CE Materials Final
Make a sketch of the fracture surface you would expect to occur for a metal tat suffered a moderately ductile type of fracture
"cup and cone"
What is the relative temperature that is commonly applied in the annealing of work-hardening steel?
.6Tm
What is the maximum amount of Silica Fume that is used in concrete?
10%
TF: According to ASTM C-33, the fineness modulus of fine aggregate must be between 2.1 and 3.3
2.3 and 3.1
What size of US standard sieve is used to separate fine aggregate from fines?
200
What is the minimal amount of time that a concrete structural element made with ggb slag as SCM in the concrete mix must be kept moist to insure proper curing and strength gain?
21 days
What is the modulus of elasticity of steel at room temperature?
29*10^6 psi
What is the value of the modulus of elasticity of steel?
29*10^6 psi
What is the normal amount of time that a concrete structural element made with normal concrete must be kept moist to insure proper curing and strength gain?
7 days
At what temperature does this change in solid iron occur?
910C
What types of cement (1-5) are need to: A. Be high early strength? B. Give low heat of hydration?
A. 3 B. 4
What is the formal ASTM designation for steel used today to make structural steel in hot-rolled shaped?
A992
What are the 4 different elements (periodic table) that the earth materials provide, that are combined in the kiln ans burned together in the process of making Portland Cement?
Al, Ca, Si, and Fe
What is the name of the behavior where in hot solid iron changes its atomic structure when cooled?
Allotroph
Besides silica, what other metallic element is a primary component of most ceramics?
Aluminum
List the three main components of bitumen
Asphaltenes, resines, and oils
What type of stainless steel can be welded?
Austenitic
What are four different properties that are necessary for steel rebar to have?
Bendable, weldable, high strength, and resistance to corrosion
What is the one cmpd in Portland Cement that is primarily responsible for long-term strength gain of concrete?
C2S
List the initials of the 4 different compds that exist in each grain of Portland Cement
C2S, C3S, C3A, and C4AF
Which one of the 4 cmpds in Portland Cement grains must be kept to a very low percentage to make the cement resistant to sulfate attack?
C3A
Write the equation for the carbonation reaction that occurs in concrete exposed to the atmosphere
CO2 + Ca(OH)2 -> CaCO3 + H2O
When Portland cement and water are mixed together, what is formed that gives concrete its strength?
CSH
List the four different sources of drying concrete shrinkage
Capillary tension, interlayer water, disjoining, and surface energy
Cast iron products are more brittle than steel because cast iron contains much greater carbon content that often forms hard Fe3C during the slow cooling of the iron. What are the two different names of Fe3C
Cementite and iron carbite
What are the three different types of mineral aggregates that are used in making asphalt concrete for paving?
Coarse agg, Fine agg, and fillers
Explain the fundamental reason why aluminum should not be imbedded in comcrete
Concrete has a higher pH than aluminum so it will corrode the aluminum
What is the primary reason that rebar is at high risk of corrosion when concrete has suffered carbonation?
Concrete's pH decreases from >12 to 9/8 so the rebar steel is no longer protected
What type of bond exists between the carbon atoms in a long polymer chain that makes the chain very strong in the line of the chain?
Covalent
Which type of atomic bonding occurs when one atom "shares" one or more electrons from another atom of the same element?
Covalent
What are the names of the four different types of bonds between the atoms?
Covalent, Ionic, Metallic, and Van der Waal
What is the principle metal alloy in stainless steel?
Cr
What metal alloy is in self-weathering steel?
Cu
What are the 4 different methods that are commonly used to keep concrete moist while it is curing?
Curing membrane, windbreakers and sunshades, polythene sheets, and spraying with water
There are three different types of asphalt. How is each softened for making pavement asphalt: Cutback, Penetration Grade, and Emulsion?
Cutback- solvent Penetration Grade - Heat Emulsion - water and emulsifier
Describe the one physical condition in metals that makes the actual tensile strength be only about 10% of the theoretical atomic structure that would be calculated based on the interatomic force attraction and repulsion
Defects in atomic structure
What are the names of the 4 major types of glass fibers used in FRP?
E-glass, A-glass, Z-glass and S2-glass
What is the atomic structure of Aluminum?
