Concrete Test Hammer

It is used to determine in-situ compressive strength of concrete. Aluminium body, supplied with aliminum carrying case.

Concrete Hammer is a testing device, suitable for testing the strength of general building components, bridges and various concrete components (plates, beams, columns, bridges), the main technical indicators are impact function; Hammer stroke; the maximum static friction of the pointer system and the average value of the drill rate.

Technical indicators:

1. Impact function: 2.207J (0.225kgf.m)

2. Rigidity of spring tension spring: 785N/cm

3. Hammer stroke: 75mm

4. The maximum static friction force of the pointer system: 0.5-0.8N

5. Average value of just drilling rate: 80±2

How to operate

During the whole process of operating the Hammer, you should pay attention to the posture of holding the Hammer, hold the middle part of the Hammer with one hand, and play the role of righting; Auxiliary righting effect. The key to the operation of the hammer is to ensure that the axis of the hammer is always perpendicular to the concrete test surface, the force is uniform and slow, and the centering is aligned with the test surface. Advance slowly, read fast.

Testing method

There are two ways to test the concrete strength of a member:

(1) Single detection:

Applicable to the detection of a single structure or component;

(2) Batch testing is applicable to structures or components of similar age, with the same concrete strength grade, basically the same raw materials, molding process, and curing conditions under the same production process conditions. In batch testing, the number of random inspections shall not be less than 30% of the total number of components in the same batch and shall not be less than 10. When sampling components, random selection of key parts or representative components should be followed.

The survey area of the second component meets the following requirements：

(1) The number of survey areas for each structure or component shall not be less than 10. For components whose dimension is less than 4.5m in one direction and less than 0.3m in the other direction, the number of survey areas may be appropriately reduced, but shall not be less than 5;

(2) The distance between two adjacent survey areas should not exceed 2m at most, and the distance between the survey area and the end of the member or the edge of the construction joint should not be greater than 0.5m and not less than 0.2m;

(3) The measuring area should be selected as far as possible on the side where the hammer is in the horizontal direction to detect the concrete. When this requirement cannot be met, the hammer can be placed in a non-horizontal direction to detect the pouring side, surface or bottom of the concrete;

(4) The measuring area should be selected on two symmetrical measurable surfaces of the component, or on one measurable surface, and should be evenly distributed. In the important parts or weak parts of the structural members, the survey area must be arranged, and the embedded parts should be avoided;

(5) The area of the survey area should not be larger than 0.04m2;

(6) The testing surface should be the concrete surface, and should be clean and smooth, and there should be no loose layer, laitance, grease, honeycomb, and pockmarked surface. If necessary, the loose layer and sundries can be removed with a grinding wheel, and there should be no residual powder. or debris;

(7) The thin-walled or small components that vibrate when shot should be fixed.

Measurement of rebound value of concrete hammer

1. When testing, the axis of the hammer should always be perpendicular to the testing surface of the structure or component, apply pressure slowly, and reset quickly with accuracy.

2. The measuring points should be evenly distributed in the measuring area, and the net distance between two adjacent points should not be less than 2cm; the distance between the measuring points and the exposed steel bars and embedded parts should not be less than 3cm. The measuring points should not be distributed on air holes or exposed stones, and the same point can only be bounced once. Each measuring area records 16 rebound values, and the rebound value of each measuring point is accurate to 1.

Measurement of carbonation depth with concrete hammer

1. After the rebound value is measured, measure the carbonation depth value of concrete at a representative position. The number of measurement points should not be less than 30% of the number of measurement areas of the component, and the average value is taken as the carbonation depth value of each measurement area of the component. . When the carbonization depth range is greater than 2, the carbonization depth value shall be measured in each measurement area.

2. For the measurement of carbonation depth, appropriate tools can be used to form holes with a diameter of 15mm on the surface of the measurement area, and the depth should be greater than the carbonation depth of concrete. Powder and debris should be removed from the holes and should not be washed with water. Use 1%~2% phenolphthalein alcohol solution to drop on the edge of the inner wall of the hole, the color of the carbonized concrete does not change, and the uncarbonized concrete turns red. When the boundary between carbonized and uncarbonized is clear, use a depth measuring tool to measure the carbonized The depth of concrete shall not be measured less than 3 times, and the average value shall be taken, accurate to 0.5mm.

Calculation of rebound value of concrete hammer

1. To calculate the average rebound value of the measurement area, 3 maximum values and 3 minimum values should be removed from the 16 rebound values of the measurement area, and the remaining 10 rebound values should be calculated as follows: The average rebound value of the area, accurate to 0.1; Ri — the rebound value of the i-th measuring point.

2. Correction in non-horizontal direction is as follows: Rm R i 1 10 i Rm Rm Ra where Rm is the average rebound value of the measurement area in non-horizontal detection, accurate to 0.1; Ra is the rebound in non-horizontal detection Correction value, query according to the attached table.

3. When the top or bottom surface of concrete pouring is detected in the horizontal direction, the correction shall be made as follows: tt Rm Rm Ra bb Rm Rm Ra tb where Rm, Rm - the average rebound value of the measuring area when the surface and bottom surface of concrete pouring are detected in the horizontal direction; b Rat, Ra - the correction value of the springback value of the concrete pouring surface and bottom surface, query according to the attached table.

4. When the test hammer is neither in a horizontal state nor on the pouring side of concrete, the angle should be corrected first, and then the pouring surface should be corrected.

Check method

4.1 Temperature.

4.1.1 Carry out at room temperature of 20±5℃.

4.1.2 The weight and hardness of the calibration must meet the requirements of the national standard "hammer tester" GB/T 9138-2015. Rockwell hardness H RC is 60±2.

4.2 Operation.

4.2.1 The steel drill should be placed firmly on the concrete solid with high rigidity.

4.2.2 When the hammer strikes downward, the striker shall rotate four times, 90° each time.

4.2.3 Bounce three times in each direction, and take the average rebound value of the last three stable readings.

Maintainance:

Routine maintenance should be performed when the hammer has one of the following conditions:

1. More than 2000 shots;

2. When there is doubt about the detection value;

3. The fixed value of steel anvil rate is unqualified; Concrete Hammer Tester

The regular maintenance method of the concrete hammer should meet the following requirements:

1. After decoupling the percussion hammer, take out the movement, and then remove the percussion rod (remove the buffer compression spring inside) and triple parts (percussion hammer, percussion tension spring and tension spring seat);

2. Use gasoline to clean all parts of the movement, especially the center guide rod, the inner hole and impact surface of the percussion hammer and percussion rod. After cleaning, apply a thin layer of watch oil or sewing machine oil on the center guide rod, and other parts should not be oiled;

3. Clean the inner wall of the casing, remove the scale, and check that the friction force of the pointer should be between 0.5-0.8N;

4. Do not rotate the zero-adjusting screw that has been positioned and fastened on the tail cover;

5. Do not make or replace parts;

6. After maintenance, the calibration test should be carried out as required, and the calibration value should be 80±2.

Verification of concrete hammer

When the hammer has one of the following conditions, it should be sent to the statutory department for verification, and the hammer that has passed the verification should have a verification certificate:

1. Before the new hammer is activated;

2. Exceed the validity period of the verification (valid for half a year);

3. The cumulative number of bombardments exceeds 6,000;

4. After routine maintenance, the fixed value of the steel anvil rate is unqualified;

5. Suffering severe impact or other damage.