Synthesis and Properties of a Starch-based Clay Tolerance Sacrificial Agent

For improving the workability of clay-containing cement paste superplasticized by polycarboxylate ether (PCE), a new starch-based sacrificial agent is synthesized in the following two steps: first, the starch is sulfonated to obtain sulfonated starch (SS) with a strong steric effect, which is verified through its dispersion performance; then, SS is quaternized to obtain starch-based sacrificial agent (SSB). The structure of SSB is characterized by FT-IR and element analysis. Montmorillonite (MMT), as the most detrimental clay, strongly perturbs the dispersing power of conventional PCE. Therefore, the MMT-tolerance property of SSB is tested. With the addition of 0.02 wt.% SSB, the fluidity of MMT-containing cement paste is increased from 191.5  to 222 mm and the rheological property of MMT-containing cement paste is improved by reducing the yield stress and the flow index ( τ 0 and n in Herschel-Bulkley model). Adsorption experiments, DLS, and XRD are used for explaining SSB's clay-tolerance mechanism. Adsorption experiments show that the cationic group enhanced the interaction between MMT and SSB; DLS and XRD demonstrated that SSB is adsorbed on MMT through electrostatic attraction and could hinder the interaction between PCE and MMT by its high steric effect.