Stone Substrate Research Articles

Evaluating two nanosilica dimensional range for the consolidation of degraded silicate stones

The application of silica nanoparticles strengthening agents in conservation of monumental and architectural heritage field is currently a challenge of particular interest. Some commercial products are already on the market and several studies highlighted the related strength and weakness. In order to contribute to the knowledge of the interaction between nanoparticles and stone materials as well as to provide key elements to improve the approach to conservative treatments, two silica nanoparticles products for the consolidation of silicate stones were developed in the laboratory. Bianco Sardo granite, Firenzuola and Muggia sandstones were selected as substrates for the experimentation after a laboratory investigation of their open porosity. Silica nanoparticles having two different particles size, both compatible with the porosimetric features of the selected stones, were synthesized and dispersed in an ethanol–water solution. The carrier was specifically studied for avoiding the agglomeration of silica nanoparticles and facilitating the penetration of the products in the stone substrates. Sound and artificially aged specimens were impregnated by capillary absorption method and the effectiveness of the treatment was evaluated through morphological and physical analyses. Microscopic observations, colorimetric analyses, sponge tests, ultrasound velocity determinations and porosimetric measurements showed positive results, which encourage, on one hand, the use of silica nanoparticles for consolidating silicate stones, on the other hand, further researches aimed to improve the synthesized products by reaching a deeper penetration and the reduction of water absorption.

Examining the Potential of Enzyme-Based Detergents to Remove Biofouling from Limestone Heritage

Commonwealth war cemeteries commemorate the fallen of both world wars. Every casualty is remembered with a memorial or on a headstone. However, the headstones need to be maintained extensively, as microorganisms easily colonise them, affecting legibility and the stone substrate in the longer term. In the past, pesticides and other chemicals were popular to clean headstones, but due to raised environmental concerns, new treatment strategies are necessary. Within conservation science, enzymes have emerged as a popular tool for restoration. However, studies related to the use of enzymes for stone conservation are limited. Within this preliminary study, we applied commercially available enzyme-based treatments on biofouled natural building stones in the laboratory and in situ. Photography and spectrophotometry were used to monitor the effect of the treatment. The application of enzymes resulted in rapid disintegration of biological pigments, whereas visual improvement occurred more gradually. The successful application of enzymes suggests their potential to replace pesticides as the principal cleaning agent for headstones and natural building stones in a more general fashion.

Lichen impact on sandstone hardness is species‐specific

AbstractThe balance between lichen biodeterioration and bioprotection processes on stone surfaces depends on many variables and is crucial to understanding the role of lichens in biogeomorphology and their threat to stone heritage conservation. However, stones colonized by lichens have still been mostly examined in terms of affected volumes and physico‐chemical modes of interactions, overlooking the overall effects on properties related to surface durability. In this study, the impact of lichen colonization patterns on Cortemilia sandstone was examined beneath thalli of three lichen species. Rock hardness, a proxy for rock durability, was measured at different depths from the surface using an Equotip hardness tester and compared to that of freshly cut surfaces and exposed surfaces uncolonized by lichens. Mineralogical analyses were performed by X‐ray powder diffraction on rock beneath lichen colonization, in comparison with unweathered rock. Equotip analyses quantified a differential, species‐specific decrease in stone hardness. This variability was related to differences in hyphal penetration patterns and, possibly, calcite (re‐)precipitation. In particular, in the case of the species most impacting rock hardness, X‐ray diffraction patterns of calcite showed a remarkable stability of crystallographic plane (01–12), known to be enhanced in the presence of organic chelants. These results confirm that decisions on lichen removal from stone surfaces should consider species‐specific behaviour. Moreover, the innovative approach of measuring stone hardness variation in association with the analysis of biomineralization processes contributes to unveil the extension of the sphere of lichen interaction within the stone substrate beyond the limit of the hyphal penetration.

