Guohao Fang

Self-immunity microcapsules for corrosion protection of steel bar in reinforced concrete.

A novel microcapsule-based self-immunity system for reinforced concrete is proposed. Its feasibility for hindering the corrosion of steel rebar by means of lifting the threshold value of [Cl−]/[OH−] is discussed. Precisely controlled release behavior enables corrosion protection in the case of depassivation. The release process is characterized over a designated range of pH values, and its release characteristics of the microcapsules, triggered by decreasing pH value, are captured by observing that the core crystals are released when exposed to a signal (stimulus). The aim of corrosion protection of steel bar is achieved through the constantly-stabilized passive film, and its stability is promoted using continuous calcium hydroxide released from the microcapsule, restoring alkaline conditions. The test results exhibited that the release process of the microcapsules is a function of time. Moreover, the release rate of core materials could interact with environmental pH value, in which the release rate is found to increase remarkably with decreasing pH value, but is inhibited by high pH levels.

Investigation of a Novel 3D Non-Destructive Evaluation for Corrosion Process in Reinforced Concrete

X-ray computed microtomography (X-ray mCT) method is proposed to trace the corrosion features of steel bar in cementitious materials (e.g., concrete). Three-dimensional corrosion morphology (including morphology of steel corrosion, corrosion products, and cracks formation) are characterized and reconstructed. Experimental results demonstrate that X-ray mCT can track time-dependent development of corrosion products and the subsequent initiation and propagation of corrosion-induced cracks. In addition, scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) are used to morphologically and chemically analyze the corrosion result. The microscopic analysis result is found to be in a very good agreement with the image analysis measured by X-ray mCT. Furthermore, the total corrosion ratio of steel, obtained by the X-ray mCT, is calculated to be in a good correlation with the data measured by Faraday’s law as well as gravimetric method.