-- -- S k S k Annual Concrete Seminar 2009 Annual Concrete Seminar 2009 Concrete for Repairs in Existing Buildings Concrete for Repairs in Existing Buildings -- -- Concrete for Achieving a Sustainable Environment Concrete for Achieving a Sustainable Environment Concrete for Repairs in Existing Buildings Concrete for Repairs in Existing Buildings an Integrated Development Approach an Integrated Development Approach Speakers: Speakers: Introduction & Part I Introduction & Part I ………………………… ………………………….. Ir K.C. Lau .. Ir K.C. Lau Part IIa Part IIa ……………………… ……………………….…………………… …………………… Ir K.C. Lau Ir K.C. Lau 1 Part IIb Part IIb ……………………………… ……………………………….…………… …………… Ir W.B. Chan Ir W.B. Chan
Concrete for Repairs in Existing BuildingsConcrete for Repairs in Existing Buildings ----
Concrete for Achieving a Sustainable EnvironmentConcrete for Achieving a Sustainable Environment
Concrete for Repairs in Existing BuildingsConcrete for Repairs in Existing Buildings an Integrated Development Approachan Integrated Development Approach
Speakers:Speakers:
Introduction & Part IIntroduction & Part I …………………………………………………….. Ir K.C. Lau.. Ir K.C. Lau
Part IIaPart IIa ………………………………………………..………………………………………… Ir K.C. LauIr K.C. Lau
11
Part IIbPart IIb ………………………………………………………………..………………………… Ir W.B. ChanIr W.B. Chan
e e a e a an appe e a e a an app
qq
i i i d i fi i i d i f
in a in a
Integrated Development ApproachIntegrated Development ApproachIntroductionIntegrated Development ApproachIntegrated Development Approach In the process of our structural related repair works forIn the process of our structural related repair works for
isting b ildings dopting oach ofisting b ildings dopting oach of
Introduction
¾¾ with thewith the industries experts & specialistsindustries experts & specialists
existing buildings, we are adopting an approach ofexisting buildings, we are adopting an approach of integratingintegrating::
industries ¾¾ with thewith the industries, experts & specialistsindustries, experts & specialists zz in researching, developing and introducing newin researching, developing and introducing new
construction techniques and materialsconstruction techniques and materials
industries
zz in achieving effective and economic ways to sustainin achieving effective and economic ways to sustain our buildingsour buildings
zz incorporating our experiences and views ofincorporating our experiences and views of stakeholdersstakeholders
zz in creating a peoplein creating a people--oriented, continuously improving,oriented, continuously improving,
22
creating peoplecreating people oriented, continuously improving,oriented, continuously improving,safe, comfortable and healthy living environment thatsafe, comfortable and healthy living environment thatcan meet our tenants’ needscan meet our tenants’ needs
CSIPCSIP
qq
ii
Integrated DevelopmentIntegrated Development ProcessProcess identify needs,identify needs,
defects & constraintsdefects & constraints
Integrated DevelopmentIntegrated Development ProcessProcess
formulateformulate requirementsrequirements
implementationimplementationour CSIPour CSIP
develop repairdevelop repair methodsmethods
ourour
IndustriesIndustries
HousingHousingspecificationsspecifications
laboratorylaboratory trials & teststrials & tests
technicaltechnical ourour
industryindustry expertsexperts
TrialsTrials & Tests& Tests
trials & teststrials & tests
simulation trialssimulation trials
reviewsreviewsourour DrDr our SEsour SEs
33 onon--sitesite
actual trialsactual trials
our Drour Dr & SSEs& SSEs
----
Concrete for Repairs in Existing BuildingsConcrete for Repairs in Existing Buildings ----Concrete for RepairsConcrete for Repairs Existing BuildingsExisting BuildingsConcrete for Repairs in Existing BuildingsConcrete for Repairs in Existing Buildingsan Integrated Development Approachan Integrated Development Approach
Concrete for RepairsConcrete for Repairs Existing BuildingsExisting Buildings an Integrated Development Approachan Integrated Development Approach
-- development of thedevelopment of the HPCHPC
-- problemsproblems to be resolved for sustainabilityto be resolved for sustainabilityproblemsproblems to be resolved for sustainabilityto be resolved for sustainability
44
-- solutionssolutions jointly developed with the industriesjointly developed with the industries
----
Part I
Concrete for Repairs in Existing BuildingsConcrete for Repairs in Existing Buildings ----Concrete for RepairsConcrete for RepairsConcrete for Repairs in Existing BuildingsConcrete for Repairs in Existing Buildings an Integrated Development Approachan Integrated Development Approach
