INTERNATIONAL JOURNAL OF CIVIL AND STRUCTURAL ENGINEERING Volume 3, No 1, 2012 © Copyright by the authors - Licensee IPA- Under Creative Commons license 3.0 Research article ISSN 0976 – 4399 Received on June, 2012 Published on August 2012 168 Effect of synthesizing parameters on workability and compressive strength of Fly ash based Geopolymer mortar Anupam Bhowmick 1 , Somnath Ghosh 2 1- Post Graduate Student, Civil Engg. Deptt. Jadavpur University, Kolkata, India 2- Professor, Civil Engg. Deptt. Jadavpur University, Kolkata, India anupam.bhowmick@rediffmail.com doi:10.6088/ijcser.201203013016 ABSTRACT Geopolymer is known for its durability and environmental sustainability. The findings of this research paper are based on the experiments conducted on geopolymer mortar synthesized from locally available fly ash. Various engineering properties are highlighted. Influence of processing parameters such as Fly ash/ Sand ratio, SiO 2 /Na 2 O ratio, and Water/ Fly ash ratio on workability and compressive strength are studied which may be useful to develop mix design methodology. Pore size distribution and total pores volume are appreciated by Mercury Intrusion Porosimetry (MIP) and their influence on compressive strength. Scanning electron microscopy (SEM) along with Energy dispersive X-ray spectroscopy (EDX) was done for micro-structural and elemental analysis. Keywords: Geopolymer, fly ash, workability, compressive strength, microstructure. 1. Introduction Sustainable practice of industrial ecology demands the use of byproduct of one industry as source materials to other industrial application. This will help in complying environmental parameters for both the industry. Environmental concerns compelled us to reduce the material consumption by enhancing the durability and resource efficiency using advancement in technology. (Mehta P.K. 1990). Fly ash based geopolymer may be a solution in this regard. Fly ash is a residue from combustion of coal, improper retention of which cause environmental concern. Fly ash is activated with alkaline solutions and soluble silicates. Sodium / Potassium hydroxide are generally used as alkaline solution successfully supplemented by Sodium / Potassium Silicate. A lot of research was carried out on the geopolymer paste to understand the basics of geopolymer chemistry. Parameters such as Si/Al ratio, SiO 2 /Al 2 O 3 , Na 2 O/ Al 2 O 3 , Na 2 O/ SiO 2 in the activator solution, water/fly ash ratio were varied in the synthesis of geopolymer and found to affect the geopolymer properties. Choice of source material is important parameters which affect the processing of geopolymer. Thermal activation is an essential requisite of geopolymer formation. However level and duration of thermal activation differs for various source materials. Heat overcomes activation barrier & enhances the dissolution rate of solid alluminosilicate material from byproduct materials such as ASTM class F fly ash. (Thakur R.N., Ghosh S., 2009) Curing at ambient temperature is also possible. However, exact properties of geopolymer mortar cannot be predicted from the properties of geopolymer paste. Plastic shrinkage induced cracking especially due to thermal curing affect. Addition of filer materials like sand up to a certain extent plays an important role in reducing