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83 Cards in this Set
- Front
- Back
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Asphalt Cement
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~Semi-solid at room temp
~Excellent binding capabilities ~Used in hot mix |
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Asphalt Emulsion
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~Asphalt blend with water
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What is the ratio of water to asphalt in an asphalt emulsion?
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~70% Asphalt
~30% Water ~Used cold patch material |
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What are the two main uses of asphalt?
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~Pavements (Main Use) hot mix
~Sealing pavements - cracks |
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Hot Mix
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Aggregate asphalt used for pavements surface
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Cold Mix
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~Aggregate & Asphalt emulsion
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Prime Coat
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~sprayed onto soil to help the soil bond to the pavement
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Name the five methods to reduce asphalt stripping.
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~Increase asphalt percent
~Use high viscosity asphalt ~Use clean aggregate ~Additives ~Alter grading of aggregate |
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Rutting
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~Accumulation of permanent deformation in the wheel path
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Fatigue Cracking
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~Failure due to repeated bending
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Thermal Cracking
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~Failure due to repeated temperature change
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Bleeding
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~Migration of asphalt to the surface
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Raveling
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~Loss of flexibility due to oxidation and aging (becomes dry and brittle)
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Name and describe the two mix design methods.
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Super Pave - (current standard) run lab tests at varied temps
Marshall Method - old method (obsolete) run lab tests at one temp |
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How is bituminous asphalt lab tested?
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1. Run trial batches before bituminous asphalt is used in project
2. Vary asphalt content, pick best mix based on results |
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What are the four steps in the Super Pave Design Method?
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1. place the hot mix into the mold
2. apply compressive force to compact mix and gyrate at the same time 3. mold is 6" dia x 4" high 4. take the sample and test at different temps for deformation |
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What are the three steps in the Marshall Design Method?
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1. compact hot mix in mold with a drop hammer
2. hammer is ten pounds and drops 18" 3. compact one side, flip, compact other side |
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Using the Marshall Design Method, how many drops of the hammer does it take for light duty pavement? medium? heavy?
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Light - 32 drops per side
Medium - 50 drops per side Heavy - 75 drops per side |
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How are small batches of asphalt for driveways and sidewalks produced?
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~in a small pug mill
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How are larger batches of asphalt produced?
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~large quantities of asphalt are produced using the continous drum process
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Describe the continous drum process.
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1. a large basket is loaded with aggregate
2. the aggregate goes up a conveyor into a heated drum 3. asphalt cement is injected into the drum 4. the bituminous asphalt concrete is placed in a truck 5. when the truck is full, the bit asp concrete goes up another conveyor into a silo for storage |
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What percent of of asphalt does the Massachusetts Highway Dept. require be recycled material?
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25%
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What are the benefits of recycling asphalt?
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Reduces Construction Costs
~less new material ~less disposal (asphalt is considered hazardous) |
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What are the five reasons for milling asphalt?
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1. creates recyclable material
2. saves gutters 3. saves from having to reset structures (manholes, water valves, etc...) 4. reduces bridge load 5. maintains tunnel clearance |
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Stripping
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~the loss of bond between the aggregate and the asphalt due to moisture getting in between the aggregate and the asphalt
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What is the number one cause of asphalt failure?
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Stripping
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What are the seven objectives of bituminous asphalt concrete?
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1. Stability - resists deformation
2. Fatigue Resistance - resistance to cracking from repeated load 3. Develop resistance from thermal cracking 4. Resistance to moisture induced damage (stripping) 5. Resistance to hardening (aging) 6. Skid Resistance - enough surface texture 7. Workability - make it easy to place the mix |
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What are the benefits of adding rubber tire crumbs to bit. asph. concrete?
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1. increases elasticity
2. increases bond between asphalt and aggregate 3. reduces tire disposal problem |
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Describe the five typical pavement sections.
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1. Wearing coarse - 1-3" thick (smoothness, traction)
2. Binder coarse - 2-5" thick (stability) 3. Base coarse - 6-8" thick (soil, processed gravel) 4. Sub-base - 6-8" thick (optional, gravel) 5. Sub-grade - (native soil) |
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What is the temperature of Hot Mix?
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~250-350 Degrees F
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What can be used instead of a base coarse and how would it be determined?
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~geotextile
~cost analysis (what's more economical?) |
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What is the typical density of asphalt?
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~150 lbs/cubic foot
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How does temp affect the stability of asphalt?
