CONSTRUCTION MANAGMENT

1
CONSTRUCTION MANAGMENT

• Michael A. Baca
• Nevada Department of Transportation
• Cell [phone]
• Email mbaca_at_dot.state.nv.us

2
OVERVIEW

• Aggregate
• Asphalt Pavement (Flexible)
• Concrete (Rigid)
• Construction Management
• Construction Economics

3
AGGREGATE

• Two Types of Aggregate
• Fine Aggregate
• Is material passing through a 3/8 Sieve and also
  includes mineral filler which is at least 70 of
  soil that passes the No. 200 Sieve
• Coarse Aggregate
• Is the material that has passed the No. 4 Sieve
  retained on a 1 ½ Sieve.

4
Base Coarse

• Sub-Grade
• Native material maybe sieved to take out anything
  retained by the 1 ½ Sieve
• Material is usually scarified and always
  compacted (to a standard of 90) before placement
  of base coarse
• Type 1
• Can either be processed native material or
  manufactured material from a plant or gravel pit.
• Conforms to strict mixing of materials by sieve
  analysis.
• Has a Plasticity Limit of no more than 15
• Usually needs to meet compaction of 95
• Type 2
• Is always processed material (almost always made
  hardly ever native material can be used)
• Conforms to stricter mixing of materials by sieve
  analysis
• Has a Plasticity Limit of no more than 9
• Must be compacted at a minimum of 95 (sometimes
  98)
• Type 3
• All requirements of this Type is provided in
  Special Provisions required by the Designing
  Engineers

5
COMPACTION OF BASE

• Sheepsfoot Rollers
• Vibratory Rollers
• Rubber Tired Rollers (covered in asphalt)
• Smoothwheel Rollers (covered in asphalt)
• Vibrating Baseplate Compactors
• Jumping Jack
• Crawler Tractor
• Dynamic Compaction

6
SHEEPSFOOT ROLLER

• Are most effective in compacting cohesive (clayey
  and silty) soils
• Is used to create small zones of intense
  shearing, which drives air out of the soil.

7
VIBRATORY ROLLER

• Are extremely efficient in compacting granular
  soils.

8
VIBRATING BASEPLATE AND JUMPING JACK COMPACTORS

• Mainly used to compact the backfill in narrow
  trenches for utilities

9
CRAWLER TRACTOR

• Used when compaction is necessary but not critical

10
DYNAMIC COMPACTION

• Is used only in extreme conditions
• The soils are densified at the prevailing water
  content when the energy is applied. Granular soil
  deposits located below the groundwater table also
  achieve densification.
• Can be rendered obsolete due to the application
  of geo-fabrics.

11
TESTING COMPACTION

• Three Methods Used
• Sand Cone
• Is the most reliable test for determining
  compaction
• It is time consuming
• Rubber Balloon
• Not commonly used
• Is time consuming
• Nuclear Density Meter (Nuclear Gauge)
• Reliable as long it is properly calibrated
• Sand Cone Method is used to calibrate the gauge
• It is not time consuming (Depending on the
  specification given by the engineer a test can be
  done between 15 sec. to 4 min.)

12
SAND CONE
13
SAND CONE METHOD

• A small hole (6" x 6" deep) is dug in the
  compacted material to be tested.  The soil is
  removed and weighed, then dried and weighed again
  to determine its moisture content.  A soil's
  moisture is figured as a percentage.  The
  specific volume of the hole is determined by
  filling it with calibrated dry sand from a jar
  and cone device.  The dry weight of the soil
  removed is divided by the volume of sand needed
  to fill the hole.  This gives us the density of
  the compacted soil in lbs per cubic foot.  This
  density is compared to the maximum Proctor
  density obtained earlier, which gives us the
  relative density of the soil that was just
  compacted. 

14
RUBBER BALLOON

• Step 1 After initial reading has been taken,
  dig the density hole using the field density
  plate as a template.
• Step 2 Pumping the balloon into the density
  hole. Operator takes reading at lowest point on
  the graduated cylinder.
• Step 3 Replacing the actuator bulb in the quick
  coupler changing from a pressure operation to a
  vacuum operation, pump water and balloon back
  into the cylinder.

