This study is attempted to investigate the change in mechanical properties and to formulate the stress-strain models of air-entrained (AE) and non-air entrained high strength concrete with blast furnace slag (BFS) sand as fine aggregates under freezing and thawing. The freeze-thaw (FT) test was carried out on the concrete specimens followed by static compression tests and the results are compared with those of AE normal strength normal (AENSN) and AE high strength normal (AEHSN) concrete using crushed sand. The experimental results disclose that overall the rate of plastic strain development due to freezing and thawing in non-AE high strength concrete is higher than that of AE high strength concrete, but less than that of companion normal strength concrete. Consequently, the mechanical properties of non-AE concrete deteriorate at higher rate in comparison with AE concrete under freezing and thawing. However, no significant reduction in mechanical properties of AEBFS and AEHSN concrete is observed compared to AENSN concrete. Moreover, it is found that the Young's modulus of frost-damaged concrete degrades rapidly than the compressive strength. Thereafter, the stress-strain relationships for AE and non-AE high strength concrete under monotonic loading are formulated based on elasto-plastic and fracture concept. Based on the experimental data, the relationships for fracture parameter and plastic strain development of high strength concrete under monotonic loading are developed. The stres-strain relationships calculated by the proposed model are compared with the experimental ones.
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