Engineering Geology Lecture 9

1. Chapter 9
Geological Construction Materials

2. Chapter 9
Geological Construction Materials
Introduction
Rocks as building materials
Soils and Rocks as construction material for roads,
dams..
Aggregate and Aggregate Test

3. Chapter 9
Geological Construction Materials
Outcome
Students will be able to understand geological
construction material
Students will be identify the suitable potential source
of geological construction material
Characterize the geological construction material for
different engineering structures

4. Introduction
Many civil & hydraulic structures require various
construction materials with good quality and quantity.
It is very important to study the nature, amount, quality
and economic significance of these geologic
construction materials.
This helps to address the demand of these industries to
their satisfaction.
4

5. Introduction Cont..
Significance of Geology in Civil works
Geology provides a systematic knowledge of construction
material:
its occurrence
composition
durability and other properties.
Examples of such construction materials are building stones
(granite), clays and sand.
Aggregates in earth dams, building, road

7. Introduction Cont..
Engineering geologist/ material engineer is assigned to study the
construction materials…
He/she can ask the following important questions
Is the material produced locally?
Is it cheap, abundantly available?
Is the material & construction climatically acceptable?
Can the material and technology be used and understood by
local workers, or special skills and experience required?
Does it require special machines, transportation?, etc.

8. Introduction Cont..
At present day the construction industry places a large
demand upon rock & soil products in the form of
Building stones in the form of masonry blocks.
Rubble-in the form of small irregular fragments.
Crushed stones-to make concrete
Limestone-to make lime and cement.
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9. Introduction Cont..
 The first consideration for construction material is Quality,
quantity and proximity.
a) Quality
Rock for dimension stone must be:
free of cracks
uniform texture
attractive color and
polish able.
Crushed stone and riprap must have:
satisfactory strength
soundness, and
low water absorption.
riprap should be roughly squared and reasonably flat faced.
Values of specific gravity of 2.6 and higher are preferred because
the rock has to be resistant for wave action etc.
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10. Introduction Cont..
b) Supply of the material (quantity)
The rock supply of a quarry generally is estimated in tones.
For dimension and crushed stone operations, the supply
should be sufficient for about 20 years if initial expense and
costs are to be justified.
For riprap quarries economically feasible operations
usually is possible even if the supply is only sufficient for
the immediate use on the structure
c) Proximity – the material should be available at/near to the
project site
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11. 11
Source of Constructional
material
(a) Naturally available
materials:
 Clay/Earth/Soil
 Wood/Timber
 Sand/Fine Aggregate
 Rock
(b) Artificial or Industrial
materials:
 Cement
 Bricks
 Steel
 Tiles
 Ceramic
 Paints and Varnishes
 Glass
 Plastic
 Stone
 Lime

12. Building Stones/Construction Material
Building materials (stones) are products of rocks that are used
in construction of buildings, dams, bridges etc.
 Factors determine whether a rock will be worked as a building
stone are:
volume of material that can be quarried
the ease with which it can be quarried
the wastage consequent upon quarrying; and
the cost of transportation
its appearance and physical properties.

13. Properties of Building Stones
 The properties that are commonly examined for rock materials, which
used for construction, are:
Mineral composition
Texture
Structure
Porosity
Permeability
Durability
Strength of rock
Resistance to fire
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Building Stones/Construction Material

14. Mineral composition
The rocks are aggregates of minerals.
If the constituent minerals of rock are:
Hard, Free from cleavage and resistant
to weathering.
The rock is likely to be strong and
durable.
The rocks, which are rich in weak
minerals such as mica, talc, calcite and
clay minerals, are not durable.
A uniform appearance is generally
desirable in building stone.
The appearance of a stone largely
depends on its color, which is determined
by its mineral composition. 14

