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Appearance and internal defect detection of building concrete members
Defect detection of building concrete components is divided into appearance defect detection and internal defect detection. This paper will introduce the contents and methods of the two tests.
Concrete component defect detection
First, the appearance of defect detection
In the case of on-site inspection, it is advisable to carry out full inspection of the appearance defects of the components within the inspection scope; when the inspection conditions are not available, the area of the uninspected components shall be indicated.
The relevant parameters of the appearance defects of the concrete members can be detected according to the following conditions:
1 The length of the exposed ribs can be measured with a steel ruler or a tape measure;
2 Holes can be directly measured with steel ruler, and the hole depth can be measured with vernier calipers;
3 The position and extent of honeycomb and looseness can be measured with a steel ruler or a tape measure;
4 The position and extent of pitting, peeling and sanding can be measured with a steel ruler or a tape measure;
5 The maximum width of the surface crack can be measured by a special measuring instrument for cracks, and the length of the surface crack can be measured by a steel ruler or a tape measure.
Defects in the appearance of concrete members shall be classified and summarized according to the type of defects. The summary results may be expressed in a list or diagram and should reflect the distribution characteristics of the appearance defects within the scope of inspection.
Second, internal defect detection
For the detection of internal defects or areas, it is advisable to carry out full inspection. When the conditions for full detection are not available, the following components or parts may be selected for testing according to the agreed sampling principle:
1 important components or parts;
2 A component or part with a serious appearance defect.
The internal defects of concrete members should be tested by double-sided ultrasonic method. When there is only one side, the impact echo method and electromagnetic emission method can be used for detection. For the difficult area, the core verification or chisel verification should be carried out.
Ultrasonic testing of the internal parameters of concrete components shall be measured in accordance with the following provisions:
1 Defect test sites should be determined according to inspection requirements and on-site operating conditions;
2 The surface of the concrete to be measured should be clean and flat. If necessary, it can be smoothed with a grinding wheel or smoothed with high-strength quick-setting mortar; the smoothing mortar should be well bonded to the concrete to be tested;
3 Under the condition that the first wave amplitude measurement accuracy is satisfied, the higher frequency transducer should be selected;
4 The transducer should be tightly coupled to the concrete test surface by the coupling agent, and the coupling layer should not be mixed with sand or air;
5 When detecting, avoid the ultrasonic propagation path parallel to the internal rebar axis. When it is unavoidable, the minimum distance between the measuring line and the reinforcing bar should be no less than 1/6 of the ultrasonic ranging;
6 According to the size of the distance measurement and the appearance quality of the concrete, the parameters such as the emission voltage and the sampling frequency should be set. When the same side position is detected, the instrument parameters should remain unchanged;
7 The sound time, amplitude and frequency value should be read and recorded, and the waveform should be accessed if necessary;
8 When suspicious data appears in the test, the cause should be found in time. If necessary, retest or check the test.
The detection of internal defects in concrete members shall provide information on the selection of the lateral position, location, appearance quality description, and the nature and distribution characteristics of the defects.