Synthesis of Hybridized Rheological Modifiers for 3D Concrete Printing (2020-07)¶

Viscosity and static yield stress are key rheological properties for 3D concrete printing (3DCP), where high static yield stress is associated with high buildability and shape stability and low viscosity is associated with extrudability and pumping. The challenge in concrete rheology lies in decoupling the effect of admixtures on these two properties, i.e. achieving high static yield stresses while still maintaining moderately low viscosities. In this paper, we present a hybridized additive system of nanoclays and viscosity modifying admixtures that can tailor the rheological properties of cement composites to meet 3DCP performance requirements. Further, because 3DCP is a technology of scales, any additive must meet scalability and stability requirements for construction, i.e. ease of processing in abundance and relatively low cost, and exhibit an extended shelf life. We examine different methods of synthesizing the hybrid systems and examine their stability through measuring their effect on cement rheology at different component ratios and at different time stamps from the time of hybridization. We then demonstrate their impact on printing performance by producing complex 3D prints utilizing cement pastes modified with the hybridized additive system.