15. Texture
 Fine-grained rocks are generally more dense and stronger than coarse-
grained rocks.
 Texture also affects the appearance of a stone, as does the way in which it
weathers.
For example, the weathering of some minerals, such as pyrite, may
produce ghastly stains.
 Generally speaking, rocks of light color are used as building stone.
 The texture and porosity of a rock affect:
 its ease of dressing, and
the amount of expansion, freezing and dissolution it may undergo.
 For example, fine-grained rocks are more easily dressed than coarse varieties.
 It is for this reason that Basalt and Dolerite are widely used as road metal.
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16. Structure /discontinuous
Many rocks contain structures like stratification,
lamination, flotation and cleavage.
Such rocks can withstand greater loads if their beds
are perpendicular to the line of action of load.
Ideally, rock for building stone should be:
Massive
Certainly it must be free from closely spaced joints
or other discontinuities
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17. Porosity
The porosity of a rock is the ratio of the volume
occupied by pores to the total volume of rock
sample. N = Vv/Vt
It is generally expressed as percentage.
A less porous rock is generally more durable and
stronger
Therefore it is preferred for construction work.
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18. Permeability
It is a capacity of a rock to transmit water.
The permeable rocks are considered harmful
because they cause seepage of water.
Permeable are not only result in loss of stored
water, but may also endanger the civil engineering
structures by developing pore water pressure.
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19. Durability
It is the capacity of stone to retain its original size, strength
and appearance for long time.
It depends on:
Chemical composition
Mineral constituents
Texture
Permeability and porosity
Structure
Climatic conditions
Assessment of the durability of building stone are acid immersion
test.
Sulfuric acid test…if they are resist this…
The crystallization test uses either magnesium or sodium
sulphate
Stones are being resistant/ weathering behavior to attack by
acidic rainwater.
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20. Strength of rock
it is one of important properties of building stone is strength and it is
measured in laboratory.
Crushing strength
It is the resistance offered by a stone to pressure or compressive
strength.
For usual building purposes, a compressive strength of 35 MPa is
satisfactory.
Shearing strength
It is the resistance offered by a stone against shear stresses that
tend to move one part of the specimen with respect to other.
Resistance to abrasion.
It is the resistance of stone against scratching or rubbing action.
The stone used for paving and flooring purposes must have high
resistance to abrasion.
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21. Resistance to fire
 The resistance of rock to fire will be more if it expands or contracts
uniformly throughout its body.
 This depends on the mineral composition and grain size.
Mono minerallic rocks quartzite, marbles, compact limestone and
dolomite possess greater fire resistance property because such rocks
have uniform expansion or contraction.
Grain size is also important in this context because, in Aphanitic rocks,
the minerals being very small in size, each grain will not exert any
significant volume change by itself and therefore the rock as a whole
undergoes expansion or contraction uniformly. 21

22. GRANITE
Figure: Granite slab
High crushing strength
Durability and weight.
Low porosity
Pleasing pink, and gray colors
Takes good polish
Massive masonry
architectural works,
Ornamental works and face
coverings
Constructions in the industrial
towns

23. Figure: Granite decorative building stone
Figure: Granite wall brick
Figure: Granite wall stone

24. Figure: Granite paving stone

25. Figure: Granite column building stone

26. Gneiss
 Gneiss is high-grade
metamorphosed rock.
 It has high crushing strength,
durability and weight.
 It is also used for the construction
of heavy engineering structures
like Dams, Bridges etc.

27. Continued…
Figure: polished Gneiss building stone

28. Continued…
Figure: Gneiss stone used as column of building

29. Continued…
Figure: Building built of gneiss stone

30. Sandstone
Well-cemented sandstones are good building stones.
They are used both in building masonry and as facing
stones) used for ornamental works
Figure: Red sandstone block

31. Continued…
Figure: sandstone as wall stone in building

32. Continued…
Figure: Sandstone cobble

33. Continued…
Figure: Sandstone brick

34. Marble and Limestone
Due to:
 Homogenous texture
 easy workability and pleasing
colors,
 Limestone and marble are used
for building and ornamental works.
Compact limestone is also used for
ballast along railway track.
Limestone is also used in the
cement making industry

35. Continued…
Figure: Marble rock

36. Continued…
Figure: white grey marble tiles

37. Continued…
Figure: Marble wall stone

38. Continued…
Figure: Marble Sculptures

39. Basalts and Dolerites
They make excellent road metal and aggregate for
concrete because of their high crushing strength.
They are not commonly used as building stone
because of their dull and unpleasant color, even
though they have easy workability and durability.

40. Slates
Slates are metamorphosed
form of shale.
Slates can be split easily
into thin and smooth
slabs.
Hence they are chiefly
used for roofing, flooring
(or paving) in buildings.

41. Quartzite
Quartzite is metamorphosed sandstone.
Quartzite is not used as building stones since its
workability is difficult due to its extreme hardness.
 However quartzite broken stone is used as road metal.
It can be used as aggregate as ballast for railway
track.
Pure and white quartzite is used in glass making
industry.

