ASTM C231 Standard Test Method for Air Content of Freshly Mixed Concrete by the Pressure Method

Product introduction of CA-3 gas content measuring instrument:
1. CA-3 concrete gas content measuring instrument is used to measure the gas content of concrete mixture, suitable for aggregate particle diameter not more than 40mm, gas content not more than 10%, and slump concrete. This machine has the advantages of easy operation, accurate measurement, intuitive reading and so on. It is an advanced concrete mixture gas content measuring instrument. The measuring method of the concrete gas content measuring instrument conforms to the relevant regulations of GBJ80-85 (General Concrete Mixture Performance Test Method) on the concrete mixture gas content test.

2. Parameters
1. Volume of measuring bowl: 7 liters (the inner diameter is equal to the depth)
2. Gas content range: ≤10%
3. Maximum particle size of coarse aggregate: ≤40mm
4. Quality: 13KG

3. Determination of gas content of concrete mixture
1. Wipe the inner surfaces of the measuring bowl and the lid with a damp cloth, and place the measuring bowl horizontally.

2. Put the fresh concrete mixture into the measuring bowl evenly so that the concrete mixture is a little higher than the measuring bowl. When loading, you can use a tamping rod to insert it slightly. After loading, when vibrating with a vibrating table (frequency of 50HZ, amplitude 0.5 ± 0.1mm under no load), the concrete will fall below the level during vibration. At the mouth, the concrete mixture should be added at any time, vibrate until the concrete surface is flat, and stop vibrating when it is glazed. Instead of vibrating table, use real-time tamping for tamping. Load concrete mixture into three layers. After tamping, each layer is about one-third of the height of the measuring bowl. When inserting the tamping layer, the tamping rod should penetrate the entire depth. Insert and insert it into the lower layer 10-20mm. After each layer is tamped, the tamping rod can be placed on the lower part of the measuring bowl, and the measuring bowl is alternately struck on the ground 15 times.
3. After the tamping is completed, the excess concrete mixture on the surface should be scraped off immediately with scraping ruler. If there are depressions on the surface, they should be filled in, and then smoothed with a trowel to make the surface smooth without bubbles.
4. Wipe the edge of the measuring bowl and the lid, place the O-shaped rubber seal ring (238 × 8.6) in the groove on the edge of the lid, cover the lid, clamp with a clip to make it airtight, and use a spirit level Check the level.
5. Open the faucet and the air outlet valve, use a water injector to fill the measuring bowl from the small faucet until the water flows out of the air valve port, and then close the small faucet and the air outlet valve.
6. Close all the valves and pressurize with a pump to make the gauge pressure slightly greater than 0.1MPA. Note: (1) When reading the pressure, flick the dial with your fingertip and wait for the pointer to stop swinging before reading. (2) 0.1MPA pressure line is the initial pressure line of the instrument, and 0.1MPA is the initial pressure of the instrument.
7. Press the valve stem 2-3 times, tap the circumference of the measuring bowl with a wooden beater to make the pressure evenly distributed around the sample, press the valve stem again, and after the pressure gauge pointer stabilizes, measure the pressure gauge degree, According to the relationship between the gas content calibrated by the instrument and the reading of the pressure gauge, the gas content A value of the sample of the measured concrete mixture is obtained by the instrument.

Concrete gas content measuring instrument Concrete direct reading gas content measuring instrument Imitation daily gas content measuring instrument:
After testing:
1. Open the gas outlet valve to prevent gas from the measuring bowl. If it is necessary to repeatedly measure the gas content of the same sample, repeat steps 5-7 above.
2. Open the small faucet, release the clip, and remove the lid.
3. Pour out the sample of the concrete mixture in the measuring bowl, and clean the inner surface of the bowl cover and the measuring bowl.
4. If the gas content measuring instrument is used continuously. Need to open the fine adjustment valve to deflate, so that the pressure of the gas chamber is consistent with the atmosphere.
Concrete gas content measuring instrument Concrete direct reading gas content measuring instrument
Note: During the operation, if the pressure of the air chamber is exhausted through the trim valve, and there is still pressure in the measuring bowl, the valve rod must not be pressed down, otherwise water will be sucked into the air chamber, which will cause errors in future tests.

