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CE 4650 Quiz Lec 16-17

Terms in this set (45)

Limitation of Marshall Mix Design
lab compaction method, mold size, measure of compactibility, durability
4 Steps of Superpave Mix Design
1. materials selection
2. design aggregate structure
3. design binder content
4. moisture sensitivity
Material Selection
more angular, more cubical, less natural sand
Consensus Properties
Coarse aggregate angularity, fine aggregate angularity, flat-elongated particles, clay content
(required test)
Source Properties
toughness, soundness, deleterious materials
(optional)
Coarse Aggregate Angularity (CAA)
evaluates angularity by visually examining each particle and counting the number of fractured faces
one crushed face, two crushed face
Fine Aggregate Angularity (FAA)
evaluates angularity of fine aggregate, measuring uncompacted void content on fine agg sample
uncompacted voids =
(V-Vfine)/V 100 = (V - (M/Gsb))/V 100
natural sands <45
manufactured sands >42
Flat, Elongated Particles
Evaluate coarse agg tendency to impede field compaction
based on dimensional ratio of particles: agg dimension: length, width, thickness
elongated
ratio of length to width
Flat
Ratio of width to thickness
clay content
evaluate relative proportions of clay-like materials in fine agg, can coat agg particles and prevent proper asphalt binder agg bonding
Based on Sand Equivalent value
Sand Equivalent (SE)
(Sand reading/clay reading ) *100
Superpave Agg Specifications
Required on total aggregate blend, not individual agg stockpiles
nominal maximum aggregate size
one size larger than the first sieve to retain more than 10%
maximum aggregate size
one size larger than nominal maximum size
Maximum density line
straight line from the origin though 100% passing the maximum sieve size
0.45 gradation chart - features
restricted zone: from 2.36mm to 300mm sieve, 2-3% on either side of line
max density line
control point

fine agg are above line, coarse agg are below line
Aggregate tests
consensus properties - required
source properties - optional
aggregate criteria
based on aggregate blend
based on traffic and depth into pavement
Design aggregate structure
0.45 power chart
control points and restricted zone
Mixture Design
selection of optimum amount of asphalt cement content to satisfy a prescribed Volumetric and Densification criteria
Criteria
Volumetric: voids in total mix, VTM; voids in the mineral agg, VMA; voids filled with asphalt, VFA
Densification: stages during compaction process, initial stage(construction), design stage, final stage(end of service)
Densifcation
consolidation, reduced volume
Goals of Compaction Method
simulate field densification of traffic and climate
accommodate large aggregates
measure compactability
conducive to QC
Superpave Gyratory Compactor (SGC)
texas equipment, french operational characteristics, 150mm diameter, height recordation
Compacted Specimen height
Mix design: 115mm
Moisture sensitivity: 95mm
Mix Characterization/Analysis: 140+mm
Loose Specimen
mixture max specific gravity, Gmm
height varies with nominal max size: 19mm, 12.5mm
Nini
6-9 gyrations, initial number of gyration
Ndes
50-125 gyrations, design number of gyration
Nmax
75-205 gyrations, Maximum number of gyration
Criteria for Superpave Gyratory Compactor
Primary Consolidation: %Gmm at Nini (construction
Secondary Consolidation: %Gmm at Nmax (end of life)
%Gmm (N)
%Gmm(N) = (100(Hfinal/HN)Gmb(measured))/Gmm
VTM, Va
VTM = 100 - %Gmm
Mold vs sample
Mold has greater volume than sample
Mixture Bulk Specific Gravity, Gmb
Measured is higher than the estimated one
Gmb(N)
Gmb(N) = (Hfinal/HN)*Gmb(measured)

Gmb(estimated, N) = Mass/(((pid^2)/4)HN*gammaw)
Correction Factor, CF
Gmb(measured)/Gmb(estimated) > 1
Volumetric equations
the Gmb used is for design
Va = (Gmm - Gmb)/Gmm *100
VMA = 100(1-(Gmb(1-%AC))/Gsb)
VFA = (VMA-Va)/VMA *100
Densification equations
%Gmm = 100 *(Gmb/Gmm)
%Gmm(Nini) = 100 * (Gmb(Nini)/Gmm) < 89
%Gmm(Nmax) = 100 *(Gmb(Nmax)/zgmm) <98
Gmb(N)= (Hmax/HN)*Gmb(measured)
%Gmm(Ndes) = 96
Superpave Mixture Requirements
mix volumetrics at Ndes: Va, VMA, VFA
Mix densification: %Gmm at Nini and Nmax
Dust proportion: %weight of -0.075 material/% weight of effective asphalt
moisture sensitivity
Effective Asphalt
unabsorbed binder in miz
Mix requirement for Dust proportion
0.6 <= %weight if -0.075 material/% weight of effective asphalt <= 1.2
Moisture Sensitivity
tensile strength ration of 3 conditioned specimens, 3 dry specimens -- 80% min
optional freeze cycle and hot water soak
TSR
average dry tensile strength, avg wet tensile strength
TSR = Wet/Dry >= 80%
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