Concrete test hammer overview

Concrete test hammer is a detection device, suitable for testing the strength of general building components, bridges and various concrete components (slabs, beams, columns, bridges). The main technical indicators have impact function; the spring strength of the spring Hammer stroke; pointer system maximum static friction force and rigid drilling rate set average.
Impact function 2.207J (0.225kgf.m) impact spring tension 785N / cm impact hammer stroke 75mm just drill rate 80 ± 2

Concrete test hammer Standars as below:

US ASTM C805 standards

BS 1881-202 standards

EN 12504-2 standards

IS: 13311(2)-1992 standards

Features of concrete rebound meter:
The Concrete Test hammer implements US ASTM C805 standards BS 1881-202 standards EN 12504-2 standards IS: 13311(2)-1992 standards national metrological verification regulations. It is suitable for detecting the strength of general building components, bridges and various concrete components (slabs, beams, columns, bridges).

Technical index
1. Impact function: 2.207J (0.225kgf.m)
2. Steel spring strength: 785N / cm
3. Stroke of impact hammer: 75mm
4. Maximum static friction of pointer system: 0.5-0.8N
5. The average value of rigid drilling rate: 80 ± 2

Method of operation
In the whole process of operating the Concrete test hammer rebound instrument, you should pay attention to the posture of holding the rebound instrument, and hold the middle part of the rebound instrument with one hand to play a role of uprightness; Auxiliary righting effect. The operation method of the rebound tester is to ensure that the axis of the rebound tester is always perpendicular to the concrete test surface, the force is even and slow, and the alignment is aligned with the test surface. Advance slowly and read fast.

Test Methods 
1. Two methods can be used to test the strength of concrete components
(1) Single detection:
Suitable for the detection of a single structure or component;
(2) Batch testing It is applicable to structures or components with the same production process conditions, the same concrete strength level, the same raw materials, molding process and maintenance conditions and similar age. During batch testing, the number of random inspections shall not be less than 30% of the total number of components in the same batch and not less than 10. When sampling components, follow the random selection of key parts or representative components.
2. The measurement area of ​​the component meets the following requirements
(1) The number of measurement areas for each structure or component should not be less than 10. For components with a dimension less than 4.5m in one direction and less than 0.3m in the other direction, the number of measurement areas can be appropriately reduced, but should not be less than 5;
(2) The distance between two adjacent measurement areas shall not exceed 2m at the maximum, and the distance between the measurement area and the end of the member or the edge of the construction joint shall not be greater than 0.5m and not less than 0.2m;
(3) The test area should be selected as far as possible on the side where the rebound tester is in the horizontal direction to detect the concrete. When this requirement cannot be met, the rebound meter can be placed in a non-horizontal direction to detect the pouring side, surface or bottom of the concrete;
(4) The measurement area should be selected on the two symmetrical measurable surfaces of the component or one measurable surface, and should be evenly distributed. In the important parts or weak parts of structural members, the measurement area must be arranged, and the embedded parts should be avoided;
(5) The measurement area should not be larger than 0.04m2;
(6) The detection surface should be a concrete surface, and it should be clean, flat, free of loose layers, floating slurries, greasy dirt, honeycomb, and pitted surfaces. If necessary, use a grinding wheel to remove loose layers and debris, and no residual powder Or debris;
(7) The thin-walled or small components that vibrate when struck should be fixed.

Measurement of rebound value of concrete test hammer
1. When testing, the axis of the rebound hammer should always be perpendicular to the detection surface of the structure or component, apply pressure slowly, with accuracy and quick reset.
2. The measuring points should be evenly distributed in the measuring area. 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 the stomata or exposed stones, and can only be played once at the same point. Each measurement area records 16 rebound values, and the rebound value of each measurement point is accurate to 1.
Measurement of carbonation depth of concrete rebound meter
1. After the rebound value measurement is completed, measure the carbonation depth of the concrete at a representative location. The number of measurement points should not be less than 30% of the number of measurement areas of the component. . When the carbonation depth range is greater than 2, the carbonation depth value should be measured in each measurement area.
2. For the measurement of carbonation depth, a suitable tool can be used to form a hole with a diameter of 15 mm on the surface of the measurement area, and the depth should be greater than the carbonization depth of the concrete. The powder and debris in the holes should be removed and cannot be washed with water. Use 1% ~ 2% phenolphthalein alcohol solution to drip on the edge of the inner wall of the hole, the color of the carbonized concrete does not change, the uncarbonized concrete becomes red, when the boundary between carbonized and uncarbonized is clear, use the depth measurement tool to measure the carbonized The depth of the concrete shall not be less than 3 measurements, and the average value shall be taken to the nearest 0.5mm.
Calculation of rebound value of concrete rebound meter
1. Calculate the average rebound value in the measurement area. The 3 maximum values ​​and 3 minimum values ​​should be removed from the 16 rebound values ​​in the measurement area. The remaining 10 rebound values ​​are calculated as follows: 10 where Rm-measurement Area average rebound value, accurate to 0.1; Ri — rebound value of the i-th measurement point.
2. In the non-horizontal direction, press the following correction: Rm R i 1 10 i Rm Rm Ra where Rm-the average rebound value of the measurement area during non-horizontal detection, accurate to 0.1; Ra-rebound during non-horizontal detection For correction value, check according to the attached table.
3. When detecting the top or bottom surface of the concrete pouring in the horizontal direction, use the following correction: tt Rm Rm Ra bb Rm Rm Ra tb where Rm, Rm — the average value of the rebound value of the measurement area when detecting the concrete pouring surface and bottom surface in the horizontal direction; b Rat, Ra — the correction value of the rebound value of the concrete pouring surface and bottom surface, inquire according to the attached table.
4. When the rebound instrument is neither horizontal nor concrete on the side of the pouring, the angle should be corrected first, and then the pouring surface should be corrected.

