Lignosulfonates in Concrete Admixture

Lignins are derived from abundant and renewable resources: trees, plants and agricultural crops. Lignins are nontoxic and extremely versatile in performance, qualities that have made them increasingly important in many industrial applications.Commercial lignin is currently produced as a co-product of the paper industry, separated from trees by a chemical pulping process. Lignonsulfonates (also called lignin sulfonates and sulfite lignins) are products of sulfite pulping. Kraft lignins (also called sulfite lignins) are obtained from the kraft pulping process.One of the largest applications for lignosulfonates is in the concrete admixture industry where they are used as dispersing agents to reduce the amount of water needed to form plastic and workable mixtures. Because of the lower water requirements, the resulting concrete is of increased density, better uniformity, higher compressive strength, and better durability. Lignosulfonates are also utilized as set retarding agents in applications where concrete needs to remain fluid over extended periods of time.The earliest patent concerning cement and lignin was issued to J. South, a "subject" of the King of England in 1904. Other patents in 1914, 1917, and 1919 discussed the benefits of waste sulfite pulping streams to cement slurries. A key patent issued to J. Mark of the Dewey and Almy Chemical Company (now a division of W.R. Grace Co.) discussed a water soluble lignin from the sulfite pulp process that provided increased strength and workability. In 1939, E. Scripture Jr. of the Master Builders Company was issued a patent claiming the advantage of the J. Mark patent plus significant reductions in the amount of water required. In 1948, and later years, employees of Master Builders Company were issued patents claiming superior performance from de-sugared (fermented) calcium lignosulfonates produced at Bellingham, Washington.The earliest sale of the product was recorded in 1948. In that first year 4,000 tons of liquid product were sold in the United States. Today approximately 100,000 tons of powder and 200,000 tons of liquid are consumed world wide for admixture usage.

Historically, lignin products have been primarily used in the low range commodity type admixtures. However, because of lignin's success in low range applications, companies around the world are researching ways to increase the usage of lignosulfonate products in the more technical, middle range and high range water reducing admixture products. The goal is not only performance, but reduction in costs by replacing more expensive petroleum based synthetic chemicals.