![]() In another study of drill cores of Roman harbor concrete collected by the ROMACONS project in 2002-2009, Jackson and colleagues found an exceptionally rare mineral, aluminous tobermorite (Al-tobermorite) in the marine mortar. One factor, she says, is that the mineral intergrowths between the aggregate and the mortar prevent cracks from lengthening, while the surfaces of nonreactive aggregates in Portland cement only help cracks propagate farther. She first studied tuffs and then investigated volcanic ash deposits, soon becoming fascinated with their roles in producing the remarkable durability of Roman concrete.Īlong with colleagues, Jackson began studying the factors that made architectural concrete in Rome so resilient. Jackson’s interest in Roman concrete began with a sabbatical year in Rome. Tamura and Stan are scientists at the Advanced Light Souce. Left to right: Nobumichi Tamura, Marie Jackson and Camelia Stan at beamline 12.3.2 at the Advanced Light Source, Lawrence Berkeley National Laboratories. ![]() “This alkali-silica reaction occurs throughout the world and it’s one of the main causes of destruction of Portland cement concrete structures,” Jackson says. Any reaction with the cement paste could form gels that expand and crack the concrete. Modern Portland cement concrete also uses rock aggregate, but with an important difference: the sand and gravel particles are intended to be inert. Massive marine structures protected harbors from the open sea and served as extensive anchorages for ships and warehouses. The conglomerate-like concrete was used in many architectural structures, including the Pantheon and Trajan’s Markets in Rome. The Romans may have gotten the idea for this mixture from naturally cemented volcanic ash deposits called tuff that are common in the area, as Pliny described. The combination of ash, water, and quicklime produces what is called a pozzolanic reaction, named after the city of Pozzuoli in the Bay of Naples. Romans made concrete by mixing volcanic ash with lime and seawater to make a mortar, and then incorporating into that mortar chunks of volcanic rock, the “aggregate” in the concrete. Drilling is by permission of the Soprintendenza Archeologia per la Toscana. ![]() ROMACONS drilling at a marine structure in Portus Cosanus, Tuscany, 2003.
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