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Analysis and characterization of Roman and Byzantine fired bricks from Greece
Abstract
Fired bricks were for millenniums one of the main building materials of masonry structures of the old civilizations developed around Mediterranean basin. In ancient Greece, fired bricks systematically appeared in buildings from the fourth century BC, although ceramic manufacturing was well known since the pre-historic period. In this research study, the morphological, mechanical and physical characteristics, as well as the microstructure of old bricks from Greek monuments dated from the Roman and Byzantine period, are presented. Based on the results, bricks were usually produced manually by using empirical criteria. The bricks of Roman and Byzantine period were mainly plates of 30 x 30 or 30 x 40 cm. Their thicknesses ranged from 2.5 to 6 cm. Different additives were used to improve their properties, such as fine and coarse aggregates or fibrous materials. Generally, old bricks of those periods were of low apparent specific density (1.5-1.8), high absorption (13-30 %) and relatively low compressive strength (5-20 MPa), due to large pores and cracks into their matrix. Due to their surface roughness, the adhesion with the lime mortars was relatively high. A chemical reaction of lime mortar with the amorphous siliceous materials presented in old bricks has often contributed to the improvement of the mortar-brick bond. Since the characteristics and behavior of old bricks of the aforementioned historic periods do not differ much, it implies that both raw materials and the manufacturing techniques used for bricks production had not changed through a long historic period.
... Bricks, ceramic materials obtained by firing raw clay at temperatures ranging between 650 and 1100°C, are the most ancient man-made building materials (Cardiano et al. 2004) comprising masonry structures of the old civilizations, developed around the Mediterranean basin (Stefanidou et al. 2015). Bricks were the favourite building materials in Rome between the middle of the first century (Emperor Nero) and the beginning of the fourth century (Emperor Constantine) (Bloch 1941). ...
... The latter, if it is present, represents the only way to interpret the provenance and manufacture of clayey materials (Scalenghe et al. 2015). The latter consist of heterogeneous mixtures of aluminate, silicate and aluminosilicate compounds of calcium, iron and alkali metals (Stefanidou et al. 2015). During firing, the raw materials (clay minerals and predetermined fractions of silt and sand-temper) are transformed into new artificial materials, in which mineralogic changes occur. ...
... However, not only the colour differences could be attributed to different raw materials (nature of the clay) but also to differences in the temperature of the firing process and as well as to the nature and amount of temper (Cardiano et al. 2004). In a study conducted on fired bricks, evaluating the different physic-mechanical properties, the red colour (light red and reddish brown) was attributed to Roman bricks and the yellow colour (reddish yellow) to Byzantine bricks (Stefanidou et al. 2015). Anyway, that is an isolated study. ...
Red and yellow bricks are the wall-building materials generally used in Roman masonries. The reasons for the different coloration are not always understood, causing loss of crucial information both for the conservation and for the archaeological knowledge of the cultural sites. In this work, a combination of in situ analyses, employing portable Raman spectroscopy and handheld energy dispersive X-ray fluorescence (HH-ED-XRF) spectroscopy along with chemometric analysis, was carried out on ancient Roman bricks of the “Casa di Diana” building (Ostia Antica, Italy-130 CE). Specifically, the compounds and the characteristic elements, which describe each type of brick (red and yellow), were studied avoiding destructive or invasive sampling. The molecular analysis allowed us to identify the major and minor compounds that characterise the bricks (anatase, hematite, quartz, calcite and silicates). However, the elemental analysis gave more useful information. Thus, the complex HH-ED-XRF data matrix generated was treated by a specific principal component analysis (PCA) to identify behavioural differences of the coloured bricks. The results revealed that Ca and Fe are the discriminatory elements for the two types of bricks. The PCA outcomes suggest that the contribution of certain elements is different in the bricks (mainly Ca, P, Sr, As and S, for yellow bricks), which could indicate different raw materials. Even among bricks with the same red colour (Al, Si, Ti, K, Fe, Cr, Mn, Ni, Zn, Cu, Rb and Zr, seemed to be the elements linked to raw materials), as a function of the surface impacts (orientation and microclimate affect the salts’ formation), a distinction was made. Furthermore, the PCA pointed out that the yellow bricks are those more affected by decaying processes (related with Ca, P and S), complying with the Raman spectroscopy results in which the efflorescences (gypsum) affect especially the surface of these types of bricks.
... The clay bricks of the composition used in Nippur and Mesopotamia civilizations are encountered in other ancient buildings in the world, for example in ancient Greece at the fourth century BC and that used in Portuguese monuments dated to the period of 12th-18th centuries. Previous studies have described the methodology of producing fired bricks used in the former buildings in four stages [8,9]. The first stage incorporates selection of an appropriate soil as a raw material which is usually clay. ...
... In general mechanical, the physical, thermal, mineralogical and durability properties of clay bricks and their masonry structures are affected by the raw clay, weathering mechanism, material aging and long term behaviour. The former effects are usually by the action of atmospheric agents such as wind and water [8][9][10]. ...
... For the same weight, the highest volume sample is associated with the lowest value of the density and vice versa. Moreover, the microstructure of the ancient brick units and the connection of their interior pores may have the role in producing the specified level of density [9]. ...
This paper describes a programme of experimental measurements performed in support of a parallel
programme of field investigations to evaluate the construction methods used at the site of the ancient
city of Nippur. The experimental programme investigated both the mechanical properties and durability
of the ancient clay masonry units used in the construction of buildings at Nippur including tests for
dimensional consistency and flatness, density, compressive strength, initial rate of water absorption and
thermal properties. The test results have been compared with those for modern brick units available
nowadays in Iraq and with hard natural stone samples.
The field investigations showed that the important buildings were constructed using composite walls
inclusion firing clay masonry units with two nominal dimensions (30× 30×7) cm and (30× 15× 7) cm (l, w
and h). The formulation of working design technique was followed to achieve the member stability
under applied loads. Layers of bitumen material were used as a binder for both bed and head joints in
order to provide the desired strength level for the masonry wall.
The experimental results show that the ancient brick units and stone samples exceed the tolerance and
range of dimensions limits recommended by current EN Standards. Lower density values were recorded
for the ancient brick units compared with that for both modern clay brick and stone specimens and
these values showed agreement with the modern classification of high density (HD) units.
Approximately similar values of compressive strength were observed for both ancient brick units and
natural stone samples reaching about 17 MPa, whilst modern clay brick samples showed lower
compressive strength value suitable for application of partition walls. The initial rate of water absorption
increases with an increase of the soaking time, but tends to decrease after 90 minutes for both ancient
and modern brick units. Superior performance in terms of thermal conductivity, thermal resistance and
durability under fire action were observed for the ancient brick samples compared with modern clay
brick and stone samples.
