Quicklime, hydrated lime and natural calcium carbonate

Precipitated calcium carbonate (PCC) chemically can be synthesized in the laboratory. In this study, hydrated lime or calcium hydroxide was used as raw material with sucrose as additive to produce PCC. The process was compared with the one without additive. PCC produced was observed based on morphology, mineral composition and size by using Fesem-Edx and LPSA, respectively. PCC products without additive demonstrated fine and more uniform size of calcite PCC as compared to the one with additive. Nevertheless, the process with additive produced more PCC product than without additive.

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Radiocarbon Dating of Anthropogenic Carbonates: What Is the Benchmark for Sample Selection?

Heritage ◽

10.3390/heritage3040079 ◽

2020 ◽

Vol 3 (4) ◽

pp. 1416-1432

Author(s):

Michael B. Toffolo

Keyword(s):

Calcium Carbonate ◽

Cultural Evolution ◽

Atmospheric Carbon Dioxide ◽

Radiocarbon Dating ◽

Sample Selection ◽

Hydrated Lime ◽

Radiocarbon Dates ◽

Synthetic Materials ◽

Lime Plaster ◽

Definition Of

Anthropogenic carbonates are pyrotechnological products composed of calcium carbonate, and include wood ash, lime plaster/mortar, and hydraulic mortar. These synthetic materials are among the first produced by humans, and greatly influenced their biological and cultural evolution. Therefore, they are an important component of the archeological record that can provide invaluable information about past lifeways. One major aspect that has been long investigated is the possibility of obtaining accurate radiocarbon dates from the pyrogenic calcium carbonate that makes up most of these materials. This is based on the fact that anthropogenic carbonates incorporate atmospheric carbon dioxide upon the carbonation of hydrated lime, and thus bear the radiocarbon signature of the atmosphere at a given point in time. Since plaster, mortar, and ash are highly heterogeneous materials comprising several carbon contaminants, and considering that calcium carbonate is prone to dissolution and recrystallization, accurate dating depends on the effectiveness of protocols aimed at removing contaminants and on the ability to correctly identify a mineral fraction that survived unaltered through time. This article reviews the formation and dissolution processes of pyrogenic calcium carbonate, and mineralogical approaches to the definition of a ‘dateable fraction’ based on its structural properties.

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