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In this work, the polishability of six types of building limestone with different physical and mechanical
properties is reported after Moh’d (1996). Using the multiple regression technique on the raw data of Moh’d
(1996) eight equations have been formulated to predict the two components of polishability (roughness and
gloss).
2. SAMPLE PREPARATION
Specimens with different degrees of surface finish were prepared. Using a bench saw with a diamond tipped
blade, 4 cm-cube samples were sliced to produce 5 specimens from each of the 6 types of limestone being
examined. The resulting sawn surface was used as stage 1 in the investigation. The remaining slices were
ground on a diamond-lapping wheel (100/120 grit size) with a sample of each being retained as stage 2. In
the third and fourth stages, all samples were ground to 600F SiC on glass plate, so producing specimens for
stage 3. Using a similar method, specimens for stage 4 were prepared by grinding the samples to 1000F
SiC. The final specimen from each rock type was polished on the ground/flattened surface, starting at 14µ
m diamond paste on a parchment type cloth, through 6µm, 3µm, 1µm and finally 0.25µm.
Throughout the different preparations, water was used as a lubricant, with the exception of the polishing
process, where a diamond polishing fluid was used in conjunction with the diamond pastes.
Equipment used in the sample preparation included
- Bench saw with 250mm diamond blade (Stage 1);
- Diamond lap with 100mm diamond in bronze cup wheel (Stage 2);
- Silicon Carbide powders (SiC) -600F and 1000F grades on 6mm glass plate (Stage 3 and Stage 4);
- Polishing machine - Struers Dap 5 with PdM Force Unit;
- Polishing compounds - Kemet Ltd (Stage 5); and
- Polishing lubricant - Hyprez Fluid
3. TESTING METHOD
Specimens used in this study are 4cm x 4cm x 1cm in dimension. The Cyper Optics Point Range Sensor
(PRS) model 30 and a portable gloss meter available at BRE were employed to evaluate the average
roughness and gloss values. The PRS is a laser-based, non-contact sensor uses a technique known as laser
triangulation to measure the distance between the sensor and an object surface. The PRS works by
generating a spot of laser light and projecting that laser spot onto an object's surface. A highly polished
surface reflects the laser light; a rough surface scatters the light. A portion of the laser light coming off the
object surface reaches the PRS and is imaged on a solid state detector. The detector is able to determine the
object's surface height by calculating the centroid of the laser spot image. If the surface height changes,
then the laser spot is imaged on a different portion of the detector. PRS-30 used during this study has the
following specifications:
Resolution: 0.76 µm
Range: 0.3 mm
Standoff: 7.6 mm
Receiver Angle: 90°
Spot Diameter: 10.2 µm
For Ra (average roughness measurement) a step size of 20µm with scan length of 4 cm was used. Ra
values given in this work is the average of eight profiles (with a total length of 32 cm) measured in each
specimen as follows: 2 bisectors, 2 diameters, 4 marginals (parallel to and 1 cm away from the margins).
Gloss value reported here is the average of two readings.
3. The Polishability of Some Jordanian Limestones
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4. SAMPLES STUDIED
The petrographic nomenclature is following one or more of the following schemes: Folk (1959, 1962),
Dunham (1962), and Fookes and Higginbottom (1975). Yanabi is an Upper Cretaceous, yellow grey, fine-
grained limestone (peloidal micrite/wackestone with packstone lenses) with 53.01% CaO, 2.67 g/cm
3
dry
density, and 147.2 MPa uniaxial compressive strength. Izrit is an Eocene, moderately orange pink chalk
(micrite/mudstone-wackestone) with 50.94% CaO, 1.96 g/cm3
dry density, and 33 MPa uniaxial
compressive strength. Saham is an Oligocene, cream, conglomeratic (reworked) limestone with 49.65%
CaO (12.66% SiO2,), 2.66 g/cm
3
dry density, and 91.7 MPa uniaxial compressive strength. Hallabat is an
Upper Cretaceous, pinkish grey, coarse bioclastic limestone (biosparrudite/packstone-grainstone) with
51.77% CaO, 2.22 g/cm3
dry density, and 26.2 MPa uniaxial compressive strength. Karak is an Upper
Cretaceous, light olive grey, coarse bioclastic limestone (biosparite-biosparrudite/ fossiliferous packstone-
grainstone) with 47.76% CaO, 2.65 g/cm
3
dry density, and 110.3 MPa uniaxial compressive strength. Tafih
is an Upper Cretaceous cream-white, coarse crystalline limestone (sparite) with 54.52% CaO, 2.25 g/cm
3
dry density, and 30 MPa uniaxial compressive strength.
