TY - JOUR
T1 - Effect of natural carbonation on the pore structure and elastic modulus of the alkali-activated fly ash and slag pastes
AU - Nedeljkovic, M.
AU - Savija, B.
AU - Zuo, Yibing
AU - Luković, Mladena
AU - Ye, Guang
PY - 2018/2/10
Y1 - 2018/2/10
N2 - The aim of this paper was to investigate the effect of natural carbonation on the pore structure, and elastic modulus (Em) of alkali-activated fly ash (FA) and ground granulated blast furnace slag (GBFS) pastes after one year of exposure in the natural laboratory conditions. The chemical changes due to carbonation were examined by X-ray diffraction (XRD), scanning electron microscope/energy-dispersive X-ray (SEM−EDX) and attenuated total reflectance Fourier transformed infrared spectroscopy (ATR-FTIR). Subsequently, the pore structure and Em of the degraded material were tested by mercury intrusion porosimetry (MIP), nitrogen (N2) adsorption, and nanoindentation. The chemical degradation of alkali-activated pastes due to natural carbonation is showed to be dependent on the GBFS content and their pore structure development. It was found that the pure alkali-activated GBFS paste was not carbonated at all within the tested period due to fine gel pore structure. On the other hand, carbonation of the gel in the pastes consisting FA and GBFS generated significant mineralogical and microstructural changes. The extensive decalcification of the gel was reflected in the increase of nanoporosity. Consequently, the Em of the carbonated pastes decreased. This study suggests that the degradation of alkali-activated FA and GBFS pastes due to carbonation may be accurately evaluated through micromechanical properties measurements rather than only by testing alkalinity of the pore solution and corrosion of reinforcement such as commonly studied carbonation effect in the ordinary Portland cement (OPC)-based materials.
AB - The aim of this paper was to investigate the effect of natural carbonation on the pore structure, and elastic modulus (Em) of alkali-activated fly ash (FA) and ground granulated blast furnace slag (GBFS) pastes after one year of exposure in the natural laboratory conditions. The chemical changes due to carbonation were examined by X-ray diffraction (XRD), scanning electron microscope/energy-dispersive X-ray (SEM−EDX) and attenuated total reflectance Fourier transformed infrared spectroscopy (ATR-FTIR). Subsequently, the pore structure and Em of the degraded material were tested by mercury intrusion porosimetry (MIP), nitrogen (N2) adsorption, and nanoindentation. The chemical degradation of alkali-activated pastes due to natural carbonation is showed to be dependent on the GBFS content and their pore structure development. It was found that the pure alkali-activated GBFS paste was not carbonated at all within the tested period due to fine gel pore structure. On the other hand, carbonation of the gel in the pastes consisting FA and GBFS generated significant mineralogical and microstructural changes. The extensive decalcification of the gel was reflected in the increase of nanoporosity. Consequently, the Em of the carbonated pastes decreased. This study suggests that the degradation of alkali-activated FA and GBFS pastes due to carbonation may be accurately evaluated through micromechanical properties measurements rather than only by testing alkalinity of the pore solution and corrosion of reinforcement such as commonly studied carbonation effect in the ordinary Portland cement (OPC)-based materials.
KW - Alkali-activated FA/GBFS
KW - E
KW - Nanoindentation
KW - Natural carbonation
KW - Pore structure
UR - http://www.scopus.com/inward/record.url?scp=85037532721&partnerID=8YFLogxK
UR - http://resolver.tudelft.nl/uuid:433d53e4-f151-4365-9b56-220c5fb9fdfe
U2 - 10.1016/j.conbuildmat.2017.12.005
DO - 10.1016/j.conbuildmat.2017.12.005
M3 - Article
AN - SCOPUS:85037532721
SN - 0950-0618
VL - 161
SP - 687
EP - 704
JO - Construction and Building Materials
JF - Construction and Building Materials
ER -