Collaborative Research: Fungi-Based Biological Upcycling of Waste Concrete into Durable Infrastructure Materials

Concrete demolition generates hundreds of millions of tons of waste in the United States each year. Although some demolished concrete is reused, much of it becomes low-value road base, fill, or discarded fine powder rather than a dependable ingredient for new concrete. This underuse increases disposal costs, consumes space, and sustains demand for newly quarried stone, dredged sand, and manufactured cement. This project will advance biological methods for converting demolished concrete into reliable materials for future infrastructure. By improving recycled aggregate and finding beneficial uses for crushing fines, the project will conserve domestic resources, reduce solid waste, and support more durable and efficient rebuilding of roads, bridges, and buildings. The work serves the national interest by promoting the progress of science, advancing national prosperity and welfare through better use of waste resources, and strengthening the construction materials supply chain. The project will train undergraduate and graduate student researchers. Educational activities, research opportunities, demonstrations, and public presentations will be open and broadly available, and results will be shared through publications, courses, partnerships with industry and transportation agencies, and practitioner education. The technical goal of this work is to establish a biological pathway for the complete upcycling of waste concrete into structural concrete ingredients. The research will investigate how naturally occurring oxalate-producing fungi strengthen recycled concrete aggregate by forming insoluble minerals and silica within pores, cracks, and surface defects, thereby reducing water absorption, improving abrasion and crushing resistance, and decreasing variability among aggregate sources. The research will also use biologically produced organic acid to dissolve cementitious phases in recycled concrete fines and convert them into blends of functional fillers and reactive silica that can partially replace portland cement. Experiments will quantify the effects of fungal strain, cell density, calcium source, nutrient level, acidity, temperature, treatment duration, and vacuum soaking on mineral formation and aggregate properties. Converted fines will be characterized for physical properties, mineral composition, and reactivity. Mortar and concrete mixtures containing treated aggregates and converted fines will be tested for workability, mechanical properties, volume stability, and durability. Molecular simulation, microstructural characterization, life cycle analysis, and technoeconomic analysis will clarify mechanisms, cost drivers, scalability, and practical adoption pathways. The results will establish design principles for biological upcycling of demolished concrete into durable structural concrete. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.