15
NUCLEAR DENSITY METER

• Using a flat metal plate and a rod, drive a hole
  into the base material stopping 2 before exiting
  the layer. (12 thick base layer, the test is
  taken at 10)
• Place the gauge on top of the hole, slide source
  rod to the length driven
• Enter the required data of the max density and
  optimum moisture content of the soil being tested
  and the length of test
• The density is measured by the use of gamma rays.

16
WHAT IS ASPHALT PAVEMENT?

• Pavement is made of crushed aggregates and
  asphalt cement.
• Before the mix becomes pavement it is called HMA.
• Hot Mix Asphalt.

17
HMA TYPES

• Dense-Grade
• Aggregate sizes evenly distributed from the
  smallest to the largest.
• Open-Grade
• Few fines

18
PG GRADES
PG 46-34 PG 46-40 PG 46-46 PG 52-10 PG 52-16 PG 52-22 PG 52-28 PG 52-34 PG 52-40 PG 52-46 PG 58-16 PG 58-22 PG 58-28 PG 58-34 PG 58-40 PG 64-10 PG 64-16 PG 64-22 PG 64-28 PG 64-34 PG 64-40 PG 70-10 PG 70-16 PG 70-22 PG 70-28 PG 70-34 PG 70-40 PG 76-10 To PG 76-34 PG 82-10 To PG 82-34
19
PG 76 - 22

• Grades are designed for the 7 day average of the
  high and the max low temperature that an asphalt
  mat has reached ( _at_ 20mm depth ) in the area in
  which we live.
• 76C 168.8F
• -22C -7.6F
• An asphalt binder grade for a given location is
  selected on the bases of the desired statistical
  reliability. A 50 reliability means that over
  the design life of the pavement there is a 50
  chance that the actual temperatures recorded
  could exceed the max or min temperature. A
  reliability of 98 means a 2 chance of exceeding
  temperature extremes.

20
WHERE DOES ASPHALT COME FROM

• The asphalts that we use is a by product of the
  crude oil refining process. After higher grades
  of oil are drawn off in the refinery the thick
  asphalt remains and can be either used for paving
  or processed further for use in industries such
  as roofing.

21
625 BC

• The first recorded use of asphalt as a road
  building material was in Babylon.
• The road was a wide Procession Street which led
  away from the palace and was made of burnt brick
  and asphalt.
• Greek. Asphaltos which means secure

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• Until about 1900, almost all asphalt used in the
• United States came from natural resources like
• Lake Trinidad, Bermudez Lake (Venezuela),
• La Brea. Refined petroleum asphalts were designed
  
• initially to soften the natural asphalt for
  handling
• and placing. By 1907 production of refined
  asphalt
• took over and natural asphalts were not used.

25
HMA PRODUCTION

• Aggregates are divided into bins according to
  size. Depending on the design of the mix the bins
  automatically meter out the right amount of each
  size needed onto a conveyor belt which travels to
  the dryer. In the dryer the aggregate tumbles
  through the hot air drying the aggregate. It is
  necessary to get the aggregate dry. WHY?

26
WATER AND ASPHALT DONT MIX!

• It is necessary to get all the moisture out of
  the aggregate so that the asphalt will adhere to
  the aggregate.
• In the mixer the rocks are coated with heated
  asphalt.
• The finished product is for the most part 95
  aggregate 5 asphalt.

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28
PUG MILL

• .

29
MINERAL FEEDINGMARINATION

• 401.03.08

30
PROPER COATING

• .

31
CALIBRATING THE MARINATION PLANT

• To calibrate a marinating plant the aggregate
  weigh system must be calibrated and the lime
  weigh system must be calibrated.

32
TIME TO TPH

• 1min 56sec. (156) 116sec.
• Actual tons recorded 15.42
• 15.42
• 0.132931 tons every sec.
• Times that by 60 7.975862tons per min (TPM)
• Times that by 60 478.6tons per hour (TPH)

33
DAY TWO

• Continue Marination calibration
• Marinating Plant Inspection
• Hot Plant Calibration
• Hot Plant Inspection
• Sampling
• Temperatures

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COMPONENTS

• Dryer Drum Plant

• Cold Feed bins
• Asphalt storage
• Dryer
• Emissions control
• Storage silos

36
BATCH

• Batch Plant

• Cold feed bins
• Asphalt storage
• Dryer
• Emissions control
• Storage silos

37
COLD FEED BINS

• Cold feed bins are used to accurately meter the
  different aggregates used in the mix.
• From here the aggregate goes to the dryer drum.