Concrete for RepairsConcrete for Repairs
-- development of thedevelopment of the HPCHPC
55
…itit sttartts from our needsneeds…
HPCHPCHPCHPC High Performance ConcreteHigh Performance Concrete
66
t th
Our needs HPCOur needs HPCOur needs HPCOur needs HPC high
flow ability
compaction not needed
low long-term
shrinkage
our needs
strength achieved quickly drying
shrinkage crack free
good
high bond strength
77 low elastic modulus
g impermeabilit
y to water
our HPCour HPCour HPCour HPC major types using currently by Housing Department:major types using currently by Housing Department:
CC (f f )(f f )¾¾ HPCHPC –– F (for floor)F (for floor) ¾¾ HPCHPC –– C (for ceiling)C (for ceiling)( g)( g)
a kind of thea kind of the PMCPMC amongst the followingamongst the followinga kind of thea kind of the PMCPMC amongst theamongst followingthe following concrete using polymers:concrete using polymers:
Initial Setting Time < 40 minutes (HPC-F) Long Term Shrinkage at 28-day < 0.015%
Coutinho Ring Test No Cracks Bond Test at 7-day > 1 MPa Water Absorption < 2%
Modulus of Elasticity at 28-day < 25 Gpa Flow Test > 150 mm (HPC-C)
99
Flow Test 150 mm (HPC C) Maximum Chloride Content < 0.35%
t t
Hi h Adh i Mi i i R b d
Key Ingredients in the HPCKey Ingredients in the HPC hi h S ifi i R ihi h S ifi i R ito achieve the Specification Requirementsto achieve the Specification Requirements
Requirements Additives UsedAdditives UsedRequirements Additives UsedAdditives Used
Fast Initial Setting Time & 1.5 hr. Comp. Strength (for HPC-Early Strength Only) (1) Chloride Free Mineral Accelerator(1) Chloride Free Mineral Accelerator
Low Long Term Shrinkage (2) Mineral Shrinkage Reducing Agent(2) Mineral Shrinkage Reducing Agent
Crack Control (Coutinho Ring Test) (3) Micro(3) Micro--CelluloseCelluloseCrack Control (Coutinho Ring Test) (3) Micro(3) Micro CelluloseCellulose
High Bond Strength; Low Water Absorption & Elastic Modulus compatible
(for HPC-Early Strength Only) (5) Polycarboxylate High Range Water(5) Polycarboxylate High Range Water
Reducing AgentReducing Agent (6) R l i l Hi h D f Hi h(6) R l i l Hi h D f Hi h
1010
High Adhesion to Minimize Rebound Loss when Spray (for HPC-Spray Only)
(6) Relatively High Dosage of High(6) Relatively High Dosage of High Viscosity Cellulose EtherViscosity Cellulose Ether
for concrete for concrete
t tt t
Effects of Special Additives in HPCEffects of Special Additives in HPC--FF
(1)(1) Chloride Free Mineral AcceleratorChloride Free Mineral Accelerator:: ¾¾ Accelerate the hydration process of cement and thus ableAccelerate the hydration process of cement and thus able¾¾ Accelerate the hydration process of cement and thus ableAccelerate the hydration process of cement and thus able
to achieve the requiredto achieve the required early strengthearly strength
Possible Side Effect:Possible Side Effect: ¾¾ Fast workability loss (facilitate with mechanicalFast workability loss (facilitate with mechanical
equipment for concrete placing)equipment for concrete placing)equipment placing)equipment placing) ¾¾ Fast development of heat of hydration (not a problem forFast development of heat of hydration (not a problem for
thin section structures less than 500 mm)thin section structures less than 500 mm) ¾¾ I h ibilit f h i k ki ( dI h ibilit f h i k ki ( d¾¾ Increase the possibility of shrinkage cracking (preventedIncrease the possibility of shrinkage cracking (prevented
by adding Cellulose Ether)by adding Cellulose Ether)
1111
gg (( ))
))
⋅⋅
⋅⋅
⋅⋅ ⋅⋅ ⋅⋅
⋅⋅ ⋅⋅ ⋅⋅ ⋅⋅
⋅⋅ ⋅⋅⋅⋅ ⋅⋅
Mechanism of the Accelerator to develop theMechanism of the Accelerator to develop the early strengthearly strength of concreteof concreteearly strengthearly strength of concreteof concrete
¾¾ Main Ingredient: AlMain Ingredient: Al22(SO(SO44))3322 44 33
¾¾ Mechanism: It increases the SOMechanism: It increases the SO44 --22 content in the paste and reacts very fast withcontent in the paste and reacts very fast with
the Althe Al22OO33, CaO & CaSO, CaO & CaSO44 in Portland Cement to form Cin Portland Cement to form C33A (tricalciumA (tricalcium aluminate: 3CaO.Alaluminate: 3CaO.Al22OO33)) 22 33
¾¾ The CThe C33A content helps increasing the early strength of concrete (also evolvesA content helps increasing the early strength of concrete (also evolves heat during hydration)heat during hydration)
1212
CC33S (tricalcium silicate 3CaOS (tricalcium silicate 3CaO SiOSiO22), C), C22S (Dicalcium Silicate 2CaOS (Dicalcium Silicate 2CaO SiOSiO22) & C) & C44AFAF Tetracalcium aluminoferrite 4CaOTetracalcium aluminoferrite 4CaO AlAl22OO33 FeFe22OO33 contribute concrete strength at a latercontribute concrete strength at a later stage.stage.
