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Testing Standards for Sandstone, Lime stone, Marble and Slate

Praveena Das Jennifer*, G.M.Nagaraja Rao** P.C.Nawani @

1National Institute of Rock Mechanics, Kolar Gold Fields - 563 117, Karnataka, India

1. Introduction

Dimension stone includes granite, sandstone, limestone, marble and slate. They can be in the form of tiles, slabs, circle, steps etc. They differ in their properties, colors and textures, and usage depending on the application. In today’s building environment, the emphasis is on safe, permanent, low maintenance products, of which stone leads the list in the minds of architects, designers, and consumers worldwide. Before putting the material into usage it is prerequisite to ascertain whether the material is having the basic engineering properties or not. Without a consistent, realistic set of standards and testing procedures for stone products, the stone industry as a whole would be in disarray. The standards that have been developed and set in place for these products are important tools to help protect end users, individual companies, and the industry from negative effects related to product failures. Materials standards help to prevent the use of stone products for unsuitable applications. These standards also serve as benchmarks for quality limits of products. To determine the properties of stones, two important International Standards are available

1. ASTM Standards 2. European Standards

These standards give the procedures for determining the various properties and also property value for accepting the stone. European standards give detailed methodology for CE marking. Every one is more or less familiar with ASTM standard, but European standards are of recent one.

In this paper we shall discuss about the required tests to be carried out for sandstone, limestone, marble, and slate as per ASTM and European Standards for better marketability of the stone.

2. International Standards 2.1 ASTM (American Society for Testing and Materials) Standard The following American Standards (Table 1) gives the specification (i.e. property values) for sandstone, lime stone, marble and slate, which may be used as acceptance criteria for each of the stone.

• * Scientist, ** Corresponding author • @ Director

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TABLE 1 Code Title C568 Specifications for Limestone Dimension Stone C503 Specifications for Marble Dimension Stone (Exterior) C616 Specifications for Quartz-based Dimension Stone (Sandstone) C620 Specifications for Slate Dimension Stone C406 Specifications for Roofing Slate

In the following tables, the properties required to be tested and the test code reference as per the ASTM standard for sandstone, limestone, marble and slate for the benefit of quarry owners and suppliers of dimensional stones, have been given.

2.1.1 SANDSTONE-Requirement TABLE 2

Sl no. Property Test

Requirement* ASTM

test Code

1. Absorption, max, (%) 8 C97

2. Density, min, (kg/m3) 2003 C97

3. Modulus of rupture, min, (MPa) 2.4 C99

4. Compressive strength, min, (MPa) 27.6 C170

5. Abrasion resistance subjected to foot traffic, min, (H) 2a C241/

C1353 a Not recommended for paving in areas subject to heavy foot traffic * for sandstone with 60% minimum free silica content 2.1.2 LIMESTONE - Requirements

ASTM has classified limestone into three categories according to their density ranges as follows:

TABLE 3

Type 1: limestone having a density ranging from 1760 to 2160 kg/m3 - Low Density

Sl no. Property Test

Requirement ASTM test

Code 1. Absorption, max, (%) 12 C97 2. Density, min, (kg/m3) 1760 C97 3. Modulus of rupture, min, (MPa) 2.9 C99 4. Compressive strength, min, (MPa) 12 C170

5. Abrasion resistance subjected to foot traffic, min, (H) 10 C241/

C1353

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TABLE 4

Type 2: limestone having a density ranging from 2160 to 2560 kg/m3 - Medium Density

Sl no. Property Test

Requirement ASTM test

Code 1. Absorption, max, (%) 7.5 C97 2. Density, min, (kg/m3) 2160 C97 3. Modulus of rupture, min, (MPa) 3.4 C99 4. Compressive strength, min, (MPa) 28 C170

5. Abrasion resistance subjected to foot traffic, min, (H) 10 C241/

C1353 TABLE 5

Type 3: limestone having a density greater than 2560 kg/m3 - High Density

Sl no. Property Test

Requirement ASTM test

Code 1. Absorption, max, (%) 3 C97 2. Density, min, (kg/m3) 2560 C97 3. Modulus of rupture, min, (MPa) 6.9 C99 4. Compressive strength, min, (MPa) 55 C170

5. Abrasion resistance subjected to foot traffic, min, (H) 10 C241/

C1353 2.1.3 MARBLE- Requirements TABLE 6

Sl no. Property Test

Requirement ASTM test

Code 1. Absorption, max, (%) 0.20 C97 2. Density, min, (kg/m3) 2595 C97 3. Modulus of rupture, min, (MPa) 7 C99 4. Compressive strength, min, (MPa) 52 C170

