ULTRA LIGHTWEIGHT CONCRETE
Ultra-lightweight concrete with a unit weight or density of 600 to 31000 kg / m is made from a mixture of cement, sand (left for concrete with a unit weight or density of less than 600 kg / m3), and extended-polystyrene. One to six-millimeter diameter beads.
This concrete has high thermal insulation efficiency and is mainly compatible with prefabricated non-load bearing panels, hollow and solid blocks, lightweight sandwich panels, and highway construction as a sub-base that threatens the subgrade’s stability.
Polystyrene beads or foam making is essentially a polymerization process that utilizes a liquid styrene monomer dispersed in aqueous media containing a foaming or expanding agent and a polymerization catalyst.
Foam or extended bead products can be treated with bromine solutions to improve fire retardancy and self-extinguishing properties. Enlarged beads usually have a density between 12 and 25 kg / m3, however, the foil form produces a density of 330 to 75 kg / m.
The most commonly used size range for extended beads is 1 to 3 mm. When exposed to sunlight, foam or beads will deteriorate and cause a distinct yellow color.
Extended-polystyrene concrete mixtures can be designed to have compressive strengths of 15 to 20 MPa at a concentration of 1600 kg / m3.
The blended design aims to achieve an economical and optimal balance between density, thermal insulation, and energy. Extended-polystyrene beads are electrostatically charged during processing, which makes it difficult to be hydrophobic when mixed.
Separation tendencies can be overcome by binding agents (usually water-emulsified epoxies and aqueous dispersions of polyvinyl propionate) and controlling the liquidity of the paste or mortar.
The compressive strength and thermal insulation properties of extended-polystyrene concrete increase with its density. Due to the low specific heat capacity, the heat of the hydration of the cement causes a greater and more rapid increase in the temperature of this concrete, which sets it up faster than conventional aggregated concrete and accelerates hardening.
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Setting and hardening rates can be controlled by selecting suitable cement and using water-reducing blends. Traditional feasibility tests include the slump test, the compacting factor test. The Vee-Bee test and the Flow Table test are not appropriate in the case of extended-polystyrene concrete.
Conventional techniques can be used to cast and place extended-polystyrene concrete. The mechanical properties of extended polystyrene concrete are a function of density in the case of other lightweight aggregate concrete but have relatively low values. The elastic and shrinkage deformations are substantially greater than the normal weight of concrete.
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