Mechanical and microstructural properties of geopolymer mortars from meta-halloysite: effect of titanium dioxide TiO2 (anatase and rutile) content

Abstract: This study aimed to investigate the effect of Titanium Dioxide TiO2 (anatase and rutile) on mechanical and microstructural properties of meta-halloysite based geopolymer mortars namely GMHA and GMHR series. Meta-halloysite received 2.5, 5.0, 7.5 and 10 wt% of anatase or rutile as addition before calcination and geopolymerization. The raw materials and the end products were characterized using XRD, FTIR, ESEM and MIP analyses. The flexural strength increases from 6.90 to 9.13 MPa and from 6.90 to 12.33 MPa for GMHA and GMHR series respectively. The cumulative pore volume decreases from 102.2 to 84.2 mm3 g−1 and from 102.2 to 51.3 mm3 g−1 for GMHA and GMHR products respectively. Both matrices present micrographs with very low capillaries pores and fractured surfaces that confirmed the enhancement of the mechanical properties. It was concluded that TiO2 in both forms is beneficial for the reduction of porosity and densification of geopolymer matrices. Rutile enabled more compact and denser geopolymer structure compared to anatase. The aforementioned results showed the efficiency of both fine TiO2 particles to improve the geopolymer network significant for its durability. Graphic abstract: [Figure not available: see fulltext.].