SURFACE DAMAGE OF SLAG-CEMENT CONCRETE STRUCTURE EXPOSED TO DEICING-FROST CONDITIONS

The deicing-frost experimentation with test beams made of ordinary Portland cement concrete (OPC), air-entrained Portland cement concrete (APC) and high performance concrete (HPC) subjected to the action of 3.5% (mass fraction) sodium chloride (NaCl) solution was studied by the accelerated freezing method. Adopting to ultrasonic testing method, the surface damaged thickness of concrete structure was detected, and a new evaluation index was put forward, the deicing-frost damaged degree. The results show that the deicing-frost damaged degree of OPC increases sharply and linearly with increase of freeze-thawing cycle. But the addition of air-entrained admixture can efficiently not only decrease deicing-frost damaged degree of the concrete but also enhance its deicing-frost resistance. The deicer-frosting-resistance of air-entrained HPC is prodigiously influenced by the amount of mineral admixtures. Air-entrained HPC with 50%SG (50% of binder mass) has strongest deicing-frost resistance, and its typical characteristic is that the deicing-frost damaged degree decreases and in the later period it increases very slowly. Finally, Minimum cover depth of concrete structure exposed to deicing-frost conditions was discussed, and some regulation required by Code for Design of Highway Reinforced Concrete and Prestressed Concrete Bridge and Culverts (JTG D62-2004) was insecure by considered.