... Recent researches revealed that historic bricks were mainly composed of quartz, feldspar, muscovite, amorphous silica, alumina and hematite which provides red color for the bricks [29][30][31]. The chemical composition of the historic bricks consisted of silica (SiO 2 ), alumina (Al 2 O 3 ), iron oxide (Fe 2 O 3 ), potassium oxide (K 2 O), sodium (Na 2 O), calcium (CaO) and magnesium (MgO) oxides. ...
... Results of the major oxide compositions of construction bricks of Çinili Bath were similar to the chemical composition of historical bricks from 12 th to 18 th centuries [34,30,31]. But then, brick aggregates of plasters had higher SiO 2 (85.97-91.72 %), lower Al 2 O 3 (3.04-6.75 ...
Ottoman baths were peculiar buildings with their function in community life, architectural characteristics and material use. Their interior spaces were exposed to high humidity and temperatures that made the building structure vulnerable to physical, chemical, physicochemical and biological degradations. Plasters used on the interior wall surfaces were the most important agents to protect the structure from deterioration and provide durability. This study aims to exhibit the plaster characteristics of Çinili Bath in _ Istanbul which was an outstanding example of Ottoman baths and built by Great Architect Sinan. Basic physical properties, raw material compositions, mineralogical, microstructural and hydraulic properties of original brick-lime plasters called as horasan (khorasan) plasters used on the walls were determined by XRF, XRD, SEM-EDS and TGA. Multilayered plaster application together with the use of glazed tiles were observed on the wall surfaces of all interior spaces. The plasters were produced from pure lime and pozzolanic crushed brick or tile aggregates and hydraulic because of the pozzolanic properties of aggregates. They are stiff, compact and durable in hot and humid conditions of bath buildings due to their self-healing properties and the formation of calcium silicate hydrates and calcium aluminate hydrates at the lime-brick interfaces and in the pores of the pozzolanic brick aggregates by the reaction of lime. Characteristics of brick aggregates were compared with the construction bricks used in the building. Their chemical and mineralogical compositions revealed that the aggregates had not been produced from construction bricks. All the results indicated that brick-lime plasters were the most suitable materials for bath buildings to protect the structure from the effect of water.
... As long as stable compounds form, porosity falls and the strength of mortars increases [74]. The amorphous silica and aluminosilicates in Roman bricks can promote the chemical reaction with the hydrated lime and also physically contribute to their bonding [85][86][87], explaining the better mechanical characteristics of the M2 mortars. The C-S-H formations contribute more than the CaCO 3 phases in the mechanical strength development of these mortars [83]. ...
... Here, the morphology of the silicate minerals also had an important role. Since the sand has a tight crystalline form, the lime binder cannot cling and react, whereas the ceramic, especially Roman ceramic, has amorphous silica, which allows the alkaline binder to enter and react [87]. Nevertheless, and contrary to expectations, the Roman ceramics from Complutum contain high temperature minerals (e.g., mullite and gehlenite), the amorphousness of which is not enough to promote pozzolanic reactions. ...
This study investigates the effect of the diethyl carbonate as a carbonation accelerator on the carbonation of lime mortars. Two types of lime mortars were prepared, one using lime putty and standard sand and the other using lime putty, dust and fragments of ceramic and standard sand. After a curing time of two weeks, the accelerator product, diethyl carbonate in a solution of ethanol and water, was sprayed on half of the mortars of each type. The differences in the carbonation performance were analyzed at 28, 90, 120 and 180 days using different analytical methods. Apart from the mineralogical and petrographic characterization, the physical, mechanical and hydric properties of the samples were determined. Mechanical tests were conducted only at 90, 120 and 180 days, because at 28 days the lime mortars were considered still too soft. The mortar samples with the accelerator had steadier carbonation and slight changes in their microstructure.
... Recent researches revealed that historic bricks were mainly composed of quartz, feldspar, muscovite, amorphous silica, alumina and hematite which provides red color for the bricks [29][30][31]. The chemical composition of the historic bricks consisted of silica (SiO 2 ), alumina (Al 2 O 3 ), iron oxide (Fe 2 O 3 ), potassium oxide (K 2 O), sodium (Na 2 O), calcium (CaO) and magnesium (MgO) oxides. ...
... Results of the major oxide compositions of construction bricks of Çinili Bath were similar to the chemical composition of historical bricks from 12 th to 18 th centuries [34,30,31]. But then, brick aggregates of plasters had higher SiO 2 (85.97-91.72 %), lower Al 2 O 3 (3.04-6.75 ...
Ottoman baths were peculiar buildings with their function in community life, architectural characteristics and material use. Their interior spaces were exposed to high humidity and temperatures that made the building structure vulnerable to physical, chemical, physicochemical and biological degradations. Plasters used on the interior wall surfaces were the most important agents to protect the structure from deterioration and provide durability. This study aims to exhibit the plaster characteristics of Çinili Bath in İstanbul which was an outstanding example of Ottoman baths and built by Great Architect Sinan. Basic physical properties, raw material compositions, mineralogical, microstructural and hydraulic properties of original brick-lime plasters called as horasan (khorasan) plasters used on the walls were determined by XRF, XRD, SEM-EDS and TGA. Multilayered plaster application together with the use of glazed tiles were observed on the wall surfaces of all interior spaces. The plasters were produced from pure lime and pozzolanic crushed brick or tile aggregates and hydraulic because of the pozzolanic properties of aggregates. They are stiff, compact and durable in hot and humid conditions of bath buildings due to their self-healing properties and the formation of calcium silicate hydrates and calcium aluminate hydrates at the lime-brick interfaces and in the pores of the pozzolanic brick aggregates by the reaction of lime. Characteristics of brick aggregates were compared with the construction bricks used in the building. Their chemical and mineralogical compositions revealed that the aggregates had not been produced from construction bricks. All the results indicated that brick-lime plasters were the most suitable materials for bath buildings to protect the structure from the effect of water. Keywords: Çinili Bath, Architect Sinan, Plaster, Brick, Hydraulicity, Self-healing
... It is worthy to mention that the material relaxation might have been triggered by the content of PET waste and microstructural arrangement. However, Stefanidou et al. [35] reported on the stress-strain characteristics of clay bricks, which concluded that bricks do not behave elastically even in the range of small deformations due to the brittleness of the brick material. ...
