Water absorption and drying features of different

Construction and Building Materials 63 (2014) 257–270

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Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat

Water absorption and drying features of different natural building stones Y. Ozcelik a,⇑, A. Ozguven b a b

Hacettepe University, Department of Mining Engineering, Ankara, Turkey General Directorate of Mineral Research and Exploration, Ankara, Turkey

h i g h l i g h t s Water absorption is one of the most important attributes of natural building stones. Porosity of more water absorbing stones is also an accelerating factor for drying process. First 24 h are very important for water absorption and drying. Apparent density, open and total porosity properties are highly related with water absorption ratio.

a r t i c l e

i n f o

Article history: Received 22 January 2014 Received in revised form 13 March 2014 Accepted 2 April 2014

Keywords: Natural building stones Water absorption Drying Density Porosity Mineralogical-petrographical properties

a b s t r a c t It is very important to know the properties of natural stones that are used in building construction in order to determine the specific areas of usage. Among those, water absorption is one of the most important as it determines various mechanical and physical properties. The objectives of this study are to determine the water absorption characteristics of natural building stones with different composition, structure and texture properties, to determine the parameters affecting the water absorption ratio and to obtain the drying features of natural building stones. For this purpose, in this study 12 natural building stones with different structural and textural properties are studied in detail based on their water absorption attributes. For every rock type, graphics of water absorption against time are prepared and evaluated. The relationships of density, apparent density, open porosity, total porosity and open/total porosity ratios with water absorption are studied. The drying features of the samples which absorbed water are also determined. Relationships between standard times and measured real times are obtained and the results of detailed evaluations are presented with the purpose of helping standard developers and experimental researchers. The results of these tests indicate that first 24 h are very important for water absorption and drying test and apparent porosity, open and total porosity properties are highly related with water absorption ratio. On the other hand, it is found that porosity of more water absorbing stones is also an accelerating factor for drying process. Ó 2014 Elsevier Ltd. All rights reserved.

1. Introduction Water absorption (WA) value is one of the most important parameters of rocks which have an impact upon their physical and mechanical properties [1]. This is particularly important for building stones, as it affects their hygiene, aesthetics and also structural safety [2,3]. Water absorption is the proportion of water which can be absorbed by stone under specific immersion conditions [4]. The negative influences of water on many physical and mechanical properties of stone are well known. Water softens stone and decreases its strength, as well as its abrasion and frost resistances. Stone with increased relative porosity and thus increased ⇑ Corresponding author. Tel.: +90 312 2976447; fax: +90 312 2992155. E-mail address: [email protected] (Y. Ozcelik). http://dx.doi.org/10.1016/j.conbuildmat.2014.04.030 0950-0618/Ó 2014 Elsevier Ltd. All rights reserved.

absorption is more sensitive and hence less durable [5]. The value obtained provides some indication of the stone’s performance in service, particularly its strength, durability and stain resistance. The water absorption value of a stone is also closely related to its inherent apparent porosity, i.e. the volume of open pores accessible to moisture within the stone [4]. Durability is a complex criteria determined by inherent strength, water absorption and pore space. Lower water absorption generally correlates to a greater durability, as it restricts the passage of deleterious solutions, but a larger pore size can assist with durability by reducing the pressure applied by salt or ice crystallization on the walls of the pores [6]. There are three main factors that determine stain resistance; these are water absorption, composition and appearance. The weighting of each of these factors varies depending on the stone type and application. Water absorption is directly related to stain

