A concept for a polycarboxylate superplasticizer possessing enhanced clay tolerance

Conventional PCEs are known to easily incorporate into the layer structure of clay by means of their pendant PEO side chains, hence their dispersing ability in concrete is much impeded by clay impurities. Here, modified PCEs possessing hydroxy alkyl lateral chains were synthesized from methacrylic acid and hydroxy alkyl methacrylate esters (alkyl = ethyl, propyl and butyl), characterized and tested for their dispersion performance in cement in absence and presence of montmorillonite clay. The novel PCE type was found to disperse cement well, even when clay was present. Similar to polycondensate superplasticizers it is much less affected by clay than conventional PCEs. A mechanistic study including adsorption and XRD experiments revealed that the novel PCE only adsorbs on the surface of clay and does not incorporate into the layer structure of alumosilicates. This behavior explains its high tolerance against clay contamination.