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Advantage of Central Mix Plant
Higher Production Rates
Plant operator responsible for:
Loading mixer and controlling discharge
4 element of wet plant operation
Charging Time, Mixing Time, Discharge Time, Return Time
Typical Mixing time for 10 yd3
2 min
plant equipment which gives it ability to blend ingendients before entry into mixer
efficient mixing
Fluid and consistent mixes provide
faster discharge
Central Batch Plants are capable to
start next batch while discharging
Slump affects amperage needeed to mix, higher amperage means
stiffer concrete
types of mixers
horizontal and tilt up
standand equipment, most part and pieces can be maintained by plant operators
In-house maintenance
maintenence for Batching Control Panel, electrical equipment
Specialized maintenence
tool to keep track of several activities in the daily operation and control of the batch plant.
daily plant log
Basis of strength in concrete
W/C ratio
Admixtures for concrete are
Chemical and Mineral
Concrete achieves ___% of untilate compressive strength in 7 days
65-75
what percentage does the paste represent in the concrete mixture
20-40
A mixture in a freshly harded state, delivered to the site is
Ready Mix Concrete
High Profile Bacthes have components:
above ground level
Whats is the difference between wet-batch plants and dry-batch plants
The Mixer
Liquid advixture dosage is in:
floz/yd3
minimum concrete temprature of concrete mixtures in cold weather is:
50F
Batch plant mixers can be grouped in:
Tilt and horizontal mixers
non-agitating trucks are used for:
short haul projects
10yd3 concrete buckets are helpful for:
high elevation
concrete mictures made a mobil truck mixer is commonly:
Volume based
Common concrete barrel size in NJ is:
4-12 yd3
production, delivery and placecmnt of ready mix concrete is based on:
ASTM C-94
Scale that has a counter weight
Scale Lever
Scale that is electronic
Single Load
Scale that has no moving parts
Four Point
In batching, Cement should be weighed:
First
In batching Pozzolans should be batched:
Second
water batching can be done by:
Volume and Weight
loading method which blends fine and coarse and cememt before
Ribbon Batching
Loading method where trucks get aggregate, water and admixtures; thenthey move to the next station to get the cement
Dry Batching
How many types of batch plants are usually considered
Wet and Dry
Performance and Prescription basis are _____ and ____ to order conrete
options and criteria
easiest way to increase temp of concrete is
heating water
concrete batch plant is the equipment where ________ is manufactured
ready mix concrete
configuration of batch plant based on
Location of components and high or low
W/c ratio, unit wieght, slump are
characteristics of concrete mixture
formula for absolute volume of material
weight of material/(spec grav x density of water)
tail water is ___%
15-30
What has a greatest impact on batching process
Aggregate moisture
Tolenances and calibration governed by
Concrete Plant Manufactures Bureau
Which condition is more expensive to solve in batching
Overweight
Checking weather forecast and air compressors are part of activities included in the ____
activities, daily checklist
aeration of cement silos when air pressure is applied at ___ psi
0.5-5
Typical batching tolerances for cement, aggregate, water, admixtures
0.3 of scale capacity, 1211 required weight
Bulk density varies from ________ lbs/ft3depending on degree of aeration
60-94
What 2 conditions slow down the batching-discharge process and increase the potential errors and batch accuracy?
Vacuum and Pressure
How much water is allowed to continue into mixing time
up to 25%
factors affecting truck ability to accept material
mixer design, drum opening size, rotational speed, slump
types of aggregate moisture
Free, SSD, Absorbed