Date post: | 02-Jan-2016 |
Category: |
Documents |
Upload: | shawn-pearson |
View: | 237 times |
Download: | 15 times |
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
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
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