CIE 110 - MATERIALS
Cold Mixes (less common, seen to fill potholes)
- solvent added to binder to reduce viscosity - material hardens as solvent evaporates
WE LOVE STEEL <3
- strong - dense (bad strength to weight ratio) - tough (high energy req'd to break --> ductile) - stiff (good stiff to strength ratio) -uniform properties (*HATE IT BECAUSE... rusts, cost of production [environmental effect])
Tools for Metallurgy
-Quenched- very rapid cooling (outside cools quicker than on the inside, we like because it creates a homogeneous system, but thermal stresses) -Tempering- slight reheating generally done to relieve thermal stresses -Annealing- combined heating & cooling intended to fine-tune phases/properties
General Forms of Oxidation
-general rust -pitting - very localized and deep pits (often aided by chlorides) -galvonic - results from 2 different metals in contact -stress-corrosion - stress tends to accelerate corrosion/rust (problematic for post-tension structures)
Control of Corrosion
1) Coatings - (always painting golden gate bridge) 2) Galvonic Protection - Zinc coating, very slow oxidation (put a thin coating on material) -Sacrificial anode - (i.e. Zn) 3) Cathodic Protection - (need to add voltage, to reverse flow of electrons) 4) Stainless Steels -Weathering steel - rust layer sticks to steel (so it won't rust further)
WOOD factors affecting strength
1) Grain Orientation 2) Knots - grain angle deviation (tension more affected) - discontinuity in material (stress concentration) 3) Density - High density, High Strength) - late wood = better/more dense, than early wood 4) Moisture Content - High strength, High toughness, High stiffness, Low moisture content
Steel Oxidation
1) Oxide takes up more volume than base metal => flaking & repeat 2) Oxide takes up less volume than base metal => cracks (because material contracts) 3) Oxide & base metal have same volume => oxide layer is thin so you don't really see the rust (i.e. stainless steel) (*All metals will oxidize in air but oxidation occurs more quickly when wet)
Failure Modes (* Strength more sensitive to grain angle in tension compared to compression.)
1) Tension Parallel to grain - fibers tear 2) Compression Parallel to grain - fiber buckling 3) Tension Perpendicular to grain - fibers separate 4) Compression Perpendicular to grain - fibers collapse & crush (* Strongest --> Tension (parallel) > Compression (parallel) > Compression (perpendicular) > Tension (perpendicular) <-- Weakest)
What is the probability that a 25-year storm event will occur this year?
1/25 = 0.04
What is the 5 year wind force event?
1/5 = 0.2 * 20% probability of exceeding SO, 80% probability.
While doing a test for bulk specific gravity, we prepare an aggregate sample that weighs 473 g and in air and 292 g immersed in water. The bulk specific gravity is:
473 - 292 = 181g ((473) / (181)) * (1) = 2.61
Density of water
= 1 g/cm^3 =62.4 lbs/ft^3 =1,000 kg/m^3
Fiber Saturation Point (FSP) of WOOD
=30% MC at which ONLY bound water remains NO shrinkage until MC < FSP --> does NOT shrink when free water is lost only when bound water is lost.
Which of the following compounds is not found in cement clinker: (a) calcium hydroxide (b) tricalcium silicate (c) tricalcium aluminate (d) dicalcium silicate
A - calcium hydroxide
The constituent in hydrated portland cement paste responsible for its strength is: (a) calcium silicate hydrate (b) calcium hydroxide (c) ettringite (d) calcium carbonate
A -Calcium silicate hydrate
Moisture induced shrinkage or swelling of wood occurs when there is: (a) a change in the amount of bound water in the fibers. (b) a change in the amount of free water in the fibers. (c) a change in microfibril angle. (d) a change in capillary porosity.
A -a change in the amount of bound water in the fibers.
The material with the highest carbon content is: (a) cast iron (b) wrought iron (c) quenched and tempered alloy steel
A -cast iron
Which of the following clear wood failure mechanisms is the strongest? (a) fiber rupture (b) fiber separation (c) fiber buckling (d) fiber crushing
A -fiber rupture
The stiffness of an FRP composite material comes primarily from the: (a) fibers (b) matrix (c) interfaces
A -fibers
The microfibril angle tends be: (a) greater in juvenile wood than mature wood. (b) greater in mature wood than juvenile wood. (c) relatively uniform within a species.
A -greater in juvenile wood than mature wood.
