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This paper presents a comprehensive approach to elucidate the mechanical and thermal aspects of coating layers integrated with organic-based PCMs. In that respect, three sets of cement mortars were studied experimentally to underline the significance of PCMs proportion. From a mechanical point of view, the strength of specimens cured at 20 °C resulted to be superior compared to 40 °C, with a more evident influence for cement mortars containing PCMs. Laboratory tests on specimens subjected to 50 wetting–drying cycles demonstrated an insignificant increase of the mass for coatings without PCMs and a slight increase for coatings containing PCMs. During this process, growth in strength for the base mix without PCMs and a loss in strength for mixtures with PCMs was exposed; an exponential decay relationship was noted between the compressive strength with the PCM proportion. Alongside this, a transient thermal analysis was carried out to assess the effect of PCMs on the dynamic thermal parameters of coating layers. A higher proportion of PCM ingredients leads to enhanced responsiveness since the heat wave penetrating the layer is smoothen and delayed. These issues can adequately address the defensive behaviour capacity of building components, without surpassing their carrying structural stability and mechanical properties.
K.J. Kontoleon; M. Stefanidou; S. Saboor; D. Mazzeo; A. Karaoulis; D. Zegginis; D. Kraniotis. Defensive behaviour of building envelopes in terms of mechanical and thermal responsiveness by incorporating PCMs in cement mortar layers. Sustainable Energy Technologies and Assessments 2021, 47, 101349 .
AMA StyleK.J. Kontoleon, M. Stefanidou, S. Saboor, D. Mazzeo, A. Karaoulis, D. Zegginis, D. Kraniotis. Defensive behaviour of building envelopes in terms of mechanical and thermal responsiveness by incorporating PCMs in cement mortar layers. Sustainable Energy Technologies and Assessments. 2021; 47 ():101349.
Chicago/Turabian StyleK.J. Kontoleon; M. Stefanidou; S. Saboor; D. Mazzeo; A. Karaoulis; D. Zegginis; D. Kraniotis. 2021. "Defensive behaviour of building envelopes in terms of mechanical and thermal responsiveness by incorporating PCMs in cement mortar layers." Sustainable Energy Technologies and Assessments 47, no. : 101349.
Brick residues, such as brick dust and crushed brick, have been diachronically used in historic mortars, both as binders and aggregates. Their application served as a mean to increase the pozzolanicity of the matrixes, enhancing resistance to humidity, decrease the density of the mixtures and add special hue to the structures. On the other hand, the performance of traditional mortars at elevated temperatures is a significant aspect that should be taken into account, in order to assess the preservation state and residual capacity of historic structures, as well as to design fire resistant restoration materials, under the prism of compatibility. In this study, three mortar series were manufactured, based on lime (L), lime : natural pozzolan (LP-1:1 by weight), lime : natural pozzolan : brick dust (LPB-1:0.8:0.2 by weight). In order to envisage the role of crushed brick in the matrix, they substituted the 40% of natural aggregates in the same gradation (0–8 mm). The physico-mechanical properties of the mortars were tested at 28 and 90 days, while they were further exposed at elevated temperatures, concerning 200 °C, 400 °C, 600 °C, 800 °C and 1000 °C. Their post fire properties (physico-mechanical, microstructural) were recorded, so as to identify the preferable testing age of lime-based mortars and the impact of brick residues on their behavior. From the evaluation of the results, it was asserted that the 90d age seems to be more representative, while crushed brick and brick dust enhanced structural integrity throughout extreme temperatures.
Vasiliki Pachta; Stavroula Konopisi; Maria Stefanidou. The influence of brick dust and crushed brick on the properties of lime-based mortars exposed at elevated temperatures. Construction and Building Materials 2021, 296, 123743 .
AMA StyleVasiliki Pachta, Stavroula Konopisi, Maria Stefanidou. The influence of brick dust and crushed brick on the properties of lime-based mortars exposed at elevated temperatures. Construction and Building Materials. 2021; 296 ():123743.
Chicago/Turabian StyleVasiliki Pachta; Stavroula Konopisi; Maria Stefanidou. 2021. "The influence of brick dust and crushed brick on the properties of lime-based mortars exposed at elevated temperatures." Construction and Building Materials 296, no. : 123743.
