Cocciopesto(OpusSigninum)
Known historically as Opus Signinum. A bio-composite mortar obtained by mixing aerial lime with crushed fired brick. The ground brick acts as a pozzolanic reactant, conferring hydraulic properties on an otherwise fragile binder.
The pozzolanic effect: the amorphous silica in the fired brick reacts with calcium hydroxide to form calcium-silicate-hydrate crystals (C-S-H), enabling the mortar to set even in the presence of water.
Cocciopesto (Opus Signinum) is one of the most brilliant engineering inventions of Roman antiquity. By mixing crushed brick with air lime, the Romans discovered how to create a waterproof yet breathable mortar, able to harden even underwater, long before the invention of modern cement.
Pure air lime, on its own, hardens very slowly by carbonation and is soluble in water. Adding crushed brick fragments changes everything: clay fired at low temperatures (600-800 degrees C) contains silica and alumina in amorphous, reactive form. These minerals react at ambient temperature with calcium hydroxide, forming hydrated calcium silicates and aluminates (C-S-H): the pozzolanic reaction, which confers hydraulic properties and a set that occurs even in the presence of water.
In historic architecture and contemporary bio-construction, cocciopesto is considered the dehumidifying render par excellence. Its macroporous structure works like an intelligent sponge: it absorbs rising capillary damp and allows it to evaporate freely. Unlike cement, mineral salts crystallise harmlessly within the large pores, without causing detachment of the render.
Standards
European and international references applicable.
Physical properties
Usage environment
Not all crushed bricks produce the pozzolanic reaction. Modern industrial bricks fired above 1000 degrees C have vitrified crystalline silica that does not react with lime. Only traditional or artisanally fired brick at low temperatures is effective.
Documented applications
TAV. DDehumidifying plasters
Remediation cycles for historical masonry affected by strong capillary rising damp and soluble salts.
Continuous beaten floors
Poured screed, compacted, ground with pumice and finished with linseed oil. The traditional Battuto Veneziano.
Historical waterproofing
Lining of cisterns, fountains, Roman baths and gutter channels in monumental architecture.
Bio-architecture finishes
Coloured mortars (brick red or yellow ochre) for healthy interiors without chemical pigments.
Compatibility with Capillary Rising Damp (higher bar = more compatible)
TAV. ECocciopesto offers the perfect balance: macroporosity allows salts to crystallise harmlessly in large pores, while its hydraulic nature prevents the binder from dissolving over time in wet environments.
Used in these systems
TAV. SOperational documents from this sheet
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