VBZ track concrete, Stauffacher Zurich

Situation

The tram tracks of VBZ (Zurich Transport Services) at Stauffacher, Zurich needed to be replaced. In order for the tram lines to resume their operations without hindrance on Monday morning, all work (track excavation, relaying the tracks, and concreting) had to be completed during a weekend closure. The required 300 m³ of track concrete had to be poured in a single shift on Sunday.

Solution and Evaluation

To ensure rapid setting, the special concrete Concretum® Q-FLASH 5/20 was used. Using two pumps, the Concretum rapid-hardening concrete was successfully poured on Sunday between 1:00 PM and 8:00 PM. The set open time of 130 minutes allowed for a more secure delivery from the Wollishofen concrete plant, and there was enough time to pump and vibrate the respective truck-mixed concrete, even with a fresh concrete temperature of 30°C at the construction site. The consistency was adjusted by the Concretum technicians so that the Q-FLASH 5/20 was easy to pump and provided adequate workability within the open time. Just 5 hours after mixing, the Q-FLASH 5/20 achieved a compressive strength of > 20 N/mm².