Concrete is a widely used artificial stone in modern construction. For certain types of structures—such as hydraulic structures, underwater, submerged, underground, and other engineering projects—buildings are required to possess special performance characteristics: impermeability. So-called impermeability refers to the ability of the materials used in a structure to resist the penetration of water or other liquids (such as light oil and heavy oil) under pressure.

The HS-4 permeability tester is primarily used for concrete permeability tests and the determination of permeability grades. It can also be employed to measure the air permeability of construction materials and conduct quality inspections, which is why it has been widely adopted by departments involved in production, construction, design, and research & development.

Main Technical Parameters

Main Working Principle and Its Mechanism (See Figure 1)

1. Principle

The HS-4 permeability tester and the HP-4.0 digital permeability tester operate on the principle that pressure is uniform throughout a sealed container (with water level differences being negligible). A water pump supplies pressure to the entire system, and by adjusting the pressure via an electrical contact pressure gauge or a pressure controller, pressurized water is forced to permeate upward through the specimens housed in the test mold, thereby enabling the determination of the specimens’ impermeability performance and the calculation of their impermeability grade.

2. Structure

It mainly consists of a cabinet and a workbench made of stainless steel panels, equipped with 6 mold bases and 36 M12 bolts for installing test molds.

3. Pressurization System

It consists of an electric motor, a power unit, a water pump, a water tank, a safety valve, piping, and other components. The electric motor serves as the power source for the system, while the power unit converts the power supplied by the electric motor into reciprocating motion and transmits it to the water pump. The water pump is responsible for providing water pressure throughout the system, and the water tank stabilizes the system’s water pressure and acts as a water pressure source. The power unit converts the power delivered by the electric motor into reciprocating motion and supplies it to the water pressure system, while also diverting a portion of the water pressure to serve as a secondary pressure source. The safety valve is installed at the center of the water tank; its function is to ensure that the system pressure does not exceed 4 MPa.

4. Workbench

It is primarily composed of electrical controls and control valves. The system consists of red and green push-button switches and a single electrical contact pressure gauge: the green button serves as the start switch, while the red button acts as the stop switch. The electrical contact pressure gauge is used to maintain the pressure in the pressurization system within the range you require—when the pressure pointer reaches the upper limit, the water pump stops operating. Due to factors such as specimen permeability, the water pressure will drop, causing the pointer to rotate counterclockwise and move away from the upper limit until it reaches the lower limit, at which point the water pump restarts and the water pressure rises back to the upper limit. (2) Control Valves: Their opening and closing functions are identical to those of conventional valves—turning clockwise closes the valve, while rotating counterclockwise opens it. Each valve corresponds to and controls a single test mold. (3) Electrical Control Section: This section comprises a combination switch connected to a controller equipped with a single pressure sensor. The combination switch controls the power supply to the permeability tester; “0” represents the off position, while “1” indicates the on position. The controller is used to regulate the pressure in the pressurization system, keeping it within the range you need. For detailed operating instructions regarding the controller, please refer to Appendix “Operating Instructions for the Digital Display Permeability Tester Pressure Controller.”

Installation and Use

1. Preparation

a. Place the impermeability testing apparatus on a level, solid indoor foundation.

b. Close the drain and pressure relief valve located in the lower right corner of the housing.

c. Open the six control valves

d. For first-time use, fill the tank with water, open the control valve, and turn on the power until water overflows from all six mold cavities, thereby venting the air from the system.

e. Close the control valve

2. Specimen Fabrication and Installation

a. The test specimens shall be molded and cured according to the material mix proportions specified in the design, using a molding mold (also known as a secondary mold), and then subjected to curing in accordance with relevant national or international standards.

b. Dry the surface of the cured specimens, then apply molten sealing material (such as shellac or sealing wax) to their sides, taking care to avoid applying any sealing material to the end faces of the specimens.

c. Heat the mold to 40°C, then place the specimen coated with sealing material into the mold cavity. Next, use a press—either a screw press or a pressure testing machine borrowed from the laboratory—to compress the specimen into the mold and cool it down to room temperature. Ideally, use the DL-200KN hydraulic demolding machine manufactured by our own factory, which can both load and demold specimens while also splitting them to observe the depth of water penetration.

d. Install the test mold containing the compacted specimen onto the working table of the permeability tester and evenly tighten the screw caps.