4. Determination of concrete mixture
1. Before measuring the gas content of the concrete mixture, the gas content of the aggregate should be measured first. The method of measurement is as follows. Press to calculate the weight of coarse and fine aggregate in each sample. In the formula: WG and WS-respectively the weight of coarse and fine aggregate in each sample (KG) V-gas volume meter volume (liter) Gg and Cs-respectively the coarse and fine in each cubic meter of concrete Fine aggregate dosage (kg)
2. Hold three-thirds and one-height water in the measuring bowl, mix well the weighed coarse and fine aggregates, and slowly pour into the measuring bowl. When adding the sample, the air should be brought in as little as possible. When it is 20-30mm, it should be gently inserted 10 times, and agitated a little, tap the measuring bowl at any time to eliminate air. During the feeding process, the water surface should always be held above the top surface of the material. After all the aggregates are added, soak for another five minutes, and tap the wall of the measuring bowl to eliminate the air bubbles. .
3. Wipe the edge of the measuring bowl and the lid, place the O-shaped rubber seal (230 × 8.6) in the groove on the edge of the lid, cover the lid, and clamp it with a clip to make it airtight, and use a spirit level Check the level. For the remaining steps, the gas content C of the grade aggregate is measured according to the relevant regulations for the determination of the gas content of the concrete mixture.
5. Calculation of test results of concrete gas content tester

The gas content is calculated as follows:
A = A1-C
Among them: A-concrete mix volume (%)
A1-The instrument determines the gas content (%)
C-aggregate gas content (%)
Take the average of the two measured values ​​as the test result. If the two gas content measurements differ by more than 0.2%, the cause must be found and the test repeated.
Concrete gas content measuring instrument Concrete direct reading gas content measuring instrument
6. Calibration of the gas content of the instrument Each instrument is accurately calibrated before leaving the factory, and the calibration results are prepared, but it is calibrated from time to time to ensure the accuracy of the gas content measurement of the concrete mixture. It is also feasible. Calibration includes the following 3 steps:
1. Calibration of measuring bowl volume
a. Prepare a flat glass plate, weigh it with an empty measuring bowl W2 (accurate to 0.05kg);
b. Fill the container with water and slide it along the upper edge with a glass plate. Use a water injector to add water from time to time to fill the measuring bowl with water without bubbles under the glass plate. Weigh the measuring bowl filled with water with the glass plate In, the weight W1 (accurate to 0.05kg) is the volume V of the measuring bowl:
W = W1-W2 (W, W1, W2-kg)
V = W1-W2 (W, W1, W2-kg)
V = W / r (V-L)
r- Specific gravity of water at standard temperature (r-kg / L)
2. Calibration with 0% gas content.
a. Fill the measuring bowl with water and connect the calibration tube 2 to the end of the small faucet under the lid.
b. Open the small faucet, put the lid on the measuring bowl, clamp it with a clamp, and check the level of the instrument with a spirit level.
C. Open the air outlet valve, add water from the small faucet with a water injector until the outlet of the air outlet valve is filled with water, and then close the small faucet and the air outlet valve. Note: The space under the bowl cover must be completely filled with water, otherwise the reading will not reflect the correct gas content value.
d. Inflate and pressurize with a pump to make the gauge pressure slightly exceed 0.1MPA. After stopping for 5 seconds, adjust the pressure with a fine adjustment valve to make the gauge pressure accurately stop at 0.1MPA. Tap the dial, the gauge pressure is still 0.1MPA Then press the valve lever 2-3 times to balance the pressure of the gas chamber and the pressure of the measuring bowl. The value read from the pressure gauge is equivalent to 0% of the gas content.
3. After the gas content of 1% -10% of the calibration instrument with a gas content of 0% is calibrated, connect the calibration tube 1 to the upper end of the small faucet of the bowl cover, and suck the water from the measuring bowl into the measuring cylinder through the calibration tube 1. The specific operation method is as follows:
a. Press the valve lever and slowly open the small faucet. The water in the measuring bowl flows into the measuring cylinder through the calibration tube 1. If the water flow is not smooth, first close the small faucet.
b. Open the air outlet valve to balance the pressure in the measuring bowl with the atmospheric pressure, then close the air outlet valve, pressurize with a pump to make the gauge pressure slightly exceed 0.1MPA, and stop for 5 seconds.
C. Adjust the pressure with a fine-tuning valve to make the gauge pressure accurately stop on 0.1MPA, stop for 5 seconds, press the valve lever 2-3 times, after the pointer stabilizes, the pressure value read at this time is equivalent to the gas content 1 %, The same method measured 2%, 3%, 4%, … 10% of the pressure gauge reading.
d. Calibrate 2 times strictly in the order of calibration. The obtained pressure gauge readings of 0%, 1% … 10% gas content points, the corresponding two readings, take their arithmetic average. Taking the average pressure as the abscissa and the gas content as the ordinate, the relationship between the gas content and the pressure value should be in accordance with Bozer’s law (p1v1 = p2v2). If a significant deviation is found, the cause should be found
The HC-7L new standard concrete gas content meter is independently developed and produced based on “General Concrete Mixture Performance Test Method” GB / T50080-2002, which is used to measure the air content in the mixture.
Concrete can be divided into two components, coarse aggregate and mortar. The size of the coarse aggregate particle size has almost no direct effect on the air content. The introduced air bubbles are distributed in the fine particles of the concrete, that is, the mortar, and the performance of the entire concrete is determined by the performance of the mortar.

