Classification Features in Influencing Concrete Fine Aggregate-Sand Coarse Aggregate-Gravel 4.2.2 Aggregate.

ClassificationClassificationFeatures in Influencing ConcreteFeatures in Influencing ConcreteFine Aggregate-SandFine Aggregate-SandCoarse Aggregate-GravelCoarse Aggregate-Gravel

4.2.2 Aggregate4.2.2 Aggregate

Coarse Aggregate

DefinitionClassificationRequirements of Aggregate

ImpuritiesParticle Shape and Surface TextureParticle Size GradationType of Particle Size GradationMaximum SizeAggregate Strength

It refers to the aggregate larger than 5mm

Must be in agreement with GB/T14685-2001(JGJ53-92)

AggregateAggregate PrimaryPrimaryPrimaryPrimary

GravelGravel

ScreeScree

According to shape of primary coarsAccording to shape of primary coarse aggregate, it can be divided into grave aggregate, it can be divided into gravel and scree. el and scree. Gravel is the widely used primary coGravel is the widely used primary coarse aggregate.arse aggregate.

ClassificationClassification

ⅠⅠ: I: In the concrete the strn the concrete the strength grade is more than C60ength grade is more than C60 ；；

Ⅱ Ⅱ : I: In the concrete the stren the concrete the strength grade is ngth grade is between C30-between C30-CC6060;;

AggregateAggregate Technical requirementTechnical requirementTechnical requirementTechnical requirement

ⅢⅢⅢⅢ

ⅡⅡⅡⅡ

ⅠⅠⅠⅠ

Ⅲ Ⅲ : : IIn the concrete thn the concrete the strength grade is e strength grade is lessless than Cthan C30.30.

By quality, there are three types: , ⅠBy quality, there are three types: , Ⅰand Ⅱ Ⅲand Ⅱ Ⅲ

ClassificationClassification

ImpuritiesParticle Shape and Surface TextureParticle Size GradationType of Particle Size GradationMaximum SizeAggregate Strength

Clay contentClay content , clod , clod content, and the content, and the content of content of needle shaneedle shapepe particles and particles and slice slice shape shape particles particles must must be in agreement with be in agreement with GB/T14685-2001(JGGB/T14685-2001(JGJ52-92).J52-92).

ImpuritiesImpuritiesImpuritiesImpurities

Limits of type and contentLimits of type and contentLimits of type and contentLimits of type and content

Fig4.2.1Needle and Slice Shape Particles

Details will be introduced later in durability of concrete.

If there is potential danger, the alkali content should be less than 0.6%.

A special test is needed when we used the admixture containing potassium and sodium.

Alkali-aggregate ReactionAlkali-aggregate ReactionAlkali-aggregate ReactionAlkali-aggregate Reaction

The particle shape and surface texture are the same with that of the sand.

Particle Shape and Surface TextureParticle Shape and Surface TextureParticle Shape and Surface TextureParticle Shape and Surface Texture

Particle Size GradationParticle Size GradationParticle Size GradationParticle Size Gradation

The parameter is the same with the sand in the test method of gradation and the calculation.

Only differs in the size of sieve pore and the requirements of gradation.

SStandard screen siztandard screen size: e:

2.52.5 、、 5.05.0 、、 1010 、、 1166 、、 2020 、、 2525 、、 31.531.5 、、4040 、、 5050 、、 6363 、、 80 80 、、100 and so on.100 and so on.

Particle Size GradationParticle Size GradationParticle Size GradationParticle Size Gradation

Fig.4.2.2 Screen Instrument

Type of Particle Size GradationType of Particle Size Gradation

Particle Size Particle Size

GradationGradation

Particle Size Particle Size

GradationGradation

Sequent GradingSequent GradingSequent GradingSequent Grading

Discontinuous GradationDiscontinuous Gradation

Single GradationSingle Gradation

There are three types of particle size gradation sequent There are three types of particle size gradation sequent grading, discontinuous gradation and single gradation.grading, discontinuous gradation and single gradation.

Sequent GradationSequent Gradation Every gradation of gravel accounts for a certain

proportion from the small to the big so that the workability is excellent and it is not easy to form layers.

Discontinuous GradationDiscontinuous Gradation Rid some particles of some gradation to reduc

e porosity; separate out easily so that high strength concrete or dry concrete can be produced with pounding.

Single GradationSingle Gradation It is used to form sequent gradation or mix with

coarse aggregate in continuous gradation, but the porosity is bigger and easier to be separated out when alone.

Maximum Size: Maximum size refers to the upper line of

nominal gradation of gravel. For example:5～ 20 is a range of nominal

gradation, 20mm is the upper line of nominal gradation.

