SigmaRoc has signed a joint venture agreement with major Calais based high-grade limestone and construction materials company, Carrières du Boulonnais (‘CB’), part of Groupe Carrières du Boulonnais (‘Groupe CB’), which has become a 25% shareholder in Granulats du Hainaut (‘GduH’), to expand GduH into a Benelux and Northern France wide supplier of limestone products.