Download - CE 251 Lecture 4A
-
8/10/2019 CE 251 Lecture 4A
1/15
1
Dr Rajib ChowdhuryDepartment of Civil Engineering
IIT Roorkee
Module CE-251
Building Materials,Construction and Estimation
Lecture 4: Aggregates
-
8/10/2019 CE 251 Lecture 4A
2/15
CE-251 - 2Lecture 4
Aggregate Sources
!
Natural:
" natural sand & gravel pits, river rock
" quarries (crushed)
! Manufactured & recycled materials:
"
steel mill slag
" steel slugs
" expanded shale
" styrofoam
-
8/10/2019 CE 251 Lecture 4A
3/15
CE-251 - 3Lecture 4
Geological Classifications
! Igneous
!
Sedimentary
!
Metamorphic
#
All three classes of rock are used successfully in CE applications.
# Check physical, chemical, and mechanical properties, supplemented bymineralogical examination.
# Historical performance in a similar design.
-
8/10/2019 CE 251 Lecture 4A
4/15
CE-251 - 4Lecture 4
Aggregate Uses
"
Under foundations and pavements" Stability
" Drainage
" As fillers
" Portland Cement Concrete
60-75% of volume
80-85% of weight
" Hot Mix Asphalt
80%-90% of volume
90-96% of weight
-
8/10/2019 CE 251 Lecture 4A
5/15
CE-251 - 5Lecture 4
Aggregate Sizes
! Coarse aggregate material
retained on a sieve with 4.75mm openings
! Fine aggregate materialpassing a sieve with 4.75mm openings
! Traditional
"
Maximum aggregate size thelargest sieve size that allows allthe aggregates to pass
" Nominal maximum aggregatesize the first sieve to retainsome aggregate, generally less
than 10%! Superpave
" Maximum aggregate size one
sieve size larger than the nominalmaximum aggregate size
" Nominal maximum aggregate
size one sieve larger that thefirst sieve to retain more than10% of the aggregate
4.75mm
#4 sieve =`four openings/
linear inch
1
-
8/10/2019 CE 251 Lecture 4A
6/15
CE-251 - 6Lecture 4
Aggregate Gradation
-
8/10/2019 CE 251 Lecture 4A
7/15
CE-251 - 7Lecture 4
Semi-Log graph
-
8/10/2019 CE 251 Lecture 4A
8/15
CE-251 - 8Lecture 4
Sample Problem
-
8/10/2019 CE 251 Lecture 4A
9/15
CE-251 - 9Lecture 4
Solution
-
8/10/2019 CE 251 Lecture 4A
10/15
CE-251 - 10Lecture 4
0.45 Power Graph
Sieve Size
PercentPassing
0
100
Straight line identifies maximumdensity aggregate blend
But a special scale is needed for the sizeaxis
Pi =100
di
D
!"#
$%&n
-
8/10/2019 CE 251 Lecture 4A
11/15
CE-251 - 11Lecture 4
0.45 Power Grading Chart
-
8/10/2019 CE 251 Lecture 4A
12/15
CE-251 - 12Lecture 4
0.45 Power Grading Chart
-
8/10/2019 CE 251 Lecture 4A
13/15
CE-251 - 13Lecture 4
Types of Gradation
Maximum Density Gradation: 0.45 Power Chart
High density gradation (Well Graded)
" has a good mix of all particle sizes which means the
aggregates use most of the volume and less cement or
asphalt is needed
One-size gradation (Uniform)
" all same size = nearly vertical curve
Gap-graded
" missing some sizes = nearly horizontal section of curve
Open-Graded"
missing small aggregates which fill in holes between larger
ones
" lower part of curve is skewed toward large sizes
-
8/10/2019 CE 251 Lecture 4A
14/15
CE-251 - 14Lecture 4
Effect of Amount of Fines on the Relative Propertiesof Aggregate Base Material
-
8/10/2019 CE 251 Lecture 4A
15/15
CE-251 - 15Lecture 4
Aggregate Mining
Quarry
Sand from river deposit