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resistance. Simply put, a higher water absorption capacity allows for a higher ‘stain holding’ capacity [6]. There are many studies on the water absorption properties of natural building stones. These studies are mostly focused on the changes in the mechanical property of natural building stones which have absorbed water [7,8]. A new rock classification system (moisture index) has been presented in order to evaluate the properties of wet rock by Fahimifar and Soroush [9]. Karaca [3] analyzed the water absorption and dehydration time of five different types of natural building stones (marble, limestone, travertine, onyx and granite). In that study, Karaca [3] tested final water absorption ratios and drying features while ignoring the durations and course of those processes. Dejian et al. [10] analyzed rock samples using a water absorption test and scanning electron microscopic (SEM) experiments. Sariisik et al. [11] studied on characterization of physical and mechanical properties including water absorption of natural stones affected by ground water under different ambient conditions. But, these studies are not sufficient for fully explaining the water absorption properties and drying features of natural building stones. No studies focusing on the water absorption properties and drying features of rocks with different structural properties and formations are to be found in the literature. The calculation methods and procedures employed to obtain the water absorption value of rocks have been explained in several publications, including ASTM C-97 [12], TS 699 [13] and RILEM [14]. However, these standards do not provide any explanation of the significance of sample dimension and time [1]. According to these standards, water absorption experiments may be performed with samples of different dimensions and for some of those standards, after certain durations (48 h) of water absorption or when the water absorption levels of samples reach a specific point, experiments are concluded. Obtaining proper results from water absorption experiments is difficult and an experiment-planning process is not possible due to the lack of discrimination between different natural building stones according to their water absorption properties. For different types of natural building stones, individual water absorption characteristics need to be determined and approximate durations of water absorption for every natural building stone must be calculated. Thus, the necessary revisions for correcting the standards of water absorption experiments and the addition of auxiliary information for planning experiments may be added. This study is an important step towards executing better and more efficient water absorption experiments. 2. Materials and methods In this study, the water absorption and drying features of different types of natural building stones were characterized. To achieve this, natural building stone samples were characterized and monitorized until they were completely saturated and dried. In addition, physical tests (such as true density, apparent density and open and total porosity tests) were carried out and the results were discussed.

Table 1 Types and names of samples. Sample code

Commercial name

Stone type

Rock type

T O C HP DB SB AG MM GA PA G GG

Denizli travertine Agri onyx Adana conglomera Hazar pink Daisy beige Sivrihisar beige Afyon gray Mugla milas Gray andesite Pink andesite Granite Green granite

Travertine Onyx Conglomera Limestone Limestone Limestone Marble Marble Andesite Andesite Granite Granite

Sedimentary Sedimentary Sedimentary Sedimentary Sedimentary Sedimentary Metamorphic Metamorphic Igneous Igneous Igneous Igneous

Fig. 1. Samples used in water absorption and drying test.

Rocks with different formation, structure, texture and porosity features were chosen and water absorption and drying experiments were performed on 12 different samples which can be commercially obtained and are commonly. These samples consisted of the following rock types: marbles, limestones, granites, andesites, travertines, onyx and conglomerate. The names and types of these samples are presented in Table 1, and their appearances in Fig. 1. In order to better determine the water absorption and drying features of natural building stones with different properties, experiments were performed with 10 samples for each stone. Experimental samples were prepared as cubes of 50 ± 5 mm dimensions and in accordance with the CSN EN 1936 [15] and CSN EN 13755 [16] standards. Samples were completely dried in an air-conditioned drying-oven at 70 ± 5 °C and their weights were recorded. Water absorption experiments were carried out in accordance with the CSN EN 13755 [16] standard, the experimental samples were firstly half-submerged in water, after one hour, they were three-quarters submerged, and at the end of the second hour, they were submerged 25 ± 5 mm in the water. Specimens were taken out of the water, quickly wiped with a damp cloth and were then weighed within an accuracy of 0.01 g. Specimens were immersed again in water and the tests were continued. The water absorption experiments were concluded when the specimens are completely saturated. Over 6 days, 23 different readings were taken after short-term intervals firstly then after longer intervals in order to better determine the water absorption characteristics of the different natural building stones. Completely saturated specimens were placed in an air-conditioned drying-oven at 70 ± 5 °C. Over 5 days, 22 different weight readings were taken after short-term and then longer-term intervals. In order to better evaluate their water absorption and drying features, the samples were also tested for real density, apparent density, open and total porosity. The results are shown in Table 2. Tests were performed using a Accupyc 3600 multipicnometer with helium gas in accordance with Real density ASTM D-5550-06 [17]. Apparent density, open and total porosity experiments were performed according to the CSN EN 1936 [15] standard. The relationships between the chemical composition and water absorption ratios of natural building stones were compared and studied regardless of their origin and type. The compositions of natural building stones were determined using the XRF method and the results obtained are presented in Table 3. In addition to the effects of the main components (presented in Table 3) on water absorption ratios, the effects of lesser components (presented in Table 4) traced in specimens were also studied. Detailed studies were carried out to determine the effects of the chemical properties of specimens on their water absorption ratio. Graphs based on these chosen parameters were drawn and relationships were investigated. Mineralogy is one of the most important factors that determine the kind of effects water has on stone types (physical, chemical or physico-chemical effects). Most minerals do not show any reaction to water; however some of them are very sensitive to water. The percentages of these minerals in rocks must be determined

