Viscoelastic - Non-Newtonian transitory response of cement paste and superplasticizer combinations

Cement paste exhibits mechanical response similar to a viscoelastic fluid. When superplasticizers are added, the viscoelastic effects diminishes and the mixture exhibits non-Newtonian response. Under complete dispersion, the mixture exhibits a Newtonian response. To develop an understanding on the choice of superplasticizer (dosage and type), it is necessary that one understands the transitory response of cement paste and superplasticizer combinations. This investigation is related to developing such understanding. Ordinary 53 grade Portland cement was used with superplasticizers from the naphthalene, melamine and polycarboxylate family of products. Creep and recovery and stress relaxation experimental data was collected under different loading combinations at room temperature. It was seen that as the dosage increased, the response varied from a viscoelastic fluid to a non-Newtonian fluid. The experimental data was modelled using an upper convected Burgers' model. The polycarboxylate based superplasticizer exhibited interesting trends in terms of the viscoelastic - non-Newtonian transition.