tiivistymine

Tiivistumine is a process by which a material’s density increases, typically through a reduction in volume or a rearrangement of its internal structure under applied stress. The term is used across disciplines such as geology, materials science, soil science, and engineering to describe how powders, soils, rocks, and other granular or porous materials become more compact over time or under load.

Common mechanisms include mechanical compaction, where external pressure reduces porosity; sintering, where particles fuse at elevated temperatures to form a denser solid; and diagenetic processes in sediments, where compression and cementation increase density as rocks form. Factors influencing tiivistumine include particle size and shape, moisture content, temperature, applied pressure, duration, and the presence of binders or cementing agents. The rate and extent of densification depend on the material, its initial structure, and the environmental conditions.

Contexts and examples

In soils, overburden pressure from overlying deposits or construction activities can reduce porosity and increase strength, affecting stability and runoff. In manufacturing, powder metallurgy and ceramics rely on hot or cold pressing and subsequent sintering to produce dense, strong components from fine powders. In geology, diagenesis and lithification densify sediments into sedimentary rocks through compaction and mineral cementation.

Consequences and measurements

Tiivistumine often leads to decreased porosity and permeability but increased mechanical strength. It can also cause volume changes and potential cracking if differential stresses occur. Key measurements include bulk density, density after compaction, porosity, and compression tests to assess stiffness and strength.

See also: compaction, densification, sintering, diagenesis, lithification, soil science.