The concrete carbonation test chamber is a professional equipment that simulates the chemical reaction between carbon dioxide and cement hydration products in the atmospheric environment. Its core goal is to accelerate the carbonation process, evaluate the carbonation resistance of concrete, and the stability of the passive film on steel bars. The scientific and reasonable maintenance method directly determines the accuracy and reliability of the test results. The following elaborates on the key maintenance points from multiple dimensions:
1、 Accuracy of Box Environment Control
1. Constant temperature and humidity mechanism
-The temperature needs to be stably controlled at 20 ± 2 ℃, monitored in real-time using high-precision PT100 sensors, and combined with PID intelligent temperature control modules to achieve a fluctuation range of ± 0.5 ℃. Humidity management is achieved through dynamic balance between ultrasonic atomization humidifier and electronic dehumidification system, maintaining 70% ± 5% RH to avoid condensation or excessive drying on the surface of the specimen.
-The air circulation system inside the box adopts centrifugal fan forced convection to ensure that the concentration difference of CO ₂ in each area is ≤ 1%, and the distance between specimens is strictly maintained at ≥ 5cm to ensure airflow continuity.
2. Dynamic control of CO ₂ concentration
-Initial filling of food grade CO ₂ gas to target concentration (usually 20% ± 3%), automatically calibrated every 30 minutes using an infrared gas analyzer. When the concentration drops by more than 5%, the solenoid valve immediately replenishes air and starts the stirring fan to promote uniform diffusion.
-The air inlet is equipped with a 0.2 μ m precision filter to prevent impurities from interfering with the carbonization reaction.
2、 Specification for Preparation and Pre treatment of Test Specimens
1. Molding and maintenance stage
-The test piece adopts a standard size (100 × 100 × 400mm prism), and after demolding, it is immediately moved into a standard curing room (20 ± 2 ℃, 95% RH) for 26 days of curing. On the 27th day, it is taken out for carbonization testing. At this stage, it is necessary to ensure that the humidity gradient inside the specimen is ≤ 3% to prevent uneven carbonization in the early stage.
2. Key preprocessing steps
-Before the experiment, place the specimen in a 60 ℃ oven at a constant temperature for 48 hours to reduce the moisture content to below 1%. Subsequently, seal the non test surface with paraffin, exposing only the carbonized surface, and control the thickness of the sealing layer at 2-3mm to prevent edge effects.
-Before placing the test piece in the test chamber, wipe the surface dust with an alcohol swab to avoid pollutants hindering the penetration of CO ₂.
3、 Dynamic maintenance during the experimental period
1. Stage detection strategy
-Stop the machine every 24 hours to take samples, spray 1% phenolphthalein ethanol solution for color development, and measure the depth of the non carbonized area. Strictly control the operation time within 10 minutes each time to reduce environmental disturbance inside the box.
-Synchronously record the CO ₂ concentration attenuation curve. If the detection value is below 18% for three consecutive times, immediately check the airtightness and replenish the gas.
2. Handling of abnormal situations
-When it is found that the aging of the sealing strip of the box door causes air leakage, the silicone rubber sealing ring needs to be replaced; When the humidity exceeds the standard and causes condensation, activate the emergency dehumidification program and check the smoothness of the drainage valve.
-If the test piece shows cracks or peeling or other damages, the test group should be terminated and the raw material ratio issue should be traced.
4、 Protective measures during long-term disuse
1. Dormancy maintenance of the box body
-Clean the residue on the inner wall, spray 75% ethanol for disinfection, and turn on the ultraviolet lamp for 30 minutes for sterilization. Before turning off the power, place a color changing silicone desiccant on the shelf to absorb residual moisture.
-Connect the CO ₂ pipeline to nitrogen and blow for 10 minutes to replace residual gas and prevent pipeline corrosion.
2. Periodic activation operation
-Power on and run for 4 hours every month, load the basic load (unloaded state), and test the efficiency of the refrigeration/heating system. Inject standard concentration CO ₂ gas every quarter to verify the linearity of sensor response.
5、 Data traceability and quality control
-Establish a three-dimensional digital archive: record the temperature/humidity/CO ₂ historical curves, color photos of specimens, and depth data for each experiment, and generate a PDF encrypted report.
-Every year, a third-party metrology institution is commissioned to conduct traceability calibration of sensors and issue CNAS certification certificates. Daily verification is conducted using standard carbonation depth blocks (pre embedded phenolphthalein indicators) for cross validation.