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The crystallisation of soluble salts within the pores of the stone is widely recognised as a major mechanism causing the deterioration
of the stone-built architectural heritage. Temperature, in turn, is one of the main controls on this process, including salt
precipitation, the pressure of crystallisation and the thermal expansion of salts. Most laboratory experiments on decay generated
by salts are just carried out with convective heating regimes, while in natural environments building stones can undergo radiative
and convective heating regimes. The thermal response of stone to these different heating regimes is noticeably different and
might influence the crystallisation patterns of a salt within a stone. The aim of this work is to raise awareness on the different
patterns of crystallisation of NaCl within a porous stone tested with different heating regimes (convection and radiation)
and the implications that this could have on the design of experimental modelling of natural weathering conditions in laboratory
simulations. Results show that heating regime affects the sodium chloride distribution within a stone with high percentage
of microporosity. In this case, radiation heating facilitates the generation of subefflorescences, while convection heating
promotes efflorescences. This has a clear implication both on the stone decay in natural environments and on the methodologies
for testing salt decay, as subefflorescences are more destructive than efflorescences. In this sense, the use of convective
heating in laboratory experimentation might underestimate the potential damage that sodium chloride may generate. This counsels
the use of radiation heating test methods in addition to convection for the laboratory study of salt crystallisation. 相似文献
3.
D. Benavente J. Martinez-Martinez N. Cueto S. Ordoñez M. A. Garcia-del-Cura 《Environmental Earth Sciences》2018,77(4):147
This study aims to understand the effect of salt and frost crystallisation on the petrophysical and durability properties of representative types of travertine and carbonate tufas. Results demonstrate that the studied travertines and tufas exhibit a very high durability against salt and ice crystallisation cycles, compared to carbonates rocks with similar porosity values. The variation of the loss of mass, effective porosity, capillary absorption coefficient, ultrasonic wave velocity and attenuation, and compressive strength was scarce during weathering tests. The evolution of petrophysical properties was slightly more intense after 30 cycles of salt crystallisation than 100 cycles of freeze–thaw. Petrophysical and durability properties of the travertines and carbonate tufas depend on porosity fraction and on the manner in which the vuggy porosity is connected. In the travertine facies, vuggy macropores show little connection and can be considered as separate-vug porosity. Their addition to interparticle porosity increases effective porosity and reduces their mechanical strength but does not significantly increase capillary transport and the effectiveness of salt and ice action over the stone. On the contrary, in the carbonate tufas, vugs act as touching-vug pores, as capillary imbibition coefficients reveal. However, scanning electron microscopy displays that they underwent microcracking processes related mainly to both thermal stresses and/or ice and salt pressures. These microcracks present little connection, and they do not enhance noticeably the water flow or decrease the mechanical properties. These results are finally discussed in terms of a nonlinear decay pattern, which with long periods of apparent stability might be followed by rapid and catastrophic decay. 相似文献
4.
S. McCabe B. J. Smith J. J. McAlister M. Gomez-Heras D. McAllister P. A. Warke J. M. Curran P. A. M. Basheer 《Environmental Earth Sciences》2013,69(4):1225-1235
Salt weathering is a crucial process that brings about a change in stone, from the scale of landscapes to stone outcrops and natural building stone façades. It is acknowledged that salt weathering is controlled by fluctuations in temperature and moisture, where repeated oscillations in these parameters can cause re-crystallisation, hydration/de-hydration of salts, bringing about stone surface loss in the form of, for example, granular disaggregation, scaling, and multiple flaking. However, this ‘traditional’ view of how salt weathering proceeds may need to be re-evaluated in the light of current and future climatic trends. Indeed, there is considerable scope for the investigation of consequences of climate change on geomorphological processes in general. Building on contemporary research on the ‘deep wetting’ of natural building stones, it is proposed that (as stone may be wetter for longer), ion diffusion may become a more prominent mechanism for the mixing of molecular constituents, and a shift in focus from physical damage to chemical change is suggested. Data from ion diffusion cell experiments are presented for three different sandstone types, demonstrating that salts may diffuse through porous stone relatively rapidly (in comparison to, for example, dense concrete). Pore water from stones undergoing diffusion experiments was extracted and analysed. Factors controlling ion diffusion relating to ‘time of wetness’ within stones are discussed, (continued saturation, connectivity of pores, mineralogy, behaviour of salts, sedimentary structure), and potential changes in system dynamics as a result of climate change are addressed. System inputs may change in terms of increased moisture input, translating into a greater depth of wetting front. Salts are likely to be ‘stored’ differently in stones, with salt being in solution for longer periods (during prolonged winter wetness). This has myriad implications in terms of the movement of ions by diffusion and the potential for chemical change in the stone (especially in more mobile constituents), leading to a weakening of the stone matrix/grain boundary cementing. The ‘output’ may be mobilisation and precipitation of elements leading to, for example, uneven cementing in the stone. This reduced strength of the stone, or compromised ability of the stone to absorb stress, is likely to make crystallisation a more efficacious mechanism of decay when it does occur. Thus, a delay in the onset of crystallisation while stonework is wet does not preclude exaggerated or accelerated material loss when it finally happens. 相似文献
5.