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 Materials used for roads:
 Gravel, crushed rock aggregates for the top layers.
 Sand and clay may be used for embankment.
 Materials used for airfields:
 Landing and takeoff strips have the same requirements as
roads, although the specifications are more stringent due to
higher loads.

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Railways
 The ballast bed generally consists of
coarse aggregate in which the shapes
are embedded.
 The ballast bed is placed either directly
on the sub-grade or on a layer of
blanketing sand.
 The function of the blanketing sand
is primarily to provide a filter to
prevent contamination of the ballast
by fine particles derived from
ascending water (from sub-grade to
ballast bed).
 As the higher loads are passed on to the
ballast bed by relatively small sleepers,
abrasion and fracturing may occur.
 The material should, therefore, be
stronger than in the case of road sub-
base materials.

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Construction materials for
railways:
Railway ballast material should
be:
 Clean.
 Strong.
 Angular.
 Durable.
 Closely graded.
 Free draining aggregate.

45. 45
Fine material is not
wanted in railway ballast
as it influences:
 Stability.
 Creep resistance of the
ballast bed.
 Drainage is hindered.

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Dams and Coastal Protection
 For dams, more than for any other construction, the construction
material should be obtained locally because of large quantities
needed.
 Dams are designed to fit the available materials.

47. 47
Materials for Core fill
Materials for impermeable core are specified in terms of grading,
plasticity, moisture content and compaction standard.
Required criteria include:
 Low permeability,
 Intermediate to high plasticity,
 High shear strength
 Clay content 25-30% suitable for core.
Other desired properties of core fill are:
 Homogenous,
 Less compressible,
 High compacted density,
 Low pore pressure,
 High shear strength,
 Moderate plasticity,
 Good grading.

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Materials for Shoulder fill
 High shear strength,
 High permeability to assist at dissipating pore water pressure,
 Wide range of material could be used; not only single material.
Materials for Drain/ Filter materials
 Filter materials selection should be based on the design criteria
(piping and permeability criteria) and no clogging is required.
 Priority need to be given to naturally available filter materials;
processed materials can also satisfy the same purpose, despite its
cost.
 Must be permeable, clean and free of sediments in cases of
naturally collected sand, and no clogging or piping is required.
 The filters are covered with rockfill.

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Requirements of filters:
 Structural stability (especially in unconfined
condition).
 Durability.
 High permeability coupled to resistance to internal
erosion of fine particles.
 Low frost susceptibility.
 Low susceptibility to salt aggression, chemical
attack, and solution loss.
 The strength, shape, texture, and composition of the
particles will have an important impact on the above
properties.

50. Riprap
Riprap is preferably a relatively thin layer of:
– Large, approximately equidimensional,
– Durable rock fragments or blocks placed on bedding
– To dissipate water energy and protect a slope, channel bank or
shore from erosion caused by the action of runoff, currents,
waves or ice
50

51. • Riprap surfaces on earth dams must:
– withstand severe ice and wave action
– withstand heavy rainfall, turbulent flow
– as well as destructive forces associated with
temperature changes, which includes freezing and
thawing, heating and cooling, and wetting and drying.
• Riprap either: dry-dumped or hand-placed, concrete
pavement, steel facing, bituminous pavement, precast
concrete blocks, soil-cement pavement, wood & sacked
concrete.
• Riprap should be “hand” placed to reduce the void space
and maximize the interlocking arrangement
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52. • Most riprap is dumped and falls into place by gravity with little
or no additional adjustment.
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53. Riprap Quality
 Rock quality is determined by laboratory & field testing.
 There are numerous quarries and pits capable of producing aggregate,
but not all sources are suitable for the production of riprap.
 Riprap sources must produce:
 the necessary weight & size,
 shape,
 gradation, &
 durability to be processed and placed and then remain “nested” for the
life of the project.
• Performance on existing structures is a valuable method of assessing
riprap quality from a particular source.
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54. Shape of riprap
 The shape of individual rock fragments affects the workability and
nesting of the rock assemblage.
 Natural “stones” from alluvial and glacial deposits are usually rounded to
sub-rounded and are easier to obtain, handle, and place and, therefore, are
more workable.
 Rounded stones are less resistant to movement.
B/c the stones interlock more poorly than angular rock fragments, easily
eroded by water action.
 Angular-shaped rocks nested together resist movement by water and
make the best riprap.
 The rock fragments should have sharp, angular, clean edges at the
intersections of relatively flat faces.
 Alluvial deposits are used as riprap sources only if rock quarries are
unavailable, too distant, or incapable of producing the appropriate sizes.
 Rounded to sub-rounded stones are typically used only on the
downstream face of embankments, in underlying filters, or as the
packing material in gabions.
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55.  Not more than 30% of the riprap fragments should have a 2.5 ratio of
longest to shortest axis of the rock.
 Stones having a ratio greater than 2.5 are either tabular or elongated.
tend to bridge across the more blocky pieces or protrude out of the
assemblage of rocks.
 During handling, transporting, and placement, these elongated or
tabular rock fragments tend to break into smaller fragments
55
Tabular rock fragments

