11-05 :: May/June 2011

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Background: Nanoscale crystal seeds also make concrete harden faster at normal

outside temperatures (magnification 960:1 at 12cm image width). © BASF

mass and thereby promote faster growth. When the concrete hardens, further molecules from the cement can attach themselves to these CSH seeds. The resul- ting crystals grow more densely and finally interlock to form the compact cement stone.

The mechanism of action of the hardening accelera- tor is explained by Professor Horst-Michael Ludwig of the Bauhaus University in Weimar: “As well as the temperature the availability of these crystallization seeds determines the rate of crystal formation and

thus the hardening process. Normally, the CSH seeds first have to form spontaneously from several mole- cules released from the cement which accidentally come into contact with each other. X-Seed®

voids

this first barrier to crystallization by providing an excess of these tiny crystal seeds.”

Another factor is that the CSH crystals form in a more homogeneously distributed manner, adds the expert for construction materials who early turned his atten- tion to this subject.