Study of the influence of micro-and nano-cellulose on the growth and carbonation kinetics of portlandite crystals

Restoration of historical buildings contributes to the preservation of history and identity of the cities, but also, in the current climate crisis, an alternative solution to reduce the environmental impact of the construction sector, which is one of the main global contributors to green-house gas emissions and waste production. It can be also claimed that the most sustainable building is the one that has already been built. An important aspect to consider for the restoration of built heritage is the use of compatible materials, such as lime-based mortars, that should be preferred over cement. However, their slow setting and hardening (via carbonation), and, in some cases, poor durability prevent their full acceptance and widespread use. One course of action is to improve the quality of the binder via an innovative approach: inclusion of natural organic additives during the slaking process of CaO. This is expected to have a higher impact than their inclusion in the mortar’s mix design. In the present work the analysis of the growth of Ca(OH)2 crystals following their crystallization in the presence of micro- and nano-cellulose is studied, together with the morphological changes that these additives induce on portlandite crystals. Moreover, the study of the carbonation kinetics of the modified portlandite crystals gives insights on the effect that these additives have on the quality of the binder. The promising results highlight the potential of micro- and nano-cellulose as sustainable additives for lime-based binders. Furthermore, these additives can be obtained from industrial wastes, promoting a circular economy.