Building stone of Anahita Temple seriously suffers from weathering due to long term freezing-thawing and salt crystallization processes. This article investigates possible changes of physical and mechanical characteristics of this stone subjected to freeze–thaw and salt crystallization ageing tests. Fresh samples obtained from the Chelmaran quarry (the main quarry supplying for Anahita Temple stone) were tested under freeze–thaw and salt crystallization experiments. The freeze–thaw and sodium sulfate salt crystallization are suggested to be the most effective factors affecting in apparent deterioration of the stone in compare to the magnesium sulfate salt crystallization test. Significant decreases in mechanical properties of the stone were observed after freeze–thaw and salt crystallization tests. However, more mechanical losses were recorded after the salt crystallization cycles than the freeze–thaw cycles. This is probably due to crystallization pressure of salt crystals in compare to ice wedging force, which promoted more development of micro-fractures in the specimens. Probably, intrinsic factors of the stone such as frequent calcite veins and stylolites, are the main factors that control the durability of Anahita Temple stone. Preferential weakening along these features during freeze–thaw and salt crystallization cycles led to physical destruction and strength loss of the stone. Based on comparison between experimentally induced damages and field observations, reasonably freeze–thaw process is major factor in weathering of Anahita Temple stone. It should be noted that recorded 102 frozen days for the region imply high destruction potential of the stone during freeze–thaw cycles. 相似文献
6.
Ali Bahad?r Yavuz 《Environmental Earth Sciences》2012,67(7):1909-1925
Ala?at? tuff has been used extensively as a source of building stone for outdoor and indoor decorations since the historical times in and around the tourist town of Ala?at? (western Turkey). The use of the Alacati tuff in buildings has been made compulsory by the Ala?at? municipality, for preserving the historical appearance of the buildings, after 2005 in Ala?at?. It has been noticed that, evident deteriorations developed in tuff surfaces of the stone buildings and garden walls within 5?C6?years of their emplacement. Durability properties of the Ala?at? tuff are evaluated by determining the mineralogical, chemical, and physico-mechanical properties of the fresh tuff samples obtained from the only operative quarry in the area. Ageing tests such as Na2SO4 and MgSO4 salt crystallization, freezing?Cthawing, and wetting?Cdrying were conducted on the fresh tuff samples to assess their durability. Additionally, the durability of the tuff is also evaluated by determining its average pore diameter, saturation coefficient, wet-to-dry strength ratio, static rock and slake-durability indices. Fresh Ala?at? tuff has high porosity and low unit weight and strengths and are classified to be very poor to moderately durable stone based on the test results of different durability assessment methods. Mineralogical and geochemical analyses have also been carried out on the deteriorated tuff samples collected from the surfaces of the stone buildings to determine the effect of weathering on tuff and the test results have been compared with those of the fresh tuff samples. There is no major difference observed between the mineralogy and chemistry of the fresh and weathered tuff samples thus, it has been concluded that physical weathering has been dominant in the area in deterioration of tuff. 相似文献
7.
