D3 method: Direct and delayed dosing: New insights into specific surface area modification by superplasticizers
Shengnan Sha, Sirajuddin Moghul, Robert J. Flatt
Abstract
In cement suspensions, a part of the superplasticizers measured as adsorbed by solution depletion, is actually consumed uselessly by intercalation, coprecipitation, micellization and/or modification of early hydrate surface area. This amount is often referred to as lost, as it is not effective as a dispersant. Despite extensive research on the subject, mechanisms responsible for this remain unclear. With a focus on polycarboxylate superplasticizers (PCEs) and Ordinary Portland cement (OPC)-limestone blended cements, this paper proposes a “direct and delayed dosing (D3)” method to shed new light onto this age-old question. Thereby, the amounts of lost PCE are shown to be proportional to the amount of PCE included in the mixing water and to result directly from an increase in specific surface area.