Crystallization Of Soluble Salts Research Articles

The Crystallization Effect of Sodium Sulfate on Some Italian Marbles, Calcarenites and Sandstones

Soluble salts are compounds found inside ornamental rocks and building stones exposed to atmospheric agents in environments rich in alkaline metal ions, such as sodium and potassium. The damage induced by their crystallization in those materials, used to build monuments and architectural structures of great importance, is an unsolved problem. Sodium sulfate is one of the most common and harmful salt found in these constructions. In this work, we studied the resistance through time to the wet-drying cycles of some natural stones (calcarenites, marbles, and sandstones) that have been utilized in the historical architecture in Italy. Samples were freshly cut and thermally aged to simulate increasing decay. Induced porosity in the thermally degraded samples was high in calcarenites, medium in marbles, and low in sandstones. Specimens subjected to artificial thermal aging lost a major percentage of mass compared to the non-weathered ones, when affected by the crystallization of soluble salts. With this study, we have observed that samples subjected to different wetting and drying cycles degrade faster due to the action of soluble salts, compared to samples that are not subjected to these cycles.

Investigation of a suitable porous stone for the restoration work on the Acropolis circuit wall

The present work describes the research that was carried out to define a suitable replacement or supplementary stone to use in the restoration work of the circuit wall of the Acropolis in Athens, Greece. The main original building material of the wall is known as Aktitis stone, originating from the ancient quarries of Piraeus, which are no longer accessible. Given the constant exposure to a combination of decay agents, the building materials of the Acropolis wall have begun to present various weathering patterns that gradually have reduced their mechanical properties. When the stability of the structure is threatened and it is not possible to use fresh stones of the same type as the original, it is necessary to use an alternative compatible replacement stone during the restoration. Therefore, an evaluation of eight porous stone samples originating from active quarries in Sitia (Crete), Afytos (Chalkidiki) and Pitsa (Corinthia) in Greece was carried out, through various methods, including determination of physical and moisture transfer properties, uniaxial compression strength tests and color parameter measurements. Moreover, to study the resistance of the samples in the crystallization of soluble salts, accelerated aging tests were performed in sodium sulfate cycles. A comparative evaluation is made between the quarry stones and the original, to draw conclusions about the appropriate materials for use in the upcoming interventions.

Effects of freeze-thaw cycles on the erodibility and microstructure of soda-saline loessal soil in Northeastern China

Soda-saline loessal soils are distributed extensively in the Songnen Plain of Northeast China. Freeze-thaw effects on soil structure and mechanical properties are becoming more frequent and intense with global warming, which further affects soil erosion in cold regions. Quantifying the effects of freeze-thaw cycles (FTCs) on the erodibility of saline soils is challenging because of the abundant soluble salt content and complex soil mechanical responses. In this study, direct shear tests, disintegration tests, and scanning electron microscopy were conducted to investigate the effects of freeze-thaw action on the erodibility indicators (shear strength and disintegration velocity) of soda-saline loessal soils and their microscopic deterioration mechanisms. Four initial moisture contents (IMCs: 8%, 13%, 18%, 23%), three soluble salt contents (SSCs: 0.5%, 1.0%, 1.5%), and six FTCs (0, 1, 3, 6, 10, 15) were considered. The results showed that successive FTCs continued to degrade the erosion resistance of the soil until it stabilized after approximately 10 FTCs. After 15 FTCs, the shear strength and cohesion decreased by 8.6–19.8% and 24.1–59.2%, respectively, while the angle of internal friction was relatively unaffected. Meanwhile, the soil disintegration velocity increased by 52.3–208.8%. During the freeze-thaw process, the water-ice phase change and the crystallization of soluble salts both led to the continuous adjustment of the microstructure of soda-saline loessal soils. It was found that microcracks within the soil structural units increased significantly, cementation between the structural units weakened continuously, pore connectivity was enhanced, and pore size homogenization increased. Correlation analysis showed that IMC was the fundamental factor affecting the soil mechanical properties, whereas SSC mainly affected the soil's resistance to disintegration. The increase in IMC and SSC exacerbated the deterioration of the soil by freeze-thaw action. This paper presents a new understanding of the erosion characteristics and micromechanisms of soda-saline loessal soils in seasonally frozen regions under freeze-thaw action.

