Title: Superplasticizer-Nanosilica Compatibility: Assessment and Optimization
Author(s): Harry Brace and Emilio Garcia-Taengua
Publication: Materials Journal
Appears on pages(s): 95-103
Keywords: chemical admixtures; compatibility; compressive strength; fresh state performance; Marsh funnel test; paste; statistical models
Nanoparticles can yield significant benefits in cement-based products but can pose problems regarding dispersion and optimal doses. This paper proposes an inexpensive methodology to compare superplasticizers in terms of their compatibility with nanosilica, providing concrete technologists with a practical tool to select the best combinations. A series of cement pastes were produced, incorporating nanosilica and two different superplasticizers at different dosages. Their fresh state performance was assessed by means of the Marsh funnel test, and their compressive strength was determined at 28 days. The compatibility between nanosilica and superplasticizers was defined and described by developing semi-empirical models. These were used to identify optimal combinations which maximize the flowability and compressive strength and minimize their variability. It was concluded that the optimization of cement pastes with nanosilica was feasible only when the superplasticizer used is highly compatible. Careful selection of the superplasticizer proved to be critical in ensuring the efficiency and cost-effectiveness of the addition of nanosilica.