Application of resin-TiO2 nanoparticle hybrid coatings on travertine stones to investigate their durability under artificial aging tests

Three different stone coating products including industrial resin, resin-anatase nanoparticles and resin-rutile nanoparticles (NPs) were used to evaluate their stone surface protection effect against thermal shock and salt crystallization on three types of porous travertine stones. The results showed that the use of nanoparticles of both TiO2 polymorphs (rutile and anatase) dispersedly in resin, significantly increased durability of the stones surfaces during the aging tests. No color change in the sample surfaces is another advantage of the resin-TiO2 NPs hybrid coating. Product with anatase nanoparticles shows by far the best performance in protecting the stone surfaces. In both aging tests, samples coated by resin-anatase NPs had the lowest mass changes and the highest surface hardness compared to samples coated by the other coatings. Mineralogy, porosity and microbial activity textural features controlled the durability of the studied stones. Mono-mineral composition and macro porosity of studied samples explain their significant durability against the thermal shock process. On the other hand, the growth of salt crystals in the pore space of the stones in some cases induced macroscopic cracks, particularly in Abarkooh sample with high porosity and microbial textural features Scanning electron microscopy observation confirms that the samples underwent microcracking processes related mainly to salt crystallization pressures. Finally it can be concluded that the resin-TiO2 NPs hybrid coating had a good compatibility with the stone substrate and could be very promising to protect the porous stone façades against natural aging processes.

A Lichens-Mediated Mechanism for Environmental Biodeterioration

As mediators in soil formation, lichens play an essential role in the physical and biological formation of the natural environment. A recent study showed that they are capable of biodegrading stone substrates in a little amount of time, despite being excluded in a geological setting. Many species, mainly those able to produce an oxalate at the thallus-substratum interface, can alter the surface, affecting it chemically. The oxalate remains a noticeable increase even after the lichen has faded, and it makes a major contribution to the structure and composition of the thallus itself. These severe oxalate deposits on historical sites have been alternatively attributed to the earlier as the consequence of air pollutants, prior mechanical/chemical renovation treatments, as well as environmental deterioration. Lichen growth on building materials and biodegradation are frequently based on environmental variables. The biogeophysical and biogeochemical weathering of the substrate by the lichens is the mechanism underlying biodegradation. For stone surfaces, lichens can endeavor bio protection by acting as a barrier against weathering, holding humidity, improving permeability, reducing heat stress and erosion, and absorbing contaminants. Lichen’s significance as a biodeteriorant, its colonization and impact on monuments, as well as bioprotection, are all discussed in the current review.

Epiphyton in Agricultural Streams: Structural Control and Comparison to Epilithon

Stream biofilms play an important role in the structure, functioning, and integrity of agricultural streams. In many lowland streams, macrophyte vegetation is abundant and functions as an important substrate for biofilm (epiphyton) in addition to the gravel and stone substrate for epilithon on the stream bed. We expect that reach-scale habitat conditions in streams (e.g., nutrient availability, hydraulic conditions) affect the epiphyton and epilithon biomass and composition, and that this effect will be substrate-specific (macrophytes and stones). The objectives of our study were (i) to describe concurrent changes in epiphyton and epilithon biomass and composition over a year in agricultural streams, and (ii) to determine the substrate specific reach-scale habitat drivers for the epiphyton and epilithon structure. We monitored epiphyton and epilithon biofilm biomass and composition at three-week intervals and reach-scale environmental conditions daily during a year for two agricultural steams. The results showed that epiphyton and epilithon communities differed in biomass, having high substrate specific biomass in epilithon compared to epiphyton. Epiphyton was mainly composed of diatom and green algae, while cyanobacteria were more important in epilithon, and the diatom species composition varied between the two biofilm types. Epiphyton structural properties were less influenced by reach-scale hydrology and nutrient availability compared to epilithon. The overall explanatory power of the measured environmental variables was low, probably due to micro-scale habitat effects and interactive processes within stream biofilms. Knowledge of biofilm control in agricultural streams is important in order to improve management strategies, and future studies should improve the understanding of micro-scale habitat conditions, interactive relationships within biofilms and between the biofilm and the substrates.

TEOS-PDMS-Calcium Oxalate Hydrophobic Nanocomposite for Protection and Stone Consolidation

A treatment for both protection and consolidation, was synthesized in a simplified procedure through the sol gel process. Synthesized nano-calcium oxalate (CaOx) was incorporated into tetraethoxysilane (TEOS) and polydimethylsiloxane (PDMS), providing a hybrid hydrophobic consolidant nanocomposite. Oxalic acid was selected due to its ability to catalyse the hydrolysis of TEOS, as a drying control agent, but also because of its contribution at the formation of the calcium oxalate in reaction with calcium hydroxide. CaOx, incorporated into the silica matrix of the final copolymer, exhibits interfacial compatibility with the stone substrate and simultaneously strengthens the treated surface, since CaOx appears to be more stable than calcium carbonate. The hydrolysis of TEOS, as well as the formation of CaOx was evaluated through thermogravimetric analysis (TG/DTA). The nanocomposite consists of particles with approximately 7–700 nm in size range, as shown in TEM images. The consolidation, in combination with the hydrophobicity of surface resulted in an increase of the resistance to decay. Mechanical properties were enhanced as evaluated by ultrasonic pulse velocity on treated and untreated surfaces. Furthermore, water contact angle, as well as water absorption by capillarity test, showed improved water repellency of treated stones. Finally, this treatment doesn’t alter the aesthetic surface parameters, a fact that is essential in cultural heritage conservation, while the consolidant remains intact under UV and moisture exposure.