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Y. Ozcelik, A. Ozguven / Construction and Building Materials 63 (2014) 257–270 Table 2 Physical properties of samples. Sample

Density (g/cm3)

Apparent density (g/cm3)

Open porosity (%)

Total porosity (%)

Open/total porosity ratio (%)

Water absorption (%)

T O C HP DB SB AG MM PA GA G GG

2.6990 2.7264 2.7048 2.7379 2.7239 2.7222 2.7189 2.7269 2.6172 2.6352 2.6976 3.1309

2.4876 2.6684 2.6768 2.6549 2.6781 2.6980 2.7128 2.7124 2.2844 2.3480 2.6689 3.0881

3.07 0.84 0.58 1.78 1.10 0.45 0.18 0.29 7.70 4.60 0.89 0.78

7.83 2.13 1.03 3.03 1.68 0.89 0.22 0.53 12.71 10.90 1.06 1.37

39.19 39.71 55.97 58.66 65.50 50.57 82.96 54.29 60.58 42.24 83.96 56..90

1.42 0.27 0.33 1.00 0.44 0.20 0.07 0.12 3.99 3.24 0.37 0.24

Table 3 Water absorption and chemical analysis results of examined specimens. No

Sample

WA

Na2O

MgO

Al2O3

SiO2

K2O

CaO

TiO2

MnO

Fe2O3

Li

1 2 3 4 5 6 7 8 9 10 11 12


1.42 0.27 0.33 1.00 0.44 0.20 0.07 0.12 3.99 3.24 0.37 0.24

0.07 0.08 0.07 0.08 0.07 0.09 0.07 0.08 2.21 3.52 2.90 0.08

1.36 0.91 3.87 0.03 1.03 0.67 0.89 0.03 4.15 3.14 0.42 11.83

2.31 0.63 3.57 0.09 1.81 1.82 0.50 0.32 15.36 16.56 16.20 17.48

1.34 1.81 21.01 0.28 1.44 1.88 0.72 1.20 61.75 59.81 66.86 48.21

0.58 0.78 0.75 0.01 0.97 0.64 0.48 0.01 2.97 2.85 5.39 0.85

56.18 52.11 36.90 62.96 58.76 50.53 48.63 61.03 5.92 4.56 2.74 9.34

0.18 0.35 0.30 0.00 0.31 0.32 0.76 0.01 0.50 0.34 0.11 0.72

0.04 0.05 0.05 0.01 0.04 0.05 0.16 0.01 0.07 0.04 0.04 0.14

1.96 2.20 3.13 0.06 2.59 1.87 0.81 0.09 5.64 5.04 3.21 10.19

35.87 40.82 29.84 36.92 32.80 41.83 46.83 37.84 1.84 3.87 1.93 0.74

Table 4 Water absorption ratios and trace element values of examined specimens. No

