When sampling mortars for radiocarbon (14C) dating it is crucial to ensure that the sample has hardened rapidly relative the resolution of the dating method. Soft and porous lime mortars usually fulfill this criterion if the samples are taken from an uncovered surface from less than a few centimeters deep. However, hard, concrete-like mortars may be impermeable for carbon dioxide and even the outermost centimeters may still contain uncarbonated calcium hydroxide. These mortars may harden very slowly and contain carbonate that formed centuries or even millennia after the original building phase, and they can still be alkaline and capture modern 14C, causing younger 14C ages than the actual construction age. Another problem is reactivation of the binder carbonate if it has been partly decarbonated during a fire later on in its history. It will be shown that these young carbonates dissolve rapidly in phosphoric acid and in many cases a reasonable 14C age can be read from 14C profiles in sequential dissolution if the measurements from initially formed carbon dioxide are disregarded. However, if a mortar was made waterproof deliberately by adding crushed or ground tile, as in Roman cocciopesto mortars, it may be very difficult to get a conclusive dating.

中文翻译：

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粘结剂方解石的延迟硬化和再活化，石灰砂浆放射性碳测年的常见问题

当对放射性碳砂浆进行采样时（14C) 测年 确保样品相对于测年方法的分辨率快速硬化是至关重要的。如果样品是从不到几厘米深的裸露表面采集的，则软质多孔石灰砂浆通常符合这一标准。然而，坚硬的混凝土状砂浆可能无法渗透二氧化碳，甚至最外层几厘米仍可能含有未碳酸化的氢氧化钙。这些砂浆可能会非常缓慢地硬化，并且含有在原始建筑阶段之后几个世纪甚至几千年形成的碳酸盐，它们仍然可以是碱性的，并且可以捕捉现代14C、引起年轻化14C 年龄比实际建造年龄。另一个问题是粘合剂碳酸盐的再活化，如果它在其历史后期的火灾中部分脱碳。可以看出，这些年轻的碳酸盐在磷酸中溶解迅速，而且在许多情况下是合理的14C年龄可以从14如果忽略最初形成的二氧化碳的测量值，则连续溶解中的 C 曲线。但是，如果通过添加碎或磨碎的瓷砖故意使砂浆防水，就像在罗马球菌砂浆中一样，则可能很难获得确凿的约会。