Buildings

14 pages, 3932 KiB

Open AccessArticle

Evaluation of Residential Buildings Savings for Various Envelope Retrofits and Heating Energy Sources: A Simulation Study

by Radoslav Ponechal, Jozef Jandačka and Pavol Ďurica

Buildings 2024, 14(2), 332; https://doi.org/10.3390/buildings14020332 - 25 Jan 2024

Cited by 2 | Viewed by 973

Abstract

The paper considers the issue of the thermal refurbishment of residential buildings built between 10 and 40 years ago in some European countries. It suggests that, while facade retrofitting is the most effective solution for older dwellings, all actions are equally less effective [...] Read more.

The paper considers the issue of the thermal refurbishment of residential buildings built between 10 and 40 years ago in some European countries. It suggests that, while facade retrofitting is the most effective solution for older dwellings, all actions are equally less effective for newer dwellings built in this millennium. According to the current situation, as society shifts away from the use of fossil fuels, this paper presents the expected energy and financial savings that were calculated using one of four different heating sources. The study shows that the efficiency of the additional thermal retrofitting of the structures is low when the building is heated with a heat pump. The addition of thermal insulation to already well-insulated roofs or floors results in minimal savings of approximately 0.15 kWh per square meter of heated floor area per year. The potential advantage of replacing existing windows with new windows in a top thermal quality was shown. After window replacement, the financial benefits could be twice as high in houses heated by district heating compared to houses heated by gas or a heat pump, including an alternative heat pump with photovoltaics. Full article

(This article belongs to the Special Issue Rehabilitation and Reconstruction of Buildings)

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18 pages, 5800 KiB

Open AccessArticle

Experimental Investigation on the Rehabilitation of RC Flat Slabs Using CFRP Sheets to Enhance Punching Shear Capacity

by Mohammed Qusay Abdul Sahib, Reza Aghayari, Mohammad Javad Moradi and Mehrzad Tahamouli Roudsari

Buildings 2024, 14(1), 153; https://doi.org/10.3390/buildings14010153 - 8 Jan 2024

Cited by 1 | Viewed by 1071

Abstract

In this paper, the feasibility of strengthening a flat column–slab connection within the carbon fiber reinforced polymer (CFRP) has been investigated through experimental study. The experimental program includes a set of nine reinforced concrete flat slab specimens. Three unaltered specimens served as control [...] Read more.

In this paper, the feasibility of strengthening a flat column–slab connection within the carbon fiber reinforced polymer (CFRP) has been investigated through experimental study. The experimental program includes a set of nine reinforced concrete flat slab specimens. Three unaltered specimens served as control slabs, while an additional six samples were strengthened with various CFRP configurations to enhance their shear capacity. The strain distribution, ductility, punching shear resistance, stiffness, and crack formation were studied. The result of experimental studies showed that in the direct method of strengthening in which two layers of unidirectional CFRP sheets were employed in two opposite directions, the ultimate punching shear resistance improved by 64%, 44.7%, and 15.3%, with respect to the location of the column connection, as compared with the control specimens. In the case of using one layer of unidirectional CFRP strips, the punching shear resistance was enhanced by approximately 16% and 39%, considering the configuration of CFRP sheets and the amount of strengthened and adhesive layers used. Following the outcomes of this research, the application of CFRPs in improving the resistance capacity of flat slabs against the punching shear is considerable. The reported outcomes were compared with the latest provisions of ACI to show the efficiency of the presented strengthening. Finally, a parametric study was performed assuming different loading locations to assess the effect of the loading region on the response of RC slabs. Results indicate that approaching the loading location toward the RC slab supports results of an increase in the load-bearing capacity and a reduction in the ductility of the RC slab. Full article

(This article belongs to the Special Issue Rehabilitation and Reconstruction of Buildings)

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22 pages, 10588 KiB

Open AccessArticle

A BIM-Based Method for Structural Stability Assessment and Emergency Repairs of Large-Panel Buildings Damaged by Military Actions and Explosions: Evidence from Ukraine

by Petro Hryhorovskyi, Iryna Osadcha, Andrius Jurelionis, Vladyslav Basanskyi and Andrii Hryhorovskyi

Buildings 2022, 12(11), 1817; https://doi.org/10.3390/buildings12111817 - 30 Oct 2022

Cited by 7 | Viewed by 2962

Abstract

The article presents the results of analysis and perspectives for the application of Building Information Modeling (BIM) for the selection of effective organizational, technological, and technical solutions in the elimination of the emergency destruction of large-panel buildings as a result of military actions. [...] Read more.

