Introducing the Porous Plant Concrete Permeability Tester: A Detailed Overview
The self-designed equipment used in this experiment is a porous phytosanitary water permeability tester. This device is composed of several key components, including a fixing device, a testing device, a water supply system, and a drainage system. The test specimen used is a cylindrical piece of porous planted concrete.
The fixing device consists of two vertical columns with a bottom plate fixed at the base. Between these columns, an upper sliding platform and a lower sliding platform are installed, allowing vertical movement along the column axis. This structure provides flexibility during the testing process.
The testing device includes a test piece sleeve that can accommodate the cylindrical test sample. The sleeve is designed with a rubber sleeve on its outer wall to ensure a tight seal around the test piece. A top cover is placed on the sleeve, equipped with a water inlet at the top and a water outlet at the bottom. These are connected via a passage, allowing water to flow through the test piece.
The base of the testing device is made up of an upper cylinder and a lower cylinder. The upper cylinder has a smaller cross-section than the lower one, and it contains multiple water-permeable holes that connect to the inner cavity of the lower cylinder. A drain pipe with a second water stop valve is attached to the side of the lower cylinder for controlled drainage. The lower cylinder is mounted on the lower sliding platform.
The water supply system features a transparent acrylic container with an overflow port. A water supply pipe is connected to the bottom of the container, equipped with a first water stop valve. The end of this pipe connects to the water inlet of the top cover. The water supply container is placed on the upper sliding platform, ensuring a steady water supply during the test.
The drainage system includes a drainage container with an overflow opening. It is connected to the drain pipe on the side of the lower cylinder, allowing collected water to be measured accurately.
A scale is also included, fixed to the base plate, enabling direct measurement of liquid level differences between the water supply and drainage containers.
This design is simple, cost-effective, and easy to produce. During testing, the test piece is placed inside the sleeve and covered with a rubber sleeve slightly smaller than the test piece, preventing leaks between the specimen and the sleeve walls. The rubber sleeves are folded over the outer surface of the test piece sleeve and secured with rubber bands on both ends to ensure a tight seal, eliminating side leakage and improving measurement accuracy. The setup allows for easy installation and sealing of the test piece.
Water flows from the top cap through the test piece and into the base, then drains into the drainage container. By adjusting the positions of the upper and lower sliding platforms, the pressure difference can be controlled, ensuring accurate permeability measurements. The millimeter-scale ruler on the column allows for direct reading of the water level difference between the two containers.
Preferred dimensions include a top cap with a diameter of 100 mm and height of 30 mm, a test piece sleeve with a diameter of 105 mm and height of 70 mm, made from PVC. The upper cylinder of the base has a diameter of 100 mm and height of 25 mm, while the lower cylinder has a diameter of 250 mm and height of 25 mm. These sizes ensure a balanced and precise instrument, making it easier to handle.
The water supply and drainage pipes have an inner diameter greater than 10 mm, which helps reduce pressure loss and improves pressure transmission efficiency.
The cross-sections of the test piece sleeve, top cap, and base are all circular, with the same cross-sectional dimensions for the top cap and base. The test piece sleeve is slightly larger than the test piece itself, facilitating a secure fit. The base is designed as two separate cylinders, with the upper part matching the test piece size and the lower part optimized for drainage and sealing. This configuration ensures better performance compared to a single-cylinder design.
The test piece sleeve is designed to be detachable from the water inlet, drainage container, base, and top cap, allowing for easy assembly and disassembly.
The procedure for determining the permeability coefficient using this device involves the following steps:
- Preparation: Check all components and instruments to ensure proper connection and airtightness.
- Fill the water supply and drainage containers to a constant level and maintain the normal water head by closing the first and second water stop valves.
- Place the rubber sleeve (a round sleeve) around the test piece, then insert the test piece into the sleeve. Pull the rubber sleeve over the test piece to ensure full coverage. Secure the rubber sleeves on both ends of the test piece onto the upper cylinder of the top cap and the base, and fasten them with rubber bands.
- Open the first and second water stop valves and continuously fill the water supply container, keeping the water level constant until the overflow from the drainage container stabilizes.
- Once the flow is stable, measure the volume of water collected in a beaker over a set period and weigh the collected water using an electronic balance.
- Record the temperature of the water during the test.
- Repeat the measurement process and take an average of the results for accuracy.
- After completing the test, remove the test piece in reverse order and replace it with a new one for the next test.
Name of the Device: Porous Plant Concrete Permeability Tester
Developed by: Ningbo University of Science and Technology, Zhejiang University
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