• The amount of each aggregate is controlled
  by a combination of the gate opening and the belt
  speed.

38
AGGREGATE COLD FEED

• The aggregate feed system
• is the first major component of a HMA plant.

• I

39
COLD FEED BINS

• 1

40
BINS

• Cold feed bins should never be overcharged to the
  point where material will flow over to the next
  bin.
• Bins should be kept full enough so that a uniform
  flow of that material is ensured throughout the
  days production.

41
Proper Cold Feed Function

• Correct sizes of aggregates.
• No segregation of aggregates.
• No intermixing of aggregates.
• Accurately calibrated, set and secured feeder
  gates.
• No obstructions in the gates or feeder.
• Correct speed control settings.

42
AGGREGATE

FEED

• Bins picture of

• A conveyor belt below the cold feed bins
  transfers the aggregate to the dryer where
  aggregate is dried and heated.
• Drum plants produce mix continuously, a weigh
  scale is used to weigh the aggregate before it
  enters the dryer so the amount of asphalt can be
  accurately added.

43
WIEGH SCALES

• RAM

• MILL

44
SCALE SENSOR
45
DRYERS

• Parallel Flow
• Counter Flow

• Dryers

46
PARALLEL FLOW

• In a Parallel Flow drum aggregates are dried and
  heated as they are tumbling through the hot air
  stream.
• The hot air is created by the burner and is
  pulled through the drum by the exhaust fan.

47
COUNTER FLOW

• In a parallel flow drum the aggregates move in
  the same direction as the hot hot air.
• In a counter flow plant the aggregate moves in
  the opposite direction as seen here.

48
PARALLEL? COUNTER?
49
BATCH PLANT

• Batch

• In a batch plant the dried hot aggregates exit
  the dryer and travels up a bucket elevator to the
  batch tower, where they are separated by large
  sieves and stored in the hot bins. The amount of
  each aggregate is accurately proportioned by
  weight in the weigh hopper.

50
BATCH PLANT

• BA

• After weighing the aggregates they are dropped
  into the pugmill where they are mixed with
  asphalt.
• After the two are mixed the mix is either dropped
  into a truck or conveyed to a silo.

51
EMISSION CONTROLS

• As hot air passes through the aggregate it picks
  up some fine sand and dust particles. These
  particles are removed by the emission control
  system before the air goes into the atmosphere.
  Most plants have primary and secondary collectors
  to remove the particles. Sometimes these
  particles are put back in small percentages.

• PICS

52
COLLECTORS

• .

• .

53
BAG HOUSE
54
THE BAG HOUSE
55
.

• .

• Asphalt Storage.

56
OVERVIEW
57
STORAGE SILOS

• Pic silo

• Drum mix plants must have storage silos since
  they produce mix continuously.
• Batch plants do not require a silo but often do
  have storage to increase plant production.

58
STOCKPILES

• Good stockpiling procedures are crucial to HMA
  production. Properly stockpiled aggregates retain
  their gradation. Poorly stockpiled aggregates
  segregate that is they separate by size, and
  gradations varies within the stockpile.
  Precautions should be taken to keep stockpiles
  separated to maintain the required gradations.
  This is achieved by keeping stockpiles widely
  spaced by using bulkheads between stockpiles or
  by storing aggregates in bins. Bulkheads should
  extend the full depth of the stockpiles.

59
WHATS WRONG WITH THIS STOCKPILE?
60
HANDLING

• All handling degrades individual aggregates to
  some extent. Therefore handling should be
  minimized to prevent degradation and segregation
  that could make that unsuitable for use. There
  are no set rules for the handling of stockpiles
  at the hot plant for HMA production but the
  national guideline for front loaders is that the
  sample taken should be from a near vertical face,
  from the bottom to the top of the stockpile
  one-bucket load. This means that the height of
  the stockpile should never be over the loader.

61
SPECIFIC GRAVITY

• The specific gravity of an HMA is the ratio
  between the weights of a given volume of the HMA
  and the weight of an equal volume of water.
  Specific gravity provides a means of expressing
  the weight-volume characteristics of material.
  These characteristics are important in
  calculating the volumetric properties of the
  compacted mixture.

62
SPECIFIC GRAVITIES

• Insert

63
RICE

• You will never achieve the theoretical maximum
  voidless density behind the paver.
• If you average 92 compaction behind the paver
  then theoretically 8 will represent air voids.