56. • Most igneous and some sedimentary rocks are capable of
making suitabl shaped fragments. However, secondary
fracturing or shearing will affect the shape.
• Rocks having closely spaced discontinuities tend to
produce fragments that are too small.
• Sedimentary rocks that have bedding plane partings tend
to produce flat shapes.
• Metamorphic rocks tend to break along jointing, rock
cleavage, or mineral banding and often produce elongated
shapes.
56

57. Weight and Size
• The unit weight of riprap generally varies from (2.4 to 2.8 g/cm3)
• Rock having unit weight above 2.6 g/cm3 is typically suitable for
riprap.
• Most rock sources are capable of producing suitable weights and sizes.
• The size rarely impacts use as a riprap source unless more than 30% of
the rocks are elongated or flat.
• Size range is controlled by discontinuities in the rock.
• Columnar basalt, some fine-grained sedimentary rock, and
metamorphic rock commonly have inherent planes of weakness that
limit larger riprap sizes.
• the rock mineralogy and porosity also controls the weight of riprap.
• Generally, rock having a low unit weight is weak and tends to break.
57

58. Gradation
 The desired size fractions of the individual particles that will nest
together and withstand environmental conditions.
 The gradation design is based on the ability of the source(s) to produce
appropriate sizes.
 Most coarse-grained sedimentary and igneous rock quarries are
capable of producing suitable riprap gradations.
 Intensely to moderately fractured rock rarely produces suitable riprap
gradations.
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59. Durability
• Riprap durability affects the ability of a source to provide a consistent
shape, size, and gradation and the ability to resist weathering and
other environmental influences.
• Durability is a function of the rock’s mineralogy, porosity,
weathering, discontinuities, and site conditions. In rare instances,
environmental considerations such as Abnormal pH of the water may
be a controlling factor in selecting an appropriate riprap source.
59

60. 60
Quantity
 Every riprap source must provide the estimated quantity
required.
 Estimating realistic quantities depends on: understanding
of subsurface geologic conditions, uniformity of rock and
discontinuities within a source area.
 This estimate (often referred to as the reserve) provides
not only the amount of riprap available but also provides an
understanding of wastage resulting from blasting, handling,
processing, haulage, and placement..

61. 61
what are aggregates?
 Aggregate: the inert filler materials, such as
sand or stone, used in making concrete.
 Aggregates for concrete are divided into two:
 Fine aggregates
 Coarse aggregates
(a) Fine aggregates:
 Sand and/or crushed stone
 < 5 mm (0.2 in.)
Fine aggregate content usually ranges from 35%
to 45% by mass or volume of total aggregate.
(b) Coarse aggregates:
 Gravel and crushed stone
  5 mm (0.2 in.)
 Typically between 9.5 and 37.5 mm (3/8
and 1½ in.)

62. Aggregate
Aggregates can be
classified as natural or
artificial depending on
their sources.
Natural aggregates are
obtained from quarries by
processing crushed rocks
or from riverbeds
Artificial aggregates are
obtained from industrial
by products such as blast
furnace.

66. 66
Factors affecting aggregate quality for concrete
(a) Size and grading:
Aggregate grading affects:
 Void-filling characteristics,
 Permeability,
 Strength of concrete,
 Strength of road base aggregates,
 Filter design materials.
Requirements:
 Maximum size up to 40mm in diameter.
 Minimum size: 5mm.
 Commonly preferred size is about 20mm
(maximum).
 Size limits: 20-5mm graded aggregates are
commonly used.

67. 67
Dense-graded mixes:
 well graded, continuous graded, straight line
graded.
 Characterized by an even blend of size fractions
from coarse gravel to silt, such that the finer
grains can - with the help of vibration, watering
and compaction - fit between the coarser ones.
Open-graded aggregate blends:
 Termed no fines, harshly graded.
 Contain an even mixture of coarse particle sizes,
but little or no void filling fines.
Gap-graded mixtures:
 Also termed skip graded or ‘armchair’ graded).
 Have an intermediate size fraction missing,
generally coarse sand or fine gravel (say, 1–5
mm).