5. Abrasion resistance subjected to foot traffic, min, (H) 10 C241/

C1353 6. Flexural strength, min, (MPa) 7 C880

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2.1.4 SLATE -Requirements

ASTM has classified slate into two categories according to its use as follows:

Type 1: slate used for Exterior applications TABLE 7

Sl no. Property Test

Requirement ASTM test

Code

1. Absorption, max, (%) 0.25 C121

2. Modulus of rupture, min, (MPa) Across grain Along grain

62.1 49.6 C120

3. Abrasion resistance subjected to foot traffic, min, (H) 8.0 C241/

C1353 4. Acid resistance, max, (mm) 0.38 C217

Type 2: slate used for Interior applications

TABLE 8

Sl no. Property Test

Requirement ASTM

test Code

1. Absorption, max, (%) 0.45 C121

2. Modulus of rupture, min, (MPa) Across grain Along grain

49.6 37.9 C120

3. Abrasion resistance subjected to foot traffic, min, (H) 8.0 C241/

C1353 4. Acid resistance, max, (mm) 0.64 C217

2.2. Properties for intended use Depending on the application or usability of the dimensional stone, the test properties to be determined are listed in the following table. TABLE 9

Sl No

Test Method →

Absorption, (%)

Density, (kg/m3)

Compressive strength,

(MPa)

Flexural strength,

(MPa)

Abrasion resistance subjected

to foot traffic, (H)

Acid resistance,

(mm)

1. External Cladding - -

2.

Load - Bearing Masonry units

- - -

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Sl No

Test Method →

Absorption, (%)

Density, (kg/m3)

Compressive strength,

(MPa)

Flexural strength,

(MPa)

Abrasion resistance subjected

to foot traffic, (H)

Acid resistance,

(mm)

3.

Non load - Bearing Masonry units

- - - -

4. Copings - - - - 5. Sills/ Lintels - - - 6. Roofing - 7. Internal

Flooring -

8. External Pavements - -

9. Counter Tops - - -

10.

Food Areas (Commercial, Residential, kitchen and Dining areas)

- -

(flooring only)

3. EUROPEAN STANDARDS

European standards do not give separate standard for lime stone, sandstone and marble. The standards are broadly classified in to two groups:

1. Standards for granite, lime stone, sandstone and marble. 2. Standards for slate.

The standards which are applicable for Granite are also applicable to lime stone, sandstone and marble are given in TABLE 10 TABLE 10 European Standards for Natural Stones prepared by the CEN TC 246 Code Title EN 12371 Determination of Frost Resistance EN 14581 Determination of Thermal Dilatation Coefficient EN 14579 Determination of the Sound Speed Propagation EN 14157 Determination of Abrasion Resistance EN 14205 Determination of Knoop Hardness EN 14066 Determination of Thermal Shock Resistance EN 14231 Determination of Slip Coefficient EN 14580 Determination of Static Elastic Modulus EN 14158 Determination of Rupture Energy EN 13373 Determination of Geometric Characteristics on Units EN 14147 Determination of Ageing by Salt Mist

EN13919 Determination of Resistance to Ageing Actions by SO2 in presence of Humidity

EN 14146 Determination of Dynamic Elastic Modulus (by Fundamental Resonance Frequency)

EN 13161 Determination of Flexural Resistance (under Constant Moment)

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EN 1467 Rough Blocks - Specifications EN 1468 Semi-Finished Products (Rough Slabs) - Specifications EN 12057 Finished Products, Modular Tiles - Specifications EN 1469 Finished Products, Slabs for Cladding - Specifications EN 12059 Finished Products, Dimensional Stone Work - Specifications EN 12058 Finished Products, Slabs for Floors and Stairs - Specifications EN 1925 Determination of Water Absorption Coefficient by Capillarity

EN 1936 Determination of Real Density and Apparent Density and of Total and Open Porosity

EN 1926 Determination of Compressive Strength EN 12370 Determination of Resistance to Salt Crystallization EN 12372 Determination of Flexural Strength under Concentrated Load EN 12407 Petrographic Examination EN 12440 Denomination Criteria EN 13364 Determination of the Breaking Load at the Dowel Hole EN 12670 Terminology EN13755 Determination of Water Absorption at Atmospheric Pressure EN = European Norm EN 12326 is one of the series of standards for slate and stone products for roofing, the details are as follows. TABLE 11 Sl no. Title Code no.

