Novel strategy for autogenous shrinkage mitigation by combining internal curing and self-compensation: Carbon nanotube sponge with carbamate solution absorbed

Abstract

Internal curing and self-compensation are two different approaches to mitigate autogenous shrinkage, with their own pros and cons. In this study, strategies of internal curing and self-compensation are combined in a single material by pre-absorbing hydrophilic carbon nanotube sponge with L-Serine based carbamate (H-CNTSP@C-Ser). In contrast to the detrimental effects of C-Ser when directly mixed with cement, the autogenous shrinkage and compressive strength of cement can be reduced and enhanced by 81.8 % and 44.4 %, respectively, with the addition of 0.05 wt% H-CNTSP@C-Ser, as compared to the control sample. This comparison strongly confirms the importance of the controlled release of C-Ser. After setting, the hydrolysis of the released C-Ser solution pre-absorbed within H-CNTSP promotes the precipitation of CaCO₃, which can not only induce expansion for self-compensation of shrinkage, but also promote the formation of C-S-H with a higher modulus, thereby leading to an enhanced compressive strength of cement paste.