Research Projects
Prototype Design and Additive Manufacturing for Improved Engineering Performance of Mass Timber Components Using Forest Residues
This project uses robotic extrusion to print earth-based composite layers of clay-rich soil, biochar, and hemp fiber directly onto cross-laminated timber (CLT) panels. The timber carries the structural load, while the printed layer adds thermal mass, acoustic damping, and moisture buffering. We are optimizing mixture designs for printability, shrinkage control, and compressive strength, and fabricating prototype components to evaluate performance. The work turns Oregon’s forest and agricultural residues into higher-value, low-carbon building components.
Funding agency: USDA-Agricultural Research Service
Integrating soil mechanics into the development of printable soil mixtures
Once an earthen layer leaves the nozzle it behaves as an unsaturated soil, so drying-induced matric suction largely decides whether a printed wall stands and how much strength it gains. We bring unsaturated soil mechanics into printable mixture design. Our suction-based framework uses a diffusion model to track suction as each layer dries, then converts that suction to shear strength through the Fredlund framework to predict buildability.
We tested the framework on clay–sand mixtures with 30 to 70% clay, measuring suction with HYPROP and WP4C. Predicted buildability matched experiments, with up to 21 stable layers. At placement, buildability depends on cohesion and interparticle friction. Over time, suction-mobilized friction takes over and supplies 80–90% of shear strength after seven days. Longer intervals between layers increase buildability, higher humidity reduces it, and temperature has little effect.
The result is a physics-based way to match binder-free earthen mixtures and print schedules to local soils and climates.
Funding agency: Engineering and Research Development, US Army Corps of Engineers, U.S. Department of Energy
Geochemistry-Informed Durability of Stabilized Soils
We combine computational geochemistry with experimental testing to understand and predict how chemically stabilized soils perform over their service life. Thermodynamic and kinetic modeling predicts the strength-enhancing pozzolanic products that form during stabilization, while experimental characterization measures the resulting engineering performance. We apply this coupled approach to durability under aggressive conditions, including seawater intrusion and the pH drawdown that stabilized soils experience under flooding and leaching. By linking pore-solution chemistry to measured strength and stiffness, our work provides a physically grounded basis for designing stabilized soils that remain durable in harsh environments.
Funding agency: Engineering and Research Development, US Army Corps of Engineers, University Transportation Center, Cascadia Lifelines Program (CLiP)
Rapid Stabilization of in-situ weak soil
Overview:
Rapid stabilization of expansive soils has significant potential to support infrastructure development, particularly highway pavements. Historically, several studies have attempted to develop a stabilizer that can rapidly convert weak soils to strong soils with little manipulation and straightforward construction protocol. Often, such studies have recommended the use of non-traditional stabilizers that have not been widely implemented. This study aimed to develop and evaluate the use of a mixture composed of conventional stabilizers such as lime, metakaolin, and sodium silicate for rapid strength gain of expansive soils.
Funding agency: Cascadia Lifelines Program, US-Army Engineering and Research Division