PROGNOSIS OF DURABILITY OF CONCRETE BY EVALUATING FREEZING AND THAWING CYCLES
Keywords:freeze-thaw cycling, durability of concrete, hydraulic structures
Hydraulic structures are exploited in hard environmental conditions (impact of freeze-thaw cycling, ultraviolet, humidity and drying, acidity or salinity of water, abrasion etc.), so due to the impact of environmental factors some deteriorations will occur. The repeated cycles of freezing and thawing have significant effects on durability of concrete. They reducing durability, because of cracking and scaling of concrete. Using the research results of investigated hydraulic structures concrete average compression strength fck, water absorption by weight Wm, by formulae (1, 2) were calculated numbers of laboratory freeze-thaw cycles n50, freeze-thaw resistance of concrete rate F5 % and from them – durability index – probable deterioration start time T5 % of investigated main hydraulic structures .( concrete strength fck loss in 5 % and 5 freeze-thaw cycles per year).
Relationships between shaft spillway or retaining wall freeze-thaw resistance of concrete rate F5 % , durability index T5 % , and average compression strength of concrete fck were evaluated. These equations may be used for the durability prognosis of existing shaft spillways or retaining walls exploited in hydraulic structures.