The performance of building materials at extreme temperatures is a significant parameter taken into account, in order to apply fire safety criteria in constructions. In this study, various flame retardants (aluminum tri-hydroxide/Al(OH)3, magnesium hydroxide/Mg(OH)2, nano-clay) were used as additives in cement mortars, in order to evaluate their impact at high temperatures. The mortar specimens were exposed at 200, 400, 600, 800 and 1000 °C and their physico-mechanical characteristics (mass and volume loss, porosity, water absorption, specific gravity, dynamic modulus of elasticity, flexural- compressive strength) were studied. Additionally, their mineralogical (X-Ray diffraction), thermal (Thermogravimetric/Differential Thermogravimetric analysis (TG-DTG), Differential Scanning Calorimetry (DSC)) and microstructure (scanning electron microscopy) properties were recorded. The results indicated the positive role of additives in the mortar matrix, especially when they were combined. In particular, the combination of nano-clay with Al(OH)3 or Mg(OH)2 increased the resistance to flexure up to 1000 °C, while the mass and volume loss was also retained. The beneficial role of the Al(OH)3 and Mg(OH)2 addition in cement mortars exposed up to 600 °C, was documented in the experimental results.
Vasiliki Pachta; Eirini-Chrysanthi Tsardaka; Maria Stefanidou. The role of flame retardants in cement mortars exposed at elevated temperatures. Construction and Building Materials 2020, 273, 122029 .
AMA StyleVasiliki Pachta, Eirini-Chrysanthi Tsardaka, Maria Stefanidou. The role of flame retardants in cement mortars exposed at elevated temperatures. Construction and Building Materials. 2020; 273 ():122029.
Chicago/Turabian StyleVasiliki Pachta; Eirini-Chrysanthi Tsardaka; Maria Stefanidou. 2020. "The role of flame retardants in cement mortars exposed at elevated temperatures." Construction and Building Materials 273, no. : 122029.
The present study aims to record the influence of nano-particles on the durability of cement and lime pastes exposed to salt cycles. As salts are a significant pathology factor for materials exposed to marine or other corrosive environments, the influence of nano-technology towards the protection of materials is of great importance. The incorporation of nano-silica (NS) and nano-alumina (NA) in cement and lime pastes influenced the physic-mechanical properties and the behavior of the pastes through the salt cycles. NA provoked compressive strength increment, open porosity reduction and water absorption in lime pastes at 90 and 180 days. Additionally, it allowed the enhancement of compressive strength after sodium sulfate cycles. XRD (X-Ray Diffraction) analysis and ATR (Attenuated Total Reflectance) spectroscopy contributed to the explanation of the high compressive strength recorded after the sodium sulfate cycles of NA-modified lime pastes. In case of cement pastes, NS favoured the compressive strength after the sea water and sodium sulfate cycles. Moreover, NA aided the enhancement of the properties of the pastes in the latter conditions.
Eirini-Chrysanthi Tsardaka; Maria Stefanidou. Testing nano-silica and nano-alumina additions for enhancing the durability of cement and lime pastes. Materials Today: Proceedings 2020, 37, 4082 -4090.
AMA StyleEirini-Chrysanthi Tsardaka, Maria Stefanidou. Testing nano-silica and nano-alumina additions for enhancing the durability of cement and lime pastes. Materials Today: Proceedings. 2020; 37 ():4082-4090.
Chicago/Turabian StyleEirini-Chrysanthi Tsardaka; Maria Stefanidou. 2020. "Testing nano-silica and nano-alumina additions for enhancing the durability of cement and lime pastes." Materials Today: Proceedings 37, no. : 4082-4090.
The present study proposes nano-calcium oxide (NC) and nano-silica (NS) particles as healing agents in cement pastes, taking into account the curing conditions. Two series of specimens were treated in water and under wetting-drying cycles. The addition of NC (1.5%wt of binder) triggered early healing since cracks were healed within 14 days in underwater immersion and before 28 days at wetting-drying cycles. Attenuated Total Reflectance (ATR) spectroscopy and SEM analysis revealed that the healing products were mainly aragonite and calcite in water conditions and more amorphous carbonates under wetting-drying cycles. The combination of NS and NC (3.0%wt in total) offered healing under both curing conditions before 28 days. The presence of NS assisted toward porosity refinement and NC increased the carbonates’ content. The newly formed material was dense, and its elemental analysis by SEM revealed the C-S-H compounds that were also verified by ATR.
Maria Stefanidou; Eirini-Chrysanthi Tsardaka; Aspasia Karozou. The Influence of Curing Regimes in Self-Healing of Nano-Modified Cement Pastes. Materials 2020, 13, 5301 .
