TY - JOUR
T1 - Zeolite formation in alkali-activated cementitious systems
AU - Grutzeck, Michael
AU - Kwan, Stephen
AU - DiCola, Maria
N1 - Funding Information:
This material is based on work supported by the National Science Foundation under Grant No. 9988534.
PY - 2004/6
Y1 - 2004/6
N2 - Autoclaved aerated concrete (AAC) is a unique building material. Because of its cellular nature, it is lightweight, self-insulating, sound- and fireproof, as well as insect and mold resistant. Furthermore, AAC is free of VOCs and various fibers associated with wood and glass wool construction. In an attempt to toughen AAC and make it less prone to on-site damage, a conventional fly-ash-based AAC formulation is being supplemented with sodium hydroxide (NaOH). The introduction of sufficient alkali promotes the growth of crystalline zeolites in the tobermorite matrix during autoclave curing. It is postulated that in situ grown zeolites will serve the same purpose as added fibers. Inasmuch as fly-ash-based AAC reactions often do not go to completion, a phase study of the development of tobermorite and zeolites from a gel-like slurry made from reagent grade chemicals was undertaken. Mixtures were studied as a function of time and temperature. Phase development depends on bulk composition and curing conditions. Longer curing at higher temperatures causes the Na-P1 that forms initially to change to analcime. Whereas Na-P1 is bladelike in habit and is seen to intermingle with the slightly larger blades of tobermorite, the Na-P1 gradually undergoes a phase change to analcime that forms very large cubes. This change has the potential to disrupt the AAC matrix.
AB - Autoclaved aerated concrete (AAC) is a unique building material. Because of its cellular nature, it is lightweight, self-insulating, sound- and fireproof, as well as insect and mold resistant. Furthermore, AAC is free of VOCs and various fibers associated with wood and glass wool construction. In an attempt to toughen AAC and make it less prone to on-site damage, a conventional fly-ash-based AAC formulation is being supplemented with sodium hydroxide (NaOH). The introduction of sufficient alkali promotes the growth of crystalline zeolites in the tobermorite matrix during autoclave curing. It is postulated that in situ grown zeolites will serve the same purpose as added fibers. Inasmuch as fly-ash-based AAC reactions often do not go to completion, a phase study of the development of tobermorite and zeolites from a gel-like slurry made from reagent grade chemicals was undertaken. Mixtures were studied as a function of time and temperature. Phase development depends on bulk composition and curing conditions. Longer curing at higher temperatures causes the Na-P1 that forms initially to change to analcime. Whereas Na-P1 is bladelike in habit and is seen to intermingle with the slightly larger blades of tobermorite, the Na-P1 gradually undergoes a phase change to analcime that forms very large cubes. This change has the potential to disrupt the AAC matrix.
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U2 - 10.1016/j.cemconres.2003.11.003
DO - 10.1016/j.cemconres.2003.11.003
M3 - Article
AN - SCOPUS:2142821046
SN - 0008-8846
VL - 34
SP - 949
EP - 955
JO - Cement and Concrete Research
JF - Cement and Concrete Research
IS - 6
ER -