Time-Resolved ATR-FTIR Spectroscopy and Macro ATR-FTIR Spectroscopic Imaging of Inorganic Treatments for Stone Conservation.

In this study, the novel application of ATR–FTIR spectroscopy and macro ATR–FTIR spectroscopic imaging overcame an analytical challenge in conservation science: the time-resolved, chemical, and spatial investigation of the reaction of inorganic treatments for stone conservation (ammonium oxalate, AmOx; ammonium phosphate, DAP) occurring in water-based solutions. The aim was to (1) assess the composition and localization of reaction products and their phase variation during the reaction in real time and directly in an aqueous environment and (2) investigate the reaction of AmOx and DAP with calcite and the transformations induced to the substrate with a time-resolved approach. The new analytical results showed that for both treatments, the formation of new crystalline phases initiated at the early stages of the reaction. Their composition changed during the treatment and led to more stable phases. The reactivity of the stone substrate to the treatments varied as a function of the stone material features, such as the specific surface area. A clear influence of post-treatment rinsing on the final composition of reaction phases was observed. Above all, our research demonstrates the actual feasibility, practicality, and high potential of an advanced ATR–FTIR spectroscopic approach to investigate the behavior of conservation treatments and provided new analytical tools to address the choices of conservation in pilot worksites. Lastly, this study opens novel analytical perspectives based on the new possible applications of ATR–FTIR spectroscopic imaging in the field of conservation science, materials science, and analytical chemistry.

Eco-Friendly Protective Coating to Extend the Life of Art-Works and Structures Made in Porous Stone Materials

The application of hydrophobic treatments to stone surfaces is the most common proven method to prevent, or at least limit, the degradation of stone-made constructions and artworks brought about by the ingress and action of water, in particular in the case of very porous stone materials. To avoid the use of protective products containing harmful solvents, new green products have been proposed. In this paper, an eco-friendly hydrophobic coating, based on a fluorine polymer dispersed in water, was deeply analyzed to evaluate its protective properties, especially for very porous stone substrates. To this aim, a wide characterization of treated and untreated Lecce stone elements, i.e., a stone typical of the Apulia region, was carried out to assess the optimum required amount, the effectiveness and the protective capability, even against graffiti staining, of the green hydrophobic treatment, still allowing the stone to retain adequate vapor permeability. The efficacy of the eco-friendly product was analyzed also after a short time (four weeks) of outdoor exposure. Suitable performance and short-term durability of the green hydrophobic coating were found, comparable or even greater than those reported in the current literature for other widespread commercial products, confirming the capability of the product to preserve porous stone surfaces even in absence of solvents in its formulation. The study also allowed to experiment with the “contact sponge” test as an appropriate method for evaluating the water absorption properties of the stone.

Multifunctional and Durable Coatings for Stone Protection Based on Gd-Doped Nanocomposites

The development of nanocomposite materials with multifunctional protective features is an urgent need in many fields. However, few works have studied the durability of these materials. Even though TiO2 nanoparticles have been extensively applied for self-cleaning effect, it displays a weak activity under visible light. Hence, in this study, pure and Gd-doped TiO2 nanoparticles (molar ratios of doping ions/Ti are 0.1 and 1) were synthesised, characterised, and then mixed with polydimethylsiloxane (PDMS), used as a binder, in order to produce a homogenised thin film on a very porous stone substrate. To our knowledge, Gd-doped TiO2/PDMS protective coatings are studied for the first time for application on historic structures. The protective coatings developed in this work are intended to reduce the surface wettability of the stone and protect the historic stones from dye pollution and microorganism colonisation. Moreover, in this study, the durability of the developed nanocomposite was deeply studied to evaluate the stability of the coatings. Results confirmed that samples treated with the lowest concentrations of Gd ions (0.1 mol%) showed acceptable chromatic variations, a good repellent feature, acceptable water vapour permeability, good durability, the highest self-cleaning activity, and good inhibitory behaviour against microbial colonisation.

