Olten Hammer District Connection, Concrete Roof Slab

Project

As part of the Olten Hammer District Connection project, a concrete roof slab supporting the Swiss Federal Railways (SBB) tracks was constructed using 34 m³ of Concretum^® Q-FLASH rapid-hardening concrete. The concrete works were carried out on Saturday around midday as part of a weekend construction operation. Railway operations were scheduled to resume as early as 11:00 a.m. on Monday. This tight construction window placed high demands on the concrete mix design, logistics and execution.

Challenge

The roof slab required a pumpable rapid-hardening concrete with a maximum aggregate size of 32 mm, combining sufficient working time with rapid strength development. On-site concrete production in seven conventional truck mixers required precise coordination between concrete mixing, pumping and placement. Rainy weather conditions and the limited time available before the scheduled resumption of railway operations on Monday added further challenges.

Solutions

In preparation for the project, Concretum conducted targeted trials in its in-house laboratory to optimise the concrete mix design for the specific project requirements. Particular attention was given to concrete consistency, pumpability with a maximum aggregate size of 32 mm and the required working time. Thanks to this thorough preparation, on-site production of the rapid-hardening concrete proceeded smoothly. A total of 34 m³ of concrete was mixed directly on site in seven truck mixers, pumped and placed.

A key factor in the project's success was the excellent collaboration between all parties involved: the team from Baustoffzentrum, the truck mixer drivers, the concrete pumping company A3, the construction team from Meier + Jäggi and Concretum's technical staff.

Despite the rainy conditions, the concrete works were successfully completed. This project demonstrates how targeted laboratory preparation, rapid-hardening concrete technology and well-coordinated teamwork enable demanding construction works to be carried out within tight construction windows.