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transcript
Roller Compacted Concrete in UK
Experiences and Opportunities
ERMCO Representatives Meeting
Cascais, 7 June 2013
Steve Crompton, MBA, B.Eng, MICT
National Technical Director
Cemex UK
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Contents
Background – Why RCC now?
What is RCC
– Production
– Installation
– QC
Applications
Pavement design
Additional benefits of RCC
Case studies and opportunities
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The use of asphalt in UK infrastructure is
often deemed to be the only option to fulfil
the requirements of modern day contracts
Background
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0
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35
40
Background
Economic pressures driving ‘More for Less’
The UK Asphalt Market
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BITUMEN 36%
AGGREGATES 29%
HAULAGE 11%
FUEL 9%
FC 8%
OVERHEADS 3%
OTHER VARIABLE COST
2%
ELECTRIC POWER 1% OTHER RAW
MATERIALS 1%
Background
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BLS Inflation Indexes since Jan 1971
0
200
400
600
800
1,000
1,200
1,400
1,600
1,800
Jan
-71
Jan
-74
Jan
-77
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-86
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-89
Jan
-92
Jan
-95
Jan
-98
Jan
-01
Jan
-04
Jan
-07
Jan
-10
Pri
ce I
nd
ex (
Base Y
ear
= 1
971)
Paving Asphalt (CAGR=6.9%)
Cement (CAGR=4.3%)
Ready Mix Concrete (CAGR=4.7%)
Aggregate (CAGR=4.7%)
PPI-Commodities (CAGR=4.3%)
CPI (CAGR=4.4%)
(Data thru June 2011)
Paving Asphalt
All Other Indexes
BLS Inflation Indexes since Jan 1971BLS Inflation Indexes since Jan 1971
0
200
400
600
800
1,000
1,200
1,400
1,600
1,800
Jan
-71
Jan
-74
Jan
-77
Jan
-80
Jan
-83
Jan
-86
Jan
-89
Jan
-92
Jan
-95
Jan
-98
Jan
-01
Jan
-04
Jan
-07
Jan
-10
Pri
ce I
nd
ex (
Base Y
ear
= 1
971)
Paving Asphalt (CAGR=6.9%)
Cement (CAGR=4.3%)
Ready Mix Concrete (CAGR=4.7%)
Aggregate (CAGR=4.7%)
PPI-Commodities (CAGR=4.3%)
CPI (CAGR=4.4%)
(Data thru June 2011)
Paving Asphalt
All Other Indexes
-40%
-20%
0%
20%
40%
60%
80%
100%
120%
140%
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An
nu
al
Infl
ati
on
Rate
(%
)
CPI (Avg=4.4%, St Dev =3.1%)
PPI-Commodities (Avg=4.3%, St Dev =5.6%)
Aggregate (Avg =4.8%, St Dev =3.4%)
Ready Mix Conc. (Avg =4.4%, St Dev =4.5%)
Cement (Avg=4.4%, St Dev =5.8%)
Paving Asphalt (Avg=8.4%, St Dev =20.9%)
Paving Asphalt’s 40-year historical rate is 2 to 4% higher than the general rate of inflation
(higher than concrete and cement’s and much more volatile)
Background
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Background
So why the reliance on asphalt?
‘Time is Money’
+
‘Sticking Plaster’ approach to infrastructure maintenance
+
Tradition ?
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Definition: “Roller Compacted Concrete is a no-slump concrete placed by an asphalt paver
and compacted by rollers”
Materials are same as concrete – well graded, angular aggregates, cement, and water – but
different mixture proportions. (Cement content around 300kg/m3)
Zero slump (consistency of damp aggregate)
No pavement formwork, consolidated with paver and vibratory rollers
No reinforcing steel
After curing, RCC properties and performance are similar to PQ concrete
What is RCC?
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RCC is a blend of asphalt & concrete Paving technologies
Hot-Mix Asphalt Pavement Conventional Concrete Pavement
Shared construction characteristics
Similar aggregate gradation
Similar placement and compaction
Shared materials characteristics
Same materials (different proportions)
Similar curing requirements
What is RCC?
