Fast-curing compound for casting efficiencies Feb 2011
BASF News Release
- Crystal Speed Hardening™ (CSH), a new admixture technology developed by construction chemical giant BASF, is set to revolutionize concrete casting. Shorter curing times achieved by using the new admixture will change the planning and processes for both cast in-situ concrete and precast concrete segmental linings. It will allow the efficiencies of earlier striking times of formwork and contribute to key sustainability issues of reducing energy demand, minimising carbon dioxide emissions, ensuring material optimization and maintaining high quality specifications.
Accelerated growth of calcium silicate hydrate crystals provides the key advantage of using the CSH concept
- The CSH concept uses a new hardening accelerator called X-SEED® to boost early strength development by modifying the action mechanism of cement hydration. X-SEED is made of suspended CSH-seeding crystals: the material added is of the same nature as the final hydration products from the cement reaction with water. Since the suspended crystals are considerably smaller than microsilicas, the surface is much more beneficial for accelerating the crystal growth during the early stages of concrete hardening.
- The cost implications of using X-SEED vary widely by application, as does the generated added value. The elimination of heat curing, the optimization of the mix design for lower CO2 emissions, and the acceleration of the production process however, bring considerable and attractive benefits.
- "Although primarily developed for improving precast production efficiency, the CSH concept, of which X-SEED is a key component, also offers distinct advantages in cast in-situ operations," said Michael Kompatscher of BASF. X-SEED used in the in-situ concrete lined tunnels on the high-speed railway between Madrid, Bilbao and Donosti in Spain, demonstrated a 20% increase in productivity as well as better workability.
Faster curing admixture for in-situ and precast concrete
- In segment casting factories, mix designs containing X-SEED can optimize production capacity and revises substantially required investments in heat curing facilities.
- "The abbreviation CSH also refers to calcium silicate hydrates; the cement hydration products responsible for the compressive strength of concrete," explained Kompatscher. "Hydration speed depends on the chemical composition of flyash and other cementitious materials. X-SEED admixture, which is a liquid suspension of synthetic crystal seeds on the nano scale, significantly accelerates the growth of calcium silicate hydrate crystals to effectively boost the hydration process of early-age (6-12hr old) concrete and within a wide range of temperatures.
- The CSH crystals grow quickly between cement grains and promote improved properties in the final microstructure through natural hardening and without the typical drawbacks on durability of common acceleration methods."
- The concept is also compatible with other BASF admixture technologies including the Zero Energy System and Smart Dynamic Concrete.
- BASF contribution to Switzerland's mega Gotthard Baseline undertaking - TunnelTalk, October 2010
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