Nanolime products are one of the most promising consolidation methods for historic calcareous substrates. Whilst the popularity of nanolime has been growing, its consolidation mechanism still needs to be fully understood when applied to highly porous substrates. The aim of this paper is to compare the three available nanolime products in terms of consolidation efficacy on lime mortar specimens. It is shown that repeated applications of a low concentrated nanolime can increase the superficial cohesion and the mechanical strength of the mortar within 1cm from the surface, while also reducing porosity, number of micro-pores and capillary water absorption coefficient. Nanorestore Plus® yielded the highest short-term consolidation effect. However, L'Aquila nanolime showed a higher durability which was attributed to a better developed crystalline structure.

Nanolime is a promising consolidant for the conservation of most historic structures thanks to its high compatibility with carbonate-based substrates. Nanolime can recover the superficial cohesion of deteriorated surfaces thanks to its potential to complete the carbonation process, recreating a thin network of new cementing calcium carbonate. In this paper, the nanolime was produced by an innovative, time and energy-saving and scalable method, and its efficacy was tested preliminarily on biocalcarenite stones from Agrigento. The stones characterization as well as the treatment effectiveness, in terms of protection against water and superficial consolidation, was investigated by several techniques such as X-ray fluorescence, X-ray diffraction, scotch tape test, water absorption by capillarity, mercury intrusion porosimetry, drilling resistance measurement system and colorimeter. Investigations showed that nanolime could guarantee a complete transformation in pure calcite together with a superficial consolidation and a reduction in water absorption.

Nanolime is a promising consolidation treatment for the conservation of historic structures thanks to its high compatibility with carbonate-based substrates. Nanolime products can effectively reduce the porosity and restore the mechanical properties of treated surfaces. Whilst the popularity of nanolime has been growing, its consolidation mechanism still needs to be fully understood when applied to porous substrates. The aim of this paper is to determine the influence of nanolime particle size and substrate pore structure on the effectiveness of nanolime treatments. Results suggest that nanolime products with larger particle size tend to close predominantly large sized pores, while nanolime with smaller particle size tends to fill both large and small pores equally. These results suggest that for a consolidation treatment, the nanolime product must be chosen taking into consideration the substrate pore structure.

For almost 1500 years, many ancient Chinese mortars have remained unaltered despite exposure to atmospheric agents. The main reason for this long-term durability is the addition of sticky rice water to the standard mortar ingredients (lime and sand) following traditional recipes. In recent years, these mortars have been methodically studied leading to the conclusion that amylopectin, a polysaccharide in the sticky rice, plays a crucial role in regulating calcite crystals growth, creating a denser microstructure and providing the mortar with hydrophobic properties which contributed to their survival. In recent decades, nanolime products based on Ca(OH) 2 nanoparticles suspended in alcohol or hydro-alcoholic medium have been extensively used for the consolidation of calcareous substrates mainly due to their chemical affinity and absence of side effects. Nanolime products have resulted in successful superficial consolidations. However, in-depth consolidation still needs to be achieved, and research needs to focus on ways to attain this objective. This study aimed to test a novel approach consisting of applying a pre-treatment of sticky rice and subsequently the nanolime. The resulting consolidation was evaluated by measuring changes of superficial cohesion, porosity, contact angle, drilling resistance, water absorption by capillarity, drying rate and aesthetic properties. The durability of the treatments was investigated by exposing samples to accelerated weathering. Results showed that the use of sticky rice in combination with nanolime yields a higher degree of consolidation increasing drilling resistance and delivering hydrophobic properties although prolonged exposure to high temperature and moisture can compromise treatment durability.

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