CLOOS originally established in Maizières-lès-Metz by Félix CLOOS senior in 1902 and relocated to Esch-sur-Alzette in 1921. On the basis of its in-depth experience built up over the years, CLOOS is now Luxembourg’s No. 1 supplier of aggregates for use in road and civil construction. Certified by Ponts & Chaussées, the aggregates display a constant quality, in line with customer demands.

Since its establishment, CLOOS has focused on the exploitation and processing of blast furnace slag, a steelmaking by-product. Working under contracts from ARBED (now ArcelorMittal), CLOOS operates in a range of slag heaps in Luxembourg: since 1921 in Esch-sur-Alzette (the Terres Rouges slag heap), and in Dudelange from 1922 to 1945.

Atfter the Second World War, CLOOS started modernising its facilities in the face of high demand for aggregates for use in reconstructing the buildings and infrastructure destroyed in Luxembourg and the surrounding Greater Region.

Exploitation of the slag heap in Differdange started in 1955 and continued into the 1960s and 1970s, in parallel with the exploitation of the slag heaps of Terres Rouges, Belval and Dudelange.

The steel crisis of the 1970s and 1980s and the progressive closure of blast furnaces caused supplies of slag to dry up, forcing CLOOS to diversify its operations and sources of aggregates:

Quarrying: the sandstone quarry in Bridel, the dolomite quarry in Ralingen in Germany (Rabenborner Steingrube), the limestone quarry in Volmerange-les-Mines in France (Roche Blanche SA).
Crushing and screening of electric arc furnace (EAF) slag for the construction and civil engineering.
Establishment of sales platforms for aggregates from our various partners: Rhine alluvium and sand, Meuse grouine, Moselle gravel, quartzite aggregates, aggregates of quartz sandstone from the quarry in Cielle In Belgium, hard limestone, etc.
Development of aggregate packaging activities (big-bags, …).
Services for ArcelorMittal.
Recycling of materials from demolition sites.
Exploitation of inert waste landfills.