Abstract: The invention relates to a mixture containing a building binder (preferably cement), comprising cellulose, ready for preparing water-based hardenable mixings intended to realise mainly soundproofing agglomerates suitable for laying or for producing manufactured articles or for fabricating structural building elements or for other engineering works. The invention further relates to a method for preparing said hardenable mixings. The invention further relates to a mainly soundproofing non structural agglomerate obtained from said mixture when a “light inert” is added and to a structural mainly soundproofing agglomerate obtained from said mixture when an “heavy inert” is added.