Effect of surface preparation on corrosion of steel rebars coated with cement-polymer-composites (CPC) and embedded in concrete. (20th March 2020)

• Record Type: Journal Article
• Authors: Kamde, Deepak K.; Pillai, Radhakrishna G.
• Is Part Of: Construction & building materials. Volume 237(2020)
• Publication Date: 2020-03-20
• Subjects: %bwob % by weight of binder -- AR As-received -- C (x t), Chloride concentration at depth 'x' after exposure for 't' seconds -- CDF Cumulative distribution function -- Cmax Maximum chloride concentration at the exposed concrete surface -- CPC Cement-Polymer-Composite -- Cs Surface chloride concentration -- Clth Critical chloride threshold of steel-concrete interface -- Dcl Diffusion coefficient of concrete -- erf Error function -- m Decay constant -- RC Reinforced Concrete -- SB Sand-blasted -- SC Steel-Cementitious -- t Exposure time -- ti Time to corrosion initiation -- wC With coating -- woC Without coating -- x Depth from the exposed surface of concrete; Reinforced concrete -- Surface preparation -- Chloride threshold -- Cement polymer composite coating -- Time to corrosion initiation; Building materials -- Periodicals; 624.18
• DOI: 10.1016/j.conbuildmat.2019.117616
• Languages: English
• ISSNs: 0950-0618

Abstract

Highlights: First paper on performance of CPC coated steel rebars considering the possible quality issues at construction sites. Paper covers from microstructure aspects of corrosion to the service life of a bridge structure. Possible corrosion mechanism for inadequately applied CPC coated steel is proposed. When CPC coatings are used, sandblasting of steel rebar can enhance the service life by twice. Abstract: Nowadays, Cement-Polymer-Composites are widely used to coat steel rebars to delay the initiation of corrosion in reinforced concrete (RC) structures. However, Cement-Polymer-Composite (CPC) coating is sometimes inadequately applied on rusted steel and can lead to premature under film/crevice corrosion. This paper investigates the effect of such inadequate applications of CPC coating and premature corrosion on the service life of RC structures. For this, maximum surface chloride concentrations, diffusion coefficients, and chloride thresholds were determined by a one-year-long laboratory study on the specimens obtained from a 6-year-old bridge and prepared in the laboratory. Studies found that the chloride threshold of inadequately coated steel rebar (i.e., coating on 'as received' surface) is significantly lower than that of the adequately coated steel rebars (i.e., coating on 'sandblasted' surface). Also, the corrosion initiation time for systems with inadequately coated steel rebar was about 50% less than that of the systems with adequately coated steel rebars. The corrosion mechanisms were justified with micrographs. It is recommended not to use CPC coated steel rebars if adequate surface preparation (say, cleaning/sandblasting) is not implemented.