Polycarboxylate ether (PCE)-based dispersant is the most widely used polymeric chemical admixtures to improve the early age properties (e.g. workability) and mature state properties (e.g. compressive strength) of high performance concretes. The polymer is known to interact with both cement particles that are undergoing hydration and also with hydrated cement compounds that are generated during hydration. While the mechanism and dynamics of the former interaction process are well established, very little is known about the latter. Interestingly, the dynamics of polymer interactions with hydrated cement phases present untapped opportunities to engineer sustainable construction materials through a controlled admixture release process. The controlled admixture release process involves the incorporation of polymer admixtures in a phases such as the Ca-Al-layered double hydroxides (LDH), such that when the composite is intermixed in concrete, it creates a modulated admixture availability, and hence a smartly controlled workability and slump retention at early age of the concrete â which is vital for special construction application, e.g., deep oil-well cementing. However, lack of adequate understanding of the dynamics of the interaction of the polymer with Ca-Al-LDH and the behavior of the composite in cement pore fluid, have limited the applications of Ca-Al-LDH for smart admixture release in concrete technology.
This work examines the intercalation of different polycarboxylate ether (PCE)-based dispersant structures in Ca-Al-LDH, and the kinetics and thermodynamics of the de-intercalation in simulated pore fluid of various cement types (e.g., Portland cement, and calcium aluminate cement). Emphasis is placed on elucidating the effects of the polymer structure â size, chain length, functionality (e.g., SO42-, NO3-, OH-, and PO43- groups), and tacticity â ; the effects of the cationic ratio and charge density of the host LDH; and the effect of the pore fluid chemistry (i.e., composition and pH), and the curing condition (e.g., temperature). The expected results will provide insights on a means to control admixture release in cementitious systems.
Keywords: Layered Double Hydroxide; Controlled Polymer Release; Cement and Concrete.