Papers by Ioannis Ioannou
The conservation of 20 th century concrete heritage structures poses a major challenge worldwide.... more The conservation of 20 th century concrete heritage structures poses a major challenge worldwide. Whilst these structures possess a remarkable architectural value and a rather experimental character in terms of the use of materials and technologies, at the same time there is admittedly lack of recognition of their cultural and historical value by the wide public. More often than not, such buildings are left to deteriorate and often they are even demolished. This paper follows the workings of the project "CONSErvation of 20 th century concrete Cultural Heritage in urban changing environments" (CONSECH20). The aforementioned international interdisciplinary project aims to investigate concrete constructions built until 1965 in four different European countries (Cyprus, Italy, The Netherlands and the Czech Republic), in terms of their architectural, social and historical value, and to address their restoration and re-use potential. The paper initially presents the significance of 20 th century concrete heritage structures in general, and describes the methodology proposed in order to ensure the protection of such buildings from demolition, and facilitate their restoration and re-use (if and where possible) for the benefit of the society. The focus is on the structural assessment and restoration of 20 th century concrete heritage buildings in Cyprus, following the methodologies described by modern codes for the assessment and retrofit of existing concrete structures. A new practical analysis approach is described and compared to the force-control approach of the pushover analysis of Eurocode 8:3, which significantly overestimates the demands for seismic upgrading. The two aforementioned approaches are examined for a specific case study concrete heritage building in Nicosia, Cyprus.
Construction materials, Nov 10, 2022
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Processes, Apr 14, 2021
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
E3S web of conferences, 2023
Earth-based building materials have been used since antiquity for the construction of various str... more Earth-based building materials have been used since antiquity for the construction of various structures. The main drawback of these materials is their vulnerability to direct contact with liquid water, such as rising damp. To protect earthen structures from rising damp, a stone foundation was used, resulting in composite masonry. In the current study, an experimental investigation of the capillary absorption of nonstabilized CEBs produced with soils sourced from different areas of Cyprus, as well as of 2-layer composite building materials comprising of natural stone and CEBs was carried out. The tests on CEBs indicated that the use of water as the wetting liquid led to the disintegration of the specimens and consequently to nonlinear response. Thus, a non-reactive liquid was used instead to measure the capillary absorption coefficient of the materials. The test results showed that the capillary absorption coefficient of CEBs varied between 140-260 gr/m 2 sec 1/2. In the case of the composites, capillary absorption with water as the wetting liquid showed perfectly linear response, following the t 1/2 law, with no disintegration of the specimens. The results showed that there are two distinct capillary absorption branches with different gradients, in line with the theory of capillary absorption into 2-layer composite materials.
Compressed Earth Blocks (CEBs) have been attracting increasing research interest recently, becaus... more Compressed Earth Blocks (CEBs) have been attracting increasing research interest recently, because of their low embodied energy, compared to other contemporary building materials. The aim of this study is to examine the effect of wind-driven rain on non-stabilized CEBs produced in Cyprus. To that extent, five soils sourced from different areas of Cyprus were used to produce CEBs, whilst the spray erosion test was conducted to assess the resistance of the end-products against water-mediated weathering. Furthermore, durability design for different areas of Cyprus was carried out for a specific earthen structure, in order to correlate the results of the spray erosion test with the desired durability specifications of CEBs for construction. The findings suggest that the majority of CEBs produced in Cyprus can be used in contemporary earthen architecture. Peer-review under the responsibility of the organizing committee of the ICMB23.
Materials and Structures
The scope of this collective paper produced in the frame of RILEM TC 277-LHS is to provide sound ... more The scope of this collective paper produced in the frame of RILEM TC 277-LHS is to provide sound knowledge on the use of additives/admixtures in lime-based mortars, based on literature and practice. The most widely known additives/admixtures are systematically presented. Their main effects and testing of their performance have been properly tabulated. It is well known that a plethora of additives/admixtures are produced every year by chemical industries. However, when using them in lime-based mortars, compatibility and durability aspects are of primary importance. The introduction of additives/admixtures in lime mortars was imposed by the need to improve important properties of these composites in the fresh and hardened state, namely, workability, durability, early-age and long-term strength and to reduce defects, such as shrinkage and long setting time. In this review paper, the terminology proposed by EN 16572 is followed, designating additive as a constituent added in small quant...
