Glossary term
Compressive Strength
The maximum compressive stress a material, specimen, or structural element can withstand before crushing, yielding, instability, or unacceptable deformation.
Definition
quantityThe maximum compressive stress a material, specimen, or structural element can withstand before crushing, yielding, instability, or unacceptable deformation.
Compressive strength is a material and test-dependent strength measure. It is especially important for concrete, ceramics, foams, polymers, composites, masonry, geological materials, and brittle materials whose compressive capacity differs strongly from tensile capacity.
Compressive strength is the stress level associated with failure or specified deformation under compressive loading. It is calculated from applied compressive force divided by specimen cross-sectional area, but the interpretation depends strongly on material class and test method.
Engineering role
Compressive strength controls design in concrete columns, masonry, ceramics, bearing surfaces, foams, cores of sandwich panels, rocks, soils, and many composite structures. Some materials are much stronger in compression than tension. Others fail by shear bands, barreling, crushing, microcracking, or instability rather than by a clean fracture plane.
Testing
Compression tests require defined specimen geometry, loading rate, end conditions, alignment, platen friction, temperature, moisture condition, and failure criterion. Concrete cylinders, polymer specimens, metallic coupons, and composite compression tests are not directly interchangeable. Slender specimens may buckle before the material reaches its true compressive strength, so geometry and support are part of the result.
Design interpretation
Compressive strength should not be confused with compressive stiffness, allowable stress, or buckling load. A short stocky block may crush, while a long slender column of the same material may buckle at much lower stress. In ductile metals, yield strength in compression may be more relevant than ultimate crushing strength. In brittle materials, flaw population and confinement can dominate.
Factors affecting value
Important factors include porosity, moisture, curing, microstructure, fibre orientation, strain rate, temperature, defects, confinement, and manufacturing route. Concrete gains strength with curing but is sensitive to mix, water-cement ratio, aggregate, and test age. Composites can be sensitive to fibre waviness and matrix shear. Ceramics and rocks are sensitive to flaws and confinement.
Common mistakes
Common mistakes include using compressive strength from a small specimen for a structural member without checking scale, stability, and load eccentricity. Another error is assuming compressive and tensile properties are symmetric. Engineers should also avoid comparing published values unless specimen standard, failure criterion, and conditioning are the same.