| Abstract Scope |
This study examined the effects of adjusting proportions of water, cement, fine and coarse aggregates, shrinkage-reducing and -compensating admixtures, as well as metakaolin (MK) calcined clay, on the shrinkage of 3D printed concrete (3DPC). Printable mixes were first developed using an in‑situ caulk gun extrusion test and the modified ASTM C1437 slump flow test. Buildability was further evaluated using unconfined compression to obtain time-dependent green strength and Young’s modulus, revealing that MK mixes gained strength rapidly compared to control concrete and mortar mixes. Unrestrained shrinkage was measured using 3 in. × 3 in. prisms via a modified ASTM C157. MK mixes showed high early shrinkage but significantly reduced long‑term shrinkage relative to other designs. ASTM C157 failed to capture the shrinkage‑reduction effect of shrinkage-compensating admixtures. This study proposes using ASTM C1581 in future work to quantify the effects of these admixtures.
Keywords: 3D printed concrete (3DPC), metakaolin (MK), calcined clay, shrinkage-reducing/-compensating admixture, slump flow, buildability, drying shrinkage. |