Construction

Aggregates

1. Uses & Economics in UK

2. Types & Sources

3. Processing & Testing

4. Environmental Impact

1. What are aggregates?

‘granular material used in construction and

may be natural, manufactured or recycled’

• Aggregates are a low cost product used in

very large quantities

1. Primary are extracted from mineral

deposit and are used for first time

2. Secondary & recycled had a previous use

• Demand for aggregates from construction

industry:

• Maintenance of transport infrastructure

• Construction of Affordable housing

• Rail system growth (HS2 & Crossrail

projects)

• Flood & coastal defences

Uses of Aggregates

add additional strength and bulk to composite material, e.g. concrete

as a drainage & filter material as possess high hydraulic conductivities, e.g. coarse gravels in french drains & landfill sites

base material under foundations, roads & railways (madeground)

to make a surface suitable for task, e.g. road stone in asphalt on roads

for building materials and finishing products, e.g. bricks, masonry, plaster

1.

UK Aggregates UK demand for stone is about 200 million

tonnes/year

5.5 tonnes per person in UK

50% goes on road & 50% on concrete

Small amount of dimension stone

More than half the aggregates come from crushed rock (60 %); the rest is sand and gravel (40 %)

Rock strength is the prime requirement, usually UCS > 100 MPa

Main size required is 5 – 50 mm

1.

Economics of UK Aggregates Aggregate consumption

linked with demand from construction industry

Consumption of primary aggregates decreasing since 1989 because of: Decline of manufacturing

economy, road construction & house building

Construction methods

Aggregates used economically

Introduction of landfill tax &

Rise of recycled aggregates

Less demand for primary

1.

Primary Aggregates R

ock

Typ

es

Cut or crushed Fired Mixed Uses

2.

Extracted directly from mineral by quarrying or dredging to become aggregate

Treatment & uses of primary aggregates

Primary Aggregates in the Home 2.

Building

materials and

their mineral

‘ingredients’

UK Aggregate Quarries

BGS mineral planning factsheet

2.

Limestone Quarries

Igneous & Metamorphic

Quarries Sandstone Quarries

Dimension Stone: Building Stone

Bath Abbey constructed of

Oolitic Jurassic Limestone

Edinburgh Castle

constructed of Carboniferous

Sandstone

2.

Dimension stone is quarried

rock used in large blocks;

Some is cut and used as a

building stone or cladding stone

Dimension Stone: Armourstone

Soton.ac.uk

2.

Rough blocks used as

rock armour in coastal

defences to protect

against coastal

erosion

Crushed Stone Aggregates

Crushed stone aggregates can

be either single size or variable

depending on application

Concrete & gabion fill require

single size aggregates

2.

Road Aggregates

Igneous & some metamorphic rocks

are good road stone because;

High rock strength and resistance to

impact, abrasion, polishing, skidding

and frost action;

Laboratory rock property testing

2.

Road surfaces built up of a series of

layers & topped with three layers of

asphalt.

Each asphalt layer uses different

aggregate sizes (fining upwards)

Asphalt is a mix of bitumen & crushed

rock

Outside the Chancellor’s Office on campus

Laboratory property testing of aggregates Aggregate Abrasion Test (AAV)

Slake Durability Test

Aggregate Impact Test (AIV)

3.

5 kg sample is

rotated at 30

revolutions per

minute with 11 steel

balls

15 ‘shock’ blows and sieved

to measure weight lost

Standard aggregate tests

Property Test Procedure Good

value

Poor

value

Road stone

value

AIV - Aggregate

impact value

% fines lost by hammering on standard rig 5 35 <20

AAV- Aggregate

abrasion value

% loss by abrasion on standard rig 1 25 <10

PSV-polishing

stone value

Frictional drag recorded by swinging pendulum 70 30 >60

ACV-aggregate

crushing value

% fines lost by uniform load crushing on a

standard rig

5 35

10% FV – 10%

fines value

Load on an ACV rig to give 10% fines loss 400 20 >100

Flakiness index Weight % particles with minimum thickness<60%

mean

20 70 <3

CBR- California

bearing ratio

Resistance to plunger penetration compared to a

standard

100 60 >90

Water absorption Weight % increase after immersion in water for

24hrs

0.2 10 <2

Frost heave Heave of air-cooled column of sample standing in

water

3 20 <1

3.

