-terminated
polyethers are effective superplasticizers.
Superplasticizers are synthetic
polymers. Compounds used as superplasticizers include (1) sulfonated naphthalene formaldehyde condensate, sulfonated melamine formaldehyde condensate, acetone formaldehyde condensate and (2)
polycarboxylates
ethers.
Cross-linked
melamine- or
naphthalene-sulfonates, referred to as PMS (polymelamine sulfonate) and PNS (polynaphthalene sulfonate), respectively, are illustrative. They are prepared by
cross-linking of the sulfonated
monomers using formaldehyde or by sulfonating the corresponding crosslinked polymer. superplasticizer stabilizing a
colloidal suspension through steric interactions thanks to its lateral chains. Note: the PCE molecules are adsorbed onto positively-charged cement particles (
tricalcium aluminate () mineral phase). The polymers used as plasticizers exhibit
surfactant properties. They are often
ionomers bearing negatively charged groups (
sulfonates,
carboxylates, or
phosphonates...). They function as
dispersants to minimize particles segregation in fresh concrete (separation of the cement slurry and water from the coarse and fine aggregates such as
gravels and
sand respectively). The negatively charged polymer backbone
adsorbs onto the positively charged
colloidal particles of unreacted cement, especially onto the
tricalcium aluminate () mineral phase of cement. Melaminesulfonate (PMS) and naphthalenesulfonate (PNS) mainly act by
electrostatic interactions with cement particles favoring their electrostatic repulsion while polycarboxylate-ether (PCE) superplasticizers
sorb and coat large agglomerates of cement particles, and thanks to their lateral chains, sterically favor the dispersion of large cement agglomerates into smaller ones. However, as their working mechanisms are not fully understood, cement-superplasticizer incompatibilities can be observed in certain cases. ==Common superplasticizer types==