The article presents the results of analysis and perspectives for the application of Building Information Modeling (BIM) for the selection of effective organizational, technological, and technical solutions in the elimination of the emergency destruction of large-panel buildings as a result of military actions. It has been established that information–mathematical modeling and the usage of a database on typical destructions can improve the work efficiency and safety of the liquidation of emergency destructions of buildings. Moreover, it enables the scaling and identification of the optimal option of emergency stabilization, as well as organizational, technological, and technical actions that have to be urgently taken to prevent the loss of life or collapse of large-panel buildings after massive damage due to shelling and other military actions. Information–mathematical modeling is explored as the key enabler of assessment and decision-making, while typically there is limited access to the survey object and a lack of information about its condition. The case of a large-panel building in Ukraine damaged as a result of a gas explosion was used for the development of the information–mathematical model and for demonstrating the proposed approach. In post-war times, the use of the presented methodology will allow a rapid assessment of the technical condition of buildings and stabilization strategy selection, including the periodicity of monitoring needs and times of repairs. Full article

(This article belongs to the Special Issue Rehabilitation and Reconstruction of Buildings)

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11 pages, 874 KiB

Open AccessArticle

Effect of Microwave Radiation on the Compressive Strength of Solid Ceramic Brick

by David Průša, Karel Šuhajda, Tomáš Žajdlík, Kateřina Svobodová, Stanislav Šťastník, Klara Hobzova and Vaclav Venkrbec

Buildings 2023, 13(4), 1018; https://doi.org/10.3390/buildings13041018 - 13 Apr 2023

Cited by 7 | Viewed by 2495

Abstract

Microwave radiation is widely utilized in construction practice, especially for drying building materials, remediating damp masonry, or sterilization of biotic pests that have infested building structures. The available scientific and technical literature reports that certain materials exposed to microwave radiation do not change [...] Read more.

Microwave radiation is widely utilized in construction practice, especially for drying building materials, remediating damp masonry, or sterilization of biotic pests that have infested building structures. The available scientific and technical literature reports that certain materials exposed to microwave radiation do not change their physical and mechanical properties, although this has not yet been adequately verified. This paper builds on many years of research in the area, adding to and refining existing information, providing new insights into the mechanical and physical properties of commonly available building materials that have been exposed to controlled microwave radiation, and comparing them with reference values. The experimental research on a set of clay brick samples is carried out using tests according to European standards, and it focuses on the effect of microwave radiation on compressive strength and water absorption. The experimental samples were compared to reference samples that had not been subjected to prolonged exposure to moisture and were subsequently treated with microwave radiation for dehumidification. Full article

(This article belongs to the Special Issue Rehabilitation and Reconstruction of Buildings)

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11 pages, 2307 KiB

Open AccessArticle

Development of a New Nondestructive Method for the In-Situ Determination of Mortar Strength

by Jiří Žalský, Miroslav Vokáč, Milan Hrabánek and Karel Hurtig

Buildings 2023, 13(2), 273; https://doi.org/10.3390/buildings13020273 - 17 Jan 2023

Cited by 3 | Viewed by 1518

Abstract

The determination of the load bearing capacity of masonry in existing structures is not an easy task, even for experienced surveyors. For its assessment, it is necessary to know the compressive strength of the masonry units and mortar. Relatively good destructive and non-destructive [...] Read more.

The determination of the load bearing capacity of masonry in existing structures is not an easy task, even for experienced surveyors. For its assessment, it is necessary to know the compressive strength of the masonry units and mortar. Relatively good destructive and non-destructive methods were developed for the determination of the compressive strength of masonry units. However, mortar compressive strength determination is currently closer to a rough estimation rather than a deterministic approach. All of the currently used methods are either complicated, have a limited application, or are based on the surveyor’s experience only. Influence of the human factor on the results of testing is significant. The paper introduces the development of a new non-destructive method, which eliminates the influence of the human factor. The method is supposed to work as quickly and as easily as the Schmidt hammer used for concrete structure surveys. The new instrument was created where the compressive strength of mortar is assessed by hammering a steel bar into a joint with constant energy, while the depth of penetration is measured. The impact energy is provided by a steel spring with a prescribed stiffness, and the loading is provided by an automatic system similar to those used in air-soft guns. Full article

(This article belongs to the Special Issue Rehabilitation and Reconstruction of Buildings)

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19 pages, 9756 KiB

Open AccessArticle

Study of the Interaction of Cement-Based Materials for 3D Printing with Fly Ash and Superabsorbent Polymers

by Jindřich Melichar, Nikol Žižková, Jiří Brožovský, Lenka Mészárosová and Radek Hermann

Buildings 2022, 12(11), 2008; https://doi.org/10.3390/buildings12112008 - 17 Nov 2022

Cited by 6 | Viewed by 2056

Abstract

The use of superabsorbent polymers (SAP) in construction is a relatively new trend, and not a completely explored area. However, SAP itself has been on the market for over 80 years. SAPs have a cross-linked three-dimensional structure, thanks to which they have the [...] Read more.

