Geopolymer synthetized from bottom coal ash and calcined paper sludge

This study deals with the development of geopolymers synthetized from industrial waste containing aluminosilicates. Geopolymers are inorganic polymers formed by the activation of amorphous aluminosilicates (Al2O3.SiO2), which react in a strongly alkaline medium. Bottom ash (SiO2/Al2O3 = 3.3–4.5) was used as source of aluminosilicate and sodium hydroxide (NaOH = 5, 10 and 15 M) and sodium silicate (Na2SiO3, SiO2/Na2O = 1.58) were used as alkaline medium. Calcined paper sludge was used to increase the reactivity of the partially crystallized bottom ash. The solid waste was characterized by XRF and XRD and the geopolymer samples were characterized by XRF, XRD, SEM, FTIR and compressive strength tests. The best results were obtained with a solution of 15 M NaOH and sodium silicate and a mixture of 2:1 bottom ash and calcined paper sludge.