This standard is applicable to compare the corrosion resistance of cement in environmental water containing sulfate or artificially prepared sulfate solution. GB 2420-1981 Rapid test method for cement resistance to sulfate attack GB2420-1981 standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Cement Sulfate Attack
Test Method
GB 2420-—81
Promulgated by the General Administration of Standards of the People's Republic of China
Implementation on October 1, 1981
This standard is applicable to the comparison of cement corrosion resistance in environmental water containing sulfates or artificially prepared sulfate solutions. This standard adopts 1:2.5 mortar, 10×10×60mm prism-shaped specimens, pressurized, 1d curing in a curing box, 7d 50°C water curing, and 28d room temperature erosion. The sand adopts standard sand with a particle size of 0.25~0.65mm. This standard mainly calculates the corrosion resistance coefficient based on the ratio of the flexural strength of the cement mortar specimen immersed in the erosion solution to the flexural strength of the same age in fresh water (immersion age is 28d) to compare the corrosion resistance of cement. 1. Instruments
1. Pressurized molding machine
The specimen is molded using a small jack press, and the maximum load must be above 1.5t
, see Figure 1.
Jack press
Figure 2 Electric anti-bending machine
2. Anti-bending machine
The specimen is broken using a small electric anti-bending machine, see Figure 2, with a loading speed of 80g/s.
The three-joint model with a specimen size of 10×10×60mm is shown in Figure 3, and is composed of a partition 1, an end plate 2, and a base 3. After assembly, the contact surfaces of the inner wall should be perpendicular to each other, and its effective dimensions are shown in the table. The test mold should be made of stainless steel, and the upper surfaces of the partition, end plate and bottom must be ground flat.
Permissible size after grinding (mm)
Triple mold
Manufacturing size (mm)
Triple test mold
1-two plates, 2-straining plate, 3-hemp seat
4. Spherical mixing pot: diameter 200mm, height 70mm, thickness 1~2mm.
5. Small steel spoon: see Figure 4.
Figure Small steel spoon
2. Materials
. The cement sample is fully mixed and passed through a 0.9mm square hole sieve. 7. Standard sand should meet the quality requirements of GB178-77 "Standard Copy for Cement Strength Test".
8. The test water should be clean fresh water that does not interfere with the test results. Temperature,
9. The test case temperature is 17~25°C, the relative humidity is greater than 50%, and the temperature of cement specimens, standard sand, mixing water, etc. should be in phase with the temperature. 10. The temperature of the curing box is 20±3, and the relative humidity is greater than 90%. 11. The temperature of the curing water before soaking is 50±1°C. 12. The temperature of the etching liquid is 20+3°C.
IV. Specimen molding
13. Before molding, clean the test mold, assemble it tightly, and apply a thin layer of engine oil on the inner wall.
11. The weight ratio of cement to standard sand is 1:2.5, and the water-cement ratio is set at 0.515. Weigh 100g of cement sample and 250g of sand, put them into the mixing pot, use a small spoon to drain for 1min to mix the cement and sand evenly, add 50ml of water, drain for 3min, and put the mortar into 6 triple molds respectively. Use a small moon to insert it firmly during molding. Pay special attention to inserting the two ends of the test body several times, then put the mortar close to the edge of the mold sleeve, and then insert the mold core into the mold. Put the test mold with the mold core on a small jack press and pressurize it to 80kg/cm for 5s, then take out the test mold, scrape it flat, number it, put it in a curing box for 24±2h, and demold it. V. Curing and Erosion of Specimens
16. After demoulding, the specimens are placed in 50°C water (high alumina cement in 20°C water) for curing for 7 days, and then taken out and divided into two groups. One group of nine pieces are placed in 20°C water for curing, and the other group of nine pieces are placed in sulfate etching solution for soaking. Artificially prepared sulfate solution uses 3% chemically pure anhydrous sodium sulfate (SO4, 20250mg/L).
Fluorescence: According to requirements, natural environmental water can be used, and the concentration of sodium sulfate can also be changed. 17. During the soaking process, the specimen is titrated with 1NH4SO4 once a day to neutralize the Ca(OH)2 released by the specimen in the solution. Stirring while titrating keeps the pH of the solution at about 7.0.
Phenol red can be used as an indicator.
Standard: The specimen is allowed to stand still in the silicate solution. 18. When the specimen is not soaked in the container, each specimen must have 200mL of etching solution, and the liquid level must be at least 10mm above the surface of the specimen. To avoid evaporation, the container must be covered.
VI. Specimen Forming
19. After the specimen is cured in 20°C water for 28 days and soaked in sulfate solution for 139
28 days, it is taken out and subjected to a small anti-bending machine for anti-bending test. The fulcrum span is 50mm, the support column diameter is 5mm, and the loading speed is controlled at 80g/s. The slow etching period can be increased according to actual conditions. 20. Before breaking the mold, the moisture and sand on the surface of the specimen must be wiped off, and the debris adhering to the surface of the fulcrum cylinder must be removed. When the specimen is placed on the anti-bending fulcrum, the side should be in contact with the cylinder.
VII. Calculation of resultsbzxZ.net
21. The ultimate flexural strength of the specimen (kg/cm2) is obtained by multiplying the breaking load by 7.5, and the flexural strength is calculated to 0.1kg. 22. The flexural strength of the specimen is calculated by removing the maximum and minimum values ​​of the breaking loads of 9 specimens and taking the average value of the remaining 7 specimens. 23 The corrosion resistance of various cements in the silly corrosion solution is compared by the corrosion resistance coefficient 140
. The corrosion resistance coefficient refers to the ratio of the flexural strength of cement mortar specimens of the same age immersed in sulfate solution and cured in 20°C water, expressed in special, and calculated accurately to 0.01. And calculated by the following formula: Re
Corrosion resistance
R---The flexural strength of the specimen immersed in the solution for 28 days, kg/cm; the flexural strength of the specimen cured in 20fC water for the same age, kgR
Additional instructions:
This standard is proposed by the Ministry of Building Materials Industry of the People's Republic of China. This standard is drafted by the Chinese Academy of Building Materials Science and Technology. Service new, price ww1h travel management meal delivery, secret drink fresh replacement lock green box Ying 60 fee
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