Influence of aggressive environmental impacts on clean, lightweight bricks made from cement kiln dust and grated polystyrene

Cementitious bricks of low density were produced from a novel composite material consisting of four different surplus products: iron slag, cement kiln dust, ground waste glass and spent polystyrene in combination with Portland cement. The new composite material was thoroughly characterized by mechanical testing, and its durability when exposed to heavy weathering conditions (water penetration and frosting) was examined. The suitability of the new composites as construction materials was validated by physical and mechanical characterizations. Composite specimens containing 5% iron slag, 10% Portland cement, 10% ground waste glass and 3% spent polystyrene in a cement kiln dust matrix were exposed for long periods to repeated freezing/ thawing cycles, and to immersion in water of different origin for up to three months. Compressive strength, water absorption, porosity and density of the specimens were studied after exposure to these challenging conditions, while microstructural changes after exposure were examined via scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and spectroscopic analysis (FT-IR and XRD). As major outcome, compressive strength and indirect tensile strength of tested specimens increased during 30 days of freezing/thawing to 3.63 MPa and 2.13 kPa, respectively, and to 3.31 MPa and 1.94 kPa, respectively, during 60 days of immersion in aqueous medium mimicking acidic rain. This indicates that the new composite material, which can be produced at lower cost compared to current construction materials, not only revealed high resistance against the harsh environmental conditions exposed to, but even improved mechanical properties in comparison to data measured prior to exposure.