Metakaolin - waste glass geopolymers. The influence of hardening conditions on mechanical performances

The development of new ecological materials for the construction field represents a sustainable solution for waste management as long as their properties are comparable with those of traditional materials in terms of strengths, durability, corrosion resistance etc. Considering the large amount of glass wastes that are generated (e.g. technical waste glass derived from industrial activities) a sustainable approach is to recycle them in new products. To this purpose, metakaolin-waste glass geopolymers were obtained by using 10% technical glass powder and 90% metakaolin, activated with alkaline solutions of NaOH 8M and 12M. After 24 hours of hardening in certain conditions (cured for 2 hours at 60°C respectively 90 °C in covered moulds and up to 24 hours at room temperature) the geopolymer specimens were subjected to thermal treatments at temperatures up to 700°C, in order to establish the influence of hardening conditions on mechanical performances. The transformations which occur in the geopolymer matrix during the hardening process were studied by SEM analyses and x-ray diffraction. The results showed that a higher treatment temperature improves the mechanical resistance.