64
VOIDS
65
AGGREGATES

• All aggregates do not weigh the same, just
  because they take up the same volume doesnt mean
  they have the same mass.

66
INTERLOCKING

• 2

67
STABILOMETER

• Insert 3.11

• A vertical pressure is exerted on the sample and
  the horizontal pressure that develops is measured.

68
HVEEM

• Hveem is the result of stabilometer, the density
  and void content measurements.

69
Checklist for Material Handling

• Do aggregates meet gradations?
• Are proper sizes being introduced?
• Is aggregate storage satisfactory?
• Are stockpiles separated properly?
• Are stockpiles constructed properly?
• Is stockpiled material handled properly?
• Is segregation being controlled?
• Is mineral filler being kept dry?

70
Checklist for Cold Feed

• Do cold feed bins contain proper size aggregate?
• Are cold feed bins charged properly?
• Are the feeders in proper working order?
• Are feeders calibrated?
• Are the gates set correctly?
• Are all the feeders feeding continuously?
• (are they interlocked?)

71
Checklist for Asphalt at plant.

• Is the asphalt heated to its specified
  temperature?
• Is that temperature being maintained?
• Have the lines been checked for leaks?

72
Checklist for Drum Plant

• Have aggregate feeds been calibrated?
• Has the asphalt feed been calibrated?
• Are the aggregate and the asphalt feed
  interlocked?
• Is the asphalt up to temperature?
• Are the plant parts in good condition and
  adjusted? (bearings locked , leaking pipes,
  ripped belts, etc.)

73
Checklist for Dryer/Collector

• Is the aggregate dry?
• Are aggregates at temperature?
• Is Dryer in balance with the rest of the
  equipment.
• Are reintroduced fine calibrated and are they
  being feed uniformly?
• Are flights in good condition?

74
Checklist for Storage Bins

• Does the silo contain a batcher?
• Are baffles working properly?
• Is the discharge opening properly configured to
  prevent segregation?
• Does the gate open and close efficiently?

75
Checklist for Misc. Responsibilities

• Have truck beds been inspected?
• Are truck beds drained after spraying?
• Do trucks meet weight requirements?
• Are trucks equipped with tarpaulins?
• Is the mix uniform?
• Is the general appearance of the mix
  satisfactory?

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PROPER LOADING
77
HMA BASES

• Subgrade (soil)
• Granular base course (aggregate)
• Existing asphalt pavement
• Existing Portland Cement Concrete Pavement.
• Rubbilized pcc pavement.
• Brick pavement

78
SUBGRADE

• Subgrade--- the soil foundation for the
  pavement.
• The subgrade must be properly graded to line and
  grade and it must thoroughly and uniformly be
  compacted to the required density.
• The subgrade should be inspected to identify
  soft soil or soil that is too weak to support the
  paving equipment and haul trucks.

79
BASE COURSE

• A base course can either be a layer of granular
  material placed on the subgrade and compacted or
  a layer of asphalt paving.
• Subgrade.
• Base course.
• Asphalt pavement.

80
PRIME TACK COATS

• They are applications of liquid asphalt applied
  to the base material or lower layers of the
  pavement.
• Prime Coat is a cut back or emulsified prime that
  is applied to the base course of untreated
  material.
• Tack Coat are emulsified asphalts sprayed on top
  of existing pavement prior to an overlay.

81
BOOT TRUCK

• .

82
THE SPRAY BAR
83
CALCULATING LOAD COVERAGE

• It is important to know how much linear distance
  of roadway can be covered by the asphalt
  contained in the distributor.
• L 9TWR
• Llength of the spread in feet
• TTotal gallons in the distributor
• WSprayed width of the roadway in feet
• RRate of application in gallons per yd²
• This is an estimate not to be used for
• pay calculations in the book.

84
CALCULATING ACTUAL COVERAGE

• To calculate the actual coverage you must have
• Length
• Width
• Gallons used
• Temperature

85
CALCULATING COVERAGE

• To find out how many tons it will take to cover
  an area use this formula.
• Tons Yd² x application rate
• Gallons per Ton

86
CALCULATING ACTUAL COVERAGE

• To find out what was actually put down in the
  area use this formula.
• Application rate
• Tons x Gallons per Ton
• Yd²
• Use this formula for your records in the pay book

87
MILL

• When HMA is placed over an existing pavement it
  is called an OVERLAY.