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• Mid size applications
• 100 to 150 tons/hr
• Not all plants have mixers
• Fixed locations
• Capacity reduced due to low
water content of mixture
• High-volume applications
• Excellent mixing efficiency for dry
materials
• Consistent mix properties
• 250 to 600+ tons/hr
• Mobile, erected on site
• Lower mobilization costs
Central Mix Continuous Flow Pugmill
Production
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Standard paver (80% to 85% initial density)
Widely available
High-production (4 to 6 m/min)
Lift thickness up to 150mm
May require multiple lift paving
– Impossible to pave adjacent lanes
Increased roll down to achieve density (grade control problems)
Easier to fix segregated areas before compaction
• High density screed
• High initial density (> 90%)
• Smoother surface with higher initial density
• Less roll down from to achieve density
• High production (4 to 6 m/min)
• Lift thickness up to 250mm
• Adjacent lanes easily paved
Standard Paver High Density Paver
Installation
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Initial: 10 - 12 ton static & vibratory roller
– Thinner lifts may allow smaller roller
Establish roll pattern (check density a lot!)
Adjust based on moisture content (visual observation and lab measurements to confirm)
Compact to 98% of maximum wet density
Adjust moisture content if needed – impacts smoothness
Finer mixes achieve density easier
• Final: Combination, dual steel or rubber tired
• Maximum weight - 6 ton
• Remove roller marks
• NO MORE ROLLING!
Initial Compaction Finish Rolling
Compaction
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Density tested with nuclear gauge in direct transmission mode
Test density behind paver and after roller to establish rolling patterns to achieve density
Continuously check density until comfortable
Achieve 98% of maximum wet density
Nuclear gauge gives general moisture fluctuation indication
• Cubes prepared with vibratory hammer
• 3 to 4 cubes per set
• Strength timing depends on traffic opening (1, 3, 7, 28 days)
• Cores can be obtained where density is not being achieved
Compressive Strength Moisture & Density
Quality Control
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• Applied at same rate or slightly higher than conventional concrete
• Ensure uniformity with application process
• Apply as soon as possible behind roller operation
• Ensures durable surface
Curing Saw Cut & Fill Joints
• More aesthetically pleasing
• Early entry saw very effective, shortly following placement
• Recommend sawing within 2 - 6 hours to avoid uncontrolled cracking
• Depth: 1” to 1.5”
• Spacing: Maximum 36 times thickness, Max 6m
Finishing Touches
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The Difference?
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The ‘Time’ Issue
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Industrial
Dockyard
Container storage
Airfield refuelling areas
Roads ?
Applications
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HBM
(Flexible Composite)
Asphalt
(Fully Flexible)
Pavement Design
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RCC does theoretically fit into to the HBM ‘family’ of materials
But.... the compressive strength of RCC is much higher (C32/40 +)
Therefore no design option is available for RCC in this methodology
Pavement Design
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Pavement Design
Still a requirement for 100 to 180mm of asphalt overlay
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Surface Course
Capping
Subgrade
CBGM
Sub-base
RCC
Potential option
Asphalt surface course to achieve:
Skid resistance and noise
reduction
Would require formal RCC
specification which in turn would
allow inclusion in design charts
Pavement Design
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Benefits of RCC
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Pavement Cost Analysis
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$0,64
$0,5
Nom Disc Rate=8%
$0,34
$0,03
$0,50
$0,04
$0,19
$0,05
$0,46
$1.65
$0,4 $0,4
$0,9 $0,9
0 5 6 10 13 15 16 18 24 25 28 30 34 35 38 40 45 50
Rehabilitation – Activities based on Proper Maintenance Cycles for asphalt pavements. Current year costs are inflated at 4%, Rehab costs also include other
Incidental Costs (striping, mob, etc) - 40% of material costs, Traffic Control - 5% of material cost, and Engineering & Inspection - 5% of material cost
Nominal Expenditures by Pavement Type Total Cost Net Present Value
M $
M $
In this example Asphalt is 26% more expensive than RCC throughout the life
cycle of the road
year
Asphalt – Rehab: Crack / cape sealing in years 6, 13, 16, 24, 34, 38
Microsurfacing in years 10, 28
