Effect of sodium gluconate on polynaphthalene sulfonate adsorption

The influence of sodium gluconate (SG) on the adsorption of polynaphthalene sulfonate (PNS) superplasticiser on the surface of particles was investigated using cement and fly ash pastes. Below the saturated PNS dosage, SG reduces the fluidity loss of the two pastes and the amount of PNS adsorbed on the particle surface. The similarity of this behaviour for the two pastes indicates that inhibition of cement hydration is not the sole reason for SG reduction of fluidity loss of cement paste with PNS. X-ray photoelectron spectroscopy data show competing adsorption forces between SG and polar groups of PNS on the active points of the cement particle surface. This reduces the transformation rate from a caudal style to either a ring or horizontal PNS adsorptive style, as confirmed by dynamic adsorptive models. These are important mechanisms of SG reduction in the fluidity loss of cement pastes with PNS.