Zinc is an appropriate sacrificial anode for steel because it: (a) has a higher electrode potential. (b) has a lower electrode potential. (c) does not oxidize. (d) accelerates oxidation.
A -has a higher electrode potential.
Wood strength is most sensitive to variations in grain angle when it is loaded: (a) in tension parallel to the grain (b) in compression parallel to the grain
A -in tension parallel to the grain
Creep and Shrinkage in concrete are similar in that both are a function of: (a) moisture movement in the gel pores. (b) moisture content of the concrete. (c) applied load. (d) capillary porosity.
A -moisture movement in the gel pores.
Which of the following is NOT a phase of steel: (a) stalite (b) pearlite (c) cementite (d) ferrite
A -stalite
Steel has a higher elastic modulus than aluminum. If identical bars of aluminum and steel are subjected to the same stress, which will deform more? (a) the aluminum bar (b) the steel bar (c) they will deform the same (d) can not tell from information given
A -the aluminum bar
ABSORPTION CAPACITY
AC = ((Wssd)-(Wod))/(Wod) (x100%)
Pavements
ACC is weak, but it is effective at holding aggregates in proper position. - only a few inches thick - primary load carrying ability comes from sub-base - base helps to disperse load (*ACC more common in ME)
Resiliance
Ability to bounce back (area under stress-strain curve
In an economically proportioned concrete mix, the most abundant constituent is:
Aggregate
An aggregate sample with a moisture content of 1.1% and an absorption capacity of 1.3% is:
Air Dry
All metals have an electrode potential
Anode is always the higher side (will rust) than the cathode side. (*zinc has a higher electrode potential so when attached to Fe it will oxidize/rust over the iron)
Thermal stresses
Arise when material wants to expand/contact, BUT CAN'T
In an economically proportioned concrete mix, the most abundant constituent is: (a) portland cement (b) aggregate (c) water (d) fly ash
B -aggregate
Which of the following is generally NOT a typical advantage of a wood composite: (a) better resource utilization (b) better decay resistance (c) better strength (d) better dimensional stability
B -better decay resistance
Each of the following may be considered a toughening mechanism except: (a) crack blunting (b) crack surface energy (c) crack bridging (d) none of the above are toughening mechanisms
B -crack surface energy
Which of the following clear wood failure mechanisms is the weakest? (a) fiber rupture (b) fiber separation (c) fiber buckling (d) fiber crushing
B -fiber separation
All of the following are standard cement types EXCEPT: (a) high early strength (b) high freeze-thaw resistance (c) low heat of hydration (d) moderate sulfate resistance
B -high freeze-thaw resistance
The nonlinear stress-strain curve observed in concrete is primarily due to: (a) the nonlinear stress-strain curves for cement paste and aggregate. (b) interface cracking between the cement paste and the aggregate. (c) creep. (d) the rule of mixtures.
B -interface cracking between the cement paste and the aggregate.
Wood is an anisotropic material because: (a) its properties vary depending from point to point within the material. (b) its properties vary depending on the orientation of the specimen. (c) its properties have very large standard deviations. (d) it is heterogeneous.
B -its properties vary depending on the orientation of the specimen.
Flaking occurs in steel when: (a) the oxide layer takes up less volume than the base metal. (b) the oxide layer takes up more volume than the base metal. (c) the oxide layer takes up the same volume as the oxide layer.
B -the oxide layer takes up more volume than the base metal.
While doing a test for bulk specific gravity, we prepare an aggregate sample that weighs 473 g in air and 292 g immersed in water. The bulk specific gravity is:
BSG = ((Wsolids)/(Vsolids)) * ((1)/(pH20)) = (473) / (181) = 2.61
Bulk Specific Gravity (BSG)
BSG = ((Wt agg)/(Vol agg)) * ((1)/(pH20))
If 7.20 ft^3 of fine aggregate is required to fill out a cubic yard of concrete mix, what is the weight required?
BSG = W/V (1/(pH20)) => W = BSG(V)(pH20) W = (2.6)(7.2)(62.4) = 1168 lbs
Engineered Wood Composites
Glulam Plywood (thin veneer peeled off of tree) - orient the grain in different directions, to prevent splitting Oriented Strand Board (made from flakes of wood) Laminated Veneer Lumber - plywood type beam, made of veneer Parallel Strand Lumber (PSL) - oriented strand board type beam, made of flakes (*LVL is to Plywood as PSL is to OSD)
Fatigue
Gradually reduction in strength due to repeated loading.
Ductile Material
Show extensive plastic deformation prior to rupture.