Compressed Earth Blocks (CEBs) have been attracting increasing research interest recently, becaus... more Compressed Earth Blocks (CEBs) have been attracting increasing research interest recently, because of their sustainable nature. However, their poor performance against water-mediated weathering is still considered to be a major drawback for contemporary architecture. The aim of this study is to enhance the durability of non-stabilized CEBs produced in Cyprus by optimizing their granular composition. To that end, two locally sourced soils and a fine crushed aggregate were used to produce several CEBs. Spray erosion, drip and capillary absorption tests were carried out to test the performance of these CEBs against liquid ingress. The results suggest that the addition of sand can significantly improve the durability of non-stabilized CEBs against water action. Peer-review under the responsibility of the organizing committee of the ICMB21.
Materials and Structures
Salt crystallization is a major cause of damage in porous building materials. Accelerated salt we... more Salt crystallization is a major cause of damage in porous building materials. Accelerated salt weathering tests carried out in the laboratory are among the most common methods to assess the durability of material to salt decay. However, existing standards and recommendations for salt weathering tests have limitations in terms of effectiveness and/or reliability. In the framework of the RILEM Technical Committee 271-ASC, a procedure has been developed which proposes a new approach to salt crystallization tests. It starts from the consideration that salt damage can be seen as a process developing in two phases: accumulation of the salt in the material and propagation of the decay. In the first phase, salts are introduced in the material and accumulate close to the evaporation surface, while in the second phase damage propagates because of repeated dissolution and crystallization cycles, induced by re-wetting with liquid water and by relative humidity changes. In this paper, the proced...
Zenodo (CERN European Organization for Nuclear Research), Apr 28, 2023
This paper presents experimental results for the characterization of masonry materials from the B... more This paper presents experimental results for the characterization of masonry materials from the Byzantine Monastery of Panagia Apsinthiotissa in Cyprus. Stone samples obtained from the monument were subjected to laboratory tests to determine their apparent density, capillary absorption coefficient and compressive strength. Furthermore, XRD analysis of stone, brick and fractionated mortar samples was performed to investigate the materials' mineralogy. Micro-destructive drilling tests and non-destructive rebound hammer and Karsten tube absorption tests were also undertaken in situ aiming to enrich the database of information regarding the properties of the stones and bricks. The experimental data point towards the use of locally sourced building stones and mortar aggregates. The use of lime-based mortars with additions for improving their setting properties and for imparting hydraulicity to the composites was identified. The properties of the bricks were found to be influenced by their composition and variable degree of deterioration. The study is a contribution to systematic efforts for the preservation of the cultural heritage of Cyprus in the context of the peacebuilding process supported by the United Nations and the European Union.
Hygrothermal Performance of Adobe Structures
IOP conference series, Jun 1, 2023
Vernacular architecture incorporates many cooling and heating passive design strategies related t... more Vernacular architecture incorporates many cooling and heating passive design strategies related to the structural envelope, the different architectural arrangements and the way of living of the inhabitants. Adobe walls are considered to be high thermal mass masonries, as they have the ability to store thermal energy. The high thermal inertia of these materials regulates indoor temperature variations through considerable time lags, thus contributing to the improvement of thermal comfort conditions. This study deals with the environmental behaviour of an adobe historic building in the rural area of Nicosia, Cyprus. The aim of this study is the investigation of the hygrothermal performance of the external adobe masonry walls of the structure under study. For this purpose, in-situ long-term monitoring is currently being carried out, focusing on the indoor and outdoor environmental conditions of a south wall of a room which has two exposed surfaces, the north towards the street and the south towards a courtyard. The south wall is being monitored with temperature/moisture sensors, installed at various locations along its thickness and height. In situ monitoring is complemented with laboratory measurements of the thermophysical (thermal conductivity, porosity, and sorptivity) properties of the main masonry material (adobes). Rising damp height, time of wetness, thermal inertia and decrement factor have all been calculated based on the laboratory and in-situ measurements. The results are analysed in terms of existing standards and analytical equations. The findings of this research may be used to evaluate the overall thermal performance of historic adobe buildings and the effectiveness of adobe walls in the improvement of indoor comfort conditions.
