Criticality of Binder-Aggregate Interaction for Buildability of 3D Printed Concrete Containing Limestone-Calcined-Clay (2022-11)¶

The study aims at understanding the criticality of interaction between the binder matrix and aggregate when a 3D printable mix is subjected to compression at an early age. Two binder systems containing fly ash and limestone calcined clay (LC2) as supplementary cementitious material are compared based on flowability and compression at an early age. The superplasticizer (SP) dosage for the mix with LC2 is observed to increase significantly to maintain equivalent flowability as the mix with fly ash. Compressive rheology (squeeze flow) test is performed at 5 and 30 min, and it is observed that the mix with LC2 shows an enormous growth in the compressive stress restraining capacity with time. Further, the effect of two types of aggregate, namely uniformly graded quartz sand (maximum size of 2 mm) and well-graded crushed stone sand (maximum size of 4.75 mm), on buildability is studied. It is observed that the total printed height of the hollow cylinder before collapse increases from 220 mm for quartz sand mix to 1.14 m for mix with crushed stone sand, possessing the same flowability. It is also observed that when the layers are subjected to compression due to printing, the rheological properties of the binder matrix are more critical within the first few minutes (5 min) of deposition, whereas the binder matrixaggregate interaction becomes the influencing factor at later ages (30 min).