Abstract
High cost has been pointed among factors that limit the promotion of geopolymers. To contribute to the reduction of the use of costly industrial sodium silicate in activators for geopolymers, a gel obtained with RHA and concentrated sodium hydroxide was used in the present study to develop an alkaline activator with 8 M NaOH and to produce geopolymers with crushed fired clay bricks wastes (FCBW). Characteristics of the gel were compared to that of commercial sodium silicate which was also mixed with 8 M NaOH in the ratio 1:1 to produce geopolymers. Chemical and mineralogical analyses were done on raw materials. Fourier Transformed Infrared Spectroscopy (FTIR) was done on the gel, commercial sodium silicate and products. Biaxial four point flexural strength, bulk density, water absorption and scanning electron microscopy (SEM) tests were also done on products. Results showed that RHA-NaOH alkaline activator has good potential in consolidating FCBW powder through geopolymerization process which gave products that had characteristics not far from that when the commercial sodium silicate was used. The gel obtained by mixing RHA and NaOH can contribute to the reduction of the use of costly commercial sodium silicate in the production process of geopolymers. However, appropriate filtration process is needed for the RHA-NaOH gel to reduce its impurities as undissolved entities, which will consequently contribute to improve the flexural strength, the density and the microstructure of its products which were low compared to when commercial sodium silicate was used.
Highlights
Concrete is the most used material worldwide in construction because of its multiple technical advantages [1]
The aim of this study is to investigate the properties of geopolymer products obtained by the alkali-activation of fired clay bricks wastes (FCBW) powder with an alkaline solution obtained by mixing RHA, sodium hydroxide and water
The OH vibration band is observed at 3300 cm−1 for commercial sodium silicate whereas that from RHA-NaOH gel appeared at 3200 cm−1
Summary
Concrete is the most used material worldwide in construction because of its multiple technical advantages [1]. For environmental concerns, by-products, containing alumina and silica were increasingly used They can be volcanic ash [9] and ceramic wastes [10]. The conventionally used alkaline activator is a mixture of sodium (NaOH) or potassium (KOH) hydroxide with sodium (Na2SiO3) or potassium (K2SiO3) silicate [11] The constituents of these alkaline solutions are manufactured products. For geopolymers to be a viable alternative and industrially interesting, many technological issues must be overcome, especially research on low cost activators. In this direction, Zivica developed alkaline activators based on silica fume [14]. RHA has been widely used in many construction and civil engineering applications [18] [19] [20]
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