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Asphalt Mixing Plant (Types of Asphalt Mixing Plant (Drum Mix (-Aggregate…
Asphalt Mixing Plant
Types of Asphalt Mixing Plant
Drum Mix
-Aggregate is dried , heated and mixed with aggregate in the drum.
-Mix is discharged into a hot conveyor that carries the mix to surge silo before loadout
-Production rate 300 ton/hr
Batch Plant
-Aggregate is removed from storage, in controlled amounts and passed through a dryer where it is heated and dried
-Aggregate passes over a screening unit (to separate the materials into different sizes and deposits into bin for hot storage)
-The combined aggregate is dumped into a mixing chamber, pugmill and mixed with asphalt.
-After mixing, the material is transferred to silo.
-Production rate is 100 ton/hr
Continuous Plant
-Process similar up to hot bins but differ during mixing
-Uses a continuous flow of aggregates into pugmill
-Bitumen is sprayed into pugmill continuously
-Continuous mixing process
Asphalt Quality
Quality Management Process
Laboratory mix design
-Selection and proportioning of binder, aggregate and filler
-Marshall mix design procedure to obtain optimum mix
-Final optimum mix: Bitumen content, VTM, VMA, VFB, flow and stability
Plant trial mix
-Optimum mix is manufactured in asphalt plant
-Mix procedures are verified: Grading, BC, VTM,VMA, VFB, flow and stability
Trial paving
-Access constructability of mix such as workability
-Test field samples properties
-Establish required compaction effort
-Establish production mix parameters
-Set tolerances for acceptance control
Site paving
-Undertaken after successful evaluation of trial plant mix and trial paving
-Parameters monitored for compliance: Grading, Bitumen content, VTM, Density, Layer Thickness and Levels
Factors Affecting Quality
Compaction
Factors affecting compaction
-Material properties, Environmental variables
-Site conditions, Types of compaction equipment
Best practice requirement:
Equipment selection
Sequence of compaction
Rolling pattern and speed
Correct roller operation
Temperature
Temperature control to avoid:
Difficulty in achieving density
Water permeability of mat
Ageing of binder
Segregation
Avoid segregation of mix:
-Variability in mix composition
-Finer fraction higher binder course
-Variation in density and voids
-Worse with large aggregate mixes
Functional mix
Functional performance indicators:
-Surface texture
-Riding quality
-Appearance
-Noise generation