THE EFFECT OF CRYSTALLINE COATINGS DEFECTS OF STEEL-CORROSION IN REINFORCED CONCRETE

Abstract

This study focus on corrosion behavior of reinforced concrete with crystalline coating materials. The efficiency of crystalline coating was considered comparing with different water to cement ratios. Determination of steel corrosion protection provides a comparison between the uncoated and coated concrete. This study was evaluated by using half-cell potential measurements in accordance with ASTM G109. The specimens were exposed to chloride environment, 5% NaCl solution by weight in wet-dry cycles. The coated concrete specimens were partly coated with crystalline material on top surface of the concrete. The coated area was considered defective to the different degrees 0, 1, 2 and 3%. A total of 90 specimens were cast with dimension 280 x 150 x 115 mm. The concrete was designed to have different water to cement ratios at 0.45, 0.50 and 0.60. The specimens had been exposed to humidity room environment for 365 days before coated. Half-cell potential of steel was measured at 0, 14, 21, 28, 42, 49 and 56 days. The results indicated that concrete with crystalline coating material performed better than uncoated concrete. The potential measured in all specimens were resemble regardless all of the defects on coated areas. The results of half-cell potential measurements indicate that there was reasonably no corrosion in coated concrete specimens. However, it revealed that the uncoated specimens with w/c ratios of 0.6 were attacked by corrosion. For the others mix of uncoated concrete, the corrosion activity gradually proceeded within duration of 56 days. By using difference water to cement ratios. It showed that the higher the water to cement ratios, the greater the probability of corrosion. In term of corrosion current density, the condition of the coated concrete rebar was found to be in passive condition but for the uncoated concrete, the result showed that the condition of the rebar was low to moderate corrosion. Crystalline coating materials delay the onset of corrosion in reinforced concrete under severe environment.