Abstract
Cement replacement by supplementary cementitious materials has been gaining momentum as a sustainable mechanism to reduce greenhouse gas emissions while also recycling industrial by-products. This paper presents the development and microstructure characterization of fly ash-based lightweight geopolymer concrete incorporating ground granulated blast furnace slag (GGBS). Concrete samples were prepared with 0%, 25% and 50% GGBS replacement and cured at 30°C, 60°C, and ambient temperature. While dune sand and lightweight expanded clay were used as aggregates, a mixture of sodium silicate and sodium hydroxide served as the alkaline activation solution. Microstructure evaluation was carried out at 7 and 28 days employing scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). Residual fly ash and GGBS were identified in the concrete and bonded to geopolymeric reaction products. The microstructure highlighted the formation and coexistence of aluminosilicate hydrate and aluminum-rich calcium silicate hydrate with traces of sodium. Subsequent polymerization was also verified by an increase in FTIR and DSC peaks.
Highlights
The global production of concrete is approximately one cubic meter per capita, making it one of the largely produced materials on earth [1]
Aluminosilicate glass represented in unreacted fly ash spheres are heavily dispersed throughout the microstructure of concretes regardless of curing temperature
Upon the replacement of 25% fly ash with ground granulated blast furnace slag (GGBS), concrete micrographs of Fig. 3 showed agglomerated angular slag particles with some fly ash spheres attached to the reaction products
Summary
The global production of concrete is approximately one cubic meter per capita, making it one of the largely produced materials on earth [1]. It is a composite material mainly comprising cement and coarse and fine aggregates. The cement industry alone is accountable for 5-7% of the global CO2 emissions [4, 5], leading to an increase in the concentration of CO2 in the atmosphere [6, 7]. Cement production is becoming an increasing global pressing issue from an ecological, social, and environmental standpoint
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