Thermal and mechanical properties of lightweight concretes based on waste aggregates

Abstract

The aim of this study is to identify a construction material ensuring good mechanical properties and thermal insulation. The study also aimed at assessing the suitability of lightweight aggregates of waste origin such as lytag, boiler slag and omega spheres. On the basis of these components, using chemical admixtures, we tried to produce concrete with the lowest possible W/C ratios, but accordingly characterised by high compressive strength, low density and thermal conductivity parameters. The paper presents 8 mix formulas of lightweight concrete based on waste aggregates. An interesting aspect of the work was to compare different concrete formulas to determine the most advantageous parameters for future use. Substantial changes in formulas consisted in replacing lytag with boiler slag and introducing such components as omega spheres, micro-silica and fly ash. The use of waste aggregates (lytag, boiler slag) improved concrete characteristics. All presented formulas ensured high compressive strength and good thermal insulation performance. Significant porosity of the aggregates allowed for maintaining low density (1332-1749 kg/m³) and very good thermal properties of the material (0.388- 0.6 W/mK). After 28 days the compressive strength testing of the samples, depending on the composition of concrete mix, provided significant results as for lightweight concrete parameters reaching even 65 MPa.