Major rehab in year 18 (2” OLAY + PDR)
Major Rehab in year 45 (Full Replace)
PCC – Rehab: Patch & diamond grind at years 25, 35, 2” AC Overlay at yr 45
26 %
Life Cycle Cost Analysis
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Cost Issues
Cementitious options now cheaper to build
Reduced maintenance
Longer life
Lower whole life cost
More traffic per £ invested
On going fuel and environmental savings
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Added Benefit Reducing Fuel Use
Many world wide studies show fuel savings for rigid pavement construction
• 6% Eupave • 2.4% NRC, Canada • 6.7% NRT, Sweden • 3.1% NRI, Japan • 1.1% TRL, UK • 5.8% University of Texas, USA
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Added Benefit – Rolling Resistance
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The Noise Issue
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0 5 10OB
SI S
ou
nd
Level
(d
BA
)
Pavement Age
Asphalt Surface –
ARFC / OGFC
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0 5 10OB
SI S
ou
nd
Level
(d
BA
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Pavement Age
Concrete Surface -
NGCS
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Advances in Noise Reduction
An innovative, diamond saw-cut surface designed to provide a consistent profile absent of positive or upward
texture
• A uniform land profile design with a predominantly negative texture
• A hybrid texture that resembles a combination of diamond grinding (called flush grind) and longitudinal
grinding
• Can be done as a single step or a 2 step process
• Visit www.ngcs.info for 25 additional references on the pavement surface type
• Could compete with HRA in terms of noise
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Further Benefits - Lighting
US studies have suggested that up to 30% saving in artificial lighting cost can be
achieved by using a light coloured surface
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CASE STUDIES
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Druids Heath Bus Terminus
Asphalt RCC
CBR 15 15
Subbase 150mm 150mm
Pavement 260mm 200mm
Overall 410mm 350mm
•Repeated heavy loading of parked buses
•Oil spillage
•Disruption to public transport, congestion if re-routing employed
•Options were asphalt or RCC
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Druids Heath Bus Terminus
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• Transverse joints cut every 4 – 5 metres
• Cut using dry blade to one third of the depth
• Filled with bitumen emulsion prior to rolling
Druids Heath Bus Terminus
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Druids Heath Bus Terminus
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Impetus Waste Transfer
PAV 2 RCC
CBR 10 10
Subbase 150mm 150mm
Pavement 400mm 400mm
Overall 550mm 550mm
Program 16 weeks 6 weeks
• Large storage area for compost waste
• Difficult ground conditions
• Time pressure on program
• No asphalt design option
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Impetus Waste Transfer
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Impetus Waste Transfer
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Impetus Waste Transfer
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Current Applications in UK
• Lorry & Trailer Parking
• Container Storage & Handling
• Materials Storage & Handling
• Composting Hardstandings
• Waste Recycling Sites
• Heavy Industrial Access Roads
• Farm Roads
• Port Pavements
• Fuel Resistant Applications
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Future Applications in UK
HIGHWAYS
Highway Agency & Local Authorities
Under consideration, with induced
cracking and surface course
for bus lanes, motorway widening and as
an alternative to
fully flexible pavements
AIRFIELDS
May require surface course
Ideal for Taxi Ways & Airplane Stands
NEW BUILD HOUSING
Composite solutions under consideration
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Summary
• RCC is not a new product
• Economics are driving contractors to seek ‘more (and more) for less’
• The challenge is to improve understanding and knowledge of RCC
• Specifications and design charts need to include RCC as an option
• RCC has all the attributes of concrete, with the installation speed of asphalt
• Concrete paving is becoming a viable economic and sustainable option in many
applications
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Conclusions
Lower initial cost
Lower lifetime cost
Less maintenance
Lower Fuel usage
Lower CO2 emissions from road traffic
Economic benefits through lower fuel use
More road miles per £ invested
Predictable cost inflation
A better way to build pavements!
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Thank You