1. Slate and Stone products for Discontinuous Roofing and Cladding - Part 1 : Product Specification EN 12326 - 1

2. Slate and Stone products for Discontinuous Roofing and Cladding - Part 2 : Methods of test EN 12326 - 2

EN = European Norm According to EN 12326-2:2000 the following tests are to be carried out depending on the application. TABLE 12

Sl no. Property to be tested

1. Failure load in bending 4. Sulfur dioxide exposure test

2. Water absorption 5. Thermal cycle test

3. Freeze - thaw test 3.1 Determination of failure load in bending Tests are carried out on prepared test pieces to measure the failure load in bending.

From the results, the modulus of rupture is calculated.

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3.2 Water absorption test Dried test pieces are immersed in water at ambient temperature for 48 hrs and the absorption is determined from the difference of the wet and dry mass. The samples are dried to a constant weight in an oven at 105 degree C +/- 5 degree C over a period of 48 hours. The samples are submerged in distilled water in a suitable receptacle provided with a reflux condenser and are kept gently and continuously boiling for 48 hours. After cooling in air for 5 min they are placed in cold water and allowed to stand for 30 minutes in the room. At the end of this period the samples are removed from the water bath one at a time, surface dried with damp cloth and weighed. Absorption of water is calculated by using the formula given in the relevant standard.

3.3 Freeze - thaw test Test samples are prepared as given in the Standard. Divide the paired test pieces into two lots, the test lot and the control lot. Conduct the failure load in bending test( refer standard EN12372:1999/EN13161:2001) on the control lot. Immerse the test lot in the water bath at (23+5) 0C for 48 hrs. When soaking is complete, place the test pieces in the freezing cabinet until the temperature has held (-20+2) 0C for at least 3 hrs. Then replace the test pieces in the water bath for at least 1 hr. This constitutes 1 cycle. Repeat the freeze-thaw cycle 99 times to give a total of 100 cycles. When the 100 cycles are complete dry the test pieces in the oven at (110+5) 0C for (17+2) hr and then cool to ambient temperature. Carry out the bend strength test on these samples. Calculate the mean value and standard deviation of the modulus of rupture of the test lot and compare with the mean value and standard deviation of the control lot using a one-sided student’s t-test at the 2.5% significance level.

3.4 Sulfur dioxide exposure test

EN has classified Sulfur dioxide exposure test for slates into two categories according to its calcium carbonate content as follows: a.) Sulfur dioxide exposure test for slates with a calcium carbonate content less than

20% b.) Sulfur dioxide exposure test for slates with a calcium carbonate content 20% or

more a.) Sulfur dioxide exposure test for slates with a calcium carbonate content less than 20% Pairs of test pieces sawn from roofing slates, one dry and one soaked in water, are exposed to sulphur dioxide atmospheres at each of two concentrations for upto 21 days. Depending on the physical changes observed during or on completion of the exposure, a code as specified in EN 12326-1:1999 is assigned to the slates. b.) Sulfur dioxide exposure test for slates with a calcium carbonate content 20% or more The softening of slate resulting from exposure to an atmosphere of moist sulfur dioxide is determined by scraping the surface under a standard load before and after exposure, and measuring the increased depth of the scratches.

3.5 Thermal cycle test Test pieces sawn from slates are subjected to cycles of drying at (110+5) 0C and immersion in water at (23+5) 0C. On completion of 20 cycles the test pieces are

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inspected for physical changes indicative of the presence of harmful mineral components. A code, as specified in TC128 WI 00128032 is assigned to the slates. 3. Comparison between the ASTM Standards and the European Standards Although both these standards are widely used for characterizing the stone, there exist certain differences among these standards, and some of them are presented in the TABLE 13.

TABLE 13

Sl no. ASTM Standards European Standards

1. The ASTM Standards are user friendly and have been in use, since ages.

The European standards have recently come into use, a little complicated, not user friendly.

2.

The accepted test values are clearly mentioned in the standards for each of the Dimensional stone individually along with their ASTM code of reference.

The accepted test values are not mentioned in the standards for each of the Dimensional stone.

3.

Limited tests have been recommended and the existing facilities in the materials testing laboratory can also be used for testing of dimensional stones.

A large number of tests are recommended, requires heavy capital investment to carryout some of the tests.

5. Methodology of CE marking is not available. Methodology is available for CE marking.

6. Test methodology is not available for Freeze thaw resistance and Slip resistance.

Test methodology is available for Freeze thaw resistance and Slip resistance. However the methodology of freeze thaw test is too complicated.