5. RESULTS OF THE PRESENT WORK
5.1. Change of roughness and gloss with progress of polish
Summaries of roughness and 'glossiness' data in the different stages of polish are given in Tables 1 and 2
and shown diagrammatically in Figures 1 to 4.
Table 1 Summary of surface roughness data (in micrometers).
As Sawn Diam Lap SiC600 SiC1000 Diamond
Karak 32.13 17.38 14.00 11.63 10.75
Saham 29.50 18.13 18.00 16.00 15.09
Izrit 47.13 31.63 13.00 12.63 11.89
Hallabat 51.25 28.13 20.50 17.13 17.13
Yanabi 35.63 14.13 10.75 8.38 7.76
Tafih 62.88 23.13 21.75 18.63 17.81
5.1.1. As Sawn
The surface roughness values of the as sawn samples range from about 30µm to 60µm. The sequence of
rocks arranged from highest to lowest roughness is as follows: Tafih, Hallabat, Izrit, Yanabi, Karak and
Saham. The high range of surface roughness values raises the following questions: Are the surface
roughness values of the as sawn rock a function of the physical/mechanical properties of the rock (texture
and strength) or a function of the cutting process (type of cutting machine, cutting parameters)?. In other
words, what is the role of personal factors on deciding the surface roughness values? As the same cutting
parameters, cutting machine, and all the rocks studied were cut by the same person it seems that the
physical/mechanical properties of the rock are the critical factors. It can be seen from Figure 2 that the
surface roughness values of the as sawn rocks can be subdivided into two groups: the first group with an
average surface roughness of 53.75µm including Tafih, Hallabat, and Izrit which can be considered of weak
to moderate strength and specific gravity, and high porosity and water absorption; and the second group
with an average surface roughness of 32.42µm including Yanabi, Karak, and Saham and of relatively high
strength and specific gravity and low porosity and water absorption. A second look on the members of the
two groups shows that they are petrographically different (crystalline limestone, fossiliferous limestone and
chalk for the first group, and micritic limestone, fossiliferous limestone and conglomeratic limestone for
the second group). Provided that the cutting process occurred under the same technical conditions, it can
be concluded that the physical/mechanical properties of the rock are the conclusive factor in deciding the
roughness of the as sawn rock.
4. Basem K. Moh’D
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Figure 1 Decreasing of Ra value with the progress of polish.
Figure 2 Surface roughness data of the selected stones in the different stages of polish: 1. as sawn, 2. diamond-lap,
3. SiC 600, 4. SiC 100, and 5. 1/4 µm diamond.
Table 2 Change of gloss values of the selected limestones with progress of polish.
As Sawn Diam. Lap SiC 600 SiC 1000 Diamond
Karak 1.65 2.35 1.5 2.65 42.6
Saham 1.7 1.7 1.75 2.7 22.65
Izrit 1.5 1.5 1.4 1.4 14.5
Hallabat 1.9 2 2 2.6 46.9
Yanabi 1.95 2.35 2 2.85 48.1
Tafih 1.8 1.75 1.5 3.75 43.7
Gloss meter values of the 'as sawn' surfaces are the lowest compared to other stages of the polishing
process with an average of 1.75% , a standard deviation of 0.17, and a range of 1.5-1.95%. The lowest
values were encountered in Izrit (chalk), and the highest in Yanabi. In descending order, the sequence of
rocks according to their gloss value is as follows: Yanabi, Hallabat, Tafih, Saham, Karak, Izrit.
