New Sensors for Monitoring pH and Corrosion of Embedded Steel in Mortars during Sulfuric Acid Attack

Abstract

The sulfuric acid attack is a common form of degradation of reinforced concrete in contact with industrial wastewater, mine water, acid rain, or in sewage treatment stations. In this work, new pH-sensitive IrOx electrodes were developed for monitoring the pH inside mortar or concrete. To test their ability, the pH sensors were embedded in mortar samples at different depths and the samples were exposed to sulfuric acid solution. In another set of experiments, iron wires were placed at the same depths inside similar mortar samples and their corrosion was monitored as the acid attacked the mortar. Severe acid attack led to cement dissolution and formation of gypsum. The new pH sensors succeeded in measuring the pH changes inside the mortars. The pH gradient, from the high acid environment to the high alkaline mortar interior, occurred in a narrow region. Corrosion of the iron electrodes started only when the acidic solution was in their close vicinity.

Effect of Embedded Depth of Copper-Nickel-Plated Sensor Probes on Compressive Strength Development of Mortar

“…Accordingly, the authors mentioned that PEC sensors are particularly suitable for monitoring changes in the material properties of cement-based materials. Sampaio et al [25] developed an iridium oxide (IrO x )-based sensor sensitive to pH to present a method for manufacturing and characterizing embedded sensors for monitoring the pH concentration of steel embedded in mortar. In their study, they embedded the developed sensor in mortar specimens for verification and conducted monitoring after exposing them to a sulfuric acid solution.…”