Abstract
Ferrochrome (FeCr) slag was used as a precursor for the synthesis of a geopolymer. The effect of KOH concentration, liquid solid ratio (L/S), content of potassium metalisicate (KS) or potassium aluminate (KA), curing time on the unconfined compressive strength (UCS) and metal leachability of the synthesised geopolymer was investigated. A 10 M KOH and an L/S of 0.26 yielded a geopolymer with a UCS 13.0 MPa after 28 d of ambient temperature curing. A 0.125 wt KS:KOH addition yielded a geopolymer with a UCS of 14.7 MPa whilst a 1.25 wt KA:KOH addition yielded a geopolymer with a UCS of 24.5 MPa. The increase in strength was due to the formation of Calcium Silicate (Aluminate) hydrate. The aluminate activated FeCr slag geopolymer was the most competent of all geopolymers synthesised as it resulted in over 97% immobilisation of Fe, Zn, Mn, Ni and Cr. The 360-d static leachability tests for the aluminate activated geopolymer yielded a metal release rate lower than 90 mg mm− 2 of the geopolymer. The aluminate activated geopolymer also was resistant to changes in wet and dry cycles as it had a UCS reduction of 42% after 10 cycles whereas the pure FeCr slag geopolymer and the silicate activated geopolymer had a UCS reduction of 91 and 72% respectively after 10 cycles. The aluminate activated geopolymer met the minimum requirements for use as a paving brick for low traffic pavements. The study provides opportunities for sustainable use of FeCr slag with minimal environmental impact.
Highlights
Ferrochrome (FeCr) slag is a waste product from the carbothermic reduction of FeCr ore resulting in the production of high or low carbon FeCr alloy
Effect of KOH concentration and liquid solid ratio (L/S) ratio on the unconfined compressive strength (UCS) of the geopolymer At a fixed concentration of KOH, there was an increase in the UCS of the obtained geopolymers with an increase in L/S up to 0.26 (Table 2)
The decrease in UCS with an L/S greater than 0.26 may be due to excess liquid which would not be utilized during geopolymerisation and would be lost during curing period leaving voids in the monolith thereby creating a weak structure
Summary
Ferrochrome (FeCr) slag is a waste product from the carbothermic reduction of FeCr ore resulting in the production of high or low carbon FeCr alloy. It is estimated that the global annual production of FeCr alloy is between 12 and 16 Mt [1]. It is estimated that the FeCr slag to alloy production is 1.1–1.5:1 [2]. FeCr slag is a well-known pollutant containing elevated levels of toxic elements [3, 4]. FeCr slag has been classified as a nonhazardous waste in Finland [6] yet in South Africa it is classified as a hazardous waste [7]. The classification as non-hazardous of FeCr slag, may likely lead to its increased use in the construction industry, thereby leading to a reduction of volumes accumulating in landfills and fulfilling the demands of sustainable development through the use of secondary resources in the construction industry
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
