09-06-2012, 12:14 PM
Concrete Superplasticizers
concrete-superplasticizers.ppt (Size: 354.5 KB / Downloads: 3)
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
