Physico-mechanical flammability and leachability characteristics of fly ash/slag based foamed geo polymer concrete blocks

390-402In-situ foamed geo polymers have been produced from fly ash/slag blend, surfactant, hydrogen peroxide (H2O2) and sodium silico fluoride in an alkaline medium and evaluated their physico-mechanical, micro structural and fire characteristics as a function of foaming agent. Isothermal calorimetric response has been indicated that the rate of geo polymerization for the foam slurry was ~25% more than its un-foam slurry. An increase of H2O2 from 0.5 to 3 wt% has reduced the compressive strength of foamed geo polymers from 7.2 to 2.45 MPa. As observed in field emission scanning electron microscope (FESEM), the pores have been spherical ranging in sizes between 42 µm and 585 µm with varying H2O2 dosages. The relationship between the compressive strength and porosity has been in agreement with the exponential model. The thermal conductivity of foamed geo polymers has ~36% less than the commercial cellular concrete at a density of 1000 Kg/m3. Flammability test has shown that the samples belong to D class as per ISO 11925-2 and also exhibiting no support to the fire growth when tested as per BS 476-6. During immersion in water, the alkali leaching (pH 11-12.2) and also the fractional release of Na (22 ppm) and Si (18 ppm) under TCLP test have been observed. Based on the results, the foamed geo polymer blocks have been produced with satisfactory properties as per the requirements of commercial specification of cellular concrete blocks