The use of superabsorbent polymers (SAP) in construction is a relatively new trend, and not a completely explored area. However, SAP itself has been on the market for over 80 years. SAPs have a cross-linked three-dimensional structure, thanks to which they have the unique ability to absorb extreme amounts of water, up to a hundred times their weight. By using this property, it is possible to prevent water losses, which is important at the time of maturation in cementitious building materials. When there is a lack of water needed for hydration processes, the physical and mechanical properties deteriorate. The subject of this article is to determine the possible positive effect of the presence of SAP in the cement matrix in order to optimize the parameters of silicate composites for 3D printing. For this purpose, a special methodology was compiled consisting of tests through which it is possible to assess the suitability of the tested mixtures for 3D printing. This methodology consists of determining consistency, volumetric weight, ultrasonic analysis, buildability, X-ray diffraction, flexural tensile and compressive strength. For determining of buildability and ultrasonic analysis new methodologies were created in this research in order to be suitable for the 3D printing materials. Last but not least, efforts are also being made to increase the incorporation of secondary raw material (fly ash) in order to reduce the environmental impact of industrial production and, conversely, to increase its sustainability while maintaining or improving the mechanical–physical parameters of building materials. From the results presented in this paper it is apparent, that created methodology is efficient for determining properties of 3D printable mixtures. SAPs also significantly influenced properties of these mixtures. Mainly buildability and flexural tensile strength (by up to 30%) were increased and volumetric weight was decreased (by up to 5%). Full article

(This article belongs to the Special Issue Rehabilitation and Reconstruction of Buildings)

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17 pages, 6427 KiB

Open AccessArticle

Use of Lightweight Sintered Fly Ash Aggregates in Concrete at High Temperatures

by Klára Křížová, Jan Bubeník and Martin Sedlmajer

Buildings 2022, 12(12), 2090; https://doi.org/10.3390/buildings12122090 - 29 Nov 2022

Cited by 5 | Viewed by 2323

Abstract

This study addresses the issue of the resistance to high temperatures of lightweight concrete lightweighted with sintered fly ash aggregate. Lightweight concretes with different amounts of lightweighting and their properties after loading temperatures of 600, 800 and 1000 °C were investigated. In particular, [...] Read more.

This study addresses the issue of the resistance to high temperatures of lightweight concrete lightweighted with sintered fly ash aggregate. Lightweight concretes with different amounts of lightweighting and their properties after loading temperatures of 600, 800 and 1000 °C were investigated. In particular, the effect of high temperature on the mechanical properties of the concrete was determined on the test specimens, and the effect on the microstructure was investigated by X-ray diffraction analysis and scanning electron microscopy. It was found that there is an increase in compressive strength between 0 and 21% up to 800 °C, where the increase in strength decreases with increasing degree of lightening. At 1000 °C, the internal structure of the lightweight concrete destabilized, and the compressive strength decreased in the range of 51–65%. After loading at 1000 °C, the scanning electron microscope showed the formation of spherical-shaped neoplasms, which significantly reduced the internal integrity of the cement matrix in the lightweight concrete due to the increase in their volume. It was found that the lightweight concretes with higher lightweighting showed significantly less degradation due to higher temperature. Full article

(This article belongs to the Special Issue Rehabilitation and Reconstruction of Buildings)

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15 pages, 3088 KiB

Open AccessArticle

The Use of Advanced Environmentally Friendly Systems in the Insulation and Reconstruction of Buildings

by Jiří Zach, Vítězslav Novák, Jitka Peterková, Jan Bubeník, Mitja Košir, David Božiček and Zdeněk Krejza

Buildings 2023, 13(2), 404; https://doi.org/10.3390/buildings13020404 - 1 Feb 2023

Cited by 3 | Viewed by 2385

Abstract

This study is devoted to the possibility of using advanced insulation materials, such as Vacuum Insulation Panels (VIP), in the insulation and reconstruction of buildings, in connection with the green elements that are installed on the facade in the case of the use [...] Read more.

