Corrosion mechanisms of steel reinforcement in fly ash/slag based powder form of geopolymer concrete

University of Technology Sydney. Faculty of Engineering and Information Technology.To promote the use of geopolymer materials in structure applications, this study aimed to investigate on carbonation and chloride resistance of one-part fly ash/slag geopolymer concretes. Additionally, the possibility of using a sodium-based set retarder to address the issue of short setting time was included in the investigation. The key findings indicated that using the set retarder, with an amount of 2-6%, prolonged the setting time of one-part geopolymer binders and reduced the heat released by activation reactions. The results obtained also showed that carbonation alone might not lead to steel corrosion in one-part geopolymer concrete investigated because the pH in carbonated parts was always higher than 10. For assessing chloride resistance in an accelerated test in 16.5% NaCl solution, 40% fly ash/ 60% slag geopolymer concrete had a lower chloride resistance than OPC concretes, while chloride resistance of 60% fly ash/ 40% slag geopolymer concrete was worse. Due to the presence of both fly ash and slag in the precursor, chloride ions were physically and chemically bound in the one-part geopolymer concretes. Regarding RCPT, using 60 voltage, advocated in ASTM C1202, caused the issue of overheating, thus, RCPT performed at 30 voltage was highly suggested