The effect of adding metakaolinite and porcelenite on geopolymers produced from untreated kaolinite

A geopolymerization process was developed by activating local raw kaolinite with quartz and tuff fillers and alkaline sodium hydroxide solution. The geopolymers were cured at 80 °C for 24 hr. The increase of silica sand has improved the workability of the mixture. The addition of metakaolinite and porcelanite (opal-ct) has removed excessive salts and has also increased the compressive strength (higher than 50 MPa for dry conditions). The results have confirmed that natural kaolinite satisfy the criteria to be used as a precursor for the production of high quality inexpensive, stable materials. The produced geopolymers proved to be highly durable under different physical and chemical conditions. The high strength, heat resistance, low production cost, low energy consumption, and low CO2 emissions suit the use of the geopolymers as a substitute of Portland cement and ceramics.