The frost resistance of concrete is an important index to reflect the durability of concrete. When some special projects or special parts of projects have anti-freezing requirements, anti-freezing specimens must be retained for anti-freezing test.
The frost resistance of concrete is expressed by frost resistance label or durability coefficient. The frost resistance label is based on the number of freeze-thaw cycles that concrete samples can withstand. The durability coefficient is obtained by calculating the number of freeze-thaw cycles and the relative dynamic elastic modulus. The frost resistance test of concrete shall comply with the provisions of Test Method for Long-term Performance and Durability of Ordinary Concrete (GBJ82).
The frost resistance label of concrete is divided into nine labels: D 10, D 15, D25, D50, D 100 and D 15d. D200, D250 and D300.
Concrete with frost resistance requirements must be issued by a qualified laboratory and meet the strength grade and frost resistance requirements at the same time.
Sampling rule: the mixture used to make the test piece should be stirred in the same plate or taken out of the same mixer. The same project, the same mixture ratio of concrete, sampling should not be less than once, the number of lien groups can be determined according to actual needs.
The test methods of frost resistance of concrete are divided into slow freezing method and fast freezing method.
(1) slow freezing method: it is suitable for determining the frost resistance of concrete according to the number of freeze-thaw cycles.
According to the aggregate particle size, the sizes of different specimens are100×100×100,150×150, 200×200×200mm respectively. Each group has three concrete specimens, and a certain number of specimens are reserved according to different labels.
The frost resistance label of concrete is expressed by the maximum number of cycles when the strength loss rate does not exceed 25% and the weight loss rate does not exceed 5%.
(2) Quick freezing method: it is suitable for quick freezing and thawing in water to measure the frost resistance of concrete and concrete with high frost resistance requirements. The frost resistance of concrete is expressed by the number of rapid freeze-thaw cycles or durability coefficient.
Use 100× 100×400 mm prism sample. Each group has three concrete specimens, which can be used continuously during the test. In addition to making freeze-thaw specimens, we should also prepare temperature specimens with the same shape and size and a thermocouple buried in the center. The frost resistance of concrete used to make temperature measuring specimens should be higher than that of freeze-thaw specimens.
The test can be stopped when the freeze-thaw reaches one of the following three situations: ① it reaches 300 cycles; ② The relative dynamic elastic modulus decreased to below 60%; ③ The weight loss rate reached 5%.
The number of rapid deicing cycles of concrete should be expressed as the maximum number of cycles when the relative dynamic elastic modulus value is not less than 60% and the weight loss rate is not more than 5%.
The detailed information of "Requirements for Filling in Concrete Frost Resistance Test Report" can be found in Zhong Da Consulting and Design Link, and all relevant building construction information you want is available.
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