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Increasing the reactivity of modified ferro silicate slag by chemical adaptation of the production process

Book Contribution - Book Chapter Conference Contribution

Modified Ferro Silicate (MFS) slag can be used as an alternative Supplementary Cementitious Material (SCM)to make concrete sustainable and to enhance the circular economy. Given their pozzolanic characteristics,these MFS slags can be used as SCM. However, due to the low CaO content of the MFS slag, they haveslower reaction and dissolution rate than Ca rich by-products such as Ground Granulated Blast Furnaceslags (GGBFS). Increasing latent hydraulic properties of the slag could potentially also increase the overallreactivity of the slag. In this respect, the objective was set to increase the CaO content of the MFS slag,by addition of CaCO3 during its fuming process. In order to investigate the feasibility, at first, lab scaletests were performed and reported in this paper. Currently available MFS slag was remelted and chemicallyadapted at 1220 ±10 °C. Two mixes were synthesized in which respectively 10 and 20 wt.% of CaC03 wasadded to the MFS slag. After melting the slag in a reducing atmosphere, it was water quenched in order toobtain an altered slag with a high glassy phase comparable to die current MFS slag. Chemical compositionand mineralogy of CaCO3 altered MFS slag was determined and its reactivity was assessed by the novel R³reactivity assessment technique proposed by RILEM TC 267-TRM. Finally, altered MFS slag was comparedwith the unaltered MFS slag to study the influence of CaO content on the slag reactivity and dissolution. R³Calorimetric analysis and CH consumption showed an enhanced dissolution rate for altered slag suggestingthat incorporation of CaO in the system tends to improve the reactivity. Moreover, XRD and in-situ XRDanalysis of the R³ hydrated paste provided sufficiënt information that increasing the Ca content in the glassyphase tends to improve the dissolution of Fe which contributes to formation of Fe-AFt and stable Fe-Mcafter 24 h.
Book: Proceedings ICSBM 2019 Volume 4 - Waste recovery, treatments and valorization
Pages: 36 - 46
Publication year:2019