Interaction of cement and admixtures and its influence on rheological properties

Dispersing admixtures play an important role in today¿s concrete

technology. Around eight billion cubic metres of concrete are

made each year and most of it contains dispersing admixtures.

These chemical compounds, added at low dosages during concrete

mixing, make fresh concrete more liquid and improve its workability.

A precise way to determine the workability of concrete is to measure

its rheological values yield stress and plastic viscosity. From

ready mixed concrete plants and concrete element plants it is known

that rheological values of mortar and concrete can sometimes vary

when a new cement batch (i.e. a new production date) is used. The

aim of this study is threefold. Firstly, to measure and evaluate the

effect of variations during routine cement production on the rheology

of mortar and concrete. Secondly, to identify the constituents

in cement which lead to fl uctuations in rheology. Thirdly, to quantify

the changes in rheology due to variations in cement properties.

These questions are essential for cement and concrete producers

to guarantee a homogeneous concrete production, but also for the

scientifi c community to reach a deeper understanding of cementadmixture

interactions.