Effect of absorption kinetics of superabsorbent polymer on 3D printing characteristics

This study evaluates the effect of different superabsorbent polymers (SAP) types on rheological properties, printability, and mechanical properties of 3D concrete printing (3DCP). Three types of SAP, including two acrylamide-co-acrylic polymers with coarse and fine particle sizes (S1 and S2) and an acrylic copolymer (S3), were employed. Results showed that the use of S1 and S2 SAP exhibiting high retention ability enhanced thixotropy, whereas the S3 SAP with rapid desorption reduced thixotropy. The S1 SAP was the most significant in maintaining a higher internal relative humidity, thus resulting in higher 28-d compressive strength. The reduction in 28-day compressive strength for printed specimens was correlated with the increase of static yield stress in 5 min (τfloc). The S3 SAP acted as a rheology-modified agent to reduce τfloc and the loss of 28-day compressive strength for printed specimens by 10%-20%.