88
MILLING TEETH
89
MILLED SURFACE
90
VERTICLE EDGE
91
VERTICLE EDGE
92
VERTICLE EDGE
93
After a pavement has been milled, the resulting
surface is quite dirty and dusty. The surface
should be cleaned off by sweeping or washing
before any HMA overlay is placed otherwise the
dirt and dust may decrease the bond between the
new overlay and the existing pavement Milling
also produces a rough, grooved surface, which
will increase the existing pavements surface
area when compared to an ungrooved surface. The
surface area increase is dependent upon the type,
number, condition and spacing of cutting drum
teeth, but is typically in the range of 20 to 30
percent, which requires a corresponding increase
in tack coat (20 to 30 percent more) compared to
an unmilled surface
94
SHUTTLE BUGGY

• HMA TRANSFER VEHICLE.

95
PAVING HMA
96
SPANDREL

• 0.2146 x r²
• Volume in ft²
• 0.2146 x r² x Depth
• Volume in ft³

97
THE PAVER
98
AUGER
TYPE

• .

99
BAR FEEDER
100
SLAT TYPE CONVEYOR
101
MATERIAL FEED RATE
The amount of HMA in front of the screed (the
material head) can also affect screed angle and
thus mat thickness.  If the material head
increases (either due to an increase in material
feed rate or a reduction in paver speed), screed
angle will increase to restore equilibrium, which
increases mat thickness.  Similarly, if the
material head decreases (either due to a decrease
in material feed rate or an increase in paver
speed) screed angle will decrease to restore
equilibrium, which decreases mat thickness.
102
In order to maintain a constant mat thickness for
a change in paver speed or material head in front
of the screed, the natural equilibrium of forces
on the screed cannot be relied upon and the
screed angle must be manually adjusted using a
thickness control screw or depth crank.  Screed
angle adjustments do not immediately change mat
thickness but rather require a finite amount of
time and tow distance to take effect.  The next
slide shows that it typically takes five tow
lengths (the length between the tow point and the
screed) after a desired level is input for a
screed to arrive at the new level.
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SKI
105
SENSORS
106
SCREED
107
COMPACTION

• .

108
TARGET

• The sweet spot.

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JOINT COMPACTION
111
TESTING COMPACTION

• Using a Nuclear Density Gauge
• Set the Gauge to backscatter
• Need to do four tests at North, South, East, West
  of same location
• Instead of a Proctor No. use the Marshall No.

112
TYPICAL TEMPS
113
HMA temperature affects its binder viscosity,
which affects compaction in two ways (1) the
colder and more viscous the binder, the less
actual amount of air void reduction for a given
compactive effort, and (2) HMA can only be
compacted until it reaches cessation temperature,
therefore initial HMA temperature and mat
cool-down rate establish a fundamental compaction
parameter the overall time available for
compaction. Many factors influence HMA
temperature and cool-down rate including initial
mat temperature, mat thickness, temperature of
the surface on which the mat is placed, ambient
temperature and wind speed. CESSATION (idleness,
from cessare to delay, be idle to cease) a
temporary or final ceasing as of action
114
WHAT IS CONCRETE?

• Is made up cement (usually Portland Cement)
• Mixed with a certain percent of water and
  aggregates creates a concrete mix
• Additives and other materials can be added to
  influence the properties of the mix
• After placement of the mix, hydration occurs the
  mix solidifies and becomes concrete
• Hydration is the chemical rxn between water and
  the chemical compounds in cement.
• Concrete is strong in compression but weak in
  tension

115
CEMENT

• Is manufactured in processing plants with the
  following chemicals
• Lime from limestone or shale
• Silica from Sand, clay, or shale
• Alumina Clay, fly ash, shale
• Iron Iron ore, clay
• These materials are crushed, heated and then
  crushed again and sieved (No. 325) to obtain the
  binding powder of cement.

116
TYPES OF CEMENT

• Type I Normal
• Type IA Normal, Air-Entraining Cement
• Type II Moderate Sulfate Resistance
• Type IIA Modified Sulfate Resistance, Air-
  Entraining
• Type III High Early Strength
• Type IIIA High Early Strength, Air-Entraining
• Type IV Low Heat of Hydration
• Type V High Sulfate Resistance

117
CONCRETE MIX

• Is made according to ratios
• Cement to Fine Aggregate (FA) to Coarse Aggregate
  (CA)
• Water is dependent on design needed
• Admixtures are added before or during the mixing
  of the concrete mix
• And the amounts are based on tables provided by
  either the American Concrete Institute (ACI) or
  American Standard for Testing Materials (ASTM).

