Exploration of using graphene oxide for strength enhancement of 3D-printed cementitious mortar

Graphene oxide (GO) sheet as a nanomaterial has been incorporated into cement-based composites to improve mechanical properties. This study investigates the effectiveness of GO sheets in enhancing the compressive strength of 3D-printed cementitious mortar. Two dosages of GO are investigated, including the GO-to-binder weight ratio of 0.015% (GO-0.015) and 0.03% (GO-0.03). Experiment results showed that adding GO at both dosages improved the compressive strengths of printed specimens in different loading directions. However, the strength improvement in GO-0.015 (∼10%) was more significant than GO-0.03 (∼5%). Although the scanning electron microscopy analysis demonstrated the cement matrix shared similar levels of microstructure densification in GO-0.015 and GO-0.03, the material underfill in 3D-printed GO-0.03 specimen due to its lower flowability generated large voids between filaments. Consequently, large voids acting as additional weakness offset the positive effects of GO on strength improvement in the 3D-printed specimen of GO-0.03.