Effects of Fly Ash Geopolymer Leachate Alkalinity on Lethality of Freshwater Climbing Perch, Anabas testudineus

The application of geopolymer materials from industrial waste as binder to cast concrete contributes to a reduction of CO2 than OPC but still contribute to other environmental adverse effect such as freshwater toxicity. The leaching of alkali from geopolymer building materials increases the alkalinity or pH values of affected water body and can cause damage the biotic ecosystem and aquatic organisms. Therefore, the increasing level of alkalinity which is pH values from the leaching of geopolymer materials and OPC caused the lethality of Anabas testudineus (climbing perch) were determined. A 50mm x 50mm x 50mm dimensional fly ash geopolymer paste with 12M NaOH solution (Na2SiO3 : NaOH = 2.5:1) and a 50mm x 50mm x 50mm dimensional OPC with the ratio of (Solid : Liquid = 3 : 1) were immersed accordingly into each cylindrical containers that contained an Anabas testudineus (climbing perch) in 500ml paddy swamp water. The fishes were observed and the pH readings were calculated. The test was ended until the fish dead. Finally, the mortality limit pH value of Anabas testudineus for fly ash geopolymer paste is at pH 11.0, while OPC is at pH 11.5. The peak of alkali leaching of fly ash geoplymer paste is between 0.5 – 1.0 hours while for OPC is between 0.25 – 0.5 hours. As the conclusion, OPC gives severe adverse effects to the mortality of Anabas testudineus than fly ash geopolymer paste due to the leaching of OH- and other alkali anions. Anabas testudineus can live 10 hours in fly ash leaching media but only can live 1 hour in OPC leaching media.