118
CEMENT TO WATER RATIO

• Depends on type of cement used and what the
  designers want, dictates the amount of water
  needed.
• Usually measured by gallons per sack of cement
• Ratios
• 0.22 to 0.28 is amount needed to just hydrate
  cement
• 0.30 to 0.45 is used for high quality concrete
• 0.45 to 0.60 is general purpose (it is best to
  stay below 0.5)
• Smaller ratio leads to stronger concrete but is
  less workability.

119
CHEMICAL ADMIXTURES

• Air-Entraining
• Water reducing admixtures (5 to 10)
• Super Plasticizer - High range water reducing
  admixtures (12 to 30)
• Retarders Delay onset of hydration
• Accelerators Increases onset of hydration

120
MINERAL ADMIXTURES

• Pozzolans Are very fine grained silica
• Fly Ash Comes from burning coal in power plants
• Ground Blast Furnace Slag Comes from steel
  production plants
• Silica Fume is a by product from the silicon
  industry

121
CURING CONCRETE

• Curing is the process of keeping concrete under a
  specific environmental condition until hydration
  is relatively complete. Because the cement used
  in concrete requires time to fully hydrate before
  it acquires strength and hardness, concrete must
  be cured once it has been placed.
• If concrete is not cured it will gain only about
  50 of the desired strength.
• If concrete is cured for only 3 days, it will
  reach about 60
• If cured for 7 days, it will reach 80
• 28 days is usually the optimal curing time needed
  to reach 100
• Temperature during the curing process is crucial
  as well.
• Temperatures below 50F (10C) are unfavorable for
  hydration
• Optimum environment is 95 humidity and
  temperature is 73F /- 3F

122
TESTING CONCRETE

• Slump Test
• Temperature
• Kelly Ball
• Unit Weight Test
• Air Content Test
• Pressure Method
• Volumetric Method
• Cylinders
• Beams (Flexural Strength Test)
• Slump Flow Test

123
SLUMP TEST

• Immediately fill the mold in three layers, each
  approx. 1/3 of the volume of the mold.
• Rod each layer 25 strokes. Rod throughout its
  depth so that you penetrate the underlying layer.
• After the top layer has been rodded, strike off
  the surface of concrete with the tamping rod.
• Remove the mold in one motion straight up. The
  slump test must be completed within 2.5 min.
  after taking the sample.
• Measure the slump by determining the vertical
  difference between the top of the mold and the
  displaced original center of the top of the
  specimen.

124
TEMPERATURE

• Is The thermometer should be accurate to plus or
  minus 1F(0.5C).
• Should remain in a representative sample of
  concrete for a minimum of 2 minutes or until
  reading stabilizes.
• A minimum of 3 in. of concrete should surround
  the sensing portion of the thermometer.
• Temperature reading should be completed within 5
  min. after obtaining the sample.

125
KELLY BALL

• Is an apparatus used for indicating the
  consistency of fresh concrete, consisting of a
  cylindrical weight 6 in. (150 mm) in diameter,
  weighing 30 lb (14 kg) with a hemispherically
  shaped bottom, a handle consisting of a graduated
  rod, and a stirrup to guide the handle and serve
  as a reference for measuring depth of
  penetration.
• Is used only for concrete pavement jobs.

126
UNIT WEIGHT TEST

• Measure filled in three layers of approximately
  equal volume. Top layer filled to avoid
  overfilling. Each layer rodded 25 strokes when
  0.5 ft3 or smaller measures are used. Each layer
  rodded 50 strokes when 1 ft3 or larger measure is
  used. Bottom layer rodded uniformly over the
  cross section of the measure and throughout its
  depth without rod forcibly striking the bottom of
  the measure. Second and top layer rodded
  throughout its depth, so that the strokes
  penetrate about 1 in. into the underlying layer.
  Measure tapped smartly 10 to 15 times with mallet
  after each layer is rodded. An excess of concrete
  is protruding approximately 1/8 in. above the top
  of the measure after rodding and tapping. Top
  surface struck off with plate or bar and finished
  smooth. Plate pressed on top surface of measure
  covering two-thirds of surface and plate
  withdrawn with sawing motion. Plate again placed
  over original two-thirds of surface and advanced
  with vertical pressure and sawing motion. Several
  final strokes are made with edge of plate to
  produce smooth finished surface. Exterior of
  measure cleaned and measure weighed to obtain
  gross weight. Unit weight calculated as follows
• Unit Weight, lb/ft3 Net Weight
• Volume of Measure
• where
• Net Weight gross weight minus the weight of
  the measure calculated to the nearest 0.01 lb
• Volume of Measure, ft3, as stated on calibration
  form

