Holcim and Lafarge which are currently no. 1 and no. 2 on the cement market had some discussions about a possible merger. The new company will probably have $40 billion in sales and will be able to get a lot of cost cutting opportunities in energy cost, production with no overcapacity, etc. Lafarge previously purchased Orascom in 2008 and Holcim also did an acquisition of Aggregate Industries in 2005. But, both these deals were done before the financial crisis.
Regarding regulatory authorities, nobody knows what might happen. Most probably they will encounter some problem in France, Span and Germany as it is highly probable that the authorities will also impose a asset sale of some factories.
Both companies have a total of 136000 employees (Lafarge = 65000 and Holcim = 71000).