TY - JOUR
T1 - Hydration and strength development of binder based on high-calcium oil shale fly ash
T2 - Part II. Influence of curing conditions on long-term stability
AU - Freidin, C.
N1 - Funding Information:
The author would like to express his appreciation for the research grant from the Jacob Blaustein Institute for Desert Research, Ben-Gurion University of the Negev (Israel) to carry out the reported work, which forms part of the major research program on the development of technology of cementless building materials on the basis of fly ashes.
PY - 1999/1/1
Y1 - 1999/1/1
N2 - The distinguishing feature of high-calcium oil shale fly ash (HCOSFA) used in experiments is the high amount of free CaO and SO3 in form of lime and anhydrite. Strength development as well as the microstructure and composition of the new formations of fly ash binder (FAB) based on HCOSFA and low-calcium coal fly ash after curing in different conditions and long-term exposure in various environments were studied. It was determined that moist air and water are the most favorable conditions for aging processes of FAB. In atmospheric air three stages in strength change of cured FAB are observed: increase of compressive strength over 1 month; sharp drop after 1 month up to the 3 to months; stabilization or slowdown of loss in strength after 3 to 6 months of exposure. The duration of the second and third stages depends on HCOSFA content and does not depend on curing conditions. One of the hydration products of FAB is ettringite. Its instability in air could be a reason for the decrease in strength of FAB and some disintegration of the hardened system. In the presence of low-calcium coal fly ash, additional amounts of stable calcium silicate hydrates are formed during FAB curing especially during steam curing. This has a positive effect on compressive strength and stability of FAB in atmospheric air.
AB - The distinguishing feature of high-calcium oil shale fly ash (HCOSFA) used in experiments is the high amount of free CaO and SO3 in form of lime and anhydrite. Strength development as well as the microstructure and composition of the new formations of fly ash binder (FAB) based on HCOSFA and low-calcium coal fly ash after curing in different conditions and long-term exposure in various environments were studied. It was determined that moist air and water are the most favorable conditions for aging processes of FAB. In atmospheric air three stages in strength change of cured FAB are observed: increase of compressive strength over 1 month; sharp drop after 1 month up to the 3 to months; stabilization or slowdown of loss in strength after 3 to 6 months of exposure. The duration of the second and third stages depends on HCOSFA content and does not depend on curing conditions. One of the hydration products of FAB is ettringite. Its instability in air could be a reason for the decrease in strength of FAB and some disintegration of the hardened system. In the presence of low-calcium coal fly ash, additional amounts of stable calcium silicate hydrates are formed during FAB curing especially during steam curing. This has a positive effect on compressive strength and stability of FAB in atmospheric air.
UR - http://www.scopus.com/inward/record.url?scp=0033328820&partnerID=8YFLogxK
U2 - 10.1016/S0008-8846(99)00139-8
DO - 10.1016/S0008-8846(99)00139-8
M3 - Article
AN - SCOPUS:0033328820
SN - 0008-8846
VL - 29
SP - 1713
EP - 1719
JO - Cement and Concrete Research
JF - Cement and Concrete Research
IS - 11
ER -