Chemometrics and elemental mapping by portable LIBS to identify the impact of volcanogenic and non-volcanogenic degradation sources on the mural paintings of Pompeii

Crystallization of soluble salts is a common degradation phenomenon that threatens the mural paintings of Pompeii. There are many elements that contribute to the crystallization of salts on the walls of this archaeological site. Notably, the leachates of the pyroclastic materials ejected in 79 AD by Mount Vesuvius and local groundwater, rich in ions from the erosion of volcanic rocks. Both sources could contribute to increase the concentration of halides (fluorides and chlorides) and other salts in these walls. The distribution of volcanogenic salts and their impact on the conservation of Pompeian mural paintings have however not yet been fully disclosed. In this work, an analytical methodology useful to determine the impact of the main sources of degradation affecting the mural paintings of Pompeii is presented. This methodology combines the creation of qualitative distribution maps of the halogens (CaF and CaCl) and related alkali metals (Na and K) by portable Laser Induced Breakdown Spectroscopy (LIBS) and a subsequent Principal Component Analysis of these data. Such maps, together with the in-situ identification of sulfate salts by portable Raman spectroscopy, provided information about the migration and distribution of volcanogenic halides and the influence of ions coming from additional sources (marine aerosol and modern consolidation mortars). Additionally, the thermodynamic modeling developed using the experimentally determined ionic content of Pompeian rain- and groundwater allowed to determine their specific role in the formation of soluble salts in the mural paintings of Pompeii.

Characteristics and deterioration mechanisms in coral stones used in a historical monument in a saline environment

Information on properties and behavior of the ancient materials is critical in adopting appropriate strategies for preservation of historic monuments. Coral stones are materials with unique physical properties, and is common in ancient stone constructions. But these are not commonly in use in new buildings, and even quarrying of coral stones is banned in several island countries. However, considering the importance in heritage protection, there is a need to define their properties and performance. The current paper documents the condition and typical damage patterns of a coral stone heritage structure and analyses the physical, mechanical and chemical properties of the coral stone through in-situ and lab tests. The material properties and the microstructural details are examined to understand weathering of coral stone. The resistance of the material to salt crystallization was studied by performing sodium sulfate and sodium chloride immersion and drying cycles. Based on the results of the microstructural modifications seen on artificial salt weathering, the unique pore distribution system in the coral stones is found as the key for a higher resistance to crystallization of soluble salts. Erosion due to rain water and wind are concluded as the potential causes for the kind of damages observed.

An Inorganic Magnesium-based Consolidant for the Consolidation of Silica Sand (A Substitute for Weathered Sandstone): A Preliminary Exploration

ABSTRACT Sandstone is a common sedimentary rock that is easily carved due to its weakly cemented fine grains and relatively low strength. Therefore, numerous large-scale grottoes in China are made of sandstone. However, these sandstone cultural heritage structures are often seriously damaged due to temperature and humidity changes, air pollution, biodeterioration, and repeated dissolution and crystallization of soluble salts. In general, it is imperative that a consolidant capable of providing cohesion by infilling pores between the stone grains is synthesized. In recent years, it has been reported that using organic consolidation materials for sandstone protection comes with various negative effects, such as a short lifetime, poor compatibility, and preservation damage. Using inorganic consolidation materials to protect sandstone seems to be one of the research trends for the future. Herein, this paper introduces a permeable, inorganic magnesium-based material (MMH solution) for silica sand consolidation. To assess this consolidant, the paper investigates the influence of varying molar ratios of MgO:MgCl2·6H2O:H2O on properties such as penetration depth, consolidation weight, colour variation, and compressive strength. The results demonstrate that the molar ratios of MgO:MgCl2·6H2O:H2O can significantly affect the consolidation performance. Additionally, it is believed that the MMH solution of MgO:MgCl2·6H2O:H2O = 5:1:16 can be successfully used for the consolidation of silica sand, as the cubic specimens’ surface micrographs show good compatibility between the consolidation product and sand grains. Experiments (i.e. weight loss rate and mineralogical compositions analysis) are performed to evaluate the cubic specimens’ water resistance properties after being immersed in water. Furthermore, the consolidation material’s failure mechanism as a self-sacrificing material is preliminarily analyzed. Results indicate that MMH solution is a promising conservation material that shows great potential for consolidating severely weathered sandstone.

