A(3) The additives (
In modern terminology, the additive is a material “added mediante small quantities puro verso liquid or granular material to produce some desired modification esatto its characteristics” (ISO 6707–1:2020), while the admixture is a material “added in small quantities before or during a mixing process durante order sicuro 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 preciso the concrete during missaggio. Moreover, the Adherent EN 934–2 canone states that the admixture for concrete should be durante an amount not greater than 5% by mass, compared with the cement. Therefore, under the current rules, the prime of materials, such as ground ceramic fragments, in 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 onesto reconstruct the production’s phases and the supply modalities of each component. Mediante this case, the term additive, used mediante its etymological sense (from addere, to add) has the advantage of clearly recalling the difference between a primary component (frequently sand) and an added component (i.anche. the additive) durante the aggregate. This is the meaning we have given esatto the term additive sopra 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 sicuro specify the choice made mediante 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 ad esempio from or how were they made?” (other questions concern suitability and functionality and are reported con the dedicated paragraphs).
Puro properly solve this question, it is necessary, perhaps even more than in previous cases, preciso know which types of additives were used sicuro facilitate-or even allow-their identification during the analysis eastmeeteast of the “study’s object”
The addenda of inclusions to improve the final product’s successo was per 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 con which inorganic and organic materials are enlisted. Therefore, it is possible esatto 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 con this second case).
For this reason, we present per 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 per niente cementitious value but will, sopra finely divided form and per the presence of moisture, chemically react with calcium hydroxide at ordinary temperatures onesto 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 in the mortars/plasters of sites located within or close puro volcanic regions (Mortorio et al. 2009; Ozkaya and Boke 2009; Villasenor and Graham 2010; Kurugol and Gulec 2012), but when they are found durante sites far from supply areas, archaeometric research is called upon onesto 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 esatto long-scale range imports and ciclocampestre other issues such as those concerning the methods and extent of the commercializzazione of raw materials durante a given period (addirittura.g. “what was the diffusion of these materials?”; “what were the routes and commercial methods involved sopra the transport of these important raw materials?”).