THE EFFECT OF INTERLAYER BOND STRENGTH ON THE MECHANICAL BEHAVIOUR OF 3D PRINTED MORTAR WITH BIOCHAR

Abstract

The built industry contributes to 40% of energy and process-related carbon emissions, with cement production and preparation contributing to a large proportion of this. With global building stock set to double by 2050, finding solutions and efficient practices are vital. Recent advancements in additive manufacturing within the built industry have shown the potential that environmental and economic benefits 3D printing possess. Biochar is considered an alternative to cement as it captures carbon and improves mechanical strength of mortar mixes. This paper looks at integrating material (biochar) and method (3D printing). A major weakness of 3D concrete printing is the bond strength between layer interface, which decreases if resting time between layers increase. This paper hypothesises that biochar improves interlayer bond strength due to its ability to retain water and slow the rate of hydration at the free, exposed surface of the layers. A series of mechanical strength tests were conducted on printed concrete samples containing biochar to test this hypothesis. The results show that while biochar enhances the intrinsic material strength of the printed concrete, it is unable to increase its interlayer strength. Biochar seems to draw water away from the interface and into its pores, increasing the rate of hydration and negatively affecting the interface bond strength. However, biochar greatly enhances overall mechanical strength, a characteristic beneficial to 3D concrete printing. Further research is necessary to optimise the mortar mix and type of biochar used, to continue investigation into improving interlayer bond strength.