LESSON 9: STONE DETORIATION PATTERNS GENERAL TERMS

Question 1

modification of the material that does not necessarily imply a worsening of its characteristics from the point of view of conservation. for instance, a reversible coating applied on a stone may be considered

Answer 1

alteration

Question 2

human perception of the loss of value due to decay

Answer 2

damage

Question 3

chemical or physical modification of the intrinsic stone properties leading to loss of value or to impairment of use

Answer 3

decay

Question 4

decline in condition, quality, or functional capacity

Answer 4

degradation

Question 5

process of making or becoming worse or lower in quality, value, character, etc depreciation

Answer 5

deterioration

Question 6

any chemical or mechanical process by which stones exposed to the weather undergo changes in character and deteriorate

Answer 6

weathering

Question 7

individual fissure, clearly visible by the naked eye, resulting from separation of one part from another

Answer 7

crack (fissure)

Question 8

crack subtypes:

Answer 8

1. fracture
2. star crack
3. hair crack
4. craquele

Question 9

may be due to weathering, flaws in the stone, static problems, rusting dowels, too hard repointing mortar. vibrations caused by earth tremors, fire, frost, may also induce cracking

Answer 9

cracking

Question 10

cracking should not be confused by this, which consists of detachment along bedding or schistosity planes, not necessarily oriented vertically.

Answer 10

delamination

Question 11

in this, mechanical overload is not noticeable, transitional to splitting

Answer 11

delamination

Question 12

change in shape without loosing integrity, leading to bending, buckling, or twisting of stone block

Answer 12

deformation

Question 13

this degradation pattern mainly affects crystalline marble slabs (tombstones, marble cladding)

Answer 13

deformation

Question 14

separated, air-filled, raised hemispherical elevations on the gface of stone resulting from the detachment of an outer stone layer. this detachment is not related to stone structure.

Answer 14

blistering

Question 15

in some circumstances, is caused by soluble salts action

Answer 15

blistering

Question 16

local loss of stone surface from internal pressure usually manifesting in the form of an irregularly sided crater

Answer 16

bursting (enclatement)

Question 17

sometimes preceded by star-shaped face fracturing. this deterioration pattern is due to the increase of volume of mineral inclusions (clay, iron minerals, etc.) naturally contained in the stone, and situated near its surface. the corrosion of metallic reinforcing elements may also induce.

Answer 17

bursting

Question 18

not to be confused by the term bursting, this term refers to loss of material due to a mechanical impact, which may have crater shape if the object hitting the stone surface is hard and small (a bullet for instance)

Answer 18

impact damage

Question 19

detachment process affecting laminated stones (most of sedimentary rocks, some metamorphic rocks), it corresponds to a physical separation into one or several layers following stone laminae. the thickness and shape of direction with regards to stone surface

Answer 19

delamination

Question 20

sub-type of delamination; detachment of multiple thin stone layers (cm scale) that are sub-parallel to the stone surface. the layers may bend, twist, in similar way as book pages

Answer 20

exfoliation

Question 21

not to be confused with delamination, it is the kind of detachment totally independent of the stone structure

Answer 21

scaling

Question 22

efflorescence’s and biological colonization can be detected in-between the laminae

Answer 22

delamination

Question 23

detachment of single grains or aggregates of grains

Answer 23

disintegration

Question 24

relationships of distintegration with the substrace:

Answer 24

1. it affects only the surface of the stone or can occur in depth, damage usually starts from the surface of the material
2. on crystalline marble, granular disintegration may reach several centimeters in depth, sometimes more

Question 25

sub-types of disintegration

Answer 25

1. crumbling
2. granular disintegration
3. powdering, chalking
4. sugaring
5. sanding

Question 26

detachment of aggregates of grain from the subtrate. these aggregates are generally limited in size (less than 2cm). this size depends of the nature of stone and its environment

Answer 26

crumbling

Question 27

occurs in granular sedimentary (e.g. sandstone) and granular crystalline (e.g. granite) stones. granular disintegration produces debris referred to as rock meal and can often be seen accumulating at the foot of the wall actively deteriorating.

Answer 27

granular disintegration

Question 28

refers to size or corresponding grains, terms sometimes employed for describing granular disintegration of finely grained stones

Answer 28

powdering, chalking

Question 29

refers to size or corresponding grains, employed mainly for white crytalline marble

Answer 29

sugaring

Question 30

refers to size or corresponding grains, used to describe granular disintegration of sandstone and granite

Answer 30

sanding