For a rock to be used as a road stone it must possess certain properties:

Typical UK aggregate properties

Material Location 10%

FV

AIV AAV PSV

Granite Dartmoor 280 16 5 60

Dolerite North Pennines 360 10 4 60

Greywacke Pennines 220 14 7 65

Limestone Pennines 120 20 12 40

Flint Thames gravels 450 23 1 35

Coarse sandstone Peak District 90 40 26 74

3.

10% Fines Value: a measure of aggregate strength

The load applied to an aggregate sample to cause 10 % loss of

fines. Uses aggregate crushing rig (ACV).

How UK aggregates compare to essential road stone properties:

Red indicates road stone

property criteria fulfilled

http://www.youtube.com/watch?v=UW7iRsut4ck

Tarmac Swinden Limestone Quarry, Cracoe,

North Yorkshire Fairport.co.uk

What are the 6 processes of quarrying?

3.

Quarrying for Crushed Stone Aggregates 3.

Quarrying for Crushed Stone Aggregates 3.

Drilling & blasting

Conveying

Secondary crushing Sorting

Schematic diagram of an impact crusher 3.

Used for secondary

crushing stage of

quarrying

Stones then go to

sorting

Laboratory impact crusher

Size-specific filter

Gravels & Sands Land-won or marine deposits

BGS mineral planning factsheet

2.

Locations of pits and a

licensed dredging area for

sands & gravels

Gravels & Sands

• Superficial deposits are sediments

deposited within the last 2 million

years mostly during interstadials

• River sands & gravels deposited in

major river valleys or terraces

• 1 -10 m thick deposits

• Well sorted and often mature

2.

Land-won aggregates can be either superficial deposits or

bedrock

Gravels & Sands

• Superficial deposits are sediments

deposited within the last 2 million

years mostly during interstadials

• River sands & gravels deposited in

major river valleys or terraces

• 1 -10 m thick deposits

• Well sorted and often mature

2.

Land-won aggregates can be either superficial deposits or

bedrock

Gravels & Sands

• Bedrock deposits

• Include poorly-consolidated:

• Sands of Lower Cretaceous

Folkestone Formation of the Weald

• Conglomerates of Triassic Sherwood

Sandstone Formation in the Midlands

2.

Land-won aggregates can be either superficial deposits or

bedrock

Marine Gravels & Sands • Marine aggregates are dredged

from the seabed

• Relict quaternary fluvial deposits,

deposited when sea-level much

lower during glacial maxima

• Dredging takes place less than 25

km offshore in 18-35 m depth

• Extraction constrained by pipelines,

cable routes, wind farms, fisheries &

shipping lanes

• Most important regions are offshore

Norfolk, Humber-Wash area and

Bristol Channel

2.

Secondary & recycled aggregates

Construction & demolition

wastes such as concrete and

masonry are the largest source

of recycled aggregates.

60 % of C&D waste currently

used as construction fill.

By-products of quarrying &

mining operations are the

main source of secondary

aggregate

Geograph.org

Imerys exporting china clay waste to South-

east & Germany as a mortar replacement

2.

Hallsands village:

This south Devon village stood on a rock platform with a protective beach

in front of it. In 1887 offshore shingle dredging steepened the seabed

sediment profile. Natural response was lowering and removal of the beach

within 5 years, exposing the houses to wave attack. The village was

destroyed in a storm in 1917. The shingle was used in the construction of the

Devonport docks.

Environmental Impact of Dredging 4.

Before dredging After dredging

Aggregate Resource Planning Extractable resources (reserves) can be extracted as they are

an economically viable commodity

‘Conditional

resources’ have

been discovered

but are not

economically viable

4.

Economic viability

governed by

price:cost ratio;

a function of mineral

grade,

concentration,

market price

Bulk Resources &

Aggregates

1. Uses & Economics in UK

2. Types & Sources

3. Processing & Testing

4. Environmental Impact

Summary

Aggregates and water are the major

resources investigated by applied

geoscientists outside the hydrocarbons and

metaliferous industries

Aggregate testing is carried out according to

Eurocode 7 and BS 812

Assessment of reserves requires a detailed

understanding of the geology

Ground subsidence associated with mine

workings

a)Failure in old pillar and stall workings or bell pits

b)Effects of multiple pillar collapses

c)Long wall mining effects

Hazard zoning over old workings: Coal outcrop

positions, dip directions and dip amount are sufficient to

identify zones on a geological map of the site where

shallow mining could occur - figure assumes collapse of

voids in seams >30m bgl unlikely to reach the surface