Effects of Special Additives in the HPCEffects of Special Additives in the HPC
(2)(2) Mineral Shrinkage Reducing AgentMineral Shrinkage Reducing Agent:: ¾¾ reduce long term dryingreduce long term drying shrinkageshrinkage byby ettringiteettringite¾¾ reduce long term dryingreduce long term drying shrinkageshrinkage byby ettringiteettringite
formation that, other than itsformation that, other than its slight expansion propertiesslight expansion properties in cement paste, grows into gel voids of hardenedin cement paste, grows into gel voids of hardened cement paste and reduce the hardeningcement paste and reduce the hardening shrinkageshrinkage andandcement paste and reduce the hardeningcement paste and reduce the hardening shrinkageshrinkage andand dryingdrying shrinkageshrinkage..
¾¾ reduce heat of hydrationreduce heat of hydration
Possible Side Effect:Possible Side Effect: ¾¾ Prolonged setting time (compensated by adjustingProlonged setting time (compensated by adjusting¾¾ Prolonged setting time (compensated by adjustingProlonged setting time (compensated by adjusting
dosage of the Mineral Accelerator)dosage of the Mineral Accelerator)
¾¾ consisting mainly of three minerals:consisting mainly of three minerals: zz Hauyne: 3CaOHauyne: 3CaO ⋅⋅ 3Al3Al22OO33 CaSOCaSO4422 33 44
zz Free lime: CaOFree lime: CaO zz Free Gypsum: CaFree Gypsum: Ca SOSO44
¾¾ h d i f h i l d ih d i f h i l d i tt i ittt i it¾¾ hydration of these minerals producinghydration of these minerals producing ettringiteettringite (3CaO(3CaO AlAl22OO33 3CaSO3CaSO44 ⋅⋅ 32H32H22O) thatO) that zz is a very small crystal of several microns.is a very small crystal of several microns.zz is a very small crystal of several microns.is a very small crystal of several microns. zz grows into the voids of cement paste gels and reduces hardening shrinkagegrows into the voids of cement paste gels and reduces hardening shrinkage
of the gel and drying shrinkage.of the gel and drying shrinkage. zz has expansion properties in its hydration process (at early stage) andhas expansion properties in its hydration process (at early stage) and
1515
p p ope y p ( y ge)p p ope y p ( y ge) compensates also shrinkage in the HPC.compensates also shrinkage in the HPC.
