Use of Treated Non-Ferrous Metallurgical Slags as Supplementary Cementitious Materials in Cementitious Mixtures

Asghar Gholizadeh Vayghan,Liesbeth Horckmans,Ruben Snellings,Bernd Friedrich,Katarzyna Klejnowska,Jürgen Maier,Priscilla Teck,Arne Peys

doi:10.3390/app11094028

Abstract

This research investigated the possibility of using metallurgical slags from the copper and lead industries as partial replacement for cement. The studied slags were fayalitic, having a mainly ferro-silicate composition with minor contents of Al2O3 and CaO. The slags were treated at 1200–1300 °C (to reduce the heavy metal content) and then granulated in water to promote the formation of reactive phases. A full hydration study was carried out to assess the kinetics of reactions, the phases formed during hydration, the reactivity of the slags and their strength activity as supplementary cementitious material (SCM). The batch-leaching behaviour of cementitious mixtures incorporating treated slags was also investigated. The results showed that all three slags have satisfactory leaching behaviour and similar performance in terms of reactivity and contribution to the strength development. All slags were found to have mediocre reactivity and contribution to strength, especially at early ages. Nonetheless, they passed the minimum mechanical performance requirements and were found to qualify for use in cement.

Highlights

Portland cement continues to have the highest share of CO2 emission among all construction materials [1] and is responsible for 5–8% of the total anthropogenic CO2 emission across the planet [2]
The application of a secondary thermal treatment to non-ferrous slags from the lead and copper industries can significantly reduce the amounts of heavy metals in the slags and enable their use in cementitious materials
Despite the differences in the source and compositions of the slags, while granulation results in a substantial increase in their amorphous content, they are only moderately reactive according to R3 and calorimetry findings

Summary

Introduction

Portland cement continues to have the highest share of CO2 emission among all construction materials [1] and is responsible for 5–8% of the total anthropogenic CO2 emission across the planet [2]. Researchers in the past few decades have attempted to reduce the use of clinker in cement-based materials by partially or fully replacing the clinker with supplementary cementitious materials (SCMs) or alternative binders. Some notable SCMs with established environmental and technical benefits when used with Portland cement are silica fume, coal fly ash, and granulated blast furnace slag from iron production. From the environmental point of view, their use in combination with Portland cement eliminates the need for their disposal (which is favourable due to the lack of landfill spaces) and reduces the environmental impact of cement-based materials (by reducing their CO2 footprint and embodied energy). The slags generated during pyrometallurgical processes in the lead or copper production industry are investigated and used in cement and concrete to a much lower extent [7] The incorporation of such SCMs in concrete entails numerous technical benefits such as higher durability against corrosion, sulphate attack and alkali–silica reaction and often improved long-term mechanical properties [3,4,5,6].

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Conclusion