Elements Sample

WA %

Ni ppm

Cu ppm

Zn ppm

Ga ppm

As ppm

Sr ppm

Y ppm

Zr ppm

Nb ppm

Sb ppm

Ba ppm

Ce ppm

1 2 3 4 5 6 7 8 9 10 11 12


1.4 0.3 0.3 1.0 0.4 0.2 0.1 0.1 4.0 3.2 0.4 0.2

4.4 3.6 1.1 5.7 3.3 2.4 2.1 4.4 2.8 2.5 2.9 4.7

8.9 10.2 13.4 2.1 9.1 7.8 35.2 1.4 1.2 1.3 1.1 55.8

17.2 37.2 31.9 3.9 36.1 27.1 63.6 2.1 43.2 33.3 9.6 11.5

3.5 6.9 6.6 1.7 9.4 6.5 14.7 3.0 16.1 14.3 13.0 13.8

2.8 5.0 4.6 0.8 6.0 4.8 15.8 3.6 5.3 6.3 1.0 4.8

2702.0 245.9 2703.0 269.4 145.1 249.7 200.2 298.9 178.3 204.8 180.0 322.5

1.0 8.4 3.6 0.8 11.9 6.9 21.0 0.8 16.5 12.0 6.5 15.9

58.0 83.9 67.0 13.7 147.1 66.1 154.3 7.2 154.3 152.0 82.2 98.0

3.6 5.5 6.1 5.9 15.1 11.3 13.0 3.8 9.4 3.2 6.2 18.6

1.0 1.1 1.0 1.0 1.1 1.1 1.7 1.0 0.9 1.0 1.0 0.9

448.0 132.7 44.6 16.4 34.8 106.0 388.4 16.1 34.0 47.0 23.0 97.6

19.0 35.9 23.5 16.2 47.5 17.7 55.0 10.0 52.9 35.2 30.6 26.7

in order to estimate the effect of water on them. Two groups of minerals are prone to reaction in presence of water: evaporite minerals (halids, sulfates, carbonates, nitrates and borates) and clay minerals [9]. Mineralogical-petrographical analyses were carried out with the purpose of discovering the relationship between water absorption properties and mineralogical structure. Thin sections of the natural building stone samples were prepared and were then examined under a polarized microscope to determine the textural features of each sample. The petrographic descriptions and microphotographs of the samples were determined from these thin-sections and are given in Table 5.

3. Results and discussion Relating the physical, chemical and mineralogical properties of natural building stones of different origins and types with their water absorption properties is important with regard to learning about the factors affecting water absorption. The different textural features and mineralogical compositions cause different properties of water absorptions to arise for each rock unit. The properties

examined were analyzed in detail and are presented below because of this. 3.1. Physical properties results and relationships with water absorption The results of the testing are graphically presented in Figs. 2–4. Changes in the water absorption ratio of the examined natural building stones due to time are given for each specimen separately in Fig. 2. Cumulative water absorption ratio changes due to time are given in Fig. 3. Water absorption and drying duration graphs are provided in Fig. 4. According to the results, almost every natural building stone shows the same water absorption trend respectively. Even though water absorption levels may vary, the behavior against time is almost the same. The least water absorbent natural building stone was determined to be marble (0.07–0.12%). Granite (0.24–0.37%), onyx

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Table 5 Petrographic descriptions and microphotographs of the samples. Sample name

Texture

Origin rock type

Mineral composition

Modal mineral composition

Denizli travertine

Vesicular precipitation

Sedimantary travertine

Distinctive vesicular and flow texture including aragonite, calcite and quartz minerals are present

Calcite (30%), aragonite (65%), quartz (2%), other minerals (3%)

Agri onyx

Comb and dog tooth

Sedimentary onyx limestone

Convex-shaped aragonite and calcite minerals are present inside the distinctive comb texture

Calcite (35%), aragonite (61%), dolomite (2%), other minerals (2%)

Adana conglomera

Clastsupported carbonate matrix

Sedimentary petromict conglomerate

Marble, limestone and schist fragments are present inside the carbonate matrix

Quartzite (26%). limestone (31%) andesite (10%), biotite (4%), quartz (12%), calcite (9%), amphibole (4%), other minerals (4%)

Hazar pink

Biosparitic

Sedimentary sparitic limestone

Bioclast, calcite and abundant fossils are present


Daisy beige

Biosparitic


Biosparitic limestone. Moderately crystalline calcite and small amount of opaque minerals are present


Sivrihisar beige

Sparitic


Moderate crystalline calcite and a small amount of recrystalised thinny calcite veins and opaque minerals are present


Afyon gray

Blastosparitic

Metamorphic marble

The calcites with pressure twining are present


Microphotographs

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Y. Ozcelik, A. Ozguven / Construction and Building Materials 63 (2014) 257–270 Table 5 (continued) Sample name

Texture

Origin rock type

Mineral composition

Modal mineral composition

Mugla milas

Granoblastic

Metamorphic marble

Calcite and small amount of muscovite, quartz, and opaque minerals are present

Calcite (98%), other minerals (2%)

Gray andesite

Hypocrystaline porphyric texture

Volcanic andesite

Oligoclase, andesine, amphibole, biotite, and small amount of epidotite and opaque minerals are present

Plagioclase (68%), biotite (12%), amphibole (14%), other minerals (6%)