H O
Reactions leading toReactions leading to ettringiteettringite formationformation by the Shrinkage Reducing Agent in the HPCby the Shrinkage Reducing Agent in the HPC
CaSO4
H2Oagen
t
CaO
2
Ca(OH)2
duci
ng a
H2O
3CaO·3A12O3 · [3CaO･Al2O3･CaSO4･ 3CaO･Al2O3･
nkag
e re
d
CaSO4 H2O 12H2O-2{3CaO･Al2O3･
Ca(OH)2･12H2O}]
3CaSO4･32H2O
Ettringiteshrin
1616
se ese e oo
C ll l E hC ll l E h f h HPCf h HPC F ll d d )F ll d d )
Effects of Special Additives in the HPCEffects of Special Additives in the HPC
(3)(3) MicroMicro--CelluloseCellulose:: ¾¾ increasingincreasing water retentionwater retention for hydration of the HPCfor hydration of the HPC¾¾ increasingincreasing water retentionwater retention for hydration of the HPC,for hydration of the HPC, ¾¾ reducing bleeding, segregation andreducing bleeding, segregation and plastic shrinkageplastic shrinkage ¾¾ modifying themodifying the viscosityviscosity (a relatively high dosage of high(a relatively high dosage of high
iscositiscosit Cell lose EtherCell lose Ether d in th HPCd in th HPC C tC t red ce rebo ndred ce rebo nd))
Possible Side Effect:Possible Side Effect: ¾¾ p the HPC
viscosityviscosity Cellulose EtherCellulose Ether usedu in the HPCsed in the HPC--C toC to reduce reboundreduce rebound))
rolonged setting time (forprolonged setting time (for the HPC--F: compensating byF: compensating byadjusting dosage of the mineral accelerator; for the HPCadjusting dosage of the mineral accelerator; for the HPC--C:C: allowing more time for finishing)allowing more time for finishing)
¾¾ slight air entrainment (controlling the dosage to preventslight air entrainment (controlling the dosage to preventexcessive air entrainment)excessive air entrainment)
¾¾ affecting flowability (for the HPCaffecting flowability (for the HPC--F: using a low viscosityF: using a low viscosity
1717
Cellulose EtherCellulose Ether; f; or the HPCfor the HPC--F: a controlled dosage)F: a controlled dosage)
Polymer Chain of Micro-Cellulose in HPC
H CH2OROR
OO
H
H
O
H
OO
H
O H HH
O
CH2OR OROR
xx R: H or CH3
The viscosity of the paste in concrete induced by the micro-cellulose and the van
1818
The viscosity of the paste in concrete induced by the micro cellulose and the van der Waals force of its long polymer chain exerted to the water ions restrict the water molecules from escaping from the concrete easily.
:
t
Effects of Special Additives in the HPC
(4) Redispersible Emulsion Powder:(4) Redispersible Emulsion Powder enhance adhesive strength to existing concrete reduce water absorption of the HPCp increase flexibility of the HPC to achieve an elastic modulus compatible to existing old concrete
P ibl Sid EffPossible Side Effect: prolonged setting time (compensated by adjusting dosage of the mineral accelerator)
1919
adjusting dosage of the mineral accelerator)
Polymer Chain of Redispersible Emulsion Powder Ethylene Vi l hl id Vinyl laurate
H H H H H H
Ethylene Vinyl chloride Vinyl laurate
H
C C C C C C
H H H OCl m n
C
CH H
O m n
C
C
H H
H HContributes
Contributes
H x Contributes flexibility
water resistance
2020
Contributes water
resistance
C ll l E h )C ll l E h )
Effects of Special Additives in HPC-F
(5) Polycarboxylate High Range Water Reducing Agent:Agent: largely reducing the mixing water required and loweringlargely reducing the mixing water required and lowering the W/C ratiothe W/C ratio providing high flowability for the HPCproviding high flowability for the HPC
Possible Side Effect: increased bleeding (compensated by addition of theincreased bleeding (compensated by addition of the Cellulose Ether)Cellulose Ether) prolonged workability retention and stiffening time of theprolonged workability retention and stiffening time of the HPC (compensated by the Mineral Accelerator)HPC (compensated by the Mineral Accelerator)
2121
HPC (compensated by the Mineral Accelerator)HPC (compensated by the Mineral Accelerator)
Polymer Structure of Polycarboxylate Admixture
known as the 3rd generation superplasticizer consisting of backbone based on poly-carboxylic salts or ether with grafted side chains of Ethylene Oxide (EO) and Propylene Oxide (PO). usually called EOPO copolymer, also called comb co-polymer
