VTT Technical Research Centre of Finland has developed a technique that can be used to convert lignin – a by-product of pulp mills and biorefineries – into a concrete plasticiser that is competitive against the synthetic and lignosulphonate-based admixtures currently on the market. In its water-soluble form, lignin can also be used as an additive in paints, printing inks, coatings and manufacture of gypsum products.
The workability of fresh concrete and the strength of the final product are important to builders. In fresh concrete, the lignin solution produced using VTT's LigniOx technique works noticeably better than commercial lignosulphonate-based plasticiser and even provides a promising alternative to synthetic superplasticisers. The LigniOx solution enables use of only a small amount of water, producing a highly workable paste that hardens into a strong final product.
VTT's LigniOx technology converts lignin water-soluble by means of oxygen oxidation. The technique can be used to process different kinds of lignins; only the process conditions must be tailored for each lignin type used. VTT's further development projects are focused on making the LigniOx solution competitive against synthetic products and exploring its commercial potential also in other application areas.
Although plasticisers account for less than one per cent of concrete paste, their global market is huge, approximately 17 million tonnes per year. Demand is also expected to increase in developing countries such as China, India, and Brazil. Plasticisers are currently produced from oil-based chemicals and lignosulphonates. Also lignosulphonates originate from the side-streams of pulping industry, but sulphite pulping and thus lignosulphonate production is declining.
Lignin – a substance that binds wood fibres – is a major by-product of the pulping industry and biorefineries, and is typically used as an energy source in the production site. VTT is seeking more valuable uses for this industrial by-product.