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De Geetere L.,Belgian Building Research Institute
Proceedings of Forum Acusticum | Year: 2011

The rain noise behaviour of multilayered lightweight roof constructions is studied, in particular for membrane incorporating roof systems. This is done by a theoretical study, experiments and by simulations. Several effects are studied: adding a rigid elastic layer (polycarbonate sheet) in the cavity, adding porous layers in the cavity and adding rain retaining meshes on the top layer. Rain noise tests are performed on 10 roof systems according to ISO 140-18:2006 and are compared to simulations based on a rain noise extension of the Transfer Matrix Method for multilayered systems. The overall correspondence was quite satisfying and resulted in a correct ranking of the measured roof systems. This demonstrates that the model can be used in parameter sensitivity analysis and to further optimise multilayered lightweight roof systems.

Van Lysebetten G.,Catholic University of Leuven | Vervoort A.,Catholic University of Leuven | Maertens J.,Catholic University of Leuven | Huybrechts N.,Belgian Building Research Institute
Computers and Geotechnics | Year: 2014

The influence of soil inclusions on the mechanical behavior of deep soil mix material was studied by discrete element simulations in combination with some laboratory tests. The innovative aspect of the simulations was that individual fracturing in the heterogeneous material was modeled. It was observed that the reduction of strength and stiffness did not correspond to the weighted average of the UCS and Young's modulus, taking into account the volumes of the strong and weak material. The actual reduction was considerably larger, e.g., on average the strength was reduced by 13% and 50% for 1% and 10% of inclusions, respectively. Moreover, other parameters, such as the shape, number, and relative position of inclusions, also have an important influence on the strength and stiffness. First, sharp-ended inclusions have a more negative impact on the strength and stiffness than rounded inclusions. Second, one large inclusion reduces strength and stiffness more than three smaller inclusions with the same shape and accounting for the same total volume percentage. Finally, diagonally-located and more-concentrated inclusions have a more negative impact on the mechanical behavior than vertically-aligned and widely-spread inclusions. The results of the numerical simulations showed good agreement with the results of laboratory tests with regard to the effect on strength and stiffness as well as the observed fracture patterns. © 2013 Elsevier Ltd.

Courard L.,University of Liege | Michel F.,University of Liege | Pierard J.,Belgian Building Research Institute
Construction and Building Materials | Year: 2011

High workability together with a good resistance to segregation is needed for cement based composites, specifically fresh self-compacting mortars (SCM); in this prospect, the amount of coarse materials has to be reduced and replaced by fine material. Several limestone fillers are here compared and analysed. These by-products are issued from different industrial sectors, such as the aggregate and lime production industry (quarrying operations) and the ornamental stones industry (sawing operations). Particular attention has been paid to clay content, as consistency of fresh mortars was varying, while other physical characteristics like granulometry remained the same. Relationship between the physico-chemical properties of the fillers and the properties of fresh and hardened mortars are brought forward. Even if it may affect fresh properties of mortars, results clearly show that clay type and content has minor influence than limestone filler itself. © 2010 Elsevier Ltd. All rights reserved.

Laverge J.,Ghent University | Van Den Bossche N.,Ghent University | Heijmans N.,Belgian Building Research Institute | Janssens A.,Ghent University
Building and Environment | Year: 2011

Ventilation is ambiguously related to the energy saving rationale originating from the mitigation of global warming, the reaching of peak oil or health concerns related to fossil fuel burning. Since it makes up for about half of the energy consumption in well-insulated buildings, it is an attractive target for energy saving measures. However, simply reducing ventilation rates has unwanted repercussions on the indoor air quality. Two main strategies have been developed to reconcile these seemingly opposing interests: heat recovery and demand control ventilation. This paper focuses on the energy saving potential of demand controlled mechanical exhaust ventilation in residences and on the influence such systems may have on the indoor air quality to which the occupants of the dwellings are exposed. The conclusions are based on simulations done with a multi-zone airflow model of a detached house that is statistically representative for the average Belgian dwelling. Four approaches to demand based control are tested and reported. Within the paper exposure to carbon dioxide and to a tracer gas are used as indicators for indoor air quality. Both energy demand and exposures are reported and compared to the results for a standard, building code compliant, exhaust system, operating at continuous flow rates. The sensitivity of the control strategies to environmental and user variations is tested using Monte-Carlo techniques. Under the conditions that were applied, reductions on the ventilation heat loss of 25-60% are found, depending on the chosen control strategy (with the exclusion of adventitious ventilation and infiltration). © 2011 Elsevier Ltd.

Barns V.,Belgian Building Research Institute
34th International Conference on Cement Microscopy 2012 | Year: 2012

In Flanders (north of Belgium), a shortness of gravel is at hand. Therefore, the "Research committee" was established to financially support projects in order to find alternatives for gravel in all its applications. With this subsidy, VITO (Flemish Institute for Technological Research) and BBRI (Belgian Building Research Institute) worked together on the research of the mechanisms of pop-outs in concrete and of the nature of the damaging secondary granulates, i.e. residues coming from different industries such as bottom ashes, slag, ⋯. This kind of research is required in order to be able to estimate the risks when using stony residues in concrete. Once the causes identified, directives can be stated to minimize the risks of popouts. Pop-outs are esthetical and structural unwanted holes that appear on the concrete by flied off surface material. The ejection of concrete pieces is caused by the pressure that is built up around an aggregate as a result of physical or chemical reactions. After mineralogical, chemical and micro structural analysis, the selected aggregates were used to make concrete samples. Three tests were developed to which the samples were exposed in order to evoke pop-outs in the concrete. Of the four different tested aggregates, only one lead to pop-outs and this with only one of the developed tests. Examining the core of the created pop-outs with the electron microscope, the hydration of calcium oxides proved to be the cause. Other than pop-outs, the damaged samples showed also an intense Assuring from which the origin could be revealed by SEM-analysis. Several attempts to make thin sections of the concrete samples failed because of the hard slag components and up till now the cause of the Assuring remains a question mark.

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