Mechanical and thermal properties of novel lightweight concrete mixtures containing recycled glass and metakaolin

The aim of this study was to investigate the behaviour of a new type of lightweight concrete which would be suitable for use as a load-bearing concrete masonry unit. Different ratios of by-product materials which consist of metakaolin (MK) and recycled glass were used in conjunction with expanded clay to produce the lightweight concrete mixtures. The short and long-term mechanical properties and thermal criteria were measured using a total of 208 specimens with different geometries. Some statistical analysis was conducted and the obtained results were compared with the standard expressions.The tests results showed that it is possible to produce a structural lightweight concrete possessing good thermal properties using by-product materials. Compressive and splitting tensile strengths, as well as the modulus of elasticity, increased with an increase in the metakaolin content, whilst a counteractive behaviour was recorded for the density. Clear improvements in thermal conductivity and insulation criteria were observed in comparison with conventional lightweight concrete mixtures. The measured thermal conductivity values ranged from 0.092 W/m K to 0.177 W/m K, and the insulation criterion reached up to 110.25 min for 29 mm concrete member thickness.

► A structural lightweight concrete was produced using by-products materials.
► Inclusion MK improved the mechanical strength of the concrete mixes.
► The ratio of MK to recycled glass influences the overall strength development.
► Superior thermal behaviour was achieved at ambient and elevated temperatures.