Poroznost

Poroznost is the fraction of a material's volume that is occupied by voids or pores. In geology, hydrology, and construction materials science it is defined as V_pore / V_total and is typically expressed as a dimensionless fraction or percentage. Poroznost determines how much fluid a rock or concrete can store and, together with permeability, governs potential fluid flow.

Poroznost is not uniform; it is classified as primary porosity, formed during deposition or cementation, and secondary porosity, produced by dissolution, fracturing, or mineral alteration. Of the porosity present, only the connected, open porosity is usually available for fluid flow; the remaining spaces are isolated and do not contribute to permeability. The term effective porosity refers to the connected portion.

Measurement and estimation: laboratory methods include mercury intrusion porosimetry, gas adsorption, and density-based methods; imaging and imaging-based porosity estimates from CT. Field methods include core analysis, borehole logging (porosity logs, NMR), and seismic measurements.

Significance and applications: poroznost controls groundwater storage and movement, hydrocarbon reservoir capacity, and the durability and performance of construction materials. Porosity alone does not determine flow; pore connectivity and throat sizes control permeability.

Typical ranges vary by rock type: sandstone often 10–25%, limestone 2–15%, shale 3–10%; these values can be higher in fractured or dissolved rocks. In soils and concrete, poroznost also influences stability and transport of water and pollutants.