Effects of freezing conditions on the frost resistance and microstructure of concrete

• Type and intensity of frost damage were affected by freezing conditions. • Amount and size of air voids were changed depending on the type of admixture. • Importance of strength of concrete concerning frost damage was investigated. • A severe scaling tests can be conducted by applying a slow freezing rate and exposure time at minimum temperature. • Microstructural examinations indicated the location and depth of the damage. Repeated freezing and thawing (F-T) cycles are the major reason for the frost damage and premature failure in concrete structures. Frost damage can be evaluated by its effects on formation of internal cracks and scaling at the surface of concrete. Both internal frost damage and surface scaling mechanisms depend on several environmental factors such as the rate of freezing, minimum temperature and the duration at the minimum temperature. The objective of this study is to investigate the effects of freezing conditions on the type and intensity of damage, and on microstructure of concrete. Investigations, within the scope of this research, indicated that freezing conditions significantly affect the F-T resistance assessment of the concrete mixtures. Microstructural examinations also revealed the severity of the scaling under slower freezing rate and longer exposure time at the minimum temperature. Therefore, examination of the local freezing and thawing regime is crucial for designing durable and sustainable concrete structures.