2. One Definition of Portland Cement Concrete…One Definition of Portland Cement Concrete…
Portland cement concrete (PCC) is a heterogeneous system ofPortland cement concrete (PCC) is a heterogeneous system of
solid, discrete, gradiently sized, inorganic mineral aggregates,solid, discrete, gradiently sized, inorganic mineral aggregates,
usually plutonic or sedimentary-calcareous in origin, embeddedusually plutonic or sedimentary-calcareous in origin, embedded
in a matrix compounded of synthesized polybasic alkaline andin a matrix compounded of synthesized polybasic alkaline and
alkaloidal silicates held in aqueous solution and co-precipitatealkaloidal silicates held in aqueous solution and co-precipitate
dispersion with other amphoteric oxides, this matrix beingdispersion with other amphoteric oxides, this matrix being
originally capable of progressive dissolution, hydration, re-originally capable of progressive dissolution, hydration, re-
precipitation, gelation and solidification through a continuousprecipitation, gelation and solidification through a continuous
and co-existent series of crystalline, amorphous, colloidal andand co-existent series of crystalline, amorphous, colloidal and
cryptocrystalline states and ultimately subject to thermo-cryptocrystalline states and ultimately subject to thermo-
allotriomorphic alteration, the system when first conjoined beingallotriomorphic alteration, the system when first conjoined being
plastic during which stage it is impressed to a predeterminedplastic during which stage it is impressed to a predetermined
form into which it finally consolidates, thus providing a structureform into which it finally consolidates, thus providing a structure
relatively impermeable and with useful capacity to transmitrelatively impermeable and with useful capacity to transmit
tensile, compressive, and shear stresses.tensile, compressive, and shear stresses.
(source unknown)(source unknown)
3. A Real Definition of PCC…A Real Definition of PCC…
A mixture of:A mixture of:
Portland CementPortland Cement
Fine AggregateFine Aggregate
Coarse AggregateCoarse Aggregate
WaterWater
AirAir
Cement and waterCement and water
combine, changing from acombine, changing from a
moist, plastic consistencymoist, plastic consistency
to a strong, durable rock-to a strong, durable rock-
like construction materiallike construction material
by means of a chemicalby means of a chemical
reaction called “hydration”reaction called “hydration”
4. Further Defined…Further Defined…
Concrete exists in threeConcrete exists in three
statesstates
PlasticPlastic
CuringCuring
HardenedHardened
5. Mix DesignMix Design
Combination of materials to provide the mostCombination of materials to provide the most
economical mixture to meet the performanceeconomical mixture to meet the performance
characteristics suitable for the applicationcharacteristics suitable for the application
Developed in laboratory - produced in a batchDeveloped in laboratory - produced in a batch
plantplant
Mix proportions will typically vary over a rangeMix proportions will typically vary over a range
for a given jobfor a given job
Required strength and exposure conditionsRequired strength and exposure conditions
Mix consistency must be ensured to guaranteeMix consistency must be ensured to guarantee
concrete performanceconcrete performance
6. Mixture Design ConceptsMixture Design Concepts
Cement contentCement content
Sacks/ydSacks/yd33
or lbs/ydor lbs/yd33
To a point, increasing cement contentTo a point, increasing cement content
increases strength and durabilityincreases strength and durability
Too much cement is uneconomical andToo much cement is uneconomical and
potentially detrimentalpotentially detrimental
Amount of waterAmount of water
Proper selection of aggregate and gradingProper selection of aggregate and grading
Admixtures?Admixtures?
7.
8. Water-to-Cement RatioWater-to-Cement Ratio
The ratio of water-to-cement, orThe ratio of water-to-cement, or w/cw/c, is the single, is the single
most important parameter with regards to concretemost important parameter with regards to concrete
qualityquality
Theoretically, about 0.22 to 0.25 is required forTheoretically, about 0.22 to 0.25 is required for
complete hydrationcomplete hydration
Practically, the useful limit is around 0.33Practically, the useful limit is around 0.33
Reducing the water for a given amount of cementReducing the water for a given amount of cement
will move the cement particles closer together,will move the cement particles closer together,
which in turn densifies the hydrated cement pastewhich in turn densifies the hydrated cement paste
This increases strength and reduces permeabilityThis increases strength and reduces permeability
It also makes the concrete more difficult to workIt also makes the concrete more difficult to work
In combination, theIn combination, the w/cw/c and degree of hydrationand degree of hydration
control many of the properties of the hardenedcontrol many of the properties of the hardened
concreteconcrete
9.