FCC
T/F: A characteristic of all metals is that all metals have an endurance level for cycled loadings, below which repeated loadings will not cause metal failure even after a many millions of load cycles
False
TF. An asphalt pavement in Texas on a hot summer day can have a stiffness modulus that is 100 times smaller (softer) than would a similar asphalt pavement on a cold cloudy day in Chicago in the winter
False
TF: Alkali-silica reaction occurs when the silica of the concrete's CSH reacts with certain alkaline materials in bedrock that is crushed for coarse aggregate
False
TF: Calcium chloride is often used as an accelerating agent to speed up concrete setting, and is effective in reinforced concrete because it greatly improves the bond of the concrete to the reinforcing steel bars
False
TF: Creep limit stress level for concrete is 40% of f'c
False
TF: Polymers that are used in FRP that are thermo-plastic are greatly affected by changes in temperature, so their in-service condition should always be temperatures above the Tg so the FRP is not brittle
False
TF: The rapid cooling of melted metal that forms from welding causes large grains of Fe3C to form which makes the weld very strong but very brittle
False
TF: The slump of fresh concrete is always measured because it indicated directly if concrete has both proper w/c and workability
False
TF: Type IV cement should be used to make concrete that can resist sulfate attack when the concrete will be embedded in sulfate rich soil
False
TF: When a steel beam is thoroughly heated to 850F, it would be expected to have lost more than 50% of its yield strength
False
TF: When aggregate is at a water content greater than its SSD condition, then the amount of water that is put into the concrete mix must be increased to maintain proper w/c ratio
False
TF: When limestone coarse aggregate is used in concrete, that concrete can experience rapid loss of strength when its temperature exceeds 450C, and this is due to the large difference in thermal expansion between HCP and the limestone aggregate
False
TF: When the viscosity value of a liquid asphalt goes down, the Marshall test strength parameter would also be expected to go down
False
TF: heating an FRP from a temperature much below its Tg, to a temperature a little below the Tg will change the FRP from a brittle material to one that is pliable and stretchablr
False
TF: In the process of ageing, the aluminum is reheated to a temperature of about 250C to cause very small particles of CuAl2 to coalesce and cluster together, which substantially improves the strength of aluminum and its ductility
False,
TF: The penetration test is performed by measuring the depth that the needle will penetrate a small cup of asphalt in 5 seconds under the weight of 100 grams, when the asphalt is at 77F
False, 5 seconds under the weight of 150 grams at 25F
TF: To resist the effect of many cycles of freeze-thaw that occur every winter season, air entraining agents must be used in concrete that will be outside through its life, and in eastern MA there should be about 4% air in concrete
False, 5%
TF: Class C Flyash has more silica but less calcium than does Class F Flyash, so Class C can be used in greater % cement replacement than can Class F
False, Class C has more Calcium
TF: Pearlite is the name given to the material formed of lamellae of Fe3C and austenite, the lamellae being nearly parallel in a laminated structure withing grains of steel that is at room temperature
False, Pearlite is formed from ferrite and Fe3C
TF: When bitumen oxidizes as it ages, oxygen molecules combine with the aromatics and resins to form asphaltenes which have a higher molecular weight and are harder than resins and oils, which makes bitumen harder and more resistant to cracking
False, it increases the viscosity of the bitumen
TF: When a simply-supported rectangular concrete beam is being reinforced with FRP to improve the beam's ability to carry bending moment, the fibers in the FRP used for the strengthening should be isotropic and should be placed along the bottom of the beam and oriented parallet to the long axis of the beam
False, it should be orientated perpendicular to the long axis of the beam
TF: In the SuperPave system, the PG that is used to designate the specific asphalt binder needed to make an asphalt concrete for paving a highway stands for PavementGrade
False, it stands for Performance Grade
TF: When a pure metal is cooled slowly from the liquid state, it will develop large crystal grain structure, and this will provide rather high yield stress and low brittleness
False, it will provide low yield stress and low brittleness (high ductility)
TF: Asphalt pavement will suffer less deformation cracking when the temperature of the pavement is cold in the winter months, because the asphalt is stiffer and more capable of acting like a stiff beam under wheel loads
False, it will suffer more deformation cracking when the temperature of the pavement is elevated in the summer months, because the asphalt is softer and more readily deflects
TF: Flyash is the most effective SCM for reducing concrete permeability
False, microsilica
