Sand-lime brick
| Sand-lime brick | |
|---|---|
|
|
| origin | |
| Material properties | |
| Thermal conductivity λ | 0.56 - 1.30 W / (m K) |
| Specific heat capacity c | approx. 1 kJ / (kg K) |
| Bulk density ρ | 1200 to 2200 kg / m³ |
| commitment | |
Sand-lime brick (also called sand-lime brick or sandstone brick ) is an artificially produced brick made of sand and hydrated lime silicate as a binding agent . Niederlehme in Brandenburg is one of the oldest sand-lime brick production sites in Germany . In Germany, sand-lime bricks are often sold under the KS * brand.
Manufacturing
The doctor and scientist Anton Bernhardi is considered to be the inventor of the manufacturing process for artificial sand-lime bricks . He was looking for an inexpensive building material for social housing and agriculture. In 1856 he wrote concrete instructions for this. A first patent for the production of a sand-lime brick was given to Dr. Michaelis granted.
In the industrial manufacture of sand-lime bricks, quicklime ( calcium oxide ) and sand (mainly quartz sand) are mixed in a ratio of 1:12 with the addition of water and fed into reactors. When the quicklime has been converted into hydrated lime with water , the mixture is brought to press moisture in the post-mixer and then shaped into stone blanks using hydraulic presses. The blanks are hydrothermally hardened in special steam pressure vessels, the autoclaves , at temperatures of approx. 200 ° C under saturated steam pressure , i.e. at a pressure of approx. 16 bar, for a period of 4 to 8 hours. This and the basic Ca (OH) 2 environment lead to a detachment of the silica from the surface of the sand grains, which then reacts with the hydrated lime. Depending on the proportion of CaO, SiO 2 and H 2 O, tobermorite and / or other calcium silicate hydrate phases are formed (called CSH phases for short; x CaO · y SiO 2 · z H 2 O). There are no pollutants.
The sand-lime bricks are produced in thin formats (DF) and normal formats (NF), whereby an additional distinction is made depending on their height and cross-section (e.g. solid, perforated or block bricks). Large-format sand-lime bricks are referred to as plan elements. They can assume lengths of 998 mm and heights of up to 623 mm.
Both stones for normal mortar (joint thickness 12 mm) and flat stones and elements for thin-bed mortar (joint thickness 1 - 3 mm) are offered.
The designation of the sand-lime bricks is based on DIN 106 depending on the type of stone, the main DIN number, the type of stone, the compressive strength class, the gross density class and the format abbreviation. For example:
Sand-lime brick DIN 106 - KS 16 - 1.8 - 2 DF.
application
Sand-lime brick is used in shell construction for interior and exterior walls. It is comparatively heavy (high density class , RDK) and therefore has good sound insulation and heat storage properties. Due to its high thermal conductivity , single-shell (monolithic) walls have a high heat transfer and heat transfer coefficient - therefore the combination with insulating materials is common . The non-flammable building material (building material class A1 according to fire protection standard DIN 4102-4) is classified as a fire wall from a thickness of 17.5 cm with a bulk density class ≥ 1.8 in DIN 1996-1-2 / NA. Thanks to the high stone compressive strength classes (SFK), the KS masonry can withstand high loads and can be carried out in a load-bearing capacity of 11.5 cm. Sand-lime bricks according to DIN 106 have a low dimensional tolerance due to the manufacturing process. For stone formats ≥ 2DF, deviations from individual values may not exceed ± 4 mm.
KS facing bricks , KS facing bricks and brick slips are classified as frost-resistant sand-lime bricks . They are mainly used for exposed masonry on exterior and interior walls. All stone properties (stone types, formats, dimensions, stone strength classes , bulk density classes ) are regulated in DIN 106.
Sand-lime brick exterior walls are usually designed as multi-layer exterior wall constructions ( functional wall ). Each layer specifically meets the requirements placed on the wall construction. The functions of load-bearing capacity (statics), sound insulation , fire protection and summer heat protection are fulfilled by the heavy KS masonry, requirements for winter heat protection are fulfilled by the lightweight thermal insulation materials. This creates functional walls that can be adjusted to the required level of requirements without having to accept losses in other areas (sound insulation) through one-sided optimization (e.g. thermal insulation).
Sand-lime brick masonry can temporarily buffer heat and moisture and release them again with a delay.
As a facing brick, there is the sand-lime brick in the surface structures:
processing
In the case of high heat, very dry stones must be pre-moistened so that the mortar does not "burn" during application (ie the moisture in the mortar is drawn away too quickly into the very absorbent stone). And vice versa, as with all bricks, the fresh masonry must be protected from excessive moisture and frost, e.g. B. by covering with tarpaulins. Masonry damaged by frost must be removed before the masonry continues.
Facing bricks are sometimes supplied with pre- impregnation at the factory. This largely counteracts contamination during transport, storage and processing. The mortar can only be impregnated in the finished masonry. If the KS veneer is subsequently impregnated, the recommendations of the supplier must be observed in order to ensure compatibility with any pre-impregnation.
