Regulating the early rapid water release and eliminating the macro void of superabsorbent polymer by embedded porous rigid skeleton

The early rapid water release from superabsorbent polymer (SAP) and the macro-voids left after water release are the main challenges of SAP for internal curing purpose. Inspired by the water release essence of conventional SAP, a new type of SAP composite with inorganic rigid skeleton (RS@SAP) was designed. The hydrogel was in-situ polymerized and assembled in porous skeleton, and the contact area between hydrogel and cement matrix was thus reduced to slow down the early rapid water release. Different from normal SAP, RS@SAP showed a three-stage water release behavior governed by osmotic pressure, capillary action, and combined humidity gradient/capillary forces. This multi-modal regulation achieved an effective water utilization rate of 72.2 %, exceeding the value of conventional SAP by 68.4 %. Microstructural analysis confirmed the suppression of diffusion pores and macro-voids, while mechanical testings revealed reduced negative impacts on compressive strength due to skeletal reinforcement and enhanced interfacial zone properties.