AMA StyleMaria Stefanidou, Eirini-Chrysanthi Tsardaka, Aspasia Karozou. The Influence of Curing Regimes in Self-Healing of Nano-Modified Cement Pastes. Materials. 2020; 13 (22):5301.
Chicago/Turabian StyleMaria Stefanidou; Eirini-Chrysanthi Tsardaka; Aspasia Karozou. 2020. "The Influence of Curing Regimes in Self-Healing of Nano-Modified Cement Pastes." Materials 13, no. 22: 5301.
The need to increase the durability of clay-based materials, due to their inherent low strength and vulnerability in contact with water, led researchers to examine different options. In this paper, clay mortars were produced using four different activating solutions. Alkali hydroxides, alkali carbonates, and alkali silicates activating solutions were used. Interest is given to long term properties while their behavior to wetting–drying and freeze–thaw cycles is recorded. In total, the results of the experiments indicated the positive effect of the potassium metasilicate on mechanical characteristics presenting, however, low performance at wetting–drying. The combination of sodium metasilicate with sodium hydroxide solution has also presented a positive effect on both mechanical and physical properties. In contrast, sodium carbonate acted better in enhancing physical properties and granting water-resistant abilities. Moreover, the performance of the specimens mixed with water–glass addition presented excellent volume stability and low mass loss in durability tests.
Aspasia Karozou; Stavroula Konopisi; Eleni Pavlidou; Maria Stefanidou. Long-Term Behavior and Durability of Alkali-Activated Clay Mortars. Materials 2020, 13, 3790 .
AMA StyleAspasia Karozou, Stavroula Konopisi, Eleni Pavlidou, Maria Stefanidou. Long-Term Behavior and Durability of Alkali-Activated Clay Mortars. Materials. 2020; 13 (17):3790.
Chicago/Turabian StyleAspasia Karozou; Stavroula Konopisi; Eleni Pavlidou; Maria Stefanidou. 2020. "Long-Term Behavior and Durability of Alkali-Activated Clay Mortars." Materials 13, no. 17: 3790.
Multilayer mortar systems have been diachronically used in historic structures. Renders and plasters were usually based on lime and presented specific characteristics (i.e. stratigraphy), while their durability was mostly attributed to the adhesion and overall performance of the mortar layers. During restoration works, the replacement or repair of successive mortar layers (i.e. renders, plasters, mural paintings’ substrates) is a common practice, whose effectiveness is closely related to the proper materials and techniques applied. In this paper, an effort was made to enhance the properties of a double-layered mortar system, based on lime and natural pozzolan. To this direction, pre-wetting of the internal layer was performed, using various organic and inorganic water-solutions (lime wash, primal, hydroground) that were further nano-modified (1.5% w/w, nano-silica). A series of specimens were manufactured and their physico-mechanical properties were tested at the age of 28 and 90 days (porosity, apparent specific gravity, water absorption coefficient, vapor permeability, dynamic modulus of elasticity, flexural and compressive strength). Additionally, bond strength by pull off and tensile bond strength were performed. From the evaluation of the results, it was concluded that the application of the proposed nano-modified solutions improved significantly the adhesion of the mortar layers. The results were encouraging, indicating that a limited, low cost and non invasive technique, could enhance their performance, during restoration works.
Vasiliki Pachta; Chrysoula Serpezoudi; Maria Stefanidou. The influence of pre-wetting with consolidants on the adhesion of double-layer lime based mortars. Journal of Cultural Heritage 2020, 46, 21 -30.
AMA StyleVasiliki Pachta, Chrysoula Serpezoudi, Maria Stefanidou. The influence of pre-wetting with consolidants on the adhesion of double-layer lime based mortars. Journal of Cultural Heritage. 2020; 46 ():21-30.
Chicago/Turabian StyleVasiliki Pachta; Chrysoula Serpezoudi; Maria Stefanidou. 2020. "The influence of pre-wetting with consolidants on the adhesion of double-layer lime based mortars." Journal of Cultural Heritage 46, no. : 21-30.
