Powdered banana peel in calcined halloysite replacement on the setting times and engineering properties on the geopolymer binders

This project aims to study the effect of ripe powdered banana peel (BP) on properties of calcined halloysite based geopolymer activated with alkaline silicate solution. Ripe powdered banana peel (BP) obtained after drying and milling banana peels was mixed with calcined halloysite (MH) at the rate of 0, 5, 10, 15 and 20 wt% by weight of binder. Setting time, compressive strength, water absorption, porosity and bulk density of resulting geopolymer products were investigated. The 28-days compressive strength increased from 33.2 to 44.8 MPa with 10% then decreased to 35.7 MPa and 32.2 MPa at 15 and 20% of BP, respectively. SEM micrographs indicated that MHBP10 sample containing 10 wt% of BP exhibited a homogeneous denser matrix with less unreacted particles and fissures justifying the improvement of the mechanical properties of geopolymer binder. Thus, using ripe powdered banana peel provides additional alkali sources (K and Na) which could have improved the dissolution of calcined halloysite resulting in high polycondensation. However, the amount of BP would not exceed 10 wt%. The use of powdered banana peel as alkali source in geopolymer appears as efficient way to reduce the amount of silicate products usually use in the geopolymer technology. © 2021 Elsevier Ltd. All rights reserved.