Characterization of black crusts developed on historic stones with diverse mineralogy under different air quality environments

Black crusts (BCs) are one of the most critical alteration forms found on stones belonging to architectural heritage. Since they could be considered as passive samplers of atmospheric pollution, it would be plausible to establish relations between the air contamination and the BCs. With this aim, we have characterized BCs collected on historic buildings from two Spanish cities (Granada and Vigo) with different polluted atmospheres, as well as formed on stone substrates of varied mineralogy and texture. Likewise, in order to assess the impact of the atmospheric pollutants on the growth of BCs, quartz fiber filters were used as surrogate substrates and placed nearby the studied buildings to collect and analyze the aerosol particulate matter (PM). To this end, an array of complementary analytical techniques was used to evaluate the mineralogy, chemical composition, and texture of the BCs and to establish the correlation with the ions, OC (organic carbon), and EC (elemental carbon) detected in the PM on the quartz fiber filters. As result, BCs developed on carbonate substrates from Granada show more complex structure than those from Vigo, which are thinner because of frequent rain episodes. In both cities, NaCl, Pb-Cl, and Ca-Cl-rich particles, Ca-phosphate particles and clusters of Ba-sulfate-rich particles were detected. However, metal-rich rounded particles were more abundant in Granada’s BCs, including soot particles. BCs from Granada were richer in carbonaceous components (OC and EC) than the Vigo’s BCs. Although in the filters PM did not show EC—mainly due to traffic—, in the BCs from both locations OC and EC were detected. Therefore, this different composition was related to the mineralogy of the stones and the higher pollution of Granada in contrast to the industrial and sea-exposed city of Vigo.

A New Methodological Approach to Correlate Protective and Microscopic Properties by Soft X-ray Microscopy and Solid State NMR Spectroscopy: The Case of Cusa’s Stone

Hydrophobic treatment is one of the most important interventions usually carried out for the conservation of stone artefacts and monuments. The study here reported aims to answer a general question about how two polymers confer different protective performance. Two fluorinated-based polymer formulates applied on samples of Cusa’s stone confer a different level of water repellence and water vapour permeability. The observed protection action is here explained on the basis of chemico-physical interactions. The distribution of the polymer in the pore network was investigated using scanning electron microscopy and X-ray microscopy. The interactions between the stone substrate and the protective agents were investigated by means of solid state NMR spectroscopy. The ss-NMR findings reveal no significant changes in the chemical neighbourhood of the observed nuclei of each protective agent when applied onto the stone surface and provide information on the changes in the organization and dynamics of the studied systems, as well as on the mobility of polymer chains. This allowed us to explain the different macroscopic behaviours provided by each protective agent to the stone substrate.

Moisture Interactions Between Mosses and Their Underlying Stone Substrates

ABSTRACT Mosses are a common type of organism found colonising stone in both the natural and built environment. People responsible for managing and conserving historic buildings often worry that mosses can cause biodeterioration, but there is very little research to date on what controls moss growth and the nature and magnitude of their impact. To help fill this knowledge gap, research has been carried out on limestone walls at Kelmscott Manor, the churchyard at Chipping Norton, and in the laboratory on limestone test blocks, to examine the impact of microclimate variations on both the initial colonisation and spread of mosses, and the impact of moss colonisation on temperature, relative humidity, and moisture conditions. The research used a combination of non-destructive and invasive tests to determine the impact of mosses on moisture relations through direct impacts on surface moisture, water absorption capacity, and open porosity. From the results presented, we can infer that mosses have an impact on water uptake and retention on mortar and limestone at both the surface and subsurface level, and that they may play a role in ‘shielding’ the underlying substrate from light rainfall events. The experimental data also suggests that in certain cases, removing mosses may have more of an impact on moisture regimes than leaving them in situ.

Consolidation and Adhesion of Pictorial Layers on a Stone Substrate. The Study Case of the Virgin with the Child from Palazzo Madama, in Turin

The study and the restoration of a polychrome limestone statue representing the Virgin with the Child, from Palazzo Madama in Turin (NW Italy) offered interesting conservation issue related to the polychromy on stone. To preserve the pictorial layers, it was necessary to re-establish the cohesion among the different polychrome layers (original and repainted) and the adhesion between polychrome film and the stone substrate. Particular attention was paid to the choice of intervention materials, selected through a preliminary survey of the scientific literature, and then verified by laboratory tests (tape test, colorimetric test, and permeability test). The most suitable product should to be able to penetrate porosity, to consolidate the layers, to make the pictorial film adhere with the stone surface, and to avoid changes in the colour and in the permeability. The material chosen also had to ensure compatibility with the cleaning method that could only take place after the consolidation of the pictorial layers due to the problematic state of preservation. A range of products, characterised by their small particle size and low viscosity, was tested, and a micro-acrylic resin was selected and successfully applied on the polychromy of the sculpture.

