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In the beginning of the 1980s earth building has undergone a renaissance, which nowadays leads to an increasing use of load-bearing earth constructions and in particular, earth block masonry. At present, there are no common structural standards according to the semi-probabilistic design concept, which is the state-of-the-art in European standards.
A solid database is needed for the determination of the partial safety factor on the resistance side. Therefore, compressive strength tests were carried out with two types of earth blocks and two types of prefabricated earth mortar. The evaluation showed that the variation of the compressive strength was remarkably less than expected, which seems to indicate high quality standards of the components earth block and mortar with regard to industrial production.
On the basis of these results and together with the reliability method, a partial safety factor for earth block masonry subjected to compression was determined. The main aim of the research was the development of a first valid database for material parameters of earth block masonry with particular regard to statistical characteristics. The results showed that a common calculation method for earth block masonry based on partial safety factors following the valid masonry construction standard is feasible.
Multi residential buildings, developed as highly energy-efficient and airtight are nowadays often fitted with mechanical Ventilation Systems as a way to overcome shortcomings and even defects tinked to indoor climate. The presented study investigates the potential of low-emitting. natural building materials with hygroscopic properties to contribute to a healthy and comfortable indoor environment, while reducing the need for mechanical Ventilation.
A selection of natural building materials suitable for application as internal partition walls has been investigated with regards to their water vapour adsorption capacity.
Special emphasis was placed on the investigation of modified earth plasters as well as wood-based materials, used as wall lining to provide increased adsorption capacities.
In addition, tests on materials emissions (formaldehyde, VOCs, SVOCs and radon) as well as adsorption tests of airborne pollutants have been conducted in specially-designed fest chambers. All tests were performed at either the material or the component tevel.
Overall results to date suggest that natural materials contribute to an improved indoor environment quality through an increased moisture-buffering capacity, low emissions and the potential to adsorb airborne pollutants, therefore reducing the need for mechanical Ventilation.
In this paper, a comparative study on the initial shear strength of
masonry with earth mortars is presented. Triplet tests were carried out to characterise the shear bond strength of five different types of earth mortar, three purely mineral and two with vegetable additives (wood and straw chaff), using calcium silicate blocks. In spite of their lower bulk densities, mortars with chaffs reached a value of compressive strength comparable to the values shown by the purely mineral mortars. The characteristic initial shear strengths of all the tested earth mortars were between two and five times higher than the minimum values for initial shear strengths required by standards.
To assess the influence of blocks pre-wetting, a comparison between calcium silicate blocks and earth blocks was performed to evaluate the results obtained from the standard test procedure compared to the more common practice of using earth mortars in combination with earthen blocks.
This paper focuses on the experimental evaluation of one of the key microstructural Parameters of a short-fiber reinforced composite – the orientation distribution of fibers. It is shown that computed tomography (CT) produces results suitable for reconstruction of the orientation distribution function. This function is used for calculation of the effective elastic properties of polymer-fiber reinforced concrete. Explicit formulas are derived for overall elastic moduli accounting for orientation distribution in the frameworks of the noninteraction approximation, the Mori–Tanaka–Benveniste scheme, and the Maxwell scheme.
The approach illustrated can be applied to any kind of composite material.
A further improvement of the excellent properties of UHPC can be realized with thermal Treatment. Like for normal concrete, it accelerates the hardening and prevents shrinkage after the treatment. Additionally, an increase in strength can be achieved. Aim of this study was the optimisation of the thermal Treatment conditions of UHPC for very different Treatment methods; heat Treatment at 90 °C for unprotected and sealed samples, hot water bath at 90 °C and hydrothermal Treatment at 185 °C/1.1 MPa. The pre-storage time and the dwell time were systematically varied for each method to gain a higher strength. The compressive strength depends on the manner of Treatment at which higher water accessibility leads to higher strengths. The Phase composition changes considerably with different Treatment tempereatures. Finally, it can activate unhydrated binder components forming additional C-S-H, leading to higher strength.