The self‐healing mechanism of cementitious materials has been investigated by many researchers in the last two decades. In the journey of this quest, more and more advanced methods of analyzing the efficiency of healing have been employed. These methods are intended to clarify and quantify the healing mechanism. This paper presents five techniques, which are either common in the microstructure and nanostructure study or innovative in this field, which was used in order to identify the healing efficacy. Specifically, the application of scanning electron microscope (SEM) analysis, 3‐D ultrasound tomography, nanoindentation, water absorption test (sorptivity), and software development in the Python programming environment for monitoring the crack closure have been used. The main objective of this study was to quantify several parameters, such as the geometry of the cracks, the properties of the healing products, as well as the healing depth. SEM analysis is a well‐known technique that can contribute to identify the elements of the healing products and give the morphology of the surface. The methodology for nondestructive 3‐D ultrasound tomography of healed specimens clarifies the ability of healing in depth. The nanoindentation technique enables localized contact response, which allows accurate estimates of the nanomechanical properties of the tested areas. The absorption method (sorptivity) is a representative method of recording cracks and open porosity. The software developed in a Python programming environment aimed at quantifying the surface crack closure and is an attempt to minimize the parameters that affect the inaccurate results, usually caused by the program's inability to detect only the crack. In addition, the results of each of the above methods are also presented, and their contribution to the study of healing is analyzed.
Maria Stefanidou; Evangelia Tsampali; Georgios Karagiannis; Stamatios Amanatiadis; Andreas Ioakim; Spyridon Kassavetis. Techniques for recording self‐healing efficiency and characterizing the healing products in cementitious materials. Material Design & Processing Communications 2020, 1 .
AMA StyleMaria Stefanidou, Evangelia Tsampali, Georgios Karagiannis, Stamatios Amanatiadis, Andreas Ioakim, Spyridon Kassavetis. Techniques for recording self‐healing efficiency and characterizing the healing products in cementitious materials. Material Design & Processing Communications. 2020; ():1.
Chicago/Turabian StyleMaria Stefanidou; Evangelia Tsampali; Georgios Karagiannis; Stamatios Amanatiadis; Andreas Ioakim; Spyridon Kassavetis. 2020. "Techniques for recording self‐healing efficiency and characterizing the healing products in cementitious materials." Material Design & Processing Communications , no. : 1.
Using recycling materials in construction is a safe way for achieving sustainability. Although European policy, through directives given, supports their use and coherent research results derive from the scientific society, their use in practice is limited. It is generally accepted that the use of alternative construction materials with low environmental impact and of low cost is an important issue. As a part of the integration in sustainable development approach, the eco-friendly materials present a great interest in building construction manufacturing. Towards this direction, many studies have been focused on the exploitation of natural fibers as reinforcements in building materials. This study is an attempt to add more experimental results by the use of bio-fibers to building materials in order to ensure the performance of recycled materials such as bio-fibers in the construction sector. Three types of natural fibers jute, coconut and kelp were used as additives in 1.5% by mortar volume. Their role in cement and lime mortars was recorded by testing mechanical, physical and microstructure properties. The results indicate that natural fibers act in favor of strength and durability. Nevertheless, bio-fibers work differently in strong cement mortars in relation to the “soft” lime-based materials. Advantages can be gained in both cases but certain aspects should be taken into account such as the adhesion to the mortar matrix and the water content of the mixture.
Fotini Kesikidou; Maria Stefanidou. Natural fiber-reinforced mortars. Journal of Building Engineering 2019, 25, 100786 .
AMA StyleFotini Kesikidou, Maria Stefanidou. Natural fiber-reinforced mortars. Journal of Building Engineering. 2019; 25 ():100786.
Chicago/Turabian StyleFotini Kesikidou; Maria Stefanidou. 2019. "Natural fiber-reinforced mortars." Journal of Building Engineering 25, no. : 100786.
Grouting is a widely used intervention technique for the consolidation and strengthening of historic masonries. During the recent decades, lime-based grouts have been developed, tested and applied, taking into account parameters, such as their compatibility with the historic structures and their performance both in terms of fresh and hardened state properties. The exploitation of perlite by-products on the other hand (named as ‘waste perlite’), is a field that should be further envisaged, due to the gradually increasing demand of expanded perlite production, as well as the need of minimizing the environmental burden from its industrial process. To this direction, a series of grout mixtures based on two types of perlite by-products (D1S and D1C) and lime (air and hydraulic) were manufactured and tested. According to the experimental results, waste perlite-based grouts presented effaceable fresh and hardened state properties, while their performance was enhanced when superplasticizer and a short proportion of white cement or metakaolin was added in the air lime mixtures. In the hydraulic lime mixtures, the addition of waste perlite enhanced their properties and significantly increased their strength. Therefore, it was concluded that according to specific requirements, both perlite by-products studied could be used in combination with lime, for the manufacture of light-weight, low cost and environmental friendly grouts. Future oriented research should be therefore made in order to further investigate the parameters influencing the performance of grouts based on other waste perlite types.
