Natural stone has traditionally been used for erecting buildings to sculpting sculptures. This is mainly because of the sustainable and imperishable nature of natural stone. However, nothing lasts forever and natural stone also weatheres. The causes of weathering are very diverse and the weathering processes can be biological, physical and chemical.
The recovery options for weathered stones are at least as diverse. From completely replacing the damaged stone to the minimal restoration of the natural stone. When repairing natural stone, both minor and major repairs, replacement mortars are impossible to imagine without.
Restoration options
During a restoration, major and less invasive repairs may be necessary. We can divide the repairs into 3 types: a complete stone replacement, inserts and mortars. In the case of complete stone replacement and insertion, existing damaged stones are completely or partially replaced by a new stone.
We can classify the stone repair mortars according to the binding agent: this can be a synthetic resin (acrylic, epoxy or polyester) or a mineral.
Resin-bonded mortars are generally not materially compatible (hardness, elasticity, water (vapor) permeability, weathering, etc.) with natural stone. They have a (too) good adhesion, but due to differences in thermal expansion, they can tear off and draw original stone along. For example, polyester resin-based mortars are not frost-resistant; epoxy mortars discolour very strongly. Such mortars are sometimes an option for interior applications such as stair treads.
Among mineral binders, we distinguish mortars based on lime, zinc oxide and cement.
Cement-based mortars have a fast curing; however, they are often too strong, too hard and not flexible compared to the original stone.
Zinc oxide mortars are composed of ground natural stone with zinc oxide and an inorganic binding agent. Their properties are close to those of the commonly occurring natural stones. They have a fast shrink-free curing. They are usually applied with an anchorage.
- RC AMONIT is a zinc oxide mortar composed of ground natural stone (RC AMONIT POWDER) and a mineral binding agent (RC AMONIT LIQUID). Due to the rapid curing, the repair can easily be processed like the original rock. They can be applied quickly to larger thicknesses; many colors are available.
Lime mortars best approach the properties of the stone. This is because they have good bonding strength, water vapor permeability, capillarity, elasticity modulus and water absorption.
There are different types of lime; for this we refer to our article'the benefits of lime in construction'.
Reynchemie offers ST.ONE to, a stone repair mortar based on natural hydraulic lime from Saint-Astier, available in a full color palette and various degrees of hardness.
ST.ONE is easy to apply and edit with traditional tools.
Reynchemistry Lab
Reynchemie has built up years of expertise in choosing the right repair mortar with an adapted color and hardness.
In Belgium and the Netherlands, we find various types of natural stones: bluestone, Tournai, Euville, Gobertange, Balegemse or Ledesteen, Savonnières, Marl, Portland, St.-Maximin,...
For RC Amonit and St. One there is a standard color palette. If no standard color is satisfactory for a certain type of repair, a color analysis can be done in our lab based on a piece of stone.
