Correct grouting is not only important for the appearance, but it also increases the durability of the facade. Several problems, including moisture problems, result from cracks and fissures in the grouting.
The joints of a facade determine the appearance of the building, facade or wall in both new construction and renovation. Besides the different types of grouting, e.g. a flat brushed grout, cut grout, cutting grout... the color of the grout can also be played with. Not only the aesthetic aspect is important when repairing grouting, but also the durability of the grout.
When renovating or restoring historic buildings, it is important to use the right type of grout. This takes into account the moisture load of the facade, the hardness of the stone type used and the composition of the building's mortar mortar used. Buildings prior to WWI were generally built with lime-bonded mortar specimens. This primarily used local lime with different characteristics. To restore these historic buildings, it is best to use compatible lime-bonded mortar specimens.
NHL 5 is a lime binder with high compressive strength (5 MPa at 28 days). It is highly resistant to frost, cures faster and has a higher resistance to crystallization of salts. NHL 5 is therefore ideal where greater hardness and compressive strength are required, such as limestone concrete, masonry mortars, etc. This makes it ideally suited for facade restoration with heavy loads or erected in hard (bricks) in both colder climates and maritime climates. NHL 5 was used in the repairs below sea level of the Mont-Saint-Michel ramparts.
NHL 3.5 is a lime binder for preparing mortars and plasters for both interior and exterior applications with medium compressive strength (3.5 MPa at 28 days). This type of NHL is ideal for masonry and pointing applications in temperate climates with mild winters.
Besides pure natural hydraulic lime, grouting can also be done with colored lime. For this we have a formulated lime product, namely RC Astivo. As a base we take NHL 3.5 and add mineral pigments to obtain the desired color. You can add sand in a ratio of 1:4 to 1:1.5 depending on the type of mortar you want to obtain.
NHL 2 has a low compressive strength (2 MPa at 28 days) and therefore an ideal binder for plasters, but less suitable as a grouting mortar in our moderate sea climate / humid climate. If you still want to grout with an NHL 2, you have to take into account a longer curing time and you have to add more lime to the mortar mortar. All this adds up to a higher cost of the final grout!
Mainly repairs are carried out with NHL 3.5 due to its excellent compressive strength and compatibility with the existing masonry. Standard grouting is done with a ratio of 1 part NHL 3.5 and 2.5 to 3 parts sand. We always recommend working with dune or rhine sand to stay as close to the color of the pigment as possible. For certain applications, such as cutting and cutting joints, it is easier for the grout to be "fatter" than normal. This is achieved by adding less sand and grouting at a ratio of 1 to 1.5.
The table below shows the mixing ratio of lime/sand with the respective curing time and compressive strength.
*EN459-1 (mix ratio 1:1 by volume with ISO 679 sand)
