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[MIS04-P04] Assessment of the combination of frost and salt solution on limestone durability: application to the Massangis limestones (Burgundy, France)
Keywords:Limestone, aging test, Frost
Change of facies within a quarry can be subtle and yet lead to contrasting behaviors when they are used as building stones. The classic characterizations of materials according to the standards do not always make it possible to highlight their differences and to understand their weathering behavior.
In the Burgundy region, middle of France, a quarry operated by POLYCOR and ROCAMAT provides different facies of oolitic type Jurassic limestones called Massangis. They are used mainly flooring, wall cladding and solid wall. These limestones have similar appearances (shade of color and texture). The various facies are not linked to the stratigraphy but by the color change observed within the different stone banks. Except for their color and according to the standards, these facies show only slight variations of properties. However, they exhibit contrasted behaviors in use, particularly in the case of combination of salt and frost action. In addition, a lower resistance of the light-colored facies pale beige compared to the yellow facies is observed.
The use of standards to assess durability of building stones usually means the measurement of the action of only one factor at a time that is not what occurs on buildings where stones are often submitted to a combination of weathering factors. Thus, some stones that were supposed to resist according to standards, show early degradation when used as building stones which is the case of some facies of Massangis. With the aim to assess the specific properties of each facies and to understand their behaviors to a combination of weathering factors, the 4 quarried facies were characterized by specific intrinsic properties: total porosity with water and pore distribution with mercury porosimetry and study of colored thin sections, transfer properties by capillarity and evaporation. Then stones were subjected to accelerated ageing tests combining the effect of frost and salts. The monitoring of the alteration was carried out by measuring the speed of the acoustic waves.
At the level of the quarry, the 4 facies are identified by the operator according to their color. Two clear facies are defined, the light shaded facies (MALP) from the Malpierre quarry next to the main quarry and the nuanced clear Massangis facies (MCN) from the main quarry called Val d’Arion. The two other facies are the facies corresponding to the yellow Massangis (MJ) and the light beige facies (MBC) composed of a mixture of light and yellow facies.
The clear facies (MALP and MCN) are quite different facies despite their similar aspect. The MALP facies is more porous than the MCN facies (MALP = 14.14% / MCN = 12.70%). However, MALP has a 48H porosity and a saturation coefficient lower than MCN. The MCN facies has an unimodal and microporous network compared to MALP. Its range of pores is homogeneous allowing good circulation of fluids.
The light beige Massangis facies (MBC) has a lower porosity (12.05%), but a high saturation coefficient (82%). The mercury porosimetry study highlighted the presence of fairly heterogeneous distribution of access radii. Within the quarry, this facies corresponds to more or less clear or yellow zones depending on the extraction zone, complicating the identification of the facies type.
Finally, the yellow Massangis (MJ) behaves quite differently from the other facies. This facies has the lowest porosity (10.36%) with a 48H saturation coefficient of 44%. It has a very heterogeneous range of pore access that does not allow good capillary saturation of the stone (26%).
The results of the weathering tests simulating unidirectional freezing of parallelepipedal samples submitted to capillary absorption with water and with salt solutions will allow to assess the behavior of the 4 facies according to their porous network.
In the Burgundy region, middle of France, a quarry operated by POLYCOR and ROCAMAT provides different facies of oolitic type Jurassic limestones called Massangis. They are used mainly flooring, wall cladding and solid wall. These limestones have similar appearances (shade of color and texture). The various facies are not linked to the stratigraphy but by the color change observed within the different stone banks. Except for their color and according to the standards, these facies show only slight variations of properties. However, they exhibit contrasted behaviors in use, particularly in the case of combination of salt and frost action. In addition, a lower resistance of the light-colored facies pale beige compared to the yellow facies is observed.
The use of standards to assess durability of building stones usually means the measurement of the action of only one factor at a time that is not what occurs on buildings where stones are often submitted to a combination of weathering factors. Thus, some stones that were supposed to resist according to standards, show early degradation when used as building stones which is the case of some facies of Massangis. With the aim to assess the specific properties of each facies and to understand their behaviors to a combination of weathering factors, the 4 quarried facies were characterized by specific intrinsic properties: total porosity with water and pore distribution with mercury porosimetry and study of colored thin sections, transfer properties by capillarity and evaporation. Then stones were subjected to accelerated ageing tests combining the effect of frost and salts. The monitoring of the alteration was carried out by measuring the speed of the acoustic waves.
At the level of the quarry, the 4 facies are identified by the operator according to their color. Two clear facies are defined, the light shaded facies (MALP) from the Malpierre quarry next to the main quarry and the nuanced clear Massangis facies (MCN) from the main quarry called Val d’Arion. The two other facies are the facies corresponding to the yellow Massangis (MJ) and the light beige facies (MBC) composed of a mixture of light and yellow facies.
The clear facies (MALP and MCN) are quite different facies despite their similar aspect. The MALP facies is more porous than the MCN facies (MALP = 14.14% / MCN = 12.70%). However, MALP has a 48H porosity and a saturation coefficient lower than MCN. The MCN facies has an unimodal and microporous network compared to MALP. Its range of pores is homogeneous allowing good circulation of fluids.
The light beige Massangis facies (MBC) has a lower porosity (12.05%), but a high saturation coefficient (82%). The mercury porosimetry study highlighted the presence of fairly heterogeneous distribution of access radii. Within the quarry, this facies corresponds to more or less clear or yellow zones depending on the extraction zone, complicating the identification of the facies type.
Finally, the yellow Massangis (MJ) behaves quite differently from the other facies. This facies has the lowest porosity (10.36%) with a 48H saturation coefficient of 44%. It has a very heterogeneous range of pore access that does not allow good capillary saturation of the stone (26%).
The results of the weathering tests simulating unidirectional freezing of parallelepipedal samples submitted to capillary absorption with water and with salt solutions will allow to assess the behavior of the 4 facies according to their porous network.