Abstract
This paper is wholly committed to resource efficiency through the valorisation of waste from other industries, and more specifically fly ash as a raw material to produce concrete-like geopolymers. In particular, this study aimed to determine the effect of the physical and chemical characteristics of recycled coal fly ash used to manufacture alkaline cement on reaction kinetics and product microstructure and performance. The ash was mixed with 8 M NaOH and cured for 20 h at 85oC and RH of 90 % to form a compact paste, after which mechanical strength was determined and the reaction rate was calculated using isothermal conduction calorimetry. The findings showed that vitreous content, (SiO2/Al2O3)reactive and (especially) particle size distribution play a very important role in both the development of cement mechanical strength and the composition and structure of the reaction products formed.
Highlights
Portland cement manufacture consumes around 4 GJ of energy per ton and accounts for approximately 8% of worldwide CO2 emissions, or 2.981 GtCO2eq in 2014 (CSI/ECRA—Cement Sustainability Initiative/ European Cement Research., 2017).The Roadmap for a resource-efficient Europe (COM, 2011) 0571 describes industrial strategies to mitigate the effects of industrial activity and ensure that by 2050 Europe will have a sustainable economy, in which “resources are not extracted, used and thrown away, but are put back in the loop so they can stay in use for longer.”Cross-cutting concerns such as the need for more long-term, innovative thinking are being addressed
Like other industrial waste such as blast furnace slag or red mud, fly ash can be activated in alkaline media, setting and hardening to acquire properties similar to Mechanical-Chemical Activation of Coal Fly Ashes those characteristics of portland cement
Mechanical activation has only a minor effect on fly ash reactivity, inasmuch as the amount of potentially reactive SiO2 and Al2O3 depends more on the mineralogical phases in the ash than on fineness
Summary
Portland cement manufacture consumes around 4 GJ of energy per ton and accounts for approximately 8% of worldwide CO2 emissions, or 2.981 GtCO2eq in 2014 (CSI/ECRA—Cement Sustainability Initiative/ European Cement Research., 2017).The Roadmap for a resource-efficient Europe (COM, 2011) 0571 describes industrial strategies to mitigate the effects of industrial activity and ensure that by 2050 Europe will have a sustainable economy, in which “resources are not extracted, used and thrown away, but are put back in the loop so they can stay in use for longer.”Cross-cutting concerns such as the need for more long-term, innovative thinking are being addressed. Like other industrial waste such as blast furnace slag or red mud, fly ash can be activated in alkaline media, setting and hardening to acquire properties similar to Mechanical-Chemical Activation of Coal Fly Ashes those characteristics of portland cement. Such materials, known as “alkali-activated cements” or “geopolymers,” constitute optimal vehicles for valorizing and recycling coal fly ash (Palomo et al, 2014; Zhuang et al, 2016; Bai and Colombo, 2018)
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