Our nation's infrastructure and long term containment of nuclear waste are two critical applications requiring concrete with an increased service life. In this paper, a new paradigm for increasing concrete service life is presented. Since diffusion of deleterious species such as chloride and sulfate ions always occurs through the solution phase within a concrete, appropriate viscosity modifiers are utilized to reduce the diffusion rate by increasing the hydrodynamic drag coefficient. The size of the viscosity modifier is critical, with only nano-sized viscosity enhancers providing the desired diffusion reduction. Studies have been carried out both in solutions and in mortars to verify this new approach to doubling concrete service life. Three different methods of introducing the admixture into the mortars have been explored, namely direct introduction into the mixing water, addition as a topical curing solution, and incorporation via lightweight fine aggregates (LWA) that are pre-wetted with a concentrated solution of the viscosity modifier. While all three methods produce a reduction in chloride penetration depth, the greatest reduction is provided when the admixture is incorporated into the LWA.
Citation: Concrete International
Pub Type: Journals
Building technology, concrete, diffusion, service life, viscosity