The influence of petrophysical properties on the salt weathering of porous building rocks 总被引：1，自引：0，他引：1
D. Benavente N. Cueto J. Martínez-Martínez M. A. García del Cura J. C. Cañaveras 《Environmental Geology》2007,52(2):215-224
The influence of pore structure, water transport properties and rock strength on salt weathering is evaluated by means of
a thorough rock characterisation and a statistical analysis. The pore structure was described in terms of its porosity, pore
size distribution (quantified by mean pore radius) and specific surface area, density and water transport was characterised
by means of water permeability (saturated flow) and capillary imbibition (unsaturated flow); whilst the rock strength test
was carried out using uniaxial compressive strength, compressional and shear wave velocities, dynamic elastic constants and
waveform energy and attenuation were obtained from the digital analysis of the transmitted signal. A principal component analysis
and a stepwise multiple regression model was carried out in order to examine the direct relationships between salt weathering
and petrophysical properties. From the principal component analysis, two main components were obtained and assigned a petrophysical
meaning. The first component is mostly linked to mechanical properties, porosity and density whereas the second component
is associated with the water transport and pore structure. Salt weathering, quantified by the percentage of weight loss after
salt crystallisation, was included in both principal components, showing its dependence on their petrophysical properties.
The stepwise multiple regression analysis found that rock strength has a predominant statistical weight in the prediction
of salt weathering, with a minor contribution of water transport and pore structure parameters. 相似文献
8.
Investigation of the weathering and weatherability of three types of igneous rocks (granite, nepheline syenite and lamprophyric-minette dyke) was carried out by means of laboratory tests.For this purpose an experimental device was developed to obtain hot conditions alternating with room temperature and also with wet conditions, by immersion in two types of liquids (distilled water and a solution simulating “seawater”).Beyond qualitative effects emphasized in the text and in a photographic documentary, some quantitative determinations were made (weight loss and chemical decay of main cations of rock-minerals), which enable the authors to present an attempt at an alterability index for classification of the rocks. The research-program outlined on quantitative determinations is suitable for application in problems of engineering geology such as in determining suitability of rocks for use as breakwater stone or riprap for dams or in the stone deterioration measurements of the deterioration of stone used for buildings and ornamental facing stones. 相似文献
9.
C. Thomachot-Schneider M. Gommeaux G. Fronteau C. T. Oguchi S. Eyssautier B. Kartheuser 《Environmental Earth Sciences》2011,63(7-8):1447-1461
The Orval Abbey, a major monument of southern Wallonia, Belgium, was partly destroyed and rebuilt several times between the Middle Ages and the present time. The oldest parts are made of natural stones of local origin (Bajocian and Sinemurian limestones) and the most recent parts are mostly made of reconstituted stone. The process of reconstituted stone making is not known. Although confronting the same environmental conditions, the reconstituted stone is much more susceptible to weathering than the natural limestones, especially to salt crystallisation. The present study compared the mineralogical and petrophysical properties of these building materials to gather information on the making of the reconstituted stone and to understand the difference in salt susceptibility between natural and reconstituted stones. Microscopic observations and petrophysical measurements showed that the reconstituted stone is composed of debris of Sinemurian and Bajocian limestone and cement, and the salt efflorescences were thenardite. Within the cement, amorphous grains were found that may correspond to grains of clinker, which have not reacted during stone making. Although its porosity and water transfer properties were close to that of the Bajocian limestone, its pore access distribution was centred around 0.1 μm. Furthermore, the details of the pore size distribution allowed calculating salt susceptibility indices that were very high in the case of the reconstituted stone. Thus, the composition of the cement and the pore size distribution are likely the two factors explaining a high susceptibility of the reconstituted stone to salt weathering. 相似文献
10.
Salt crystallisation is a major problem of deterioration in historic stone buildings, monuments and sculptures. The capillary rise of soil water is one of the primary sources of salts in stone structures, which evaporates leaving the salts behind. It has been noted that the spatial distribution profile of different species of salts crystallised in historic stone buildings is not homogeneous, i.e. different salts crystallise at different locations. The capillary transport and inhomogeneous spatial distribution of different salts in the porous building materials has been considered to be a result of solubility-dependent crystallisation; however, the factors responsible for this phenomenon are not clearly known. This paper aims to investigate the factors influencing the differential distribution of salts during capillary rise of soil water. In this study, the capillary transport of salts was simulated on two different sandstones—Locharbriggs, a Permo–Triassic, red sandstone and Stoke Hall, a Carboniferous, buff sandstone. The experiments were carried out under controlled environmental conditions to eliminate the possibility of evaporation-driven crystallisation of salts depending on their solubilities. The results indicate that fractionation or differential distribution of salts takes place even in the absence of evaporation and crystallisation. The sandstones exhibit properties like an ion exchange column, and ionic species present in the salt solution show differential distribution within the porous network of sandstone. 相似文献
11.
