ABSTRACT
Abstract The aim of this paper is to study the effect of fly ashes with various chemical composition, particle sizes and replacement percentages on autogenous shrinkage of the pastes with fly ashes. It was found in the experiment that for the effect of chemical composition, tly ash with higher SO3 content resulted in lower autogenous shrinkage. For the effect of particle size, paste with fly ash having smaller average size than cement exhibited larger autogenous shrinkage whereas pastes with fly ashes having bigger average size than cement showed smaller autogenous shrinkage than that of the cement paste. For the effect of fly ash content, non-classified fly ash and classified fly ashes which have larger average size than cement showed the same tendency i.e. larger autogenous shrinkage in 20% fly ash paste than in 50% fly ash paste. On the other hand, smaller autogenous shrinkage in 20% fly ash paste than in 50% fly ash paste was found in case of pastes with classified fly ash having smaller average size than cement. It could be concluded based on the results of the study that not only chemical composition which affects rate of hardening and volume change of pastes with fly ashes but also particle size which affects the pore structure of the pastes, has to be considered for modeling autogenous shrinkage of paste with fly ash. Key words: autogenous shrinkage, fly ash, chemical composition, particle size
1. Introduction
The current development on some types of high performance concrete tends toward reducing water to binder ratio and increasing the paste content. Two obvious examples are high strength concrete and self-compacting concrete. As it is well known that the
autogenous shrinkage is a kind of shrinkage which is dominant in the pastes having low permeability, it is essential to clarify the mechanisms and factors which have effect on the autogenous shrinkage so that simulation of the shrinkage leading to the appropriate mix proportioning of concrete regarding the autogenous shrinkage can be derived.
