Concrete Superplasticizers

What is a superplasticizer

       Developed in the 1960’s First used in Japan and Germany Introduced in the U.S. in the 1970’s Neutralizes the surface charges Causes dispersion Releases water in cement particles Reduces viscosity  Linear polymers containing sulfonic acid groups  Sulfonated melamine formaldehyde condensates  Sulfonated nephthalene formaldehyde condensates  Modified lignosulfonates  Polycarboxylate derivatives

Main Purpose

 Produce flowing concrete (7”-9” slump increase)  Easy placement (picture: concrete will fill all gaps between rebar)  High-strength (reaches up to 14,000 psi in 7 day break)

Important factors

 Type of plasticizer  Dosage  Time of addition of superplasticizer  Amount of cement

Benefits

 Reduce machine wear (concrete on picture will go from this 1” slump to 9” slump)  Better surface texture  Improve strength in less time  Reduce absorption  Eliminate fine cracks

Disadvantages

 High cost  Brief action (picture: restoration of the Queen Isabella Causeway after collapse in Sep. 15, 2001, time was very important)  Need strong, sealed forms