SPECIAL ISSUE
Weathering behaviour and construction suitability of dimension
stones from the Drei Gleichen area (Thuringia, Germany)
Heidrun Stu¨ck • Siegfried Siegesmund •
Jo¨rg Ru¨drich
Received: 6 January 2011 / Accepted: 22 March 2011 / Published online: 12 May 2011
 The Author(s) 2011. This article is published with open access at Springerlink.com
Abstract The construction suitability of a dimension
stone depends on its weathering properties along with the
petrology and the petrophysical properties. The aim of this
study was to evaluate the suitability of the dimension
stones from the ‘‘Drei Gleichen’’ area for construction and
replacement purposes. In total, six sandstones (Ingersleben,
Wachsenburg, Hindfelden, Seeberg, Ro¨hnberg, Gleichen-
berg; Upper Triassic) as well as two carbonates (Wachs-
enburg sinter; Quaternary, Wandersleben dolomite; Middle
Triassic) were analysed. The results from our laboratory
and on-site studies of the dimension stones show that rocks
from the same stratigraphic layer, like the sandstones from
the upper Triassic, can show major differences in their
petrophysical and weathering properties. These differences
are attributed to their different diagenesis, resulting, e.g. in
varying pore space, water balance and strength properties.
The pore size distribution can be divided into four different
groups based on their occurring maxima and micropore
content. The determined water balance properties as well
as moisture expansion and salt attack depend on these
groups. Next to this, the mineralogical composition sig-
nificantly influences the weathering resistance. Sandstones
with a high content of altered lithoclasts show a high
amount of moisture expansion, low strength and, in con-
sequence, a low weathering resistance against salt attack.
Based on the results of the present study, an evaluation of
construction suitability could be accomplished. From the
analysed sandstones, only the Seebergen sandstone is
suitable for construction purposes due to its good avail-
ability, good strength properties (high compressive and
tensile strength, low softening degree) as well as a low
porosity. Furthermore, the Wachsenburg sandstone also
shows good petrophysical and petrological properties, but
exploitable deposits are too sparse to be of commercial
interest. From the carbonates, the Wachsenburg sinter
shows very suitable rock parameters, but only sparse out-
crops occur, which are not appropriate for mining.
Keywords Dimension stones  Sandstones  Carbonates 
Weathering
Introduction
The construction of castles in the Middle Ages only used
regionally occurring stones and those easily accessible.
One example investigated in this study occurs in the Drei
Gleichen area of Thuringia. Three castles named after their
respective mountaintops were built on sedimentary rocks
(Keuper in age) in the Thuringian Basin (Figs. 1, 2). Due to
their geological situation and environment, the late Triassic
sediments show a wide range of stones with different
petrological and petrophysical properties.
During the Middle Ages, natural building stones were
mined because of their availability and easy handling, less
so according to certain structural and engineering specifi-
cations. Stones were extracted, for example, because of
their hardness for use as foundation stones or for their
workability, especially when stones were used for complex
decorative design purposes. Weathering resistance played a
rather unimportant role. Today, however, to preserve his-
torical cultural assets, the exact weathering behaviour of a
natural building stone has to be defined in terms of struc-
tural and engineering qualifications before being used as a
replacement stone (Siegesmund and Snethlage 2011).
H. Stu¨ck (&)  S. Siegesmund  J. Ru¨drich
Geoscience Centre of the University Go¨ttingen,
Goldschmidtstr.3, 37077 Go¨ttingen, Germany
e-mail: hstueck@gwdg.de
123
Environ Earth Sci (2011) 63:1763–1786
DOI 10.1007/s12665-011-1043-7
Besides the weathering due to thermal expansion, the
moisture expansion as well as salt weathering is especially
important for the deterioration of sandstones, which often
appear in the Drei Gleichen area. Thermal dilation can
occur on every rock and is characterised by a volume
change during changing temperature. The intensity of
thermal dilation depends on the expansion coefficient of
the occurring minerals and also on the arrangement of the
single minerals.
In most cases, many damage phenomena can be attrib-
uted to the volume increase during moisturisation, which is
also known as moisture expansion. The deterioration can
be observed as a multiple decay phenomena. Back-
weathering, related to fabric discontinuities, such as bed-
ding and scaling parallel to the surface, is often observed
and induced by hygric swelling. Individual decay phe-
nomena mostly superimpose on each other, where the
hygric swelling and salt weathering are caused by the
infiltration of deleterious salts from the surrounding mortar.
This results in the multiple flaking and efflorescence of
salts.
The requirements for a replacement stone depend on the
compatibility to the other rocks in the structure and on
the mining situation in the area, if the original state of the
building is to be reconstructed. The present day mining
situation in the Drei Gleichen area for the original stone is
concentrated only on the mining of the Seebergen sand-
stone. The remaining original dimension stones were
mined from historical and closed quarries or borrow pits.
Therefore, during the restoration work the travertine from
Bad Langensalza was also used as a possible restoration
stone.
In the present study, the weathering form and deterio-
ration of eight regionally mined stones (Keuper in age)
from the Thuringia Basin were investigated at the Castle
Gleichen (Gotha, Germany), which is part of the castle
ensemble Drei Gleichen. On a selected part of the castle,
the type of stones used as well as their particular deterio-
ration was mapped and documented. Furthermore, thin
sections were analysed in detail, and pore size distributions
of the surface deterioration were determined. To evaluate
the structural and engineering specifications of the stones
Fig. 1 Overview of the Drei Gleichen area and the buttes consisting of the Ra¨t sandstone. Location of each castle is indicated
Fig. 2 Geological map of the
Thuringia Basin and the
location of the study area
(modified after Puff 1994)
1764 Environ Earth Sci (2011) 63:1763–1786
123
used, the petrological and petrophysical properties as well
as selected weathering mechanisms were investigated and
simulated in the laboratory. The material properties of pore
space, water balance and storage, as well as the strength,
were determined. For investigating the weathering behav-
iour, the thermal dilation, moisture expansion and salt
loading tests were carried out.
Geological context and building stones of the Drei
Gleichen area
The Drei Gleichen area is situated in the Thuringian Basin
(see discussion in Beutler et al. 2010 and Schubert et al.
2010). It extends 10 km between Arnstadt and Mu¨hlberg in
a northwest direction and 3 km in a southwest to northeast
direction (Fig. 2). The outcrops, ranging in age from Lower
Muschelkalk up to the Jurassic (Figs. 3, 4), mainly consist
of Triassic and are also called ‘‘Triassic Land’’. The red-
coloured Middle Keuper is the typical rock type in the area,
which forms ‘‘together with Upper Keuper’’ the tops of the
castle mountains (Wachsenburg, Mu¨hlburg and Gleichen),
along with minor outcrops of the Jurassic (Beutler 1980;
Siegesmund et al. 2010).
Deposits and depositional environments of the Drei
Gleichen area
The sediments of the German Triassic (Figs. 3a, b, 5) were
deposited in the intracontinental German Basin and are
divided into lithostratigraphic subgroups of Buntsandstein
(red beds), Muschelkalk (chalk) and Keuper (shales). The
basin extends from Great Britain to White Russia in a
west–east direction and from the Baltic Sea to Bavaria in a
north–south direction. This middle European classification
is not transferrable to the international classification or the
Fig. 3 a Stratigraphic table of the Triassic as well as the German Triassic. b Stratigraphic table of German Keuper in detail with highlighted
abbreviations (Table 1) of the occurring dimension stones (changed after Deutsche Stratigraphische Kommission 2002)
Environ Earth Sci (2011) 63:1763–1786 1765
123
alpine Triassic, which is classified into lower, middle and
upper Triassic, based on the occurrence of ammonites.
Especially in the Thuringian Basin, the Keuper is classified
into regional and locally limited facies. In Fig. 3a and b,
the geologic timescale of the German Basin of the Triassic
is shown in comparison to the international timescale.
The basin, lying between the 25 and 35 northern lat-
itude, is situated in a semiarid area. It is surrounded in the
north by the Fenno-Scandinavian Shield and in the south
by the Bohemian-Vindelizian Shield where different sedi-
ments were deposited (Beutler 1980; Paul et al. 2008;
Wurster1964). During the Buntsandstein, the German
Basin was surrounded by the Variscan Orogen, which
rapidly eroded due to the arid climate. At the beginning of
the Keuper (Lower Keuper), when the former Muschelkalk
Sea was regressed, numerous rivers flowed into the basin
and deposited large alluvial fans. The transported sediment
was deposited at the border of the numerous deltas. The
still existing sea with the extension of the Muschelkalk
period, eventually flattened out and diminished in size
due to the continued deposition, until the basin totally
closed. During this time, an extended lagoonal landscape
Fig. 4 3-D geologic model of the Drei Gleichen area with the investigated quarries
Table 1 International and German Triassic stratigraphic classification of the investigated sandstones with their mining status
Name Abbr. Stratigraphic designation
of Thuringian Basin
International stratigraphy Quarry or outcrop
Wandersleben dolomite WD Grenzdolomite (ku) 233–235 Ma Ladinium Glory holes around Wandersleben
Ingersleben sandstone IS Lettenkohlenkeuper (ku) *
Erfurt Formation
Quarry Ingersleben, near Erfurt; c.q.
