Waterglass-based clinker-free cementitious systems

Sodium silicate in the form of waterglass (WG) typically has a high pozzolanic reactivity; therefore, it is a good candidate as a primary material in clinker-free systems. However, these systems have higher water demand, higher porosity, and lower flexural strength than comparable portland cement-based systems. The main purpose of this paper is to address these challenges, and how WG-based systems can be improved using other additions such as silica fume (SF) and cellulose crystals (CNC). Using WG as the main source of silica, different mixtures with and without CNC and SF are tested to explore if the porosity and water demand can be decreased to produce functional binders with increased flexural strength. The study parameters included calcium source, calcium-to-WG ratio, water-to-solids ratio, WG modulus, alkalinity, and CNC/SF dosage. 0.4% CNC and 10% SF replacement reduced the porosity of the low-modulus WG mixtures by about 10% and increased the flexural strength by about 100%. CNC acted as a water reducer/retarder, allowing better SF utilization while maintaining workability. CNC also slowed the initial reactions, facilitated secondary reactions, and reduced chemical shrinkage. The research concluded that clinker-free binders created using WG, CH, CNC, and SF are feasible.