10. Voids in Hydrated CementVoids in Hydrated Cement
Concrete strength, durability, and volumeConcrete strength, durability, and volume
stability is greatly influenced by voids instability is greatly influenced by voids in
the hydrated cement pastethe hydrated cement paste
Two types of voids are formed in hydratedTwo types of voids are formed in hydrated
cement pastecement paste
Gel poresGel pores
Capillary poresCapillary pores
Concrete also commonly containsConcrete also commonly contains
entrained air and entrapped airentrained air and entrapped air
11. Voids in Hydrated CementVoids in Hydrated Cement
PastePaste
Gel PoresGel Pores
Space between layers in C-S-H with thicknessSpace between layers in C-S-H with thickness
between 0.5 and 2.5 nmbetween 0.5 and 2.5 nm
Includes interlayer spaces, micropores, and smallIncludes interlayer spaces, micropores, and small
isolated capillary poresisolated capillary pores
Can contribute 28% of paste porosityCan contribute 28% of paste porosity
Little impact on strength and permeabilityLittle impact on strength and permeability
Can influence shrinkage and creepCan influence shrinkage and creep
12. Voids in Hydrated Cement PasteVoids in Hydrated Cement Paste
Capillary VoidsCapillary Voids
Depend on initial separation of cementDepend on initial separation of cement
particles, which is controlled by theparticles, which is controlled by the w/cw/c
It is estimated that 1 cmIt is estimated that 1 cm33
of anhydrous portland cementof anhydrous portland cement
requires 2 cmrequires 2 cm33
of space to accommodate the hydrationof space to accommodate the hydration
productsproducts
Space not taken up by cement or hydration products isSpace not taken up by cement or hydration products is
capillary porositycapillary porosity
On the order of 10 to 50 nm, although largerOn the order of 10 to 50 nm, although larger
for higherfor higher w/cw/c (3 to 5 mm)(3 to 5 mm)
Larger voids affect strength and permeability,Larger voids affect strength and permeability,
whereas smaller voids impact shrinkagewhereas smaller voids impact shrinkage
21. Dimensional Range of SolidsDimensional Range of Solids
and Voids in Hydrated Cementand Voids in Hydrated Cement
PastePaste
Source: Mehta and Monteiro, 1993
25. Interfacial Transition ZoneInterfacial Transition Zone
Zone between the aggregate and bulk pasteZone between the aggregate and bulk paste
Has a major impact on the strength and permeability of theHas a major impact on the strength and permeability of the
concreteconcrete
The interfacial zone is 10 to 50 mm in thicknessThe interfacial zone is 10 to 50 mm in thickness
Generally weaker than either the paste or aggregate due toGenerally weaker than either the paste or aggregate due to
locally highlocally high w/cw/c and the “wall effect” (packing problems) – inand the “wall effect” (packing problems) – in
some cases predominately large crystals of calcium hydroxidesome cases predominately large crystals of calcium hydroxide
and ettringite are oriented perpendicular to aggregate surfaceand ettringite are oriented perpendicular to aggregate surface
Greater porosity and few unhydrated cement grainsGreater porosity and few unhydrated cement grains
Microcracking commonly exists in transition zoneMicrocracking commonly exists in transition zone
Results in shear-bond failure and interconnectedResults in shear-bond failure and interconnected
macroporosity, which influences permeabilitymacroporosity, which influences permeability
Modification of transition zone is key to improving concreteModification of transition zone is key to improving concrete
26.
27.
28. Entrained AirEntrained Air
Provides the path forProvides the path for
water to migrate fromwater to migrate from
larger voids to smallerlarger voids to smaller
voidsvoids
Water in smallestWater in smallest
capillary/gel porescapillary/gel pores
won’t freezewon’t freeze
For adequateFor adequate
protectionprotection
6-8% air by volume6-8% air by volume
Entrained air spacingEntrained air spacing
factor = 0.2mmfactor = 0.2mm
29. Entrained Air MeasurementEntrained Air Measurement
Proper air entrainment is one ofProper air entrainment is one of
the most critical aspects ofthe most critical aspects of
producing durable concreteproducing durable concrete
Air entrainment affectsAir entrainment affects
StrengthStrength
Freeze-Thaw durabilityFreeze-Thaw durability
PermeabilityPermeability
Scaling ResistanceScaling Resistance
WorkabilityWorkability
Air content must be measuredAir content must be measured
accurately at the job siteaccurately at the job site
31. Curing ConcreteCuring Concrete
Extremely importantExtremely important
Concrete will not achieve its potential strengthConcrete will not achieve its potential strength
unless it is properly curedunless it is properly cured
Concrete will crack if not properly curedConcrete will crack if not properly cured
Curing should be started immediately afterCuring should be started immediately after
final setfinal set
Curing includes providing both moistureCuring includes providing both moisture
and temperatureand temperature
32.