Concrete test hammer Calibration method
4.1 Temperature.
4.1.1 Carry out at room temperature 20 ± 5 ℃.
4.1.2 The weight and hardness of the calibration must meet the requirements of the national standard “Rebound 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 rigid concrete body.
4.2.2 When the rebound hammer hits downward, the lever should be rotated four times, each time by 90 °.
4.2.3 Bounce three times in each direction, and take the average rebound value of the last three readings to average

Principle of Concrete test hammer
The concrete rebound meter uses a spring to drive the hammer and the restoring force of the instantaneous elastic deformation produced by the hammer hitting the concrete surface, so that the hammer drives the pointer to rebound and indicates the distance of the rebound. The springback value (the ratio of the springback distance to the distance between the hammer and the ram before the impact, calculated as a percentage) is used as one of the indicators of concrete compressive strength to estimate the compressive strength of concrete.

Concrete test hammer feature
Lightweight (2/3 less labor than similar products), flexible, inexpensive, no power supply, easy to master, the button is not easy to fall off by the stretching process, and the pointer is easy to adjust the friction. It is the first choice for nondestructive testing suitable for field use.

maintenance
The rebound hammer should be routinely maintained when one of the following conditions exists:
1. Bouncing more than 2000 times;
2. When there is doubt about the detected value;
3. The set value of steel anvil rate is unqualified; concrete rebound tester
The conventional maintenance method of the concrete rebound meter should meet the following requirements:
1. Remove the movement after decoupling the flick hammer, and then remove the flick lever (take out the buffer pressure spring inside) and the triple piece (flash hammer, flick tension spring and tension spring seat);
2. Use gasoline to clean the components of the movement, especially the center guide rod, the hammer and the inner hole and impact surface of the hammer. After cleaning, apply a thin layer of watch oil or sewing machine oil to the center guide bar, and no other parts should be coated with oil;
3. Clean the inner wall of the casing, remove the scale, and check that the friction of the pointer should be between 0.5-0.8N;
4. Do not rotate the zero-adjusting screws that have been positioned and fastened on the tail cover;
5. Do not make or replace parts;
6. After maintenance, the rate test should be carried out as required, and the rate value should be 80 ± 2.
Verification of concrete rebound tester
The rebound hammer should be sent to the statutory department for verification when one of the following conditions exists, and the rebound hammer that passed the verification should have a verification certificate:
1. Before the new rebound hammer is activated;
2. Exceed the valid period of verification (validity period is half a year);
3. The cumulative number of bombings exceeds 6000;
4. The steel anvil rate is not qualified after routine maintenance;
5. Suffered from severe impact or other damage.

 

Operating procedure

1. Hold the flick rod against the surface of the concrete, lightly press the instrument to loosen the button, when the pressure is released, the flick rod is extended, and the hook is hooked with the flick hammer.
2. Make the axis of the instrument always perpendicular to the surface of the concrete and apply pressure slowly and evenly. After the hammer is unhooked and the impact rod is hit, the rebound of the hammer will move the pointer back to a certain position. The value tick marks indicate that a certain value on the scale is the rebound value.
3. Make the instrument movement continue to bear against the concrete surface to take readings and record the rebound value. If the conditions are not conducive to reading, you can press the button to lock the movement and move the instrument to another place to read.
4. Gradually depressurize the instrument so that the flick rod extends out of the instrument for next use.

HOW TO IMPACT HAMMER FOR TESTING CONCRETE?