The influence of mineral admixtures on the distribution of shrinkage in high performance concrete

High performance concrete may contain different mineral admixtures which cause differential shrinkage characteristics. In order to study the phenomenon, several pairs of fixed displacement sensors at various depths from the exposed surface were used to measure shrinkage strain in concrete samples. Only one surface of each concrete specimen was exposed to dry conditions during the experiment. Relative humidity in the concrete at various depths was also studied using embedded humidity sensors. The results showed that the surface of the concrete had less relative humidity and more shrinkage than the interior of the concrete. And concrete at a depth of 100 mm from the drying surface had shrinkage of 15% to 33% less than concrete at a depth of 10 mm. Such shrinkage differences relative to distance from the drying surface were decreased significantly by the addition of silica fume. On the other hand, shrinkage increased with the addition of fly ash or granulated blast furnace slag powder. There was a good linear relationship between shrinkage and relative humidity at different depths from the exposed surface for every type of concrete.