Assessment of morphological characteristics and physico-mechanical properties of geopolymer green foam lightweight aggregate formulated by microwave irradiation

Abstract

This research work was as alkaline activator as well as foaming agent, however, small amount of sodium hydroxide (1%) and 1–2% sodium bicarbonate (NaHCO3) were also used. Nine types of green FLWA pellets were formulated by varying the proportions of foaming agent and sodium bicarbonate and all pellets were cured in instantaneous thermal irradiation of microwave oven for only 5 min. After foaming in microwave, characterization of porous green FLWAs were assessed; large pores (up to 7 mm) at cross section of pellet, expansion (up to 30%) and weight reduction (up to 30%) were observed with the increase in the amount of foaming agent, whereas apparent density reduced. Water absorption was slightly higher than the recommended ACI values due to internal porous structure of FLWA. However, high particle crushing strength (1.11 MPa) was observed for pellets with 54% foaming agent and 1% NaHCO3, therefore this optimized ratio of FLWA mix was selected for casting green lightweight concrete (LWC). Density, compressive strength, flexural strength, and sorpitivity were evaluated and it was observed that density was within acceptable range as specified by ACI for LWC. Flexural strength was also high (4.29 MPa) and showed strong potential to be used as panels of false ceiling for insulation. Sorpitivity results were also consistent with the performance of green FLWA. Therefore, adopted curing technique can be considered as rapid and sustainable solution for formulation of green FLWA and recommended to be applied at industrial scale for reducing dead load of structure.