Wachsenburg sandstone WS ‘‘Semionotus sandstone’’/
Wachsenburg (km1)
Norium Strict limited outcrop near Wachsenburg
(1-m thickness/120-m long)
Hindfelden sandstone HS Schilfsandstein (km2) 224,5–226 Ma Karnium Hindfelden near Meiningen; c.q.
Seebergen sandstone SE Ra¨tsandstein (ko) 209–200 MaUpper
Norium-Rhaetium
Multiple quarries Seebergen/Gotha; a.m.
Gleichenberg sandstone GB Outcrop at Gleichenberg
Ro¨hnberg sandstone RO¨ Quarry at Ro¨hnberg near the Castle
Gleichen; c.q.
Wachsenburg sinter WT Holocene (q), calcareous sinter Multiple borrow pits around
Wachsenburg
a.m. active mining, c.q. closed quarry
1766 Environ Earth Sci (2011) 63:1763–1786
123
developed with diverse vegetation. In the transitional per-
iod between the river system and the lagoonal landscape,
local moors arose, which are documented by the brackish-
marine delta sediments of the Lettenkohlenkeuper (Lower
Keuper/Upper Ladinian). Eponymous for this facies is the
locally occurring coal layers (Beutler and Schubert 1987;
Paul et al. 2008; Wurster1964). One sandstone from this
unit was mined near Ingersleben and was used as a com-
mon natural building stone in the region (Table 1; Fig. 5b).
Continued deposition caused further subsidence, so that
a further transgression took place, thus changing the
depositional environment from terrigenous to marine.
Carbonates with a low thickness and low fossil content
developed. One of these horizons is represented by the
Fig. 5 Macroscopic images of the dimension stones occurring at the Drei Gleichen area. Besides the local name, the stratigraphic designation is
also given
Environ Earth Sci (2011) 63:1763–1786 1767
123
‘‘boundary dolomite’’ (Lower Keuper/Lower Ladinian),
which not only includes the bivalves such as Costatoria
goldfussi but also cephalopods. This stone was also used as
a natural building material in the region and was mined
near the town of Wandersleben (Table 1; Fig. 5b).
At the beginning of the Middle Keuper (Upper Ladi-
nian–Lower Carnian), a predominant saline depositional
environment developed, which is called the interior sabkha.
The Middle Keuper begins with the gypsum Keuper, which
is overlain by the delta facies of the Schilfsandstein (Car-
nian *225 Ma). Over the flat shelf that was covered by a
marine silt layer (Wurster 1964), the delta arms meandered
leaving up to 50 m of fine sand in their channels. The
Schilfsandstein was mined as a natural building stone at
Hindfelden (near Meiningen, Fig. 5c). A further exception
in the mainly dominant saline environment is the thin
bedded formation of the Semionotus sandstone at the
Wachsenburg (Fig. 4), which is defined by the presence of
fresh- and brackish water fish fossils. This sandstone of low
thickness was also used as a natural building stone, mainly
for the construction of the three castles (Wachsenburg
sandstone, Table 1).
The youngest facies of the Middle Keuper is the Stein-
mergel Keuper (Norium), which is overlain by the Ra¨t
sandstones (Upper Keuper/Rhaetian). Locally the facies is
also called the Seeberg Formation. These show evidence of
changing depositional environments from low marine to
lacustrine-terrestrial. The sediments represent alternating
beds of fine sands and mudstones (Seidel 2003). The
investigated Rhaetian sandstones form the top of the
mountains, where the castles are located and were used for
their construction. The localities where the Ra¨t sandstones
originate are from (Table 1) the Kammerberg at Seebergen
(type locality, Fig. 5e), and the mountain of Gleichen
(Fig. 5f) and Ro¨hnberg (Fig. 5g). The Seebergen sandstone
is still mined today, whereas the quarry at Ro¨hnberg is
closed and unapproachable, but still visible at a distance.
At Gleichen Mountain, the present mining of the sand-
stones is not observable.
The Upper Keuper was closed over a period of six
million years, ending with a regressive phase and a depo-
sition of limnic mudstones. These were then displaced by
the marine sediments of the Lower Lias (Lower Jurassic).
At Kallenberg and Ro¨hnberg, a complete stratigraphic
sequence from Lias to Dogger (Middle Jurassic) crops out.
With the beginning of the Lower Dogger, the sedimenta-
tion in the Thuringian Basin ended and was interrupted by
a new transgression in the Upper Cretaceous. During the
Tertiary and Quaternary, the area was completely eroded.
The youngest and also the most recently developed sedi-
ments are calcareous sinter (Fig. 5h) and travertines
Holocene in age. They were deposited in the lowest part of
the Drei Gleichen valley, in a lixiviation depression. The
calcareous sinter deposit at Wachsenburg was also used for
construction of the castles.
The castles of Drei Gleichen––construction history
In the present investigation, on-site studies at Castle
Gleichen were accomplished. This castle is part of the
ensemble ‘‘Drei Gleichen’’, consisting of the castles
Mu¨hlburg, Wachsenburg and Gleichen. This ensemble is
architecturally very significant, because the structures span
the architectural periods from Romanticism to the
Renaissance and ending in Historicism. The earliest written
reference to a castle in the State of Thuringia is the Castle
Mu¨hlburg, which was first mentioned in the year 704.
Castle Gleichen attained fame through the legend of the
Earl of Gleichen, who was allowed to have two wives. In
1900, a historically correct construction expanded the size
of Castle Wachsenburg (Hobohm 2010; Hopf 2010).
Castle Gleichen only has one tower, where the stone-
work has been reconstructed within the framework of
specific safety margins. All the other castle buildings are in
ruins. Only a few areas or parts of the castle walls have
been restored over the last several years to ensure their
structural integrity. For reconstructing the walls and castle
buildings, dimension stones from the immediate sur-
roundings were utilised. These consist of travertine, dif-
ferent formations of Ra¨t sandstone, Semionotus sandstone,
Grenzdolomite and limestones. Of special interest are the
types of mortars applied in connection with the natural
building stones used. Gypsum mortars were applied, which
were probably produced from the Heldburg gypsum and
Grenzdolomite (Keuper in age) located in the immediate
area. Other mortars have also been used in the most recent
restoration work and these have led to the development of
strong salt efflorescences in the stones.
On-site studies on dimension stones at Castle Gleichen:
mapping of lithology and decay phenomena
The diverse geology of the Drei Gleichen area is suitable
for the mining of different dimension stones (Fig. 5).
During earlier times, borrow pits as well as quarries were
created for the construction of the Drei Gleichen castles on
the top of the Ra¨t mountains. Based on their petrophysical
properties and their petrogenesis, they also show a very
different weathering behaviour as rocks used for dimension
stones. To determine whether a possible link among the
lithology, petrophysical properties and the weathering
behaviour of natural building stones exists from the Drei
Gleichen area, the rocks were investigated at one of the
castles in the Drei Gleichen area. Since nearly all of the
1768 Environ Earth Sci (2011) 63:1763–1786
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occurring dimension stones of the area are still observable
at the Gleichen Castle, the investigation of the different
weathering shapes was found to be most suitable at this
location. The wall mapped in this study is located in the
inner part of the Romanesque residential building and is
exposed in a west–east direction (Fig. 6).
After mapping the lithology, all the occurring decay
phenomena were classified and divided into categories.
With the help of this decay scheme, a mapping of the
deterioration was undertaken (see Siedel and Sterflinger
2011).
Categories of decay
The appearing decay phenomena were classified into the
categories of displacement, loss of particles and crustal
formation. The occurring phenomena were documented in
a map according to their intensity as primary, secondary
and inferior shapes (Fig. 9).
In contrast to the displacement of particles, the whole
surface was affected by the loss of material. Here, the stone
loss was represented by shapes generated from back-
weathering and relief. The decay phenomenon is a
homogenous loss of material parallel to the surface. Relief
is defined for all decay phenomena, which cause a heter-
ogeneous loss of material parallel to the surface (Fig. 7a,
b). This includes the decay of more resistant areas of the
surrounding material. In addition to the rounding of edges
and angles, alveolar weathering was also documented as
creating relief on the surface (Fig. 7a). The latter is char-
acterised by ellipsoid erosion in the stone.
