The Effect of Pulp Industrial Waste as Chemical Admixture to Compressive Strength of Fly Ash Based Alkali Activated Materials

Black liquor is a toxic by-product from industrial pulp manufacture. It contains sodium hydroxide that can be used as precursor activator for alkali activated material, which is an aluminosilicate material that can be prepared from thermal activation of solid material containing alumina and silica as precursor and alkali activator solution. In this work, alkali activated mortar was prepared by mixing fly ash as main precursors, aggregate, followed by addition of activator solution containing sodium hydroxide solution and waterglass, and chemical admixture which is lignin or black liquor. The best compressive strength was 34.40 MPa achieved in addition of 10 wt% of black liquor to alkali activated mortar. X-ray diffraction demonstrated the formation of albite in mortars, indicating that geopolymerization have been successfully formed. FTIR spectra showed the presence of siloxo and sialate peaks which commonly found in geopolymerization