Ancient Roman architectural and marine cementitious systems, fabricated in 1st C BCE–2nd C CE with hydrated lime-volcanic tephra mortar (materia) and coarse rock aggregate (caementa), provide invaluable guideposts for creating self-sustaining and self-reinforcing environmentally-friendly concrete materials that increase in chemical and mechanical resilience over time. A recent applied research and technology-to-market project has fabricated Roman analog concrete materials that represent a cost-effective and highly durable alternative to modern portland cement concretes (PCC), which experience long term performance degradation especially when reinforced with steel rebar. Pozzolanic reactions with a proprietary synthetic tephra aggregate produce a calcium-aluminium-silicate-hydrate (C-(K, N)-A-S-H) binding phase. Ongoing reactions within the synthetic tephra (or volcanic rock) aggregate produce zeolite mineral cements, which reinforce interfacial zones and refine pore space. Geochemical analyses indicate that interstitial fluid compositions evolve as the aggregate reacts, thus determining which mineral cements precipitate and contribute to chemical and mechanical resilience. These processes and the cementitious fabrics of the analog mortars reproduce those of highly resilient Roman concretes. The durability of ancient Roman concrete systems, with service lives on the century scale, contrasts starkly with the short service life of most PCC. This has motivated development of an innovative arc-fracture test that measures the resilience and potential longevity of cementitious materials, as opposed to initial strength. The arc-fracture test has determined the structural response of Roman analog concretes as fractures nucleate and propagate, in addition to characterizing regenerative repair processes in the concrete fabric. The results indicate a highly ductile initial fracture response followed by self-repair of induced fractures, which results in an appreciable recovery of initial structural carrying capacity. The estimated material first cost per cubic yard of the Roman analog concrete is about the same as unreinforced PCC. However, the installation cost and CO2 evolved per cubic yard is substantially less than PCC with steel reinforcement. The environmental and economic benefits of the Roman analog concretes as compared to PCC are further compounded by substantially longer service lives, which reduce costs associated with maintenance and replacement.

Roman analog concretes with reactive aggregates as self-sustaining construction materials

Where thousands of chemistry professionals meet to share ideas and advance scientific and technical knowledge. Spring 2023 abstracts, posters, and presentations will launch at the end of March.

ACS Spring 2023

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.