Durability of High-Strength Concrete with Silica Fume: Temperature Attack and Freezing-and-Thawing Cycles

This paper reports high-strength concrete behavior subjected to temperatures up to 200 degrees Celsius and 100 freezing and thawing cycles in regime of 8 hours in water at +20 degrees Celsius and 16 hours at -20 degrees Celsius (weekends in frost). The concrete is composed of 425 kg/m(3) of Portland cement of CEM I 42.5 type, 32 kg/m(3) of silica fume, 5.6 L/m(3) of superplasticizer Melment and has a W/C of 0.32. Compressive strength is 78.5 MPa at 28-day curing on cubes for temperature resistance tests and 63.1 MPa on prisms for freezing and thawing tests, both after 28-basic curing in 20 degrees Celsius/100% R.H. – air. Evident C-S-H dewaterization of the cement paste is observed between 100 degrees Celsius and 200 degrees Celsius. Initial shrinkage within 24-hour period due to rapid cooling is more detrimental on the cement past strength than shrinkage due to C-S-H dewatering at temperature elevation from 100 degrees Celsius to 200 degrees Celsius. The strength, elastic modulus and volume deformation of concrete are irreversibly influenced either by temperature elevation or rapid cooling to 20 degrees Celsius. Differences in strength, elastic modulus and shrinkage or expansion after 100 freezing and thawing cycles relative to those in water are negligible. The compressive strength of prisms subjected to 118-day freezing and thawing was 62.9 MPa, compared to 65.2 MPa for those kept in water.