Biomass fly ash-based alkali-activated materials

Abstract

Biomass fly ash (BFA), a by-product of wood biomass energy production, is difficult to utilize due to its low inorganic content. This study explored the possibility of using untreated BFA in alkali-activated materials (AAM). The used alkaline activator solution (AAS) is a mixture of Na2CO3 solution and Na2SiO3 solution with less alkalinity. This article systematically examined how the Na2CO3/Na2SiO3 (SC/SS) ratio of the AAS affected the structure formation, product synthesis, and physical-mechanical properties of BFA-based AAM pastes cured at 40 °C. Increasing the SC/SS ratio of the AAS from 0.40 to 1.20 increased the density (28 d, from 1287 to 1359 kg/m3 ) and compressive strength (28 d, from 2.36 to 3.97 MPa) of the AAM samples. The AAM sample with the lowest SC/SS ratio has the longest setting time and the highest water absorption. As the SC/SS ratio rose, gaylussite and C-S-H were synthesized in the samples, contributing to the compressive strength of the AAM pastes with higher SC/SS ratio, according to XRD analyses. The results of this study can help the development of eco-friendly BFA-based AAM.