The number of wastes generated from PET plastic coupled with other wastes associated with manufacturing industries is running in billion metric tonnes annually. If scientific solutions are not provided, these wastes will become a fulcrum to an impending environmental disaster. The aims to avert the impending consequences of this disaster and conserve natural materials have fostered sustainable production of low-carbon embedded construction materials. With this view in mind, this investigation is channelled towards evaluating the strengths and durability of waste plastic bricks (WPB) fabricated by the valorization of scrap PET plastic and foundry sand waste. The WPB masonry bricks were fabricated using plastic to sand ratios of 10:90, 20:80, and 30:70, respectively. A series of compressive strength tests, modulus of rupture tests, apparent porosity tests, water absorption tests, salt-resistance tests were conducted to investigate the strength and durability of the WPB in conformance with the South African National Standard (SANS 227) for individual load-bearing masonry face brick unit. Compared to the clay bricks with 18 MPa what of strength, the test result revealed that the WPB rendered an average com-pressive strength of 35.2 MPa. Furthermore, the test result showed that the WPB recorded significant strength resistance under tension compared to the clay brick due to the ductility properties of scrap plastic waste. Also, the acid effects were significantly resisted on the surface WPBs due to the hydrophobic property of the PET waste. The stiffness of the clay bricks portrayed a brittle response, whereas WPBs benefited with high-ductility properties.
... With the systematic use of fired bricks, the width of joints increased, leading to the decrease of the constructions' weight and to the increase of their height [2]. In Byzantium, brick masonries prevailed, offering a variety of structural elements built with fired bricks (domes, arches, and pillars) [3]. ...
The Babylon of Egypt was constructed in the Roman period (300 AD), in the old Cairo area. It is one of the most distinguished monuments in the universal architectural heritage. The present study introduces the characteristics of roman and byzantine bricks and their joining structural mortars used in the roman fortress in order to risk assessment and to define the necessary characteristics of the intervention retrofitting new materials, which will be used in the ongoing preservation work of this fortress. To achieve such, several analyses and laboratory tests like ultra-sonic pulse method testing (ultrasonic pulse velocity, dynamic modulus of elasticity), uniaxial compression test and Brazilian splitting tension test, were carried out to determine their basic, mechanical and engineering properties, along with the microstructural properties determination using Mercury porosimeter. On the other hand, the morphological description, petrography, mineralogical and microstructural properties were determined using scanning electron microscope equipped by EDS, polarizing light microscopy, XRD and XRF.
The obtained results indicated that the joining structural mortars are ranging from medium to stiff, low compacted, having hydraulic properties due to the use of natural furnace slag, brick powder, brick fragments and aggregates that match with the pozzolanic properties and also rich in active silica and alumina. The examinations reveal the use of limestone fractions as coarse aggregates or fillers. On the other hand, the Roman bricks consist mainly on quartz and feldspars embedded in a matrix of iron oxide and burnt clays. Also the obtained results indicated that old bricks were of low apparent specific density (1.4–1.7), medium absorption (10–20 %) and low uniaxial compressive strength (2–10 MPa), with Young's modulus 1.2 to 3 GPa. The ultra-sonic wave velocity is 1.7 to 2 km/s, with dynamic modulus of elasticity 2.4 to 4 MPa. The shear modulus is 917 to 1500 MPa. These results may be due to large pores and cracks into their matrix. Due to their surface roughness, the adhesion with the lime mortars was relatively high.
... Traditionally produced bricks were fired at low temperature (not higher than 900-950°C) and consequently, they were less resistant and more sensitive to decaying agents such as moisture and salts. Their porosity was high and they were prone to water absorption both naturally and by capillarity [24][25][26][27]. In order to maintain the traditional technique and produce compatible bricks which could be used in restoration works, the idea to protect them against deterioration by applying a treatment with solutions by the total immersion technique was studied. ...
For millenniums, bricks were the main building material for the load-bearing structural elements of constructions. They were produced manually and they were fired at low temperature. They also present low apparent specific density, high absorption, high surface roughness and relatively low compressive strength. Nowadays, bricks used for restoration works should be compatible to the old ones. As the existing line of modern brick manufacturing is far from the above mentioned criteria, the way to solve the problem is to manually produce these special building materials which render them expensive and laborious. Additionally, their high porosity and soft nature make them easily deteriorated by different environmental conditions. The protection of traditional bricks is an important step towards their durability and a challenge especially nowadays where nanotechnology has been proven efficient when it is incorporated in coatings for building materials. In the present paper, hand-made brick samples were treated with different coatings by the technique of total immersion. The solutions tested were both traditional such as linseed oil but also silanes and alkosiloxanes both neat and nano-modified. In order to compare the physical properties of the treated bricks, parameters like capillarity, porosity, absorption and durability have been tested. It was concluded that silica nano-particles and micro-clay enrichment of alkosiloxane was the most sufficient way to protect those special building materials.
... These mineralogical components could occur together when pozzolan fragments and crushed bricks are mixed to create the silicatic aggregate that is added to lime binder, as it used to do in Roman age [53]. Chemical reaction of lime with the amorphous siliceous materials presented in brick's fragments has often contributed to the improvement of the mortar-brick bond [54][55][56]. The Raman spectroscopy results confirmed all the mineral phase described in Table 4. ...
Nowadays, a broad range of analytical techniques are available and applied in the preservation of Cultural Heritage. However, to characterise the historical materials and to obtain quantitative and qualitative information of their composition and structure, it is necessary to choose the appropriate analytical instruments.
In fact, for each study, depending on the analytical aim and nature of the analysed materials, it is necessary to combine the scientific and technological knowledge of the device used in order to define an adequate plan of action.
In the field of Cultural Heritage conservation, destructive techniques should be avoided, wherever possible, to preserve the integrity of the historical buildings and its decorations. Therefore, the development of non-invasive, non-destructive and in-situ analysis is extremely important.
Taking all of this into account, this chapter contains the main advantages of the more useful selected analytical techniques to characterise ancient building materials, taking into consideration a particular case study: a roman masonry, dated 130 A.D (Emperor Hadrian), found in the Ostia Antica archaeological site (Italy). Specifically, we will deal with bricks and mortars, the wall building materials of the “Casa di Diana” Mithraeum.
The combined use of techniques such as polarized microscope, ion chromatography, X-ray diffraction, X-ray fluorescence and Raman spectroscopy was selected, allowing us to extract information in terms of phase identification, quantify crystalline compounds and complex polyphasic mixtures (solid solutions), identify deterioration products and, determine their nature.
Using this methodology it will be possible to analyse the complete life-cycle of the roman’s manufacturing processes, starting from the raw materials, through to the man-made production and constructive techniques evolution. Moreover, the obtained results enable us to study the forms of degradation, as well as to choose and apply a suitable procedure for the preservation and safeguard of the materials taken into consideration.
