Abstract
The paper discusses the role of entrained air voids on the transformation from liquid to solid of cement based materials (paste, mortar, concrete). The discussion is based on pore water pressure and volume change measurements. Air pores seem to contribute to increased rate of autogenous shrinkage in the time before the “knee-point” (i.e. in the few hours before autogenous shrinkage rate becomes significantly lower than the chemical shrinkage rate), and an earlier appearance of the knee-point. Through setting and shortly after, air pores alter the pore water pressure evolution in that they act as a buffer, and thereby reduce the pressure decrease and the subsequent autogenous shrinkage, as well as friction against panels in slipforming. The influence on plastic shrinkage does not seem to be significant.
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Hammer, T.A., Fosså, K.T. Influence of entrained air voids on pore water pressure and volume change of concrete before and during setting. Mater Struct 39, 801–808 (2006). https://doi.org/10.1617/s11527-006-9085-0
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DOI: https://doi.org/10.1617/s11527-006-9085-0