An experimental investigation was carried out to study the in-plane shear behaviour of rammed earth structural elements strengthened with polyester fabric strips. The original idea for the retrofitting with polyester fabric strips was to introduce a vertical element for walls in order to take up horizontal loads resulting in a shear response of the building element. It has to be considered that vertical slits into the walls for fixing the strips are points of weakness and have to be mitigated by the adhesive. In this case a base coat mortar was employed. Strengthened elements were tested to exploit the strength potential of earthen materials and to solve its lack of tensile strength, significantly improving not only strength but also ductility. As part of the study results of a testing campaign of unstrengthened structural elements were considered. Strengthened elements were tested in diagonal compression/shear and cyclic shear-compression. A unique reinforcement orientation was used. The results of these tests are presented in this paper and include the load-displacement behaviours, crack patterns, failure modes. The results showed that the reinforcement was the most effective under cyclic shear-compression tests, with increase in load and displacement capacity observed. Under diagonal compression the reinforcement did not likely contribute significantly to the shear resistance, due to a lack of embedment length of the strips.
The life span of a building product is a key Parameter when it comes to Life Cycle Assessment (LCA) performance. Nevertheless, many uncertainties affect this parameter due to a lack of long-term performance data. The sensitivity of the LCA outcomes to this parameter has been studied within the framework of the FP7 project H-House (Healthier Life with Eco-innovative Components for Housing Constructions) funded by the European Commission.
The paper Features two comparative studies conducted within the scope of this project: one for new construction and another for renovation. An innovative precast sandwich panel made of Textile Reinforced Concrete (TRC) and Foamed Concrete (FC), used for external walls in new construction, is compared with a steel reinforced concrete (SRC) wall of the same thermal resistance. For renovation, a novel halfsandwich panel made of Ultra-High-Performance-Concrete (UHPC) and Autoclaved Aerated Concrete (AAC) is compared with cladding having the same thermal performance. The Evaluation was conducted using a multi-criteria basis according to the LCA methodology (ISO 14040- 44). In each case, an identical life span for both scenarios leads to the fact that H-House components have a better environmental performance. The ISO 15686 and ist relevant parts have been considered for the estimation of the service life span. The sensitivity analysis shows the link between the impact savings of the innovative walls and the life span of the walls and their components. In particular, it was found that since both scenarios need to fulfil the same service during an identical reference period, and since some maintenance and replacement of materials are necessary over time for standard Solutions compared to the innovative ones, the chosen life span of the components plays a role of utmost importance. The sensitivity analysis discloses the effect of the assumptions on these aspects.
This paper presents the development of ultra-high performance concrete (UHPC) for façade elements with self-cleaning properties. For creating self-cleaning surfaces two different approaches are proposed. One approach is based on the photocatalytic activation of the external UHPC shell by incorporation of TiO2 particles. The second approach consists of the modification of the UHPC surface by micro structuring in combination with the application of hydrophobic agents to create durable super hydrophobicity. In the framework of the H-HOUSE Project funded by the European Commission the experimental investigations were performed with UHPC based on Dyckerhoff Nanodur® technology. The special properties of this material enable the precise reproduction of any micro structure without flaws. The current results obtained from laboratory and outdoor weathering tests are promising and demonstrate the feasibility of the approaches.
The aim of this study was to develop a lightweight composite façade element for refurbishment of existing façades. It was crucial to minimize the thermal bridges and to undercut the thermal requirement of the system existing façade new element. The awareness of the environmental impact of the building sector is increasing. In this context, ultra-high performance concrete (UHPC) materials are shown to be promising alternatives with advantages such as lower embodied energy and reduced environmental impact. Predictions suggest that UHPC composite elements for building envelopes could have other benefits such as an increased service life, optimized use of building area due to thinner elements and minimized maintenance due to the absence of reinforcement or use of non-corrosive reinforcing materials such as carbon fibers. In this framework, composite elements have been developed combining an autoclaved aerated concrete insulation layer with an external UHPC supporting layer. The results show that the lightweight composite element has a good performance in term of thermal transmittance and minimization of thermal bridges.