... Regarding bricks, Thessaloniki was diachronically (at least from the Roman era) a center of brick production [6]. Therefore different types of bricks (compact, hollowed) were usually used during the 19 th -20 th century for different applications. ...
During the end of the 19th century, Thessaloniki expanded and new buildings were constructed according to the architectural style of this period. Nowadays, they present severe damages, since they were abandoned and need restoration interventions. This paper concerns the systematic study of the building materials and construction techniques, of six Eclecticism buildings concerning: Administration building. The study includes insitu observation of the constructional materials and techniques and analysis of the bearing system. An experimental analysis of building materials, revealed the main principles and details followed in the construction of the past. As it is concluded, the main building materials used were unshaped stones (limestone, schist), bricks (compact and hollowed) and mortars (structural, plasters, renders) based in lime and pozzolan. Generally, ashlar masonries were found in the basement and ground floor of the structures, while brick masonries were used for the construction of the first and second floor. The compact bricks were used for the external walls, while hollowed bricks were used for the upper and internal ones. Floors were constructed with wooden or metallic beams and were covered with tapestry or ceramic tiles. Metallic elements were also used for the connection and confinement of the masonry walls. Externally façades were decorated with thick colored renders of specific stratigraphy, while internally wall and roof plasters were decorated with frescoes. The study of the historic buildings of Eclecticism of Thessaloniki showed many similarities regarding the materials used and the constructional techniques applied. In all cases, the principles followed were closely related to the sustainability and economy, taking into account specific architectural and morphological aspects.
... Regarding bricks, Thessaloniki was diachronically (at least from the Roman era) a center of brick production [6]. Therefore different types of bricks (compact, hollowed) were usually used during the 19 th -20 th century for different applications. ...
During the end of the 19th century, Thessaloniki expanded and new buildings were constructed according to the architectural style of this period. Nowadays, they present severe damages, since they were abandoned and need restoration interventions. This paper concerns the systematic study of the building materials and construction techniques, of six Eclecticism buildings concerning: Administration building of the Allatini complex (1879), 1st Gymnasium of Thessaloniki (1890), Melissa orphanage (1896), the house of Sarantaporou and Stratou st. (1906), the building of Anagenniseos st. (1910), Villa Bianca (1913). The study includes insitu observation of the constructional materials and techniques and analysis of the bearing system. An experimental analysis of building materials, revealed the main principles and details followed in the construction of the past. As it is concluded, the main building materials used were unshaped stones (limestone, schist), bricks (compact and hollowed) and mortars (structural, plasters, renders) based in lime and pozzolan. Generally, ashlar masonries were found in the basement and ground floor of the structures, while brick masonries were used for the construction of the first and second floor. The compact bricks were used for the external walls, while hollowed bricks were used for the upper and internal ones. Floors were constructed with wooden or metallic beams and were covered with tapestry or ceramic tiles. Metallic elements were also used for the connection and confinement of the masonry walls. Externally façades were decorated with thick colored renders of specific stratigraphy, while internally wall and roof plasters were decorated with frescoes. The study of the historic buildings of Eclecticism of Thessaloniki showed many similarities regarding the materials used and the constructional techniques applied. In all cases, the principles followed were closely related to the sustainability and economy, taking into account specific architectural and morphological aspects.
... Nysa'dan alınan Roma dönemi tuğlalarının birim hacim ağırlık değerleri ise diğerlerine göre daha düşük, gözeneklilikleri daha yüksektir. İncelenen Roma dönemi tuğlalarının birim hacim ağırlık ve gözeneklilik değerleri farklı bölgelerde bulunan tarihi tuğlalar ile benzer aralıklardadır [8]. ...
Bu calismada, Bergama’da bulunan Kizil Avlu ( Serapeum ) ile Aigai ve Nysa antik kentlerinde bulunan farkli yapilardan alinan Roma donemi yapi tuglalarinin kimyasal ve mineralojik kompozisyonlari, fiziksel, mikroyapisal ve puzolanik ozellikleri XRF, XRD, FTIR, SEM-EDS ve kimyasal analizler ile belirlenmistir. Tuglalarin kimyasal kompozisyonlarini olusturan temel oksitler ve eser elementler istatistik yontemler kullanilarak tuglalarin uretiminde kullanilan hammadde kaynaklarinin ayni olup olmadigini belirlemeye yonelik olarak degerlendirilmistir. Elde edilen sonuclar, Roma donemi yapi tuglalarinin kalsiyumca zengin kil kaynaklari kullanilarak ve dusuk sicakliklarda (< 900°C) pisirilerek uretilmis olduklarini gostermistir. Tugla ornekler temel olarak kuvars, albit, anortit, muskovit ve hematit minerallerinden olusmustur. Fakat antik kentlerden toplanan bu tugla orneklerin kimyasal kompozisyonlarinin istatistiki olarak anlamli farklilik tasiyor olmasi tuglalarin uretiminde yerel hammadde kaynaklarinin kullanildigini ortaya koymustur.
... Regarding bricks, Thessaloniki was diachronically (at least from the Roman era) a center of brick production [6]. Therefore different types of bricks (compact, hollowed) were usually used during the 19 th -20 th century for different applications. ...
During the end of the 19th century, Thessaloniki expanded and new buildings were constructed according to the architectural style of this period. Nowadays, they present severe damages, since they were abandoned and need restoration interventions. This paper concerns the systematic study of the building materials and construction techniques, of six Eclecticism buildings concerning: Administration building of the Allatini complex (1879), 1st Gymnasium (1890), Melissa orphanage (1896), the house of Sarantaporou st. (1906), the building of Anagenniseos st. (1910), Villa Bianca (1913). The study includes insitu observation of the constructional materials and techniques and analysis of the bearing system. An experimental analysis of building materials, revealed the main principles and details followed in the construction of the past. As it is concluded, the main building materials used were unshaped stones (limestone, schist), bricks (compact and hollowed) and mortars (structural, plasters, renders) based in lime and pozzolan. Generally, ashlar masonries were found in the basement and ground floor of the structures, while brick masonries were used for the construction of the first and second floor. The compact bricks were used for the external walls, while hollowed bricks were used for the upper and internal ones. Floors were constructed with wooden or metallic beams and were covered with tapestry or ceramic tiles. Metallic elements were also used for the connection and confinement of the masonry walls. Externally façades were decorated with thick colored renders of specific stratigraphy, while internally wall and roof plasters were decorated with frescoes. The study of the historic buildings of Eclecticism of Thessaloniki showed many similarities regarding the materials used and the constructional techniques applied. In all cases, the principles followed were closely related to the sustainability and economy, taking into account specific architectural and morphological aspects.