Ag-TiO2/PDMS nanocomposite protective coatings: Synthesis, characterization, and use as a self-cleaning and antimicrobial agent

The protection of our artifacts becomes a necessity due to several decay phenomena induced by pollution, microorganism colonization, and water. This research study has been focused on elaborating photo-activated nanocomposites to protect outdoors heritage buildings. Hence, novel Ag-TiO2/PDMS hydrophobic nanocomposites (with low doping rates) thin films with enhanced photo-response activity have been developed to be used as self-cleaning durable protective coatings in the field of monument conservation. The protective coatings elaborated in this work are intended to have multifunctional properties (water repellent features, self-cleaning activity, antimicrobial agent). To reach our objective, silver-doped titanium dioxide nanoparticles (Ag-TiO2 NPs) at different doping amounts (0.1, 1, 3, and 5 mol%) were firstly synthesized by the sol-gel method. As-prepared NPs were characterized and their performance was evaluated comparatively to find out the appropriate low doping rates of the dopant by testing photo-degradation as well as photo-killing activities. The second part of this research is focused on elaborating Ag-TiO2/PDMS hydrophobic nanocomposites (selected low doping rates) as self-cleaning protective coatings. For this purpose, Ag-doped TiO2 NPs were dispersed in a polymeric binder (polydimethylsiloxane, PDMS) and applied to the very porous stone substrate, i.e., Lecce stone (LS). The suitability of the resulting nanocomposites (optimal Ag doped TiO2 NPs/ binder ratio; optimal doping amount) on the stone substrate was evaluated by performing different experimental analyses: chromatic measurements, contact angle measurements, water capillary absorption test, permeability to water vapour, pencil and Vickers hardness tests, optical microscope analyses, and scanning electron microscopic analyses combined with energy-dispersive X-ray spectroscopy (SEM-EDS), microbiological experiments, and self-cleaning test. Moreover, the durability of the nanocomposite coatings was also assessed after exposing to different ageing cycles. Results suggested that the samples doped with low concentrations (≤1 mol%) of silver (Ag-doped TiO2) together with PDMS can be considered as efficient and durable protective coatings for the highly porous bio-calcarenite stone. Such doping amount is considered very low compared to the other research works that have been performed in the same field.

Lime-based Sacrificial Layers – Evaluation of a Traditional Conservation Method Applied in an Urban Environment

The use of modified lime slurry as a sacrificial layer to protect the original porous substrate has a long tradition in the practice of building and monument conservation in Austria. This paper presents the results of analyses performed on the Natural History Museum Vienna to get more insight into the long-term performance of this conservation method. Stone surfaces on the facade and roof area, covered with an acrylic tempered lime sacrificial layer and subsequently made water-repellent, were tested in situ and in the laboratory. Whilst coatings in the exposed zones were completely vanished in certain areas, the samples from the facade were in a good condition even after nearly twenty years of exposure. Hydrophobic activity could be verified up to a depth of five mm in the porous stone substrates. Despite the general good state of preservation of most surfaces, the existence of highly hydrophobic substrates will definitely restrict the implementation of any future sustainable conservation effort.