Concrete Hydration Reaction
Stage I- inital hydrolysis -dissolution of Ca & OH ions -no reaction products Stage II- induction period -reaction appear dormant -no reaction products Stage III- initial formation of reaction products -CSH forms on surface of cement grain -CH precipitates out of solution Stage IV- continued formation of hydration products -reaction slows -SCH forms a barrier that inhibits further reaction (kind of blocking C3S) Stage V- steady state hydration
Two types of steels (A & B) are being considered for a particular component. After extensive sample testing, the tensile capacity of steel A was found to have a coefficient of variation nearly twice that of steel B. In designing the component, which steel (A or B) should be assigned a higher factor of safety? Why?
Steel A should be assigned a higher factor of safety because the material has a bigger variability spread.
Strain: deformation per unit length [put on x-axis]
Strain = (deformation) / (length) (* dimensionless)
What is the shrinkage strain in the radial direction of a 2in. by 6in. by 12ft. quarter sawn board if after drying the dimensions are 1.90in. by 5.90in by 11.92ft.?
Strain = deformation / length = (6in. - 5.90in) / (6in.) = 0.0167
In the previous problem, what is the stress induced if the board is completely restrained from shrinkage in the longitudinal direction, and it is subjected to a shrinkage strain of .002 in that direction? The elastic moduli for the wood are as follows: EL=1,500,000 psi, ER=160,000 psi, and ET=150,000 psi. What is the shrinkage strain in the longitudinal direction of a 2 in. by 4 in. by 10ft. quarter sawn board if after drying the dimensions are 1.97 in. by 3.96 in. by 9.93 ft? => strain = 0.007
Stress = (elastic modulus) * (strain) = (.002) * (1,500,000) = 3000 psi
An S/N (stress over # of cylces) curve can be used to estimate the endurance limit.
TRUE.
Composite materials are always heterogeneous.
TRUE.
Dislocations are responsible for facilitating plastic deformation in crystalline materials.
TRUE.
Edge knots tend to reduce the wood strength more than equivalently sized center knots.
TRUE.
Elastic modulus is part of a material's constitutive relationship.
TRUE.
Fiber-matrix debonding leads to a reduction in material stiffness.
TRUE.
Glass fibers are much stronger than pane glass because the fibers tend to have fewer or smaller defects.
TRUE.
In structural design, a lifeline bridge gets a higher factor of safety than a small road serving a wood lot.
TRUE.
The density of the cell wall material is essentially the same among all wood species.
TRUE.
The effect of knots on wood strength is difficult to predict.
TRUE.
The greater the uncertainty in our design, the larger the factor of safety that should be applied.
TRUE.
Wood that has a higher proportion of latewood generally exhibits better structural properties than wood that has a higher proportion of earlywood.
TRUE.
High strength/low alloy steel has a lower stiffness than A-36 carbon steel.
TRUE. (*stiffness is the same)
All plastic deformations are inelastic.
TRUE. *but all inelastic objects are NOT plastic.
Carbon fiber has a higher elastic modulus than steel. If identically sized bars of carbon fiber and steel are subjected to the same strain, which will deform more?
They will deform the same. * if subjected to higher stress, steel would deform more
If MC > AC have excess H20 If MC < AC have H20 deficit If MC = AC agg is SSD (no excess or deficit H20)
This will effect strength & durability
PORTLAND CEMENT result compounds
Tricalcium Silicate --> C3S Dicalcium Silicate --> C2S Tricalcium Aluminate --> C3A Tetracalcium Alumino Ferrite --> C4AF C3S= greatest contribution to strength relatively fast reaction C2S= high contribution to strength relatively slow reaction C3A= low strength, very fast reaction (Gypsum added to avoid "flash set")
ASTM Cement Types
Type I: Normal; general purpose Type II: Moderate sulfate resistance (commonly used in ME) Type III: High early strength Type IV: Low heat of hydration Type V: High sulfate resistance (commonly used along coast of ME)
What is the dry-rodded unit weight of the aggregate of the previous problem? A 5 gallon (0.668 ft^3) bucket of contains dry-rodded coarse aggregate. If the aggregate sample weighs 70lbs, and the BSG is 2.60, what is the volume displaced by the aggregate particles only: 0.43 ft^3
UW = (W) / (V) = (70) / (0.668) = 105 lb/ft^3 (* use total volume, NOT the volume of particles)
UNIT WEIGHT (dry rodded unit weight ~ compacted)
UW = (Wagg) / (Vol agg)
A concrete mix calls for an air content of 6.0%. If the cement, water, and aggregates all add up to a volume of 2.707ft^3, and wight total of 404.7lbs, what is the unit weight of the concrete mix with air?
