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Lightweight concrete with recycling aggregates made from masonry rubble and rubble-clay mixtures
(2018)
Structural lightweight concrete is a construction material composed primarily of lightweight aggregates (LWA), cement and water. Most LWA are produced by thermal treatment of natural raw materials such as clay and shale today. In addition to the high energy costs thereby incurred, the availability of suitable raw materials is limited. An alternative is the use of recycling LWA made from mineral construction and demolition waste. Recycling LWA made from masonry rubble and rubble-clay mixtures were studied in two different research projects. The technology pursues the idea of feedstock recycling, which means the recycling is based on the chemical and mineralogical composition of the masonry rubble and clay. The recycling LWA are produced in a multistage manufacturing process by thermal hardening in laboratory and pilot scale. Their particle bulk densities and particle strengths vary between 600 and 2000 kg/m³ and 1.5 and 13 MPa, respectively. Their equivalence to traditional LWA was proven in comprehensive tests of the aggregates themselves as well as the mortars and concretes made therefrom. Our contribution reports on the results of the characterization of the recycling aggregates compared to expanded clays and the studies on LWA concretes.
At present, heterogeneous and fine-grained masonry rubble can only be recycled at very low level. To overcome this limitation, the material was employed as feedstock for the production of lightweight aggregates in a thermal process similar to that used in the manufacture of expanded clay and expanded slate. To that end, the fundamental suitability of masonry rubble as a raw material was evaluated. Experiments were carried out which indicated that lightweight granules with defined, adjustable properties similar to those of natural-material-based aggregates could be manufactured from masonry rubble. Structural lightweight concretes produced with these secondary aggregates achieved comparable performance to lightweight concretes produced with conventional expanded clay. Lightweight recycled building material aggregates represent a product that hardly requires any primary resources in its manufacture. In principle, the technique also seems to be well suited for high-quality recycling of other mineral waste materials.
Most lightweight aggregates (LWA) are produced by thermal Treatment of natural raw materials such as clay and shale. In addition to the high energy costs thereby incurred, the availability of suitable raw materials is limited. Other LWA manufactured from industrial by-products and wastes do not always meet the quality criteria for use in high-Quality lightweight concrete. A real alternative is the use of novel lightweight aggregates (referred to as LWA, aggregates and granules) made from mineral construction and demolition waste. An appropriate manufacturing technology has recently been developed in the framework of a German research project /1, 2/. Masonry rubble of variable grain size containing different amounts of brick material (25 to 70 %) serves as raw material. The LWA are obtained in a multistage manufacturing process by a thermal or hydrothermal treatment, which causes the expansion and the hardening of the material. The novel LWA meet the acceptance criteria for conventional lightweight aggregates. They are suitable for the production of lightweight concrete /2-6/. However to create tailor-made LWA from masonry rubble, the novel expanded materials and the influence of manufacturing conditions have to be understood in more detail. This paper reports on ongoing investigations of the chemico-mineralogical composition and microstructure of the novel LWA and focuses on the results of Chemical analyses, XRD, ESEM, TG/DTA and fusibility tests.
Heterogene und feinkörnige Bauabflle aus Mauerwerkbruch lassen sich heute nur auf einem sehr geringen Qualittsniveau verwerten. Um diese Situation zu überwinden, wird deren Verwendung als Ausgangsstoff für die Herstellung von leichten Gesteinskörnungen vorgeschlagen, die hnlich wie Blhtone und Blhschiefer in einem thermischen Prozess erzeugt werden. Dafür wurde zunchst die grundstzliche Eignung von Mauerwerkbruch bewertet. Es folgten experimentelle Untersuchungen, in welchen nachgewiesen werden konnte, dass Leichtgranulate mit definierten, einstellbaren Eigenschaften aus Mauerwerkbruch herstellbar sind. Sie sind in ihren Eigenschaften den leichten Gesteinskörnungen aus natürlichen Rohstoffen mindestens ebenbürtig. Die daraus hergestellten, gefügedichten Leichtbetone erzielen durchweg vergleichbare Werte wie die Leichtbetone mit herkömmlichem Blhton. Leichtgranulate aus Mauerwerkbruch stellen ein Produkt dar, dessen Herstellung nahezu ohne Primrrohstoffe auskommt. Das Verfahrensprinzip scheint außerdem prdestiniert für die hochwertige Verwertung auch anderer mineralischer Reststoffe zu sein.---------------------------------------------------------------------------------------------------------------------------------------------------
Production of lightweight aggregate from masonry rubble. At present, heterogeneous and fine-grained masonry rubble can only be recycled at very low quality. To overcome this limitation, the material was employed as feedstock for the production of lightweight aggregates in a thermal process similar to that used in the manufacture of expanded clay and expanded slate. To that end, the fundamental suitability of masonry rubble as a raw material was evaluated. Experiments were carried out which indicated that lightweight granules with defined, modifiable proper-ties on a par with to those of natural-material- based aggregates could be manufactured from masonry rubble. Structural lightweight concretes produced with these secondary aggregates achieved comparable performance to lightweight concretes produced with conventional expanded clay. Lightweight recycled building material aggregates represent a product that hardly requires any primary resources in its manufacture. In principle, the technique also seems to be well suited for high-quality recycling of other mineral waste materials.