Renovation of the Bürgertobel Viaduct, Thalwil

Initial situation

An existing SBB railway bridge had to undergo general renovation measures. In order to keep the closure period as short as possible, a concept was conceived that allowed the subsequent work to be performed rapidly. The concreted surface had to harden and dry as rapidly as possible so that the subsequent work steps could be completed on schedule and rail traffic could quickly return to its normal timetable. One track would be closed for renovation work, while the other remained open.

Solution and assessment

A system was selected for the renovation of the bridge, in which precast concrete elements were used. In order to guarantee a bond between the precast elements, the rapid-hardening concrete Concretum^® Q-FLASH 2/20 was used. This was pumped and achieved an open time of up to two hours.
Just two hours after the start of hardening, a strength of 20 N/mm² was achieved and residual moisture of below 4 CM-% was reached, irrespective of the weather conditions. As a result, the closure periods specified by SBB were complied with. The concrete was produced on site in a mixer truck under the guidance of Concretum employees. The fresh concrete consistency could be adjusted for purpose so that the pouring with pumps could be performed smoothly.