This study is devoted to the possibility of using advanced insulation materials, such as Vacuum Insulation Panels (VIP), in the insulation and reconstruction of buildings, in connection with the green elements that are installed on the facade in the case of the use of external thermal insulation composite systems (ETICS). The use of VIP as part of the insulation system will result in a significant reduction in the required thickness of the insulation layer. In turn, the reduced overall thickness of the system will allow for easier direct anchoring of the elements of the green facade through the insulating layer to the base of the structure. The research carried out proves that, by using VIP in the insulation system (with a VIP thickness of 30 mm in combination with 20 mm of extruded polystyrene XPS), the thermal insulation properties can be significantly improved and, thus, the thickness of the insulation system can be reduced to 1/3 of the thickness of conventional insulation (while achieving the same thermal resistance), thereby enabling the anchoring of green elements on the surface of such an insulation system. Full article

(This article belongs to the Special Issue Rehabilitation and Reconstruction of Buildings)

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17 pages, 3242 KiB

Open AccessArticle

Experimental Research on Hybrid Hardwood Glue-Laminated Beams

by Eva Šuhajdová, Pavel Schmid, Miloslav Novotný, Jan Pěnčík, Karel Šuhajda and Ondřej Uhlík

Buildings 2023, 13(4), 1055; https://doi.org/10.3390/buildings13041055 - 17 Apr 2023

Cited by 6 | Viewed by 1686

Abstract

The aim of this work was to verify the behavior of hybrid hardwood glue-laminated beams and the possibility of replacing Norway spruce (Picea abies) construction elements, especially in roof and ceiling structures. The samples were six lamellae homogeneous beech (Fagus [...] Read more.

The aim of this work was to verify the behavior of hybrid hardwood glue-laminated beams and the possibility of replacing Norway spruce (Picea abies) construction elements, especially in roof and ceiling structures. The samples were six lamellae homogeneous beech (Fagus sylvatica) beams and six-lamellae hybrid beech-poplar (Fagus sylvatica–Poplar spp.) beams; each beam had a cross-section of 60 × 120 mm and was glued with polyurethane adhesive. The samples were loaded using destructive four-point bending tests according to EN 408; the obtained bending strength and modulus of elasticity were statistically evaluated and compared to each other in both types of samples. The results showed that the examined properties of the hybrid beams (with a 16% weight reduction) are comparable to the properties of homogeneous beech glue-laminated beams. Based on the obtained data, the timber elements that are currently used can be successfully replaced by hardwood glue-laminated elements. Based on their higher load-bearing capacity, the cross-section depth can be reduced compared to a larger cross-section depth in spruce beams; this means that hardwood could be suitable in building renovations. Full article

(This article belongs to the Special Issue Rehabilitation and Reconstruction of Buildings)

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20 pages, 8643 KiB

Open AccessArticle

Heat Flow through a Facede with a Controlled Ventilated Gap

by Aleš Rubina, Pavel Uher, Jakub Vrána, Miloslav Novotný, Ondřej Nespěšný, Daniel Skřek, Eva Šuhajdová, Jan Vystrčil and Marian Formánek

Buildings 2023, 13(3), 817; https://doi.org/10.3390/buildings13030817 - 20 Mar 2023

Cited by 1 | Viewed by 2428

Abstract

The article presents current research results in the field of airflow through a façade with a width of 1 m and a height of 13.7 m and with a ventilated gap, and its effect on the year-round heat balance of this façade. An [...] Read more.

The article presents current research results in the field of airflow through a façade with a width of 1 m and a height of 13.7 m and with a ventilated gap, and its effect on the year-round heat balance of this façade. An idea to influence airflow in the ventilated gap of the façade is presented based on the results of developed software and the suitability of closing the air gap in winter and in the transition period of the year is described. First, the boundary conditions of the calculations, which are further used in the energy balance between the interior of the building and the exterior environment are defined. In order to include these influences, a discrete analytical calculation was created. It consists of the time distribution of the investigated thermal phenomena calculations. A significant finding is an obvious benefit of controlling the airflow through a ventilated gap in the winter and especially in the transitional period of the year. This technological knowledge has a high potential for energy savings related to the heating of buildings. As the calculations show, airflow control through a ventilated façade reduces heat flow by 25–30% on average, and in contrast, it increases heat gains by 20% and the specific values are presented within the article. Full article

(This article belongs to the Special Issue Rehabilitation and Reconstruction of Buildings)

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20 pages, 117644 KiB

Open AccessArticle

Experimental Comparison of Efficiency of Water-Soluble and Solvent Hydrophobic Agents for Concrete

by Jakub Hodul, Jana Hodná, Lenka Mészárosová and Ruben Paul Borg

Buildings 2022, 12(11), 1857; https://doi.org/10.3390/buildings12111857 - 2 Nov 2022

Cited by 3 | Viewed by 1816

Abstract

The paper presents the results and assessment of the properties and capabilities of new types of surface hydrophobic agents for the treatment of fresh and matured surfaces of concrete and other cement-bound layers. Hydrophobisation prevents the premature evaporation of water and thus plastic [...] Read more.

