A comparative study on corrosion behavior of rebar in concrete with fatty acid additive as phase change material

The aim of this study is to evaluate thermal and corrosion behavior of concrete with fatty acid (FA) mixture as phase change material (PCM) used for energy saving in buildings. We compared direct use of fatty acid mixture (capric acid and myristic acid) and its microencapsulated form in concrete. The work is based on thermal analyses (DSC, TGA, thermal buffering and thermal regulation effect), and also corrosive behavior of PCM on reinforcement steel (rebar) by using electrochemical impedance spectroscopy. Temperature development of fresh concrete in the first 40 h shows that PCM additives do not affect the hydration reaction, but peak temperature was lowered due to the absorption of heat by PCM. This also indicates retarding effect of PCM in concrete. Additionally, exposed metal surfaces and concrete samples in contact with rebar were examined with SEM for determination of corrosion products. Concrete samples showed enhanced thermal behavior and buffering effect to temperature fluctuations. Compressive strength was decreased by up to 38% with the addition of PCM into concrete. The polarization resistance determined from EIS results does not change significantly addition of PCM in concrete. Thus, PCM has no corrosive effect on metal surfaces in concrete.