68. 68
Particle size distribution curves for different aggregate mixtures used
for concrete, unbound roadbase and asphalt.

69. 69
(b) Particle shape:
 could be rounded, angular, flaky, elongated, etc.
 Ideal aggregate mixture: all particles should be equidimensional
and angular, but not spherical.
 Flakiness of an aggregate have an effect on:
 Quality: some flaky particles are more easily stripped from
bitumen seals.
 Workability of concrete (compacting behavior): concrete
mixes rich in misshapen fragments are difficult to pump and
to compact.
 Strength of concrete: with more flakiness flexural strength
is affected.
 Water demand of concrete: with increase in flakiness water
demand of the concrete mix increases.
 These flakes may bridge across open voids in the mix,
weakening it, or, if filled, will increase the cement demand.

70. 70
Consequences of flaky and
elongate particles on
aggregate behavior in chip
seals, concrete and
asphalt.

71. 71
(c) Particle surface texture:
 This include all those factors influencing the bond
between chips and bituminous binder in asphalt, and that
between cement paste and aggregate in concrete.
 The relevant aggregate properties comprise particle
roughness, dustiness, moisture content and surface
chemistry.
 Is a function of mineral grain size and rock fabric.
 Fine-grained igneous rocks tend to have smooth or
glassy fracture surfaces, medium- and coarse-
grained ones are rougher textured, while some are
visibly porous or even vesicular.
 The rougher the texture, the better the bond
strength.
 It is often related to concrete flexural strength which are
frequently found to reduce with increasing particle
smoothness.

72. 72
(d) Bulk density (or its unit weight):
 It reflects in part to its void content at a given
degree of compaction and is therefore an indirect
measure of the grading and shape characteristics.
 It ranges: 1200-1800Kg/m3 for normal
aggregates; 500-1000Kg/m3 for lightweight
aggregates.
(e) Particle density (relative density):
 It is a property of particular value in concrete mix
design, concrete yield checks, and in the
assessment of compaction and void content of
hardened concrete.

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(f) Water absorption:
 Is an indirect measure of the porosity/permeability of an aggregate
which in turn can relate to other physical characteristics such as
mechanical strength, shrinkage, soundness and to its general
durability.
 In general less absorptive aggregates often tend to be more
resistant to mechanical forces and wetting.
 Acceptable limit: 1-5% (generally).
 Lightweight aggregates generally have higher water absorption
values: 5-20%.
(g) Aggregate durability:
 Several tests are carried out which include soundness test, and
alkali-reactivity.
 Soundness test: measures the resistance of aggregates to
degradation or disintegration resulting from crystallization of salts
within the pores and interstitial structures of the aggregate
particles, also to wetting-drying, heating-cooling cycles.

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h) Alkali-Aggregate Reactivity (AAR)
AAR is a reaction between the
active mineral constituents of
some aggregates and the sodium
and potassium alkali hydroxides
and calcium hydroxide in the
concrete.
It includes:
 Alkali-Silica Reaction
(ASR).
 Alkali-Carbonate
Reaction (ACR).
Visual Symptoms:
 Network of cracks.
 Closed or spalled joints.
 Relative displacements.
 Fragments breaking out of the
surface (popouts).

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Mechanism for ASR:
1. Alkali hydroxide + reactive silica gel  reaction
product (alkali-silica gel).
2. Gel reaction product + moisture  expansion.
Influencing Factors for ASR:
 Reactive forms of silica in the aggregate,
 High-alkali (pH) pore solution
 Sufficient moisture
If one of these conditions is absent - ASR cannot
occur.