Construction and Building Materials, Dec 1, 2015
The adoption of any binder system for structural concrete depends on the performance characterist... more The adoption of any binder system for structural concrete depends on the performance characteristics desired for addressing the long-term deformation and durability concerns. The major properties influencing the performance includes the shrinkage characteristics governing the long-term deformation, and durability characteristics related to various transport mechanisms, governing the performance in different service conditions. This paper describes the potential of Limestone Calcined Clay Cement (LC 3) for use in structural concrete in comparison with Ordinary Portland Cement (OPC) and fly ash based blended cement (FA30). Three types of concrete mixtures were designed for the study, two based on achieving an equivalent strength grade (M30 and M50 concrete grade) with each binder, and the third with equal binder content and w/b ratio. Mechanical properties such as compressive strength and elastic modulus, and autogenous and drying shrinkage, along with various durability parameters of the different concretes were assessed. Oxygen permeability, rapid chloride penetration, chloride migration, resistivity development and water sorptivity were the various parameters considered for evaluation of durability performance. The results indicate the superiority of LC 3 binder over other binders in producing durable concrete, especially in a chloride laden environment. The major reason for the better performance was attributed to the more compact and dense microstructure of the system with the LC 3 binder against OPC and FA30. The drying shrinkage performance was seen to be similar for concrete with all three binders.
Energy, Dec 1, 2019
The present study examines the overall assessment of a novel environmentally responsive modular m... more The present study examines the overall assessment of a novel environmentally responsive modular masonry wall system (EcoBrick). The system consists of modular construction components that are produced using an eco-friendly mix design, in which 50% w/w of the binder and aggregate are replaced by waste materials and industrial by-products. Steady-state and transient heat numerical analyses are carried out to determine the system's thermal performance, i.e. U-value, time lag and decrement factor, while data from the literature are used to assess its environmental impact in terms of embodied energy and carbon. The results are compared against corresponding data referring to common contemporary construction systems. The overall efficiency of the proposed building solution is further evaluated via a comparative qualitative analysis of various aspects associated with construction practices, in-service use and aesthetic quality. The outcomes obtained indicate that the novel masonry system EcoBrick hereby examined has excellent prospects and can be effectively adopted by the building industry, provided that a higher technological matureness level is attained.
The classification of a concrete mixture as self-compacting (SCC) is performed by a series of emp... more The classification of a concrete mixture as self-compacting (SCC) is performed by a series of empirical characterization tests that have been designed to assess not only the flowability of the mixture but also its segregation resistance and filling ability. The objective of the present work is to correlate the rheological parameters of SCC matrix, yield stress and plastic viscosity, to slump flow measurements. The focus of the slump flow test investigation was centered on the fully yielded flow regime and an empirical model relating the yield stress to material and flow parameters is proposed. Our experimental data revealed that the time for a spread of 500 mm which is used in engineering practice as reference for measurement parameters, is an arbitrary choice. Our findings indicate that the non-dimensional final spread is linearly related to the non-dimensional yield-stress. Finally,there are strong indications that the non-dimensional viscosity of the mixture is associated with the non-dimensional final spread as well as the stopping time of the slump flow; this experimental data set suggests an exponential decay of the final spread and stopping time with viscosity.
Infrastructures
Historic concrete buildings are at risk. Limited knowledge of concrete technology until the 1960s... more Historic concrete buildings are at risk. Limited knowledge of concrete technology until the 1960s led to more sensitive buildings than modern concrete buildings. In addition, the lack of sensibility regarding their heritage value and insufficient protection is leading to remorseless demolition. Still, concrete has proved to be a resilient material that can last over a century with proper care. There is not yet an estimation of the status of historic concrete buildings in Europe. Until now, a few attempts have been done to secondarily, and subjectively, gauge their conservation status. This paper is the result of a joint investigation studying forty-eight historic concrete buildings distributed in four countries. They were surveyed by expert teams according to a predefined methodology. The study aims to identify recurrent damages and parameters affecting the conservation state. It also aims to serve as the first trial for an objective and measurable methodology, to apply it with a st...
