Thermo-chemico-mechanical activation of bagasse ash to develop geopolymer based cold-pressed block

Abstract

• Sugarcane bagasse ash (BA) is used as precursor to develop geopolymer brick. • Reactivity of BA was assessed, and its semi-dry paste was thermo-chemcio-mechanically activated. • Dune sand and river sand was used to further enhance the strength. • Good physico-mechanical relationships have been obtained and results are aligned with ASTM specifications. • FTIR analysis reconfirm the results and strengthen the discussion at molecular level. Sugarcane bagasse ash (SCBA) is an agricultural waste, and it is well recognized as pozzolanic material after calcination. However, it’s potential to be used as precursor in geopolymerization; in raw form, after calcination or chemical treatment, along with the cold pressing is not being investigated in depth. Therefore, this experimental work was designed in which initially, the reactivity of SCBA was assessed by a modified Chapelle test, TGA, and XRD analysis. And later a paste was formed by mixing FA with different dosage of SCBA (10–30 wt%) in an alkaline environment and then further activated mechanically. Afterwards dune sand, another industrially discarded material, was also mixed to formulate mortar and to get benefits of its natural fineness. For mechanical activation, 20 MPa molding pressure was applied and a reduction in strength was observed by increasing SCBA contents. Whereas an increase in strength was observed when calcined SCBA was used (thermo-mechanical activation). The 20 % SCBA has almost the same results under both activation modes and therefore this percentage was selected for mortar formulation and a further increase in strength (up to 73 %) was observed. The strength gain mechanism was discussed at the molecular level by conducting FTIR analysis. Among all techniques, the mechanical activation and incorporation of dune sand was found to be the best choice. Furthermore, the physico-mechanical relationship was established, and the developed block was compared with the fired clay brick. It was observed that developed block has a lower density (1600 kg/m 3 ), lower water absorption (less than 15 %), and more strength than the limit specified (10.7 MPa) by ASTM standards. Moreover, by incorporating sand the strength criterion (21.3 MPa) for severe weathering condition was also achieved.