C-S-H: A state-of-the-art concept to accelerate concrete hardening; Part I

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Economic and ecolo-
gical optimization: New options arise from concrete hardening accelerators like X-Seed

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The addition of synthetic C-S-H phases accelerates hydration by crystal growth also in the pore solution

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Progress of C-S-H phase formation with and without hardening accelerator. Reference: without accelerator after eleven hours ...

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Photo: BASF

... sample with X-SEED hardening accelerator after six hours

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SEM images of the cement paste recorded after 28 days show comparable structures with and without X-SEED hardening accelerator. Reference: without accelerator (left);

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Sample with X-SEED hardening accelerator (right)

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Photos (3): BASF

Development of concrete compressive strength (350kg of CEM I 52.5 R) at 10°C with and without hardening accelerator

Photos (3): BASF

Photo: BASF

In Germany, hardening accelerators have been largely neglected to date, particularly because a corrosive effect on the reinforcing steel could not be excluded. It appears appropriate, however, to revisit these agents as a result of the introduction of the Crystal Speed Hardening concept and the availability of suspensions based on nanoscale C-S-H phases.

Mixing the concrete, transporting it to the job site, pouring it into the formwork, flicking a switch, stripping the formwork – and that’s it: Generations of researchers and concrete technologists have dreamt of this scenario. The introduction of self-compacting concrete has made it a routine at least with respect to the “pouring into the mold” part without shaking and vibration. Yet, unfortunately, it is still not possible to just “flick the switch”. Concrete producers have to either wait until the concrete itself has reached a sufficient strength to be demolded or take appropriate measures...