Decay of sandstone subjected to a combined action of repeated freezing–thawing and salt crystallization

The weathering of rocks controls the shape of the Earth’s surface and affects their suitability as building stones. Frost weathering and crystallization of soluble salts are considered to be important factors in rock weathering. Although the crystallization of salts and ice presents obvious chemical differences, both of them produce crystallization pressure. Few studies seem to have been done on the effects of the combined action of repeated freezing–thawing and salt crystallization on the rocks. This paper studies the weathering of rocks under the combined effect of freezing–thawing cycle and salt crystallization cycle. The results show that, with the increase of freeze–thaw cycles, the samples soaked with MgSO4 solution tend to turn red and the surface particles fall off more seriously. The mass of the sandstone is increased at the beginning of the freeze–thaw cycle and then decreases. Roughness, residual moisture, and MgSO4 crystal affect the thermal conductivity. Samples soaked with 40% MgSO4 solution lost the most mass and have the lowest thermal conductivity. There are two main factors that cause damage to sandstone: (1) crystallization pressure of salt and (2) frost heave action of ice. Crystallization pressure of salt and frost heave action of ice can reduce the cohesive force between particles, making the particles fall off, which is the most important factor of sandstone damage.

Combined wicking and drying of a NaCl solution in porous building materials

Salt weathering is a major cause of destruction of many valuable monuments. The salt damage of historical porous materials is mainly due to the crystallization of soluble salts due to drying. A special situation which occurs often in marine environments, the case where there is a permanent supply of sea water at one side of a material, whereas the other side is exposed to continuous drying in the open air. A well-known example is the historic city of Venice. Evaporation from the air exposed side provides a continuous moisture sink which is compensated by capillary suction, i.e., wicking of the sea water. As a result there will be a continuous flux of NaCl ions towards the surface. As soon as the concentration at the surface reaches the maximum solubility, crystallization will start which can give rise the damage. A simple analytic model was developed to describe this process. In order to verify this model non-destructive measurements were made of the moisture and ion transport during an experiment with limestone. In order to do so, we make use of a specially designed Nuclear Magnetic Resonance setup where we are able to measure quasi-simultaneously the 1H and 23Na content. Hence this method gives us the possibility for real-time monitoring of transport processes of the ions during experiments. It is seen that the concentration rise at the drying surface can be described by a simple analytic model.

Consolidation effectiveness of modified Si-based nanocomposites applied to limestones

One of the main issues in the field of Monument Protection is the degradation of limestones as a result of the action of various weathering mechanisms. The modification of widely used silicon-based materials for stone consolidation is intended to overcome the well-known drawbacks of these materials, such as shrinkage and cracking tendency during drying. The addition of nano-dispersions into a silica matrix aims to enhance their effectiveness in several ways, by improving their properties and their viscoelastic behavior. The objective of the current research was the application and evaluation of Si-based modified nanocomposites of optimized composition. The materials were applied to two types of porous stone and the assessment of their compatibility and performance was carried out by using both laboratory techniques and methods (SEM, MIP, TMA, Water Absorption by Capillarity, determination of Water Vapor Permeability) and non-destructive techniques (Ultrasound Velocity determination, Colorimetry). To study the resistance of the treated samples to soluble salt crystallization, accelerated aging tests were performed in sodium sulfate cycles. The modified consolidants consist of an ethyl silicate matrix reinforced with colloidal silica (SiO2) nano-particles and titania (TiO2) particles. Based on the results, the consolidating material does not significantly alter the characteristics of the microstructure and the appearance of stones, allowing the passage of water vapor, while increasing their mechanical properties. Furthermore, the accelerated ageing tests revealed that the treated samples have a higher resistance to the action and crystallization of soluble salts in comparison to untreated.

