Drying shrinkage behavior and internal curing mechanism of 3D printed lightweight ceramsite concrete

Abstract The drying shrinkage behavior of 3D printed lightweight ceramsite concrete (3DPLC) was experimentally investigated with emphasis on the effect of aggregate-to-cement mass ratio (A/C). The shrinkage evolution of 3DPLC was compared with that of conventional 3D printed concrete, which used manufactured sand and granite aggregates (SX group). Results show that 3DPLC exhibits a typical multi-stage shrinkage development, with 70∼80% of total shrinkage occurring within the first 28 days. Increasing A/C effectively reduces long-term shrinkage and stabilizes shrinkage development. Compared with the SX group, the 120-day drying shrinkage value of the C-2 group was significantly reduced by 61.4%. This improvement is attributed to the internal curing effect of ceramsite, which releases absorbed water and mitigates internal humidity gradients. The shrinkage behavior of 3DPLC is governed by the coupled mechanism of rapid surface evaporation and internal water release, which distinguishes it from conventional cast or printed concrete. Thermogravimetric analysis further confirms that the internal curing effect improves hydration uniformity and reduces moisture loss.