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Aggregates

Introduction to• Different types of aggregates• Relevance to sustainable aggregates supply• Different uses of aggregates• Requirements for different aggregates (why rather that what)• Different sources of aggregates

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Naturalaggregates(Crushed) RockaggregatesArtificialaggregatesRecycledaggregates

Warning

Some potential sources ofmisunderstanding concerningsoil and aggregates

Credits for the pictures: Blogs.egu.eu, www.soilsandhealth.orgwww.webpages.uidaho.edu

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Aggregates

Soil (sand or gravel) or crushed rock• Excavated as it is or processed• Selected and finished to specific sizes or shapes• Selected, sieved (dry or wet), crushed

- Endurance and capability to maintain its essential and distinctive characteristics of strength, resistanceto decay, and appearance

- Within EU: CE-marking• CE-marked aggregates are produced in standardized, harmonized manner• Declaration of Performance• Only qualified producers can give CE-marking

Aggregate production

Globally largest sector ofextractive industries”Through 2017, worldwide sales ofconstruction aggregates are forecast toexpand 5.8 percent per year to 53.2 billionmetric tons (Gt).The market is predicted to expand further to66.2 Gt by 2022.””Globally, crushed stone production ispredicted to grow by an average of 7.7 percentannually”

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Aggregate use in infrastructuresno aggregates-no construction

20 m3/capita, 100x106 ton/a, over 300 aggregateproduction sites

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Sustainability issuesProblems:• Commonly regionally limited

sources of high qualityaggregates, particularly

• Aggregates are non-renewable- sand and gravel deposits- important aquifers- fluvial deposits- shoreline deposits

• Conflicts with groundwater andsurface water use, coastalmanagement, fishery, birdlifeetc.

Solutions• Utilization of rock aggregates

increases• Recycling of aggregate based

materials• Challenges:

- new techniques for concreteproduction needed

- Aggregate material research and newtechniques

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Main use of construction aggregate• Cementitious materials

- concrete- mortar etc.

• Road construction- asphalt pavements- baselayers (bituminous or

hydraulically bound)- unbound base course- unbound road aggregates

• over 75 %

• Railroad construction• Foundations and other civil

engineering structures

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Concrete aggregates- All-in aggregate mixture ( fine and coarse

materials)- Filler aggregates (<0,063); fine aggregates (<4

mm); coarse aggregates (max size >4mm,minimum>2mm based on sieving)

• Specific characteristics include- shape and grading requirements- contents of fines and coarse- shell content- chemical resistance- reactivity of materials- Radioactivity of materials- Density (depending on the type of concrete)

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Shape ratio of mass percentage ofparticles with length/thickness >3

grain sizes over 4-64 mm

Examples of geometrical tests

• Flakiness: by test sieves, with squareapertures+ corresponding bar sieves,comprising parallel cylindrical barsconforming

• Sieve test (standards for sampling,sample treatement, sieving procedureand applied sieve size-and shapes)

• Standards for measuring the proportionof crushed and broken surfaces

• Shape index fro coarse material

Shape index- Shape ratio of mass percentage of particles with

length/thickness >3- grain sizes between 4-63 mm

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Practical requirementsConcrete aggregates should• Represent homogeneous or uniform

material• Low radioactivity• No alkali-silica reactions• Low mica content (<7 %), sulfides (< 1-

2 %)• Less angular grain shapes

- Minimum cement consumption

• Low amount of fines• No clogging during pumping

- Flat, elongate grains rapidly deteriorate toworkability of pumping of concrete

Sand and gravel aggregates favoredthis farShortage of these resources has alreadylead e.g. in Sweden and Norwaydevelopment of technology that canutilize rock aggregates

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For instance, flaky and elongatedparticles tend to lower theworkability of concrete mix whichmay impair the long-term durability.

Road construction aggregates

Manufactured or recycledaggregates

- Hydraulically bound and unboundmaterials for civil engineering workand road construction.

• EN 13242 + A1

- Bituminous mixtures and surfacetreatments for roads, airfields andother trafficked areas

• EN 13043 + AC

- (Armourstones• EN 13383-1 + AC)

Requirements deal with- Geometrical requirements

• Sizes and grading of aggregateso (grain-size distributions and ranges on sieve test)

• Flakiness (in. Finland max values forflakiness index defined for differentclasses)o For bituminous mix, flaky particles are liable to break up

and disintegrate during the pavement rolling process.• Proportion of grains with a crushed and

broken surfaces defined

- Particle density- Mechanical and physical properties- Resitance to wear, fragmentation and

impact, freezing and thawing- Water absorption- Thermal and weathering properties- Chemical properties 15.10.2016

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Aggregates for other civil engineeringworkManufactured or recycledaggregates

- Hydraulically bound and unboundmaterials for civil engineering workand road construction.

