Peer-to-Peer Webinar: Cementitious materials for advanced construction

Theme of the Peer-to-Peer Webinar: Cementitious materials for advanced construction

REGISTER FOR FREE HERE.

Speaker 1: Robert J. Thomas, Ph.D., Clarkson University, USA

Title: Space concrete - The final frontier

Eight thousand years ago, the Nabataea Bedouins built cisterns from hydraulic lime. Five thousand years ago, ancient Egyptians used gypsum and lime to make masonry mortars. Two thousand years ago, the Romans built the Pantheon with hydraulic lime and volcanic ash. Two hundred years ago, an English bricklayer patented portland cement. And twenty years ago, construction began on the Burj Khalifa, which now stands as not only the tallest concrete structure—but also the tallest man-made structure of any kind—in the world. For thousands of years, concrete technology has continued advancing. But for thousands of years, concrete has been tethered to Earth’s surface. Now, as the international space community plans for a sustained human presence on Earth’s Moon, concrete technology faces a new frontier—a challenge to use in-situ planetary resources to build landing pads, human habitats, and other critical infrastructure on the Lunar surface and beyond. This presentation will outline the challenges and opportunities around the development of concrete materials for extraterrestrial infrastructure, focusing on the general principle of in-situ resource utilization and how humans can harness geopolymer technology to produce concrete on the Moon.

Speaker 2: Shashank Gupta, Ph.D. Candidate, Princeton University, USA

Title: Tough Cortical-Bone Inspired Tubular Architected Cement-based Material

Natural materials demonstrate an exceptional combination of competing mechanical properties, fracture toughness and strength, by assembling modest constituents into complex arrangements and hierarchical architectures that trigger clever toughening mechanisms. Cortical bone is a tough shell of the human femur bone and is composed of elliptical tube-like osteons embedded in the organic matrix that is surrounded by weak interfaces known as cement lines. The cement lines provide a preferable micro-structural path for crack growth, hence triggering in-plane crack deflection around elliptical osteons due to cement line-crack interaction. Inspired by cortical bone’s toughening mechanisms, the tubular architected cement-based materials are engineered into the design and fabrication by employing a hybrid 3D-printing and casting method as well as a layer-wise additive manufacturing process.

In this webinar, we demonstrate using experimental, theoretical, and numerical approaches that tubular architected cement-based material exhibits significantly improved fracture toughness and a non-brittle fracture response compared to conventional monolithic brittle counterparts without sacrificing flexural strength. This improvement is enabled by crack-tube interaction which leads to a new stepwise cracking toughening mechanism, from which a non-brittle fracture can emerge. The tubular geometry, tube size and shape, compete to alter the stress intensity factor which can be engineered to enable stepwise cracking. The stepwise cracking promotes rising R-curves vs. the flat brittle response of solid (without the tubes) counterparts. These tubular architected materials composed of brittle components can be exploited to promote a global non-brittle behavior and enhance damage tolerance by pinning the crack to the tubes. The findings can be extended to quasi-brittle materials such as mortar and concrete, contributing a strategy for enhancing the fracture toughness of concrete materials while reducing material usage through the deliberate design of intentional defects.

This webinar is brought to you by the RILEM Youth Council (RYC) and hosted by Olga Beatrice Carcassi (North America RYC representative) in collaboration with the American Concrete Institute.