Table of ContentsIntroduction
The geopolymerization technology is evolving gradually in the ground stabilization, construction and waste management industries. The key application of geopolymer technology is in the development of reduced CO2 construction materials as an alternative to Portland-based cements.
Geopolymerization can also be used as a processing technique in the field of ceramics, offering the potential to set or harden without deploying high firing or sintering temperatures.
This is of increased interest to ceramics manufacturers, bringing down firing temperatures, which reduces associated costs and energy usage which has a positive impact on profitability. Firing energy accounts for a significant percentage of ceramic production costs hence several sub-sectors have expressed interest in this technique including the tile and building material producers.
Being committed to energy reduction improves brand reputation and offers consumers confidence in the strategy of business sustainability. Along with saving energy, geopolymerization can enable low-cost secondary grade or waste mineral phases, using waste also enhances profitability.
Figure 1. Geopolymerisation ingredients
Conventionally ceramic production involves shaping with mixed powders, next firing in kilns with peak temperatures in the range of1,000-1,250°C. Solid state reactions or glass phases at this temperature rise to form bonds between the inorganic powder particles. In geopolymerisation, similar M-O-M bonds (e.g. Si-O-Si or Si-O-Al) are formed between particles by inducing lower temperature (40-180°C) chemical reactions. In order to ensure successful geopolymerization, it is important to identify the silicate source that the caustic chemicals driving the chemistry can dissolve readily.
Figure 2. A red tile (10 x 10cm) produced with metakaolin, a black tile (10 x 10cm) obtained with fly ash as received from the power station and a red/black tile (10 x 10cm) showing the excellent bonding between the metakaolin and fly ask layers
Even though geopolymerization cannot match the mechanical characteristics of traditional ceramics delivered by firing, it offers a viable option for applications where the need for abrasion resistance, strength and chemical durability is less demanding. For instance, if compressive strength is lacking, bricks may not be a suitable application, whereas roofing tiles which experience negligible load-bearing may be.
The white paper ‘Geopolymerisation: A Sustainable Processing Method for Ceramics and Bricks’ reviews specific technologies used in developing geopolymer systems and studies how, specifically, rheology and material characterisation can enhance the final mechanical properties. Additionally, the paper also discusses how novel shaping routes can play a major role in making geopolymerisation a commercial reality.
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