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Building the S7 express road in Poland, stretching 706km from Gdańsk to Rabka Zdrój, was a mammoth undertaking.

Division(s)
Europe Materials
Business Type(s)
Aggregates
Cement
Readymixed Concrete
Location
Poland
The challenge

The stretch of approximately 18 kilometres that runs through mountains was particularly challenging, requiring the construction of two 2.1km-long tunnels, the longest in Poland. A series of 22 bridges was also part of this massive five-year construction effort.

The environmental standards for working in this sensitive mountainous area were stringent, meaning great care and creativity were needed to comply with all regulations and minimise any short and long-term impacts.

As if these challenges weren’t enough, winter weather conditions in this part of Poland can be particularly harsh, with temperatures often reaching as low as -25oC. Ensuring the right materials – perfectly blended to deal with the conditions – and enough of them were in place to meet the demands of the project was essential for the main contractors, Astaldi and Salini Impregilo.

The solution

Three of CRH’s five operating companies in Poland – Bosta Beton (readymixed concrete), Trzuskawica (aggregates and lime) and Grupa Ożarów (cement) – combined their expertise to come up with unique and innovative solutions for the mountainous section of this complex project.

The contract for delivery of 500km3 of concrete was awarded to Bosta Beton. Together with the technologists in its sister companies, they came up with a bespoke recipe for a frost-proof readymixed concrete, resistant above 50 MPa and therefore ideal for extreme weather conditions, and a special sprayed concrete called “shotcrete”. Because of the technology chosen for the construction of the tunnel, shotcrete was a crucial part of the process. In the course of tunnel drilling, the walls and vaults were protected by a temporary casing of sprayed concrete. Then, after drilling consecutive 70-80m segments, a permanent casing of high-strength C50/60 concrete was formed by a special formwork.

The concrete used for the bridges of the project was based on a recipe combining – for the first time in Poland – the CEM I 42.5 Portland cement produced by Grupa Ożarów and crushed-stone aggregates from carbonate deposit (the first certification of this material for such application) specifically produced for this purpose by Trzuskawica.

The project also used some 10,000t of ‘Trzuskar’ HSD, a product launched by Trzuskawica in 2017. ‘Trzuskar’ is a mix of burnt lime and fly ashes used for soil stabilisation on construction sites; its composition perfectly fits the soil type in this area.