The paper presents the results and assessment of the properties and capabilities of new types of surface hydrophobic agents for the treatment of fresh and matured surfaces of concrete and other cement-bound layers. Hydrophobisation prevents the premature evaporation of water and thus plastic shrinkage, which inevitably leads to the formation of cracks in cement-based structures. The influence of the new type of hydrophobic agents, epoxy water-based (EWH) and acrylate (AH) containing solvent, on the physical and mechanical properties of the treated concrete samples was assessed, including the adhesion of hydrophobisation on the concrete surface layers. It was confirmed that surface hydrophobisation successfully prevents premature evaporation of water, and thus, plastic shrinkage (concrete treated with EWH_0.3 showed more than two times lower shrinkage than reference concrete). The concrete samples treated by hydrophobisation agents showed higher strength after 120 days (37.5 MPa) in comparison with untreated concrete (32.8 MPa). Different properties were recorded with different types of hydrophobisation agents, including compressive strength after 90 days (31.2 MPa with EWH_0.15, and 35.9 MPa with AH_0.15). Water absorption after 120 days was lowest with EWH_0.3 samples (3.77%), two times lower than AH_0.15 (6.98%). The layer of hydrophobisation agent EWH_0.3 was thicker than AH_0.15, leading to lower water absorption of treated concrete and higher resistance to defrosting chemicals—waste 8.5. g/m² with EWH_0.3 in comparison to 35.7 g/m² with AH_0.15. Furthermore, a difference in the hydrophobisation behaviour was shown with blocking of infiltration from the chemically aggressive environment into the concrete substrate. Deterioration of the surface concrete exposed to 10% HCl solution was worse with AH_0.15; but the concrete surface treated with AH_0.15 showed better resistance than the EWH treated surface, when exposed to 5% CH₃COOH. Degradation of the hydrophobisation integrity and the loss of cohesion between the concrete and the surface treatment after exposure to acetic acid and hydrochloric acid was observed using scanning electron microscopy (SEM). Full article

(This article belongs to the Special Issue Rehabilitation and Reconstruction of Buildings)

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21 pages, 4328 KiB

Open AccessArticle

The Effect of Exposure Conditions on the Properties of Cementitious Composites with Reduced Electrical Resistivity

by Vojtěch Uher, Vít Černý, Rostislav Drochytka and Šimon Baránek

Buildings 2022, 12(12), 2124; https://doi.org/10.3390/buildings12122124 - 3 Dec 2022

Cited by 3 | Viewed by 1813

Abstract

Cement composite materials with reduced resistivity are specialized building materials, which are constantly pushing their limits. Research into these composites requires a study of the influences of exposure conditions on resistivity. The mixes selected for the purpose of the research included the reference, [...] Read more.

Cement composite materials with reduced resistivity are specialized building materials, which are constantly pushing their limits. Research into these composites requires a study of the influences of exposure conditions on resistivity. The mixes selected for the purpose of the research included the reference, pure cement mix, and mixes with proportions of graphite under and above the percolation threshold, with two different types of graphite. It was found that the resistivity of all the tested mixes decreases if moisture grows; the influence of moisture is more significant for mixes with graphite proportions below the percolation threshold. The resistivity of all the tested mixes decreases with increasing temperatures; the influence of a higher temperature (50 °C) is more significant for mixes with graphite proportions above the percolation threshold; however, these mixes are, at the same time, more resistant to permanent changes in resistivity caused by frost (−10 °C). It was found that the action of CO₂ causes a reduction in resistivity. Mixes with proportions of graphite above the percolation threshold show higher stability when exposed to CO₂. Mixes with proportions of graphite below the percolation threshold are extremely sensitive to horizontally oriented pressure loads. Increases in resistivity caused by vertical pressure loads were by 20–40%. The resistivity of the mixes with proportions of graphite above the percolation threshold was less sensitive to the pressure load. Full article

(This article belongs to the Special Issue Rehabilitation and Reconstruction of Buildings)

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24 pages, 7343 KiB

Open AccessArticle

Recycling Plaster Waste as a Substitute for Aggregates in Obtaining Plastering Mortars

by Saitis Catalin, Manea Lucia Daniela, Plesa Luminita Monica and Saitis Lavinia Raluca

Buildings 2023, 13(2), 491; https://doi.org/10.3390/buildings13020491 - 11 Feb 2023

Cited by 3 | Viewed by 2953

Abstract

The current context regarding the management of waste obtained from the construction industry, according to European Union laws and directives, requires the imposition of an integrated waste management system. The main objective of this study was to integrate and reuse old plaster waste [...] Read more.