UW = W/V V = (2.707)/(1-0.06) = 2.88 UW = (404.7)/(2.88) = 140.5 lbs/ft^3
STEEL (carbon content) (an alloy of iron + carbon)
Wrought Iron ~ 100% iron -dense, less strong but more ductile Cast Iron ~ 2-5% carbon (but mostly iron) -->brittle Steel- in between typically ~ .2-.4% (*elastic modulus does NOT change with reduction process)
Smelting of iron is
a reduction process
In a wet corrosion process, oxidation takes places at the
anode
CONCRETE does not equal CEMENT
concrete does not dry strong, the chemical reaction makes it strong.
The cement hydration reaction is:
exothermic
A rational materials selection process will typically
first consider intrinsic properties, then attributed properties.
The term "free water" in wood refers to water
in the lumen
Statistical analysis techniques allow us to
make prediction of a population based on measurement of a limited number of samples.
Composite Structure
material made up of distinct phases.
Polymeric Structure
material made up of very long twisted/tangled molecules.
Amorphous
no clearly defined structure. No plastic deformation in amorphous materials (i.e. brittle) => no inelastic mechanisms
Oven Dry
no moisture in aggregate
Wet
pores are full, surface is wet
Saturated Surface Dry
pores full of moisture, surface dry
Surface Energy
potential energy associated with surfaces. Surfaces have the capacity to do work => which is why they have surface energies During fracture STRAIN energy IS CONVERTED to SURFACE energy.
Air Dry
some moisture in pores
What is the shrinkage strain in the longitudinal direction of a 2 in. by 4 in. by 10ft. quarter sawn board if after drying the dimensions are 1.97 in. by 3.96 in. by 9.93 ft?
strain = (deformation) / (length) = (.07) / (10) = 0.007
A 3 meter long rod is subjected to a stress that causes a uniform axial strain of 0.0004. What is the overall change in bar length due to that stress?
strain = (deformation) / (length) so, deformation = (strain) * (length) = (0.0004) * (3m) = 0.00012 m = 1.2 mm
You need to size a column that must carry 100,000 pounds. The maximum stress that can be allowed in the material used for the column is 1500 psi. What is the minimum required cross-sectional area?
stress = (load) / (area) 1500 = (100,000) / (A) => A= (100,000) / (1500) = 66.67 in^2
Strength
stress at failure
You need to size a bar that must carry 50,000 pounds. The maximum stress that can be allowed in the material used for the bar is 15,000 psi. What is the minimum required cross-sectional area?
stress=length/area => area=length/stress = (50,000) / (15,000) = 3.33 in^2
The heat affected zone in a welded joint refers to:
the area where material properties are changed by welding.
The "weak link" in concrete strength is typically
the cement-aggregate interface.
Crystalline Structure
very clearly defined atomic structure.
When we deform an elastic material, we change its potential energy because
we have changed its capacity to do work.
Steel stiffness
~ 8-9x more stiff than concrete ~ 15x stiffer than wood
Why Wood Composites?
- Better properties - mechanical properties - dimensional stability - More shapes/sizes variability - Efficient use of resources
Primary Phases of Steel
- Ferrite= nearly pure iron. soft, ductile - Cementile (or Iron carbide, Fe3C)= hard brittle material - Pearlite= 2 phased: ferrite & cementite - Austenite= solid solution of Fe + C - Martinsite-Austinite that has been rapidly cooled (quenched)
Durability of Wood
- Oxygen - Warmth (~20C-35C) - Moisture (Below 20% MC)
Asphalt Cement Concrete
- Petroleum based - VERY sensitive to TEMP. - Viscoelastic (returns to original state [time dependent]) - Brittle when very cold - PROPERTIES ARE VERY TEMP. DEPENDENT
Hot Mixes (used when paving)
- heat up at batch plant to melting, mix with aggregate - material hardens as it cools
Which of the following is likely to have the highest strength-to-weight ratio:
Carbon fiber composite
In order for the rule of mixtures to be valid, the composite material must have: (a) a stiff matrix relative to the fibers. (b) a small representative volume element. (c) an anisotropic matrix. (d) a good bond between the fibers and the matrix.
D -a good bond between the fibers and the matrix.
