The effect of alginates on the hydration of calcium aluminate cement. (15th May 2020)

• Record Type: Journal Article
• Authors: Engbert, Alexander; Gruber, Stefanie; Plank, Johann
• Is Part Of: Carbohydrate polymers. Volume 236(2020)
• Publication Date: 2020-05-15
• Subjects: C CaO -- A Al2O3 -- S SiO2 -- H H2O -- F Fe2O3 -- T TiO2 -- M MgO; Polysaccharide -- Alginate -- Calcium aluminate cement -- Accelerator -- Hydration -- Calcium complexation; Polysaccharides -- Periodicals; Polysaccharides -- Periodicals; Polysaccharides -- Périodiques; Electronic journals; 547.78
• DOI: 10.1016/j.carbpol.2020.116038
• Languages: English
• ISSNs: 0144-8617

Abstract

Graphical abstract: Highlights: Alginate behaves as an accelerator in calcium aluminate cement. Significant increase in early strength achievable. Accelerating mechanism is based on calcium complexation. Alginate promotes C-A-H formation. Partial replacement of lithium salts possible with alginate. Abstract: The hydration of calcium aluminate cement (CAC) in the presence of sodium alginate which is known to slightly retard Portland cement, was studied using heat flow calorimetry and mortar strength testing. Most surprisingly, addition of alginate resulted in an earlier occurrence of the maximal heat release as well as an increased early strength, thus confirming that in CAC alginate acts as accelerator. The thickening effect of alginate was effectively compensated using a superplasticizer while retaining its accelerating property. An investigation of the pore solution composition indicated that in the presence of alginate the concentration of calcium ions was reduced. Such effect normally causes retardation of cement hydration and should delay the formation of C-A-H phases. Apparently, the strong calcium ion complexing ability of alginate promotes the formation of C-A-H via e.g. a templating effect. A combined application of alginates and lithium salts presents a viable option to reduce the lithium consumption in CAC acceleration.