Vasiliki Pachta; Fotis Papadopoulos; Maria Stefanidou. Development and testing of grouts based on perlite by-products and lime. Construction and Building Materials 2019, 207, 338 -344.
AMA StyleVasiliki Pachta, Fotis Papadopoulos, Maria Stefanidou. Development and testing of grouts based on perlite by-products and lime. Construction and Building Materials. 2019; 207 ():338-344.
Chicago/Turabian StyleVasiliki Pachta; Fotis Papadopoulos; Maria Stefanidou. 2019. "Development and testing of grouts based on perlite by-products and lime." Construction and Building Materials 207, no. : 338-344.
In the present paper different external surface treatments published in the literature as preventive solutions for improving the performance of existing concrete constructions are presented and discussed. They are categorized as repair materials for concrete conservation, protection surface methods against moisture and aggressive agent penetration, injection techniques for crack sealing and preventive repair solutions with smart functionalities. In a final section, the most extended testing methods for evaluating the effectiveness of the different repair solutions are summarized depending on the property to be enhanced: moisture control and resistance against penetration of aggressive agents. The review shows that although several possibilities exist for the repair of the existing constructions, there is a lack of comparative analysis between the different methodologies. SARCOS COST Action CA15202 stablishes as scientific objectives to carry out comparative studies including the most advanced solutions for the external repair of concrete, giving criteria for effectiveness assessment and defining robust and reliable methods for charactering the performance of the repaired structures.
M. Sánchez; P. Faria; L. Ferrara; E. Horszczaruk; H.M. Jonkers; A. Kwiecień; J. Mosa; A. Peled; A.S. Pereira; D. Snoeck; M. Stefanidou; T. Stryszewska; Bogusław Zając. External treatments for the preventive repair of existing constructions: A review. Construction and Building Materials 2018, 193, 435 -452.
AMA StyleM. Sánchez, P. Faria, L. Ferrara, E. Horszczaruk, H.M. Jonkers, A. Kwiecień, J. Mosa, A. Peled, A.S. Pereira, D. Snoeck, M. Stefanidou, T. Stryszewska, Bogusław Zając. External treatments for the preventive repair of existing constructions: A review. Construction and Building Materials. 2018; 193 ():435-452.
Chicago/Turabian StyleM. Sánchez; P. Faria; L. Ferrara; E. Horszczaruk; H.M. Jonkers; A. Kwiecień; J. Mosa; A. Peled; A.S. Pereira; D. Snoeck; M. Stefanidou; T. Stryszewska; Bogusław Zając. 2018. "External treatments for the preventive repair of existing constructions: A review." Construction and Building Materials 193, no. : 435-452.
The dispersity of silica particles affects their influence in a composite. In this work, a solution for silica fume (SF) dispersion is proposed for application in cement mixtures, as de-agglomeration method. Sodium bicarbonate salt solution 0.01 M pH 13, with addition of SF consist the proposed dispersion (SBCS). The solution has low cost it is stable, easy and quick to be prepared and does not require special equipment. Dispersion was characterized using particle size distribution and ATR. Cement pastes with ultrasonicated colloidal suspension of SF in water (US) and with sodium bicarbonate - SF (CDS) are compared. DTA-TG, XRD analysis and SEM observation, along with the determination of mechanical and physical properties of the produced specimens are reclaimed. SBCS gave illustrative results after subjecting the specimens in durability tests. The results indicated that SBCS can be used to disperse SF affecting positively the microstructure and the macro-properties of cement systems.
Eirini-Chysanthi Tsardaka; Maria Stefanidou. Application of an alternative way for silica fume dispersion in cement pastes without ultrasonication. Cement and Concrete Research 2018, 115, 59 -69.
AMA StyleEirini-Chysanthi Tsardaka, Maria Stefanidou. Application of an alternative way for silica fume dispersion in cement pastes without ultrasonication. Cement and Concrete Research. 2018; 115 ():59-69.
Chicago/Turabian StyleEirini-Chysanthi Tsardaka; Maria Stefanidou. 2018. "Application of an alternative way for silica fume dispersion in cement pastes without ultrasonication." Cement and Concrete Research 115, no. : 59-69.