The main technical parameters:
1. Volume: 7L
2. Gas content range: ≤10%
3. Maximum particle size of coarse aggregate: ≤40mm
4. Minimum reading: 0.1%
5. Design maximum pressure: 4MPa
6. Maximum working pressure: 0.4MPa
7. Air tightness test pressure: 0.4MPa
8. Weight: 11KG

Calibration of concrete gas content measuring instrument:
1. Wipe the inner surfaces of the measuring bowl and the lid with a damp cloth, and place the measuring bowl horizontally.
2. Put the freshly mixed concrete mixture into the measuring bowl evenly so that the concrete mixture is slightly higher than the measuring bowl. When loading, you can use a tamping rod to insert it slightly. After installation, when vibrating with a vibrating table (frequency of 50HZ, amplitude 0.5 ± 0.1mm under no load), the concrete will fall below the inner limit during vibration. At the mouth, the concrete mixture should be added at any time, vibrate until the concrete surface is flat, and stop vibrating when it is glazed. Instead of vibrating table, use real-time tamping for tamping. Load the concrete mixture into three layers. After tamping, each layer is about one-third of the height of the measuring bowl. The tamping rod should penetrate the entire depth when inserting the stratum. When inserting the upper layer, the tamper should be inserted into the lower layer 10-20mm. After each layer is tamped, the tamping rod can be placed on the lower part of the measuring bowl, and the measuring bowl is alternately struck on the ground left and right 15 times.
3. After the tamping is finished, immediately scrape off the excess concrete mixture on the surface with a scraper. If there are depressions on the surface, they should be filled in, then smooth it with a trowel and make the surface smooth without bubbles.
4. Wipe the edge of the measuring bowl and the lid, place the O-shaped rubber sealing ring (238 × 8.6) in the groove on the edge of the lid, cover the lid, clamp with a clip to make it airtight, and use a spirit level Check the level.
5. Open the faucet and outlet valve, use a water injector to pour water into the measuring bowl from the small faucet until the water flows out of the air valve port, and then close the small faucet and the outlet valve tightly. 6. Close all the valves and pressurize with a pump to make the gauge pressure slightly greater than 0.1MPA. Note: 1. When reading the pressure, flick the dial with your fingertip and wait until the pointer stops swinging before reading. 2. The 0.1MPA pressure line is the initial pressure line of the instrument, and 0.1MPA is the initial pressure of the instrument.
7. Press the valve stem 2-3 times, tap the circumference of the measuring bowl with a wooden beater to distribute the pressure evenly throughout the sample, press the valve stem again, and after the pressure gauge pointer stabilizes, measure the pressure gauge degree, According to the relationship between the gas content calibrated by the instrument and the reading of the pressure gauge, the gas content A value of the sample of the measured concrete mixture is obtained by the instrument. After the test,
1. Open the gas outlet valve to prevent gas from the measuring bowl. If it is necessary to repeatedly measure the gas content of the same sample, repeat steps 5-7 above.
2. Open the small faucet, release the clip, and remove the lid.
3. Pour out the sample of the concrete mixture in the measuring bowl and clean the inner surface of the bowl lid and the measuring bowl.
4. If Yaxing gas content measuring instrument is used continuously. Need to open the fine adjustment valve to deflate, so that the pressure in the gas chamber is consistent with the atmosphere. Note: During the operation, if the air chamber pressure is exhausted through the trim valve, and there is still pressure in the measuring bowl, the valve rod must never be pressed, otherwise water will be drawn into the air chamber, which will cause errors in subsequent tests.
Instructions:
a. The concrete mixture is evenly charged into the measuring bowl and shaken for 15-30s after shaking. b. Scrape the concrete, the surface is smooth without bubbles.
c. Cover the bowl, fill the vector bowl with water until the water flows out of the outlet, and close the faucet and exhaust valve tightly.
d. Pressurize and pressurize in the vector bowl. The gauge pressure is greater than 0.1 MPa. Use the fine adjustment valve to be accurate to 0.1 MPa.
e. Press the valve stem 1-2 times, measure the pressure gauge reading, and determine the gas content A1 according to the calibration curve.
f. The gas content C of the aggregate is measured by water pressure method.
g. Calculation of results: A = A1-C
Taking the average of the two measured values ​​as the result, the difference between the two measured values ​​is more than 0.2%, find out the reason and repeat the test [1] 6 Technical parameters of the gas content tester of the gas content calibration process Volume of the measuring bowl: 7 litres Depth is equal) Gas content range: ≤10% Maximum particle size of coarse aggregate used: ≤40mm
Precautions for use:
2. The personnel who use the concrete gas content tester for the first time must operate under the guidance of a skilled person.
3. The concrete gas content measuring instrument used in the experiment should be arranged reasonably, neatly arranged, easy to operate, observe and record.