Effect of Chloride on Accelerated Corrosion of Steel Rebar in Alkali-Activated Fly Ash and Paper Sludge Ash–Reinforced Concrete

The aim of this work was to investigate the corrosion of reinforcing rebar inserted in geopolymer concrete (GPC) made from fly ash (FA) containing 10% paper sludge ash (PSA) by weight under three curing conditions, namely oven curing (OC) at 60  C, external exposure curing(EEC), and curing at ambient temperature (AC). The investigation was carried out on the GPC using linear polarization resistance and Tafel plot techniques. All of the reinforced lollipop specimens were stored in a 3.5% NaCl solution with a steady anodic electrical potential of about 12 V applied to accelerate the corrosion process. Both the bond strength loss percentage and the mass loss percentage of the corroded steel rebar embedded in the concrete cylinder specimens were calculated. The test results showed that the OC condition demonstrated best corrosion resistance in the FA-GPC specimen compared to the FA-PSA GPC specimen. The test results for FA-PSA GPC specimens showed that their corrosion resistance performance was better under AC condition compared to the other two curing conditions.