Lecture 3. Geological materials - MyCourses · Lecture 3. Geological materials ... •...

CIV-E1010 Building Materials Technology (5 cr) (1/19)

Lecture 3. Geological materials

Prepared by:Fahim Al-Neshawy, D.Sc. (Tech.)Aalto University School of EngineeringDepartment of Civil EngineeringA: P.O.Box 12100, FIN-00076 Aalto, Finland


Table of ContentsLecture 3. Geological materials................................................................................................................. 1

3.1 Classification of geological materials ............................................................................................. 3

3.1.1 Geological classification ........................................................................................................... 3

3.1.2 Physical classification ............................................................................................................... 7

3.1.3 Chemical classification ............................................................................................................. 8

3.2 Building stones ................................................................................................................................. 8

3.2.1 Properties of stones ................................................................................................................. 8

3.2.2 Tests on stones ....................................................................................................................... 10

3.2.3 Uses of building stones .......................................................................................................... 13

3.3 Common building stones ............................................................................................................... 15

3.3.1 Basalt and Trap (Trapp) ......................................................................................................... 15

3.3.2 Granite .................................................................................................................................... 15

3.3.3 Sand stone .............................................................................................................................. 16

3.3.4 Slate ......................................................................................................................................... 17

3.3.5 Laterite .................................................................................................................................... 17

3.3.6 Marble ..................................................................................................................................... 18

3.3.7 Gneiss ...................................................................................................................................... 18

3.3.8 Quartzite ................................................................................................................................. 19


3.1 Classification of geological materials

Rock: The portion of the earth’s crust having no definite shape and structure

Stone: A natural, hard substance formed from minerals and earth material which are present in rocks.

Stones used for civil engineering works may be classified in the following three ways:

· Geological classification· Physical classification· Chemical classification· Classification according to aggregates’ size

3.1.1 Geological classification

Based on their origin of formation stones are classified into three main groups—Igneous, sedimentaryand metamorphic rocks, shown in Figure 1 (1)

Figure 1. Classification of rocks

Different statistical calculations have been made showing the distribution of the major rock groups. Ingeneral, the major rock groups, in decreasing percentage, are: 65 % igneous, 27 % metamorphic, and8 % sedimentary. These rock types form an interconnected geologic rock cycle as shown in Figure 2.The rocks do not last forever, and there is a cyclical development and transformation between thevarious rock types. The processes include the uplift of regions and exposure of igneous ormetamorphic rocks, which then become prone to surface erosion and provide particles for sedimentsand sedimentary rocks. When sedimentary rocks are subjected to higher pressures and temperatures,they shift into the metamorphic realm, and mineral transformations begin. At greater depth, melting

1 Monique Gafford (2010). Rock Classification. Available online at:http://edtech2.boisestate.edu/gaffordm/502/conceptmap.html


occurs, and both metamorphic and sedimentary rocks become parts of the magma system and theigneous province. (2)

Figure 2. The geologic rock cycle describes the relationship of the various rock groups to each other andshows the possible pathways of the different rock types (2).

3.1.1.1 Igneous rocks

o These rocks are formed by cooling and solidifying of the rock masses from their moltenmagmatic condition of the material of the earth.

o Generally igneous rocks are strong and durable.o Granite, trap and basalt are the rocks belonging to this categoryo Granites are formed by slow cooling of the lava under thick cover on the top. Hence

they have crystalline surface. The cooling of lava at the top surface of earth results intonon-crystalline and glassy texture.

o If the rock is formed from magma it is called an intrusive igneous rock. If the rock isformed from lava it is called an extrusive igneous rock.

2 Siegesmund and Snethlage (2014). Stone in Architecture - Properties, Durability. Chapter 2: Building Stones


Figure 3. Collections of Igneous rocks (3).