• EN 13242 + A1

- Armourstones• EN 13383-1 + AC

+ standards referenced inthese documents

Requirements deal with- Geometrical requirements

• Sizes and grading of aggregates• (grain-size distributions and ranges on

sieve test)• Rounding (proportions of rounded

clasts)

- Particle density- Mechanical and physical properties- Resistance to wear, fragmentation

and impact, freezing and thawing- Water absorption- Thermal and weathering properties- Chemical properties

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Tests for mechanical and physicalproperties (European standards)

- Determination of the resistance to wear (micro-Deval)- Methods for the determination of resistance to fragmentation (LA-test)- Determination of loose bulk density and voids- Determination of the voids of dry compacted filler (Ridgen device)- Determination of the water content by drying in a ventilated oven- Determination of particle density and water absorption- Determination of the particle density of filler. Pyknometer method- Determination of the polished stone value (coarse aggregates for road surfacing)

• Accelerated polishing machine• Alternative method: aggregate abrasion value

- Determination of the resistance to wear by abrasion from studded tyres. Nordic test- Determination of water suction height (of an reference aggregate layer in direct contact with

water)- Determination of compressibility and confined compressive strength of lightweight aggregates

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Sufficient aggregate resources cannot be taken for granted!• E.g. In Nordic countries (hardrock areas) only few percent of outcrops

(thousands) studied by GTK and SGU fulfill the requirements set toasphalt and railroad aggregates

• Areal distribution uneven!

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In Finland 3 categories forrailroad ballast:

• LARB 12• LARB 16• LARB 20

• In Finland 4 categories for asphaltpavement aggregates (Nordic ballmilltest)

• I <=AN 7• II <=10• III<=14• IV<=19

Rock-types and aggregate quality

Certain rocks make systematically better/poorer aggregates- High abrasion resistance (low AN or MDE)

• Quartzite, porfyritic volcanic, metavolcanic rocks, diabases , fine grained granites

- Low abrasion resistance (high AN)• Schists, carbonate rocks and lime stones, any mica rich rock

- High impact resistance (LA low)• Mafic rock types (Fe-Mg-silicate rick rocks) (diabase, diorite, gabro and their metamorphosed,

mica poor counterparts)• Many volcanic rocks (and metavolcanic (mica poor) rocks)• Tectonically recrystallized (dynamic recrystallized) rocks

- Low impact resistance (LA high)

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In Finland only about3 % of studiedoutcrops suitable torailroad ballast or forasphalt in highlytrafficked roads

Nordic ballmill test (abrasion susceptibility)

Rock mineralogy and aggregate qualityMineralogy (minerals and their contents) are some main factorsaffecting the quality based on LA, AN• Presence of any sulfide minerals• Presence of soft minerals, particularly mica

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Mica content

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AN<=10 AN<=15 AN<=20

Grain size and aggregate quality

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Mineral contacts

More complex the better

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Deformation

Dynamic metamorphosis (induced by shearing)

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Metamorphosis

Low metamorphic grade (low pressure and temperature)produces mica (chlorite, biotite, muscovite).High metamorphic grade favors recrystallization in stableconditions that leads to straight crystal contacts• medium grade, amphibolite facies probably best compromise?Hydrothermal alteration e.g. along faults can cause alteration offeldspars to fine mica (sericite, saussurite)

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Geological trends

Complexity of grainboundariesGrain-sizeMica contentDensity (function of Fe-Mg-silicate content)

- Note also Fe-Mg-silicates bind moreefficiently to bitumen, which effectsthe performance of mafic rocks asasphalt pavement

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Nordic ball mill test

LA

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Weight of aggregate material• Utilization of aggregates involves conversion of volumes to tons as a

part of mass balance calculations• Excavated rocks and soils, transported loose loads of aggregates• Density of most common minerals (and granitic rocks) 2.5-2.8

ton/m3

• Density of solid materials in sand and gravel also fit to this category and quite commonlysame conversion factors will be used for soil and rock aggregates (assumed to be granitic)

• Density of many rock types comprising high quality aggregates canbe substantially higher (up to 3.1-3.3 ton/m3). Conversion shouldtake this into account!

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Harmful components ( for concrete)

• Materials in proportions that• adversely affect surface quality

or durability.• Constituents affecting the setting

and hardening of concreteThese may be a greater problemin recycled and artificial (= poorlytested?) aggregates

- In aggregates (or water!)• Organic contaminants• Iron sulfide (e.g. pyrite)• Humus and sugar-type/ liginite (soil

aggregates)• Some clay minerals

- Sulfates in aggregates can give rise toexpansive disruption of the concrete.

