Effect of addition of As-received IGCC slag in making geopolymer

Abstract

It is a known fact that the cement production is responsible for almost 5% of total worldwide CO2 emission, the primary factoraffecting global warming. Geopolymers are valuable as ordinary Portland cement (OPC) substitutes because geopolymersrelease 80% less CO2 than OPC and have mechanical properties sufficiently similar to those of OPC. Therefore, geopolymershave proven attractive to eco-friendly construction industries. Geopolymers can be fabricated from aluminum silicatematerials with alkali activators such as fly ash, blast furnace slag, and so on. Integrated gasification combined cycle (IGCC)slag has been used for fabricating geopolymers. In general, IGCC slag geopolymers are fabricated with finely ground andsieved (<128 mesh) IGCC slag. The grinding process of as-received IGCC slag is one of the main costs in geopolymerproduction. Therefore, the idea of using as-received IGCC slag (before grinding the IGCC slag) as aggregates in thegeopolymer matrix was introduced to reduce production cost as well as to enhance compressive strength. As-received IGCCslag (0, 10, 20, 30, 40 wt%) was added in the geopolymer mixing process and the mixtures were compared. The compressivestrength of geopolymers with an addition of 10 wt% as-received IGCC slag increased by 19.84% compared to that with noadditional as-received IGCC slag and reached up to 41.20MPa. The enhancement of compressive strength is caused by asreceivedIGCC slag acting as aggregates in the geopolymer matrix like aggregates in concrete. The density of geopolymersslightly increased to 2.1-2.2 g/cm3 with increasing slag addition. Therefore, it is concluded that a small addition of as-receivedIGCC slag into the geopolymer can increase compressive strength and decrease the total cost of the product. Moreover, thedirect use of as-received IGCC slag may contribute to environment protection by reducing process time and CO2 emission.