Effect of mixed in crystallization modifiers on the resistance of lime mortar against NaCl and Na2SO4 crystallization

Weathering of porous building materials caused by the crystallization of soluble salts is a ubiquitous problem in the built cultural heritage. Especially lime-based mortars are susceptible to salt decay, due to both their bimodal pore size distribution and low mechanical strength. The addition of crystallization modifiers to mortars during mixing may confer them an improved resistance to salt decay. In this research, lime-based mortars additivated with ferrocyanide or borax (modifiers for sodium chloride and sodium sulfate, respectively) were prepared. An accelerated salt crystallization test was carried out to assess the effect of the modifiers on the salt resistance of the mortars. The development of damage was assessed by visual and photographical observations and by quantifying the salt and material loss. At the end of the test, SEM observations were performed on the surface and cross-section of the specimens, to study the effect of the modifiers on the crystallization habit of the salts. The ferrocyanide and borax additivated mortars showed a considerably improved durability with respect to salt crystallization damage. Both modifiers altered the growth morphology of the salt crystals inside the pores of the mortars.

Ghaleh-khargushi rhyodacite and Gorid andesite from Iran: characterization, uses, and durability

Durability of building stones is an important issue in sustainable development. Crystallization of soluble salts is recognized as one of the most destructive weathering agents of building stones. For this reason, durability of Ghaleh-khargushi rhyodacite and Gorid andesite from Iran was investigated against sodium sulfate crystallization aging test. Petrographic and physico-mechanical properties and pore size distribution of these stones were examined before and after the aging test. The characteristics of the microcracks were quantified with fluorescence-impregnated thin sections. Durability and physico-mechanical characteristics of Ghaleh-khargushi rhyodacite are mainly influenced by preferentially oriented preexisting microcracks. Stress induced by salt crystallization led to the widening of preexisting microcracks in Ghaleh-khargushi rhyodacite, as confirmed by the pore size distributions before and after the aging test. The preexisting microcracks of Gorid andesite were attributed to the mechanical stress induced by contraction of lava during cooling. The number of transcrystalline microcracks was significantly increased after the aging test. The degree of plagioclase microcracking was proportional to its size. Durability of the studied stones depends on initial physico-mechanical properties, pore size distribution, and orientation of microcracks. Initial effective porosity is found to be a good indicator of the stones’ durability. Salt crystallization resulted in an increase in the effective porosity with a parallel decrease in the wave velocities. Surface microroughness parameters increased with the development of salt crystallization-induced microcracking. Gorid andesite showed higher quality and durability than Ghaleh-khargushi rhyodacite.

Exposure Factors Influence Stone Deterioration by Crystallization of Soluble Salts

The present work tries to determine the factors that influence the crystallization of soluble salts in the stone material used in the construction of buildings in Valencia (Spain). Samples are obtained from a building which has served to accomplish observations and laboratory experiments necessary in order to determine the pathology of deterioration of the material. It was particularized in the exposition conditions of the material as a base for determining the morphologies of deterioration caused by salts in the same lithotype. The main contribution is the petrological study from the architectural point of view considering its orientation, sunlight in façade, and so forth. This study proves that both material petrology (its mineralogy and texture) and the properties related to the movement of water inside rocks play a decisive role in the conservation and development of elements in the alteration.