3.1.1.2 Sedimentary rocks

Sedimentary rocks are formed when sediment compacts together and the particles are cementedtogether. There are three types of sedimentary rocks:

o Clastic rocks form when rock fragments are squeezed and cemented together.Examples of clastic rocks are shale, sandstone, conglomerate, and breccia.

o Organic rocks form when the remains of plant or animals are deposited in thicklayers and become cemented together. Coal is an example of organic rock.

o Chemical rocks are formed when minerals that are dissolved in solution crystallize.Rock salt and limestone are examples of a chemical rocks.


Figure 4. Collection of sedimentary rocks (3).

3.1.1.3 Metamorphic rocks

Metamorphic rocks are formed when heat and pressure below Earth's surface change a rock.Metamorphic rocks can be either foliated or non-foliated.

o Foliated rocks are metamorphic rocks that have their grains arranged in parallellayers or bands. Slate is an example of a foliated rock. Before becoming ametamorphic rock slate's parent rock is shale.

o Non-foliated metamorphic rocks are rocks that the grains are arranged randomly.Marble is an example of a non-foliated metamorphic rock.

3 Alexandria Darcy, (2015). My feelings about rock names. Available online at:https://alexandriadarcy.com/2015/02/15/my-feelings-about-rock-names/


Figure 5. Collection of metamorphic rocks (3).

3.1.2 Physical classification

Physical classification of rocks is based on general structure of rocks. According to this classification,the rocks may be classified as:

· Stratified rocks:o These rocks are having layered structure.o They possess planes of Stratification or cleavage.o They can be easily split along these planes.o Sand stones, lime stones, slate etc. are the examples of this class of stones.

· Unstratified:o The structure of these rocks may be crystalline granular or compact granular.o They cannot be split in to thin slab.o Granite, trap, marble etc. are the examples of this type of rocks.

· Foliated:o These rocks have a tendency to be split up in a definite direction only.o The direction need not be parallel to each other as in case of stratified rocks.o This type of structure is very common in case of metamorphic rocks.


Stratified Rocks Unstratified Rocks Foliated RocksFigure 6. Physical classification of rocks.

3.1.3 Chemical classification

On the basis of the stones’ chemical composition engineers prefer to classify rocks as:

· Silicious rocks:o The main content of these rocks is silica.o They are hard and durable.o Examples of such rocks are granite, trap, sand stones etc.

· Argillaceous rocks:o The main constituent of these rocks is argil i.e., clay.o These stones are hard and durable but they are brittle.o They cannot withstand shock.o Slates and laterites are examples of this type of rocks.

· Calcareous rocks:o The main constituent of these rocks is calcium carbonate.o Durability depends upon surrounding atmosphere.o Limestone is a calcareous rock of sedimentary origin while marble is a calcareous rock

of metamorphic origin.

3.2 Building stones

3.2.1 Properties of stones

The following properties of the stones should be looked into before selecting them for engineeringworks:

(i) Structure: The structure of the stone may be stratified (layered) or unstratified. Structuredstones should be easily dressed and suitable for super structure. Unstratified stones arehard and difficult to dress. They are preferred for the foundation works.

(ii) Texture: Fine grained stones with homogeneous distribution look attractive and hencethey are used for carving. Such stones are usually strong and durable.

(iii) Density: Denser stones are stronger. Light weight stones are weak. Hence stones withspecific gravity less than 2.4 are considered unsuitable for buildings.


(iv) Appearance: A stone with uniform and attractive colour is durable, if grains are compact.Marble and granite get very good appearance, when polished. Hence they are used forface works in

(v) Strength: Strength is an important property to be looked into before selecting stone asbuilding block. Standard code recommends, a minimum crushing strength of 3.5 N/mm2

for any building block. Table 1 shows the crushing strength of various stones. Due to non-uniformity of the material, usually a factor of safety of 10 is used to find the permissiblestress in a stone. Hence even laterite can be used safely for a single story building, becausein such structures expected load can hardly give a stress of 0.15 N/mm2. However in stonemasonry buildings care should be taken to check the stresses when the beams(Concentrated Loads) are placed on laterite wall.

