A(3) The additives (
Durante modern terminology, the additive is a material “added in small quantities puro verso liquid or granular material preciso produce some desired modification esatto its characteristics” (ISO 6707–1:2020), while the admixture is a material “added per small quantities before or during verso missaggio process con order to modify the characteristics of a mixture”. However, the difference between the two terms lies mainly mediante that the additive is added during the manufacturing of the cement, while the admixture is added esatto the concrete during mixing. Moreover, the Uni EN 934–2 standard states that the admixture for concrete should be mediante an amount not greater than 5% by mass, compared with the cement. Therefore, under the current rules, the addenda of materials, such as ground ceramic fragments, mediante considerable proportions would fall into the category of aggregates and not that of additives.
However, one of the main aims of the archaeometric study on ancient mortars and plasters is preciso reconstruct the production’s phases and the supply modalities of each component. Per this case, the term additive, used in its etymological sense (from addere, preciso add) has the advantage of clearly recalling the difference between verso primary component (frequently sand) and an added component (i.e. the additive) mediante the aggregate. This is the meaning we have given puro the term additive per this article. Still, the explanation provided above accounts for the fact that modern terminology partly overlaps and partly articulates itself differently, based on the contemporary world’s different needs. It follows that, as long as terminological uncertainties persist, it is always good esatto specify the choice made con the description of the results.
Hence, after having accurately characterised the main components (aggregate and binder), the following question concerns the possible presence of additives: “are there any deliberately added materials?”. If yes: “which types of materials were added?” and “where did they quale from or how were they made?” (other questions concern suitability and functionality and are reported durante the dedicated paragraphs).
Esatto properly solve this question, it is necessary, perhaps even more than in previous cases, puro know which types of additives were used to facilitate-or even allow-their identification during the analysis of the “study’s object”
The accessit of inclusions sicuro improve the final product’s performance was verso common practice that frequently left recognisable traces con literary sources and archaeological evidence. Consequently, citable examples are numerous and provide us with an extremely varied picture mediante which inorganic and organic materials are enlisted. Therefore, it is possible puro formulate the characterisation question sopra terms of: “are the additives of an inorganic or organic nature?” (we will see later that there are additional difficulties in this second case).
For this reason, we present verso shortlist of inorganic and organic additives (and admixtures); however, we refer to the other contributions for the necessary insights on their characteristics and properties (Arizzi and Cultrone 2021; Ergenc et al. 2021).
Beginning with inorganic additives, the most common were natural and artificial pozzolans that are defined as “siliceous or siliceous and aluminous materials which per themselves possess little or giammai cementitious value but will, sopra finely divided form and in the presence of moisture, chemically react with calcium hydroxide at ordinary temperatures to form compounds possessing cementitious properties” (Dodson 1990).
Natural pozzolans are volcanic origin materials, such as the volcanic ashes from the region of Pozzuoli from which they take their name (pozzolan s.s.). These are often found per the mortars/plasters of sites located within or close puro volcanic regions (Lagna et al. 2009; Ozkaya and Boke 2009; Villasenor and Graham 2010; Kurugol and Gulec 2012), but when they are found sopra sites far from supply areas, archaeometric research is called upon preciso localise their origin and reconstruct the trade routes that allowed their import and usage. The provenance question may thus remain confined onesto the scale of the site and its territory or expand preciso long-scale range imports and ciclocampestre other issues such as those concerning the methods and extent of the commercializzazione of raw materials sopra verso given period (anche.g. “what was the diffusion of these materials?”; “what were the routes and commercial methods involved durante the transport of these important raw materials?”).