Pink andesite

Hyaloplitic porphyric

Volcanic andesite

Oligoclase, andesine, amphibole, biotite, and small amount of pyroxene and opaque minerals are present

Plagioclase (63%), biotite (10%), amphibole (10%), pyroxene (9%) other minerals (8%)

Granite

Holocrystaline hipidiomorphic

Plutonic monzogranite

Quartz, orthoclase, oligoclase, biotite, and small amount of amphibole, titanite zircon and opaque minerals are present

Quartz (31%), orthoclase (28%) plagioclase (20%), biotite (9%), amphibole (6%), other minerals (6%)

Green granite

Holocrystaline

Plutonic gabbro

Labradorite, bytownite, pyroxene, and small amount of epidote, tremolite, actinolite and opaque minerals are present

Plagioclase (60%), pyroxene (23%), amphibole (8%), other minerals (9%)

(0.27%), conglomerate (0.33%) and some beiges (0.20–0.44%) also have low water absorption ratios. While travertines absorbs a little more (1.42%), the most water absorbent natural building stones were determined to be andesites (3.24–3.99%). With the exception of andesites, travertines and some beige, all of the examined natural building stones are determined as water absorbent at a rate below 1%. Due to andesites’ porous structure and different compositions, different types of andesites were determined to not display similar water absorption and drying characteristics. GA seems to absorb water over a longer duration and to take a similarly long duration to dry. This is important to consider when planning experiments. Marbles were determined to not need long durations for water absorption and drying. In under one day, both water absorption and drying processes were carried out. Considering this, the first 24 h are very important for marbles with regard to the water absorption and drying processes.

Microphotographs

Lesser water absorbent natural building stones dry in a shorter duration respectively as expected, while more absorbent specimens takes more time to dry. The greater porosity of more absorbent stones must be considered as a factor in shortening the drying process. This phenomenon is observed clearly with travertine and andesite specimens. Meanwhile tighter textured and closed-porous specimens were observed to take a longer time to dry. Conglomerate and gray andesite specimens are separated in time from the other specimens which had the same water absorption and drying trend. Other specimens absorb water fast in the beginning but the absorption progresses at a slower rate as time goes on. These same two specimens have a similar fashion of drying as well considering the other specimens, and dry within almost the same durations. This situation can be observed clearly on the slopes of graphs given in Fig. 2(c) and (j). In this area, the effects of the physical properties of rocks given in Table 2 on water absorption ratio are also examined. The effects of density, apparent density, open porosity, total porosity and

262


Fig. 2. Variation of water absorption ratio of samples depending on time.

open/total porosity ratio values on water absorption ratio are examined and presented in Fig. 5. Considering all natural building stones, some physical properties were observed to directly affect the magnitude of the water absorption ratio. When Fig. 5 is examined, apparent density as well as open and total porosity values seems to have a direct relationship with water absorption ratio. As porosity increases and as apparent density decreases, the water absorption increases.

While the relationship between apparent density and absorption ratio (R2 = 0.671) displays high correlation, the relationship between density and water absorption (R2 = 0.187) shows low correlation. This is mostly because of the fact that specimens are ground until there is no space between particles during the density determination process. It was also observed that when apparent density becomes lower, the water absorption ratio follows a reverse trend.


263

Fig. 3. Variation of cumulative water absorption ratio of samples depending on time.

As expected, a high level of correlation between water absorption and porosity was determined. As porosity increases so does the water absorption. While for the relationship between water absorption and open porosity, the R2 value is 0.961, for the relationship between the total porosity and water absorption that value is 0.950. Besides that, no relationships were found between open porosities’ ratios in total porosity and water absorption. For the relationship between open/total porosity ratio and water absorption ratio, the R2 value is determined to be at the low value of 0.150.

Considering the type of natural building stones separately, Fig. 5 indicates that there are high correlations between water absorption of igneous and sedimentary rocks and apparent density (R2i = 0.80; R2s = 0.772), open porosity (R2i = 0.947; R2s = 0.954) and total porosity (R2i = 0.996; R2s = 0.845). In addition, no relationships were found between open porosities’ ratios in total porosity and water absorption for both rock types. However, moderate relationship was found between water absorption of igneous rocks and density (R2i = 0.592) and no relationship was found between water

264

Y. Ozcelik, A. Ozguven / Construction and Building Materials 63 (2014) 257–270 Table 6 R2 values of the relationships between water absorption and chemical components.

