Geopolymer formulation for binder jet 3D printing

Abstract

The construction industry is a significant emitter of CO2 and it uses more than 40% of the resources consumed worldwide, which are becoming scarce. 3D printing can help to reduce the material consumption by enabling the manufactur-ing of structurally optimized building parts and formworks since material is only placed where needed. To combine the reduction of material consumption with less CO2 emissions, the raw materials that are currently used in 3D printing in construction need to be replaced by materials with lower carbon footprint. Among the materials with high potential for this application, geopolymer is a good candidate to fulfill the required criteria in terms of performances and em-bodied energy as they can be built from waste materials such as slag, fly ash or glass waste as aluminosilicate source. The objective of this research is thus to define a mix design strategy to allow the implementation of geopolymers in powder bed 3D printing with various waste materials. In this technique, an aluminosilicate powder bed is activated through the deposit of an alkaline silicate solution. This selective binder activation ap-proach requires to master the spreading of the liquid into the powder bed and to ensure that the reaction takes place where it is needed. A series of experiments at the droplet level were performed to estimate the relationship between the initial liquid to solid ratio and the packing of the powder bed. Based on this a mix de-sign strategy for the printing solution was developed and proofed by SEM/EDX analysis.