Detachment includes every change on a rock surface,
which is characterised by the peeling of the rock or when
the material is still in partial contact with the original
Fig. 6 Schematic drawing of the Gleichen Castle with the mapped wall at the Romanesque residential building
Fig. 7 Selected decay phenomena occurring on dimension stones at
the Gleichen Castle. a Alveolar weathering of the Gleichenberg
sandstone, b relief and back-weathering due to the bedding of the
Hindfelden sandstone, c scaling and flaking at the Ro¨hnberg
sandstone and d multilayer flaking of the Gleichenberg sandstone
Environ Earth Sci (2011) 63:1763–1786 1769
123
surface. This also includes sanding, flaking and scaling.
Sanding of the surface means the displacement of milli-
metre-sized particles or smaller. Flaking is the displace-
ment of loose, small centimetre-sized particles, which peel
parallel to the surface (Fig. 7c). Sometimes the displace-
ment occurs in a blister-like manner or as a bulging.
Scaling includes large-scale displacement parallel to the
surface (Fig. 7c). Locally, scales up to 4 cm in thickness
are observable. Furthermore, the flaking and scaling occur
in multiple layers over each other, which is mainly
observable at the edges of the natural building stones
(Fig. 7d). The surface of the scales in general is more
lightly coloured than the original intact rock surface.
All decay phenomena, which show a surface accretion
of material, belong to the category of crustal deformation.
Material accretion is related to visually recognisable
changes of the rock surface, including biological settling,
crusting and efflorescence. The observed crusts reach a
thickness of up to 5 mm.
Mapping of lithology
From the eight occurring natural building stones in the
region, only seven could be observed in the Romanesque
residential building (Fig. 8). Two different construction
phases were also observable by the particular types of
building stones used. In the lower part, almost every
occurring rock type was applied in the construction,
whereas in the upper part only Wachsenburg sinter was
used. Decorating elements were made of the soft and easy
to sculpt sandstone from Hindfelden. Ra¨t sandstones were
used in the lower part of the wall, which originated from
Seebergen, Gleichenberg and partially from Ro¨hnberg.
Wachsenburg sandstone and the Wandersleben dolomite
(Grenzdolomite) were also used. The former was applied
continuously in a thin line 1 m up from the bottom,
whereas the dolomite was only arbitrarily used (Fig. 8).
The Wachsenburg sinters were cut into rectangular forms,
whereas the lower part of the wall was constructed from
Ra¨t sandstones that were uncut.
Mapping of decay phenomena
The appearance of decay phenomena (Fig. 9) depends on
the lithology and the position of the stone within the wall.
For example, the travertine shows just a shallow settling of
microbes, which is characterised by a darkened surface.
The decay is concentrated in the lower part of the wall,
where the various lithologies exhibit the different types of
decay structures. The Hindfelden sandstone, which is
exclusively used for the decorative elements, mainly
exhibits a relief controlled by the bedding. In particular, the
iron-rich zones are untouched by the weathering. Close to
the bottom of the wall (*1 m above the ground), most of
the rocks show crusts, efflorescences and reliefs. The
cumulative crusts and efflorescences observable here were
probably due to permanent moisture penetration by capil-
lary water entering from the bottom. The salts and crust
material most likely originated from the surrounding
mortar. Scaling occurred in the lower part, mainly on the
Seebergen and Wandersleben sandstone. Directly above
the windows, nearly no decay could be observed. However,
at the right and left of the windows, highly decayed Ra¨t
sandstones with alveolar structures were observable. The
Seebergen sandstones often show a previously developed
millimetre-thick iron crust on the surface, which are called
Fig. 8 Lithological map of the
Romanesque residential
building wall
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liesegang rings. Liesegang rings result from a specific
weathering process, caused by the diffusion of iron-rich
solutions and the precipitation into deeper parts of the rock.
They form concentric rings parallel to the surface and are
often linked to joints and cracks.
The isolated and seldom used Wandersleben dolomite is
characterised by the back-weathering of the rock’s compact
and micritic fabric and shows flaking at the rims. Ro¨hnberg
sandstones characteristically exhibit sanding and flaking.
Dimension stones: petrology and fabrics
Understanding the geological setting of sandstones is
necessary, when considering their use as a natural building
stone. The geological setting affects the mineralogical
composition, petrophysical properties and to a certain
degree the weathering behaviour of natural building stones.
The investigation of the mineralogical composition and
fabric was done by polarisation microscopy, scanning
electron microscope and cathodoluminescence. Observa-
tions with the scanning electron microscope can reveal
information about the pore space properties as well as the
crystallisation of new minerals in the pore space, which can
influence the petrophysical and weathering properties.
Cathodoluminescence can uncover information about
diagenetic processes and the types of cement phases pres-
ent (e.g. authigenic quartz), which is critical since it can
influence the strength properties of a stone. Using this
method, different provenance areas of detrital quartz grains
can be determined. In the following section, each of the
sandstones will be described in their stratigraphic order
(Tables 1, 2).
Lower Keuper
The Wandersleben dolomite represents the youngest cycle
in the hanging wall of the Lower Keuper. This horizon
crops out in the northeast and southeast of the Wachsen-
burg Castle (Wandersleben) and shows an approximate
thickness of 2 m. The yellowish-brown, highly porous
dolomite is characterised by its high content of fossils of up
to 8 mm in size. Microscopic analyses show a sparitic re-
crystallisation at the fossil rims. The macroscopically vis-
ible pores, traced by the hollow space of fossils, only show
a weak alignment. Besides the fossil-rich areas, which
mainly show a sparitic fabric, a very compact micritic part
also occurs (Figs. 10, 11a).
The fine-grained, yellowish-grey sandstone from Inger-
sleben is characterised by its well-developed bedding (mm
in thickness) and its accumulation of coaled plant particles
on bedding planes. The stone consists of 60% quartz, 30%
lithoclasts and 10% feldspars. Subordinated mica also
occurs. The pseudomatrix comprises about 20%, with
isolated grains occurring in the matrix. The grain contact is
sometimes elongated, but point contacts are more pre-
valent. Quartz grains are subangular and the rock is well
graded (Figs. 10, 11c).
Middle Keuper
The white-rose, fine-grained and cross-bedded Wachsen-
burg sandstone is partially interstratified with thin coal
layers (Fig. 6c). At the bedding surface, mudcracks can be
found. The sandstone consists of about 75% quartz, 20%
feldspar and 5% lithoclasts. The grain contact is concave–
convex to sutured and the grading is moderate. The quartz
Fig. 9 Mapping of
deterioration at the Romanesque
residential building wall. The
dominant deterioration shapes
are completely filled, the
secondary ones are striped and
the subordinate shapes are
indicated with a letter
Environ Earth Sci (2011) 63:1763–1786 1771
123
grains are, if not surrounded by quartz cement, subangular
to angular. In some areas, the cement is totally composed
of silica and in other parts composed of calcite, which
induces a very low porosity. Furthermore, the feldspars are
mostly altered to clay minerals (Figs. 10, 11e).
Schilf sandstone
The fine-grained, yellowish-brown silty sandstone of
Hindfelden is macroscopically characterised by thin iron
oxide layers and thin layers of coaled organic material on
the bedding plane. The stone is composed of 60% quartz
grains, 25% lithoclasts, 10% feldspar and 5% mica chlorite.
Furthermore, a pseudomatrix comprises 20% of the rock,
which is composed of pelitic lithoclasts. Many clasts are
altered to chlorite and are volcanic in origin. The feldspars
are strongly altered, and the micas are oriented parallel to
the bedding where they developed as kink bands. The
quartz grains are subangular, the grains have point contacts
and the grading is moderate to well (Figs. 10, 12a).
Upper Keuper––Ra¨t sandstones
The Ra¨t sandstones represent a group of mature sandstones,
enriched in quartz grains, and depleted in feldspars and
lithoclasts.
The yellowish, fine-grained sandstone of Seebergen
(Fig. 12c) is characterised by local iron oxide precipita-
tions also known as liesegang rings. The stone is composed
of 95% quartz and 5% feldspar. After the process of quartz
cementation, the quartz grains were coated by iron oxides.
The grains are somewhat rounded to subangular, the grain
contact is concave–convex and the rock is well graded.
The almost white, fine-grained Ra¨t sandstone from
Ro¨hnberg (Fig. 12e) is similar to the adjacent Seebergen
sandstone, which contains no visible bedding. Spots of dark
brown iron precipitations are recognisable. The stone
consists of 90% quartz, 5% lithoclasts and 5% feldspar.
The subangular grains are surrounded by tangential illite
coatings. The grain contact is pointed to elongated, the
grading is very well developed and the quartz grains are,
with exception at the grain contacts, coated by illites.
The light yellow–grey sandstone from the Gleichenberg
(Fig. 12g) is characterised by thin bedding. The sandstone
is composed of 85% quartz, 10% feldspar and 5% litho-
clasts. The grain contacts are almost concave–convex, but
sometimes pointed. The bedding is represented by grain
size and material changes. Some areas are fine grained and
Table 2 Overview of sandstones investigated: compositional data, grain size, roundness, grain contact, sorting as well as classification after
McBride (1963)
Sample Qtz/Fsp/
Lithocl.
