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Organisationseinheit der BAM
Measurement of Water Vapour Sorption and Humidity - A Survey on Measuring Methods and Standards
(2005)
Der Einsatz von Sekundärrohstoffen im Betonbau kann einen wesentlichen Beitrag zu einer nachhaltigen Ressourcenwirtschaft im Bauwesen leisten. Sekundärrohstoffe (Recycling-Baustoffe, RC-Baustoffe) finden bereits Anwendung als Roh- bzw. Brennstoffe in der Portlandzementklinkerherstellung, als Zementbestandteile, als Betonzusatzstoffe sowie als sekundäre Gesteinskörnungen in Beton. In einem Teilprojekt des DAfStb/BMBF-Verbundforschungsvorhabens 'Nachhaltig Bauen mit Beton' wurde das Einsatzpotenzial von Sekundärrohstoffen in Beton untersucht. Hierbei spielen sowohl technische als auch ökologische und ökonomische Fragestellungen eine wichtige Rolle. Vor diesem Hintergrund wurde eine Bewertungsgrundlage mit ganzheitlicher Betrachtung von Nachhaltigkeitsaspekten (Technik, Ökologie, Ökonomie) ausgearbeitet. Dieses Bewertungskonzept umfasst die vier Bewertungsschritte: I. Grundsätzliche Überlegungen, II. Vorteile für das nachhaltige Bauen, III. Alternative Bewertungswege und IV. Sensitivitätsanalysen. Das Bewertungskonzept wurde am Beispiel der bereits im Betonbau eingesetzten rezyklierten Gesteinskörnungen entwickelt.----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Nowadays there are several applications of secondary mineral materials and residues. In the framework of the German research project 'Sustainable Building with Concrete', a concept to assess the applicability of already used and new secondary materials in concrete has been developed. It considers sustainability aspects and includes the following four assessment steps: I. Basic considerations, II. Advantages for sustainable construction, III. Alternative paths of application, and IV. Sensitivity analysis. Depending on changing technical, ecological and economic aspects, the assessment has to be performed for changed technical, ecological and economic conditions as necessity arises.
A silica residue from waste treatment of chlorosilane production was used together with solid sodium aluminate to test its applicability for the production of one-part geopolymers. The blend was activated with water and cured at 70 °C. The degree of reaction and strength were determined after 1, 3, and 7 days. The reaction products were analyzed by XRD and SEM/EDX. Until the third day of curing the degree of reaction of the residue reached 51 % and the strength was 8.9 MPa. The reaction product was identified as geopolymer containing zeolite A. Thus, the results confirmed that the residue may be used in the production of geopolymers. However, after 3 days of curing no further progress of reaction was observed and the strength slightly decreased, which was attributed to changes in the structure of the geopolymeric gel. It was further observed that even harsh vacuum drying left some water (presumably zeolitic water and surface hydroxyl groups) in the geopolymer.
Recycling materials from building construction can currently not be adequately recycled. Reasons for this are their considerable heterogeneity in terms of materials composition and high fine partide content. Recycling as filling material and in the construction of waste disposal facilities, or as landfill, will in future no longer be possible in view of the stringent application of the German law of lifecyde management and/or the steady decrease of waste-disposal capacities. In this context, the joint research project “lightweight aggregates,” supported by the German Federal Ministry for Education and Research, a technology for manufacturing lightweight aggregates was developed.
Die Ressourcenverknappung und steigende Preise rücken nachhaltiges Wirtschaften und die Wiederverwertung von Abfällen in den Blickpunkt der Forschung. Bauabfälle sind in Deutschland – mit 72,4 Mio.t im Jahr 2004 – der größte Abfallstrom. Es wird ein Überblick über den Stand der Technik zur Aufarbeitung und Verwertung von Bauabfällen gegeben und die Anforderungen an Bauabfälle, die als Sekundärrohstoff eingesetzt werden sollen, diskutiert. Die Forschung im Baustoffrecycling bezieht sich sowohl auf neue Aufbereitungstechniken als auch auf die Charakterisierung der Recyclingmaterialien sowie auf deren Einfluss auf die Betonqualität. Die Eignung und Verwertung von Bauabfällen als Sekundärrohstoffe für Baustoffe wird anhand ihrer chemischen Zusammensetzungen mit Hilfe von ternären Diagrammen diskutiert.----------------------------------------------------------------------
An overview about quantity of construction and demolition waste (CDW) and a state of the art of the reuse is given. The technology is described, which is applied for the processing of CDW in a stationary plant. The requirements on recycled aggregates, which shall be used in road construction or in manufacturing of concrete, can be divided in such related to the material and physical properties and such related to the environmental properties. The rules give guidance on the composition with the aim of excluding the constituents with unfavourable features. The environmental standards which yet in discussion are give threshold of the leachable components in recycled aggregates. The material potential of building waste is discussed. Information on the chemical composition of recycled materials is compared with the composition of pure materials. With the aid of ternary charts such building materials are identified, in which the recycled materials can be used as recycled feedstock.
The interaction of municipal solid waste incinerator bottom ash (MSWI bottom ash), when utilized as an aggregate in concrete, with the cement matrix was investigated. The most prominent reaction observed in lab and field concrete was the formation of aluminium hydroxide and the release of hydrogen gas from aluminium grains reacting in the alkaline environment. The expansive aluminium reaction was identified as a main cause of extensive spalling on the concrete surface. Due to the higher content of bottle glass as part of the ash, in all samples, reaction products of an alkali-silica reaction (ASR) could be observed as well. However, damage due to ASR were less severe than those caused by the aluminium reaction. The expansion rates were low and only a few of the lab samples showed cracking. Microstructural analysis of the samples indicated clearly that a large quantity of the alkali-silica gel which was formed was accommodated in the pores and voids without exerting any strain on the material.
Mineral building materials are generally heterogeneous and porous solids. Their engineering properties are closely associated with their porosity and pore-size distribution, which can be studied by mercury intrusion. The entire pore-size distribution curves are used to determine changes in the pore structure of a material class in a qualitative way. Certain parameters derived from pore-size distributions can be correlated to engineering properties. These key values are applied as criteria to evaluate the quality and durability of a building material. However, because of the heterogeneity of natural and artificial building materials and the influence of moisture content on their pore structure the results are strongly affected by preparation conditions such as sampling and drying. A correct analysis requires a knowledge of these effects. The paper describes the use of mercury porosimetry to study mineral building materials such as cementitious materials, bricks, and renderings. Furthermore, the influence of preparation effects on the precision of measurements is discussed.