A study of superplasticisers (SPs), including polyethylene oxide-free type polycarboxylate superplasticisers (PCEs), a conventional PCE and a polycondensate, was carried out to research their cement dispersion behaviour and interactional behaviour with clay. It was found that the cement dispersion performance of SPs in the presence of clay is dependent on both the cement dispersing capability and clay sensitivity. The sensitivity of superplasticisers to the presence of clay was investigated systematically through a study of water and SP adsorption (surface and interlayer) on the clay. It was found that clay sensitivity is dependent on the clay adsorption of both water and the SP. The behaviours of cations (surface and interlayer) of clay interacting with different SPs were also investigated and the interactional mechanism between SPs and clay was clarified. This work will aid further understanding of the effects of clay in concrete and help in the design of SPs with enhanced clay tolerance. NotationL 0 cement paste spread (cm) at water/cement (w/c) ratio of 0·49 without superplasticiser (SP) and clay L 1 cement paste spread (cm) with a certain dosage of SP and no clay at a w/c of ratio 0·49 L 2 cement paste spread (cm) with a certain dosage of SP and clay at a w/c of ratio 0·49 m 1 weight (g) of SP m 2 weight (g) of drying clay V volume (ml) of methylene blue solution consumed