Compressive strength
The resistance of a material or building material to the action of compressive forces is called compressive strength .
The compressive strength is the quotient of breaking load and cross-sectional area A of a test specimen . It is normally expressed as the force per area (in N / mm² ), i.e. it has the unit of mechanical stress . If the applied compressive stress is greater than the compressive strength of a body , it will be destroyed.
Most materials differ in their compressive and tensile strength , e.g. B. rocks or cast iron . An example of a material that can only absorb compressive forces but not tensile forces when there is no limitation of the transverse strain is sand .
The compressive strength is tested in the laboratory , the test methods are specified in standards ( DIN , ÖNORM ). Depending on the type and implementation of the pressure tests, a distinction is made:
- uniaxial compressive strength (the test specimen can move in both lateral directions)
- biaxial compressive strength (the deformation is prevented in one of the two lateral directions)
- triaxial compressive strength (the deformation is prevented in both lateral directions).
The compressive strength increases in this order.
The compressive strength can also be directional , e.g. B. in
- Rock , if the rock is crisscrossed or shale .
- Wood that usually has a higher compressive strength in the direction of the wood fibers or the trunk than perpendicular to it.
Applications
The exploration of the deep sea, for example, must take into account the extreme pressure conditions for all materials used. The yield point of the materials is relevant here. Titanium and glass stand out in particular.
Typical values
| material | R s [ MPa or N / mm 2 ] |
| bone | 150 |
| Hard aggregate screed 65 | 65 |
| Epoxy resins | 60 - 75 |
| Ice (0 ° C) | 3 |
| Styrofoam | ~ 1 |
| Ceramic and mineral substances | |
| concrete | 20 - 80 |
| (Thin-bed) mortar | 15-30 |
| historical mortar with hydraulic binder | 5 - 40 |
| porcelain | 500 |
| Reinforced concrete B 25/35 | 25/35 |
| Stoneware tiles | 250-300 |
| Stoneware and split tiles | 180-250 |
| Cement screed ZE 12/20/30 | 12/20/30 |
| Cement mortar MG III | 10-20 |
The compressive strengths of opus caementicium are specified with values of 5 to 40 N / mm² depending on the type of component or type of use and the care taken during installation. With values of approx. 1.53 to 2.59 kg / dm³ for air-dried samples, the gross density is in the range of today's concrete (2.0 to 2.4 kg / dm³). On the other hand, opus caementicium has a significantly higher water absorption capacity than today's concrete with around 20.2 to 54.6% by volume in contrast to 10 to 15% by volume.
See also
- Material testing , strength
- Shear strength , breaking strength , yield strength
- Splitting tensile strength , bending tensile strength
literature
- Ulrich Smoltczyk (Ed.): Grundbau-Taschenbuch. Part 1, Geotechnical Basics, Wilhelm Ernst & Sohn, 2017, ISBN 978-3-433-03151-3 .
Individual evidence
- ↑ Values for stoneware tiles, stoneware and split tiles, hard aggregate screed, epoxy resins, concrete, reinforced concrete, thin-bed mortar, cement screed and cement mortar from: "Technical information" from the 2002 price list of "Deutsche Steinzeug" or "AgrobBuchtal" ceramics, page 229
Web links
- Robex Alliance: Space Meets Deep Sea , accessed November 11, 2016.
- Influence of intrinsic moisture on the compressive strength of concrete (accessed on December 13, 2019)
- Significance of the stone compressive strength class (SFK) (accessed on December 13, 2019)
- Building materials properties (accessed December 13, 2019)
- Electric pipes (accessed December 13, 2019)