Ancient Roman architecture
Although concrete had been used on a minor scale in Mesopotamia, Roman architects perfected Roman concrete and used it in buildings where it could stand on its own and support a great deal of weight. The first use of concrete by the Romans was in the town of Cosa sometime after 273 BC. Ancient Roman concrete was a mixture of lime mortar, aggregate, pozzolana, water, and stones, and was stronger than previously-used concretes. The ancient builders placed these ingredients in wooden frames where they hardened and bonded to a facing of stones or (more frequently) bricks. The aggregates used were often much larger than in modern concrete, amounting to rubble.
Francis Petre
Petre's early speciality was his work in mass concrete, at the time a novel building material in New Zealand. Widely used by the ancient Romans the formula for making it was lost and a new one only invented in the 18th century. Three of Petre's earliest projects were all constructed in this material: Judge Chapman's house (today known as "Castlamore"), the clifftop villa nicknamed Cargill's Castle in 1876, and St. Dominic's Priory in 1877. However, according to the whims of his patrons, he did also work with more conventional building materials.