Cement dispersion performance of superplasticisers in the presence of clay and interaction between superplasticisers and clay

Abstract

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

Influence of experimental procedure on d-spacing measurement by XRD of montmorillonite clay pastes containing PCE-based superplasticizer

“…From an initial d-spacing of 12.3-12.6 Å or 15.0-15.5 Å (depending on the degree of clay hydration) when no admixture is present [2,3], PCE intercalation produces a d-spacing expansion of up to 17-18 Å when a PCE-based superplasticizer is used. This enlargement has been reported to correspond to one single intercalated poly-glycol chain in MNT clay, coordinated with water molecules [4][5][6][7][8]. All available studies in the literature address the interaction of clays with PCE-based superplasticizers via the same experimental procedure [1,4,8].…”

Modelización del mecanismo de pérdida de consistencia provocado por arcillas en pastas de cemento con superplastificantes base policarboxilato

“…provocado por arcillas en pastas de cemento con superplastificantes base policarboxilato P. Borralleras (1) , I. Segura (2) y A. Aguado (3) (1) …”

“…Las arcillas MNT fundamentan su efecto interferente a partir de dos procesos diferentes que se manifiestan de forma paralela [2]. Por un lado, absorben parte del agua de amasado y, simultáneamente, inhiben el efecto dispersante de los polímeros de PCE.…”

Study on the Impact of Na/Ca Bentonites on the Dispersion Performance of Conventional and Modified Phosphate Polycarboxylate Superplasticizers in Cement Mortar

“…On the one hand, since MMT is a kind of clay with strong water absorption and swell ability, water molecules can be adsorbed on its surface and between the layers . Water molecules penetrate the interlay region and hydrate exchangeable cations, leading to water adsorption. , On the other hand, MMT has strong ion exchange ability. Under alkaline conditions in the hydration process of cement paste, SiO 2 and Al 2 O 3 react with Ca 2+ to form water-insoluble crystals, which increase the viscosity and reduce the fluidity of the paste …”