Table 1. Crushing strength of common building stones

Name of stone Crushing Strength in N/mm²Trap 300 to 350Basalt 153 to 189Granite 104 to 140Slate 70 to 210Marble 72Sand stone 65Lime stone 55Laterite 1.8 to 3.2

(vi) Hardness: It is an important property to be considered when stone is used for flooring andpavement. Coefficient of hardness is to be found by conducting test on standard specimenin Dory’s testing machine. For road works coefficient of hardness should be at least 17. Forbuilding works stones with coefficient of hardness less than 14 should not be used.

(vii) Percentage wear: It is measured by attrition test. It is an important property to beconsidered in selecting aggregate for road works and railway ballast. A good stone shouldnot show wear of more than 2%.

(viii) Porosity and Absorption: All stones have pores and hence absorb water. The reaction ofwater with material of stone causes disintegration. Absorption test is specified aspercentage of water absorbed by the stone when it is immersed under water for 24 hours.For a good stone it should be as small as possible and in no case more than 5.

(ix) Weathering: Rain and wind cause loss of good appearance of stones. Hence stones withgood weather resistance should be used for face works.

(x) Toughness: The resistance to impact is called toughness. It is determined by impact test.Stones with toughness index more than 19 are preferred for road works. Toughnessindexes 13 to 19 are considered as medium tough and stones with toughness index lessthan 13 are poor stones.


(xi) Resistance to Fire: Sand stones resist fire better. Argillaceous materials, though poor instrength, are good in resisting fire.

(xii) Ease in Dressing: Cost of dressing contributes to cost of stone masonry to a great extent.Dressing is easy in stones with lesser strength. Hence an engineer should look intosufficient strength rather than high strength while selecting stones for building works.

(xiii) Seasoning: The stones obtained from quarry contain moisture in the pores. The strength ofthe stone improves if this moisture is removed before using the stone. The process ofremoving moisture from pores is called seasoning. The best way of seasoning is to allow itto the action of nature for 6 to 12 months. This is very much required in the case of lateritestones.

3.2.2 Tests on stones (4)

To find out the required properties of stones, the following tests can be conducted:

3.2.2.1 Crushing strength test

· Samples of stone is cut into cubes of size 40x40x40 mm sizes of cubes are finely dressed andfinished.

· Maximum number of specimen to be tested is three.· Specimens are placed in water for about 72 hours prior to test and therefore tested in

saturated condition.· Load bearing surface is then covered with plaster of paris of about 5mm thick plywood.· Load is applied axially on the cube in a crushing test machine.· Rate of loading is 14 N/ mm2 per minute.· Crushing strength of the stone per unit area is the maximum load at which the sample crushes

or fails divided by the area of the bearing face of the specimen.

3.2.2.2 Water absorption test

· For the water absorption test cube specimen weighing about 50 grams are prepared and thetest is carried out in the steps given below:

(a) Dry specimen is weighted (W1).(b) Specimen is placed in water for 24 hours.(c) Specimen is taken out from water, the surface is wiped out with a piece of cloth and

weighed (W2).(d) Specimen is suspended freely in water and weighted (W3).(e) Specimen is placed in boiling water for 5 hours. Then taken out, the surface is wiped

with cloth and weighed (W4)

% ℎ =−

× 100 (1)

4 Tests on building stones. Online at: http://theconstructor.org/building/tests-on-building-stones/5552/


% =−−

× 100 (2)

% =−− × 100 (3)

= −(4)

= −(5)

= =

−−

(6)

3.2.2.3 Abrasion test

Abrasion test is carried out on stones which are used as aggregates for road construction. The testresult indicate the suitability of stones against the grinding action under traffic. Any one of thefollowing test may be conducted to find out the suitability of aggregates:

1) Los Angeles abrasion test, shown in Figure 7, which is test is preferred since these test resultsare having good correlation with the performance of the pavements.

