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“Without the additional seeds, the crystals first form on the surface of the cement grains, which are soon enveloped by a crystalline layer that delays the ex- change of water and of the molecules released from the clinker and so also slows down the further harde- ning process.”
Both these effects of the synthetic crystal seeds halve the time to formwork removal at 20° Celsius from about twelve to six hours, without any detectable differences in the final product.
This sounds simple in theory, admits BASF research scientist Dr. Luc Nicoleau who was centrally invol- ved in the developing of X-Seed®
: “But the greatest
challenge was to keep synthetic CSH crystals measu- ring only a few nanometers in a liquid suspension for prolonged periods without them fusing together and losing effectiveness.” The BASF experts finally suc- ceeded in performing this impressive feat of process technology thanks to their many years of experience with the dispersion of ultrafine materials.
When X-Seed® , which can simply be shoveled into
the concrete mixer along with the other ingredients, was finally launched on the market in 2009, its en- ormous use potential immediately became apparent. Besides the large market for precast concrete com- ponents, in which manufacturers can now produce more efficiently and rapidly and handle peak wor- kloads more flexibly, this innovative accelerator also offers advantages for a number of other applications. The product shortens the construction times of roads, tunnels and airstrips – also in winter outdoor tempe- ratures.
11-05 :: May/June 2011
Concrete is now omnipresent. Worldwide, some 1.4 billion metric tons of cement are used to produce this hard artificial stone. © BASF
The nanoproduct X-Seed®
not only saves costs, it also
has an extremely positive influence on the energy and climate balance and hence the sustainability of the material concrete.