Data underlying the PhD thesis: Squeezing Concrete - A Numerical and Experimental Study on the Mechanisms within Auxetic Cementitious Composites

Concrete is the most widely used construction material in the world, but it has a fundamental weakness: it is brittle in tension. Conventional steel reinforcement solves this by bridging cracks once they form, but it remains largely passive until the matrix has already failed. This dissertation departs from an entirely different idea: what if the reinforcement could actively prevent crack formation in the first place?Unlike conventional materials that expand laterally when compressed, auxetic structures contract inward. When used as reinforcement embedded in a cementitious matrix, compressive loading causes the reinforcement to squeeze the surrounded mortar laterally, placing it in a state of multi-axial compression. This lateral confinement mechanism actively restrains crack localization, turning what would be a sudden brittle failure into a slow, distributed process with far greater energy absorption. The auxetic reinforcements studied here are fabricated using 3D-printing, which enables the geometrically complex lattice designs that auxetic structures require, but also introduces significant complications through porosity and weakened intra- and inter-layer bonds. Models that ignore these printing-induced imperfections consistently overestimate strength and predict entirely wrong failure modes. This motivates the development of printing path-dependent numerical models based on the Lattice Beam Model (LBM), which form the numerical backbone of the entire thesis.The LBM-based multi-scale framework is extended to the specimen scale, successfully reproducing the experimentally observed behaviour: when compressed, the auxetic reinforcement contracts laterally and confines the surrounded mortar, shifting its stress state into multi-axial compression. The result is a drastic improvement in post-peak performance: instead of the sudden splitting failure of plain mortar, the composite displays a long, gradual softening response with multiple fine distributed cracks.The LBM framework is further extended to full Tailored Poisson’s Ratio-reinforced Cementitious Composite (TPRCC) simulations subjected to bending. Internal stress and fracture analyses provide the clearest evidence of compressive lateral stress concentrations within the mortar of the tensioned chord, confirming active confinement. The models capture contrasting fracture patterns with striking accuracy, including fine features such as horizontal crack deflections and diagonal branching. Taken together, the dissertation delivers a complete multi-scale modelling framework, from printing path to specimen failure, and uses it to establish, explain, and validate a new reinforcement concept for cementitious composites.