0
10
20
30
40
50
60
70
SurfaceRoughness
As Sawn
Diam Lap
SiC600
SiC1000
Diamond
0
10
20
30
40
50
60
70
0 1 2 3 4 5
SurfaceRoughness
Karak
Saham
Izrit
Hallabat
Yanabi
Tafih
5. The Polishability of Some Jordanian Limestones
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Figure 3 Development of 'glossiness' with the progress of polish.
5.1.2. Diamond Lap
Diamond lapped samples compared with the 'as sawn' ones show a lower average roughness (22.09µm) and
less scattering (standard deviation: 6.78µm). The two- group division is still evident but now the average
of the first group is 27.63µ and that of the second group 16.55µm. Physical/mechanical properties although
are still the dominant factors are of less importance. It seems that the diamond lap grinding process
succeeded in lowering the differences in roughness values of the different rocks and consequently the
importance of the physical/mechanical properties on roughness values. The sequence of rocks according to
their roughness is as follows (from the highest to the lowest): Izrit, Hallabat, Tafih, Saham, Karak, and
Yanabi. The role of petrography is now more pronounced with chalk having the highest roughness, micritic
limestone the lowest, and other lithologies intermediate roughness values.
In this stage the overall glossiness has little improved (average:1.94%; standard deviation: 0.35, range:
1.5-2.35%). In descending order the sequence of rocks according to their gloss values is as follows: Yanabi
and Karak, Hallabat, Tafih, Saham, and Izrit.
5.1.3. SiC 600
The two-group division is not valid any more as all the rocks now are lumped under one group. SiC 600
improved the rock surfaces by decreasing both the roughness values (average 16.33µm) and the scattering
between them (standard deviation 4.41). The sequence of rocks according to their roughness values is as
follows (in descending order): Tafih, Hallabat, Saham, Karak, Izrit, and Yanabi. In this case the highest
roughness was encountered in the Tafih stone which consists of crystalline limestone. Similar to the
previous stage Yanabi stone has the lowest value of roughness. In this stage the polishability of the Izrit
chalk has improved appreciably (from about 32µm to 13µm).
The average gloss value (1.69%) is lower than that of the previous stage. The same is applied for
scattering of data (standard deviation: 0.27, range: 1.4-2.0). Yanabi and hallabat have the best gloss values
(2.0%), and Izrit the worst (1.4%). The sequence of gloss values is as follows: Yanabi=Hallabat>Saham>
Karak= Tafih>Izrit.
5.1.4. SiC 1000
SiC 1000 has little improved the surfaces of the rock as revealed by the average of roughness values of
14.07µm and slightly lowered the scattering of these values (3.85). The sequence of rock according to their
roughness values is as follows (in descending order): Tafih, Hallabat, Saham, Izrit, Karak, Yanabi which is
Karak Saham Izrit Hallabat Yanabi Tafih
0
5
10
15
20
25
30
35
40
45
50
GlossValue% As Sawn
Diam. Lap
SiC 600
SiC 1000
Diamond
6. Basem K. Moh’D
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exactly the same series using SiC 600 except for Izrit and Karak which changed their ranks. The difference
in roughness values ∆ = {100[(surface roughness of previous stage- surface roughness of present
stage)/surface roughness of previous stage]} and consequently the improvement is as follows (in
descending order): Yanabi, Karak, Hallabat, Tafih, Saham, and Izrit. So the highest improvement occurred
in the foraminiferal peloidal limestone lithologies and the least in chalk.
The average of gloss values (2.66%) has improved slightly whereas both the scattering (0.75) and range
(1.4-3.75) have increased. The sequence of rocks according to their gloss values is as follows: Tafih>Yanabi
>Saham>Karak> Hallabat>Izrit. The relatively high gloss value of the Tafih in this stage may be connected,
in addition to its crystalline structure, with filling a large part of its pore space with Silicon carbide (due to
its high permeability).
