in: Handbook of advances in Alkali-activated Concrete, Fernando Pacheco-Torgal,Prinya Chindaprasirt,Togay Ozbakkaloglu, Editor, Elsevier Science, Oxford/Amsterdam , Oxford, pp.1-10, 2022
The production of alkali-activated concrete, which has
attracted great attention as an alternative to classical Portland cemented
concrete, has become prominent as an environmentally friendly process since
1970s not only because of the utilization of waste materials but also lower greenhouse
gas emissions. In the production of 1 ton cement, approximately 1 ton of CO2
is released into the air and in this respect, cement production takes the 3rd
place on a global scale in terms of both greenhouse gas emission and energy
consumption (Mohseni et al., 2019). In addition to higher strength (Lin et al.,
2020; Mehta et al., 2020), better resistance to fire (Carabba et al., 2019,
Sarıdemir and Çelikten, 2020), noise (Mastali et al., 2018), acids (Gu et al.,
2019) and salts (Aguirre-Guerrero et al., 2021) make alkali-activated concrete
production a more favorite choice. The reactions of solid precursors with
alkali activator solutions form 2 different 3-dimensional binder gel systems
that allow the formation of alkali activated concretes: (1) C-A-S-H rich in Ca
and Si and (2) N-A-S-H rich in Al and Si. Aluminasilicate and calcium
aluminasilicate precursors are mainly industrial by-products such as ground
granulated blast furnace slags (GGBFS) and fly ashes (FA). Metakaolin (MK) is
also a widely used precursor. Alkali-activated concretes, which can be obtained
in low density and lighter weight depending on the source material, turn into a
more promising building material in lightweight concrete production by using
lightweight aggregates.