3D printing of cementitious materials with superabsorbent polymers: a durable solution?

Abstract

Nowadays, 3D printing of cementitious materials is a hot research topic in the construction industry. This construction method is capable of producing complex geometries and largescale components without the use of expensive formwork. However, due to the lack of molding, more shrinkage will be induced and the amount of cracks will increase. As this phenomenon introduces ingress paths for chemical substances, it will affect the durability of the printed element in a negative way. One potential way to tackle this disadvantage is to include superabsorbent polymers (SAPs) in the cementitious material. As these polymers are able to absorb part of the mixing water and to release it during hardening, they induce internal curing and can mitigate self-desiccation and autogenous shrinkage. Another positive effect of using SAPs is the increased moisture content of the printed surface, enhancing the bond between two subsequent layers. For the aim of this research, two different SAPs were used to fabricate printed elements and the microstructural changes are correlated with their influence on durability and sustainability. First results showed that in general, the addition of superabsorbent polymers decreases the shrinkage in printed materials. They also reduce the nanoporosity in the range of 100 nm to 500 nm and increase the amount of voids with a diameter above 700 nm, resulting in less microcracks and a decreased amount of preferential ingress paths for chemical substances. On the other hand, the total air content increases with the addition of SAPs, proportional to the amount of SAPs added.