The Early Christian Munazio Ireneo cubicle in Cagliari (Sardinia) is carved into the rock and is one of the rare monuments of Sardinia belonging to Early Christian Age. It is 166 cm under the planking level and is a semi-confined chamber in which a gate allows exchange with the outside. In 1888, when it was discovered, it was completely painted, but over the years, it suffered a serious damage and all the paintings are nearly disappeared. Now the site shows a high moisture and a differential damage characterised by delamination, powdering, salt crystallisation and biological colonisation. The research offers a multidisciplinary approach to study the salt crystallisation damage, which is a phenomenon still not completely understood today. Studies and analyses highlight that different kinds of damage can be recognised. The cement mortar and the air pollution cause crystallisation of the sulphates. Constant capillary rising and the presence of water infiltration due to the rains, which travelled into the site from the vault, were detected during qualitative inspection. Although the microclimate did not change much in the site and the humidity was almost constant during the monitoring period, the variations in temperature allowed the phase transitions of sodium sulphate, especially in summer. The greatest damage of the porous stone is associated with the phase transitions and crystallisation inside the stone of sodium sulphate, one of the most harmful salts for porous materials because of its high crystallisation pressure. 相似文献
12.
M. Ahmad M. K. Ansari Rajesh Singh L. K. Sharma T. N. Singh 《Geotechnical and Geological Engineering》2017,35(2):827-842
Weathering and durability are the key factors of the rock in the suitability and usefulness of different construction materials, building materials and engineering structures. A single test never predicts the entire factor for suitability of rock stone and aggregate in different uses. Thus, variety of physical, mechanical and chemical tests and indices of rocks are widely used to estimate and evaluate the rocks for the suitability of the required purpose. In all the cases, knowledge of durability and weathering properties are the most important along with the strength of the rock. Micropetrographic index and rock durability indicators (dynamic and static) are the one of the best methods to evaluate the rock for weathering and durability. To estimate these indices, variety of tests are performed such as petrographic examination test, point load index, sulfate soundness test, water absorption test, modified aggregate impact value test and test for specific gravity. Slake durability index and impact strength index tests were also performed for correlation with static and dynamic rock durability indicators due to its application and usefulness in the durability and strength of the rock materials. Micropetrographic index was obtained by petrographic examination test and correlated with all the physical and mechanical properties used for find out the durability indicators. The present study is to express the usefulness of these three indices in the classification of weathering and durability classes and estimation of durability indices by slake durability index, impact strength index and micropetrographic index. 相似文献
13.
An integrated database and geographical information system (GIS) for the recording and monitoring of stone degradation are outlined. GIS requirements for stone degradation are summarized and a simple classification system for weathering forms identified and applied. The potential use of the system for identifying change in weathering forms using historic imagery is illustrated using an example from Oxford. Combining information from imagery of different buildings at different time periods, it is possible to put forward a possible scenario of weathering form evolution. 相似文献
14.
