Influence of curing conditions on the mechanical and hydric performance of air-lime mortars with nano-Ca(OH)2 and nano-SiO2 additions

In search of compatible materials to speed up the strength and carbonation in lime mortars, nanoparticles show significant potential. This research explores the mechanical and physical characteristics of air lime mortars with silica sand and two types of dispersions based on nanoportlandite (nP) and nanosilica (nS) used as additions according to different curing conditions. Thus, samples kept under laboratory conditions (23 degrees C, 40% RH and 700 ppm CO2) and in a climatic chamber (20 degrees C, 75% RH and 1600 ppm CO2) were tested to understand the influence of environmental conditions in these types of systems. Results: Nanoparticle dispersions have a notable effect on the mechanical and hydric performance of lime mortars as a function not only of the components but also of the curing conditions. Solvents modified the water/binder ratio with an increase of microporosity and pore volume, which negatively affected mechanical and hydric properties. However, microporosity is reduced with nanoparticles which favours the deformation capacity of the mortars. Moreover, some interesting findings arise regarding the effect of solvent and the morpho-structural properties of calcium silicate hydrate (C-S-H). Differences in terms of morphology, fibre size, flexibility or content stand out, attending to the type of nanoparticles and the curing conditions. Air lime mortar with one part of nanoportlandite and 2 of nanosilica achieved the highest rates of carbonation and hydration products under chamber conditions compared to those located in laboratory conditions.

Automated summary

The use of nanoparticles in lime mortars has a significant impact on their mechanical and hydric properties, which is influenced by the type of nanoparticles and curing conditions.