Environmental and geotechnical properties of lightweight aggregates made of reused solid wastes

In the present research, a comprehensive experimental investigation was carried out for the geotechnical characterisation of new synthetic lightweight aggregates (SLAs) composed of reused biomass fly ash and waste plastics, namely high-density and low-density polyethylene (HDPE and LDPE), with a 50:50 fly ash-to-plastic ratio by weight. One-dimensional compressibility, creep properties, compaction features and stress-strain-strength behavior of SLAs were evaluated together with hydraulic conductivity and water absorbability. The fly ashHDPE aggregate was found to be less compressible upon loading than the companion material made of fly ash and LDPE and similar to traditional natural lightweight expanded clay aggregate. The values of creep coefficient (C-alpha epsilon) were slightly higher than those expected for dense sands, but comparable, or even lower, than those measured for other recycled materials. Peak friction angle (phi') and cohesion intercept (c'), determined by triaxial compression tests, were in the ranges 42.3 to 46.3 degrees and 1.3 to 8.6 kPa, respectively with the highest values concerning the fly ashHDPE aggregate. The hydraulic conductivity (k) was around 3 x 10(-44) x 10(-4) m/s, highlighting favorable permeability properties of both aggregates. Leaching tests and thermal stability analyses proved the sustainability of both aggregates from an environmental point of view. The results obtained in the present study demonstrate the suitability of the investigated aggregates for many geotechnical applications.

Automated summary

This research conducted comprehensive experimental investigation on the geotechnical characterization of new synthetic lightweight aggregates (SLAs) composed of reused biomass fly ash and waste plastics. The SLAs were evaluated for their compressibility, creep properties, compaction features, stress-strain-strength behavior, hydraulic conductivity, and water absorbability. The study found that the fly ash-HDPE aggregate had less compressibility compared to the fly ash-LDPE aggregate, and its creep coefficient was comparable to or even lower than that of other recycled materials. The aggregates also exhibited favorable permeability properties and proved to be environmentally sustainable.