The current context regarding the management of waste obtained from the construction industry, according to European Union laws and directives, requires the imposition of an integrated waste management system. The main objective of this study was to integrate and reuse old plaster waste as a substitute for aggregates in significant proportions in mortar composition and analyzing the impact on the physical and mechanical characteristics of mortar in fresh state and in hardened state. Over periods of 7, 14, and 28 days, the experimental program studied three types of plastering mortars: a standard recipe (without waste) and another two proposed recipes, in which construction waste was re-used as a substitute for aggregates in proportions of 10% and 15%. Results obtained on the fresh properties of the proposed plastering mortars (apparent density, consistency, and segregation trend) indicated a variation (increase/decrease) of 1% to 2.5% compared with the standard recipe. Mechanical strengths showed decreased values; that is, the compressive strength decreased by 11.09% and the flexural strength decreased by 22% when waste replaced aggregates in a proportion of 15%. The results of the experimental program identified the potential of waste plaster, which can replace up to 15% of the aggregates in plaster mortars, which still guarantees their successful use in practice. To reduce the influence of the use of waste on the mechanical strengths, we propose to conduct further investigations (nuclear magnetic resonance, electronic microscopy, and X-ray diffraction) on these mortars reinforced with different types of fibers. The large amount of waste resulting from the rehabilitation of damaged building facades and the fact that there are currently no experimental studies on the reuse of waste from old plaster mortars were the main reasons for the present study examining the possibility of their use in the production of new building materials. Full article

(This article belongs to the Special Issue Rehabilitation and Reconstruction of Buildings)

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17 pages, 2290 KiB

Open AccessArticle

Development of a Low-pH Concrete Intended for Deep Geological Repository for Radioactive Waste

by Radka Pernicova, David Citek, Daniel Dobias, Jiri Kolisko, Tomas Mandlik and Lucie Hausmannova

Buildings 2023, 13(1), 182; https://doi.org/10.3390/buildings13010182 - 10 Jan 2023

Cited by 2 | Viewed by 2449

Abstract

This article deals with the development of concretes intended to be used as construction materials in the Czech deep repository for radioactive waste. The basic requirements for this concrete are a reduced pH value, which must maintain a constant reduced pH with a [...] Read more.

This article deals with the development of concretes intended to be used as construction materials in the Czech deep repository for radioactive waste. The basic requirements for this concrete are a reduced pH value, which must maintain a constant reduced pH with a value of around 11 in the long term, and mechanical properties comparable to conventional concrete. The raw materials for the production of the proposed low pH concrete come exclusively from the Czech Republic. Material characteristics were measured on fresh mixtures and concrete after 28, 56, and 90 days of curing. In addition to the basic raw materials (aggregate, cement, water), plasticizers, microsilica or slag, and defoaming agents were added to the mixture. The aggregate:binder ratio was approximately 5:1 and the w/c water coefficient was approximately 0.6. The mechanical properties of the final concrete were similar to the reference recipe of conventional concrete (the decrease was less than 10%) and the pH value was even below 11 after 90 days. The issue of a sprayed variant of the LPC mixture was solved within the project. Full article

(This article belongs to the Special Issue Rehabilitation and Reconstruction of Buildings)

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13 pages, 7890 KiB

Open AccessArticle

In-Plane Behaviour of Unreinforced Masonry Strengthened with a Structural Glass Window: A Proof of Concept

by Maria B. Gaggero, Paul A. Korswagen, Rita Esposito and Jan G. Rots

Buildings 2023, 13(2), 361; https://doi.org/10.3390/buildings13020361 - 28 Jan 2023

Viewed by 3904

Abstract

Innovative solutions for seismic-retrofitting existing structures are currently required, as often traditional strategies are expensive, non-reversible, highly invasive, and/or fail to address both serviceability and ultimate limit states together. The present paper describes a preliminary experimental campaign performed at TU Delft to investigate [...] Read more.

Innovative solutions for seismic-retrofitting existing structures are currently required, as often traditional strategies are expensive, non-reversible, highly invasive, and/or fail to address both serviceability and ultimate limit states together. The present paper describes a preliminary experimental campaign performed at TU Delft to investigate an innovative structural glass window for strengthening masonry buildings. To this purpose, a prototype composed of a timber frame, a semi-rigid adhesive, and a 20 mm thick structural glazing layer was designed. The prototype aimed to improve the structure’s behavior against minor but more frequent service vibrations (SLS), as well as against ultimate ones (ULS). Specifically, an increase in the structure’s in-plane capacity and stiffness was targeted to reduce cracking at low drifts/displacements, while at larger drifts, the adhesive’s tearing and timber crushing were used to activate damping. To evaluate the prototype’s performance, a quasi-static, cyclic, in-plane test on a strengthened full-scale wall was performed and compared with available data on a similar, yet unstrengthened, wall. Although the benefits were not pronounced in terms of cracking and energy dissipation, the implementation of the proposed strategy provided an increase in terms of initial stiffness (18%), force capacity (8%, 36%), and ductility (220%, 135%). This outcome provides the ground for numerical studies that will help better delineate the proposed strategy and improve the current design. Full article