12th International Conference on Structural Analysis of Historical Constructions, 2021
This paper presents an interdisciplinary study concerning the documentation and structural apprai... more This paper presents an interdisciplinary study concerning the documentation and structural appraisal of a Medieval Manor located in Potamia, Cyprus. The case study monument is an impressive complex of masonry structures, part of which is nowadays in ruins. A comprehensive review of historical sources was carried out in order to obtain data concerning the history and construction evolution of the Manor. It was verified that the monument incorporates different building phases dating from the 14 th to the 20 th century. Architectural typology and construction detailing was examined via in-situ investigations and topographic surveys. These enabled the identification of the elements composing the structural system. The latter consists of a combination of stone and adobe masonry load-bearing walls, upon which timber floors and roofs rest. Extensive field work was undertaken to explicitly map the various agents of pathology. Significant structural damage was detected, including partial col...
Investigating the Thermal Properties of Earth-Based Materials: The Case of Adobes
10th International Symposium on the Conservation of Monuments in the Mediterranean Basin, 2018
Earth-based materials have been receiving a growing interest in recent years due to their “redisc... more Earth-based materials have been receiving a growing interest in recent years due to their “rediscovery” as eco-friendly building materials with great potential to increase energy efficiency. Despite this interest, however, there is a lack of reliable scientific research data regarding the thermal properties of earth-based materials, which would allow a deeper understanding of their environmental performance. This work reviews current approaches on the thermal properties of adobes, and their variation with density, through a comparative study of the literature and experimental results. The literature data presented in this paper have been taken from national earth construction-related standards and normative documents, technical documents, and scientific research studies. The experimental research includes measurements of the thermal properties of six adobe test samples produced in the lab using different types and proportions of fiber additives. Through this study it is demonstrated that adobes may need further improvements in terms of thermal insulation capacity to meet the current Cyprus thermal building regulations. A deeper understanding and further research on the dynamic thermal characteristics of earth-based materials, however, are needed in order to achieve a more accurate evaluation of the thermal performance of earthen buildings. Research results further indicate that the thermal properties of earth-based materials are highly correlated to their density. By altering density accordingly, the heat storage and insulating capacity of adobes can be “manipulated” in order to achieve compliance with national thermal regulations.
Construction and Building Materials, 2021
h i g h l i g h t s A procedure for accumulating salts at the surface of porous materials is prop... more h i g h l i g h t s A procedure for accumulating salts at the surface of porous materials is proposed. Most of the salt is concentrated in the first millimetres of the subsurface. The measurement of the salt distribution is crucial in salt crystallisation tests.
Recent challenges faced by humanity in relation to the ongoing climatic changes around the globe,... more Recent challenges faced by humanity in relation to the ongoing climatic changes around the globe, have led many practitioners and researchers search for new environmentally friendly materials to use in construction, such as earth-based materials. A specific form of an earth-based building material that nowadays receives particular attention is Compressed Earth Blocks (CEBs). CEBs comprise of soil mixed at low moisture content and are formed under high pressure in compression, without firing. The end-products can be non-stabilized, i.e., without any cement or lime added, or stabilized, whereby a small quantity of stabilizer (<12% by weight) is added, mainly for enhancing their mechanical and durability properties. CEBs, particularly the non-stabilized ones, are considered to be less expensive and environmentally friendlier, compared to the traditional fired clay bricks, due to their lower production cost and excellent recyclability potential, which significantly reduces the end-product's environmental impact.
Construction and Building Materials, 2020
Research has shown that even self-compacting concrete (SCC) mixtures can exhibit the socalled "to... more Research has shown that even self-compacting concrete (SCC) mixtures can exhibit the socalled "top-bar effect" which impacts bond and anchorage. Several instances of conflicting results have nevertheless been published regarding interfacial bond between self-compacting concrete and steel reinforcement. The scope of this paper is to present an experimental methodology for assessing the quality of the interface between self-compacting concrete and ribbed reinforcement. For this purpose, seven different self-compacting and four normally vibrated concrete (NVC) mixtures with diverse rheological characteristics were examined. Digital Image Analysis of cut sections containing reinforcing bars at different cast-heights was used as a diagnostic tool. The study illustrates that the quality of the interface is strongly affected by the viscosity of the SCC mixtures and by the slump values in NVC. Self-compacting concrete mixtures show greater inherent robustness and cohesion at the steel-concrete interface compared to conventionally vibrated concretes.
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Papers by Ioannis Ioannou