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~hard and brittle at low temp
~soft and flexible at high temp |
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What is a flashpoint test?
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~measure the temp at which asphalt ignites
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How does the direction of the grain affect wood?
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~strength, shrinkage vary according to direction
~wood is more stable, stronger in longitudinal direction |
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What is the formula for determining the moisture content of wood?
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M = mass of water/mass of dry wood = wet weight-dry weight/dry weight
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Describe the two types of moisture.
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1. Free water - found in cell cavities
2. Bound water - found in cell walls |
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Fibersaturation Point
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~cell walls are saturated but there is no free water
~typically the moisture content = 3% |
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When does shrinkage in wood occur?
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~when you start to lose bound water
~least shrinkage is longitudinal, most is tangenial |
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Equilibrium Moisture Content
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~moisture content in wood based on atmospheric conditions
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What are three uses for wood in construction?
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~structural framing
~flooring ~foundations |
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Where does softwood come from?
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~Coniferous trees (pine trees)
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Where does hardwood com from?
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~Decidous trees (shed leaves)
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Cambium
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~thin growth layer of tree 1/5" outside layer where growth occurs
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Sap wood
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~live portion of the tree
~conveys food and water for the tree |
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Heart wood
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~provides structural strength for the tree
~dead portion of tree |
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Anisotropic
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~properties vary in different directions
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How is engineered wood made?
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~seperate wood fibers and then rebind them with glue
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At what percent moisture content does shrinkage/expansion occur in wood?
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30% - 0%
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What is the formula for determining how much shrinkage will occur?
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m = original moisture content - new moisture content/final saturation point
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Name four types of wood produced for construction.
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1. Dimensional lumber
2. Timber 3. Round stock 4. Engineered |
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Dimensional Lumber
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Mostly used for framing
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Timber
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typically used for landscaping or timber construction
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Round Stock
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used for posts and poles (utility poles, pilings, etc)
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What are the five steps in wood production?
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1. saw into shape
2. season (put into ovens to draw out the moisture) 3. sufacing (Dimensional lumber cut to final size) 4. Graded for quality 5. Preservative treatment (PT) |
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What is "green" wood?
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~wood that is not seasoned
~moisture content = 20-200% |
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What is the moisture content of seasoned wood?
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15-19%
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What is the typical equilibrium moisture content in the Northeast?
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12%
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Knots
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~results of tree branches growing
~creates a weak tensile strength |
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Shakes
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~lengthwise seperation of the wood between rings
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Wane
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~bark left on edge of board
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Pitch Pocket
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~voids inside of the wood which are filled with sap
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Checks
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~similar to shakes
~come from drying out the wood |
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Splits
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~similar to checks
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Warping
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~distortion
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What are the four types of warping?
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1. crooking
2. bowing 3. cupping 4. twisting |
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What is the density of dry wood?
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20-45 lbs/sq ft
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What are two positive properties of wood?
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~very good thermal barrier
~good electrical insulator |
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What are two negative properties of wood?
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~natural defects
~combustible |
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How much stronger is the radial directon that the longitudinal direction of wood?
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~20x
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Generally, is tensile strength greater than compressive strength in wood?
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Yes
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How do we minimize creep in wood?
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keep stress equal to or less than 90% of allowable stress where load is applied for 10+ years
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Name two things that cause wood degradation.
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1. Fungus
2. Insects |
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What four conditions must be present for fungus to grow on wood?
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1. Wood fiber - food
2. Temp - 4-100 deg F 3. Moisture - greater than 30% 4. Oxygen |
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What impact does fungus have on wood?
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~fungus decays wood
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Name three ways to prevent fungus.
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1. painting
2. sheltering from the rain 3. chemically treat |
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What is the most common type of insect that will attack wood?
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Termites
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Name the two types of termites.
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1. subterranian (found in this area)
2. non-subterranian (found in warmer climates) |
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What are four ways to control termites?
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1. chemically treated wood
2. metal shields 3. seal cracks/joints 4. chemically treat soil |
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Name three ways to prevent fungus.
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1. painting
2. sheltering from the rain 3. chemically treat |
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What is the most common type of insect that will attack wood?
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Termites
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Name the two types of termites.
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1. subterranian (found in this area)
2. non-subterranian (found in warmer climates) |
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What are four ways to control termites?
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1. chemically treated wood
2. metal shields 3. seal cracks/joints 4. chemically treat soil |
