Suitability of Incinerated Sewage Sludge Ash to Produce Geopolymer Concrete R.C.M. Paulnath 1 , A.M.M.Aski 1 , F.Hamsath 1 , S.Jasekan 1 and C.K.Pathirana 1 1 Department of Civil Engineering Faculty of Engineering University of Peradeniya Peradeniya SRI LANKA E-mail: chin@civil.pdn.ac.lk Abstract: Geopolymer concrete (GPC) has been developed as an alternative material to conventional Portland cement concrete. This was developed to reduce the emission of carbon dioxide. So far, materials such as fly ash, blast furnace slag and metakaolin have been used as geopolymer solids to produce the GPC. Aim of this research is to study the suitability of Incinerated Sewage Sludge Ash (ISSA) to be used as geopolymer solid. Mix design for GPC was carried out using the G-graphs which were developed for fly ash based-geopolymer concrete. Initially GPC test cubes were cast using fly ash and ISSA alone. Thereafter fly ash was replaced by ISSA in certain percentages (5, 10, 15 and 20) to make geopolymer concrete. XRF and heavy metal analysis tests were carried out for raw Sewage Sludge (SS) as well as ISSA. Compressive strength of GPC was also observed in acidic environment. XRF test revealed that SiO 2 and Al 2 O 3 are mostly present in all samples tested. Heavy metal analysis for Hanthana sample showed that Zn is the most prominent heavy metal exists in both SS sample as well as ISSA sample. The compressive strength developed was not significant when using ISSA alone to make GPC. When fly ash was partially replaced by ISSA, the strength of GPC showed decreasing pattern as the ISSA percentage was increased. Similar strength results were observed in acidic environment too. According to the Concrete Society Board recommendations, all GPC specimens with different fly ash replacements, can be considered as average in absorption rating as well as concrete quality. Therefore ISSA could be used as a partial replacement for fly ash, for specific applications which would require less strength characteristics. Keywords: geopolymer concrete, incinerated sewage sludge ash, fly ash 1. Introduction GPC is OPC free concrete. It is made by binding aggregates with geopolymer binder. Geopolymer binder is made by mixing source material and alkaline solution. Alkaline solution triggers the geopolymerisation (Davidovits, 1994). So far, slag based-geopolymer concrete and fly ash based- geopolymer concrete have been developed and used in the construction industry. Increase in sewage sludge causes too many environmental problems. The presence of harmful heavy metals in Incinerated sewage sludge ash (ISSA) causes disposal problems. By trapping these heavy metals in the chain of polymers it may achieve the immobilization. This research study mainly focuses on the application of ISSA in GPC. 1.1. Geopolymers The two main constituents of geopolymers are source materials and alkaline liquids. The source materials for geopolymers based on alumina–silicate should be rich in silicon (Si) and aluminum (Al). These could be natural minerals such as kaolinite and clays. Alternatively, by-product materials such as fly ash, silica fume, slag, rice-husk ash and red mud could be used as source materials. The alkaline liquids are obtained from soluble alkali metals that are usually sodium or potassium based.