5.1.5. Diamond (1/4µµµµm)
This is the final stage used to polish the different stones. During this stage (Wright and Rouse, 1992) the
lowest values of roughness were produced. These values were slightly lower than those produced in the
previous stage (SiC 1000). Hallabat has the worst roughness followed by Tafih, both of them have high
porosity (17%), large grain size, and medium strength. Izrit, Saham, and Karak stones have similar
roughness values although they have different lithology, grain size, porosity and strength. Yanabi stone
remained the best as the surface roughness is concerned, this may be connected to its high strength, very
fine grai and low porosity.
This final stage is the most important as far as gloss value development is concerned. According to their
gloss value, the different stones are arranged as follows (in descending order): Yanabi, Hallabat, Tafih,
Karak, Saham, and Izrit. There is no much difference in the gloss values in the first four stone types (42.6
to 48.1). Chalk has the lowest acceptability of polish followed by the conglomeratic facies (due to large
differences between the grains and matrix in both size and composition). This is an impure limestone rock
as evidenced by the presence of chert and quartz grains as well as different grain sizes of calcite (reworked
limestone). The presence of organic matter in the Karak stone may be the reason of its low gloss values
despite its high strength. The average of gloss value has developed appreciably (36.41), but the scattering
(14.20), and range (14.5-48.1) have also increased.
Figure 4 Scatter plot of average roughness versus gloss value in the final stage of polish; grain size is as follows:
large +, medium: squares, and fine: circles.
Average Roughness Ra (laser microns)
GlossValue%
10
15
20
25
30
35
40
45
50
10 15 20 25 30 35
Tafih
Yanabi
Hallabat
Izrit
Saham
Karak
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2. How roughness and gloss are related to other factors in the final stage of polish
Table 3 shows gloss and roughness as measured in the last stage of polish along with porosity, UCS, lime
and silica. Table 4 is a correlation matrix between the different variables. It can be seen that there is
practically no relation between gloss and roughness. This is odd as it is well known that roughness is one
of the most important factors upon which gloss depends. The poor correlation is caused by the presence of
at least two sets of stones types as can be seen in Figure 4, if each set is taken alone then very strong positive
correlation will appear. Here the group of Izrit, Saham, Hallabat and Tafih stones is fitted by an exponential
function with r = 0.93, indicating very strong non-linear correlation between roughness and gloss. It is
expected that the other two stones (Yanabi and Karak) will have a curve parallel to that of the first group.
Table 3 Surface roughness (Ra) and gloss in the last stage of polish along with porosity, compressive strength, lime
and silica.
Ra
µm
Gloss
%
Porosity
%
UCS
MPa
CaO
%
SiO2
%
Karak 10.75 42.6 2.21 110 47.76 13.37
Saham 15.9 22.65 1.84 91.7 49.65 10.2
Izrit 11.89 14.5 27.67 33 50.94 6.46
Hallabat 17.13 46.9 18.08 26.2 51.77 6.74
Yanabi 7.76 48.1 1.48 147.2 53.01 4.09
Tafih 17.81 43.7 16.97 30 54.52 0.89
Figure 4 Gloss value versus roughness.
Table 4 Correlation matrix between the different parameters.
