Comparative study of PCE superplasticizers with different anchoring groups in low water-to-binder ratio cementitious material

Abstract

Polycarboxylate ether (PCE) superplasticizers with three different anchoring groups were synthesized by copolymerizing allyl polyoxyethylene ether with trans-butadiene (FA), cis-butenedioic anhydride (MAH), and itaconic acid (IA), respectively. The interactions between PCEs and cementitious materials were revealed by adsorption properties, Ca2+ binding capacity of PCE, and zeta-potential of paste. The effects of anchoring groups in PCEs on the flowability and rheological properties of cementitious pastes were studied. Results indicated that the density and local configuration of –COO– groups in PCEs significantly affect their adsorption behavior and dispersibility in cementitious pastes. Most of the –COO– groups are isolated on the backbone of FA-PCE, while for the MAH-PCE, only pairs of –COO– groups present the backbone. All the –COO– groups directly connect to the main chains in FA- and MAH- PCEs, whereas half of the –COO– groups in IA-PCE indirectly connect to the main chains through hydrophobic methylene, which has a potential to curl and reduce its “accessible” –COO– groups. FA-PCE with a large specific charge density exhibit excellent flowability and rheological properties in cementitious pastes.