コンクリート中の鉄筋の腐食 (第2報)

水中に浸漬されたモルタル中の鉄筋の電食および海水混ねりモルタル中の鉄筋の腐食

抄録

Stray current corrosion of reinforced concrete, which was immersed in tap water and 10% Na₂SO₄ solution, was studied. The steel electrode in the mortar and the auxiliary electrode made of steel plate ware connected to the anode- and cathode-terminals of the battery respectively, and the voltage applied between two electrodes was 1.2 or 1.5 volts. The mortar containing either none or 2% CaCl₂ was used. The mortar containing 2% CaCl₂ cracked even in the small degree of corrosion (15-20mg/cm²) of the steel in the mortar. It seems that cracking of the mortar is caused not only by increase in volume of rusty steel, but by the corelated effect of change in volume of rusty steel and contractibility of the mortar.
The corrosion of the reinforcing bar within the mortar (mortar-S), prepared with sea water or 3% NaCl solution, were studied by the socalled R. G. Y. test. Following results were obtained:
1) By immersing the mortar-S into tap water, the reinforcing bar was slightly corroded.
2) Since, in sea water, the corrosion behabior of the reinforcing bar within the mortar-S was equal to that within the mortar (mortar-C) prepared with tap water, seemingly, the mortar-S may be useful in sea water.
3) The early mechanical strength of the mortar-S was larger than that of the mortar-C, but the final strength of these mortars was reversed.