33. CuringCuring
Concrete must not dry out, especially at aConcrete must not dry out, especially at a
young ageyoung age
Preferably water is applied after the concretePreferably water is applied after the concrete
has sethas set
Steam curing applies both heat andSteam curing applies both heat and
moisture, accelerating hydrationmoisture, accelerating hydration
Often, waterproof barriers are used to holdOften, waterproof barriers are used to hold
mix water in…not as good as wet curingmix water in…not as good as wet curing
34.
35.
36.
37.
38.
39. DurabilityDurability
Concrete is inherently durable, having aConcrete is inherently durable, having a
history of exceptional long-term performancehistory of exceptional long-term performance
In some instances, the structure’s service lifeIn some instances, the structure’s service life
has been adversely affected by the concrete’shas been adversely affected by the concrete’s
inability to maintain its integrity in theinability to maintain its integrity in the
environment in which it was placedenvironment in which it was placed
These distress manifestations areThese distress manifestations are
categorized as materials-related distresscategorized as materials-related distress
(MRD)(MRD)
40. What is Materials-RelatedWhat is Materials-Related
Distress?Distress?
MRD is commonly associated with theMRD is commonly associated with the
“durability” of the concrete“durability” of the concrete
Durability is not an intrinsic material propertyDurability is not an intrinsic material property
““Durability” cannot be measuredDurability” cannot be measured
Concrete that is durable in one application mayConcrete that is durable in one application may
rapidly deteriorate if placed in another applicationrapidly deteriorate if placed in another application
It is not related to loading, although loading canIt is not related to loading, although loading can
exacerbate the distressexacerbate the distress
41. Common Types of MRDCommon Types of MRD
Physical MechanismsPhysical Mechanisms
Freeze-thaw Deterioration of Hardened CementFreeze-thaw Deterioration of Hardened Cement
PastePaste
Deicer Scaling/DeteriorationDeicer Scaling/Deterioration
Freeze-Thaw Deterioration of AggregateFreeze-Thaw Deterioration of Aggregate
Chemical MechanismsChemical Mechanisms
Alkali-Aggregate ReactivityAlkali-Aggregate Reactivity
Alkali-Silica and Alkali-Carbonate ReactivityAlkali-Silica and Alkali-Carbonate Reactivity
Sulfate AttackSulfate Attack
External and Internal Sulfate AttackExternal and Internal Sulfate Attack
Corrosion of Embedded SteelCorrosion of Embedded Steel
42.
43.
44.
45. Important ConsiderationsImportant Considerations
The concrete constituents, proportions,The concrete constituents, proportions,
and construction all influence MRDand construction all influence MRD
Water is needed for deleterious expansionWater is needed for deleterious expansion
to occurto occur
Severe environments (e.g. freezing andSevere environments (e.g. freezing and
thawing, deicer applications, high sulfatethawing, deicer applications, high sulfate
soils, etc.) make it worsesoils, etc.) make it worse
Strength does not equal durabilityStrength does not equal durability
46. SummarySummary
Concrete is an immensely complex material thatConcrete is an immensely complex material that
will perform to its potential only if treatedwill perform to its potential only if treated
properly during the entire construction phaseproperly during the entire construction phase
Mix design and proportioningMix design and proportioning
TransportingTransporting
Placing and consolidatingPlacing and consolidating
Finishing and curingFinishing and curing
As billions are spent annually on concreteAs billions are spent annually on concrete
construction, the most sophisticated testing isconstruction, the most sophisticated testing is
used to ensure qualityused to ensure quality
47. ASTM C 143-00 Standard Test Method for SlumpASTM C 143-00 Standard Test Method for Slump
of Hydraulic Cement Concreteof Hydraulic Cement Concrete