Fig. 4. Water absorption and drying times of samples used in this study.

absorption of sedimentary rocks and density (R2s = 0.070). Metamorphic rocks having only 2 samples were not evaluated separately.

Components

All

WA < 1%

WA > 1%

CaO > 37%

CaO < 10%

Na2O MgO Al2O3 SiO2 K2O CaO TiO2 MnO Fe2O3 Li

0.493 0.095 0.204 0.212 0.107 0.272 0.018 0.001 0.086 0.191

0.119 0.103 0.287 0.205 0.355 0.097 0.010 0.001 0.330 0.058

0.889 0.629 0.766 0.943 0.683 0.910 0.613 0.660 0.646 0.987

0.198 0.003 0.000 0.070 0.012 0.116 0.105 0.082 0.006 0.104

0.318 0.033 0.459 0.101 0.065 0.001 0.075 0.061 0.009 0.384

The water absorption ratios of natural building stones that are to be used for external cladding, load-bearing masonry units, non-load-bearing masonry units, copings, sills, lentils, roofing, internal flooring, external pavements, internal walls, kitchens, dining areas, hospitals, cold storage areas are factors for selecting the stone type to be used. Natural building stones that are used especially for exterior applications and interior applications such

Fig. 5. Relationships between physical properties of rocks and water absorption.


Fig. 6. Relationships between the chemical components of examined specimens and water absorption ratios.

265

266


as bathrooms and kitchens must absorb low levels of water and dry fast. Marbles, some limestones and granites are good choices for usage on wet sections of buildings. Because they are more absorbent, travertines can be used for exterior applications because they can dry fast. Due to their porous structure, bacterias may breed in travertines and this may present a challenge to the desired hygienic conditions, so the usage of travertines in interior applications is inconvenient. While pink andesites have similarly fast drying features, because of their strength values as observed in literature, instead of covering applications like travertines, gardening applications would be more convenient for pink andesites. For the purpose of determining the water absorption ratios of natural building stones with different properties, it is maintained that 48 h standard experiment duration may not be the ideal for every natural building stone type, and it would be better if the duration in the water were to be extended until the water

absorption ratio for all natural building stones is fixed. This duration may range from 24 h to 144 h. Similarly, when the specimens are dried they must be dried until they have a fixed weight, and constant drying durations must be avoided. 3.2. Chemical analysis results and relationships with water absorption In this study, the effects of the chemical components of rocks employed in experiments on their water absorption ratio were also investigated. Firstly, the relationships between each chemical component and water absorption ratios were investigated. Then, due to the fact that a high degree of correlation was not observed, water absorption ratios were classified as lower than 1 and higher than 1 for natural building stones. Also, due to high differences in CaO values, another classification was made as CaO > 37% versus CaO < 10%. According to these classifications, the relationship

Fig. 7. Relationships between chemical properties and water absorption ratios which are higher than 1.


Fig. 8. Relationships between trace elements and water absorption ratio.

267

268


Table 7 Mineral percentage of volcanic originated specimens and water absorption ratios. WA Ratio (%) Volcanics Plagioclase Biotite Amphibole Pyroxene Quartz Orthoclase Other minerals

3.99 Pink andesite 63 10 10 9 0 0 8

3.24 Gray andesite 68 12 14 0 0 0 6

0.37 Granite 20 9 6 0 31 28 6

0.24 Green granite 60 0 8 23 0 0 9

Total

100

100

100

100

Fig. 9. Relationships between plagioclase, amphibole and biotite mineral percentages and water absorption ratio.

