The Effect of Crystalline Waterproofing Materials on Accelerated Corrosion of Steel Reinforcement in Concrete

Abstract

This research aimed to investigate the effects of two types of crystalline waterproofing materials (CWPM): surface coating and admixture mixing type, on the corrosion behavior of reinforced concrete. For the first type, the effects of curing and different degrees of the defective coating (0.1 and 2% of the area) were investigated. For the second type, different dosages of crystalline waterproofing material admixtures (0.5, 0.8, 1, and 2% of cement content by weight) were studied. Impressed voltage was used to accelerate the steel corrosion. Compressive strength, time to initiate the observed first crack, and rust stain and corrosion extent of steel were studied. The results showed that while both crystalline types yielded improved compressive strength, both short- and long-term strength of mixing type specimens were significantly higher than those of the coated specimens. The benefit increased with the increase in dosage and age. In terms of steel corrosion, the mixing type seemed to indicate improved corrosion resistance. The 2% addition provided the most advantageous effects by delaying the onset of corrosion in reinforced concrete. However, the coated concrete slightly improved the corrosion resistance. The corrosions of steel in all specimens were similar regardless of the defects on coated areas and the curing condition. The mixing type revealed better performance for steel corrosion prevention than those of the coating type. Before and after immersion into NaCl solution, needle-like crystal structures of both the mixing and coating type specimens were observed. Some needle-like crystal in concrete with CWPM showed a high sulfur peak was similar to ettringite crystals in control concrete.