- (gypsum plaster in recycledaggregates)

- Weathering of sulfides- Chlorides (mostly environmental

pollution)

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Alkali-silica reactions (ASR) in concrete

Reactions of minerals withalkaline solutions and alkalinehydroxides present in concreteAlkali-silica reactions• Different forms of silica• Certain clays and• Alkali-carbonate reactions

Solutions• limit the total alkali content of

the concrete mix;• use a cement with a low

effective alkali content;• use a non-reactive aggregate

combination;• limit the degree of saturation

of the concrete with water.

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Tectonic processes and ASR

Left is a geologic map ofGothemburg-area in SwedenNote the increase ASR-riskalong large tectonic faults• deformation

- locked tectonic stress- unstable quartz?

• hydrothermal alteration?- silica (unstable, amorphic form of

silica)

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Concrete aggregate tests

•ASTM C227: “Test Method for Potential Alkali Reactivity ofCement-Aggregate Combinations (Mortar-Bar Method)”•ASTM C289: "Standard Test Method for Potential Alkali-SilicaReactivity of Aggregates (Chemical Method)"•ASTM C295: “Guide for Petrographic Examination ofAggregate for Concrete”•ASTM C1260: “Test Method for Potential Reactivity ofAggregates (Mortar-Bar-Test)”•ASTM C1293: “Test Method for Concrete Aggregates byDetermination of Length Change of Concrete Due to Alkali-Silica Reaction”•ASTM C1567: "Standard Test Method for Determining thePotential Alkali-Silica Reactivity of Combinations ofCementitious Materials and Aggregate (Accelerated Mortar-BarMethod)"

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https://en.wikipedia.org/wiki/Alkali%E2%80%93silica_reaction

Main sources ofaggregates

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Igneous rocksMain source or rock aggregates• Crushed plutonic rocks commonly

have physical properties that aresufficient for most (but not all)civil engineering purposes

• Geometrical properties ofaggregates can be controlledduring crushing to some extent toprovide needed grain-size andgeometrical properties

• By products of building stoneexcavation, construction

Page 31Kuva: GTK/Paavo Härmä

Mafic igneous rocks as aggregates- Can provide high-strength, wear-resistant and

density required in certain importantapplications

• Rail road ballast• Asphalt pavement• Dense materials for e.g. bridge engineering

• Result from partial melting of the uppermantle of the Earths crust

• Include Fe_Mg-rich silicates- Mechanical stiffness- Moderately high hardness- Dense- Bound chemically to bitumen

Page 32Kuva: GTK/Paavo Härmä

Bowen’s reaction series

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Intrusive rocks

GraniteGranodioriteQuartzdioriteDioriteGabro (+ subclasses)Peridotite (+ subclasses

Gran

Grdr

Qzdr

Dior

GabroPeridotite

Felsic

intermediate

Mafic

Acidrocks

Ultramafic Basicrocks

Volcanic rocks• Basic (low-silica) magmas commonly erupt

on the surface as lava flows or small andless violent pyroclastic eruptions buildingcinder cones.- due to their lower viscosity and low content of

water (volatile components)

• Form basalts (or andesites) which areeruptive counterparts of gabbro and diorite

• Lavaflows can be large, good or excellentaggregates known as trap rock

• Cinder cones can comprise loose material- Ready to be excavated, comprise in geologically

young areas valuable sources of aggregates

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Dykes- Represent intrusion channels for magma- Cooled faster than intrusive rock but slower than volcanic rocks- In sedimentary rock areas, swarns of diabases particularly, can comprise regionally

important sources of aggregates

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Sedimentary rocksSedimentary rocks cover a majority of earths continental crust• Limestones and sandstones are therefore used extensively in

construction. Commonly because no better material is available- Bitumen containing sandstones may comprise good aggregate materials for road

construction.

The quality sedimentary rocks as crushed rock variessubstantially (some good materials can be found)• needs to be investigated carefully• design of mixes essentialExamples of unusual materials in USGS

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Example: Approach to sustainable aggregateresource management USGSThe use of (SARM) can help ensure an economically viablesupply of aggregate. SARM techniques that have successfullybeen used include

- protecting potential resources from encroachment;- using marginal-quality local aggregate for applications that do not demand a high-

quality resource;- using substitute materials such as clinker, scoria, and recycled asphalt and concrete;

And using rail and water to transport aggregates from remotesources.

