Lignosulfonates (often abbreviated as LS) is byproducts from the production of wood pulp using sulfite pulping,is one of the first dispersants added as an admixture to concrete.
Lignosulfonates are recovered from the spent pulping liquids (red or brown liquor) from sulfite pulping. Ultrafiltration can also be used to separate lignosulfonates from the spent pulping liquid. A list of CAS numbers for the various metal salts of lignosulfonate is available.
Lignosulfonates have been used since the 1930s as plasticizers or water reducers. Mixed with concrete, their use has afforded the beneficial effects of retarding the setting time and reducing the amount of mixing water required.
Furthermore, greater workability of plastic concrete during its placement in formworks and increased air entrainment have resulted from their use. As by-product of the pulping industry, lignosulfonates are of low price and despite their limited performance they find a large field of applications for improving the quality of concrete.