All of the following are advantages of FRP composites EXCEPT: (a) strength to weight ratio (b) corrosion resistance (c) chemical resistance (d) cost
D -cost
Quenching of steel is typically done to: (a) increase strength (b) increase stiffness (c) reduce residual thermal stresses (d) lock in a particular microstructure that would not appear at lower temperatures.
D -lock in a particular microstructure that would not appear at lower temperatures.
All other things being equal, as water-cement ration decreases: (a) strength decreases (b) durability decreases (c) rate of hydration reaction increases (d) strength increases
D -strength increases
Where do we find the microfibrils that most affect wood structural properties? (a) the lumen (b) the middle lamella (c) the primary cell wall (d) the secondary cell wall
D -the secondary cell wall (* S2 layer)
Which of the following does NOT affect the ultimate strength of a material: (a) specific surface energy (b) elastic modulus (c) inter-atomic spacing (d) yield strength
D -yield strength
Attributed Properties (selection & design)
Different from person to person - price/availability - ease of use - aesthetic properties
What is the elastic modulus of a unidirectional FRP composite with 55% carbon fiber (Ef = 230GPa) in an epoxy matrix? (Em = 41GPa)?
Ec = EfVf + EmVm = (230)(0.55) + (41)(1-0.55) = 145GPa
Elastic vs Proportional Limit
Elastic - stress at which material is no longer elastic Proportional - stress at which material is no longer linear.
Which of the following may be considered an intrinsic property of a material:
Endurance Limit
Toughness
Energy absorption capacity of material. (area under stress-strain curve = modulus of toughness)
Concrete Air
Entrained air- improves workability Entrapped air- is bad, weakens mix. Big bubbles in mix
Shrinkage is direction dependent (i.e. L vs R vs T)
Et > Er >> El
Factor of Safety (F.S.)
F.S. = (strength of material) / (max expected load) = (capacity of system) / (max expected load)
A higher strength material will always have a higher modulus of toughness.
FALSE.
A thermoset polymer can be melted and reshaped.
FALSE.
Aggregate moisture content is always greater than absorption capacity.
FALSE.
By removing defects from materials we can make them more ductile.
FALSE.
Composite materials are always anisotropic.
FALSE.
During fracture surface energy is converted to strain energy.
FALSE.
Entrained air is added to concrete to improve strength.
FALSE.
Given two grades of steel, the material with the higher strength will always have a higher toughness.
FALSE.
In mix design, we use the water-cement ratio required for strength or durability, which ever is greater.
FALSE.
Sulfate attack in concrete results from reactive aggregates.
FALSE.
The cement hydration reaction typically completes itself within 28 days.
FALSE.
The heat of a reaction of portland cement concrete is roughly constant for the first 24 hours, after which it cools as hydration slows.
FALSE.
The proportional limit and the elastic limit are always the same stress.
FALSE.
Under normal conditions, steel embedded in concrete will oxidize after several years.
FALSE.
We typically use ACC for pavements rather than PCC because ACC generally lasts longer.
FALSE.
Iron is extracted from ore by melting the raw material.
FALSE. (*need to do a reduction reaction)
The proportional limit and the elastic limit are always the same stress.
False
When loaded in radial tension, wood will fail due to
Fiber Separation
Crack Bridging
Fibers in material hold it together.
Concrete Admixtures
Fly ash Silica Fume Slag (* all waste products, pozzolans) Pozzolans - improve strength & durability
Elastic Behavior
Get elastic behavior when there is no other energy conversion. All work goes into elastic deformation. so, since reversible. When unloaded, material seeks lowest energy state. The material is seeking its lowest energy state and there is no other energy conversions taking place.
What is the most representative measure of the center of a sample, if there are one or two anomalous outliers?