5～ 20

limit of nominal gradation

Upper limit of nominal gradation

Maximum SizeMaximum Size

Maximum

Size

Economy

Quantities

of cement

Specific

Surface

area

• Maximum Size (DMaximum Size (Dmaxmax) can be decided according to the ) can be decided according to the

economy, Structure Limit and Constructioneconomy, Structure Limit and Construction

Ⅰ. Economy Larger the D D maxmax, smaller the specific surfa, smaller the specific surfa

ce, Less the quantities, higher the economyce, Less the quantities, higher the economy

Maximum SizeMaximum Size

ⅡⅡ. Structure Limit. Structure Limit

≯$≯$1/4 minimum size of section1/4 minimum size of section ≯$≯$1/4 minimum size of section1/4 minimum size of section

≯$≯$3/4minimum clear distance of bar3/4minimum clear distance of bar≯$≯$3/4minimum clear distance of bar3/4minimum clear distance of bar

=1/2 thickness of solid floor and ≯$50mm=1/2 thickness of solid floor and ≯$50mm=1/2 thickness of solid floor and ≯$50mm=1/2 thickness of solid floor and ≯$50mm

According to structure standard, the Dmax shoulAccording to structure standard, the Dmax should meet the following requirements:d meet the following requirements:

Dmax ≯91/4 minimum size of section Dmax ≯91/4 minimum size of section

Dmax ≯93/4minimum clear distance of barDmax ≯93/4minimum clear distance of bar

Dmax =1/2 thickness of solid floor and ≯950mmDmax =1/2 thickness of solid floor and ≯950mm

Maximum SizeMaximum Size

ⅢⅢ. . ConstructionConstruction

Dmax must meet the requirements of the construction.

Segregation, breakage of vane, walling up the tube of pump and vibration are easily produced in the process of mixing, transporting and vibrating, if maximum size is too large.

Maximum SizeMaximum Size

There are two methods to measure the strength of the aggregate strength: cubic strength of rock and crushing index of gravel.

Cubic strength of rock

The compressive strength of the cube is measured in saturated water.

Aggregate StrengthAggregate StrengthAggregate StrengthAggregate Strength

5cm×5cm×55cm×5cmcm×5cm

Fig4.2.3 Sketch map to measure cubic strength

Cubic strength of rock

For ordinary concrete: Aggregate strength ≮>1.

5 fcu

For HSC:Aggregate strength ≮>2.0 fcu

Also select the strength of rock according to the rocks types (list in Tab)

Aggregate StrengthAggregate StrengthAggregate StrengthAggregate Strength

RocksRocks StrengthStrength

Igneous Igneous rockrock

≮9≮980 MPa80 MPa

MetamorpMetamorphic rockhic rock

≮9≮960 MPa60 MPa

Aqueous Aqueous rockrock

≮9≮930 MPa30 MPa

Tab4.2.6 Tab4.2.6 Aggregate Strength ofAggregate Strength of different types different types

Method: Put the gravel with the

diameter of 10-20mm into the standard cylinder three times ,press them to 200kN and sift them in 2.5mm sieve.

Crushing index =

m0—mass of dry gravel before crushing

m1—mass of dry gravel after crushing and sifting

PressPress

SifeSife

Aggregate StrengthAggregate StrengthAggregate StrengthAggregate Strength

0

10

m

mm

Crushing Index of GravelCrushing Index of Gravel

Fig.4.2.4 Sketch map to measure Crushing IndexCrushing Index

石子压碎指标试验录像

Crushing IndexCrushing Index

Types of rockConcrete strength

gradeGravel crushing index（%）

Aqueous rockC55～ C40

≤C35≤10≤16

Metamorphic rock or plutonic igneous

rock

C55～ C40≤C35

≤12≤20

Igneous rockC55～ C40

≤C35≤13≤30

Tab.4.2.7 Crushing Index of GravelCrushing Index of Gravel of different of different types

Crushing index of gravel or Crushing index of gravel or sscree are listed in Tab4.2.cree are listed in Tab4.2.7 and Tab4.2.87 and Tab4.2.8

TabTab..4.2.8 4.2.8 Crushing Index of Scree Crushing Index of Scree (GB/T14685-2001)

Concrete strength grade

C55-C40 ≤C35

Crushing index (%)

≤12 ≤16

Crushing IndexCrushing Index

What kind of methods should be used

What kind of methods should be used Cubic strength of rock Crushing Index of Gravel

Cubic strength of rock is used for strength of high strength concrete.

Cubic strength of rock should be accorded with when it’s disputable between the two methods.