between water absorption ratios and chemical compositions were investigated. The results are given in Table 6. In addition, the graphs displaying the relationship between chemical composition ratios and water absorption ratios are presented in Fig. 6 and the graphs showing the relationship between water absorption ratios of natural building stones which are higher than 1 and their chemical properties are given in Fig. 7. When Fig. 6 is examined, it is observed that the chemical components of all natural building stones of different origins and types do not have direct effects on water absorption. The strongest relationship was observed with Na2O (R2 = 0.453), and the rest were found to be much lower, varying between 0.038 and 0.372. However, considering the type of natural building stones separately, similarly, relationships were found to be low. R2 values were found between 0.025 (CaO) and 0.521 (LOI) for igneous rocks and 0.014 (Al2O3) and 0.542 (TiO2) for sedimentary rocks. Metamorphic rocks having only 2 samples were not evaluated separately. When Fig. 7 is examined, it is apparent that for specimens with water absorption ratios higher than 1, there was a strong relationship between chemical components and water absorption ratios. As result of examinations done on specimens with water absorption ratios higher than 1, the strongest relationships were found for loss on ignition, SiO2, CaO and Na2O with coefficients of 0.987, 0.943, 0.910, 0.889 respectively. According to Table 6, for specimens with water absorption ratios lower than 1, the strongest relationship was observed for (R2 = 0.355) K2O, while the coefficient for the rest vary between 0.001 and 0.330. As a result, for specimens with water absorption ratios lower than 1, no relationships were found to exist between chemical analysis values and water absorption values. As a result of the classification made due to the high level of difference in CaO values (CaO > 37% and CaO < 10%), it was observed (as it can be seen in Table 6) that only weak relationships exist between chemical components and water absorption ratios. In this study, beside the main chemical components, the relationship between the trace elements and water absorption were also investigated. Examinations of the relationships between large amounts of trace elements with respective water absorption ratios as well as the related graphs are provided in Fig. 8. When Fig. 8 is examined, considering all specimens, trace elements seem to have no effect on water absorption ratio. But investigating trace elements taking in account their rock origins seems to bear interesting results. The rocks were classified into two groups as igneous and carbonate rocks. Sedimentary and metamorphic rocks were evaluated together as carbonate rocks. In specimens with volcanic origins, the most interesting trace elements were found to be Zn and Zr which had the high correlation coefficients 0.986 and 0.942 respectively. Ga (0.743) and Ce (0.742) had respectively high coefficients as well. For Cu and Ni, the coefficients were found as 0.349 and 0.432, respectively. The rest of the trace elements had much lower correlational coefficients. As can be seen also from Fig. 8 that there are some very low correlations between water absorption of carbonates rocks and Ni (R2 = 0.344), Ga (R2 = 0.309) and As (R2 = 0.298). In addition, no

Table 8 Mineral percentage of sedimentary and metamorphical originated specimens and water absorption ratios. WA ratio% Sedimentaries metamorphics Calcite Aragonite Dolomite Quartz Other minerals

