Recycled aggregates materials are often relegated to downcycled applications such as backfilling. Different barriers limit their reintegration into higher-value construction use. This paper develops a probabilistic model of material flows using a Markov chain framework to simulate transitions between four states: Input, Use/Waste, Recycling, and Disposal. The model draws on Eurostat data covering non-metallic minerals in 27 EU Member States (2014–2023) and incorporates barrier-adjusted transition probabilities reflecting economic, technological, institutional, and social constraints. Scenario simulations reveal that improvements in recycling probabilities can yield nonlinear gains in material retention. However, once structural barriers are introduced, system performance declines sharply—even under favourable technical assumptions. The results suggest that modest policy interventions may have outsized effects if targeted toward key transition points.