Effectiveness and Compatibility of a Novel Sustainable Method for Stone Consolidation Based on Di-Ammonium Phosphate and Calcium-Based Nanomaterials

Abstract

External surfaces of stones used in historic buildings often carry high artistic value and need to be preserved from the damages of time, especially from the detrimental effects of the weathering. This study aimed to test the effectiveness and compatibility of some new environmentally-friendly materials for stone consolidation, as the use thereof has been so far poorly investigated. The treatments were based on combinations of an aqueous solution of di-ammonium phosphate (DAP) and two calcium-based nanomaterials, namely a commercial nanosuspension of Ca(OH)2 and a novel nanosuspension of calcite. The treatments were applied to samples of two porous stones: a limestone and a sandstone. The effectiveness of the treatments was assessed using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, ultrasound pulse velocity test, colour measurements, and capillary water absorption test. The results suggest that the combined use of DAP and Ca-based nanosuspensions can be advantageous over other commonly used consolidants in terms of retreatability and physical-chemical compatibility with the stone. Some limitations are also highlighted, such as the uneven distribution and low penetration of the consolidants.

Selected Aspects Regarding the Restoration/Conservation of Traditional Wood and Masonry Building Materials: A Short Overview of the Last Decade Findings

“…The topic was recently reviewed by Sassoni [109], so a very thorough presentation of the method would be redundant. We have chosen to discuss only a modification of the method, proposed by Pesce et al [110]. The in situ formation of a hydroxyapatite consolidating layer was achieved using aqueous solution of diammonium phosphate and two types of calcium nanosuspensions, calcium hydroxide and calcite (calcium carbonate), on limestone and sandstone.…”

Nanolime-Based Mixtures for Treatment of Limestone Offering Table Excavated From Saqqara, Egypt: Analytical, Experimental and Applied Study

“…The consolidation treatment aims to recuperate and recover the cohesion between the grains of damaged stones, in addition to improving their mechanical properties and consequently increasing their durability (Pesce, et al, 2019). According to the data of compression strength, all the studied treatments increased the compression strength of the treated limestone samples.…”

Advances in the application of nanomaterials for natural stone conservation

“…Due to its nanostructured size and higher specific surface area, nanolime displays several advantages compared to traditional limewater: higher colloidal stability and good penetration into the stone pores, reducing the formation of white surface stains [31]; the avaialbility of several synthesis routes to finetune the particle size and control the reactivity and surface properties [32,33]; and higher reactivity resulting in a beneficial reduction of the carbonation time. Since the introduction of different commercial products, nanolimes have been widely applied for the consolidation of limestones [28,32,[34][35][36][37][38][39][40][41], lime mortars [35,[42][43][44][45], and wall paintings [32,46]. The selection of the concentration and type of solvent of the suspension and of the application methodology are important factors to consider prior to the conservation intervention.…”