Characteristics of structural concrete containing fluorosilicate-based admixture (FBA) for improving water-tightness

• Properties of concrete with fluorosilicate-based admixture (FBA) for improving water-tightness was examined.
• FBA fills the pore and space between hydrate products in the hardened concrete.
• The addition of FBA enhances the water-tightness and ductility of concrete.

Water-tightness performance of concrete is very important from the aspects of water-proof and durability of the reinforced concrete structure. In this study, fluorosilicate-based admixture (FBA) was used for concrete to improve the water-tightness. This paper provides the results of experimental program on the mechanical properties of structural concrete containing different levels of FBA. The experimental program was planned to investigate the effects of FBA for improving the water-tightness on the fresh and hardened properties of structural concrete. Experimental program focused on concrete mixtures with fixed water-to-binder (W/B) ratio of 0.50 and a constant total binder content of 360 kg/m3. The added percentages of FBA by mass of cement were: 0%, 0.5%, 1.0%, 1.5% and 2.0%. The test results show that as the added percentage of FBA increased, the workability of fresh concrete as well as the mechanical properties including the water-tightness of hardened concrete improved. Also the addition of FBA effectively reduced free shrinkage strain of structural concrete, and resulted in a considerable reduction in shrinkage cracks.