... Fired bricks are some of the most primeval and resilient building materials and have been used since around 3000 BC (Stefanidou, 2014). Clay bricks have an impressively high load-bearing capacity while keeping high dimensional stability and compressive strength. ...
... It is worthy to mention that the material relaxation might have been triggered by the content of PET waste and microstructural arrangement. However, (Stefanidou et al., 2015) reported on the stress-strain characteristics of clay bricks, which concluded that bricks do not behave elastically even in the range of small deformations due to the brittleness of the brick material. ...
The level of generated plastic waste has awash over a billion metric tonnes of this waste into our environment. If an effective long-lasting solution to this impending disaster is not provided through recycling, reengineering, and conversion of this waste to resourceful materials. Then sustainability and conservation of natural non-replenishable materials will be severely threatened. The aims to avert the impending consequences of this disaster and conserve natural materials have given rise to a sustainable future in the production of low carbon embedded construction materials. Under these circumstances, this study, therefore, presents the strengths and durability of waste plastic bricks (WPB) produced from blending scrap PET plastics and foundry sand. The WPB masonry bricks were produced using ratios of 10:90, 20: 80, and 30: 70 to the combined dry mass of PET and sand. Series of compressive strength tests, modulus of rupture (MOR) tests, apparent porosity tests, water absorption tests, salt-resistance tests, ultrasonic pulse velocity, and scanning electron microscopy (SEM) tests were conducted to investigate the strength and durability of the WPB in conformance with the South African National Standard (SANS 227) for individual load-bearing masonry face brick unit. Compared to the clay bricks with 18 MPa what of strength, the test result revealed that the WPB rendered an average compressive strength of 35.2 MPa. Furthermore, the test result showed that the WPB recorded significant strength resistance under tension compared to the clay brick due to the ductility properties of scrap plastic waste. Also, the acid effects were significantly resisted on the surface WPBs due to the hydrophobic property of the PET- waste. The stiffness of the clay bricks portrayed brittle response, whereas WPBs benefited with high ductility properties, therefore, revealed a great proportionality between the dynamic modulus and ultrasonic pulse velocity (UPV) with a coefficient of determination (R2) of 90%.
... A series of laboratory tests were realized in order to determine their physico-mechanical and chemical properties [7] [8]. Microstructure observation was performed with stereoscope (Leica Wild M10) assisted by image analysis (ProgRes), aggregates gradation was tested by hand grinding and sieving, according to EN1015-1:1998, porosity and apparent specific gravity were performed according to RILEM CPC 11.3, while compressive strength was tested in shaped cubic samples of 4x4x4cm. ...
At the end of the 19th and beginning of the 20th century, urban centers were enlarged in Greece and new, large scale constructions (public buildings, residences etc) were built. The paper concerns the systematic analysis of the building materials and constructional techniques of six historic buildings, dated at this period and situated in the regions of Thessaloniki, Florina and the islands of Chios and Rhodes. The architectural style of the buildings varied, concerning Neoclassicism, Eclecticism, Art Nouveau and Art Deco, while in all cases the regional aspects regarding the available raw material and the traditional constructional techniques were maintained. The study included site surveys of the structural system, mapping of pathology, analysis of building materials, as well as analysis of the bearing system. From the evaluation of the results it was concluded that there were many similarities, regarding the building materials used and the constructional techniques applied. In general, local materials were used for the construction of masonries, while the decoration of the facades and of the internal walls was based on hand made mortars (renders, plasters) applied by specific techniques.
... (ii) 'light brown' bricks have an f b = 14.7 MPa and w a-= 18.13% and (iii) 'dark brown' bricks have an f b = 22.7 MPa and w a = 13.4% [39]. The characteristics of available fired-clay bricks, chosen in this investigation, are hence in the low range of those from the site survey, and typically found in heritage masonry [52,53], yet they can be used for comparative assessments and structural repair studies. ...
This paper examines the fundamental mechanical properties of masonry elements incorporating fired-clay bricks and hydraulic lime mortars under ambient-dry and wet conditions, corresponding to 48 h submersion in water. In addition to complementary material characterisation assessments, two types of specimens are tested: cylindrical cores in compression, and wall elements in compression. Overall, a detailed account of more than 50 tests is given. Apart from conventional measurements, the use of digital image correlation techniques enables a detailed assessment of the influence of moisture on the constitutive response, confinement effects and mechanical properties of masonry components. The uniaxial compressive strengths of wet brick elements and brick–mortar components, resulting from tests on cylindrical cores with height-to-depth ratios of around two, are shown to be 13–18% lower than those in ambient-dry conditions. The tests also show that enhanced confinement levels in brick units mobilise 67–92% higher strengths than in the corresponding unconfined cylinders. Moreover, experimental observations indicate that the presence of significant confinement reduces the influence of moisture on the mechanical properties as a function of the brick and mortar joint thickness and their relative stiffness. As a result, the failure of wet masonry walls in compression is found to be only marginally lower than those in ambient-dry conditions. Based on the test results, the influence of moisture on the constitutive response and mechanical properties of masonry components is discussed, and considerations for practical application are highlighted.
... Thus, to examine if the terracotta tiles used for the experiment could be a cause for errors in the experiment, a small study was carried out, examining the characteristics of the tiles (porosity, density, and water absorption) compared to the characteristics found in medieval clay bricks. This study showed that the terracotta tiles were much denser than medieval clay brick as they had a very low porosity (∼15%) compared to known porosity values (∼33-37%) in older clay bricks (Böke et al. 2006;Stefanidou, Papayianni, and Pachta 2015). Moreover, water absorption tests with the Karsten tube test (RILEM 11.4 2015) showed that the absorption rate in the terracotta tiles was ten times slower than in the medieval brick. ...
This paper describes attempts to replicate medieval plaster using hot-mixing, where quicklime, aggregate, and water are combined in a single exothermic process. The experimental study aimed to reproduce the structural characteristics of medieval plaster while making sample materials for conservation trials, rendering them more relevant and comparable with the medieval materials on which treatments take place. For wall painting conservation, similar capillarity and permeability are particularly important for trials focusing on consolidation, desalination, and cleaning. These characteristics are greatly influenced by the materials, working protocol, and curing conditions used in the replication process. Replicated plaster and plaster sampled from Gothic wall paintings were analysed to provide data regarding porosity, type of lime, aggregates, and binder/aggregate ratio using thin-section analyses, X-ray diffraction, porosity measurements, and mercury intrusion porosimetry. The comparative study showed a close match between one of the two recreated mortars and the original plaster.
