Reactive binder and aggregate interfacial zones in the mortar of Tomb of Caecilia Metella concrete, 1C BCE, Rome

Integrated spectroscopic analyses and synchrotron X-ray microdiffraction investigations provide insights into the long-term reactivity of volcanic aggregate components calcium-aluminum-silicate-hydrate (C-A-S-H) binder in mortar samples from robust concrete sepulchral corridor Tomb Caecilia Metella, 1st C BCE, Rome. The results innovative micrometer-scale analytical maps indicate that Pozzolane Rosse tephra components–scoria groundmass, clinopyroxene, leucite crystals–contributed to pozzolanic production C-A-S-H then remained reactive long after hydrated lime (Ca(OH)2) was fully consumed. binding phase is reorganized wispy halos tendril-like strands, some with nanocrystalline preferred orientation or, alternatively, split elongate features short silicate chain lengths. These microstructures apparently record chemical structural destabilization during excessive incorporation Al3+ K+ released through dissolution. Resistance failure may result intermittent toughening interfacial zones scoriae clinopyroxene crystals post-pozzolanic strätlingite Al-tobermorite mineral cements remodeling phase. Roman builders’ selection a leucite-rich facies as construction tomb an environment high surface ground water exposure increased beneficial hydrologic activity concrete.