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Heritage Science

Table 1 Compressive strength ranges for natural hydraulic lime mortar samples prepared in accordance with the current British Standard (BSI, 2010)

From: Specialist ‘restoration mortars’ for stone elements: a comparison of the physical properties of two stone repair materials

Classification

28 day compressive strength (MPa)

Traditional terminology*

NHL 2

≥2 to ≤7

Feebly hydraulic

NHL 3.5

≥3.5 to ≤10

Moderately hydraulic

NHL 5

≥5 to ≤15

Eminently hydraulic

  1. * Traditional terminology only loosely relates to modern classification. In reality, modern limes are much stronger than those produced historically.
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