Renewal of Drainage and Sewer Infrastructure beneath the Railway Line Bachtelstrasse, Winterthur

Existing drainage and sewer structures beneath a heavily trafficked SBB railway line at Bachtelstrasse in Winterthur Switzerland were replaced as part of a major infrastructure renewal project. Some of the existing structures dated back to the 1930s and had reached the end of their service life. In addition, new requirements regarding flood protection and infrastructure resilience necessitated a comprehensive upgrade of the drainage system. All construction activities had to be completed within a tightly scheduled railway possession window.

Challenge

All construction operations had to be executed within a matter of hours, including demolition of the existing structures, excavation, installation of new precast elements, backfilling and reinstatement works. For the concrete works, the challenge was to achieve a balance between sufficient workability and rapid strength development. While the concrete had to remain workable during placement, the structural elements were required to attain high early-age strengths within a very short period of time. Furthermore, complex geometries and difficult access conditions placed particularly high demands on the placing characteristics of the concrete.

Solution

A total of 94 m³ of Concretum^® Q-FLASH 2/20 rapid-hardening concrete was supplied and placed for the project. Initially, 23 m³ of pumpable rapid-hardening concrete was used for the construction of the base slab. Thanks to a project-specific mix design, the required early strength was achieved within a short time, allowing the precast elements to be installed as scheduled. Subsequently, 26 m³ of self-compacting rapid-hardening concrete was used for the grouting and bedding of the precast elements. Owing to its excellent flowability, the concrete was able to completely fill the confined and difficult-to-access areas beneath the precast units without voids and without the need for mechanical vibration. Once the required strength had been achieved, the side backfill and the infill around the precast structures were completed using a further 45 m³ of pumpable Concretum^® Q-FLASH 2/20 rapid-hardening concrete.

The Q-FLASH concrete systems were specifically tailored to the project's requirements and provided an optimal combination of workability retention, reliable pumpability, excellent flow characteristics and rapid strength development.

Result

All concrete works were completed on schedule and in accordance with the demanding construction programme. Throughout the project, both the consistency and the quality of the supplied concrete remained excellent. The rapid strength development of Concretum^® Q-FLASH 2/20 enabled the works to be successfully completed within the available railway possession window.

The project demonstrates how modern rapid-hardening concrete technologies enable the successful delivery of complex infrastructure projects under extremely demanding time constraints while meeting the highest standards of quality, construction reliability and long-term durability.