Resistance to sea water
for Saint-Astier® NHL
Due to the very low presence of aluminates and other components (gypsum, alkalis), Saint-Astier® limes are well suited to marine climates.
An extreme test was conducted in our laboratories using seawater instead of distilled water (ISO norms EN 459.2). The mortar was prepared with ISO sands and the current European Norm ratio of >500kg/m3 of binder.
The sea water was simulated by using salt from the Dead Sea (as used in sea water aquariums) at a ratio of 33gr.l-1. The Proctors were cured in the same water for 7, 28 and 90 days.
The lime used was NHL 3.5 and the table below shows results in tensile and compressive strength compared with an identical mortar prepared with distilled water as per EU standards (EN 459-2).
| Curing - Days | Seawater proctors | Standard proctors | ||
|---|---|---|---|---|
|
|
TS |
CS |
TS |
CS |
|
|
N/mm2 |
N/mm2 |
N/mm2 |
N/mm2 |
|
7 |
1.23 |
3.1 |
0.85 |
2.8 |
|
28 |
3.70 |
9.5 |
2.5 |
8.9 |
|
90 |
3.80 |
15.3 |
3.5 |
14.60 |
Note: the high compressive strength obtained is due to the EU norm standard mortar ratio which is close to 1:1.
The performances of the 2 mortars are similar at 90 days but the presence of sodium chloride accelerates the early hardening. None of the following phenomena were noted:
– Lime leaching
– Portlandite reaction due to hydration of C2S that can produce calcium sulphates in the form of expansive Ettringite.
– Possible formation of Brucite.
– Substitution of Tobermorite lime by magnesium, forming friable magnesium silicates.
– Formation of Friedel salt (Calcium Chloro Aluminate)
The study is conducted to check the passive reaction in the presence of sea salt. It does not consider the possible presence of organic matter or other contaminants in the seawater.