Properties of Geopolymers Made from Fired Clay Bricks Wastes and Rice Husk Ash (RHA)-Sodium Hydroxide (NaOH) Activator

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.

Mechanical and microstructural properties of geopolymer mortars from meta-halloysite: effect of titanium dioxide TiO2 (anatase and rutile) content

“…The less intense peak of Ti-O-Ti bond is overlapped in the broad bands around 692-667 cm −1 and 688-665 cm −1 by the band ascribed to the Si-O stretching and deformation vibration for GMHA and GMHR series respectively. For the reference (GMH), the broad absorption bands at 3404 cm −1 and 1655 cm −1 are respectively attributed to vibration bending and stretching mode of the hydroxyl O-H bonds belonging to water molecules present on absorbed surface or entrapped in the 3D polymeric structure cavities during the geopolymerization process [35]. These bands are located in the range 3385-3355 cm −1 and 1649-1625 cm −1 for GMHA series (Fig.…”

A Review of Recent Advances in Alkali-activated Materials from Silica-rich Wastes Derived Sodium Silicate Activators

“…Generally, the release of SiO 2 increases with the increase of alkali concentration. When the alkali concentration was increased from 1 M to 10 M, the yield of silicate was increased (Kamseu et al 2017;Luukkonen et al 2018). This may be due to the increase in the pH of the liquid under high alkaline conditions, further enhancing the release rate of SiO 2 (Andreola et al 2020).…”

“…3.1.1 FTIR spectra FTIR results show that the derivative SS has essentially similar characteristic peaks to commercial SS. In the ATR (attenuated total reflection) method, the Si-O-Si bond asymmetric stretching vibrations of SS solutions are between 850 and 1 200 cm -1 regions (Gaggiano et al 2013;Halasz et al 2007;Moungam et al 2017;Nordström et al 2011). As can be seen in Fig.…”

“…An obvious shoulder peak near 1100 cm -1 was observed in both commercial SS and RHA2 SS. It belongs to Q 3 and Q 4 units, namely condensed silicate (Bass et al 1997;Moungam et al 2017), which are 2D/3D products of the condensation of silicate monomer SiO 4 4-. When the modulus is 2.0, the content of condensed silicate in commercial SS is higher than that of RHA1 SS, indicating a higher silica content of the commercial SS.…”

“…Commercially available Na 2 SiO 3 is produced after a range of energy-intensive processes, which result in high CO 2 emissions (Kamseu et al 2017;Mellado et al 2014). Specifically, the production of commercially available Na 2 SiO 3 requires the melting of sodium carbonate (Na 2 CO 3 ) and silica sand (SiO 2 ) into the kiln at a high temperature of 1400 to 1500°C.…”