The aim of this paper was to examine workability of fresh concrete used as material for additive manufacturing. 3D concrete printing is an innovative construction method that promises to be highly advantageous in the construction field in terms of optimizing construction time, cost, design flexibility, error reduction, and environmental aspects. Quality of the final printed structure is significantly affected by the properties of fresh concrete which must possess adequate workability in order to be extruded through an extruder head (printability), maintain its shape once deposited and not collapse under the load of subsequent layers (buildability). In the present paper, workability of fresh concrete used as material for additive manufacturing was measured according to four different tests: flow table, ICAR rheometer, Vicat and an experimental applied in the laboratory by measuring the electric power consumption of the motor that rotates the screw extruder. By measuring a wide range of mixtures produced with different aggregates (limestone, river sand, combination of both) and binders (cement, fly ash, ladle furnace slag), printing them with a printing system with screw extruder and setting printable criteria, the range of printability was obtained. Flow table test was more consistent in relation to the other methods used. Printability range was found between 18 and 24 cm (flow table values). Time after mixing for moving from the upper limit to the lower was also measured and was highly depended on the type of aggregates and binders used. A maximum of 30 minutes was obtained without using any retarder additives. Electric power consumption was considered as a parameter of measuring real-time workability of the mixture, making it possible to modify it on time in real scale applications by adding chemical additives during printing. Regarding hardened concrete properties, density of concrete was measured, between 1.9 and 2.1 g/cm³, depending on the aggregate and binder. Compressive strength and Ultrasonic Pulse Velocity are significantly affected by the type and proportions of raw materials in the mixtures.
M. Papachristoforou; V. Mitsopoulos; M. Stefanidou. Evaluation of workability parameters in 3D printing concrete. Procedia Structural Integrity 2018, 10, 155 -162.
AMA StyleM. Papachristoforou, V. Mitsopoulos, M. Stefanidou. Evaluation of workability parameters in 3D printing concrete. Procedia Structural Integrity. 2018; 10 ():155-162.
Chicago/Turabian StyleM. Papachristoforou; V. Mitsopoulos; M. Stefanidou. 2018. "Evaluation of workability parameters in 3D printing concrete." Procedia Structural Integrity 10, no. : 155-162.
The properties and preservation state of historic mortars are closely related to various aspects, such as their constituents and the pathology symptoms they confront, due to extreme environmental conditions or accidental actions (i.e. earthquakes, floods, landslides and fire). Despite the fact that in the recent decades there is extensive research on the impact of elevated temperatures on cement based materials (cement mortars, concrete), there are no relevant studies concerning historic or repair materials. Taken into account that during their service life, historic structures may be subjected to accidental fires (limited or total), the resistance of their building materials to extreme temperatures seems to be a parameter that should be further investigated. To this direction, the paper focuses on the study of a series of lime-based mortars, designed for restoration works, exposed to a range of elevated temperatures starting from 200 °C to 1000 °C. The physico-mechanical properties of the mortar specimens were tested before and after their 2 h maintenance at different temperatures, regarding weight loss, volume change, porosity, apparent specific gravity, dynamic modulus of elasticity, flexural and compressive strength, while macroscopic and microscopic observation was also realised. The evaluation of the results showed that lime-based mortars preserved their structure and characteristics after their exposure to elevated temperatures, while in the case of lime-pozzolan matrix the resistance of the specimens was extremely high, compared to the other binding systems tested.
Vasiliki Pachta; Sofia Triantafyllaki; Maria Stefanidou. Performance of lime-based mortars at elevated temperatures. Construction and Building Materials 2018, 189, 576 -584.
AMA StyleVasiliki Pachta, Sofia Triantafyllaki, Maria Stefanidou. Performance of lime-based mortars at elevated temperatures. Construction and Building Materials. 2018; 189 ():576-584.
Chicago/Turabian StyleVasiliki Pachta; Sofia Triantafyllaki; Maria Stefanidou. 2018. "Performance of lime-based mortars at elevated temperatures." Construction and Building Materials 189, no. : 576-584.