In diesem Beitrag werden numerische Analysen der mechanischen Eigenschaften von Lehmsteinmauerwerk unter Druck- und Schubbeanspruchung vorgestellt. Ergebnisse von einachsigen Druck- und Schubversuchen an Wandprüfkörpern lieferten dafür grundlegende mechanische Kennwerte im elastischen Bereich und im nichtelastischen Versagenszustand.Die Testergebnisse zeigten, dass verschiedene Vorlasten keinen wesentlichen Einfluss auf die Schubfestigkeit haben. Außerdem bestätigten die Ergebnisse das spröde Verhalten von Lehmsteinmauerwerk unter einachsiger Druckbelastung und es zeigte sich, dass das Versagen des Lehmsteinmauerwerks unter Scherbelastung entlang der Mörtelfugen erfolgt.
Die experimentellen Ergebnisse wurden verwendet, um das Verhalten von Lehmsteinmauerwerk durch nichtlineare Finite-Elemente-Methoden auf der Basis von Makro- und Mikro-Modellierungsansätzen zu simulieren. Entsprechendes konstitutives Materialverhalten und Zwängungen, die in den Versuchen durch die Art der Lasteinleitung in Form von Stahlprofilen und Stahlschuhen verursacht wurden, wurde in den Modellen berücksichtigt. Es wurde zuerst ein auf der Grundlage der experimentellen Daten kalibriertes Makro-Modell entwickelt, was zu einer brauchbaren Vorhersage des Versagensverhaltens der Mauerwerksprüfkörper führte. Die simulierten Spannungs-Dehnungs-Kurven, berechnet unter einachsiger Druckbelastung, zeigten eine gute Übereinstimmung mit den Ergebnissen der geprüften Mauerwerkskörper, sowohl im elastischen als auch im nichtelastischen Bereich. Ein vereinfachter Ansatz, basierend auf der Makro-Modellierung und einem homogenisierten Prüfkörper, kann für die Untersuchung größerer Tragsysteme oder ganzer Gebäude angewendet werden, wobei eine zufriedenstellende Genauigkeit bei geringerem Rechenaufwand erreicht wird. Obwohl das globale Spannungs-Dehnungs-Verhalten zufriedenstellend wiedergegeben wurde, ist ein solches nichtlineares isotropes Kontinuumsmodell für Lehmsteinmauerwerk nicht in vollem Umfang geeignet, um das bei den Versuchen beobachtete Rissbild an den Prüfkörpern zu simulieren.
Eine detailliertere Analyse des mechanischen Verhaltensdes Mauerwerks wurde mit einem Mikro-Modellierungsansatz durchgeführt. Das Modell, in dem ein Wandabschnitt nicht mehr homogenisiert, sondern in konkrete Stein- und Fugenelemente diskretisiert wird, hat sich insbesondere für das Verhalten von Lehmsteinmauerwerk unter Schubbeanspruchung als geeignet erwiesen. Die Auswertung der Spannungsverteilungen bei der nichtlinearen Analyse lieferte Informationen über die tatsächlichen Mechanismen der Lastübertragung zwischen Steinen und Mörtelfugen. Mit dem Mikro-Modell war es möglich, das nichtlineare Verhalten von Lehmsteinmauerwerk vorherzusagen. Es stellt somit ein geeignetes Werkzeug für die Untersuchung der Versagensmechanismen von Lehmsteinmauerwerk dar. Allerdings sind aufgrund der Komplexität des Modells für die Beschreibung der Stein/Mörtel-Schnittstelle und die hohe Anzahl an erforderlichen mechanischen Parametern umfassendere Untersuchungen notwendig. Die zukünftige Forschung wird sich daher einerseits auf die Verfeinerung der numerischen Modelle und andererseits auf die Simulation komplexer Belastungssituationen und Gebäudekomponenten konzentrieren.