Glass block
Glass blocks or glass blocks are cuboid components that are used to create translucent and non-load-bearing walls in the interior and exterior. If, on the other hand, they are arranged horizontally ( light shaft cover or skylight ), so-called concrete glass must be used. Together with the building materials concrete and steel , a glass reinforced concrete can be produced in this way , which is also suitable for absorbing loads (e.g. vehicle loads).
features
The glass blocks themselves consist either of two half-shells made of pressed glass that are fused or cemented together and are therefore hollow or are made directly as full glass blocks. They are available in different formats and different colors (clear or colored glass) in stores. Due to their structure or surface quality, they are usually so optically distorted that they are translucent, but can also be used as privacy screens. They are used to fill wall openings or open translucent walls.
Like other masonry , they can be built up with mortar or (usually in larger series) manufactured as prefabricated elements. Reinforcing steel is laid in the joints to increase stability . But there are also other mortar-free installation systems that are particularly suitable for DIY enthusiasts . The thickness (and thus the wall thickness) is usually 8 or 10 cm, but also up to 16 cm for thermal insulation or fire protection bricks. As accessories, special stones inserted into movable metal frames are available with which ventilation flaps can be created, which, however, cannot be particularly large due to the weight of the stones, so that other ventilation options must be provided if necessary.
They were often used in the 1960 / 70s on the outside walls of stairwells or in bathrooms. Today they are being rediscovered, especially as a design tool, but mainly in interiors, as the so-called thermal insulation bricks still have relatively poor insulation properties.
The white coating of the side surfaces of the glass block made by the manufacturer illuminates the view, prevents the grout from being seen and improves its adhesion.
The standard dimensions of the square format are 190 × 190 × 80 mm and 240 × 240 × 80 mm for the classic glass blocks with insulation values of approx. 2.80 W / (m² · K). For applications with higher insulation values, glass blocks with a lower heat transfer coefficient with the trade names HTI-Block (1.8 W / (m² · K)) with the dimensions 190 × 190 × 160 mm and Q19 Energy Saving (1.5 W / (m² · K)) are recommended . K)) available in 190 × 190 × 80 mm.
In the past, “normal format” glass blocks with dimensions of 240 × 115 × 80 mm were also common. The term refers to the normal format of masonry bricks .
Installation
Installation according to DIN 4242
According to the standard, cement mortar (1 part of cement, 3 parts of sand with a grain size of up to 4 mm) is used. A maximum of 20% of the cement content may be replaced by hydrated lime or trass for better workability . The width of the joints is 10 - 30 mm (for stones larger than 240 × 240 mm at least 15 mm).
The grout should not be stiffer than the masonry mortar. It must be protected from drying out quickly and should be sufficiently tight to prevent moisture penetration into the mortar joints and possibly corrosion of the rebar. The mortar joints should be spread immediately after the glass blocks have been laid.
The use of cement mortar creates a very stiff bond that can hardly absorb temperature stresses. To avoid stress cracks, a glass block surface designed in this way should have a rectangular format and be provided with a surrounding edge made of reinforced concrete (with an approximately square cross-section, but max. The thickness of the blocks and max. 100 mm wide). The entire area is protected from the surrounding components by an elastic joint (e.g. dilation tape ) of min. 10 mm thick. The lateral guidance is achieved by means of stops on both sides or U-profiles or connecting means embedded in the elastic joint, which must not hinder thermal expansion.
Installation indoors (not in accordance with the standard)
Usually mortar with hydraulically hardening components is used for bricking, which stiffens more quickly but is less elastic.
If there is no separate flexible layer between the glass blocks and the surrounding building structure (as provided in the standard), the glass blocks should be walled in with a mortar that is more elastic than the surrounding wall surfaces. Since the glass blocks are often stiffer than the material of the surrounding wall, otherwise constraint stresses would result from temperature changes and building settlement.
The glass blocks do not remove any water from the mortar, so it takes significantly longer for the mortar used for masonry to set than when working with ordinary masonry blocks. Pure air-lime mortar also only hardens when exposed to carbon dioxide . This is also hindered by the dense glass blocks, so that the use of coarse aggregate should ensure that carbon dioxide can get through the pores of the mortar into the interior. When using air-lime mortar, you should also wait until the mortar has developed sufficient strength before spreading the joints.
In order to be able to set more than just one row of stones per day when using air lime or clay mortar , the mortar used must either be applied very stiffly or the stones must be supported by inserted blocks until the mortar can remove the load.
Glass blocks made of clear glass
Profiled glass blocks
Glass blocks in a honeycomb pattern
Colored glass blocks
Norms and standards
- DIN 18 175 - glass blocks
- DIN 4243 - concrete glass
- DIN 1045 - glass reinforced concrete (section 20.3)
literature
- Willi Bucher, Ralf Kopp: beboxx documentation of an artistic stroke of genius. Justus Liebig Verlag, Darmstadt 2007, ISBN 978-3-87390-241-1 .
- Ernst Seidl: Glasbaustein, in: Reallexikon der Deutschen Kunstgeschichte RDK, 2014: http://www.rdklabor.de/w/?oldid=95496
Web links
- Glass block , in: RDK Labor (online platform for art historical object research)
- Technical manual "Glass blocks" (PDF file; 773 KB)
- Institute for Building Materials : Building Materials - Glass , University of the Federal Armed Forces, Munich 2008 (PDF file; 2.1 MB)
- Extract from DIN 1045: Glass reinforced concrete