(%)
Grain
size max
(mm)
Roundness Grain contact Sorting Classification and comments
Semionotus
sandstone
75/20/5 0.45 Subangular–
angular
Concave–
convex up
to sutured
Well–
moderate
Arkose, strongly altered feldspars, partially calcitic cement,
accretional silica
Hindfelden
sandstone
60/10/30 0.25 Subangular Point Moderate Arkositic litharenite, strongly altered feldspars and micas;
micas trace the bedding, chloritised clasts (volcanic)
Ingersleben
sandstone
60/10/30 0.35 Subangular Point-
elongated
Well Lithic arkose, chlorite: primary and secondary, clay fragments,
strong altered feldspar: sericite, epidote, calcite; locally
hematite, mafic clasts altered to chlorite (blue)
Seebergen
sandstone
95/5/– 0.25 Lightly
rounded–
subangular
Convex–
concave up
to sutured
Well Quartzarenite, lightly goethite overlays of quartz grains
Gleichenberg
sandstone
85/10/5 0.4 Subangular Elongated-
point
Moderate Sublitharenite, bedding represented by grain size and material
changes
Ro¨hnberg
sandstone
90/5/5 0.2 Rounded–
subangular
Point-
elongated
Very
well–
well
Quartzarenite, tangential illite and hematite
Fig. 10 Classification of the investigated sandstones after McBride
(1963); for abbreviations see Table 1
1772 Environ Earth Sci (2011) 63:1763–1786
123
rich in micas and clay, while some other areas are coarser
grained, with lower mica and clay contents.
Quaternary (Holocene)
The yellowish-white Wachsenburg sinter is characterised
by large-scale pores, which reach a size of up to 5 cm in
length. Furthermore, bedding is observable, which is par-
tially formed by completely calcitised plant stripes. In thin
section, the plants and fossils show a sparitic fabric,
whereas the surrounding matrix exhibits a micritic fabric
(Fig. 13a, b). After Dunham (1962), the sinter can be
classified as a wackestone.
Microfabrics of the dimensional stones
Under cathodoluminescence microscope, the Ra¨t sand-
stones show more than one provenance of quartz and
authigenic quartz in different intensity. Seebergen sand-
stones contain quartz grains originating from different
volcanic, metamorphic and magmatic provenances
(Fig. 12d). The authigenic quartz coatings are very com-
mon. Ro¨hnberg sandstone consists of two types of quartz,
magmatic and volcanic. The authigenic quartz content is
very low (Fig. 12f). The quartzes of the Gleichenberg
sandstone originate from volcanic and metamorphic areas.
The authigenic quartz is common, but mostly dissolute
(Fig. 12h). The investigation with the scanning electron
microscope shows that the pore space of the Ra¨t sandstones
developed differently. Pores, lined with illite coatings
(small needles), are observable around the well-sorted
quartz grains in the Ro¨hnberg (Fig. 14e) and Seebergen,
which has little effect on the porosity but reduces the
permeability by blocking the pore throats. Furthermore, a
loose packing or grain contact in the Ro¨hnberg (Fig. 14f)
and Gleichenberg sandstones is observable, which mainly
show point contacts and cubic packing of grains.
Sandstones from Ingersleben and Hindfelden show
authigenic quartz cement, where the occurrence is very rare
in Ingersleben and very prevalent in the Hindfelden sand-
stone (Figs. 11d, 12b). Quartz margins are clearly dis-
solved. The origin of the quartzes and feldspars is different,
and the pink colour of feldspars represents a high alter-
ation. Under the scanning electron microscope, the altered
lithoclasts or pseudomatrix of the Hindfelden and Inger-
sleben sandstones show typical fibrous clay minerals
(Fig. 14b). Furthermore, hexagonal platelets of kaolinite,
which build a network, are observable in the pore spaces of
the Hindfelden sandstone (Fig. 14c).
Dimension stones: petrophysical properties
Next to the petrology and the fabric properties, the size,
distribution and the interconnection of the pore space
mainly affect the weathering resistance of natural building
stones. These properties make them highly relevant for the
water balance in rocks (Fitzner 1988; Fitzner and Snethlage
1982; Putnis et al. 1995; Putnis and Mauthe 2000;
Siegesmund and Du¨rrast 2011). Thus, to characterise the
structural and engineering qualifications of natural building
stones, it is necessary to analyse the pore space properties
and its influence on the water transport and retention
properties. A further important parameter of a building
Fig. 11 Thin sections and cathodoluminescence (CL) images of (a, b) Wanderleben dolomite in thin section, (c, d) thin section and CL-picture
of the Ingersleben sandstone and (e, f) thin section and CL-picture of the Wachsenburg sandstone
Environ Earth Sci (2011) 63:1763–1786 1773
123
stone represents its strength. This parameter is also strongly
controlled by the pore space properties (Ruedrich et al.
2010a, b).
To determine the directional dependence of the petro-
physical properties, investigations were carried out on
specimens from two mutually perpendicular directions
parallel (X-direction) and perpendicular (Z-direction) to
the bedding. If the specimens did not show any
macroscopically visible fabric elements, an arbitrary
coordinate system was defined.
Porosity, density and pore size distribution
The porosity and density were determined according to the
DIN 52102 (1988). The investigations were carried out on
cubic samples with 65 mm edge lengths. For that purpose,
Fig. 12 Thin sections and cathodoluminescence images of (a, b) Hindfelden sandstone, (c, d) Seebergen sandstone, (e, f) Ro¨hnberg sandstone
and (g, h) the Gleichenberg sandstone
1774 Environ Earth Sci (2011) 63:1763–1786
123
the dry, hydrostatic and water-saturated mass was mea-
sured. The dry mass was determined after 2 days of pre-
conditioning the samples at 20C and 15% relative
humidity. The hydrostatic and the saturated mass were
detected after water saturation under vacuum.
The porosities of the investigated rocks vary between
8.7 vol.% and 27.7 vol.% (Tables 3, 4). This range can
be divided into three different porosity classes, low
(\10 vol.%), medium (10–20 vol.%) and high ([30 vol.%).
The Wachsenburg sandstone shows the lowest porosity with
8.7 vol.%. Medium porosities are exhibited by the samples
from Seebergen (15.80 vol.%) and the Wachsenburg sinter
(16.45 vol.%). All other samples are characterised by a high
porosity ranging from 20.08 to 26.75 vol.%.
From the sample masses used for the porosity, the matrix
and bulk densities were also calculated (cf. Ruedrich
2010b). The matrix densities were controlled by the rock
forming minerals. The sandstones generally show a low
matrix density between 2.65 and 2.67 g/cm3. This correlates
with the mineral densities of quartz and feldspar. The
Wandersleben dolomites are characterised by a value of
2.88 g/cm3. The density of the dolomite single crystal is
2.87 g/cm3 (Tro¨ger 1967), and thus the sample from Wan-
dersleben represents a more or less pure dolomitic rock. In
contrast, the Wachsenburg sinter has a matrix density of
2.64 g/cm3, which is markedly lower than the density of the
calcite single crystal (2.72 g/cm3). This can be traced back
to inclusions of material with a lower matrix density. The
Fig. 13 Macroscopic and microscopic images showing the fabric and microstructures of the Wachsenburg sinter
Fig. 14 Scanning electron microscope images of the investigated
samples. a Layers of illite over quartz grains in the Ingersleben
sandstone. b The highlighted area marks an altered lithoclast in the
Ingersleben sandstone. c Network of kaolinite platelets in the
Hindfelden sandstone. d Idiomorphic calcite as well as hexagonal
kaolinite platelets in the Semionotus sandstone. e Illite needles above
a quartz grain in the Ro¨hnberg sandstone. f Overview of the well-
sorted Ro¨hnberg sandstone with its loose packing
Environ Earth Sci (2011) 63:1763–1786 1775
123
bulk densities of the investigated rocks show a variation
between 1.92 g/cm3 for the Ingersleben and 2.42 g/cm3 for
the Wachsenburg sandstone. The bulk density was mainly
controlled by two parameters: (1) the density of the involved
minerals and (2) the porosity of the rock (Table 3).
To determine the pore size distribution of the samples,
mercury porosimetry was applied (van Brakel et al. 1981).
The investigations were carried out with pressures up to
2 kbar, which allows the evaluation of pore radii of about
0.005 lm. Cylindrical specimens ([ 12.5 9 20.0 mm)
were analysed. The pore size distribution shows a large
variation. These different patterns can be divided into four
types (Figs. 15, 16): (1) unimodal with one maximum in
the range of macropores and a micropore content of\20%
(Wandersleben dolomite, Ingersleben, Gleichenberg sand-
stone), (2) unequal unimodal with one maximum in the
range of capillary pores and micropore content between 15
and 30% (Wachsenburg sandstone), (3) unequal bimodal
with a high micropore content of 35–45% (Hindfelden
sandstone) and (4) unequal unimodal with one maximum in
the range of macropores and a micropore content between
5 and 10% (Seebergen, Ro¨hnberg sandstone). The calcar-
eous sinter covers a wide range of pore sizes with no sig-
nificant maximum. The average pore radius of the
investigated rocks can be subdivided into: small (0–1 lm),
medium (1–2 lm) and high (2–5 lm). The medium pore
radius varies from 0.24 lm for the Hindfelden sandstone
up to 6.87 lm for the Wandersleben dolomite (Table 3).