(This article belongs to the Special Issue Rehabilitation and Reconstruction of Buildings)

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14 pages, 4353 KiB

Open AccessArticle

Comparison of Wood Moisture Meters Operating on Different Principles of Measurement

by Adam Běťák, Jiří Zach, Petr Misák and Jan Vaněrek

Buildings 2023, 13(2), 531; https://doi.org/10.3390/buildings13020531 - 15 Feb 2023

Cited by 4 | Viewed by 2881

Abstract

This experiment compared commercially available moisture meters (three capacitive metersand one resistance meter) and tested their predictive ability at different moisture conditions on selected beech (Fagus sylvatica) and spruce (Picea abies (L.) Karst.) wood samples. The measurements were carried out [...] Read more.

This experiment compared commercially available moisture meters (three capacitive metersand one resistance meter) and tested their predictive ability at different moisture conditions on selected beech (Fagus sylvatica) and spruce (Picea abies (L.) Karst.) wood samples. The measurements were carried out on the samples at specified moisture intervals ranging from 5% to 30% moisture content (MC). The resistance meter showed a close correlation to gravimetric MC values; the influence of the measuring direction for MC below 17% was found when higher MCs in the transverse direction for both species were archieved. The difference was 4.6 times higher for softwood and 1.6 times higher for hardwood. Differences between radial and tangential transverse measuring were not observed. The close correlation coefficient of MC measurements was also found for capacitive methods. The effect of the direction was found for all the tested meters when higher MC values in the longitudinal measurements were found. This effect was especially significant at an MC of wood higher than 20 wt.%. For two capacitive methods, the effect of annual ring deflection only in the spruce samples was found where higher MC values in the tangential direction were observed. Full article

(This article belongs to the Special Issue Rehabilitation and Reconstruction of Buildings)

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12 pages, 4998 KiB

Open AccessArticle

Medium-Scale Fire Resistance Testing of Timber Structures with Composite Cement Fibre Materials

by Tomáš Žajdlík, Karel Šuhajda and David Průša

Buildings 2023, 13(2), 527; https://doi.org/10.3390/buildings13020527 - 15 Feb 2023

Cited by 3 | Viewed by 1860

Abstract

The combustibility of natural wood presents a negative impact for using this material in buildings. Timber elements can be cladded with boards made of non-combustible materials. This study represents a group of options for increasing the resistance of timber against the effects of [...] Read more.

The combustibility of natural wood presents a negative impact for using this material in buildings. Timber elements can be cladded with boards made of non-combustible materials. This study represents a group of options for increasing the resistance of timber against the effects of fire and the possibility of slowing down the effect of thermal degradation of wood. The aim of this study is focused on an experimental testing of structures with timber elements protected by cement fibre boards as a non-combustible fire retardant. Cement fibre boards are fibre-reinforced composite materials used for systems of dry constructions. These boards present the highest degree of fire reaction class (A1). The behaviour of the structure, loaded by the effects of fire, was monitored during the experiment. The specimen was tested with reduced dimensions. The temperature loading corresponded to the procedure according to the standards. The final fire resistant (FR) results were evaluated in accordance with the requirements for the selected limit states of FR. This was assessed based on the measured temperatures and the whole condition of the tested specimen. The specimen fulfilled the fire-separating function of the structure for the classification times. Full article

(This article belongs to the Special Issue Rehabilitation and Reconstruction of Buildings)

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11 pages, 3518 KiB

Open AccessArticle

Rehabilitation of Porous Building Components and Masonry by MICP Injection Method

by Brigitte Nagy and Andrea Kustermann

Buildings 2023, 13(5), 1273; https://doi.org/10.3390/buildings13051273 - 13 May 2023

Cited by 4 | Viewed by 1363

Abstract

Microbial-induced calcium carbonate precipitation (MICP) is a novel approach that is already being applied in various areas of construction. The precipitated calcium carbonate can be used to reduce porosity and thus increase the durability of deteriorated building components. This study investigates whether MICP [...] Read more.