TF: In the marshall test, the flow number is the maximum load that the asphalt sample supports in the test, and the stability is the deformation
False, the stability is the maximum load that the asphalt sample supports in the test, ans the flow is the deformation
TF: Water reducing agents act to make concrete very fluid with less water, thus improving workability, but this will cause the concrete to take much longer to achieve its initial set and delays strength development
False, they act to initially neutralize the electro-static charges on cement grains and cause the cement grains to become negatively charged so they repel each other and float freely and separately in mixing water, giving concrete better workability
TF: Brazing and soldering are very different processes; in brazing very hot temperatures are used to melt the members and join them by solidified melted metal, but soldering is using a different metal to join two other types of metal
False, they are very similar, soldering is joining two things together with different metals and brazing is doing the same except at a higher temp
TF: Cold-rolled steel products have an increase in strength from undergoing strain hardening, but they lose ductility and become brittle due to the intense squeezing of the grains of the original steel, but this problem does not occur in hot-rolling
False, this problem can occur in hot-rolling
T/F: The APF for BCC structure is 0.64 and the APF for FCC is 0.74
False; BCC is .68 and FCC is 0.74
TF: Surface tension is the basic physical characteristic of a liquid that causes the phenomenon if adsorption into a sand soil or paper towel
False; absorption goes with surface tension
T/F: When a metal cools from liquid state to solid, the atomic crystal structure grows from many nucleation points, and there crystal structures usually line up and overlap with one another to form into only a few large, uniformly oriented metal crystals
False; but when the cooling happens quickly, the resulting crystal structure had only enough time to make a few very large grains
T/F: In ceramic materials such as concrete, the primary type of bonding that holds the atoms together is ionic bonding?
False; covalent
TF: Steel corrosion occurs in a wet environment when electrons of iron are conducted through the steel to a places where they are consumed in a reaction with oxygen to form iron oxide ions, known as ferrous-oxide in the electron-depleted metal, and then further reacts further with water oxygen to create the fully corroded ferrous-hydroxide
False; ferric-oxide
T/F: When a steel element in a structure fractures, it is developing cracks, but when the steel element fails, the cracks break through and the element separates into two pieces
False; fracture means it has broken and failure means that it doesn't perform as desired
TF: Iron at room temperature has a FCC structure
False; iron at room temperature has a BCC structure
T/F: Many polymers are thermo-setting, which means that they become softer when heated, and stiffer when cooled
False; many polymers are thermo-plastic
TF: Within a single grain of metal, there can be thousands of edge dislocations that move when shear stress is applied. But because grain boundaries block the dislocation movements, metal having big grains and few boundaries will make for stiffer, less ductile behavior, so metals with larger grains will be stiffer than the same metal with small grains
False; metals having more boundaries will make for stiffer, less ductile behavior, so metals with smaller grains will be stiffer than the same metal with large grains
TF: The reason that metals expand when they are heated is that the added energy causes the nucleus of each atom to expand which causes atoms to vibrate and expand which causes the entire array of atoms to expand
False; the added energy causes the orbit of the electrons about the nucleus of each atom to expand which causes atoms to vibrate more which forces the entire atomic structure to expand
What is the name given to the phenomenon of an asphalt pavement suffering cracking failure after incurring several million load repetitions of heavy trucks?
Fatigue failure
What are the names of the 3 different types of stainless steel?
Ferritic, Martensite, and Austenitic
What are the two of the three primary ways that a concrete mix can be made to resist ASR when you must use aggregate that contains active silica?
Flyash and low alkali cement
What is the effect of each of the three primary SCMs used in the US on the workability of a concrete mixture
Flyash: increases, GGB Slag: increase or no change, and silica fume decreases
List the 2 principle failure modes that occur in a highway asphalt pavement?
Functional failure and structural deterioration (cracks)
What two types of fibers in FRP will suffer deterioration in moist and alkaline environments?
Glass and aramid
What does Tg stand for?
Glass transition temp
List the common names of the four different types of cast iron
Grey, white, malleable and spherical
What are the two elements that make up the greatest percentage of polymers?
H and C
What part of the asphalt making and paving process is the rolling thin film oven test used to replicate?
