Recycling waste materials, such as steel furnace slag (SFS), coal wash (CW), and rubber crumbs (RC) for transport infrastructure is environmentally friendly and offers significant economic benefits. This paper presents a fundamental study of the geotechnical characteristics of this blended matrix (SFSþCWþRC). A semiempirical constitutive model for SFSþCWþRC mixtures is proposed within the framework of critical state (CS) soil mechanics and based on the bounding surface plasticity theory. A CS surface is formulated with the changing RC contents in the waste mixtures, and an experimental relationship between the total work input (Wtotal) and CS parameter (Mcs) is established to capture the energy-absorbing capacity of the matrix. The theoretical model is validated using two sets of data, i.e., very recent triaxial test data obtained by the authors and totally independent test results from a past study conducted on sand-RC mixtures.