1. 20 EFFECT OF THE FREEZING RATE ON THE FROST RESISTANCE OF CONCRETE Geran Fagerlund Professor Division of Building Materials Lund Institute of Technology Box 118 S-221 00 LUND, SWEDEN ABSTRACT A limited literature survey shows that there is no univocal relation between the freezing rate in an unsealed test and the amount of frost damage. A theoretical analysis shows that the effect of the freezing rate on the destructive forces occuring during a sealed test is very limited, if any. This is also confirmed experimentally by tests in which the effect of the freezing rate on the critical degree of saturation is studied and found to be negligible. Therefore, the different and opposing effects of the freezing rate that have been observed in unsealed tests are no doubt mainly caused by the ef- fect that the shape of the freeze/ thaw cycle has on the maximum water content that is reached in the speci- men during the test. Key words: Frost resistance, freeze/thaw testing, freezing rate, air pore distribution, destruction mechanism. THE FREEZING RATE In this report rate of freezing is defined as the rate by which the temperature of the specimen is lowered; i. e. the rate of cooling of the specimen. This is roughly proportional to the rate by which the air or water surrounding the specimen is cool- ed. However, due to the latent heat of fusion of the pore-water the proportionality constant at a given temperature is a func- tion of that temperature. Fora coarse-porous material cogtain- ing a large amount of water that freezes somewhat below O C, the specimen temperature stays constant at that temperature fora considerable length of time despite the faet that the outer tem- perature decreases continuously, more or less rapidly. However,
EFFECT OF THE FREEZING RATE ON THE FROST RESISTANCE OF CONCRETE
May 12, 2023
A limited literature survey shows
that there is no univocal relation
between the freezing rate in an
unsealed test and the amount of
frost damage.
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A theoretical analysis shows that the effect of the freezing rate on the destructive forces occuring during a sealed test is very limited, if any. This is also confirmed experimentally by tests in which the effect of the freezing rate on the critical degree of saturation is studied and found to be negligible.
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