Control of Crystal Nucleation and Growth by Additives

Research Article| June 01, 2013 Control of Crystal Nucleation and Growth by Additives Carlos Rodriguez-Navarro; Carlos Rodriguez-Navarro 1Department of Mineralogy and Petrology, University of GranadaFuentenueva s/n, 18002 Granada, SpainE-mail: carlosrn@ugr.es Search for other works by this author on: GSW Google Scholar Liane G. Benning Liane G. Benning 2School of Earth and Environment, University of LeedsLeeds, LS2 9JT, United KingdomE-mail: L.G.Benning@leeds.ac.uk Search for other works by this author on: GSW Google Scholar Elements (2013) 9 (3): 203–209. https://doi.org/10.2113/gselements.9.3.203 Article history first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Carlos Rodriguez-Navarro, Liane G. Benning; Control of Crystal Nucleation and Growth by Additives. Elements 2013;; 9 (3): 203–209. doi: https://doi.org/10.2113/gselements.9.3.203 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyElements Search Advanced Search Abstract The survival of important pieces of our architectural and sculptural heritage is challenged by irreparable damage due to crystallization of soluble salts. Mineral precipitation is also a problem in many industrial processes, leading to costly scale formation. Most of the mechanisms that control these crystallization reactions can be modified or slowed down by using specific additives. Recent advances in elucidating the mechanisms of mineral nucleation and growth and molecular-level mineral–additive interactions have led to the development of novel treatments for the prevention of mineral scale and salt damage. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Salt Degradation in Stone of Old Buildings

The crystallization of soluble salts is a major mechanism of degradation of some building materials, including stone. This mechanism of deterioration is based on the pressure exerted by the formation of salt structures in porous materials, with increased volume and is dependent on the type of salts involved and the size and arrangement of pores. When the pressure exceeds the internal strength of the material, and particularly when the salt formations undergo cycles of crystallization and dissolution in response to fluctuating levels of humidity, the deterioration of materials typically becomes apparent. It is therefore essential to understand the phenomenon of crystallization and dissolution of salts, i.e., to know the conditions of crystallization of each salt, depending on relative humidity and air temperature. For this purpose we developed an experimental work, using four samples of stone (one limestone and three granites), which consists, initially, to study the variation of the water absorption coefficient with and without soluble salts.

The Effect of Composition of Roman Cement Repair Mortars on Their Salt Crystallization Resistance and Adhesion

Crystallization of soluble salts in porous networks is a major source of decay for mortars used in historical buildings. The optimum formulation and application of Roman cement mortars which could produce compatible and durable repairs of the original substrates was studied. Measurements were performed with the aim of determining the pore size distribution, the hydric parameters as well as the salt crystallization resistance of the mortars. The adhesive strength of the repair materials laid on historic substrates was also determined. The results of the crystallization tests show that repair Roman cement mortars with hydric parameters close to those of the historic substrates, though different pore size distributions, have related salt crystallization resistance.

Short-term and long-term maturation of different clays for pelotherapy in an alkaline-sulphate mineral water (Rapolla, Italy)

This study investigated in detail the mineralogical changes within 8 little maturation ponds filled with different clay materials placed in a spa center in southern Italy and kept under the traditional environmental conditions used by the spa itself. Both short- and long-term maturation periods were investigated. Several changes were observed in all the samples during the first month of maturation and also in the following 2 months. A significant increase in soluble Na occurred in all the samples. No significant variations in the initial mineral assemblage were detectable either in the bulk material and or in the clay fraction except for the crystallization of neoformed Na-minerals. The amount and the type of silicate minerals did not change in time, but the position and the width of the basal reflection of expansible minerals changed due to a gradual incorporation of new ions into the interlayer space. During the first month a variation in the grain-size distribution as well as a decrease in calcareous nannofossils can be observed. A slight increase in Corg was also recorded during the maturation. Some of the parameters which were more sensitive to short maturation continued to adjust also during a fairly longer time such as 15 months. The spacing and the FWHM of the basal reflection of smectite and mixed layers minerals and the crystallization of soluble salts were good monitors of long-term maturation. There were two tracks in the maturation period and were related to particular indicators. Typical indicators of this “first track”, mainly between months 1 and 2 of maturation were the grain size, the calcareous nannofossils and the amount and the type of exchangeable cations. The salt crystallization can be considered a suitable indication of the “second track” of maturation within 6–9 months.