3. Connect the power supply and turn on the red signal lights. Adjust the upper limit pointer of the electrical contact pressure gauge to 0.1 MPa, ensuring that the lower limit pointer is close to but does not simultaneously make contact with the upper limit pointer (approximately 0.05 MPa below the upper limit). Then, press the green button to start the power supply; the water pump will begin operating, and the pointer on the electrical contact pressure gauge will rotate clockwise as the water pressure rises. Pay close attention to whether the pressure rise is normal and check for any signs of leakage in the system. If any abnormalities are detected, they must be resolved before proceeding with the test. Follow the operating instructions provided in the appendix.

4. Open the control valve to apply water pressure to the corresponding test specimen. Carefully observe whether there is any leakage at the bottom of the test mold; if leakage occurs, tighten the compression nuts at the corresponding locations.

5. After the test enters normal operation, increase the working pressure by 0.1 MPa every 8 hours, and monitor the end faces of the specimens at all times for any signs of water leakage. If leakage is detected, close the corresponding control valve.

6. When pressure water begins to seep from the end faces of 3 out of the 6 specimens, the test may be stopped, and the water pressure at that point—recorded in tenths of a millimeter—shall be used as the basis for calculation.

7. Once the test is complete, disconnect the power supply, open the drain and pressure relief valve to reduce the system pressure to zero, then remove the test mold.

8. Demold the test specimens, then clean the mold, mold base, and apply rust‑preventive oil for future use.

Result Calculation

1. The concrete impermeability grade is expressed as the maximum water pressure at which four out of six specimens in a test group remain free from water penetration. The calculation formula is: S = 10H – 1, where: S = impermeability grade; H = the pressure (in MPa) at which the third specimen in the six‑specimen group begins to show signs of water penetration.

2. If the pressure is increased to 1.2 MPa and held for 8 hours, and the water leakage does not exceed 2 points, the concrete’s impermeability grade should be greater than or equal to 12, i.e., S = 12.

Maintenance and Care

1. Requirements for the working environment: Ambient air temperature should be between 5°C and 45°C; relative humidity should be less than 80%, and the equipment should not operate continuously in environments containing corrosive gases.

2. The water source should be clean and free of impurities.

3. The power box is pre-filled with oil at the factory. Thereafter, every six months, open the rear cover and the power box cover to replace the 20‑ or 30‑grade mechanical lubricating oil once. The oil level should be topped up until it reaches approximately the center of the main spindle (about 600 ml).

4. Inspect the bottom of the power box every six months for any accumulated water (this task can be carried out concurrently with oil changes), and determine whether the pump seal is damaged; if it is damaged, it must be replaced.

5. If the ambient temperature falls below 0°C, water must be drained and all water inside the relief valve must be completely emptied to prevent freezing and damage to system components.

Troubleshooting

The following solutions should be implemented after ruling out leakage at the connections of pipes, pumps, and valves.

1. If the system pressure takes a long time to build up at startup, it indicates that there is air in the pipeline; refer to the instructions for purging the air during initial use.

2. The system is not under pressure; typically, this is caused by worn seals inside the pump, resulting in poor sealing—replace them.

Instrument Packaging and Shipping

Before transportation, pack the product in wooden crates with a waterproof lining on the inner walls, and securely fasten the crates with bolts. During transport, the angle of inclination of the crate should not exceed 25°, and impacts and severe vibrations should be avoided.

The properties of mortar permeability testers are essentially the same as those of concrete. For certain special-purpose mortars—such as waterproofing mortar—requirements are also specified for impermeability, meaning that the mortar must possess the ability to resist the penetration of pressurized water. This mortar permeability tester can be used to determine the impermeability performance of mortar. By replacing the test molds and fixtures with other types, this mortar permeability tester can also be used to conduct tests on other waterproofing materials.

Main Technical Parameters

1. Maximum allowable pressure: 147 × 10⁴ Pa
2. Pump Parameters: Plunger Diameter 10 mm
3. Plunger reciprocation frequency: 54 cycles per minute
4. Flow rate: 0.1 liters/minute
5. Mold trial geometric dimensions: Φ70 × 80 × 30 mm
6. Number of test specimens per trial: 6
7. Automatic Constant Voltage and Manual Constant Voltage
8. External dimensions: 550 × 500 × 810 mm
9. Weight approximately 70 kg