Paving operations
Forming time & retempering under RMS R83 & R82
Geoff AytonSupervising Pavement Engineer (Rigid)Engineering Technology Services BranchRoads & Maritime Services24 February 2014
forming time
R83 Ed2 Rev8
Systematic consideration of: • mix characteristics & admixtures• weather conditions• your paving equipment etc
Mark Elliott - ex Abigroup (circa 1992)Mark Elliott - ex Abigroup (circa 1992)
Systematic consideration of: • mix characteristics & admixtures• weather conditions• your paving equipment etc
Charging
Mixing
"Batching""Batching""Batching"
Slump adjustment
10 mins max10 mins max "Completion of Batching""Completion of Batching""Completion of Batching"
Haul
Retemper& remix
SlumpSpread, compact& form
Finish, texture & cureFinish, texture & cure
Contractor to nominate& monitor under Cl 4.2.2 Contractor to Contractor to nominatenominate&& monitor undermonitor under Cl 4.2.2 Cl 4.2.2
"Forming Time""Forming Time""Forming Time"
(maybe)
Charging
Mixing
"Batching""Batching""Batching"
Slump adjustment
10 mins max10 mins max "Completion of Batching""Completion of Batching""Completion of Batching"
Haul
Retemper& remix
SlumpSpread, compact& form
Finish, texture & cureFinish, texture & cure
"Forming Time""Forming Time""Forming Time"Contractor to nominate& monitor under Cl 4.2.2 Contractor to Contractor to nominatenominate&& monitor undermonitor under Cl 4.2.2 Cl 4.2.2
forming time
Cl A4.2(c):The Contractor’s production and transport must .... :
(c) result in workability, at the time of incorporation,which is compatible with the capacity of the pavingequipment to achieve the specified compaction andsurface finish requiring only nominal manualfinishing.”
CRCP Overlay(North of Holbrook)
~2 hours old, but still OK~2 hours old, but still OK
forming time
• mix characteristics (set retardation etc)• season & weather conditions• slipforming vs hand-forming• paver mass• vibrator intensity
Relevant factors:
CRCP Overlay(North of Holbrook)
~2 hours old, but still OK~2 hours old, but still OK
.... again no mention of maximum forming time
but a fixed forming time is nonconforming under R83 !!
xxxxx ....
2 paragraphs later ....
from another project < 2 years ago ...
R83
• all determined long before they even began paving ....• not consistent with the intent ....
Project Quality Plan
Retempering under RMS R83 & R82
- prompted by an RMS Senior Project Manager- apologies to Grey Card holders
Charging
Mixing
"Batching""Batching"
Slump adjustment
10 mins max "Completion of Batching""Completion of Batching"
Slump adjustment
Haul
Retemper& remix
SlumpSpread, compact& form
Finish, texture & cureFinish, texture & cure
40 mins max40 mins max
(maybe)(maybe)
(for the purpose of"age of batch")
(for the purpose of"age of batch")
Time 0Time 0
50 mins max
w/c ratio
Mix 1
Is slump a reasonable indicator of w/c ?
(for a given temperature etc)
0.3 0.4 0.5 0.6
Slump(mm)
6060
100100
8080
4040
Mix 3
Mix 2
for a specific mix: Yes(all other factors being equal)
Slump(mm)
Time (mins)
6060
100100
8080
4040
00 2020 4040 6060 8080 100100 120120
Mix A
Mix B
Mix C
90
Mix variations
(for example)
Slump(mm)
Time (mins)
6060
100100
8080
4040
00 2020 4040 6060 8080 100100 12012090
Mix variations
autumn
wintersummer
- season / temperature
(for example)
Mix B
Slump(mm)
Time (mins)
6060
100100
8080
4040
00 2020 4040 6060 8080 100100 12012090
Mix variations
autumn
wintersummer
- season / temperature
(for example)
Mix B
butfor a specific mixunder uniform conditions ....slump is a useful indicator of
* age and/or* w/c ratio
Cement hydration with time
crystalline "velcro" growthCement grains ~~ Velcro tennis balls
(Human hair ~100 um)??
Cement hydration with time
crystalline "velcro" growthCement grains ~~ Velcro tennis balls
??
Higher w/c ratio :greater spacing between velcro ballslower velcro densityslower strength gainlower ultimate strength
Time
SlumpSlump
40 mins
nonconformingretempering
slumpadjustment
60mm60mm
Dormant period Dormant period
0
" Completion of batching”" Completion of batching”
absorption and/or
evaporation
absorptionand/or
evaporation+ hydration+ hydration
10 mins
Conditions !Conditions !
normal temperature conditions (both air~ & concrete~)normal temperature conditions (both air~ & concrete~)
Ordinary Portland cement (OPC, ie not HES cement)Ordinary Portland cement (OPC, ie not HES cement)
no accelerators (such as CaClno accelerators (such as CaCl22))
no highno high--range water reducers (at this stage)range water reducers (at this stage)
Cement hydration with time
water/cement ratio
• Aggregates @ SSD (saturated surface dry)
The trial mixThe trial mix
water/cement ratio (w/c):
60 mmslump
(say)
400400 kg PCkg PC= 0.5= 0.5200200 kg kg HH22OOegeg
• the absorbed water doesn’t count in the w/c ratioso SSD is the assumed default condition for all aggregates
Quick quizz: is the absorbed water counted ?
