Learn how UHPC behaves differently from traditional concrete, including workability windows, setting times, and cleanup considerations.
Ultra-high performance concrete behaves differently than traditional concrete because of its highly fluid, self-consolidating nature.
External vibration of the UHPC is not required and in fact should be avoided. Vibration can cause fiber segregation and water bleed, which will damage the mechanical properties developed by the UHPC.
The workability window for UHPC is set as the time until the minimum flow value of 7 inches is reached. This window will typically last 45 to 60 minutes after a batch is discharged. Initial set will occur between 2 and 6 hours, while final set will occur between 12 and 18 hours. These windows are all highly dependent on ambient weather conditions.
Clean up should begin as soon as practical to preserve equipment. Mixers and concrete buggies especially should be cleaned periodically to prevent buildup of hardened UHPC. Removal includes flooding with water and a moderate scrubbing action where needed.