Table 4 Water transport properties (capillary and hygroscopic water uptake, maximum degree of saturation, water vapour diffusion coefficient)
as well as tensile and compressive strength of the specimens
Direct. Wandersleben
dolomite
Ingersleben
sandstone
Wachsenburg
sandstone
Hindfelden
sandstone
Seebergen
sandstone
Gleichenberg
sandstone
Ro¨hnberg
sandstone
Wachsenburg
sinter
Porosity (vol.%) – 23.73 27.71 8.71 22.07 15.80 21.87 22.40 16.45
Matrix density
(g/cm3)
– 2.88 2.66 2.65 2.66 2.67 2.66 2.65 2.64
Bulk density
(g/cm3)
– 2.20 1.92 2.42 2.07 2.25 2.08 2.05 2.21
w value
(kg/m2 h1/2)
X 18.56 20.05 0.75 8.50 4.17 11.85 7.50 0.81
Z 18.94 24.21 0.98 9.98 4.90 10.03 8.01 –
l value – 10.08 5.20 39.90 10.88 22.72 5.80 6.70 18.25
Sorption (%) – 0.18 1.43 0.40 3.00 0.16 0.50 1.50 0.23
S value – 0.57 0.76 0.55 0.80 0.43 0.62 0.54 0.58
Tensile strength
(N/mm2)
X 2.37 1.03 6.04 1.12 5.5 2.99 1.54 2.94
Z 2.76 1.43 6.57 1.89 6.01 3.91 1.58 3.01
Compressive
strength/dry
(N/mm2)
X 40.07 15.21 102.14 21.55 100.82 41.54 34.03 55.34
Z 42.63 19.59 124.41 25.68 113.07 46.07 31.64 57.08
Compressive
strength/wet
(N/mm2)
X 34.89 7.98 93.75 9.81 87.67 30.48 25.46 47.56
Z 35.12 11.57 114.69 13.45 101.57 34.50 28.54 41.14
Table 3 Pore size distributions and medium pore radius
Pore class (lm) Micropores 0.1–1 1–10 10–100 Medium pore radius (lm)
0.001–0.01 0.01–0.1
Wandersleben dolomite 0.00 0.00 0.00 71.60 28.40 6.87
Ingersleben sandstone 5.83 11.34 13.27 34.96 34.60 1.78
Wachsenburg sandstone 2.80 12.58 56.48 22.47 5.67 0.52
Hindfelden sandstone 13.01 24.75 23.59 38.64 0.00 0.24
Seebergen sandstone 2.05 4.94 9.86 77.82 5.33 2.64
Gleichenberg sandstone 0.00 2.72 8.45 82.88 5.95 4.42
Ro¨hnberg sandstone 1.43 7.39 11.83 75.65 3.70 1.58
Wachsenburg sinter 20.10 21.44 12.50 25.43 20.52 0.37
The most occupied pore size given in bold
1776 Environ Earth Sci (2011) 63:1763–1786
123
Water transport and retention properties
The water transport and retention properties of a porous
natural building stone considerably affect the weathering
behaviour. The water balance of rocks were normally
described by the parameters of capillary water uptake,
sorption and desorption, degree of saturation and water
vapour diffusion.
The capillary water uptake was measured according to
DIN 52103 (1988) with an underfloor balance, parallel and
perpendicular to the bedding. The measurements were
performed on sample cubes (65 9 65 9 65 mm), which
were dipped 5 mm in water. The weight increase was
digitally measured every 20 s. The capillary water uptake
can be expressed by the water absorption coefficient
(w value, Table 4), which represents the absorbed water
amount in dependence to area and time (kg/(m2 Hh)). The
investigated samples show a wide range of w values from
0.75 kg/(m2 Hh) for the Wachsenburg sandstone up to
20.05 kg/(m2 Hh) for the Ingersleben sandstone. The
highest w values are exhibited by the sandstones from
Hindfelden, Ingersleben and the Wandersleben dolomite,
followed by the three Rhaetian sandstones, Ro¨hnberg,
Seebergen and Gleichenberg. Low to very low w values
were detected for the Wachsenburg sandstone and the
Wachsenburg sinter. In the case of the sandstones, the
w values show a pronounced directional dependence.
Generally, the highest w values occur parallel to bedding.
The reason for this anisotropy is in most cases a grain-
shape preferred orientation, which is typical for sandstones
(Ruedrich et al. 2010a). In the case of the two carbonates
(Wachsenburg sinter and Wandersleben dolomite), the
anisotropy is only marginally developed. However, in the
Wandersleben dolomite, this can be explained by the small
interstitial fossils, which are not aligned parallel to the
bedding.
The sorption/desorption was measured in a climate
chamber during a stepwise increase of moisturisation
between 15 and 95% relative humidity. Following the
relative humidity, a stepwise decrease was performed until
the air humidity reached the initial state of 15%. Every
humidity stage was held for 24 h. After equilibration the
mass of the samples were weighed. Sorption characterises
the hygroscopic water uptake and is a degree for the
adsorption of water at the internal surfaces of a rock. The
stepwise (10%) increase and decrease of relative air
humidity shows the same progress in all the samples, but
the intensity is different (Fig. 17). Between 15 and 80%
relative humidity, the sandstones show a more or less linear
weight increase. Above 80% relative humidity, a surge in
weight of the samples occurs. The largest increase is
exhibited by the sandstones from Hindfelden and
Fig. 15 Diagrams depicting the
pore size distributions in four
distinct groups. The average
pore radius is marked by the
dashed red line. The amount of
micropores is also given for
each group
Environ Earth Sci (2011) 63:1763–1786 1777
123
Ingersleben. All the other samples show with one percent
maximal weight increase (at 95%) a very low hygroscopic
water uptake (Table 4).
The degree of saturation depends on the pore sizes and
the interconnection of the pores. The presence of cements
can clearly affect the permeability of sandstones. The
degree of saturation covers a range from 0.43 for the Ra¨t
sandstone of Seebergen to 0.8 for the silty sandstone of
Hindfelden (Table 4).
The water vapour diffusion coefficient was determined
with the ‘‘wet-cup’’ method according to DIN 52615
(1987) and was carried out on disc-shaped samples
(40 9 10 mm). The rim of the specimens were sealed up
with an adhesive strip and closed over a Teflon fryer. The
measurement was accomplished at 20C and 50% relative
humidity in a climate chamber. The change in weight of the
water filled Teflon cup was measured in 24-h intervals.
The water vapour diffusion (l value) is a measure of the
vapour diffusion through the rock and is mainly controlled
by the pore size distribution (Ruedrich et al. 2010a). The
non-dimensional l values vary from 9 to 49 (Table 4),
which indicates only slight differences between the rocks.
Tensile and compressive strength
Strength properties such as tensile strength and compres-
sive strength are important rock parameters, which also
influence the weathering behaviour of dimension stones.
Fig. 16 Pore size distributions
in the investigated sandstones.
The red letters represent the
previously explained groups of
pore size distribution
1778 Environ Earth Sci (2011) 63:1763–1786
123
The cause for this is that stresses induced by mechanical
weathering processes have to exceed the strength of a
material before a failure occurs. Thus, the strength prop-
erties are a measure for the grain fabric cohesion. Impor-
tant fabric parameters for the tensile strength are the grain
size, the shape of the grain contacts and a preferred grain
boundary orientation. However, of most significance is the
type and intensity of cementation.
To obtain the values of tensile strength, measurements
were made using the Brazil test according to DIN 22024
(1989). The investigations were performed on disc-shaped
specimens (40 9 20 mm). By loading the discs in parallel
lying surface lines, a tensile strength is induced in the
sample perpendicular to the applied pressure. The tensile
strength of the sandstones ranges from 1.23 MPa to
6.64 N/mm2 (Table 4). The Wachsenburg and the See-
bergen sandstones show high values of 6.24 and 6.63 N/
mm2, whereas Hindfelden, Ingersleben and Ro¨hnberg only
exhibit low tensile strength values up to 2 MPa. The
remaining samples show a medium strength. The anisot-
ropy of all the rocks is not very well pronounced.
The uniaxial compressive strength was measured on
cylindrical samples (50 9 50 mm) with coplanar end faces
(accuracy of 0.1%) in the dry and water-saturated state.