... Comparison of test results on bricks of other sites in Asia Minor, Southern Europe, and Northern Africa. Byzantine monuments, Thessaloniki, Greece, 7-11th century[62] 4.5-16.08 1.46-1.84 ...
In this study, the physical–mechanical and mineralogical properties of bricks used in historical structures of the site of Harran, Turkey have been investigated. Harran was destroyed by the Mongol army, during the Turkish reconquest campaign around the 1260s. The remains of the buildings made of bricks and basalt/limestone were recently uncovered almost in their entirety. Several brick samples have been taken from the burial mound, the university, the city walls, the castle, and the great mosque. From the visual analyses, it was noted that the bricks have unique colors such as pottery, desert beige, and canyon. Physical analyses show that the absorption rates of the bricks are between 17.30–38.12%, their densities between 1.33–1.70 g/cm3, and porosities between 8.88–25.31%. For the mechanical analyses, the bending strengths have been found to be between 0.82–1.86 MPa and compressive strengths between 6.69–7.95 MPa. The thin-section images show that the bricks contain calcite, muscovite, and plagioclase quartz and pyroxene minerals.
... N/mm 2 ) is measured. These values of strength approximately correspond with the upper range of compressive strength found in literature concerning historic bricks [88][89][90][91]. Interestingly, the compressive strengths are within the mechanical range of contemporary soft mud solid clay bricks [92]. ...
Representative and very uneven texturally bricks having yellow/beige or pale or dark red colors from the Renaissance walls (16th century) of Padua, Northeast Italy, were studied by means of colorimetric, petrographic (MOP), chemical (XRF), mineralogical (PXRD) and microstructural analysis (FESEM-EDS). Starting from the color measurements of the ceramic bodies, the manufacturing technologies and their influence on the physical behavior and durability of the bricks were established. The porous system was characterized by means of hygric tests and mercury intrusion porosimetry; the compactness and structural anisotropy were defined through ultrasound velocity; the uniaxial compressive strength was determined; and durability to salt crystallization and frost action of the bricks was assessed. Mg- and Ca-rich illitic clays fired at temperatures ≥900 °C were used to manufacture the beige hue bodies, while the pale red bricks were made out with Ca- and Fe-rich illitic clays fired at 850–900 °C. A lower carbonate content on the base clays and a lower firing temperature were the main causes responsible for the changing colors from beige to red hue. The increase of the red color was associated to higher silicate inclusions content and lower development of reaction rims around grains. The low sintering degree achieved yielded highly porous bodies with diverse porous systems, leading to differential physical performance and durability of the bricks that may turn out beneficial for the conservation of the historic walls.
... It is worthy to mention that the material relaxation might have been triggered by the RCG content and microstructure arrangement of the non-fired bricks. The stress-strain characteristics of bricks do not behave elastically even in the range of small deformations due to the brittleness of the bricks (Stefanidou et al. 2015). ...
Waste utilization as an alternative for masonry bricks has proven to compensate for the dwindling natural construction materials particularly clay. Currently, South African municipalities are struggling to update their effective waste management techniques. Improper waste management is one of the major constraints affecting the natural environment due to the associated environmental waste pollution. This constraint fostered the motivation to the present study, which reported on the findings obtained from the masonry bricks produced from blends of recycled crushed glass (RCG) and fly ash (α-FA) with the inclusion of ordinary Portland cement (OPC) at varying percentages. The masonry bricks were produced with 5%, 10%, and 15% inclusion of OPC to the combined weight of α-FA and RCG. The produced bricks rendered significant compression strength resistance compared to the fired clay bricks that are 3.8% higher on average. However, the compressive strength of all the produced bricks in this study satisfied the South African National Standard SANS 227 Code requirements (i.e., ≥7 MPa) for individual load-bearing masonry brick. The scanning electron microscopy (SEM) analysis confirmed that the identified void spaces within the microstructure of the brick specimens with 5% OPC were the major cause of the low strength resulting from the incomplete pozzolanic reaction. Also, the effects of sulphate salt were significantly resisted on the surface of all the tested bricks incorporating α-FA and RCG, due to the presents of aluminosilicates compounds that triggered pozzolanic reactions within the brick's matrix. The stiffness of the investigated bricks portrayed brittle characteristics due to the developed strength after production. This revealed the existence of a great proportionality between the dynamic modulus and ultrasonic pulse velocity (UPV) revealed a coefficient of determination (R 2) equivalent to 90% because of the percentages of RCG particles.
... It is worthy to mention that the material relaxation might have been triggered by the RCG content and microstructure arrangement of the non-fired bricks. The stress-strain characteristics of bricks do not behave elastically even in the range of small deformations due to the brittleness of the bricks (Stefanidou et al. 2015). ...
During the two seasons of rescue archaeological excavations at the hillfort site of Brekinjova Kosa, the remains of an Early Medieval structure (probably a church) and Early Medieval burials containing rich grave goods were recorded. The most remarkable feature is a rich burial within the structure (grave 4) whose grave goods put it among the richest Early Medieval graves so far excavated on the territory of modern-day Croatia. Apart from the finds within the graves themselves, a certain amount of Early Medieval pottery shards were recorded at the site. The area surrounding the site is mostly archaeologically unresearched and today sparsely populated, but this type of find bears witness to its importance in the Early Middle Ages.
This study reports the first analytical study conducted on samples of fired bricks, bedding mortar and plaster layers collected from the catacombs of Ptolemy IV Philopator at Karnak temples, Upper Egypt. These unique constructions comprise three-level rectangular vaulted brick shrines that lined up in three passages. The microscopic particularities of the samples were assessed by digitalized optical handheld microscope, while the petrographic analysis was depicted by polarized light microscope. X-ray diffractometer was used to analyse some brick, mortar and plaster samples. The morphological description and microchemical analysis, on various points in the samples, were attained via the field-emission scanning electron microscope with an energy-dispersive X-ray spectrometer. Further, the molecular and vibrational attributions of some fragments and pigment grains were recognized using Fourier transform infrared spectrometer and Raman microspectrometer (µ-Raman). Results showed that the studied bricks were fired at low temperature using poor-calcium clays. The cross-sectional observation on the plaster layers defined three layers, which are mainly made up of calcium carbonate (calcite). Minerals of quartz, rutile, plagioclase feldspars and calcium silicate were identified, in varying proportions, in the studied plasters. Pigments as Egyptian blue, yellow ochre and red ochre were characterized along the plaster layers. Likely, the microscopic examination and the molecular analysis of the samples disclosed that “fresco” technique was used to decorate the catacombs.
