How To Measure Subfloor Thickness
Floor thickness is a significant factor in the safety of engineering structures. Determining floor thickness is one of the critical items in engineering quality. So, how to measure the floor thickness?
How to measure floor thickness
1) Steel tape detection: open a hole in the floor or use the reserved hole on the floor for detection. This method is commonly used for random sampling inspection of the supervision unit on-site due to damage to the floor.
2) Level gauge detection: use the level gauge to measure the elevation of the floor surface of a certain point on the floor and the elevation of the floor bottom corresponding to that point.
3) Electromagnetic detection: In the detection of construction engineering, the thickness of closed structures such as floors and some walls.
There are mainly two types of instruments used for nondestructive testing of structural thickness such as floor and wall:
one is an echometer based on the elastic wave reflection principle, and the other is a ground-penetrating radar instrument based on the electromagnetic wave reflection principle. When using an echometer, we need on-site calibration. Since the concrete structure is made of heterogeneous materials, the calibration accuracy directly affects the accuracy of the test results, and the actual error is about ± 10% of the thickness.
While the latter is not a special thickness meter, mainly used for engineering surveys or quality inspection, due to the influence of reinforcement in concrete, the accuracy is about ± 5%, but the high price.
Nondestructive testing with an error of about ± 2mm is a simple, convenient, and accurate testing floor thickness method. It is suitable for inspection organizations.
The detection of floor thickness gauge
Assuming that a floor is surrounded by axes x1, Y1, X2, and Y2, it is divided into four side areas, A, B, C, and D, and a central area, E. Each side is about 1m long and 3m wide, and the inner edge distance or beam edge is about 0.3m.
If the difference between the values of floor thickness of three points in each detection area exceeds + 8 or -5, we can appropriately increase the number of detection points. The total number of detection points in each area should not be more than 3, and the distance between each two detection points should not be less than 3m. The average of the inspection values of all inspection points in each inspection area is taken as the representative value of the floor thickness in the inspection area.
The floor thickness gauge is an instrument for nondestructive testing based on the electromagnetic principle. The transmitting probe and receiving probe are placed on the surface and bottom of the floor to be tested.
The transmitting probe sends out the electromagnetic signal, and the receiving probe receives the attenuated magnetic field signal. After the number value of the testing point is stable, we can record it by floor thickness gauge.
Step:
Keep the probe close to the top surface of the floor;
and slowly move the probe from left to right to gradually reduce the thickness value on the screen until the position of the minimum value is found;
The position is just above the transmitting probe;
The displayed thickness value is the floor thickness of the measuring point.
When the display is correct and stable, press the OK key to store it, and the thickness measurement of this point is completed.
FAQ：
Does the reinforcement in the floor affect the test results?
In general, there is no affecting factor since reinforcement spacing in the floor is commonly greater than 100mm. But if the area where the reinforcement is too dense, it will affect the test results.
Therefore, we should try to select the area with large reinforcement spacing for the test. You may know that when testing some columns with floor thickness gauge, the test error is large because of too dense reinforcement in concrete. When testing the wall, the error is significant, which may be wired in the wall that produces a magnetic field, resulting in inaccurate test results.
What is the direction key of the floor thickness gauge used for?
It is to prompt the moving direction of the receiving probe. The left key indicates that the probe is moving closer to the transmitting probe, and the right key indicates that the receiving probe is moving farther away from the transmitting probe.
Why is the floor thickness gauge not displayed or much larger?
This issue may occur when the power of the transmitting probe is insufficient. When the power of the transmitting probe is too little, the measured value is too large. If there is no problem with the power of the transmitting probe, it may be caused by the failure of connecting wire between the host and the receiving probe.
