Exploration of ecotoxicity tests for environmental assessment of coal fly ash based geopolymers: Experience with the Daphnia magna acute test

Ecotoxicological assessment of construction products is especially relevant for the building and for the demolition phase in their life cycle. Geopolymers are new construction materials based in alumina and silica by an... [ view full abstract ]

Ecotoxicological assessment of construction products is especially relevant for the building and for the demolition phase in their life cycle. Geopolymers are new construction materials based in alumina and silica by an alkali-activation process. In order to know the potential environmental effects derived during the life cycle of these new products on aquatic environment, the acute toxicity test with the crustacean Daphnia magna was conducted. To this end, two products made by mixing illite clay and coal fly ash were selected to be ecotoxicologically characterized. The first product, MP, was made without adding sodium hydroxide and sodium silicate for alkali-activation. The second product, MA, with these reactants to alkali- activation process. Leachates from both products were obtained by mobility leaching test (UNE-EN 12457-4) and used as test samples in Daphnia magna toxicity test. Percentage of mortality response was used as endpoint. After 48 hours, non mortality was recorded when D. magna was exposed to MP sample, while 75% of mortality was observed when individuals were exposed to MA sample. The ecotoxicological assessment using mortality response shows no ecotoxicity for MP (no toxic at the level of EC_50%) and recorded low ecotoxicity levels for MA (EC_50%= 56.68%). In addition, the possible usefulness and disadvantages related to this toxicity test and its applicability in geopolymers as construction product are discussed.