Polycarboxylate High Range Water Reducing Agent in the HPCPolycarboxylate High Range Water Reducing Agent in the HPC
2. … and expelling each other
( p g y charged) copolymer adhering to cement particles …
each other …
cement
cement w
w
cementw
2323 3. … releasing water molecules
trapped … enhancing workability
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Part IIPart IIaa
Concrete for Repairs in Existing BuildingsConcrete for Repairs in Existing Buildings ----Existing BuildingsExisting BuildingsConcrete for Repairs in Existing BuildingsConcrete for Repairs in Existing Buildingsan Integrated Development Approachan Integrated Development Approach
Existing BuildingsExisting Buildings
-- problemsproblems to be resolved for sustainabilityto be resolved for sustainabilityproblemsproblems to be resolved for sustainabilityto be resolved for sustainability
In the following two parts are two examples of the problems dealing with by using the HPC:
trafficabletrafficable waterproofingwaterproofing spallingspalling toto
be repairedbe repairedhigh performancehigh performance concrete (concrete (HPCHPC))
HPCHPC max. 80 mmmax. 80 mm
floor
(( ))
max. 50 mm thickmax. 50 mm thick HPCHPC thick locallythick locally
concrete slab steel bar
existingexisting concrete slabconcrete slab
steel bar
3434 spalled concrete to bespalled concrete to be removed & repairedremoved & repaired
spalling being repairedspalling being repaired
3535
EMAC & District Member ConsensusEMAC & District Member ConsensusEMAC & District Member ConsensusEMAC & District Member Consensus
---- Concrete for Repairs in Existing BuildingsConcrete for Repairs in Existing Buildings ----Concrete for Repairs in Existing BuildingsConcrete for Repairs in Existing Buildings an Integrated Development Approachan Integrated Development Approachan Integrated Development Approachan Integrated Development Approach
3636
-- solutionssolutions jointly developed with the industriesjointly developed with the industries
Measure #Measure #22Measure #Measure #22
3737
measure #measure #22 … a measure after completion… a measure after completion
f th #f th #11 ( i d ll)( i d ll)of the measure #of the measure #11 (windows on wall) …(windows on wall) …
3838previous situation after raining
High Performance ConcreteHigh Performance Concrete (HPC)(HPC)(HPC)(HPC)
¾¾ a prea pre--packed proprietary HPCpacked proprietary HPC ¾¾ for repair and patch up works like floors, toilet infill andfor repair and patch up works like floors, toilet infill and
similar applications for old buildingssimilar applications for old buildings ¾¾ allows early foot traffic after applicationallows early foot traffic after application ¾¾ high early strength within an hour of time … fasthigh early strength within an hour of time … fast
application early opening to public allowing foot trafficapplication early opening to public allowing foot trafficapplication … early opening to public allowing foot trafficapplication … early opening to public allowing foot traffic ¾¾ flowable consistency for efficient placingflowable consistency for efficient placing
¾¾ premixed in factorypremixed in factory ¾¾ easy handling and storageeasy handling and storage ¾¾ high flowabilityhigh flowability ¾¾ high workabilityhigh workability ¾¾ fast settingfast setting¾¾ fast settingfast setting ¾¾ high early strengthhigh early strength ¾¾ extremely low shrinkageextremely low shrinkage ¾¾ extremely l absorptionextremely l absorption
…. Specifications
¾¾ extremely low water absorptionextremely low water absorption ¾¾ high adhesion strengthhigh adhesion strength ¾¾ similar elastic modulus with old concretesimilar elastic modulus with old concrete
4242
p yp y
Fast SetFast Set
HPCHPCHPCHPC High Flow AbilityHigh Flow Ability
Low Water AbsorptionLow Water Absorption Compatible Modulus of ElasticityCompatible Modulus of Elasticity contradictorycontradictory
•• the initialthe initial--set from 40 to 60 minutesset from 40 to 60 minutes
6363
•• the initialthe initial set from 40 to 60 minutesset from 40 to 60 minutes
•• the 5 MPa strength development from 1 hr. to 1.5 hr.the 5 MPa strength development from 1 hr. to 1.5 hr.