2) Deval abrasion test3) Dorry’s abrasion test.

The Los Angeles abrasion test (ASTM C131, C535) evaluates the aggregates’ toughness and abrasionresistance. In this test:

· Aggregates blended to a fixed size distribution are placed in a large steel drum with standardsized steel balls that act as an abrasive charge.

· The drum is rotated, typically for 500 revolutions.· The material is recovered from the machine and passed through a sieve that retains all of the

original material.· The percentage weight loss is the Los Angeles abrasion value:

=ℎ ℎ ℎ

ℎ × 100 (7)

· The following values are recommended for road works:o For bituminous mixes – 30%o For base course – 50%

· This is an empirical test; that is, the test results do not have a scientific basis and aremeaningful only when local experience defines the acceptance criteria.


Figure 7. Los Angeles abrasion machine

3.2.2.4 Impact test

The resistance of stones to impact is found by conducting tests in impacting testing apparatus, shownin Figure 8. The apparatus consists of a frame with guides in which a metal hammer weighing 13.5 to15 kg can freely fall from a height of 380 mm.

Figure 8. Impact test apparatus.

· Aggregates of size 10 mm to 12.5 mm are filled in cylinder in 3 equal layers; each layer beingtamped 25 times.

· The same is then transferred to the cup and again tamped 25 times.· The hammer is then allowed to fall freely on the specimen 15 times.· The specimen is then sieved through 2.36 mm sieve.

(%) =ℎ

ℎ(8)

Table 2. Example of the aggregate impact values for road surfacing.


S.NO Nature of stone impact value1 Exceptionally strong < 10%2 Strong 10% to 20 %3 Satisfactory 20% to 30%4 Weak for road surfacing >30%

3.2.2.5 Acid test.

· A sample of stone weighing about 50 to 100 gm is placed in a solution of hydrophobic acidhaving strength of one percent and is kept there for seven days.

· Solution is agitated at intervals.· A good building stone maintains its sharp edges and keeps its surface free from powder at the

end of this period. If the edges are broken and powder is formed on the surface, it indicatesthe presence of calcium carbonate and such a stone will have poor weathering quality.

· This test is usually carried out on sandstones.

3.2.3 Uses of building stones

Stones are used in the following civil engineering constructions:

i. Stone masonry is used for the construction of foundations, walls, columns and arches.ii. Stones are used for flooring.

iii. Stone slabs are used as damp proof courses, lintels and even as roofing materials.iv. Stones with good appearance are used for the face works of buildings. Polished marbles

and granite are commonly used for face works.v. Stones are used for paving of roads, footpaths and open spaces round the buildings.

vi. Stones are also used in the constructions of piers and abutments of bridges, dams andretaining

vii. Crushed stones with graved are used to provide base course for roads. When mixed withtar they form finishing coat.

viii. Crushed stones are used in the following works also:a. As a basic inert material in concreteb. For making artificial stones and building blocksc. As railway ballast.


Figure 9. Example of using natural stones inbuildings - The entrance of the national museumof finland (5).

Figure 10. Example of using marble as a claddingmaterial - Finlandia Hall building façade.

Figure 11. The main facade of the FinnishNational Theatre made mostly of granite. [Photoby Sanna Parikka](6)

5 Natural stone in city buildings - history of stone construction in south-east Finland. Online at:http://projects.gtk.fi/ENPI/gallery/naturalstone_city_buildings.html6 Sanna-Katja Parikka (2006). National Romanticism in Finnish Architecture. Online at:http://www15.uta.fi/FAST/FIN/CULT/sp-natro.htmlSanna-Katja Parikka, Spring 2006 http://www15.uta.fi/FAST/FIN/CULT/sp-natro.html


3.3 Common building stones (7)

The following are the commonly used building stones:

3.3.1 Basalt and Trap (Trapp)

Figure 12. (A) Basalt rock and (B) Crushed trap rock

· The structure is medium to fine grained and compact.· Colour varies from dark gray to black.· Fractures and joints are common.· Weight varies from 18 kN/m3 to 29 kN/m3.· The compressive strength varies from 200 to 350 N/mm2 (MPa).· Basalt and Trap are igneous rocks.· Basalt and Trap are used as road metals, aggregates for concrete, for rubble masonry

works for bridge piers, river walls and dams and used as pavement.

