Nano-Modified Materials for New Construction Technologies (2023-08)¶

Self-compacting concrete (SCC) and 3D printing (3DP) have become two of the most innovative and promising construction technologies for the XXI Century Architecture with cement-based systems (CBS). Both applications require specific fresh material properties, fluid in the first case and firm in the second one. However, material cast-in-place in both technologies shows similar issues to be addressed regarding material fresh state rheology and its control. The main rheological parameters to consider for fulfilling cast-in-place requirements are shear yield stress, viscosity and structural build-up. Besides, mechanical properties as compressive yield stress, Young modulus and critical strain must also be considered at early age, when setting begins. Nano-modification can be the answer to modify fresh state rheological and early age mechanical parameters of CBS. The aim of this study was the evaluation of CBS rheological behaviour with nanocomponents and VMAs for SCC and 3DP applications. The combined use of nanocomponents (NC), as nanoclays and nanosilica, and viscosity modifying admixtures (VMAs) has shown the ability to tune CBS rheology. Moreover, the addition of a high-range water-reducing admixture (HRWRA) is essential to produce CBS with an appropriate consistency and workability, although some incompatibilities with other components have been described. CBS rheological and mechanical parameters can be studied using specific experimental test methods, depending on the properties and the consistency required by each technology and application. Nano-modified CBS showed an increase of shear yield stress while the addition of VMAs increased viscosity. The combination of both components produced synergetic effects in the material over time, overcoming issues observed for both technologies.