finally a new HPC was bornfinally a new HPC was bornfinally ... a new HPC was bornfinally ... a new HPC was born
t ith it h t i ti d itt ith it h t i ti d it 6464
to cope with its characteristics and siteto cope with its characteristics and site constraints, we developed …constraints, we developed …
… mechanical device for multi uses in many… mechanical device for multi uses in many such similar bays and public areas …such similar bays and public areas …
6565
e t oduced a ot e ee t oduced a ot e e
… we introduced another mixer …… we introduced another mixer …
for Choi Hungfor Choi Hung empty baysempty bays
in lieu of the mixer tried initiallyin lieu of the mixer tried initially
6666
controllerscontrollersmixer adopted for Empty Bays inmixer adopted for Empty Bays in controllerscontrollersChoi Hung EstateChoi Hung Estate
Needle Valve Mixing
Water to Mixing Tube
Mixing Tube
Water Flow Meter
Water Inlet
6767Electric Valve Water Pressure
Gauge Pressure ReducerHPC
Outlet
6868
material mixing proportionmaterial mixing proportion l &l &controls & testscontrols & tests
saw blade
mixing & concretingmixing & concretingmixing & concretingmixing & concreting onon--site actual trialsite actual trial
6969
mechanized sweepingmechanized sweepingmechanized sweepingmechanized sweeping onon--site actual trialsite actual trial
7070
level sweeping nearly finishedlevel sweeping nearly finishedlevel sweeping nearly finishedlevel sweeping nearly finished onon--site actual trialsite actual trial
well received with appreciationwell received with appreciation l & f ll d b ‘fi ’ h bl & f ll d b ‘fi ’ h bclaps & followed by ‘first’ thumbsclaps & followed by ‘first’ thumbs
7777
----
Part IIPart IIaa
Concrete for Repairs in Existing BuildingsConcrete for Repairs in Existing Buildings ----Existing BuildingsExisting BuildingsConcrete for Repairs in Existing BuildingsConcrete for Repairs in Existing Buildingsan Integrated Development Approachan Integrated Development Approach
Existing BuildingsExisting Buildings
-- problemsproblems to be resolved for sustainabilityto be resolved for sustainabilityproblemsproblems to be resolved for sustainabilityto be resolved for sustainability
In the following two parts are two examples of the problems dealing with by using the HPC:
T tal eplacement f lab bottom b ndT tal eplacement f lab bottom b nd�� Total replacement of slab bottom bars andTotal replacement of slab bottom bars and lower zone concretelower zone concrete Nuisance mitigationNuisance mitigation�� Nuisance mitigationNuisance mitigation
�� High performance sprayed concreteHigh performance sprayed concrete -- Low water permeabilityLow water permeability -- Compatible with old concreteCompatible with old concrete -- SustainableSustainable
8383
-- High workability and low reboundHigh workability and low rebound
Integrated Development Process
Housing Authority
Development ofDevelopment of Slab SemiSlab Semi-recastingrecastingConcrete
Supplier
Tenants of Public Housing
Cutting &Spraying
Specialists
8484
Specialists
b d lb d l
SawSaw--cutting and chipping forcutting and chipping for 3600
rebar and concrete removalrebar and concrete removal
2000
Slab to be semiSlab to be semi-recastrecast
100
mm
�� Risk of overRisk of over--breakingbreaking Concrete and bottomConcrete and bottom bars to be removedbars to be removed
1
�� Noise and vibration nuisancesNoise and vibration nuisances bars to be removedbars to be removed
Solution:Solution:
SawSaw--cutting + chipping to form orthogonal grooves for :cutting + chipping to form orthogonal grooves for :-�� Removal existing concrete and rebarsRemoval existing concrete and rebars
8585
�� Laying of new galvanized rebarsLaying of new galvanized rebars
Groove Cutting ExperienceGroove Cutting Experienceg pg p
Mounting problem;Mounting problem;
33--phase electricityphase electricity
600mm Hydraulic Saw-cutter
Grooves toGrooves to House newHouse new rebarsrebars y
The new method removes my worries of requiring me to move out
9393
Thank YouThank YouThank YouThank You
9494
th t t l b hi dth t t l b hi d
The American The American Concrete Concrete InstitutInstitute e (ACI): defines the HPC (ACI): defines the HPC asas concrete meetingconcrete meeting special combinations of special combinations of performance performance andand
ifif itit ii ttununififormormitity requy requiiremenrementtss ththaatt canno cannott a allways ways bbe ace achihieveevedd routinely routinely when using when using conventional constituents conventional constituents and and normalnormal mixing, placing mixing, placing and curing practices.and curing practices.
Related commentary Related commentary states: states: a HPC a HPC is one in which is one in which certaincertain characteristics characteristics are developed are developed for for a particular application a particular application andand environment. E.g. of characteristics are:environment. E.g. of characteristics are: ¾¾EaseEase ofof placementplacement¾¾EaseEase ofof placementplacement ¾¾Compaction without segregationCompaction without segregation ¾¾Early age strengthEarly age strength ¾¾LongLong--termterm mechanicalmechanical ppropertiesroperties¾¾LongLong termterm mechanicalmechanical propertiesproperties ¾¾PermeabilityPermeability ¾¾DensityDensity ¾¾Heat of hHeat of hyydrationdrationyy ¾¾TToughnessoughness ¾¾VVoolume stabilitylume stability ¾¾Long life in severe environmentsLong life in severe environments
