Effect of Concrete Waste on Compressive Strength and Microstructure Development of Ceramic Geopolymer Pastes

Ceramic industry generates a large amount of wastes, which pollutes and damages the environment. This paper presents the effects of concrete waste incorporating dolomite aggregate on ceramic-based geopolymer pastes in terms of microstructure and compressive strength. Recently, attention has been drawn to the use of geopolymer technology in the production of building units. Geopolymers were prepared from alkali activation of ceramic waste by 6%, 8%, 10% and 12% NaOH. To enhance the mechanical properties, alkali-activated ceramic geopolymer with 10% and 12% NaOH was partially substituted with concrete waste containing dolomite coarse aggregate at proportions of 5%, 10%, 15%, 20% and 30% by weight. Likewise, other geopolymer mixtures were manufactured by replacing ceramics with 5%, 10%, 15%, 20% and 30% calcined concrete waste at 850oC. Water/binder ratio as well as compressive strength of all mixtures was determined at 1, 7, 14 and 28 days. Phase composition and microstructure of geopolymer were identified using Fourier transform infrared spectroscopy and scanning electron microscopy techniques. Incorporation of 10% concrete waste and 20% calcined concrete waste enhanced the compressive strength and the microstructure of ceramic geopolymer pastes, while embedding extra amounts led to adverse effects.