Deterioration mechanisms of tuffs in Midas monument 总被引：3，自引：0，他引：3
Slightly weathered white and pink tuffs of the Midas monument have deterioration problems. In this study, depths and characteristics of the weathering zones developed within the tuffs are investigated through optical microscopy, X-ray diffractometry (XRD), chemical analyses, scanning electron microscopy (SEM) and some index parameters. Accelerated weathering tests including wetting–drying, freezing–thawing and salt crystallization are performed, and durability assessment methods are used to predict the durabilities of the tuffs. The findings are compared with field observations. By examining quantitative weathering indices and comparing them with thin section studies, it is found that thin section analyses of the crystals, LoI, and WPI are good indicators to quantify the depth of weathering for the tuffs. However, thin section studies have limited value for fine-grained tuffaceous matrix. The chemical weathering of the tuffs produces weathered zones that are 4.5-cm thick within the white tuff and 2.5-cm thick within the pink tuff. Physical weathering causes scaling of outer layers of the tuffs and fracturing of feldspars along their cleavage planes. However, variations of the index properties of the tuffs due to weathering are not so significant to quantify the weathering depths in the tuffs. Among the accelerated weathering tests, salt crystallization is found to be the most destructive environmental condition. Pigeon droppings rich in NO31− are found to be the main source of soluble salt at the Midas monument. The salt transported up by capillary rise due to surface water causes spalling of the tuffs in the capillary zone. Surface water and salt of any kind in the close vicinity of the monument should be totally eliminated for the purpose of conservation. Field observations and the durability equations reveal that the white tuff is less durable than the pink tuff. Wet-to-dry strength ratio yields a better stone durability assessment among various durability methods used in this study. 相似文献
15.
Two of the most popular weathering tests used for dimension stone are EN 12371 freeze–thaw (FT) and EN 12370 Salt Crystallization (SC). These tests are used to assign a durability value to the rocks. Both tests are based on the cyclical growth of crystals in the porous system of the rock, which causes structural stress on the rock matrix that may affect its integrity. The weathering mechanism is the same in both tests although the rate of volume increase is higher for the salt crystals. Due to this similarity, the two tests provide complementary information. The EN (European Norms) recommend evaluating the results together, but do not establish correlations between the results of these two tests for different types of rocks. Knowing these relationships would improve the understanding of the results and the response to weathering of the rock once placed in a building. In this work, several ornamental rocks (sandstones, limestones, dolostones, and a travertine) from the Iberian Peninsula were submitted to FT and SC tests. Rocks were mineralogically and petrographically characterized, and their porous systems were defined by a combination of techniques (scanning electronic microscopy, digital images analysis, and mercury porosimetry). The results of the tests were quantified numerically to compare them. The velocity of propagation of ultrasonic waves was measured before and after the tests. After the statistical analysis, significant correlations were found between the FT and SC tests, and between the connected porosity and the durability index of the rocks. 相似文献
16.
The role of saline solution properties on porous limestone salt weathering by magnesium and sodium sulfates 总被引：4，自引：0，他引：4
Saline solution properties, viscosity in particular, are shown to be critical in salt weathering associated with sodium and
magnesium sulfate crystallization in porous limestone. The crystallization of sodium and magnesium sulfate within a porous
limestone has been studied at a macro- and microscale using different techniques, including mercury intrusion porosimetry,
environmental scanning microscopy and X-ray computed tomography. Such analysis enabled the visualization of the crystallization
process in situ, and at high magnification, yielding critical information as to where and how salts crystallize. Sodium sulfate
decahydrate (mirabilite) tends to crystallize in large pores as euhedral micron-sized crystals formed at low supersaturation
near to the surface of the stone. In contrast, magnesium sulfate heptahydrate (epsomite) tends to precipitate as anhedral
wax-like aggregates formed at high supersaturation and distributed homogeneously throughout the stone pore system filling
large and small pores. While the former crystallization behavior resulted in scale formation, the latter led to crack development
throughout the bulk stone. Ultimately, the contrasting weathering behavior of the two sulfates is explained by considering
differences in flow dynamics of solutions within porous materials that are mainly connected with the higher viscosity of magnesium
sulfate saturated solution (7.27 cP) when compared with sodium sulfate saturated solution (1.83 cP). On the basis of such
results, new ways to tackle salt weathering, particularly in the field of cultural heritage conservation, are discussed. 相似文献
17.
The salt mist present in the coastal shoreline constitutes an important weathering agent of the building materials applied in these regions. Portugal has an extensive coastline, which has a high population density. It holds a long tradition in the use of stone as a building material, due to the abundance of this natural resource, but also because of its durability and beauty. Considering the main ornamental stones mined in Portugal, limestones are the most susceptible to the action of saline atmospheric aerosol, because, in most cases, they present open porosities higher than those of other stone types. This feature facilitates the penetration of saline aerosol in their structures. Six widely applied Portuguese limestones, with different technological properties, were selected for this study. After accessing their petrographic and main technological features, the limestones were submitted to salt mist test. The test method, established in the respective European standard, was complemented with further determinations (variation on water absorption and flexural strength after salt mist cycling). The results allowed evaluating the limestones’ suitability for the main types of applications and for specific usage conditions, within each one. Thus, it was possible to set the recommended uses for each limestone, in order to maximize its durability. Salt mist testing made possible to determine the limestones’ resistance to the climatic conditions of coastal areas. The detailed analysis of the salt mist results strengthens the knowledge that the open porosity plays a decisive role in the limestones’ behaviour to this test. 相似文献
18.