Median
Crack tip blunting (toughening mechanism)
Plastic deformation increases tip radius (so stress intensity goes down)
Asphalt Concrete vs. Portland Concrete
Portland Concrete: would rather have aggs no touch Asphalt Concrete: particle to particle contacts (strength mechanism)
Strain Energy
Potential energy associate with elastic deformations. (area under curve, before yield so entirely elastic) Strain Energy Density- area under stress-strain curve
Pozzolanic Admixtures
Pozzolanic reaction leads to more CSH formation and less CH formation => denser structure => higher strength => improved durability Other effects: => slow hydration => with silica fume, in particular, hurts workability =>fly ash MAY help workability
Welding (Heat affected zone)
Region around weld where properties have changed due to re-heating [typically weak link]. (*arc welding most common for steel)
A concrete mix calls for an air content of 5.5%. If the cement, water, and aggregates add up to a volume of 4.36 cubic feet, and weigh a total of 647 lbs, what is the unit weight of the concrete mix with air? (a) 149 lbs/ft^3 (b) 147 lbs/ft^3 (c) 140 lbs/ft^3 (d) 136 lbs/ft^3 (e) none of the above
C - 140 lbs/ft^3 UW = (Wt) / (vol) = (647) / (4.61) = 140 (* Vol= (4.36) / (0.945) = 4.61)
In fatigue loading, if the stress range decreases: (a) the endurance limit decreases (b) the probability of rupture increases (c) the number of cycles to failure increases (d) the number of cycles to failure decreases
C - the number of cycles to failure increases
A material with a high toughness is: (a) also high strength (b) also high stiffness (c) able to absorb a high amount of energy prior to rupture (d) none of the above
C -able to absorb a high amount of energy prior to rupture
All of the following are examples of concrete admixtures except: (a) fly ash (b) accelerators (c) fibers (d) shrinkage reducers
C -accelerators
An aggregate was found to have a moisture content of 0.5%, and an absorption capacity of 1.5%. The aggregate sample may be considered: (a) wet (b) saturated surface dry (c) air dry (d) oven dry
C -air dry (* MC would be 0 if oven dry)
The strength of real materials does not reach the theoretical strength due to: (a) poor atomic bonding (b) anisotropy (c) defects (d) cross linking
C -defects
All of the following knot issues lead to a reduction in wood strength except: (a) stress concentrations (b) holes caused by dead knots (c) densification of wood around the knots (d) deviation of grain angle
C -densification of wood around the knots
In order to produce high strength concrete, we must: (a) accelerate curing. (b) minimize the effect of moisture movement in the gel pores. (c) improve the cement-aggregate interface. (d) use aggregates with high BSG.
C -improve the cement-aggregate interface.
Alkali-silica reaction occurs in concrete: (a) exposed to groundwater. (b) exposed to freeze-thaw cycles. (c) made up of reactive aggregate. (d) that has a high concentration of chloride ions.
C -made up of reactive aggregate.
In order for fungi to be able to cause wood rot, which of the following is necessary: (a) light (b) a moisture content below 20% (c) temperature above 20C (d) carbon dioxide
C -temperature above 20C
What is the advantage of coefficient of variation over other measures of sample distribution?
COV is unit less, so it allows the comparison of measurements with different units.
Intrinsic Properties (selection & design)
Can be measured ~ same for everyone - mechanical properties - physical properties - surface properties
Smelting
Iron Extraction is a chemical reduction process [pure iron is not found in elemental state] A lot of CO2 as byproduct, so high pollution production
PORTLAND CEMENT constituents
Lime (CaO) Silica (SiO2) Alumina (Al2O3) Ferric Oxide (Fe2O3) (* can get all of these from Limestone & Clay)
Brittle Material
Little or no plastic deformation prior to rupture.
High stress ~ High load High stress ~ Low cycles
Low stress ~ High cross-sectional area High strength ~ Low toughness
The S2 layer microfibril angle in mature wood tends to be:
Lower than juvenile wood.
MOISTURE CONTENT
MC = ((Wagg)-(Wod))/(Wod) (x100%)
What two pieces of information are required to apply a normal distribution to a population?
The mean and the Standard deviation.
Tightly spaced growth rings in wood are generally more desirable than widely spaced rings because:
The wood tends to be denser and therefore stronger.
A 5 gallon (0.668 ft^3) bucket of contains dry-rodded coarse aggregate. If the aggregate sample weighs 70lbs, and the BSG is 2.60, what is the volume displaced by the aggregate particles only:
V = ((W)/(BSG)) * ((1)/(pH20)) = ((70)/(2.6)) * ((1)/(62.4)) = 0.43 ft^3
A partially completed mix design calls for (per cubic yard of mix) 4.70ft^3 of water, 3.90ft^3 of cement, and 10.80ft^3 of coarse aggregate (solids only). What is the volume of dry fine aggregate (solids only) required to complete the mix? The required air content is 5.5%.
Vfa= 27 - 4.70 - 3.90 - 10.80 - 0.055(27) = 6.115ft^3
Water to Cement Ratio
W/C = (Wt Water) / (Wt Cement) High w/c, High pore space, Low strength