Mosaics were diachronically used as a mean to decorate floors of historic constructions. Their durability and resistance to loading and environmental parameters, was mostly attributed to their substrate, which composed of three to four very well compacted mortar layers. The construction of these substrates usually followed specific requirements and criteria, concerning both the selection of raw materials and the application techniques followed. This paper concerns a systematic study of double-layered mortars, designed and manufactured according to the characteristics found in ancient floor mosaic substrates. Specific parameters were taken into account, such as the binding system, the aggregates’ type and gradation, the Binder/Aggregate (B/A) and Water/Binder (W/B) ratio, as well as the layers’ thickness and the application technique. A series of test were performed at the age of 28, 90 and 180 days. The properties measured concerned porosity, apparent specific gravity, water permeability, capillary absorption, dynamic modulus of elasticity, flexural, compressive strength, while bond strength by pull off and tensile bond strength were conducted. From the evaluation of the results, it was concluded that good compaction and low W/B ratio ensured relatively high compressive strength (5–10 MPa), as well as increased adhesion between the mortar layers, while the addition of brick dust and crushed brick enhanced the layered mortars’ performance.
Vasiliki Pachta; Pinelopi Marinou; Maria Stefanidou. Development and testing of repair mortars for floor mosaic substrates. Journal of Building Engineering 2018, 20, 501 -509.
AMA StyleVasiliki Pachta, Pinelopi Marinou, Maria Stefanidou. Development and testing of repair mortars for floor mosaic substrates. Journal of Building Engineering. 2018; 20 ():501-509.
Chicago/Turabian StyleVasiliki Pachta; Pinelopi Marinou; Maria Stefanidou. 2018. "Development and testing of repair mortars for floor mosaic substrates." Journal of Building Engineering 20, no. : 501-509.
Ancient floor mosaics started to be used from the 2nd millennium BCE, while their structure was established during the Classic Era. From the 4th century BCE they were wide spread and systemized around the Mediterranean Basin, as a mean to decorate public buildings, private houses or open spaces (i.e. atriums). Their substrate, as well as the successiveness of the layers played an important role on their structure, enhancing their durability to environmental factors and external loading. In the present study four multilayer mortar samples from Hellenistic and Roman floor mosaic substrates of monuments from Northern Greece, were analyzed. The methodology concerned in situ, macroscopic and microstructure observation, as well as determination of the physical, mechanical and chemical properties of each layer but at the same time of the structure as a whole. The evaluation of the test results led to the identification of the characteristics of each mortar layer, such as the binding system type, the Binder/Aggregate ratio and the application technique followed. According to the study, all multilayer samples presented similar characteristics, such as: stratigraphy of four very well compacted layers, whose thickness was decreased towards the surface layer, binding system based on lime and natural pozzolan, increase of the Binder/Aggregate ratio upwards and decrease of aggregates' maximum size and porosity. A significant aspect was the good adhesion of the mortar layers, which was attributed to the layers' compaction, as well as to different technological factors.
Vasiliki Pachta; Maria Stefanidou. Technology of multilayer mortars applied in ancient floor mosaic substrates. Journal of Archaeological Science: Reports 2018, 20, 683 -691.
AMA StyleVasiliki Pachta, Maria Stefanidou. Technology of multilayer mortars applied in ancient floor mosaic substrates. Journal of Archaeological Science: Reports. 2018; 20 ():683-691.
Chicago/Turabian StyleVasiliki Pachta; Maria Stefanidou. 2018. "Technology of multilayer mortars applied in ancient floor mosaic substrates." Journal of Archaeological Science: Reports 20, no. : 683-691.
The effect of microstructure on macroproperties of building materials was the initiation in order to use microscopic techniques for studying the materials’ behavior. Primer role among the different techniques has the scanning electron microscope (SEM) as it provides much information in an easy and understandable way. SEM has been used in almost every study of the last decades, dealing with historic and repair materials to complete the analysis performed. In the case of historic mortars, it is a unique technique as it requires a small representative sample and without any intense treatment important information derived from an almost unknown sample including damage detection, phase identification, and microanalysis. It is usually a complementary method of analysis but a precious one as the gained results from the analysis of old mortars are used for designing compatible repair materials for restoration purposes. In the paper, the long-term use of SEM in studying both old authentic and innovative repair mortars is presented.
Maria Stefanidou; Eleni Pavlidou. Scanning Mortars to Understand the Past and Plan the Future for the Maintenance of Monuments. Scanning 2018, 2018, 1 -8.
AMA StyleMaria Stefanidou, Eleni Pavlidou. Scanning Mortars to Understand the Past and Plan the Future for the Maintenance of Monuments. Scanning. 2018; 2018 ():1-8.