Heating to high degree and mixing in asphalt
Describe two ways that you can minimize the Alkali-Silica Reaction in a concrete of the only coarse aggregate that you have to use is an ASR reactive aggregate
Increase flyash and limit Alkali
List the 2 principle major benefits of using fibers in the polymer matrix material
Increase strength and increase stiffness
What is true about the effect of "strain, or work hardening" of a metal?
Increases strength, decreases ductility, and increases brittleness
What is the name used to identify a FRP that has the same strength and stiffness in all directions?
Isotropic
Explain one fundamental thing that air entraining agent does to make concrete resistant to the otherwise damaging effects of winter freeze-thaw
It creates tiny bubbles that allow the water to disperse into so it reduces the pressure that would cause the cement to crack
Describe how super-plasticizer acts in a concrete mix to greatly improve fluidity
It decreases the amount of water because when it is mixed with water the particles coalese into flocks that trap in water; this increase the strength and improves fluidity
When bleed water from fresh concrete encounters horizontal rebar as the water migrates up to the surface of freshly placed concrete, what major problem may develop?
It decreases the bond to the rebar
Describe how the ASR reaction in concrete causes damage to concrete
It forms a gel that destroys bond btwn HCP and aggregate and causes cracks
What is the primary performance reason that chert is not a good material to have in the coarse aggregate used to make concrete for the exterior of a building?
It has voids which causes popouts
What is the primary reason that the amount of Fe3C in structural steel must be kept to a very low percentage?
It makes the material brittle
What is the one big problem with HAZ, and why does it occur?
It makes the material brittle because it is heated up to change to FCC but is not high enough to reach its melting point and it cools rapidly so its structure can not go back to BCC. It occurs because the areas around it are getting heated to its melting point
What problem can be prevented by the proper design of welds required for building up weld material used to join together thick steel plate pieces?
Lamellae tearing
What is the one primary earth material needed and used in manufacturing cement?
Limestone
In making self-compacting concrete, what are the 3 very essential ingredients that must be included?
Low w/c, less coarse aggregate, super plasticizer
What are the 4 component changes needed in making concrete that will last a long time throughout its service life?
Low w/c, wet and cold environment, Calcium silicate, and sulfate ions
In using the electromotive series to select a sacrificial metal to protect another metal, the metal to be protected should have HIGHER OR LOWER electromotive value than the sacrificial metal
Lower
What type of cast iron is most ductile?
Malleable
When steel is heated and then rolled to make it into rebar, what is the name of the steel that forms at the rebar surface as a result of the water spray quenching process?
Martensite
Explain why it is much easier for heat to be transferred through metals than through ceramic materials
Metals have metallic bonds which are more conductive which ceramics have covalent and ionic bonds
In the US, the beam test is typically used to determine the flexural tension strength of concrete. What is the name of the property that is determined, according to the US concrete design practice?
Modulus of Rupture
List the 5 environmental factors that cause degradation of FRP materials
Moisture, Thermal effect, corrosion, fire and UV radiation
Describe what is the most important precaution that must be followed when fastening aluminum parts together with steel bolts and rivets
Must isolate from each other
List the 4 different way to treat hot-worked steel to relieve effects of hot-working
Normalize, normalized-rolled, thermomechanical, and quenched and tempered
What are the names of the two different types of carbon fibers made for use in FRP?
Pan and Pitch
Explain what pearlite is, and how it is formed
Pearlite is laminate and cemenite and is formed when steel gets slowly cooled from austenite
Which carbon fiber is most often used in civil engineering construction
Pitch
What are the three different sub-divisions of creep deformations?
Primary, secondary, and tertiary
What is the name of the commonly used process to make wide flange beams and other structural member from FRP?
Pultrusion
List the four different ways that bleeding of concrete can be effectively reduced
Reduce w/c, increase temp, superplasticers and AEA
What is viscosity a measure of?
Resistance to shear stress
List the names of the 6 different lab tests that are done in the SuperPave PG asphalt grading system
Rolling thin-film oven, pressure-aging vessel, flash point, sustainabillity, dynamic shear rheometer, rotational viscometer, solubility
Describe what are the two major disadvantages that arise from working metals like steel by the hot working process
Shrinkage and surface resistance
What is the one element that all Supplemental Cementitious Materials contain, that makes them valuable as replacement for some of the Portland Cement in concrete mixes?
