Dear reader we have discussed about ASTM C-33 specification for soundness of aggregates for concrete; where 8.1 and 8.2 defines specific values of weighted average losses of aggregates under sulfate salt solution and when 8.1 not passed the requirements of previous records are specified respectively.
When both 8.1 and 8.2 failed to pass, 8.3 defines that the aggregates sample should pass freezing and thawing test to be selected for using in concrete as sufficient sound aggregates.
Here we will discuss about freezing and thawing test. The German standard DIN 4226 provides a test method for freezing and thawing test as follows:
This standard specifies two methods for testing:
a. Total immersion freezing and thawing test
b. Air freezing and subsequent water thawing
Total immersion method of freezing and thawing test:
- The sample of aggregates cooled for duration of (7-10) hours to reach final temperature within (-15 ~ -20)0C
- At the final cooling temperature the sample is kept at least 4 hours.
- Then the sample is left in water of 200C for thawing and kept for 5 hours.
- The above freezing and thawing cycles are applied for ten times.
- Then the sample is dried and passes through next smaller sieve to determine loss in mass as percentage.
Air freezing and subsequent water thawing:
- Aggregate sample is soaked up to two hours
- Then left for drained
- Then they are left in freezing cabinet for 6 hours to reach temperature (-15~-20)0C
- Then the sample is left in water of 200C to thaw up to 1 hour.
- These cycles are repeated for 20 times
- The next procedure is same as that of total immersion method of freezing and thawing test.
Dear reader we are discussing these tests, as a material engineer have to approve constituents of concrete for better concrete having more durability which is sometimes a primary consideration for concrete mix design.
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