Activation of ground granulated blast-furnace slag with calcium hydroxide nanoparticles towards the consolidation of adobe

Adobe earthen materials, one of the oldest and most widespread forms of construction, are easily susceptible to degradation due to their porous structure and variable composition. Effective consolidation treatments should involve compatible materials and allow for a good penetration, to restore grains cohesion. Among all possible alternatives for the restoration of earthen masonry, the formation in-situ of calcium silicate hydrate has been reported as a compatible and efficient solution. In this study we report the investigation of consolidation treatments based on ground granulated blast furnace slag (a secondary raw material from steel production) activated with calcium hydroxide, either as bulk or nanometric particles, to allow for the consolidation of porous structures through the formation of calcium silicate hydrate. Different dispersions were thoroughly characterized, and the best formulation was applied on adobe mock-up samples. The effect of the treatment revealed that calcium hydroxide nanoparticles, synthesized through an easy and convenient process, can accelerate the activation of the slag and increase the formation of the cementitious binder, both on the surface of the treated substrates, and into their porous matrix. These results pave the way towards the use of nano-sized alkali activators to boost the hydration of geopolymers.