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Artificial and recycled aggregates• So called light aggregates

- made by heating and melting suitable soil materials• Fat clays (Leca-gravel)• Perlite (volcanic tuffs with a perlitic texture)

• Crushed concrete- Binds CO2, readily available but in limited amounts- Will not be able to solve all sustainability issues

• Different types of slag materials (metallurgical waste)- E.g. Oktomurske eng. OKTO-aggregate

• Slag material of ferro-chorimium production

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Sand and gravel aggregates

FluvialGlacio-fluvialEolian

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Braided drainage pattern

Forms in arid areas during flash flooding or from the meltwaterof a glacierThe stream “attempts” to carry more material than it is capableof handling.Much of the gravels and sands are deposited as bars andislands in the stream bed

Maturity of the flow systemYouthful stream valleys•located in highland areas,•steep gradients, high water velocities with•rapids and waterfalls,•downcutting in stream bottoms results to the V-shaped valleys, andthe filling of the entire valley floor by the stream•strong erosion, little deposition

A mature system•a developed floodplain•the stream no longer fills the entire valley floor but meanders to bothedges of the valley.•The stream gradient is medium to low,•Net deposition of materials, and widening the valley compared withthe youthful stream) less downcutting and more lateral erosion

An old-age system,Gradient is very gentle, and the water velocity is low.Little downcutting, meandering has lead to an extensivefloodplain.Low water velocity, a great amount of deposition.The river only occupies a small portion of the floodplain

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Variation of flow velocity in a channel leads to variation indeposition/erosion

Point bar deposits

Point bar is a low crescent-shaped mound of sand located at inner bend of a river or streamChannel bar a streamline mound continuing developed typically in braided stream buy may alsooccur in meandering rivers down stream of point-bar and continuing on opposite site.

Channel bar

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In meandering rivers, levees may allow higher stage of river(about 0.5-1.5 m)

Distribution of Glacial landforms

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Glacial deposits

Stratified deposits are actually deposited by glacial streams(glaciofluvial) and not by the moving ice itself!• Outwash plains.• Eskers.• Kames.• Kame terraces.• Glacial lake deposits.They represent material in the glacier has been carried and deposited by meltwater from the glacier. The flow hassorted the material and removed fines so that end result is essentially deposits of sands and gravels.

Glacial outwash

Outwash plains result when great volumes of melt water flowthrough the end-moraine as a number of streamsEach stream forms an alluvial fan that merge to comprise arelatively flat sheet of glacial out wash depositsOutwash plain exist particularly in areas where the ice sheet hasflown above a sedimentary rock or where the depth ofsedimentary cover has been thick (up to hundreds of meters)

glacial accumulation areas

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Eskers

Eskers are winding ridges of irregularly stratified sands and gravelsthat are found within the area of the ground moraine (till).“The ridges are usually several km long but are rarely more than 15 to20 m wide or more than 50 m high. “Yes, IN AREAS with thick sedimentary coverage/sedimentary rockareas!Formed by water that flowed in tunnels or ice-walled gorges in orbeneath the ice. They branch and wind like stream valleys but are notlike ordinary valleys in that they may cross normal drainage patterns atan angle, and they may also pass over hillsIn hard rock areas, however eskers are commonly substantially largerland forms

Buried valleys

In sedimentary area, melt waters have been able to erodechannels into the sediments and sedimentary rocks under theglaciers.These have been subsequently buried by sediments either fromthe same glaciation or subsequent glaciations.Buried valleys comprise increasingly important aquifers inGermany, Poland, Denmark that is at marginal, sedimentary rockareas of the Fennoscandian ice sheet and similar areas in N-America

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Glacial landforms (continental icesheet)

Glacial land forms: Alpine glaciers

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Valley deposits

Unstratified glacial deposits

Sediments deposited by the ice itself comprise aerially andvolumetrically most common glacial deposits.They comprise the following surficial features:Ground moraines.End moraines.Recessional moraines.Drumlins.The poorly sorted glaciogenic sediments are actually called tills

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Drumlins

Kuva Harri Kutvonen,GTK

Proximal part

Distal partDirection of icemovement

Eolian deposits

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Eolian erosion

DeflationAbrasion

A ventifact, Photo byGTK

Eolian deposits

Lag deposits or desert pavement.Sand dunes.Loess deposits.

2km

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Transverse dunes occur in desert locations where agreat supply of sand is present over the entiresurface.Longitudinal dunes occur where strong winds blowacross areas of meager amounts of sand or wherethe winds compete with the stabilizing effect of grassor small shrubsBarchan dunes form in open areas where thedirection of the wind is fairly constant and theground is flat and unrestricted by vegetation andtopographyParabolic, or U-shaped, dunes typically form alongcoastlines where the vegetation partially covers thesand or behind a gap in an obstructing ridge. Later, aparabolic dune may detach itself from the site offormation and migrate independently