COUNTERACTING PLASTICISER RETARDATION OF CEMENT SETTING WITH CALCIUM NITRATE
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Published:2002
H Justnes, B G Petersen, 2002. "COUNTERACTING PLASTICISER RETARDATION OF CEMENT SETTING WITH CALCIUM NITRATE", Innovations and Developments In Concrete Materials And Construction: Proceedings of the International Conference held at the University of Dundee, Scotland, UK on 9–11 September 2002, Ravindra K. Dhir, Peter C. Hewlett, Laszlo J. Csetenyi
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High dosages of lignosulfonates for super-plasticizing of concrete are prohibited by simultaneous setting retardation. The retardation can be counteracted with calcium nitrate without destroying the viscosity. This enables design of cost-effective admixture blends as alternative to super-plasticizers, since both lignosulfonates and calcium nitrate are relatively cheap and abundant industrial chemicals.
The viscosity of lignosulphonate – calcium nitrate blends is comparable to naphthalene or melamine based super-plasticizers, but these still retard somewhat less than the blends. Calcium nitrate is more efficient in counteracting retardation by lignosulfonates than calcium chloride.
Calcium nitrate can also counteract strong retarders like non-refined, sugar containing lignosulfonate. This effect may be utilised for safe transport of over-retarded ready mixed concrete, followed by activation with calcium nitrate when the truck approaches the construction site.
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