A STUDY ON THE COMPRESSIVE STRENGTH AND MINERALOGICAL PROPERTIES OF FLY ASH AND RED MUD BASED GEOPOLYMER MORTAR Dr. B HANUMANTHA RAO, IIT BHUBANESWAR, ODISHA, INDIA – 752050. Introduction Chemical Composition of Fly ash & Red mud Compressive Strength & Mineralogical Properties Material Oxide Compositions (In weight %) SiO2 Al2O3 Fe2O3 CaO Na2O K2O Other oxides LOI* Fly ash 61.9 28.10 4.15 0.89 0.37 0.80 3.3 0.48 Red mud 14.6 25.26 45.31 1.19 4.80 - 2.7 6.5 Compressive strength is decreasing with the increase in the red mud proportion in the mix. With the increase in red mud, the total silica content is reducing which could be the reason for decrease in the strength. Also decrease in the strength with time is noticed when the red mud content is 20% or more. FLY ASH RED MUD 1 tonne of cement production leads to emission of equal amount of CO2 Generation of huge amount of industrial wastes such as fly ash, red mud. Storage area construction and its maintenance are highly cost-intensive. Geopolymers have the potential to use industrial wastes and completely avoid cement usage. Utilization of fly ash, and red mud through geopolymers as an environmental protection material would be big step towards green revolution. Mix Proportioning of Fly ash-Red mud Mortar Increase in the red mud content is inhibiting the geopolymerization. With an increase in the red mud content, the increase in the amount of unreacted particles can be seen. This could be causing decrease in strength of the mortar specimens. Mix Na2SiO3 /NaOH AAS to BS Fly ash (kg/m3) Red mud (kg/m3) Sand NaOH Na2SiO3 Remarks FA 1.5 0.5 714 1286 143.8 214.2 Na O H 14M M1 709 37 1353 149.3 224 M2 671 75 1354 149.2 223.8 M3 633 112 1355 149.1 223.6 M4 596 149 148.9 223.4 M5 558 186 1356 148.8 223.2 M6 520 223 1357 148.6 222.9 M7 483 260 1358 148.4 222.7 OPC Binder vs Geopolymer Binder SEM images of geopolymer mortars of various mixes after 28 days of curing leaching of sodium and ferrous ions are increasing with time, where the red mud content in the geopolymer mixes is exceeding 15%. This could also be another reason for the decrease in the strength with time. FA: 100% Fly ash; M1- 95% FA + 5% RM; M2- 90% FA + 10% RM; M3- 85% FA + 15% RM; M4-80% FA + 20% RM; M5- 75% FA + 25% RM; M6: 70% FA + 30% RM; M7: 65% FA + 35% RM Cubes cast with different FA & RM combination MATERIALS USED Elemental compositions at 28 days SUMMARY Fly ash alone based geopolymer mortars showed better compressive strength, as high as 51 MPa, over its counter parts and it found to increase with time. With increase in the red mud content in the mix, the compressive strength decreases. Red mud content above 15% is unacceptable because of strength properties. Increase in the leaching of sodium and ferrous ions with time takes place when the red mud content in the geopolymer mixes is above 15%. Specimens prepared for experimental investigation