1.00 Hazar pink 91 5 1 0 3

0.44 Daisy 89 7 2 0 2

0.20 Sivrihisar beige 94 3 1 0 2

0.27 Ag˘rı onyx 35 61 2 0 2

0.12 Mug˘la milas 98 0 0 0 2

0.07 Afyon gri 87 7 2 0 4

1.42 Travertine 30 65 0 2 3

Total

100

100

100

100

100

100

100


relationships were found with other trace elements. According to these results, it can be said that trace elements have not significant effect on water absorption of carbonates rocks. Karaca [3], studying the effects of the chemical composition of natural building stones on water absorption, states that there are two important factors affecting water absorption and drying durations: MgO content and porosity. With increases in MgO content and porosity, water absorption and drying durations become longer. It is also stated that this effect occurs in different magnitudes with different natural building stones and MgO content is more effective than porosity. The reason behind this is stated to be the fact that Mg ions are smaller than Na and Ca ions. Mg ions have stronger reactions with water molecules due to their stronger charge loads. A relationship between water absorption (g) and MgO content (%) has also been observed. But in that study, it is also stated that MgO levels have no effect on water absorption. Also when the relationship between MgO content in all specimens and water absorption ratios is investigated, it is observed that MgO has a much lesser effect on that case considering the other chemical contents. When Table 5 is examined, considering all specimens, MgO has a correlation coefficient of R2 = 0.095, and that also indicates this is the case. Although the highest effect (R2 = 0.629) MgO has on water absorption is when specimens with water absorption values higher than 1 are considered, it is still lesser than the coefficients of the other components. Thus, it is difficult to state with confidence that MgO content is an important factor affecting water absorption. To determine the exact magnitude of the relationship between chemical analyses and water absorption, analyses and tests need to be performed on numerous specimens of different types. This study only indicates some important clues as regards this phenomenon. 3.3. Mineralogical and petrographical analyses results and relationships with water absorption For the purpose of determining the effect of mineralogical structure on the water absorption and drying characteristics of natural building stones, rocks are classified as: (1) volcanically originated and (2) sedimentary and metamorphically originated, and Tables 6 and 7 display the water absorption ratios and mineralogical compositions of each category separately. While andesites and granites are categorized as volcanic specimens, limestones, travertines, onyx and marbles are categorized as sedimentary and metamorphical specimens. With this method, it is possible to evaluate the different types of rocks separately. Adana Conglomerate specimen was not included in evaluation due to its dissimilar structure. As seen in Table 7, plagioclase, biotite and amphibole minerals were taken into account in order to evaluate the relationship between minerals’ percentages composing volcanic originated rocks and water absorption ratios. Graphs indicating the relationship between these minerals and water absorption ratios are given in Fig. 9. When Fig. 9 is examined, plagioclase and amphibole mineral contents seem to have no effects on water absorption ratio, considering their R2 values respectively, 0.320 and 0.308. Though biotite percent seems to have a high relationship with water absorption (R2 = 0.999). Thus, when biotite mineral percentage increases, an increase in water absorption is also observed. The decrease observed in water absorption after 12% biotite content is another case to investigate. As can be seen in Table 8, for the purpose of determining the relationship between the minerals’ percentages composing sedimentary and metamorphical originated rocks and water absorption ratios, only calcite and aragonite minerals which are common in all rock specimens can be taken into account. Graphs

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Fig. 10. Relationships between calcite and aragonite mineral percentages and water absorption ratio.

showing the relationship between these minerals and water absorption rations are given in Fig. 10. When Fig. 10 is examined, no meaningful relationship can be found between calcite and aragonite mineral percentages and water absorption ratio. It is understood that there have been no studies focusing on the relationship between the mineral structures of natural building stones and water absorption ratios after the literature research. Although the mineral structure types of natural building stones cannot be taken into account when considering the usage areas of current water absorption ratio informations, they are still to be studied in order to understand the water absorption characteristics completely. In addition, a natural material consisting of minerals with relationship of a very low or a very high degree to water absorption will be always important in the composite material production stage. 4. Discussion and conclusion Results obtained from the studies done for determining the water absorption characteristics of natural building stones with different composition, structure and texture properties, determining the parameters affecting the water absorption ratio and obtaining the drying features of natural building stones are presented below: Natural building stones that absorb less water dry as fast as expected and the ones that absorb more water take more time to dry. It should be considered that the porosity of more water absorbing stones is also an accelerating factor for the drying process. The first 24 h are very important for water absorption and drying. The least water absorbing natural building stone is determined to be marble (0.07–0.12%), granite (0.24–0.37%), onyx (0.27%), conglomerate (0.33%) and some beiges

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(0.20–0.44%) also have low ratios for water absorption. While travertines absorb more than these stones (1.42%), the most water absorbing stones are determined to be andesites (3.24–3.99%). Considering all natural building stones, apparent density as well as open and total porosity properties is highly related with water absorption ratio. As porosity increases and as apparent density decreases, the water absorption increases. The chemical components of all natural building stones of different origins and types do not have direct effects on water absorption. But, high relationships are only found between loss on ignition (LOI), SiO2, CaO and Na2O percentages and water absorption ratios for specimens with a water absorption ratio higher than 1. Although a relationship cannot be found between trace elements in examined all specimens and water absorption ratios, Zn and Zr percentages for volcanic originated rocks seem to have high relationships with water absorption ratios. An increase in those elements is observed to cause also an increase in water absorption ratio. However there are no significant relationships between water absorption of carbonates rocks and trace elements. Although Karaca [3] states that MgO content directly the water absorption ratio to a greater degree than rock porosity, according the study done, this is not the case and MgO content has no significant effects on water absorption ratio. When the effects of natural building stones’ mineralogical structures on water absorption ratio were investigated, Biotite in volcanic originated rocks is observed to have a high relationship to water absorption ratio (R2 = 0.999). There are no other meaningful relationships between examined minerals and water absorption ratio other than the case of Biotite.

Acknowledgements This study is supported the by Scientific Research and Development Office of Hacettepe University (Project No.: 012D11602003).

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