The Imperial Roman Baths in Sagalassos, Turkey, were built in the 2nd century C.E. and have been excavated since the 1990s. The harsh environmental conditions, especially during the winter, resulted in the accelerated decay of the building materials, material losses, and serious structural problems in the Baths. This study explores the comprehensive characterization and multiscale assessment of bricks and mortars for effective preservation of the Baths. Experimental results showed that although the interface between building materials weakened after years of accumulated degradation, the individual materials still had higher strength than those from the same period. The material scale finite element model used to understand the damage mechanism showed that brick failure was caused by the tensile stresses accumulated at the brick-mortar interface when some of the mortar crumbled and fell with deterioration. A global sensitivity analysis was also conducted to investigate the impact of individual layer thicknesses on the stress distribution in the brick and mortar composite. Results indicated that thicker bricks resulted in better confinement at mortar layer and smaller tensile stresses at the bricks.
This chapter therefore focuses on a key element of NDE systems: a suitable analysis of the captured signals, which may provide useful information to detect, characterize or classify damages. The work developed by the authors on ultrasonic signal processing techniques for testing of composite materials is presented to illustrate the potential of signal processing techniques for NDE and a functional methodology, which is based on the parametrization of the ultrasonic signals through cepstral analysis, is proposed in this chapter. After the description of the experimental setup is Section 2, the basis of the cepstral analysis are presented in Section 3. Albeit cepstrum can be directly obtained from the signal applying a simple FFT analysis, the authors show in Section 4 that the application of an appropriate signal model during its estimation provides a much more powerful signal characterization, since it allows taking into account the physics behind the signal propagation in the material. As could be expected for a multilayered material, the author’s experiments reveal that all-pole models are particularly suitable for CFRP modeling. Furthermore, the authors show how
composite plates can be even better represented by all-pole models with sparsely distributed coefficients. In order to verify this, the authors propose an analysis-by-synthesis scheme which, by assuming an underlying sparse digital signal model of the specimen, infers the order and extent of the model parameters corresponding to a certain impact damage level. Then, the authors show how the sparse structure of this model can be applied to the author’s NDE problem. The presented technique is shown to overcome the difficulties that stems from the subtle signal alterations caused by damage, combined with the inherent complexity of those signals due to overlapping echoes, noise, etc. Finally, once a suitable model-based cepstral analysis is established, Section 5 is devoted to the application of feature extraction, dimensionality reduction and damage classification for the impact damage NDE task. Signal cepstra are shown effective in discriminating among several levels of impact damage and as well as inferring quantitative damage parameters. Finally, the chapter conclusions are summarized in Section 6.
At the end of the nineteenth and beginning of the twentieth century, urban centres were enlarged in Greece, and new large-scale constructions (public buildings, residences, etc.) were built. The paper concerns the systematic analysis of the building materials and constructional techniques of five historic buildings, dated at this period and situated in the regions of Thessaloniki, Florina and the islands of Chios and Rhodes. The architectural style of the buildings varied, concerning Neoclassicism, Eclecticism, Art Nouveau and Art Deco, while in all cases the regional aspects regarding the available raw material and the traditional constructional techniques were maintained. The study included on site surveys of the structural system, mapping of pathology, analysis of building materials as well as analysis of the bearing system of the structures. From the evaluation of the results, it was concluded that there were many similarities, regarding the building materials used and the constructional techniques applied. In general, local materials were used for the construction of masonries, while the decoration of the facades and of the internal walls was based on handmade mortars (renders, plasters), applied with specific techniques.
In this study, characteristics of bricks used in the domes of some historic bath buildings dated to 15th century in İzmir were determined in order to indicate the properties of repair bricks that will be used in the conservation works of the domes. For this purpose, their basic physical properties, elemental and mineralogical compositions, firing temperatures and microstructural properties were determined by using XRF, XRD, SEM-EDS and TGA analysis. Analysis results indicated that the bricks are of low density, high porosity and were produced from raw materials containing low amounts of calcium poor clays fired at low temperatures (< 900 °C). They are mainly consisted of small pores with r < 5 μm that make the bricks more susceptible to salt crystallization and freeze-thaw cycles. Although the bricks were fired at low temperatures and susceptible to salt crystallization and freeze thaw cycles, the structural systems of the domes remained without losing their integrity due to the moderate climatic conditions of İzmir. Repair bricks that will be used in the conservation works of the domes should be compatible with the original ones and produced from calcium poor clays by firing at low temperatures.
Nondestructive testing techniques are increasingly being used to obtain the geometry of structural and nonstructural elements and hidden features such as voids, cracks, and detachments. However, the evaluation of the compressive strength and other mechanical properties of ancient materials using such techniques remains a challenge. To reliably assess mechanical properties, it is usually necessary to directly test the strength and deformation of materials by destructive methods. To avoid coring and sampling of the historic fabric, a recent minor-destructive methodology based in microdrilling is used in this paper for the characterization of clay brick. For this purpose, 148 brick specimens from the 12th to 19th centuries were collected from six monasteries in Portugal. A wide range of compressive strength was found by destructive compressive testing, ranging from 6.7 to 21.8 N/mm2. The paper shows that it is possible to reliably estimate the compressive strength of bricks by means of regression curves using the adopted microdrilling technique. DOI: 10.1061/ASCE0899-1561200719:9791 CE Database subject headings: Clays; Bricks; Compressive strength; Drilling.
Crushed brick used in historic brick-lime mortars and plasters (Horasan) were characterized for understanding their properties to develop intervention mortars for conservation. Brick powders were separated from original mortars and plasters, and analyzed by XRD, SEM-EDS, TGA and pozzolanic activity (PA) measurements. The results showed that the microstructures of brick powders were not completely vitrified, and their XRD analysis failed to show the peaks for high temperature (T>900°C) phases. PA measurements of all brick powders showed an ample amount of artificial pozzolan property. Consequently, brick powders aimed for conservation of historic mortars must have high clay contents in addition to being low-fired (T<900°C) in order to produce maximum conversion into amorphous phase for ideal PA values.
The word innovation often refers to a new product, usually to an industrial or technical invention, although actually all kinds of new ideas should be considered. Following Rogers (2003, p. 12), “[a]n innovation is an idea, practice, or object that is perceived as new by an individual or other unit of adoption.” The birth of a new industry can be considered to occur as this new innovation is introduced to the markets by the first manufacturing firm. At this point the potential customers evaluate whether it is worth to adopt the product or not.
Innovation diffusion theory studies the spread of an innovation within a social system (see, e.g., Rogers 2003). The basic aim is to answer the question of why an innovation – an improvement – is not adopted immediately, i.e., why its diffusion takes time. One of the common answers is that not everyone knows of the innovation right away, others add, for example, that gained advantages or profits vary between potential adopters.
