Concrete is the most widely used engineering material. While strong in compression, concrete is weak in tension and exhibits low ductility due to its low crack growth resistance. With increasingcompressive strength, concrete becomes even more brittle, hence requiring appropriate reinforcement to enhance its ductility. This paper presents a new method for increasing the ductility of ultra-high-performance concrete by reinforcing it with 3D printed polymeric lattices made of either polylactic acid (PLA) or acrylonitrile butadiene styrene (ABS). These latticereinforced concrete specimens were then tested in compression and four-point bending. The effect of polymeric reinforcement ratios on mechanical properties was investigated by testing two lattice configurations. The lattices were very successful in transforming the brittle ultrahigh-performance concrete (UHPC) into a ductile material with strain hardening behavior; all flexural specimens revealed multiple cracking and strain hardening behavior up to peak load. Increasing the ABS reinforcing ratio from 19.2% to 33.7% resulted in a 22% reduction in average compressive strength. However, in flexure, increasing the PLA reinforcing ratio from 19.2% to 33.7% resulted in a 38% increase in average peak load. The compression results of all specimens independent of their reinforcement ratio revealed smooth softening behavior incompression.

Recent advances in the development of Ultra-High Performance Fiber-Reinforced Concrete (UHP-FRC) with very high compressive strength has inspired the development of a lightweight structure by engineering the void spaces in the material, thus taking advantage of porous concrete’s thermal insulating properties while maintaining strength and stiffness. This paper refers to this engineered material as Octet-Truss Engineered Concrete (OTEC). To make OTEC structures, UHP-FRC and “green” UHP-FRC (G-UHP-FRC) mixtures were developed. 50.8-mm side-length OTEC unit cell specimens with various element diameters as well as 5×1×1-cell OTEC flexural specimens with 8 mm-diameter elements were cast and tested under uniaxial compression and four-point bending, respectively. The compressive strength of the OTEC unit cell specimens with various element diameters is mainly stretching-dominated, and hence considerably surpasses that of the control foam Green Ultra-High Performance Concrete specimens with random pore orientations. These results indicate a promising application of UHP-FRC and G-UHP-FRC OTECs for lightweight structures.