Selectable Cutting and Fragmentation of Damaged Runway Surfaces

A microwave system is under development for rapid, precise and safe separation and fragmentation of damaged airfield pavements in a post-event environment. This lightweight and compact system minimizes the generation of dust, noise, foreign object debris and waste, requires limited on-site labor, and is amenable to remote control. The microwave system employs concentrated input of microwave energy to induce a “thermal runaway instability” that efficiently softens/melts concrete within a narrow region for convenient and precise separation of the damaged pavement without affecting the neighboring (undamaged) regions. Application of less concentrated microwave energy to the separated parts of concrete causes a rapid rise in vapor pressure and restraint (primarily thermal) stresses that fragment/beneficiate concrete for value-added use in subsequent repair efforts. The Phase I project designed and manufactured open-ended microwave systems, and successfully verified their ability to separate and fragment concrete via rapid generation of vapor pressure and restraint stresses in different modes of operation. Developments undertaken beyond the Phase I project demonstrated the potential for rapid, precise and efficient separation of concrete via localized softening/melting under concentrated input of microwave energy. Competitive analyses conducted in the Phase I project pointed at the promise of the technology to provide distinct performance, cost, energy-efficiency and environmental advantages over existing and emerging technologies. The proposed Phase II project will: (i) Design and manufacture microwave systems with alternative modes of operation for efficient, expedient and precise separation and beneficiation of damaged airfield pavements; (ii) Develop and thoroughly characterize alternative concrete mixtures with different microwave susceptibility, thermomechanical and barrier attributes for use in airfield pavements; (iii) Experimentally evaluate the performance attributes of alternative microwave systems with different concrete materials, and identify the preferred system for field demonstration; (iv) Verify field performance of the selected microwave system in representative post-event conditions in an Air Force facility; and (v) Assess the competitive performance and cost merits of the selected microwave system in light of the Air Force requirements for selectable removal and beneficiation of damaged runway surfaces. In addition to concrete, the Phase II project will assess the microwave system capabilities in application to asphalt, flowable fill, rocks, composites, and steel.