Novel mechanical behaviour of perlite/sodium silicate composites

A novel mechanical behaviour of perlite/sodium silicate composites is studied with the benefits of a new manufacturing method based on the perlite particle buoyancy. The objective was to develop perlite composites and to understand their quantitative relations between manufacturing parameters, volume fractions of constituents, and properties. For the composites development, sodium silicate dehydration behaviour was characterised with phases formed during dehydration i.e. liquid, gel, and solid phases. The water loss-time curve for dehydration was found to have three distinctive parts - linear part at an early stage for liquid phase, followed by non-linear part during a period between commencements of gel and hydrated solid phase formations, and then another linear part for hydrated solid phase. Foams as composites were manufactured with diluted sodium silicate binder for a density range of 0.2-0.5 g/cm3. One of practical milestones achieved for composite properties without reinforcement was a density of 0.3 g/cm3 at a compressive strength of 1 MPa. Manufactured perlite/sodium silicate composites are analysed/discussed for understanding from three different perspectives i.e. manufacturing parameters (i.e. binder content, compaction pressure, and compaction ratio), properties (i.e. particle size, density, compressive strength, and modulus), and volume fractions of constituents. A rule of mixtures applicable for perlite composites for a constant compaction ratio was developed in comparison with that for particulate composites with non-compaction. It may be a basis for further development for variable compaction ratio in the future.