Testing Standards are available for the following properties for each particular stone:

Testing Standards are available for the following properties common for all stones:

Physical Properties Absorption Specific gravity

Real Density, Apparent Density Total and open Porosity Water Absorption at Atmospheric Pressure and by Capillarity Thermal Dilation Coefficient Sound Speed Propagation

7.

Mechanical Properties Flexural strength flexural modulus of elasticity Modulus of rupture Compressive strength

Flexural Resistance under Concentrated load Flexural Resistance (under Constant Moment) Compressive strength Static & Dynamic Elastic Modulus Knoop Hardness Rupture Energy

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Durability Properties Abrasion resistance Weather resistance (for slate only)

Abrasion Resistance Breaking Load at Dowel Hole Frost Resistance Thermal shock resistance Resistance to Ageing Actions by SO2 in presence of humidity Resistance to ageing by Salt mist Resistance of Salt Crystallisation

Design Standards 1. Structural performance of exterior dimension stone cladding systems by uniform static air pressure difference. 2. Static coefficient of friction of ceramic tile and other like surfaces by the horizontal dynamometer pull meter method. 3. Strength of individual stone anchorage in dimension stone. 4. Guide for design, selection and installation of exterior dimension stone anchors and anchoring systems.

Design Standards are not available.

Surface finish properties Standard is not available

Slip resistance

8. No. of samples required for determining each property is about 3 to 5 numbers.

Recommends large number of samples to be tested for each property, about 10 to 20 numbers.

Calculation of Flexural Strength : a.) Modulus of rupture

(3 point bend test) R = 3*F*l/2*b*h2 (MPa)

a.) Flexural Resistance under Concentrated load-( 3 point bend test)

Rtf = 3*F*l/2*b*h2 (MPa)

b.) Flexural strength of stone (4 point bend test)

σ = 3*F*L/4*b*h2 (MPa)

b.) Flexural Resistance (under Constant Moment) - 4 point bend test

Rtc = F*L/b*h2 (MPa)

9.

Common notations: F = failure load in N ; L = span in mm ; l = length of span in mm ; h = thickness in mm ; b = width of specimen in mm ; ∆ = the average net mid span deflection in mm ; Rtf = Flexural strength under conc. load ; Rtc = Flexural strength @ const. moment

10. No particular formula is available for the calculation of breaking load.

The Breaking load for Slabs can be calculated from flexural stress (Rtf ) value it self, the formula is as below: P = Rtf *W*t2/1500*L*1.6 W = width of slab, mm ; L = length of span, mm ; t = thickness of slab, mm ; P = breaking load , (kN)

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Note: In both the Standards, the standards for physical properties like Gloss / Reflectivity and Hardness are not available. 5. Other Standards Apart from the ASTM and European Standards, other testing standards are also available and are briefly mentioned in this section. 5.1 Australian testing standards Two sets of standards are available and are given below. TABLE 14: CSIRO (Commonwealth Scientific and Industrial Research Organization) ‘BEST’ TEST Methods for Evaluating Stone Tiles CSIRO METHOD BEST - 0 Introduction CSIRO METHOD BEST - 1 Determination of petrography of Stone Tiles

CSIRO METHOD BEST - 2 Determination of Water absorption, Apparent porosity, and Bulk density of stone Tiles

CSIRO METHOD BEST - 3 Determination of Flexural Strength of Stone Tiles CSIRO METHOD BEST - 4 Determination of Impact Resistance of Stone Tiles CSIRO METHOD BEST - 5 Determination of Scratch Hardness of Stone Tiles

CSIRO METHOD BEST - 6 Determination of Resistance to abrasion of Stone Tiles (Capon method)

CSIRO METHOD BEST - 7 Determination of Co-efficient of Thermal Expansion of Stone Tiles

CSIRO METHOD BEST - 8 Determination of Resistance to Thermal Shock of Stone Tiles

CSIRO METHOD BEST - 9 Determination of Dimensional Stability of Stone Tiles CSIRO METHOD BEST - 10 Determination of Frost Resistance of Stone Tiles CSIRO METHOD BEST - 11 Determination of Chemical Resistance of Stone Tiles CSIRO METHOD BEST - 12 Acid Immersion test for Stone Tiles CSIRO METHOD BEST - 13 Determination of Stain Resistance of Stone Tiles CSIRO METHOD BEST - 14 Determination of Weatherability of Stone Tiles

