Basic properties

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Complementarity with lime

Prompt natural cement is the ideal complement to limes. Indeed, a proportion of Prompt natural cement, usually in a minority in relation to lime, brings lime mortars short term strength and limits shrinkage without disrupting the breathability of walls and low modulus of elasticity.

Since the first batches, manufactured at the beginning of the 19th century, Prompt natural cements (PNC) have been mixed with lime in order to accelerate setting.


Maintaining breathability of walls : 
The permeance of hydraulic lime mortar is preserved:

  Total binder in km/m3 of dry sand PNC in kg NHL 3.5 Permeance (PNC-NHL 3.5) in g/m2 .h.mmHg Permeance (NHL 3.5) in g/m2 .h.mmHg
Lean mix concrete 280 70 210 0.92 0.76
Medium mix concrete 340 100 240 0.78 0.73
Fat mix concrete 360 200 160 0.60 0.57

The higher the permeance value, the better the water vapour transfer.
PNC-NHL 3.5 mixes are at least as permeable to water vapour as crack joint control mortars based on NHL 3.5 alone (kept under the best temperature and hygrometry conditions).


Maintaining a low modulus of elasticity: 
Lime–Prompt natural cement mortars are fairly flexible in accommodating changes in surface dimensions. After three months, the modulus of elasticity of lean and medium mix mortars is the same as that of crack control mortars based on NHL 3.5 lime alone.


Prompt natural cement and lime: two natural, complementary materials for high quality, long-lasting work.