Concrete permeability resistance measuring system based on high-frequency alternating current

Abstract

The invention discloses a concrete permeability resistance measuring system based on high-frequency alternating current, belonging to the field of concrete performance testing. The concrete permeability resistance measuring system is characterized in that an 89C52 type microprocessor, a TLC5615 type amplitude adjustment adjusting D / A module, an AD9832 type direct digital frequency synthesizer, an AD534 type multiplier and a CVA-1000 type power amplification module in a program-control high-frequency alternating current power supply are adopted, user expected frequency and current value input by a computer are modulated into required high-frequency alternating current, and then the high-frequency alternating current is output; then, current in a measuring loop is collected by a DAM-3502 type isolation sampling module; closed loop control is carried out after the current is judged by software containing a PID (Proportion Integration Differentiation) control module via the computer; and measurement on the concrete permeability resistance of the high-frequency alternating current expected by the user is formed. The concrete permeability resistance measuring system has the advantages of high measuring precision, large loading capability and good stability and convenience for function expansion.

Description

Technical field: [0001] It is used to test the permeability resistance of concrete samples obtained by laboratory preparation or engineering core drilling. Background technique [0002] The durability of concrete structures is a hot spot in the research of concrete materials science and concrete structure engineering. The permeability of concrete directly determines the degree of difficulty for external substances such as aqueous solutions, carbon dioxide, chloride ions and sulfates to penetrate, diffuse or migrate into the concrete structure under pressure, chemical potential or electric field, and therefore determines the durability of concrete The key parameters. [0003] Permeation refers to the movement of liquid or gas under pressure. The mathematical model describing its state of motion is Darcy's theorem; diffusion refers to the movement of particles in a gas or liquid due to the existence of a concentration difference. The mathematical model describing its state of motion...

AI Technical Summary

Problems solved by technology

The disadvantage of the RCM method is that the test takes a long time, up to 96 hours, and the color reaction of the sample section is not very clear and sharp, which affects the efficiency and accuracy of the test and limits the application and promotion of this test method.

(3) Resistivity method, which has not yet formed a unified standard

According to the model proposed by Professor Z.P.Bazant, Gong Guojun of Shanghai Jiaotong University and others established a method for testing concrete resistance. This method uses a DC power supply, records the current in the loop during the test, and then uses the voltage of the power supply and the loop current Calculate the resistance of the tested sample according to the ratio of the tested sample, and then calculate the resistivity according to the area and length of the tested sample (Gong Guojun, Song Xiaobing, Kong Qiming. Resistivity of concrete under chloride salt pollution. Industrial Construction, 2005 35(12) : 5-7.), the shortcoming of this method is to adopt the DC power supply, so the polarization and corrosion of the electrode cannot be avoided, and at the same time, this method does not provide requirements for the current value to be achieved in the test circuit or the potential difference between the two ends of the sample. Therefore, it is difficult to implement; Hao Tingyu of Beijing Yejian Special Materials Co., Ltd. has applied for an invention patent of "a concrete resistivity measurement method and its device (Patent No. 200910148445)". A constant current value is formed in the middle, and the resistivity of concrete is calculated by measuring the potential difference between the two ends of the tested sample during power-on and the potential difference between the two ends of the tested sample in a short enough time after power-off

The disadvantage of this method is also that the DC voltage used will cause polarization corrosion of the electrode. At the same time, the requirement of this method to test the potential difference between the two ends of the test sample within a short enough time after power off is difficult to quantify, so it is difficult to operate. and will affect the accuracy of test results

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