Ωcm, 35,000 in the specific resistance distribution described above.
The range b of Ω · cm or less can be defined as the range where the reinforcing bars are completely corroded.

Therefore, the partial distribution shown in FIG. 6 in which the range a ₁ of −250 mV in the distribution map of average spontaneous potential shown in FIG. 3 and the range b ₁ of 35000 Ω · cm or less in the distribution map of resistivity shown in FIG. It can be determined that FIG. C shows the range C _{1 of} corrosion (average spontaneous potential −250 mV or less, specific resistance 35000 Ω · cm or less) that causes a decrease in proof stress of the reinforcing bar.

As a result of the experiment, the above-mentioned overlapping range C ₁
Actually, significant corrosion was observed in the steel, but no significant corrosion was observed in other parts.

(Effects of the Invention) The present invention has the following effects by adopting the method as described above.

As compared with the conventional method, the corrosion of the reinforcing bar can be determined more accurately and regularly.

Since it is not necessary to perform core boring, sampling: analysis, etc. associated with the measurement of salinity distribution and neutralization depth, it is possible to work quickly and at low cost.

Since the entire structure can be investigated in detail, the deterioration diagnosis can be made more accurate than the conventional method.

By using the above-mentioned method together, it becomes possible to detect deterioration at an early stage, and it is possible to plan a maintenance / repair measure in advance.

[Brief description of drawings]

Fig. 1 is a sectional view showing the average spontaneous potential measuring method, Fig. 2 is a plan view showing measuring points, Fig. 3 is a potential distribution diagram, Fig. 4 is a schematic diagram of the resistivity measuring method, and Fig. 5 is a ratio diagram. Resistance distribution diagram, Fig. 6
It is a distribution map of the corrosion range which moves the yield strength decrease of the reinforcing bar. 1: Potentiometer, M: Reinforced concrete structure, m: Reinforcing bar, 3: Reference electrode, 4 ... Water absorbing material, P ... Measuring point, 5 ... Reinforcing bar.

Claims (1)

(57) [Claims] 1. A self-potential method is used to measure the self-potential of a reinforcing bar in a desired range of a concrete structure, and a self-potential distribution map is drawn based on the average self-potential of the self-potential. Of the reinforced concrete structure for determining the corrosion area of the reinforcing bar by measuring the specific resistance of the concrete and drawing a specific resistance distribution map based on the specific resistance, and superimposing these natural potential distribution maps and specific resistance distribution maps Deterioration determination method.