Interlayer adhesion and strength of structures in Contour Crafting - Effects of aggregate size, extrusion rate, and layer thickness

- The structural integrity of Contour Crafted structures is investigated.
- A concrete mixture which is compatible with the existing extrusion system is proposed.
- Effects of the aggregate size on early strength development of the mixture are studied.
- The impacts of fabrication parameters on the interface bond strength are analyzed.

Contour Crafting (CC) is a method that builds coherent concrete structures in a layer-by-layer fabrication fashion. During fabrication, layers must be bonded together to make a homogenous structure, as there is no vibration or external force during layer deposition. This research investigates the structural integrity of Contour Crafted structures using experimental approaches to analyze the bond strength between layers. Initially, a concrete mixture which the compressive and tensile strength is significantly improved through modifying the aggregate size and aggregate to cement ratio is developed. The mixture is compatible with an existing extrusion system and it is tested to quantify the strength at interface for different extrusion rate and layer thickness. The results show that an improvement of up to 16% at interface is achievable for different fabrication conditions.