3.3.2 Granite

Figure 13. Granites

7 The University of Auckland, Geology Rocks and Minerals - Rock identification and classification: Online at:https://flexiblelearning.auckland.ac.nz/rocks_minerals/rocks/index.html

(A) (B)


· Granites are igneous rocks.· colour varies from light gray to pink.· The structure is crystalline, fine to coarse grained.· Granites are hard durable.· Specific gravity is from 2.6 to 2.7 and compressive strength is 100 to 250 N/mm2.· Granites are used primarily for bridge piers, river walls, and for dams. They are used as kerbs

and pedestals. The use of granite for monumental and institutional buildings is common.Polished granites are used as table tops, cladding for columns and wall. They are used ascoarse aggregates in concrete.

3.3.3 Sand stone

Figure 14. Sand stones

· Sand stones are sedimentary rocks, and hence stratified.· Sand stones consist of quartz and feldspar.· Sand stones are found in various colours like white, grey, red, buff, brown, yellow and even

dark gray.· The specific gravity varies from 1.85 to 2.7 and compressive strength varies from 20 to 170

N/mm2. Its porosity varies from 5 to 25 per cent.· Weathering of rocks renders it unsuitable as building stone. It is desirable to use sand stones

with silica cement for heavy structures, if necessary. They are used for masonry work, fordams, bridge piers and river walls.


3.3.4 Slate

Figure 15. Slate

· Slates are metamorphic rocks.· Slates are composed of quartz, mica and clay minerals.· The structure is fine grained.· Slates split along the planes of original bedding easily.· The colour varies from dark gray, greenish gray, purple gray to black.· The specific gravity is 2.6 to 2.7. Compressive strength varies from 100 to 200 N/mm2.· They are used as roofing tiles, slabs, pavements etc.

3.3.5 Laterite

Figure 16. Laterite

· Laterite is a metamorphic rock.· Laterite has porous and sponges structure. It contains high percentage of iron oxide.· colour may be brownish, red, yellow, brown and grey.· specific gravity is 1.85 and compressive strength varies from 1.9 to 2.3 N/mm2.· It can be easily quarried in blocks. With seasoning it gains strength. When used as building

stone, its outer surface should be plastered.


3.3.6 Marble

Figure 17. Marble

· Marble is a metamorphic rock.· Marble can take good polish.· Marble is available in different pleasing colours like white and pink.· Specific gravity is 2.65 and compressive strength is 70–75 N/mm2.· Marble is used for facing and ornamental works. It is used for columns, flooring, steps etc.

3.3.7 Gneiss

Figure 18. Gneiss

· Gneiss is a metamorphic rock and having fine to coarse grains.· Alternative dark and white bands are common. Light grey, pink, purple, greenish gray and dark

grey coloured varieties are available.· Gneiss stones are not preferred because of deleterious constituents present in it.· Gneiss may be used in minor constructions. However hard varieties may be used for buildings.· The specific gravity varies from 2.5 to 3.0 and crushing strength varies from 50 to 200 N/mm2.


3.3.8 Quartzite

Figure 19. Quartzite

· Quartzites are metamorphic rocks.· The structure is fine to coarse grained and often granular and branded.· Quartzites are available in different colours like white, gray, yellowish.· Quartz is the chief constituent with feldspar and mica in small quantities.· The specific gravity varies from 2.55 to 2.65. Crushing strength varies from 50 to 300 N/mm2.· They are used as building blocks and slabs. They are also used as aggregates for concre

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