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Vermiculite is a 2:1 clay, meaning it has two tetrahedral sheets for every one octahedral sheet. It is a limited-expansion clay with a medium shrink–swell capacity . Vermiculite has a high cation-exchange capacity (CEC) at 100–150 meq /100 g.
An aerogel material can range from 50% to 99.98% air by volume, but in practice most aerogels exhibit somewhere between 90 and 99.8% porosity. [12] Aerogels have a porous solid network that contains air pockets, with the air pockets taking up the majority of space within the material.
Clay minerals can be classified as 1:1 or 2:1. A 1:1 clay would consist of one tetrahedral sheet and one octahedral sheet, and examples would be kaolinite and serpentinite. A 2:1 clay consists of an octahedral sheet sandwiched between two tetrahedral sheets, and examples are talc, vermiculite, and montmorillonite.
Lightweight expanded clay aggregate (LECA) or expanded clay (exclay) is a lightweight aggregate made by heating clay to around 1,200 °C (2,190 °F) in a rotary kiln. The heating process causes gases trapped in the clay to expand, forming thousands of small bubbles and giving the material a porous structure.
In a study comparing lightweight expanded clay aggregate (LECA) and expanded vermiculite (EV), two materials used to make concrete, to a mycelium grown brick, the mycelium grown brick was found to be a better insulator. [13] These results are similar when comparing a different mycelium based composite with extruded polystyrene.
2:1 clay minerals crystallographic structure made of three superimposed sheets of tetrahedra-octahedra-tetrahedra (TOT layer unit), respectively. The 2:1 layer (TOT) structure consists of two silica (SiO 2) tetrahedral (T) layers which are electrostatically cross-linked via an Al 2 O 3 (), or Fe 2 O 3, octahedral (O) central layer.
Vermiculite. Like perlite, vermiculite is a mineral that has been superheated until it has expanded into light pebbles. Vermiculite holds more water than perlite and has a natural "wicking" property that can draw water and nutrients in a passive hydroponic system.
The expanded material is a brilliant white, due to the reflectivity of the trapped bubbles. Unexpanded ("raw") perlite has a bulk density around 1100 kg/m 3 (1.1 g/cm 3 ), while typical expanded perlite has a bulk density of about 30–150 kg/m 3 (0.03–0.150 g/cm 3 ).