Microbial-induced calcium carbonate precipitation (MICP) is a novel approach that is already being applied in various areas of construction. The precipitated calcium carbonate can be used to reduce porosity and thus increase the durability of deteriorated building components. This study investigates whether MICP injections are suitable for building rehabilitation. Porous mortar test samples of recycled aggregate and parts of deteriorated masonry were prepared. The MICP injections were performed without pressure and with an injection pump. The treatment effect was investigated after MICP injection by testing the porosity, strength and microscopic evaluation. It can be observed that multiple MICP injections under pressure result in a reduction of the pore volume of porous mortar samples. The produced calcium carbonate precipitates in the pore space of the samples and increases the density by 1.59% and the weight by 7.56%, which also results in a 48.3% reduction of the capillary water absorption. The results of strength tests show an increase of 45.16% in flexural strength and 35.64% in compressive strength compared with the untreated mortar samples. In addition, the MICP process was investigated and the precipitation was characterised. The X-ray diffraction (XRD) of the precipitated calcium carbonate confirms that mainly calcite was formed, which was also found in the pore structure of the MICP-injected masonry after the microscopic analysis. Precipitated calcium carbonate could be detected especially near the injection spots. Full article

(This article belongs to the Special Issue Rehabilitation and Reconstruction of Buildings)

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19 pages, 3038 KiB

Open AccessEssay

Earthquake Economic Loss Assessment of Reinforced Concrete Structures Using Multiple Response Variables

by Xiaoxiao Liu, Jingming Chen, Hongchen Wang, Zhaoping Jia and Ziyan Wu

Buildings 2023, 13(7), 1719; https://doi.org/10.3390/buildings13071719 - 5 Jul 2023

Cited by 2 | Viewed by 1408

Abstract

For buildings that meet the requirements of current seismic design codes, damage to nonstructural components and the internal objects of buildings often become the main source of the seismic economic losses of these buildings. However, the current specifications only consider the safety of [...] Read more.

For buildings that meet the requirements of current seismic design codes, damage to nonstructural components and the internal objects of buildings often become the main source of the seismic economic losses of these buildings. However, the current specifications only consider the safety of ‘no collapse under strong earthquake’ and do not consider ‘functional recoverability’. In this paper, a six-story frame building was taken as an example. Four joint performance limit states were proposed, as per FEMA 273, to establish a two-dimensional probabilistic seismic demand model that considers parameter correlations. The limit state function was established, and the two-dimensional seismic vulnerability curve was calculated. The seismic intensity–economic loss curve and the annual average economic loss established by one-dimensional and two-dimensional seismic vulnerability curves were compared. The results showed that the seismic performance of the structure was lower than expected when using only a one-dimensional seismic vulnerability curve. However, the situation was more serious under high-intensity earthquake and high-performance levels. Full article

(This article belongs to the Special Issue Rehabilitation and Reconstruction of Buildings)

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16 pages, 4009 KiB

Open AccessFeature PaperArticle

Microwave Technology, Its Use and Heating of Composite Aerated Concrete Blocks

by Jindřich Sobotka, Zdeněk Jiroušek, Táňa Švecová and Miloslav Novotný

Buildings 2023, 13(7), 1729; https://doi.org/10.3390/buildings13071729 - 7 Jul 2023

Cited by 1 | Viewed by 1159

Abstract

This paper aims to test the method of using microwave technology for drying aerated concrete masonry. Furthermore, the propagation of microwave technology through irradiated elements and the effectiveness of eliminating the moisture of the given blocks were examined. There are various discussions about [...] Read more.

This paper aims to test the method of using microwave technology for drying aerated concrete masonry. Furthermore, the propagation of microwave technology through irradiated elements and the effectiveness of eliminating the moisture of the given blocks were examined. There are various discussions about the potential use of this technology in civil engineering. However, they are often based on inaccurate, superficial knowledge. The cause is usually based on a lack of access to accurate professional knowledge. Although the potential use of microwave technology (MWT) has been known for many decades, its use in civil engineering tends to be of marginal interest. The research and tests are mostly carried out by private facilities, which protect the obtained knowledge as their “know how”. For this reason, VUT Brno teamed up with an implementation company and conducted several dozen experiments with repeated measurements of the effect of MWT on various building materials. Moreover, a number of different tests with drying of building materials, as well as the elimination of biotic pests in buildings have been carried out. However, the vast majority were experiments carried out in laboratory conditions, i.e., under precisely given boundary conditions, which were often very far from the conditions in real construction practice. Therefore, the goal of this experiment was to verify the use of microwave technology during the drying and heating of building materials. The experiments on the heating and drying of aerated concrete parts were divided into several phases, in which the dependence of the depth of heating on the time intervals of irradiation was verified. It was clearly concluded that the drying of this material by microwaves is very effective and efficient, particularly from time and financial viewpoints. Therefore, this technology can be successfully used in construction practice, which has started to be often used with reconstructions. Full article

(This article belongs to the Special Issue Rehabilitation and Reconstruction of Buildings)

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