bigger = better - Development Bank of Southern Africa · 2014-01-28 · Track record – HVS...
Transcript of bigger = better - Development Bank of Southern Africa · 2014-01-28 · Track record – HVS...
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bigger = better
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Thicker = stronger
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A man walking on the moon?
No ways!
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concrete = rigid?
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innovation = flexibility
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Join us on the road to
innovation …
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Inspired ideas It all started…
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Inspired ideas
In the USA: Iowa
• Showcase: Road consisting of 100mm both un-reinforced and reinforced pavement
• Results: After 15 year performance, mesh reinforced pavement showed excellent results (1 100 vpd 4 – 4,5 % heavy)
In RSA: Gauteng
• 60mm concrete slab of the first floor slab of an old house, lightly reinforced with steel wires
• CSIR test section at access road to Roodekranz Quarry
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Our subject?
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UTRCP: Ultra Thin Reinforced Concrete Pavement (50mm)
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Layerworks: Ultra Thin Reinforced Concrete Pavement (UTRCP)
Cape Seal
150 mm G5
imported subbase
compacted to 95%
mod. AASHTO
50 mm UTRCP
150 mm In-situ layer compacted
to 95% mod.
AASHTO
150 mm In-situ
layer compacted
to 93% mod.
AASHTO
Typical Cape Seal Design UTRCP Design
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Track record – HVS testing
Design repetitions: 300 000 E80’s
No failure at 2 000 000 E80’s repetitions (166 days, 900 mm rainfall)
Failure after 2 346 920 E80’s plus 24/7 water drip
(equivalent to 2 000 mm rainfall)
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Application Residential
Alternatives Cape Seal Asphalt
Block Paving
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Lessons Learned ………
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Communities
Lessons learned
• Communication programme to create understanding of
concrete roads and the benefits thereof – BUY-IN
• Opportunity to create more jobs compared to similar surfacings
• SMME contractors can be employed
• Supervisors trained in concrete and LIC skills
• Community training in concrete skills
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• Reduced layer works – limit damage to existing underground
services
• Fly ash, waste product can be used
• Less cut and spoil
• Less borrow from borrow pits
Lessons learned
Natural Resources
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• Local small maintenance teams (work with concrete)
• Savings in terms of lower life cycle costs
• Currently grant incentives can be claimed under EPWP-2
• Job creation
Lessons learned
Authorities
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Asphalt 1
Block paving 4
Cape seal
5
UTRCP 15
Lessons learned – Job Creation
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• Training in technical skills crucial (especially concrete and LIC methods)
• Establishing balanced teams (workers and equipment)
• Site administration and record keeping
• Quality Assurance systems
Lessons learned
SMME Contractors
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• Shaping – preferred final shaping by grader, tolerance + 5 mm
• Alignment – provide levels at 10 m intervals
• Compaction – recommend 95 % mod AASHTO
• No ETB used, apply 1:8 diluted emulsion
• Stabilize material with high PIs
Lessons learned
Construction PREPERATION OF ROAD BED
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• Must be robust to withstand handling on site
• 50 mm box sections in 2 m (max) lengths
• Securely fixed to carry vibrating beam/spin screed
Lessons learned
Construction SHUTTERS
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• 3 lugs per shutter to hold in place
• Straight edge across shutter
• Vertical and horizontal alignment of joints
• Use clean 1mm x 300mm wide galvanising sheet strip on
existing concrete as shutter
• Pegs through lugs to secure shutter
Lessons learned
Construction FIXING SHUTTERS
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• Sizing, fixing and transporting on flat truck
• Protecting while placing concrete, use bridge
• Sufficient overlapping
• Use factory sizes – 2.4m x 6m
• Position in centre of slab
Lessons learned
Construction MESH REINFORCEMENT
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MATERIALS, PROCESS AND QUALITY CONTROL CRITICAL
• Mix design – use same type and source of cement
• Batching and mixing – method and controls
• Testing – slump and cube strengths
• Placing asap after mixing, steel squeegees
• Screeding and finishing
• Texturing – light broom
• Covering and protecting with canopy
• Curing asap, secure plastic and cleaning
Lessons learned
Construction CONCRETE
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• Vibrating beams sagging and breaking – spin screed more durable.
• Proper spreading of concrete prior to screeding.
• End of day joint, prevent leaching.
• End beams when delays are experienced.
• Method specification for :
• road markings; and
• speed humps
Lessons learned
Construction CONSTRUCTION PROCESS AND FINISHING
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• Reconstituted bottom dump ash from SASOL (continuous
grading)
• Plasticizer (currently being considered)
Lessons learned
Construction ADD MIXTURES
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REPAIRS TESTED WITH HVS
• Trenching for services with backfill and compaction by hand
• Potholes at failed sections were cut, cleaned, mesh replaced
with overlap and filled with concrete
Lessons learned
Trenching and repairs
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• Mix design must be finalized before construction starts:
• Type of Cement is to be specified or agreed upon by means of mix-design.
• No changes without new mix design and approval
• A very accurate site diary must be kept to record:
• Where concrete was placed
• Weather conditions of that day
• Slumps and cube testing details
Lessons learned
Quality assurance MATERIALS
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• Curing is a critical element in the development of concrete strength
• Samples must be kept on site at all times to allow the consultant regular inspections
• Close supervision on the use of materials. Should materials require change, a material grading must be done and submitted to the engineers for approval
• All materials used must be clean of all types of contamination
• Slump tests and cube testing
Lessons learned
Quality assurance MATERIALS
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R 140
Lessons learned
Costing PAVEMENT COSTS (R/m2)
* Excluding storm water & ancillary work
R 181 Asphalt
R 156
Block paving R 256 R 257
Cape seal R 128 R 171
UTRCP R 139
Life Cycle Costs (25 yr) Construction costs
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Lessons learned
Costing PROJECT COST DISTRIBUTION AND JOBS CREATED
Description Soshanguve Mamelodi (Section 6)
Atteridgeville George
Total Project Cost (inc VAT) R 8 913 085 R 4 389 277 R 6 471 803 R 3 909 681
% Cost of UTRCP & layer works in relation to total project cost
18 % 29 % 26 % 8 %
Jobs created with UTRCP & layer works
4 448 2 802 4 480 588
Construction cost per job created with UTRCP & layer works
R 360 R 375 R 468 R 503
% Cost of UTRCP & layer works to labour *
19.5 % 15 % 18.7 % 20 %
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Lessons learned
Costing % COST OF UTRCP = Total Project Cost
26%
29%
21%
8%
11%
5%
UTRCP - Mamelodi (Section 6)
P&Gs & Ancillary works
UTRCP & Layerworks
Stormwater
Kerbing
Sidewalks
Roadsigns and trafficcalming
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Tshwane Status Quo 4,4 km UTRCP roads completed
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Excellence Recognitions
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Excellence
“The innovative thought processes that this design team applied……..is impressive.…
The skills transfer processes, opportunities for the upliftment of local communities, as well as promotion of BEE contractors as a result, is applauded.”
Fulton Commendation Award
Unique Design Aspects
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Excellence
SAICE National Award Most outstanding Civil Engineering Achievement in the Community -Based Category
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Conclusions
• Based on observations
• Engineering principles and experience Approach
• Extensive tests by University of Pretoria
• HVS tests by Gauteng DPTRW
• Guidelines developed by CSIR Research
• Based on present knowledge and experience.
• Suitable for urban streets and bus routes – 3 000 vpd with 5 – 7% heavy vehicles
Application
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Thank you