The trial mixThe trial mix 400400 kg PCkg PC= 0.5= 0.5200200 kg kg HH22OOegeg
water/cement ratio
• Aggregates @ SSD (saturated surface dry)
• the absorbed water doesn’t count in the w/c ratioso SSD is the assumed default condition for all aggregates
Time
Slump
40 mins
nonconformingretempering
slumpadjustment
60mm60mm
Dormant period Dormant period
0
absorption and/or
evaporation
absorptionand/or
evaporation+ hydration
Water/cement & Slump
under RMS specs R82, R83, R84under RMS specs R82, R83, R84and AS 1379and AS 1379
Time
Slump
Slump adjustment & retempering
0
N N ±± 15 mm15 mm
“Completion of batching”“Completion of batching”
N mmN mm 60 60 ±± 15 mm15 mm
N = nominated slumpN = nominated slump
7575
4545
60mm60mmconformance windowconformance window
40 mins
(under RMS specs R82, R83, R84)(under RMS specs R82, R83, R84)
Slump
60mm60mm
0
workability limitworkability limit
"Forming"FormingTime"Time"
((R83 Cl 4.2.2)R83 Cl 4.2.2)
7575
4545
“Completion of batching”“Completion of batching”
Slump adjustment & retempering
80 mins (say)
(1) Quality of concrete(as supplied)
(2) Quality of construction
40 mins
30
(under RMS specs R82, R83, R84)(under RMS specs R82, R83, R84)
Slump
60mm60mm
0
workability limitworkability limit
"Forming"FormingTime"Time"
((R83 Cl 4.2.2)R83 Cl 4.2.2)
7575
4545
“Completion of batching”“Completion of batching”
Slump adjustment & retempering
80 mins (say)
(1) Quality of concrete(as supplied)
(2) Quality of construction
40 mins
R83 industry review
10 mins
(under RMS specs R82, R83, R84)(under RMS specs R82, R83, R84)
Slump
60mm60mm
0 "Forming"FormingTime"Time"
((R83 Cl 4.2.2)R83 Cl 4.2.2)
7575
4545
“Completion of batching”“Completion of batching”
Slump adjustment & retempering
40 mins10 mins
absorption absorption (?)(?)
hydration hydration (?)(?)
??
Time
Slump
0
“Completion of batching”“Completion of batching”
7575
4545
60mm60mm
20
4040
Case study 1Case study 1
5555
identical mix, inclidentical mix, incl
same same added wateradded water
wet aggregateswet aggregates
ovenoven--dry aggregatesdry aggregates
except :except :
??
40 mins
7575
4545
Slump
60mm60mm
0
Case study 2Case study 2aa
8585
conformingconforming
“Completion of batching”“Completion of batching”
Time
acceptable ?acceptable ?
suggests a mixing problemsuggests a mixing problem
40 mins
(as long as the load has been agitated or re-mixed)
7575
4545
Slump
60mm60mm
0
Case study 3
“Completion of batching”“Completion of batching”
Time
??
20
4040
??
OK to retemper (on conditions)must re-check slumpsuggests a mixing problem(Wodonga Place, Albury. 1990s)
OK to retemper (on conditions)must re-check slumpsuggests a mixing problem(Wodonga Place, Albury. 1990s)
(after partial(after partialdischarge)discharge)
Becomes unworkable afterpartial discharge.
40
What if you were controlling by w/c ratio ?
Slump adjustment & retempering
100
150
Supe
rplas
ticise
r
40
100
Are these "similar" mixes ?
If you don't test initial slump (pre-HRWR*), how will you know what you've got ?
* HRWR:High range water reducer(superplasticiser)
End product vs method
(with a questionable response)
Beware the unconscious ignorant !!Beware the unconscious ignorant !!
End product vs method
"... a young contractor's interpretation of R83 was basically that Clause 5 (End Product Criteria) is all that 'really matters' and that if these requirements are met, any other non conformances don't justify NCRs."
My response:What about all the missing "End product criteria" for properties like:• mixing uniformity in the pavement (?)• uniform compaction throughout a Lot (?)• w/c ratio in the finished pavement (?)
Following a project audit:
(under RMS specs R82, R83, R84)(under RMS specs R82, R83, R84)
Slump
60mm60mm
0
7575
4545
“Completion of batching”“Completion of batching”
Slump adjustment & retempering
40 mins
absorption absorption (?)(?)
hydration hydration (?)(?)
??
80 mins
End product assessment ?