There are several dichotomous classifications of innovations, trying to separate innovations into two categories by their nature. Some of such dichotomous divisions are, for example, the division of innovations into incremental and radical innovations (e.g., Freeman 1994), into sustaining and disruptive (e.g., Bower and Christensen 1995), or into continuous and discontinuous innovations (e.g., Tushman and Anderson 1986). Even though the category names differ, these divisions seem to have the same basic aim: An innovation may be a totally new innovation (e.g., product), but it also could be an improvement to an existing innovation. In practice, however, it is often hard to place an innovation into one of these two categories as it might have some characteristics from both.
The clay brick masonry that is much used in historical structures often is in a rather poor state of conservation. In order to intervene correctly in these buildings, it is convenient to characterize the old material. For this purpose, a large sample of clay brick specimens from the 12th to 19th centuries were collected from six Portuguese monasteries and were characterized chemically, physically, and mechanically. A large variability of the properties was found. Additionally, a sample of handmade new bricks, which are commonly used as replacing material, was also analysed. The results were compared with the old bricks, and these new bricks could be possibly adequate as substitution bricks. Still, significant differences were found in chemical composition and in water absorption and porosity, which are much lower in modern handmade bricks. With respect to mechanical properties, the range of values found in old bricks was rather high and the degree of deterioration exhibited a large scatter, meaning that a conclusion is hardly possible.
It is well known that even though historic mortars present low strength and elastic moduli they confer durability to the structures surviving today. The present work investigates the durability of historic mortars in relation to the production technologies employed. Thermal analysis allows for classification of historic mortars in both lime and hydraulic types. Mineralogical data, concerning fabrication and texture, along with thermal analysis provide criteria on specific classification, for: typical lime, crushed brick–lime, cementitious, rubble masonry, hot lime technology and gypsum mortars. The correlation of the measured tensile strength (fmt,k) with the estimated CO2/structurally bound water ratio, indicates direct proportionality to the levels of the hydraulicity. Physico-chemical adhesion and cohesion bonds, studied by SEM-TEM/EDX, developed at the matrix and at the binder/aggregate interface, respectively, becomes the key factor in interpreting the considerable durability that the historic mortars confer to the structures as bearing elements.
Brick was proved to be one of the main building materials in the region of today's Serbia, especially in the time of late antiquity and in the following medieval time. Hence, the idea was born to make a comparison between the main characteristics of late antique and medieval bricks and brickworks from this region that could confirm the continuity and variety of its use. A question of evolution of the use of bricks was partly based on comparison of their estimated properties and also on comparison of applied building techniques and known characteristics of brick production. It has been confirmed that although it is possible to discuss and confirm the continuity in the use of bricks and adequate building techniques, up-to-date research based on quantitative analysis of historical bricks do not offer enough comparable data regarding their quality. Therefore a new field of possible qualitative research is needed in the future.
The aim of the research on brick masonry degradation supported by the D.G. XII is presented. The project has delivered a damage atlas of ancient brick masonry, a book with a description of the types of damage, and their possible causes, in ancient brick masonry structures and Masonry Damage Diagnostic System (MDDS), an expert computer system allowing the user to define damage types and damage causes in ancient brick masonry structures. The scientific methodology used for the development of both documents is given. Illustration of the MDDS is done through explaining the type, processes and cause of damage that occurs to historic brick masonry structures related to air pollution and traffic.
This paper deals with the repair of brickwork and masonry walls that have cracked as a result of ground movement. It outlines work in this field over the last 60 years, identifying the options of repairing the foundation or increasing the ductility of the brittle structure. Practice has been to underpin or otherwise strengthen the foundation but this paper examines the potential to modify the behaviour of the masonry itself by introducing reinforcement. A study of four building facades, verified by a programme of laboratory tests, leads to the conclusion that if the ductility of existing masonry can be improved then the need to underpin will be reduced. This is of particular relevance to non-invasive restoration of historic buildings but also offers an economic repair to more routine structures. The paper concludes that localized reinforcement of masonry walls can significantly increase their tolerance to foundation movement.
Dust and powder fall in medieval churches in coastal regions has been observed. Cores from borings in nine churches have been
analysed and the influence of sodium chloride on thermal expansion and hygroscopic shrinkage has been tested. NaCl forms the
main part of the water-soluble salts in the investigated medieval bricks and is found in the form of very small crystals in
pores smaller than 15 μm. Pore size distribution is determined and shows that medieval bricks have pores in the hygroscopic
range. It is demonstrated that thermal expansion and hygroscopic shrinkage increase with an increase in NaCl content, and
a model to determine the relative thermal expansion is proposed. The dust and powder fall seems to be at a peak at relative
humidities around 75%, the crystallization point of NaCl.
On a observé dans les régions côtières des chutes de poussière et de poudre dans les églises du Moyen-Age. On a analysé des
échantillons prélevés dans 9 églises et on a étudié l'influence du chlorure de sodium (NaCl) sur la dilatation thermique et
le retrait hygroscopique. Le chlorure de sodium constitute la partie essentille des sels solubles à l'eau dans les briques
médiévales examinées, et se rencontre sous la forme de très petits cristaux dont les pores sont inférieurs à 15 μm. On détermine
la distribution dimensionnelle des pores. Celle-ci montre que les pores des briques médiévales se situent dans un intervalle
hygroscopique. On démontre que la dilatation thermique et le retrait hygroscopique augmentent avec une teneur accrue de NaCl
et on propose un modèle de détermination de la dilatation thermique relative. La chute de poussière et de poudre semble à
son maximum à des humidités relatives avoisinant 75%, point de cristallisation du NaCl.
An increasing interest in the pozzolanic activity of bricks with calcium hydrate has been shown recently by researchers dealing with the production of new hydraulic materials for the masonry industry. Furthermore, deteriorated mortars of historic buildings and damaged masonries require repointing, repair or strengthening with mortars and grouts compatible with the existing materials. Admixtures of hydrated lime and crushed bricks also have an acceptable colour from an aesthetic point of view. This paper concerns a systematic research on the pozzolanicity of different bricks and clays. The laboratory tests were based on chemical, mineralogical-petrographical analyses and pozzolanicity tests, applied to measure the capacity of crushed bricks in fixing calcium hydrate (pozzolanicity). Various types of clay, calcinated at different temperatures, are subjected to the pozzolanicity test in order to state the degree of pozzolanicity. The research intends to give guidelines for the production and use of pozzolanic bricks and clays for the preparation of hydraulic mortars and grouts.
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