Properties of Fresh Concrete


Properties of Fresh Concrete

The last RILEM Seminar on the Technology of Fresh Concrete took place in 1973 in Leeds. The main  interest of this seminar was focused on workability, measuring techniques and the use of additives.  In the meantime nearly two decades have passed. During this period, considerable changes have taken  place in concrete production. In many countries concrete production has been shifted from the site to the  
plant almost completely. This development presents new questions for technology, especially how to  
achieve an exactly defined consistency at the moment 
of delivery on site, from plant to builde . This 
problem turned out to be a difficult one, since consistency changes take place during the period between  
mixing and delivery, not only depending on the duration of transport, but also on othr parameters, for  
example temperature.

This paper reviews the progress made in our understanding of the rheology of cement paste since 1973 and
describes the general features of the rheology and methods of measurement. Cement paste has a yield value 
and shows irreversible structural breakdown during handling and testing as a result of the shear imposed on 
the sample. This accounts for the discrepancies between the numerical values reported in different papers
and also for the range of different rheological models to which experimental data have been fitted. Slippage 
and plug flow are also problems which have been investigated and can be taken into account when planning 
experiments.Keywords: Cement Paste, Rheology, Measurement Methods, Slippage, Plug Flow, Mixing.

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