The investigated rock material belongs to the group of upper cretaceous quader sandstones which are very important construction stones in Poland and Germany. The mineral composition of the rocks is relatively uniform??they are quartzose sandstones. The most important feature is their good workability and comparatively high weathering resistance. Still, regardless of the apparent resemblance, the observations carried on buildings and monuments show differences in weathering processes. The undertaken test was an attempt to verify the proposed before rock classification, performed on the basis of parameterization of porosimetric cumulative intrusion volume curves. The aim of the experiment was the evaluation of the sandstone petrography (including the structure, texture and porosity of the rock) influence on the weathering process. The modelling of accelerated weathering was conducted in Chamber for Ageing Acceleration, where some weather circumstances were simulated (insolation, rain and frost). As the result of the weathering experiment it could be stated that the dominant mechanism of the sandstones deterioration was granular disintegration and weight loss as a consequence of sample destruction. The most important factor influencing rock deterioration is rock texture, especially the character of grain contacts. The effective porosity is a requisite of potential for the stone to take in and hold water, and hence of resistance to weathering. In case of silica-cemented sandstones, the deciding criterion influencing weathering resistance is pore structure. In case of sandstones with clay cement, the most important is mineral composition of the rock. 相似文献
19.
Black crusts are very common on limestones in polluted urban environments, but white crusts are less frequently developed. On the soft, porous and inherently weak oolitic limestone of Budapest both crusts are frequent, and indeed white ones are more common on the stone walls of the studied fortress. In this paper, black and white crusts and the host rock have been described using morphological criteria, mineralogical analyses (XRD, DTA), elements analyses (microprobe) and micro-morphological (SEM) tests. The analyses have shown that on white crusts the surface dissolution is combined with the precipitation of gypsum and calcite in the pores and accumulation of gypsum on the underside of the crust. Thin white crusts are removed by a combination of salt crystallisation (gypsum) and frost action while very thick stone layers scale off due to freeze-thaw cycles. Black crusts are enriched in gypsum relative to white crusts. Gypsum accumulates on the crust surface and signs of dissolution have not been observed. Airborne particulates (flyash, silt-sized quartz, and organic debris) adhere to the crust surface of sheltered black crusts. These particles are later incorporated into the expanding gypsum crystals, that are visible on the underside of the crust. The host rock also contains gypsum, but it is washed off the surface when the crust is removed. Further exposure of the host rock may lead to the dissolution of calcite crystals as it is observed by SEM. The micro-environment influences the crust formation and adherence of the crusts. On frequently wet and dry surfaces crust removal is more common. The crust serves as a protective layer on the stone surface, but this protection is temporary since trigger mechanisms such as salt crystallisation or frost action can cause rapid surface loss.Special Issue: Stone decay hazards 相似文献
20.
Salt and ice crystallisation in porous sandstones 总被引：1，自引：0，他引：1
Salt and ice crystallisation in the pore spaces causes major physical damage to natural building stones. The damaging effect
of these processes can be traced back to physically induced stress inside of the rock while crystallizing. The increasing
scientific research done during the past century has shown that there are numerous parameters that have an influence on the
weathering resulting from these processes. However, the working mechanisms of the stress development within the rock and its
material dependency are still subject to discussion. This article gives an overview of salt and ice weathering. Additionally,
laboratory results of various sandstones examined are presented. Salt crystallisation tests and freeze/thaw tests were done
to obtain information about how crystallisation weathering depends on material characteristics such as pore space, water transportation,
and mechanical features. Simultaneous measuring of the length alternating during the salt and ice crystallisation has revealed
detailed information on the development of crystal in the pore spaces as well as the development of stress. These findings
can help to understand the damaging mechanisms. 相似文献