Test | Measuring Air Content in Hydraulic Roller-Compacted Concrete

Introduction to the straight read air content meter

According to the Mariner Concrete Test Protocol (SL-T352-2020) 7.3The air concentrator is very important in determining the air contente of the roller-compacted concerete. Concrete in the cold zone needs control over the appropriate air content to ensure durability.

Generally measured concretair content isDirectly Read Concreteair content, the device applies to the maximum particle size of the bone $\le$ 40mm，air content$\le$ 10% concrete blending test.

Straight-reading air content meter principles

The concrete direct read air content is based on the principle thatBoyle’s Law(i.e., the ideal simplified form of the gas equation) is determined directly by pressure balance by air content.

$$PV=C(Constant)$$

• Reload and seal.

Load the new corcrete layer with volume sprawling, as specified, to level the surface to ensure that the loaded concrete volume equals volume of the mound (known as ” VolumeThe cover is covered and sealed so that the system remains intact.

• Water to the base

The process is to fill all the spaces in the filler, except the concrete solid particles themselves, which contain the microbush (air) in the concrete and the gap between the particles (at this point filled by water).

At this point, the total amount of space not occupied by solids in the mass (known as compressable space volume) is equal to the volume of volume mulch minus the total volume of absolute solid particles in concrete. This space contains water (non-compressible) and air (compressable).

• Pressure chamber (initial status)

Closes the valves connecting the air chamber and the volume of the turbo.$P_1$）。 At this point, the gas chamber is sealed with a certain mass of gas, and its volume is the air chamber’s fixed volume.$V_a$- What? $P_1$。

• Connectivity and balance (core step air room connectivity)

Open the valves that connect the air chamber and the Quantum. The air chamber is under pressure. $P_1$The gas is rapidly expanding and the amount of compressable space in the influx is intensible. Gas expansion caused the system to drop pressure (air chamber volume + compressable space in volume) and eventually reached a new equilibrium, with pressure sheets indicating the final balance pressure$P_2$。 According to the law of Boear (no change in temperature and gas mass), the pressure and volume of the initial gas chamber state equal to the pressure and volume of the pressure and volume of the system ’ s interconnection balance can be derived from:

$$P_1\times V_a=P_2\times (V_a+V_{air})$$

The blogger writes:$V_{air}$ The volume of the mass can be compressed to the size of the space that is actually occupied by air (compressable parts), that is, the volume of the concretair content that we need to measure.

• Air content deduce

The formula of the Boear law can be deformed to deform the air volume.$V_{air}$：

$$V_{air}=V_a\left(\frac{P_1}{P_2}-1\right)$$

I’m going to be a good man. $A$Defines air volume as concrete total (i.e. volume muctuation)$V_B$(Percentage:

$$A(\%)=\frac{V_{air}}{V_B}\times 100\%$$

Will $V_{air}$Into the top, you can get:

$$A=\left[\frac{V_a\times \left(\frac{P_1}{P_2}-1\right)}{V_B}\right]\times 100\%$$

• Marked roles

The instrument manufacturer or user must be marked before using it (usually using water or standard calibration columns known to be zero for air content). The central roles identified are:

1. Determine Constant $K$Because of the air chamber volume$V_a$and volume$V_B$ It’s the fixed value inherent in the instrument. $K=\frac{V_a}{V_b}\times 100\%$It’s a constant.
2. Fixed initial pressure$P_1$: determine standard operating pressure.

When marked, the typographical or internal circuits of the pressure table (or display device) are calculated according to the formula $A=K\times \left(\frac{P_1}{P_2}-1\right)$Design and calibration. Therefore, the operator simply reads the final pressure of the connection balance $P_2$, the instrument automatically calculates and shows the air percentage directly $A$ , which is not manually calculated, achieves “direct reading”.

The hydraulic roller-compacted concret determination process

The air content test should be pre-rated. And then we’ll be doing the test of the roller-compacted concrett.

1. (a) Plugger 15L, sifting and even mixing of bone material greater than 40 mm in diameter using wet sifting;
2. (a) Mixing concrete, which sifts the bone material greater than 40 mm wet;
3. Wet cloths, wetners, load concrete blends, vibrate with the stage, and the vibrate should be 15 times.~30s to concrete surface slurry (if artificially tampered, blended and material in two layers, 25 times per layer). Scratch excess concrete blends with a scavenging knife, carefully level the barrel mouth, smooth the surface without bubbles. Wipe the pineapple tube, cover it and tighten the cover;
4. Close the valves and open the water valves and drain valves and pour the water from the water valves. After the drain valves are released, the drain valves are slightly tilted up, the air confent instrument is lightly shaking from the drain valves to the gas, and then the drain valves are leveled until the drain valves are out of the water without bubbles, and the flow valves are shut down. Pressure is pressed to control the drain valves over initial pressure and to adjust to the initial pressure. Open the air chamber valves to connect the air chamber to the container, and the signal table values are read after pressure is balanced.