127
AIR CONTENT PRESSURE METHOD

• Fill the apparatus exactly as in the Unit Weight
  Test.
• After filled place cap on and fasten the flanges.
• Using a rubber syringe, inject water through one
  petcock until water emerges from the opposite
  petcock.
• Jar the meter gently until all air is expelled
  from the same petcock.
• Pump air into the air chamber until the guage
  indicator is on the initial line.
• Open the air valve between the air chamber and
  the measuring bowl.
• Tap the sides of the measuring bowl sharly, and
  lightly tap the pressure gauge.
• Read the percentage of air conctent on the dial
  gauge.
• Determine the aggregate correction factor
  according to ASTM C231 and subtract it from the
  reading obtained in step 11.

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AIR CONTENT VOLUMETRIC METHOD

• Is also referred to a the rolo-meter
• Mostly used when freeze/thaw is a main concern
  for concrete.
• The method in the beginning is exactly like the
  pressure method.
• Only after filling a clasping, the operator needs
  to invert and agitate until the concrete settles
  free from the base.
• Then add in 1-cup increments using the syringe,
  sufficient isopropyl alcohol to dispel the foamy
  mass on the surface of the water.
• Make a direct reading of the liquid in the neck
  to the bottom of the meniscus to the nearest 0.1.

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CYLINDERS

• Depending on aggregate size dictates the size of
  cylinder molds required.
• Is made same way 3 layers and each layer is
  rodded 25 times.

130
COMPRESSION TEST

• Cylinders that were made are tested after they
  cure.
• After 7 day cure
• After 14 day cure
• After 28 day cure

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BEAMS (FLEXURAL STRENGTH TEST)

• In the flexural-strength test, a test load is
  applied to the  sides  of  a  test  beam.
   Although  the  test  can  be performed upon
  beams sawed from existing concrete structures, it
  is more commonly performed upon beams that are
  cast for testing purposes. The standard test beam
  measures 6 inches by 6 inches by 21 inches.

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REINFORCED CONCRETE

• Concrete needs to be reinforced due to its
  negligible tensile strength.
• Rebar - Almost always deformed to ensure a good
  bond between the bar and the concrete

133
TYPES OF CONCRETE CONSTRUCTION

• Cast-In-Place
• Prestressed Concrete
• Postensioned Concrete

134
FACTORS THAT INFLUENCE STRENGTH

• Age Older is better
• Water Cement Ratio, Lowering is better (above
  0.25)
• Curing Wet (RH gt 80)
• Curing Temperature Higher is better, up to
  about 140 F

135
SECONDARY FACTORS ON STRENGTH

• Aggregate Texture Rougher is better
• Gradation of Aggregate
• Shape of Aggregate Angular for Strength
• Pozzolans Increases Strength and Hardening Time
• Cement Type
• Air Content Lower is better
• Aggregate Size Smaller is Stronger (bigger is
  cheaper)

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CONCRETE

• Remember there are two types of concrete
• Concrete thats cracked
• And Cracked Concrete
• Control joints are placed in concrete so that
  cracks will form in the joints during
  freeze/thaw.

137
CONSTRUCTION MANAGEMENT

• Activity Scheduling
• Activity on Arrow
• Activity on Nodes

138
DEFINITIONS

• Early Start (ES) Earliest you can possibly
  start a task
• ES Latest EF of Predecessors
• Early Finish (EF) Earliest you can possibly
  finish a task
• EF ES Duration
• Late Start (LS) Latest you can start without
  delaying the project completion
• LS LF Duration
• Late Finish (LF) Latest you can finish without
  delaying the project completion
• Critical Path Sequence(s) of task where delay
  in any one path will delay the project completion
• CP Sequence where slack (Float) equals zero
• Float (Slack) Time you can delay a task without
  delaying completion
• Float LS-ES LF - EF

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CRITICAL PATH PROBLEM
140
Construction Economics