Abstract:

The adsorption mechanism of water reducer to clay is of great significance in effectively guiding the design of molecular structure of mud⁃inhibiting polycarboxylate superplasticizer（PCE）.Here，we prepared a series of low molecular weight anti⁃mud PCEs by visible light heterogeneous photocatalysis using Co/CeO₂ as catalyst，（NH₄）₂S₂O₈ as initiator，allyl polyoxyethylene ether（APEG-1000），2-acrylamido-2-methylpropanesulfonic acid（AMPS） and sodium vinyl sulfonate（VS） as monomers.The molecular chain contained functional groups such as carboxyl，amine，sulfonic acid，and polyethylene oxide chains，with a number⁃average molecular weight of approximately 1 400 and a weight⁃average molecular weight of approximately 3 800，and a relatively narrow molecular weight distribution.The most suitable synthesis process condition was obtained as follows.The ratio of APEG-1000、AMPS and VS was 1∶0.1∶0.1.The amount of（NH₄）₂S₂O₈ and Co/CeO₂ was 9% and 0.2%，respectively.The reaction temperature was 60 ℃.The reaction time was 4 h.The initial flow of the cement paste was 272 mm，while the flow was 260 mm after adding kaolin without loss in 60 minutes，demonstrating superior dispersion and antimud properties.The systematic characterizations revealed that the excellent antimud performance could be attributed to several factors.On the one hand，the strong interactions were conducived to anchoring adsorption of the PCE by cement and kaolin particles.On the other hand，the main diffraction peak（001） of kaolin was increased by 0.002 9 nm and the layer thickness was reduced by 4.64 nm when PCE was inserted into the interlayers of kaolin.Overall，this adsorption was beneficial to improve the mud resistance and retention of polycarboxylate superplasticizers.

Key words: photocatalytic, polycarboxylate superplasticizers, adsorption, kaolin