Sammendrag
Air-entrainment is difficult with high volumes of Supplementary Cementitious Materials (SCM). High Performance Concrete (HPC) with low w/b without air-entrainment can, however, survive severe deicer salt frost performance testing, eliminating all the hassle of producing air entrained concrete. Therefore, the surface scaling of low-CO2-emission concretes was studied in freeze/thaw performance tests with a 3 mm layer of 3% NaCl on the surface. Four different non-air entrained silica fume-fly ash concrete mixes with w/b = 0.30 – 0.35 with 91d strengths >100 MPa were investigated after 3 different curing conditions (Normal, Dried, Wrapped). The w/b=0.30 CEM IIA reference mix without additional FA had lowest scaling following all curing conditions. However, all 4 mixes and 3 curing conditions suffered severe internal damage. Liquid Uptake (LU) during freeze/thaw related best to internal damage, whereas the correlation LU-scaling and strain-scaling were weaker. A parametric analysis of glue-spall stress as affected by internal cracking was made with increasing differential thermal expansion (Da) due to internal cracking and Poisson ratio (v) equal to zero in severely cracked concrete assuming compression closes cracks without lateral deformation. An experimentally based model for elastic modulus (E) as function of cracking was employed. The analysis shows that glue spall stress reduced by reduced ice thickness due to LU while internal damage (reduced E and v, increased Da) affects glue spall stress directly and indirectly by the same order of magnitude as 1 – 2 mm reduction of ice thickness. LU must be accounted for in modelling scaling.
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