Additive manufacturing, commonly known as 3D printing, is current technology for easy and automatic manufacturing. In 3D concrete printing, the component is built by printing a series of single filament stacks. However, 3D printing of cementitious materials still has problems, such as decreased material strength and difficulty installing steel reinforcement.

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Fiber reinforcement is an alternative way to overcome the low strength problem of 3D concrete printing mixture. ECC (Engineered Cementitious Materials) is one example of fiber-reinforced cementitious materials with lower fiber content and has strain hardening behavior to overcome concrete's brittleness. ECC has an extended service life, excellent leak-proofing, impact absorption abilities, and reduced installation cost. ECC has better durability performance than ordinary concrete in terms of freeze-thaw, carbonation, and high-temperature resistance due to the bridging effect of fibers.

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ECC typically uses more cement than conventional concrete, which could have a higher carbon footprint. Hence, a new mix design is needed to reduce the cement proportion and replace it with supplementary cementitious materials. The other challenge is to adjust the fiber orientation to make the interlayer bond stronger. This way the material strength for both the stack direction and print direction are excellent.

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The research aims to determine the greener mixture proportion and 3D printing framework by evaluating rheology, microstructure, mechanical properties, and durability under multiple environmental conditions.