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Alkali-Silica Reaction (ASR)
Test Methods:
Mortar-Bar Method (ASTM 227)
Chemical Method (ASTM C 289)
Petrographic Examination (ASTM C 295)
Rapid Mortar-Bar Test (ASTM C 1260 or
AASHTO T 303)
Concrete Prism Test (ASTM C 1293 )

77. 77
Controlling ASR:
 Non-reactive aggregates
 Supplementary cementing materials or blended
cements
 Limit alkali loading
 Lithium-based admixtures
 Limestone sweetening (~30% replacement of
reactive aggregate with crushed limestone)

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Alkali-Carbonate Reaction (ACR)
Influencing factors:
 Clay content, or insoluble residue content, in the range
of 5% to 25%.
 Calcite-to-dolomite ratio of approximately 1:1
 Increase in the dolomite volume
 Small size of the discrete dolomite crystals (rhombs)
suspended in a clay matrix
Test methods:
 Petrographic examination (ASTM C 295)
 Rock cylinder method (ASTM C 586)
 Concrete prism test (ASTM C 1105)

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Controlling ACR:
 Selective quarrying to avoid reactive
aggregate
 Blend aggregate according ASTM C
1105
 Limit aggregate size to smallest
practical

80. 80
(i) Frost susceptibility:
 Some aggregates may contain fragments of friable
sandstone, porous limestone, chalk or white flint cortex
particles.
 These materials are micro-porous and hence potentially
frost susceptible.
(j) Impurities:
 Effects of fines on concrete include: increase in water
demand, coatings impair mixing of aggregates, and reduce
aggregate-matrix bond.
(k) Other properties
 Aggregate drying shrinkage.
 Thermal movement.
 Fire resistance.

81. The principal tests For Aggregates
Particle size
Aggregate crushing test
Aggregate impact test,
Aggregate abrasion test
Water absorption
Specific gravity
Density
Aggregate shape tests.

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Mechanical Test for Aggregates
Aggregate Crushing
Value (ACV)
 About 2Kg of sample is
taken.
 Apply continuous load
transmitted through a
prism, in compression.
 Total load: 400KN is
achieved in 10 minutes.
 Fines passing sieve BS
2.36 mm is calculated as
the percentage of initial/
original weight.
 A high value indicates a
weak, potentially non-
durable material.

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Aggregate Impact Value
(AIV)
 A sample of 14mm to 10mm in
size is subjected to discontinuous
loading of 15 blows from a
hammer or piston (13.5-14.1Kg);
height 380mm+6.5mm.
 The sample suffers degradation to
a graded assemblage of fines.
 Sieve size: 2.36mm is chosen and
% of material passing relative to
the initial weight gives the
aggregate impact value.
 AIV is used as a measure of
resistance to granulation.
 Low numerical value means a
resistant rock.

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Variation in ACV and AIV may be due to:
 Influence of particle shape.
 Geological features e.g. bulk
composition.
 Grain-size.
 Texture. E.g. Smooth, rough.
 Structure e.g. micro-structures.
 Alteration.
 Methodological factors e.g. apparatus
rigidity, etc.

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Ten Percent fines value
 This presents the load required to
produce 10% fines rather than the
amount of crush for a specific load.
 A uniform loading rate is applied to
cause a total penetration of the
plunger of approximately 15mm
(gravel), 20mm (normal crushed
rock), or 24mm honey combed
aggregate in 10 minutes.
 The fines less than 2.35mm should
fall within 7.5% to 12.5% of the
initial weight.
 The force required to produce 10%
fines is calculated by:
X= Maximum force (KN).
Y= Mean percentage of fines from two tests at X KN.
 Some judgment is required to
generate exactly 10% fines.
 In practice, two tests are performed,
with the aim of liberating about 7%
and 13% fines.
 The ram load required for 10% fines
is then estimated by proportioning
between these values.

86. 86
Aggregate Petrography Test
Durability: Predicting the durability of aggregates, expected to be
susceptible to weathering or alteration.
Reactivity: Predicting potential reactivity between free alkalis in
the cement paste and certain siliceous and dolomitic aggregates.
Deleterious minerals: Detecting other deleterious minerals such
as gypsum (a source of sulphate attack in concrete), sulphides
(which oxidize, generate acid and stain finished concrete), fine
micas (in sand) and clays (swelling and otherwise).
Abrasive wear: Estimating the abrasive wear potential of
siliceous rocks on crusher plates and screens, in terms of their
granular quartz (‘free silica’) content.

87. 87
Bond strength: Investigating the aggregate-paste bond
strength in concrete, particularly where reaction rims
form due to pozzolanic action.
Surface micro-texture: Investigating the surface micro-
texture of aggregate chips, mainly with regard to their
skid resistance.
Flakiness: Investigating the lithological, as distinct from
the crushing induced, causes of flakiness.
These include metamorphic foliation and flow banding in
acid lavas.

88. Further Reading on
• Bricks
• Timber
• Cement
• Lime
• Metal
• Ceramics
• Concrete
• Paints
• Glass
• Plastics
• Mortar