Nondestructive Investigation of Wet Building Material: Multimethodical Approach

Building stones are porous media and they can deteriorate through moisture ingress and secondary damage such as crystallization of soluble salts. Not only is this due to the increasing number of flood events in the past years but also structural damages of houses from activity such as leakage or rising moisture (groundwater) are the main causes. The potential benefit of several nondestructive testing methods to assess water damage in building stone has been studied in a field-scale experiment. Three testing walls made of fired clay brick, sandstone, and spongilite were flooded and their drying behavior monitored using infrared thermography, complex resistivity, ground penetrating radar, and ultrasonics. The results were compared to the average moisture content determined by gravimetric weighing of the specimens. Qualitatively, the results of the different nondestructive testing methods matched well. But in terms of quantitative data, some scatter was observed and the results should be viewed with care. Co...

Physical principles and efficiency of salt extraction by poulticing

The crystallization of soluble salts plays a significant role in the deterioration of porous cultural property. A common response to salt damage problems is to undertake treatments aimed at reducing the salt content of the affected object, most typically through the application of poultices. The process of poulticing is in theory relatively simple: the wet poultice material is applied to the surface of the object to be treated, and is kept in place for some period of time before being removed. However, in practice, the efficiency of the salt extraction, or even the location of salt accumulation post treatment is more difficult to predict. This paper examines the physical principles of salt ion and moisture transport by which poultices function, and shows how depending on the application methodology, these treatments can be divided into diffusion and advection-based methods. The maximum salt extraction efficiency, the depth to which this can be achieved, and the time scale required is estimated for each type of poulticing system, to gain a better understanding of their working properties and performance. Finally, the pros, cons and limitations of desalination treatments are discussed.

Incorporação de resíduo do tratamento de drenagem ácida em massa de cerâmica vermelha

Neste trabalho, apresenta-se o estudo experimental em escala laboratorial e industrial da incorporação de resíduo do tratamento de Drenagem Ácida de Mina (DAM) na formulação de massa de cerâmica vermelha, com substituição parcial das argilas. Foram realizados algumas análises e ensaios nas amostras dos blocos cerâmicos: análise dilatométrica a verde, absorção de água, resistência à compressão, eflorescência de sais solúveis e emissões atmosféricas (MP e SOx). Os resultados das análises nos corpos de prova ensaiados indicam aumento de resistência a compressão. Os ensaios de eflorescência de sais solúveis indicam maior intensidade de cristalização de sais solúveis na superfície dos corpos de prova e blocos cerâmicos à medida que se aumenta o percentual de resíduo. As análises realizadas nos blocos cerâmicos ensaiados em escala industrial, recomendam uma proporção de até 2,5% de resíduo na massa cerâmica.

Prevention of Salt Damage to Monuments: Esem and Time-Lapse Studies

Introduction: “In time, and with water, everything changes.” —Leonardo da Vinci The crystallization of soluble salts in porous building materials is a widespread weathering process that results in damage to important monuments and archaeological sites. Salt weathering by thenardite (sodium sulfate) and mirabilite (sodium sulfate decahydrate) is especially destructive, yet is still not fully understood. Halite (sodium chloride) in contrast, is one of the least damaging salts. Previous work has also demonstrated the importance of airflow in salt weathering. Here we present new data that help explain why sodium sulfate is so damaging and also show how crystallization modifiers and changes in airflow can reduce salt damage in laboratory experiments.Damage Mechanism: The behavior of sodium sulfate was documented using saturated solutions and oolites from Monks Park limestone (a stone well known to be vulnerable to salt damage) as test samples. Damage was evaluated based on the degree of cracking of the oolite.