TY - JOUR
T1 - Alkalinity and its consequences for the performance of steel-reinforced geopolymer materials
AU - Koenig, Andreas
AU - Mahmoud, Hitham
AU - Baehre, Oliver
AU - Dehn, Frank
PY - 2020/5/1
Y1 - 2020/5/1
N2 - This paper investigates the development of the alkalinity and its impact on carbon steel reinforcement embedded in alkali-activated fly ashes (AAFA) and alkali-activated fly ashes with ten percentage mass (wt%) of blast furnace slag (AAFAS)-based materials (geopolymer–GP). The pH analysis of eluates indicates a remarkable decrease of alkalinity in AAFA and AAFAS in the first hours of the geopolymerization process. Phenolphthalein solution and pore solution tests on concretes also show a sharp decrease of alkalinity with increased Ca content in the binder due to carbonation. Micro X-ray computer tomography (µXCT) and electrochemical techniques indicate that the changed pH in the GP systems was accompanied by a decrease in the corrosion rates of steel reinforcement when compared to ordinary Portland cement (OPC) systems. In contrast to calcite and vaterite, which were detected in OPC and AAFAS after a carbonation process, only sodium carbonate natron was determined at lower levels in AAFA by X-ray diffraction (XRD).
AB - This paper investigates the development of the alkalinity and its impact on carbon steel reinforcement embedded in alkali-activated fly ashes (AAFA) and alkali-activated fly ashes with ten percentage mass (wt%) of blast furnace slag (AAFAS)-based materials (geopolymer–GP). The pH analysis of eluates indicates a remarkable decrease of alkalinity in AAFA and AAFAS in the first hours of the geopolymerization process. Phenolphthalein solution and pore solution tests on concretes also show a sharp decrease of alkalinity with increased Ca content in the binder due to carbonation. Micro X-ray computer tomography (µXCT) and electrochemical techniques indicate that the changed pH in the GP systems was accompanied by a decrease in the corrosion rates of steel reinforcement when compared to ordinary Portland cement (OPC) systems. In contrast to calcite and vaterite, which were detected in OPC and AAFAS after a carbonation process, only sodium carbonate natron was determined at lower levels in AAFA by X-ray diffraction (XRD).
KW - Alkalinity
KW - Geopolymer concrete
KW - Micro X-ray computer tomography (µXCT)
KW - Steel reinforcement corrosion
UR - http://www.scopus.com/inward/record.url?scp=85085158267&partnerID=8YFLogxK
U2 - 10.3390/molecules25102359
DO - 10.3390/molecules25102359
M3 - Article
C2 - 32438581
AN - SCOPUS:85085158267
VL - 25
JO - Molecules: a journal of synthetic organic and natural product chemistry
JF - Molecules: a journal of synthetic organic and natural product chemistry
SN - 1420-3049
IS - 10
M1 - 2359
ER -