Ra µµµµm Gloss % Porosity % UCS MPa CaO % SiO2 %
Ra µm 1.00
Gloss % -0.04 1.00
Porosity % 0.37 -0.36 1.00
UCS MPa -0.76 0.25 -0.87 1.00
CaO % 0.25 0.33 0.35 -0.30 1.00
SiO2 % -0.22 -0.24 -0.43 0.34 -0.99 1.00
Using multiple regression roughness Ra, can be derived using the following equations:
Ra = -0.459*porosity – 0.144* UCS + 0.095*CaO – 0.113*SiO2 + 25.083
(r = 0.996, SD = 0.759)
Ra = -0.449*porosity – 0.143* UCS + 0.293*CaO + 13.922
(r = 0.996, SD = 0.541)
y = 1.3079e0.1968x
R2
= 0.8673
0
10
20
30
40
50
60
0 5 10 15 20
Roughness (microns)
Glossvalue%
Others
Kar & Yan
Expon. (Others)
8. Basem K. Moh’D
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Ra = -0.425*porosity – 0.143* UCS + 28.648
(r = 0.982, SD = 0.960)
Gloss also can be predicted using multiple regression using the following equations:
Gloss = -15.131*Ra – 7.318*porosity – 2.192* UCS + 28.028*CaO + 11.928*SiO2 1035. 545
(r = 1.00, SD = 0.00)
Gloss = 0.348*porosity +0.104* UCS + 32.299*CaO + 16.659*SiO2 – 1747.272
(r = 0.77, SD = 20.12)
Gloss = 0.050* UCS + 28.198*CaO + 14.279*SiO2 -1512.485
(r = 0.77, SD = 14.35)
Gloss = 30.179*CaO + 15.542*SiO2- 1619.197
(r = 0.75, SD = 12.08)
Gloss = -0.920*Ra + 32.660*CaO + 16.641*SiO2 - 1738. 667
(r = 0.78, SD = 13.79)
6. DISCUSSION AND CONCLUSIONS
Limestone which takes polish is referred to in industry as marble. Despite the fact that polishing of stone
has been practiced from times immemorial as evidenced by artifacts and gemstones, it has received little of
the attention from applied science received by other materials. There is no universal theory explaining
conclusively the polishing process. As different surfaces react differently to different processes, the effects
on each material has to be judged by its merits.
Pulling-out of grains from the polished surface of the Tafih stone is a noticeable feature. Any plans for
using this rock as marble may necessitate some curing processes to improve the strength, minimize the
pulling out of grains, and consequently preserve the polish.
Various properties of rock affect polishability. In terms of texture, the highly crystalline limestone
varieties produced the lowest roughness and highest gloss, while chalk produced the worst results in each
case. This is explained by the three excellent cleavage planes of calcite producing 'polished' surfaces in
three dimensions in well-crystallized varieties. Low porosity rocks gave the highest gloss and low
roughness values as would be expected. In high porosity stones, pores are exposed with continued polish,
so little reduction in surface roughness occurs. The purity of crystalline limestones also appears to affect
the roughness and gloss, with impurities producing differential hardness and polishability within the rock.
To predict the gloss, all available data (roughness, porosity, compressive strength, silica and lime
contents) must be used in the multiple regression. In this case, the coefficient of correlation r is 1.00. If
roughness or other parameters are not used in the regression, you will be able to predict gloss but the
coefficient of correlation r will be less than 1.00. Even if the chemistry (silica and/or lime) is not known,
porosity and strength can be used to derive roughness. The latter parameter can be used along with strength
and porosity to predict the gloss value in the final stage of polish.
To conclude, it can be said that even if there is no access to a gloss meter and/or roughness equipment,
the polishability can still be predicted using the equations formulated by the present work. It is highly
recommended to use a larger database and check the validity of the formulated equations on building
limestones in countries other than Jordan.
9. The Polishability of Some Jordanian Limestones
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[1] Dunham, R. J., 1962. Classification of carbonate rocks according to depositional texture, in W. E. Ham,
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[3] Folk, R. L., 1962. Spectral subdivision of limestone types, in W. E. Ham, ed., Classification of carbonate
rocks, Mem. AAPG 1, pp. 62-84.
[4] Fookes, P. G., and Higginbottom, I. E., 1975. The classification and description of near-shore carbonate
sediments for engineering purposes, Geotechnique, 25, 21, pp. 406-11.
[5] Moh’d, B. K. 1996. Evaluation of some Jordanian limestones as building stones, PhD Thesis, Queen
Mary and Westfield College, University of London, UK.
[6] L. Prathyusha and B. Harish Naik, Effect of Stone Dust and Fines on the Properties of High Strength
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[7] Akshaya Kumar Sabat and Swapnaranee Mohanta, Performance of Limestone Dust Stabilized Expansive
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