Pool officer, Centre for Rural Development and Appropriate Technology, Indian Institute of Technology, Hauz Khas, New Delhi,
Executive consultant, Feeders India Consultants, New Delhi,
Two percent of the additive lignin superplasticizer (SLC) that is developed by mixing equal amounts of alkali carbonate and black liquor sulfate/sulfite lye (that is, lignosulfonate-based material) from paper and pulp works in India can eliminate the use of gypsum and produce a cement with improved strength, lower water requirements (about 30% less) for the same consistency, and increase durability. When used as a simple additive to normal portland cement (clinker and gypsum system), it increased strength and durability to aggressive reagents and decreased the water requirement for the same consistency. Porosity, microstructural, and morphological studies suggest that the lower porosity and increased strengths observed in the presence of the additive are caused by the formation of a Type III calcium silicate hydrate gel in the early stages of hydration, instead of a Type I or a Type II calcium silicate hydrate gel that is generally observed in the normal systems. The atomistic mechanism explains that the increased durability in concretes is caused by a denser, more uniform cement matrix and a stronger matrix-aggregate bond.
Paper ID: CCA10238J