Geopolymer Composites with Recycled Binders

Abstract

The application of geopolymers as an alternative to cement concretes is becoming increasingly important. The significant advantage of this composites is that, the basic ingredient is not a cement, but pozzolans such as waste materials—fly ash, fly ash slag mix, red ceramic fines, recycling cement mortar—which makes building materials more environmentally friendly. Currently the availability of blast furnace slag and high-quality fly ash is limited in Europe. At the same time, the ways for management of the concrete rubble and the construction waste are being sought, because the volume of waste materials is constantly increasing. Therefore, the application of secondary binders extracted from the recycling of various construction waste (recycled cement mortar, red ceramic fines, fly ash-slag mix) in geopolymers was proposed. The recycled binders were introduced into geopolymer composites as a replacement of 25% by mass of primary binder (fly ash) and the 65, 75 and 85ºC was the curing temperature. The process of manufacturing the recycled binders has been described and basic parameters of new binders. The tests of physical and mechanical properties of the composites such as compressive strength, flexural strength, volume density in dry state and saturated one and water absorption were performed. The microstructure of geopolymers was examined using scanning electron microscopy (SEM). The results obtained show that recycled binders obtained from the treatment of construction waste could be a valuable component of geopolymers. © The Author(s) 2025.