The load was applied to the end faces of the specimen with
a strain rate of 1,000 N/s until failure. The compressive
strength varied between 16.97 and 113.27 N/mm2
(Table 3). The highest compressive strength in the dry
sample state was exhibited by the Wachsenburg sandstone,
followed by the Rhaetian sandstones. The compressive
strength in the water-saturated state ranged from 7.98 N/
mm2 for sandstone Ingersleben and 93.75 N/mm2 for
Wachsenburg sandstone (parallel to bedding/Table 4).
Laboratory weathering tests
The dimension stones show in a natural environment a
manifold deterioration (see Chapter 4). Several weathering
mechanisms are assumed to be responsible for the actual
state of the rocks. In general, the weathering can be divided
into chemical, physical and biological processes, whereby
the single mechanisms overlap each other and lead to
multifarious deterioration.
To determine and evaluate the weathering behaviour of
the dimension stones from the Drei Gleichen area, thermal
dilatation, moisture expansion and salt weathering were
simulated and accomplished in the laboratory.
Thermal dilation
During changes in temperature, all rocks show a change in
volume, which results from the increasing movement of the
atoms of minerals during heat input. Natural building
stones are exposed to continuous temperature fluctuations
during the cycles of day and night. Thermal dilation was
measured by heating the samples from 20 to 90C followed
by a cooling down to 20C. The length change was
detected by an incremental displacement transducer with
an accuracy of 1 lm.
All the samples are characterised by an expansion with
increasing temperature and during cooling a contraction
(Fig. 18). The path of the curves proceeds differently:
Some samples, such as Seebergen and Semionotus, show a
more or less linear progression, whereas other samples
show a distinct departure from this linear path. During
heating at temperatures ranging between 55 and 85C,
some of the curves clearly show a flattening. This is
Fig. 17 Sorption/desorption in
dependence to relative air
humidity of a Ingersleben
sandstone, b Hindfelden
sandstone, c Seebergen
sandstone and d Ro¨hnberg
sandstone. Red line adsorption,
blue line desorption
Environ Earth Sci (2011) 63:1763–1786 1779
123
especially the case for the Hindfelden sandstone, which
does not show a linear progression. When reaching a
temperature of 55C, the path runs parallel to the abscissa.
Furthermore, at reaching the initial temperature of 20C,
some samples show shrinkage, but different intensities
occur based on rock types.
The intensity of thermal dilation mainly depends on
the types of minerals present and can be expressed by the
thermal expansion coefficient (Table 5). The coefficients
of the investigated sandstones are very similar, with the
exception of the sandstones from Ingersleben and Hind-
felden. The mineralogical composition affects the thermal
dilation, especially swellable clay minerals, and at least
altered lithoclasts and pseudomatrix, enriched in swella-
ble clay minerals. All the four sandstones mentioned
above have a high content of altered lithoclasts or
pseudomatrix, which also show a departure from the
linear progression.
All the samples investigated exhibit an anisotropy,
which is very well pronounced in the case of the altered
lithoclasts in the stones of Hindfelden and Ingersleben
sandstone. The contraction during heating, resulting from
clay mineral shrinkage, strongly depends on the kind of
clay mineral present. The shrinkage intensity is well pro-
nounced in the case of the Ingersleben and Hindfelden
sandstones. These all contain a high amount of altered
clay-rich lithoclasts.
Moisture expansion
In many cases, moisture expansion is held responsible for
the damages visible in rocks. The swelling and shrinking
during changing moisturisation can induce stresses within
the rock fabric. In the course of time, this leads to a
breaking up of the grain cohesion. Moisture expansion can
occur for almost every type of rock (Weiss et al. 2004,
Ruedrich et al. 2010a, Siegesmund and Du¨rrast 2011).
However, porous rocks with certain clay mineral content
like sandstones show pronounced moisture expansion
wetting. Pore spaces with a high content of micropores, in
combination with clay minerals (partly swellable) at least
in the lithoclasts, is probably responsible for the intensity
of this weathering process (Ruedrich et al. 2010a).
In the present study, moisture expansion was measured
under water-saturated conditions (hydric wetting). The
investigations were carried out on cylindrical samples
(100 9 15 mm). A preconditioning of the specimens was
achieved by drying in a climatic chamber at 20C and 15%
relative humidity. The final resolution of the displacement
transducers was better than 0.5 lm.
The measured swelling during water absorption of the
rocks varies from 0.015 mm/m for the Wachsenburg sinter
to 5.2 mm/m for the Hindfelden sandstone (both measured
parallel to the Z-direction, Table 6). In general, quartz-rich
rocks like the Ra¨t sandstones show only slight moisture
expansion, whereas rocks with a high content of altered
lithoclasts like the Hindfelden and Ingersleben sandstones
are characterised by large values of moisture expansion.
All investigated rocks show a directional dependence of
moisture expansion. The expansion perpendicular to the
Table 5 Thermal expansion coefficients and shrinkage (mm/m) after
measuring
X-direction Z-direction Shrinkage
(mm/m)
Thermal expansion coefficient a (K-1)
Wandersleben dolomite 8.04865E-06 8.013462-06 –
Ingersleben sandstone 9.0391E-06 7.9079E-06 0.08
Wachsenburg sandstone 9.9448E-06 1.00715E-05 0.02
Hindfelden sandstone 2.7675E-06 5.418E-06 0.35
Seebergen sandstone 1.1658E-05 1.183E-05 0.01
Ro¨hnberg sandstone 1.1481E-05 1.1935E-05 0.02
Gleichenberg sandstone 1.15379E-05 1.19331E-05 0.02
Wachsenburg sinter 8.46775E-06 8.127656-06 –
Fig. 18 Length change (mm/m)
of samples investigated
dependent on the temperature
1780 Environ Earth Sci (2011) 63:1763–1786
123
bedding is in general more pronounced than parallel to the
bedding. Sandstones with a distinct bedding show a well-
pronounced anisotropy, such as the rocks from Gleichen-
berg, Ingersleben, Hindfelden and also Wachsenburg.
Salt attack test
In order to determine the weathering resistance of the
investigated samples against crystallisation of salt within
the pore space, salt attack tests were performed according
to the German VDI 3797. Cubic samples (65 mm edge
length) were saturated with a solution of 10% NaSO4 at
different cycles. After 6 h of saturation the samples were
dried at 60C for 16 h. Afterwards, the samples were
weighed and the macroscopic damages were photographi-
cally documented. The experiment was completed after a
maximum of 15 cycles. The sample weights as well as the
surface consistency of all the rocks were changed by the
salt attack test. All samples show after the first test cycle a
slight weight increase. This can be traced back to crystal-
lisation of salt within the pore spaces of the rocks without
damaging effect. For the following cycles a rock specific
weight decrease is observable. This is strong for the
Ingersleben sandstone and very slight for the Wachsenburg
sinter (Fig. 19).
The decay phenomena observed are different in shape
and intensity, and are also specific for each rock. For the
Ro¨hnberg and Ingersleben sandstone a first loss of material
is observable after the third test cycle. The visible decay
phenomena are sanding at the edges, which lead to a
rounding of the samples. Furthermore, a crack formation is
detectable for the rocks from Ro¨hnberg. In contrast, the
Ingersleben sandstone shows a higher variation in the type
of decay, besides sanding and rounding, scaling, flaking as
well as back-weathering of iron-rich areas occur. The
Hindfelden sandstone as well as the Wandersleben dolo-
mite reached a 10% loss of material after five to six cycles.
Therefore, the Hindfelden sandstone exhibits a similar
decay pattern as the Ingersleben rock. For the Wandersle-
ben dolomite, a back-weathering of the fine-grained, mi-
critic and fossil-rich areas are observable. After ten cycles,
the Hindfelden and Ingersleben sandstones as well as the
Wandersleben dolomite show a highly rounded and glob-
ular shape. In contrast, the Seebergen sandstone exhibits a
better salt attack resistance. The rock only shows slight
sanding and rounding. The Wachsenburg sinter shows the
best weathering resistance within the test. After reaching
the 15th cycle, the sample exhibits more or less no loss of
material. Also, no decay phenomena are observable.
Discussion and summary
The geology of the Drei Gleichen area is dominated by
sediments of the Late Triassic age. This sedimentary
sequence is characterised by a high diversity of different
rock types, where some of the rocks are also suitable for
use as dimension stones. Of lesser importance are the
younger rocks (Quaternary in age), which mainly occur as
exposed outcrops in the floodplain. Regionally quarried
Fig. 19 Salt weathering test: damage phenomena of the samples on the left and diagram of the weight change with each cycle
Table 6 Moisture expansion at water saturation (mm/m)
Sample X-direction Y-direction Z-direction
Moisture expansion (mm/m)
Wandersleben dolomite 0.175 0.180 0.190
Ingersleben sandstone 0.500 0.290 1.800
Wachsenburg sandstone 0.120 0.050 0.130
Hindfelden sandstone 2.400 1.800 5.200
Seebergen sandstone 0.010 – 0.020
Gleichenberg sandstone 0.110 0.080 0.470
Ro¨hnberg sandstone 0.130 0.090 0.190
Wachsenburg sinter 0.016 0.015 0.015
Environ Earth Sci (2011) 63:1763–1786 1781
123
rocks were used for the construction of the three castles in
the Drei Gleichen area. Eight different building stones were
mined, six sandstones (Late Triassic) as well as two car-
bonates (Late Triassic and Quaternary).