According to VOB / C ATV DIN 18330, the use of acidic cleaning water is not permitted, as this damages the structure of the sand-lime brick.
Advantages and disadvantages
Advantages:
- high pressure capacity for easy anchoring of heavy loads
- good ecological balance (low energy consumption, low resource consumption)
- good building biology properties because it regulates moisture and stores heat
- high sound insulation
- high water vapor storage capacity
- non-combustible building material (building material class A1)
Disadvantage:
- high heat transfer (use of thermal insulation materials necessary)
- high cleaning effort (use of conventional agents for ceramic building materials not possible)
- uneven color image in different production batches
The "Xella" case
According to issue no. 29 of July 10, 2008 of the magazine Stern , Haniel Bau-Industrie (since 2002 Xella ) produced low-quality sand-lime bricks in three plants for around eight years and, according to the Handelsblatt, sold them under the “KS” brand until 2006; these were later built into around 45,000 houses. The quicklime required in the production process has been at least partially replaced by a binding agent that is created during the flue gas desulphurisation of power plants - although the Federal Association of Sand Lime Bricks had warned against it.
The report comes, as the statement of the Bundesverband Kalksandsteinindustrie e. V. from 1987, to the result that walls made with these sand-lime bricks could lose their load-bearing capacity as a result of strong moisture exposure to such an extent that they can no longer safely divert the loads that are attributable to them as part of the overall structure and finally also the overall structure of the building may no longer be able to guarantee a sufficiently high level of overall stability over the long term by shifting loads. According to this report, if there is sufficient moisture penetration into the masonry, the affected walls can be completely destroyed, with the result that the stability of the entire building can be endangered.
If basement insulation or plaster was not used, dangerous cracks in the masonry could occur, Xella admitted. Xella has not yet confirmed the number of 45,000 houses given by the star . In the winter of 2011, Xella reported a number of 382 previously damaged houses. In 2013, the expert Dekra spoke of a total of 430 cases. Since the defective sand-lime bricks were exclusively produced in three plants on the Lower Rhine and are usually only transported over short distances, damage to the Lower Rhine, the western Ruhr area and the neighboring Münsterland is to be expected. There were also isolated cases of damage in Frankfurt a. M. discovered.
Similar materials
literature
- Wilhelm Scholz, Wolfram Hiese (Ed.): Knowledge of building materials . Werner-Verlag, Cologne 2007, ISBN 978-3-8041-5227-4 .
- Günter Neroth, Dieter Vollenschaar (ed.): Wendehorst building materials. Basics - building materials - surface protection . Vieweg + Teubner Verlag, Wiesbaden 2011, ISBN 978-3-8351-0225-5 .
- Harald Knoblauch, Ulrich Schneider: Construction Chemistry . 6th edition. Werner Verlag, Neuwied 2006, ISBN 978-3-8041-5174-1 .
- Roland Benedix: Construction chemistry for the bachelor's degree. Modern - competent - compact . 3. Edition. Springer Vieweg, Wiesbaden 2017, ISBN 978-3-658-18495-7 >.
- DIN V 106: 2005. Sand-lime bricks with special properties . Beuth Verlag, Berlin 2005.
Web links
- Bundesverband Kalksandsteinindustrie e. V.
- European Calcium Silicate Unit Producers Association (ECSPA)
- Expertise: exterior walls made of sand-lime brick
Individual evidence
- ↑ https://www.ks-original.de/de/ks/die-marke-ks
- ↑ A look back: The origins of the traditional brand KS-ORIGINAL. - The sand-lime brick industry - pioneer of innovative masonry construction ( Memento from January 12, 2014 in the Internet Archive ) In: ks-original.de
- ^ German Institute for Standardization: DIN V 106: 2005. Sand-lime bricks with special properties. Beuth Verlag, Berlin 2005.
- ^ A b Rolf-Herbert Peters: Building scandal: The trace of the stones. In: stern.de . July 20, 2008, accessed February 13, 2015 .
- ↑ Your house made of sand-lime brick - built by HANIEL / Xella with "crumbling stones"?
- ↑ Markus Peters: Crumbling sand-lime bricks: legal deadline for damages expires. In: DerWesten. Funke Medien NRW, December 21, 2011, accessed on May 8, 2018 .
- ↑ Frank Messing: Haniel stops payments for new Bröselstein victims. In: DerWesten. Funke Medien NRW, April 8, 2013, accessed on May 8, 2018 .
- ↑ Dirk Hautkapp: The sand-lime brick files. In: derwesten.de. July 9, 2008, accessed February 13, 2015 .
- ↑ Building materials manufacturers sold inferior sand-lime bricks for years. In: doit-tv.de. July 9, 2008, accessed February 13, 2015 .
- ↑ Christoph Schlautmann: Xella leaves Haniel with business risks . In: handelsblatt.com . July 11, 2008, accessed February 13, 2015 .