Sticky rice–nanolime as a consolidation treatment for lime mortars

Abstract

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.

Preventing the Undesired Surface Veiling after Nanolime Treatments on Wall Paintings: Preliminary Investigations

“…First of all, the specimens in which the consolidation treatment has been applied removing the excess of product after each application (NC1 and NC2) showed, in general terms, an acceptable consolidation effectiveness since they presented a significant increase in superficial cohesion (57-70%), a reduction in Wa (20-21% reduction) while did not significantly induced the so-called white glazing side-effect commonly caused by the nanolime treatments, as reported in the literature [5][6][7][8]14,15,[25][26][27][28]. While the rest of consolidation treatments showed a regular white "stratum" covering up the pictorial layer, NC1 and NC2 only showed some small whitish deposits, therefore the difference of aspect and colour they showed after the application of the treatment is significantly lower (∆E* 3.99 ± 0.96).…”

“…Since their discovery in the early 2000s by the University of Florence-CSGI (Florence, Italy), the effectiveness of nanolimes has been tested specially in wall paintings, obtaining successful results in terms of superficial cohesion recovery, reduction of water absorption by capillarity and increase of the mechanical properties of the pictorial layer and support [7,[9][10][11][12][13]. However, despite the significant increase in superficial cohesion, the consolidation usually generates whitish deposits on the surface which frequently covers the pictorial layer, modifying its aspect, colour and interpretation of the historical artwork [5,14,15]. Such a "veiling" or white "glazing" is highly detrimental and there is a strong need for research aimed at preventing its appearance.…”

“…Whereas this side-effect is recurrently mentioned in most of scientific articles concerning nanolime consolidation treatments [6][7][8][9][10][11][12][13][14][15], and it is mentioned in the information technical data sheet provided by both nanolime distributors (e.g., Calosil ® and Nanorestore ® ) [16,17], there is no literature or scientific evidence which clearly specify neither the most convenient application method to avoid the generation of those glazings without altering the consolidating properties, nor the possible subsequent treatments to remove them. Following the technical recommendations provided by both nanolime commercially available brands (Calosil ® and Nanorestore ® ), it is also not clear which guidelines should be followed: whereas Nanorestore suggests washing the pictorial layer after each application to remove the excess of product remaining [16], Calosil suggests the possibility of diluting the consolidating product to obtain lower concentrations, as a way to prevent the appearance of superficial glazings [17].…”

Experimental investigation on compressive strength of concrete with sticky rice pulp at different ages (the experiment of concrete with sticky rice pulp)

“…As an organic substance, sticky rice pulp acts as a template effect for biomineralization, 26,27 sticky rice pulp contains a large amount of amylopectin, which can provide a binding site during the hydration of cement, so that the hydration products (CSH) are arranged in a certain pattern. Meanwhile, in the reaction process, amylopectin controls the microscopic size of gelatinous materials generated by the reaction, so that the structure becomes more dense 7,10,28,29 (as shown in Figure 12b). Secondly, the unreacted sticky rice pulp is used as a cementing agent to fill the gap, and it is close to the cementing material and coarse and fine aggregate.…”

Ανάπτυξη Νανο-Σύνθετων Υλικών Με Βάση Το Ασβέστιο Για Την Ενίσχυση Των Πορωδών Υλικών Δόμησης Σε Αρχιτεκτονικά Μνημεία Και Παραδοσιακές Κατασκευές

“…The application of the dispersion of Ca(OH)2nanoparticles synthesized via this methodology with a pre-treatment of the substrate with a sticky rise was recently studied. The efficiency level of the consolidation action to weathering conditions was rather reduced [194].…”