The field observations as well as the laboratory experi-
ments indicate that there are strong differences between the
various rock types in respect to their suitability for con-
struction. This is the result of their respective depositional
environment and geological history, which lead to strong
variations in the fabric and their petrophysical properties.
The investigations have shown that the deterioration of the
rocks was mainly controlled by physical weathering pro-
cesses such as salt crystallisation and moisture expansion.
In these processes water transport and retention properties
of the rocks play an important role, which are also con-
trolled by the rock fabric and the pore space properties.
Relationship between petrology and pore space
properties
In general, the porosity of sandstone depends on its dia-
genesis, where the controlling factors are compaction,
cementation or dissolution. However, the (primary) pore
size distribution is controlled by the sorting of the sand-
stone (Fu¨chtbauer 1988; Tucker 2001).
The porosity evolution of the six sandstones investigated
in this study and their pore size distribution can be clas-
sified into mature and immature rocks. The maturity can be
divided into compositional and textural sediments. Textural
immature sediments are those with poor sorting and
angular grains; mature sediments are those with moderate
to good sorting and subrounded to rounded grains. The
compositional maturity is characterised by the content of
stable grains such as quartz in proportion to labile grains
consisting of lithoclasts and feldspars (Pettijohn 1975; Folk
1974; Tucker 2001).
The Seebergen, Gleichenberg and Wachsenburg sand-
stones represent quartz-arenites to subarkoses (Fig. 11;
Table 2) and are characterised by a pronounced textural
and compositional maturity. However, the compaction and
cementation leads to differences in the porosities. Whereas
the Seebergen sandstone exhibits a clearly reduced primary
porosity by compaction and quartz cementation, the
Ro¨hnberg sandstone shows a low compaction with
accompanying point contacts between the grains. More-
over, the well sorting causes a narrow spaced maximum of
capillary pores in the pore size distribution of the Seeber-
gen and Gleichenberg sandstones (Fig. 16f; Table 2). The
pore size distribution of the Ro¨hnberg sandstone differs
from the other two sandstones. In this case the presence of
quartz enclosed by illite coatings also generates smaller
pores. The Wachsenburg sandstone exhibits a higher con-
tent of feldspar and is poorly sorted. The low porosity was
generated by compaction, which is evidenced by numerous
pressure solution phenomena and syntaxial quartz growth
fringes. Another diagenetic phase of calcite cementation
further reduced the porosity. Although all three sandstones
form the top of the Rhaetian Hills in the Drei Gleichen
area, they show a very different porosity evolution with an
accompanying different material behaviour (see explana-
tion below).
The sandstones from Hindfelden and Ingersleben are
litharenite in composition (Fig. 11) and originated in a
fluvial environment. They are compositionally immature
(Table 2); however, they are moderately to well sorted. In
both sandstones, all quartz grains show overgrowths
(Figs. 11d, 12b). Furthermore, alteration and partial
replacement of feldspar and lithic clasts are accompanied
by the formation of new clay minerals. The replacement
increases the volume making up the interstitial matrix,
which affects the homogeneity appreciably and gives rise
to a greywacke-type of fabric (Tucker 2001). The clay does
not retain its shape, but becomes squeezed between more
rigid grains. Simultaneously, the porosity increases by the
dissolution or replacement of unstable grains. Generally,
the alteration from original stable grains or lithoclasts goes
along with an increase of smaller pores between the newly
generated networks of clay minerals. In the case of the
Hindfelden sandstone, the volume of micropores is higher
than in the sandstone of Ingersleben (Fig. 16c, d).
The porosity development in the two carbonates is due to
their different origin in contrast to the sandstones, since
delivery coincides with deposit area. Carbonates that
develop in shallow water form metastable calcite dur-
ing deposition and undergo phase transition to stable calcite
or dolomite during diagenesis. During the process of dia-
genesis, grain size can either increase (sparitic growth) or
decrease (micritisation), as well as the pore space can
increase (solution) and decrease (cementation, compaction).
The porosity in the Wandersleben dolomite depends on
its genesis and the fossil content, which influences the
development of a primary or secondary porosity. The
dolomite is generally altered by a secondary process from
calcite to dolomite. Since dolomite has a higher density
than calcite, vugs or cavities are common for dolomites and
creates an increase in the porosity. In contrast, the porosity
decreases when calcite is recrystallised and forms a sparitic
calcite cement around the fossils. Moreover, when abun-
dant fossils are present large-scale pore spaces are gener-
ated, whereas the micritic fabric does not allow the
development of micropores. Therefore, the dolomite shows
a unimodal pore size distribution with a large average pore
size (Fig. 16a).
The porosity development of the Holocene non-com-
pacted Wachsenburg sinter mainly depends on the calcified
plant particles incorporated into the rock during its
1782 Environ Earth Sci (2011) 63:1763–1786
123
formation. Since the plant particles show a size of up to
several centimetres in length, the stones are characterised
by a well-developed pore space network (Fig. 13b). The
remaining material consists of micritic calcite, which does
not allow for the development of many micropores.
Relationship between pore space, water balance
and strength
The pore space and its properties significantly affects the
weathering resistance of a natural building stone, since the
pore space coevally rules the water balance (Fitzner 1988;
Fitzner and Snethlage 1982; Putnis et al. 1995; Putnis and
Mauthe 2000; Ruedrich et al. 2010a). Therefore, properties
such as capillary water uptake, water vapour diffusion and
saturation degree correlate in the present study with the
porosities of the rocks. However, the pore size distribution
and the network of single pore sizes among each other
defines the intensity of the water uptake (Ruedrich and
Siegesmund 2006; Siegesmund and Du¨rrast 2011) and at
least the weathering resistance of sandstones (Fitzner and
Snethlage 1982).
The ability of the rocks for capillary water uptake
strongly depends on the porosity as well as on (the group
of) pore size distributions. In general, the higher the
water uptake, the higher is the porosity (Fig. 20a). The
Wachsenburg sinter does not fit this trend. The large pores
of the Wachsenburg sinter cannot connect, and thereby
create a network between the few occurring capillary pores.
The Wachsenburg sandstone with a pore size distribution,
belonging to group ii (Fig. 15) and showing a unimodal
distribution with a maximum in capillary pores, exhibits a
very low w value. A medium water uptake can be seen in
the sample from groups iii (weak bimodal distribution;
Hindfelden sandstone) and iv (weak unimodal distribution;
Seebergen and Ro¨hnberg sandstone) (Figs. 15, 16). The
samples with the highest w values belong to group i:
Wandersleben dolomite, Ingersleben sandstone and Glei-
chenberg sandstone (Figs. 15, 16). This suggests that not
only the abundance of capillary pores is important for the
intensity of capillary water uptake, but also the connection
of capillary pores, which can be confirmed by the satura-
tion degree (s value). The correlation between saturation
degree and micropores as well as the sorption (max. weight
increase) is nearly linear (Fig. 20c). The porosity correlates
positively to the capillary water uptake (Fig. 20a). If the
values deviate from this path, the samples not only show a
high amount of macropores, but also a high content
of micropores (Fig. 16). The observed interconnection
between the w value and the (fabric) texture is different.
The sandstones with a well-pronounced bedding also show
a distinct anisotropy of the w value. The reason for this
anisotropy may be the grain shape as well as the orientation
of the grains. Parallel to the bedding, the pore space or the
network of pores is well developed. Water can easily pass
through the rock, and thus the pores build an intercon-
nected network. The anisotropy of the two carbonates is not
that well pronounced. In the case of the Wandersleben
Fig. 20 Correlations of petrophysical properties. a w value dependent on porosity, b l value dependent on porosity, c content of micropores
dependent on s value and d tensile and compressive strength dependent on porosity
Environ Earth Sci (2011) 63:1763–1786 1783
123
dolomite this can be explained by the small interstitial
fossils, which are not aligned parallel to the bedding. The
w value of the Wachsenburg sinter is very small, so that
any conclusion concerning the anisotropy is difficult to
make.
The water transport via water vapour diffusion also
depends on the porosity, but here the higher the l value, the
lower is the porosity (Fig. 20b). This means that sandstones
with a large medium pore radii show a high w value and a
low l value. The hygroscopic water uptake depends sig-
nificantly on the amount of micropores, because the
hygroscopic water absorption takes place in smaller pores
(Peschel 1983; Klopfer 1985; Siegesmund and Du¨rrast
2011). Therefore, samples with a high micropore content
also show a very high increase in weight at higher humid-
ities. However, some samples do not follow this trend. For
example, although the sandstone Seebergen exhibits more
or less the same amount of micropores, the hygroscopic
water uptake is clearly lower than the Ro¨hnberg sandstone.
