Opus Signinum, an old innovation

Opus signinumThe Opus signinum, used in the construction of the Romans for lining of tanks, terraces, thermal environments, flooring, can be defined as the collection of pottery fragments (by terracotta) crushed, from tiles and amphorae, mixed or not with lime and sand.
The oldest citation about the cocciopesto are attributable to Pliny the elder who spoke in composition and use Naturalis Historia (Book XXXV) and Vitruvius who, in the Treaty De Architectura. He prescribes: If in’arena, by river or sea, We will add a third part of matton pesto, and past pel vaglio, become the best lime and strength.
The signs of Pliny and Vitruvius are taken by Leon Battista Alberti in De Re Aedificatoria (Book IV): For any type of application should cover at least three layers of plaster, the first very rough layers must consist entirely of dredged sand and broken brick
The ground or earthen pot crock, the tradition of Vitruvius, It was widely used by the Romans, who knew, using it wisely, the properties of the malte (especially those of finish) remarkable features of waterproof, adhesiveness, membership, water vapour permeability and weightlessness.
This feature was, and is, the direct result of the Pozzolanic behaviour of cocciopesto, that is expressed through the ability to react with the lime light (calcium hydroxide) to form hydraulic compounds with high stability and resistance to water.
The reaction of Opus signinum with lime is basically a classic Pozzolanic reaction, schematized in Figure, Although quite similar to the reaction between lime free and pozzolan, recognized and described by Vitruvius.

This schematic Pozzolanic reaction

cocciopestoreazioneOften identified with the term opus signinum, named after the city of Signa (today's Signs located near Rome where, According to ancient sources, It was invented), actually, the Opus signinum is characterized by chemical and compositional aspects, Although at the time were only insights, While the opus signinum had more linkable projections with static functions resulting from compression in masonry.

A technology of yesterday and today

THE chemical secrets of cocciopesto are hydraulic behavior that makes it able to exert a binding action.
In other words, only the cocciopesto, added to adequate amounts of fine aggregates (arena) , You can develop a form, Although weak, time-hardening.
The hydraulic behaviour takes place also in respect of alloying elements traditional lime which, the hydraulic lime and the most modern cement, through the Pozzolanic reaction which note the transformation of free lime, soluble and unstable, in more stable calcium silicate hydrate, able, inter alia, of seal:  … It cannot dissolve them neither the wave nor any water surge
In other words, Lime also, added with the cocciopesto, becomes hydraulic lime.

In today's buildings, as well as in the building and informed interventions restoration of the existing, the chemical of the cocciopesto valences are often neglected and the material is prescribed and used today, almost exclusively as a coloring agent in mortar that can be, at the same time, coating and finishing.
The modern earthen pot, produced through crushing of soft bricks (that is cooked at a temperature exceeding 850°(C)) and selected in various sizes, may constitute an efficient protective garrison of murari, consistent with the canons of’construction biocompatible today d is particularly suitable for the recovery of building heritage, and historian.
The mortars to cocciopesto, Besides a remarkable durability and resistance, possess interesting characteristics such as
– low permeability to water ’
– balanced and prolonged hardening over time
– improved ability to diffuse vapor
– total absence of unhealthy or harmful components (If properly formulated).

Uses of mortars the cocciopesto

The protective coating, waterproofing and decorative walls and indoor and outdoor flooring, species in historic heritage recovery and/or specialty, today represents the most frequent usage of cocciopesto.
In the floor, the mortars to cocciopesto can be used as an array of weaving Mosaic arranged in various ways or Fragments of white marble or coloured.
From the perspective of terminological and normative, the Opus signinum, properly designed and manufactured, placement can be found in the definition of adding, covered by the standard UNI EN 206-1: Finely divided material used in concrete in order to improve certain properties or to obtain special properties. In this case the cocciopesto can be considered among the additions pozzolaniche or latent hydraulic activity.

taken from a technical announcement of Edward Maloku

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