Effect of copper and stainless steel slags on fresh, mechanical and pore structure properties of alkali activated ground granulated blast furnace slag

Abstract

Reusing and recycling waste materials in the construction industry can provide a significant contribution in terms of environmental and economical aspects. This article reports a material case study on the combined use of three industrial by-products (metallurgical slags), namely copper slag (CS), stainless steel slag (SS) and ground granulated blast furnace slag (GGBFS) as solid precursors to produce binary blend alkali activated materials (AAMs). A total of seven binary AAMs mixtures with different ratios (0%, 25%, 50%, and 75%) of CS and SS as partial replacement of GGBFS were activated by a combination of sodium hydroxide and sodium silicate as an alkali solution. The behaviour of the mixtures is reported in terms of flow spread and flow curve, compressive and flexural tensile strengths, mercury intrusion porosimetry (MIP) and water absorption by submerging. The flow spread and dynamic yield stress of the mixtures increased and decreased by partially replacing GGBFS with CS or SS, respectively, leading to better workability properties of the fresh mixture. The use of CS or SS up to 50% reduced the compressive and flexural tensile strengths of the specimens between 30‐42% and 14‐46%, respectively. Despite this drop in strength, the 28 days compressive strength of the studied mixtures was always higher than 50 MPa. The capillary porosity of the specimens increased with higher contents of CS or SS. Water absorption results of the specimens appeared highly influenced by the applied drying temperature in the test method. Overall, partial replacement of GGBFS by CS or SS, targeting binary precursor systems, is promising for replacement levels up to 50%.