Most likely the micropores of the Seebergen sandstone are
not very well interconnected. In general, the weight increase
does not depend on the porosity. Highly porous sandstones,
such as the Ingersleben and Gleichenberg sandstone and the
low porous Wachsenburg and Seebergen sandstones, can
show medium weight increases.
Along with the water balance, the strength in stones is
important for the resistance against weathering, because
when the strength of a rock is exceeded the fabric begins to
disintegrate. The measured tensile and compressive
strength in the sandstones depend on these three factors:
the porosity (medium pore radii), the grain contact and
cementation. Sandstones with low porosity show mainly
quartz cementation, concave–convex to sutured grain
contacts and they exhibit a high tensile and compressive
strength. This type of rock is represented by the sandstones
of Seebergen and the Wachsenburg. They show sutured
grain contacts as well as quartz cementation and partially
calcite cement, which stabilizes the framework and results
in a high strength. In contrast, the sandstones from Hind-
felden and Ingersleben are characterised by a highly ductile
clayey matrix or lithoclasts that do not allow the formation
of stable grains to be built for generating a strong granular
grain structure. Moreover, the Ra¨t sandstones from Ro¨hn-
berg and Gleichenberg show a low strength, caused by its
high porosity and the predominant point contact. The
observed decrease of strength at the water-saturated state
was already mentioned by Hirschwald (1908) and is called
‘‘softening’’. According to Morales et al. 2007 or Siedel
(2010), this effect can reach a decrease of 50% in sand-
stones. In the present study, the Hindfelden and Ingersleben
sandstone nearly reach a decrease of this amount. Seeber-
gen and Semionotus sandstones only show a slight decrease
through water saturation.
The strength of the two carbonates is, besides the
amount of porosity and micritic/sparitic areas, controlled
by the heterogeneous distribution of large pores, which is
also confirmed by the high standard deviation. Measured
samples with an inappropriate distribution of large, elon-
gated pores cannot develop a stable network of calcite,
which is why they exhibit a very low strength. In contrast,
some areas consisting of smaller pores and a micritic fabric
show very high strength properties.
Weathering properties
The investigation of weathering behaviour on-site and in
the laboratory show that many occurring decay phenomena
can be traced back to moisture expansion as well as salt
crystallisation in the pore space. Moreover, the intensity
and shape of deterioration depends on different rock
parameters.
Sandstones with a high porosity, high content of mi-
cropores and altered lithoclasts ([20%), like the lithare-
nites from Hindfelden and Ingersleben, show very high
values for moisture expansion, which is confirmed by the
studies of Ruedrich et al. (2010a). The Hindfelden sand-
stone reaches the maximum length change for sandstones
during moisturisation with a value of *5 mm/m (Schuh
1987; Snethlage and Wendler 1996). In contrast, the
quartz-arenites and subarkoses with high quartz contents
show low porosities and low contents of micropores as well
as low moisture expansion values. Furthermore, sandstones
with distinctly pronounced bedding, such as Hindfelden,
Ingersleben and Gleichenberg sandstones, show a clear
anisotropy.
The results of the salt attack tests agree with other
studies on German sandstones (Snethlage and Wendler
1996, Fitzner and Snethlage 1982, Rossi-Manaresi and
Tucci 1991, Ruedrich et al. 2005, Ruedrich and Sieges-
mund 2006), where samples with a high amount of smaller
capillary pores and micropores are highly sensitive to salt
attack. According to Snethlage and Wendler (1996), the
pore space properties, such as porosity and pore size dis-
tribution, control the solution transportation and restore
behaviour, and in consequence also the salt distribution and
enrichment in the rock. Thus, a link between the salt attack
resistance and the groups of pore size distributions is
observable. Rocks belonging to group i and iii (Figs. 16,
17) have high amount of micropores and exhibit low
resistance during salt attack.
According to Ruedrich and Siegesmund (2007), the
different deterioration phenomena during salt attack tests
can be traced back to the pore space properties. Sandstones,
showing a slow drying rate, exhibit scaling as the main
phenomenon. In contrast, sandstones with a high drying
velocity show sanding as the prevalent deterioration
1784 Environ Earth Sci (2011) 63:1763–1786
123
phenomenon. Moreover, the strength of the rocks seems to
influence the sensitivity to salt attack. Rocks, showing a
low strength, such as Hindfelden and Ingersleben, are less
resistant than rocks with a high strength, like the Wachs-
enburg sandstone or Wachsenburg sinter. This was also
observed by Ruedrich et al. 2005.
Conclusions––construction suitability
The investigation of the material behaviour and the dete-
rioration at the residential building ruins allows an eval-
uation to be made concerning construction suitability and
possible material replacement. Without considering the
present day mining situation in the Drei Gleichen area,
any possible replacement of deteriorated stones at the
building may not be done, if no suitable material can be
found in the region. At present, the mining of natural
building stones depends on the availability of the material,
but less so on the means of transporting the stones.
However, luctrative mining is limited by the material
behaviour of the rocks.
• In the natural environment, only the Wachsenburg
sinter shows a marginal deterioration, which was also
verified by the laboratory tests. Besides a low thermal
coefficient, the rock shows a minor moisture expansion
and a high resistance against salt loading. This behav-
iour can probably be traced back to its pore space
properties, which allows just minor water uptake or
water storage in the pore spaces. The other carbonate
behaves differently. The Wandersleben dolomite dete-
rioration is characterised by different shapes and
intensities. In laboratory tests, the rock exhibits a
distinct moisture expansion similar to the sandstones,
which also results in decay-like flaking, scaling and salt
efflorescence. Here the pore size distribution promotes
the capillary water uptake, whereas hygroscopic water
uptake is marginal. Simultaneously, the minor strength
also allows a slight deterioration through salt loading.
• Even though the sandstones from Seebergen, Ro¨hnberg
and Gleichenberg are exposed relatively close and
show the same stratigraphical age, they all exhibit a
totally different material behaviour. The Seebergen
sandstone mainly shows a weak deterioration in the
natural environment and in laboratory tests. This is due
to its mineralogical composition that results in a high
strength. Furthermore, the pore space properties pro-
mote a low water uptake. In contrast, under outdoor
conditions, the Ro¨hnberg sandstone shows intensive
deterioration in the shape of flaking and sanding. This
is due to the grain boundary configuration, e.g. the rock
exhibits grain point contacts. The crystallisation of salt
in the pore space of this weakly cemented sandstone
can easily exceed the strength of the rock. The
Gleichenberg sandstone mainly shows deterioration in
the form of relief, which is due to its well-developed
bedding. In this sandstone, the pore space distribution
shows a high water uptake, whereas the grain contact
that results in a high porosity causes the rock to have a
low strength. All Ra¨t sandstones show a low hygric
swelling and also small thermal expansions coeffi-
cients, which are the results of the rock’s mineralogical
composition. Only salt loading causes a difference.
Whereas the Gleichenberg and Ro¨hnberg sandstones
show a distinct deterioration due to salt (also in the
field), the sandstone from Seebergen only exhibits a
slight disintegration. Therefore, the Seebergen sand-
stone can be considered a suitable dimension or
replacement stone.
• Next to the Seebergen sandstone, one of the most
weathering resistant stones of the Drei Gleichen area is
the Wachsenburg sandstone that only occurs as minor
exposures. In the field as well as in the laboratory, this
stone shows just a weak deterioration, which can be
explained by its porosity evolution and the low water
uptake and high strength. The water uptake and the
strength properties prove that this sandstone meets the
structural and engineering specifications for use as a
dimension stone. However, the deposit is only locally
exposed in a small area below the Wachsenburg, and
thus replacing the deteriorated stones with fresh ones is
near to impossible.
• The most susceptible stones with regard to weathering
in the area are the altered lithoclast-rich sandstones
from Hindfelden and Ingersleben. Because of their low
strength the stones are easily workable, but also show a
low resistance to weathering. The presence of altered
lithoclasts as well as an inappropriate pore size
distribution results in low strength properties and a
high water uptake. Sandstones showing a better water
balance but similar strength properties (e.g. lower
content of altered lithoclasts) would probably be more
suitable as a replacement stone.
Acknowledgments We would like to thank the Deutsche Bun-
desstiftung Umwelt for supporting the Drei Gleichen project and the
long-term PhD fellowship for H. Stu¨ck (AZ 20008/997). Furthermore,
gratitude also goes to A. To¨ro¨k for his very helpful comments on an
earlier version of this paper and to Chr. Gross for editing the English.
Open Access This article is distributed under the terms of the
Creative Commons Attribution Noncommercial License which per-
mits any noncommercial use, distribution, and reproduction in any
medium, provided the original author(s) and source are credited.
Environ Earth Sci (2011) 63:1763–1786 1785
123
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