TABLE 15: Australian Stone Standards 1. AS/NZS 3661.2:1994 Slip resistance of pedestrian surfaces - Guide to the

reduction of slip hazards

2. AS/NZS 4586:2004 Slip resistance classification of new pedestrian surface materials

3. AS/NZS 4663:2004 Slip resistance measurement of existing pedestrian surfaces

4. HB 197:1999 An introductory guide to the slip resistance of pedestrian surface materials

8. AS 4204-1994 Headstones and cemetery monuments

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5.2 Chinese Standards: A list of Chinese standards are given in Table 16 TABLE 16 1. GB/T 13890-1992 Terms for natural facing stone 2. GB/T 14319-1993 Super finishing stone 3. GB/T 14320-1993 Vitrified force-honing stone 4. GB/T 14685-2001 Pebble and crushed stone for building 9. GB/T 17670-1999 Unified catalogue for natural stone 10. GB/T 18250-2000 Test method for performance in plane deformation of curtain

wall's 11. GB/T 9966.7-2001 Test methods for natural facing stones--Part 7: Test method

for strength of individual stone anchorages 12. GB/T 9966.8-2001 Test methods for natural facing stones--Part 8: Test method

for structural performance of dimension stone cladding systems by uniform static pressure difference

5.3 Indian Standard-Bureau of Indian Standards (BIS) In India, Bureau of Indian standard has recommended a list of standards for stones and is given in Table. TABLE 17 IS 1121 : Part 1 : 1974 Methods of test for determination of strength properties of

natural building stones: Part I Compressive strength

IS 1121 : Part 2 : 1974 Methods of Test for Determination of Strength Properties of Natural Building Stones - Part II : Transverse Strength

IS 1121 : Part 3 : 1974 Methods of Test for Determination of Strength Properties of Natural Building Stones - Part III : Tensile Strength

IS 1122 : 1974 Method of test for determination of true specific gravity of natural building stones

IS 1123 : 1975 Method of identification of natural building stones

IS 1124 : 1974 Method of test for determination of water absorption, apparent specific gravity and porosity of natural building stones

IS 1125 : 1974 Method of test for determination of weathering of natural building stones

IS 1126 : 1974 Method of test for determination of durability of natural building stones

IS 1706 : 1972 Method for determination of resistance to wear by abrasion of natural building stones

IS 1805 : 1973 Glossary of terms relating to stones, quarrying and dressing

IS 4121 : 1967 Method of test for determination of water transmission rate by capillary action through natural building stones

IS 4122 : 1967 Method of test for surface softening of natural building stones by exposure to acidic atmospheres

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IS 4348 : 1973 Methods of test for determination of permeability of natural building stones

IS 8381 : 1977 Recommended practice for quarrying stones for construction purposes

IS 8759 : 1977 Code of practice for maintenance and preservation of stones in building

IS 3622 : 1977 Specification for sandstone (slabs and tiles) IS 1128 : 1974 Specification for Limestone (Slab and Tiles) IS 1130 : 1969 Specification for marble (blocks, slabs and tiles) IS 6250 : 1981 Specification for Roofing Slate Tiles

6. CONCLUSION

NIRM laboratory is equipped with various testing facilities to carry out the tests as per the International standards. Presently few of the industries are using the NIRM facilities. With the above list of properties they will be able to market their product in a better way. Data generation on Indian stones is the prime requirement for improving the exporting of stones. It is to be understood it is not only aesthetic appearance i.e color of the stone, other engineering properties play a dominant role in selecting the stone for a particular application.

7. BIBLIOGRAPHY

1. ASTM standard

2. BIS Standards, European Standards, Australian Stone Standards and Chinese Standards

3. Standards and Specifications for Stone Products - 2007 Marble Institute of America 4.European Standards And CE Marking on Stone Construction Products - Angelica Frisa Morandini, Dipartimento Georisorse e Territorio,CNR IGAG – Politecnico di Torino 5. International standards on dimensional stone - Dott.ssa Paola Blasi ,Internazionale Marmi Macchine Carrara S.p.A., Italy 6. Selective guide to the Specification of Dimension Stone - Geoff Quick CSIRO Building, Construction and Engineering, Highett, Victoria, Australia, 3190. 7. A compilation of international standards for testing of material - Prodomea team – Hashemite University 2004 8. Guide for Testing of Dimension stone as per ASTM and European Standards - G.M.Nagaraja Rao, S.K.Mohanty, S.Udayakumar, National Institute of Rock Mechanics, KGF