Reactivity of modified iron silicate slag as sustainable alternative binder

Abstract

A possible solution to decrease the CO2 footprint caused by the cement industry and to enhance the transition to circular economy is to use slags as Supplementary Cementitious Materials (SCM). The study presented here focuses on valorizing and investigating the reactivity and mechanical properties of blended binder systems combining Modified Iron Silicate (MFS) slag and Ordinary Portland Cement (OPC). MFS slag is a fumed by-product synthesized during the production of Copper (Cu) metal. This slag can be used as possible alternative SCM due to its pozzolanic behaviour. To study the replacement level in relation to reactivity and strength development, replacement levels of 15, 30 and 50 wt% of MFS-slag in ordinary portland cement are analyzed. The work can be divided into two categories: 1) assessing the reactivity through thermogravimetric analysis (TGA) and 2) evaluating the compressive strength (as a function of time) of mortar with MFS-slag after 2, 7, 28 and 90 days. TGA at 7, 15, 28 and 90 days allows to determine the reduction of portlandite content which gives an indication on the pozzolanic reactivity. Reactivity of MFS-slag blended systems is also determined relative to inert filler blended systems to discern between the reactive behavior of the MFS-slag and the filler effect.

A Method for Synthesizing Iron Silicate Slags to Evaluate Their Performance as Supplementary Cementitious Materials

“…FeO The studies have concluded that iron silicate copper slags exhibit pozzolanic properties [12,[14][15][16]21]. However, the inherent reactivity is lower than, e.g., ground granulated blast furnace slag [21,22], which is reflected when reviewing data on mortars and cement composites.…”

“…The results showed that the incorporation of the slag improved the compressive strength of mortars after curing beyond seven days [10]. Since 1997, several studies have been published explicitly addressing iron silicate copper slags for SCM applications [6,[11][12][13][14][15][16][17][18][19][20]. Furthermore, an additional study has incorporated the slag in a comparison of different SCMs [21].…”

“…The slag compositions included in these studies are presented in Table 1. The primary methodologies employed for these slags include mortar testing [6,[11][12][13][14]16,18,21], cement composite testing [17,19,20], isothermal calorimetry on Portland cement blends [12,14,19,20], isothermal calorimetry using the R 3 test [21], as well as the Chapelle and Frattini tests [14].…”

Feasibility Study on the Use of Modified Copper Slag as a Sustainable Fine Aggregate in Mortar

“…At 28 and 90 days, the MFS slag mortar showed higher compressive strength (70 MPa at 28 days and 78 MPa at 90 days) relative to the standard aggregate mortar (66 MPa at 28 days and 75 MPa at 90 days). It can also be proposed that finer particles of the MFS slag potentially reacted and formed binders due to pozzolanic reaction at later ages [9].…”

“…For instance, when Cu slag is used as a substitute for cement in concrete, the Sirich glass structure reacts with the porous alkaline solution (enriched in CH) as a result of the pozzolanic reaction. In the work of Sivakumar et al, the pozzolanic reactivity of one particular type of clean Cu slag as SCM was assessed using TGA analysis by replacing 0%, 15%, 30%, and 50% of CEM I in a paste [9]. The conclusions were that the CH was consumed through the pozzolanic reaction.…”