Chicago/Turabian StyleMaria Stefanidou; Eleni Pavlidou. 2018. "Scanning Mortars to Understand the Past and Plan the Future for the Maintenance of Monuments." Scanning 2018, no. : 1-8.
Natural pozzolans were used selectively in combination with lime for the production of mortars used in structures where water tightness was required such as aqueducts, baths, and pipes many centuries ago. Their use in building materials was diachronic. The appreciated properties of mortars containing pozzolans were the increased durability and strength and the dense structure in relation to pure lime mortars. In the present paper, two natural pozzolans from Greece were analyzed systematically in order to record their mineralogical, chemical, morphological and physical properties. These pozzolans were used for the production of repair mortar, and the mechanical and physical properties of the mortars were also recorded. From the results, it is derived that the pozzolans tested were materials of high quality and reactivity and could be used for the production of compatible repair mortars for the restoration of monuments and historic buildings. The elaboration of natural pozzolans by grinding could lead to further increase of their reactivity. From the analysis, valuable criteria could be instituted for the qualitative evaluation of natural pozzolans.
Stefanidou Maria. Use of natural pozzolans with lime for producing repair mortars. Environmental Earth Sciences 2016, 75, 1 .
AMA StyleStefanidou Maria. Use of natural pozzolans with lime for producing repair mortars. Environmental Earth Sciences. 2016; 75 (9):1.
Chicago/Turabian StyleStefanidou Maria. 2016. "Use of natural pozzolans with lime for producing repair mortars." Environmental Earth Sciences 75, no. 9: 1.
The systematic analysis of mortars from monuments or historic buildings and the simultaneous study of the construction environment show that it was common practice to use naturally occurring sand from local rivers or streams for the production of the mortars. There are cases though, mainly on islands, where sands of natural origin were limited, and marine or crushed sands were used possibly after elaboration. In all cases the particle size analysis of old mortar confirms the presence of even distribution of the granules. As regards the design of the repair mortars, there are criteria that should be taken into consideration in order to produce materials with compatible properties. The main properties concerning sands are the grain distribution and maximum size, the color, the content of fines, and soluble salts. The objective of this research is the study of the physical characteristics of the sands such as the sand equivalent, the gradation, the apparent density, the morphology of the grains, their mineralogical composition and the influence of these properties on the behavior of lime mortars, notably the mechanical and physical properties acquired.
Maria Stefanidou. Crushed and River-Origin Sands Used as Aggregates in Repair Mortars. Geosciences 2016, 6, 23 .
AMA StyleMaria Stefanidou. Crushed and River-Origin Sands Used as Aggregates in Repair Mortars. Geosciences. 2016; 6 (2):23.
Chicago/Turabian StyleMaria Stefanidou. 2016. "Crushed and River-Origin Sands Used as Aggregates in Repair Mortars." Geosciences 6, no. 2: 23.
Mortars started to be used as protective coatings (renders) during the Neolithic period (8th millennium BC) and since then they constantly contributed to the longevity and durability of construction. Through centuries, the demands in construction were increased as functional, aesthetic, economic and insulating criteria had to be fulfilled. Into this frame, renders had to play a malty-phase role. In the present work a series of mortars were produced based on white cement and lime as binders and three different aggregate types (river sand, glass spheres available at the market and recycled glass particles from broken bottles, laboratory produced) were tested in order to produce a render with improved properties. Microstructure, physical–mechanical properties and thermal conductivity were measured in the produced mortars in order to explore the possibility of replacing sand from natural resources, with glass particles. The results indicate that a more porous structure is achieved in the case where glass particles are used, improving the thermal behavior of the mortars.
M. Stefanidou; E. Anastasiou; O. Mantziou; E. Mpougla; E. Vasiliou; P. D. Konti; K. Antoniadis. Incorporation of Glass Particles in High-Performance Mortars. Waste and Biomass Valorization 2016, 7, 879 -883.
AMA StyleM. Stefanidou, E. Anastasiou, O. Mantziou, E. Mpougla, E. Vasiliou, P. D. Konti, K. Antoniadis. Incorporation of Glass Particles in High-Performance Mortars. Waste and Biomass Valorization. 2016; 7 (4):879-883.
Chicago/Turabian StyleM. Stefanidou; E. Anastasiou; O. Mantziou; E. Mpougla; E. Vasiliou; P. D. Konti; K. Antoniadis. 2016. "Incorporation of Glass Particles in High-Performance Mortars." Waste and Biomass Valorization 7, no. 4: 879-883.