Natural biocides and bio-calcite: innovative tools for cultural heritage

Lithic artworks as churches, historical buildings and every usage object are our precious cultural heritage, memory of our past history step needed to build present and future. These artistic heritages with morphological, chemical and physical properties totally dissimilar make they a “unicum”, characterized by a specific vulnerability. Their decay is unavoidable, but it is a challenge for the humankind to protect and preserve them. Thus far, solutions for the safeguard of cultural heritage are usually based on chemical procedures to remove biodeteriogen agents, but these substances can be hazardous to the environment, to public health and to stone materials itself because it is not known about the consequences of repeated applications. Then the restoration methods require innovative approaches, eco-friendly and not harmful to human beings and the environment. Aiming at this objective a deeply study on two rupestrian churches located in Matera (Italy) was carried out in order to prevent and/or control microbial and biological evolution, and to exploit the potential of some bacterial species in the interventions of stone consolidation. Surface analyses of detached rocks to evaluate the (i) stone composition, (ii) isolation and characterization of biological and (iii) microbial colonizers present on the stone surfaces were formerly performed. In vitro bioactivity test against autotrophic/heterotrophic species isolated was carried out using secondary metabolites extracted from cultivated crops and spontaneous herbs with a strong biocidal activity (extracts from Solanum nigrum, Volutaria lippii, Moricandia arvensis, Pulicaria inuloides). Finally, calcinogenic activity tests employing native bacteria (Bacillus strains) isolated on stone surfaces of the two churches constitute the conclusive research step. Glycoalkaloids inhibited all bacterial strains tested. Some strains of Bacillus to produce the greatest amount of crystals, coherent with the stone substrate, was evidenced. This research highlights the opportunity to change the way of thinking and performing recovery actions for cultural heritage. Not last-minute remediation but continuous monitoring and time by time actions to avoid the formation of aggressive colonisations.

Efficiency evaluation of chemical and physical methods for the removal of spray paints from marble substrates

The graphic vandalism is considered one of the most important topics in the field of conservation of cultural heritage. The most widespread means used for the acts of vandalism are the felt-tip pens and the aerosol paints. These tools irreversibly damage the stone substrates, changing their appearance and conservation state. The aim of this article is to compare and characterize four different cleaning approaches in terms of their efficacy and invasiveness in the removal of the specific brand spray used as dirtying material.

Bacterial mineralization of calcium carbonate for conservation of stone artworks

Calcareous stones have been widely used as artwork and building materials by human civilizations, especially in the Mediterranean Basin. Calcareous stone deterioration is a consequence of the weathering action of physical, chemical and biological factors, which causes a progressive dissolution of the mineral matrix and an increase in porosity, resulting in the weakening of the structure. Recently, increased environmental pollution and global warming are threatening stone cultural heritage more than ever. Inorganic or organic products have been using to slow down monument deterioration, but their use presents several drawbacks. Bacterial Calcium Carbonate Mineralization is a natural process widespread among bacteria and occurring in different environments. In the last decades it has been proposed as a new and environmentally friendly tool in conservation of monumental and ornamental calcareous stones. The aim is to develop a bacteria-mediated mineralization treatment providing a coherent calcium carbonate layer on the surface of deteriorated stone, able to protect it against the intake of water and chemicals and to consolidate the inner weakening structure. The advantage is to obtain a mineral product similar to the calcareous stone substrate, mimicking the natural process responsible for stone formation. This review introduces the mechanisms of bacterial mineralization and describes the current strategies based on this process to promote stone reinforcement in field tests. They include applications of selected bacterial strains and/or culture media as well as selected components of bacterial cells on stone. The review finally provides perspectives based on recent advances.

Reducing susceptibility to moisture damage in asphalt pavements using polyethylene terephthalate and sodium montmorillonite clay

This study examines the feasibility of developing built-in resistance against moisture damage using either passivation or an arresting mechanism. A specific moisture-susceptible paving mixture with proven moisture-damage issues in the field was selected for this study. The damage was attributed to failure at the interface of bitumen and stone aggregate due to accumulation of acidic compounds at the interface with subsequent dissolution in the presence of water. Here, we examine two remedial methods. The first method introduces a polyethylene terephthalate based additive (PET) to bitumen to neutralize active sites of stones with concentrations of silica oxide greater than 50% (denoted simply as siliceous stones), suppressing nucleation and growth of acids at the interface. The second method introduces sodium montmorillonite clay (MMT) to adsorb acids and prevent their migration to the interface of stone and bitumen. Measurement of shear binding between siliceous substrates and bitumen using a shear rate sweep test showed increases of 21% and 43% due to the inclusion of MMT and PET, respectively. This improvement was also observed in the results of bitumen bond-strength tests performed on glass and on stone substrates. Results of the evaluation at the mixture level using a Hamburg wheel-tracking test showed that the addition of MMT and PET improved resistance to moisture damage, as evidenced by the increasing number of cycles before moisture stripping occurs. For the PET-modified mixture, no stripping inflection was observed until 20,000 cycles. It was also observed that MMT’s adsorption of acidic compounds from bitumen led to the appearance of surface dents after water conditioning. The PET-modified specimen showed some signs of color change after water exposure, without any signs of stripping. The study results help formulators design materials with built-in resistance mechanisms against moisture damage.