Silica
What is another way to speed up the hydration of cement, other than altering the relative amounts of the four primary cmpds?
Smaller grains
List the three fundamental mechanisms by which water and chemicals penetrate into concrete
Sorption, permeability and diffusion
List the 2 of the 3 primary functions of the top-most layer of an asphalt pavement
Stability and Withstand abrasions
List the following information for each stage of cracking development in concrete
Stage 1: 0-30%, transition zone, little stable cracks Stage 2: 30-50%, transition zone, cracks grow but still stable Stage 3: 50-70%, matrix, unstable cracks Stage 4: 70-100%, matrix, max strain and unstable crack growth
When red-hot steel is quenched, what is the result in terms of ductility and strength?
Strength is high and ductility is low
Creep deformation also manifests itself as the physical cause for a material to slowly lose load when that material is loaded to a pre-determined strain and held at that strain, such as a torqued bolt. What is the name of this load reducing phenomenon?
Stress Relaxation
Explain the one reason why, on the atomic crystal basis, that when a metal experiences a small load in tension, it deforms elastically, has no plastic deformation and will return to its original length when load is removed
The edge dislocation didn't jump
What is the name if the method used to accelerate testing of new FRP materials to make sure that the new material will have acceptable performance over its full design life
Time-temp superposition principle
As the temperature of steel increases from -30C to +40C, what happens to the following properties: Toughness, yield stress, and ductility?
Toughness increases, Yield stress either no change or decreases, and ductility increases
T/F: A cylinder of concrete is really experiencing a form of tensile failure when loaded to failure under compression loading in the laboratory.
True
T/F: A steel bar used in a bridge would not be expected to eventually fail and break if permanently loaded to 62% of its ultimate strength
True
T/F: Nominal stress, which is also referred to as engineering stress, will be less than the "true stress" in a metal bar being loaded in tension.
True
T/F: One of the most frequent atomic structures in ceramic materials is the silica tetrahedron
True
T/F: The APF is the ratio of the volume of atoms in the unit cell divided by the volume of the unit cell
True
T/F: The term valence electron of an atom refers to only those electrons in the outer orbit of an atom that can be used to fill outer orbits of other atoms
True
T/F: When an iron rod is tested in tension, and the fracture surface shows no necking down and sharp fracture through the bar at a right angle to the applied load, this represents a very brittle material behavior
True
TF: A metal is considered to be ductile when it has toughness, from the Charpy test that is a value greater than 20 J
True
TF: Aggregates that are silica based such as granite and quartzite do not perform as well in asphalt as does carbonate rocks such as limestone because the asphalt does not adhere very good to silica minerals, but does not stick well to carbonate-rich limestone
True
TF: Air entrainment protects concrete from freeze-thaw deterioration by providing lots of air bubbles that are 1/100 the size of entrapped air voids, so the expansive force of freezing water is relieved by freezing water moving into the tiny voids
True
TF: Alloys are used in aluminum, because their inclusion increases the strength of aluminum by as much as 15 times greater than the strength of plain aluminum
True
TF: An elastomer will undergo elastic strain when a stress is applied, but it will recover all of the strain when the stress is removed, because such a polymer is made of long-chain molecules that are coiled and twisted and cross-linked so the molecules can not move irreversibly
True
TF: Both bolts and earlier used rivets have to have high strength, and low stress-relaxation, but they are both brittle and have low strain to failure
True
TF: HDPE is a thermo-plastic polymer
True
TF: Hot-working steel by rolling structural shapes at 1000C will cause great deformations in the grain structure, but this is generally relieved by leaving beams to cool naturally, which allows time for internal heat to anneal the grain structure
True
TF: In a plant that makes asphalt concrete for paving, the aggregates are heated thoroughly to both dry them out and give heat needed for the asphalt concrete mixture, and then finally sprayed with hot asphalt and mixed for several minutes
True
TF: In the SuperPave system, the asphalt binder used to make the asphalt concrete is designated by PG numbers that are based on the temperature range that the pavement is expected to experience throughout its life
True
TF: In the strain hardening of metals, a large number of dislocations are forced to move in the atomic structure, which results in plastic deformation of the metal and an increase in the proportional limit
True
TF: Metals that have BCC atomic structure will readily undergo plastic deformations in response to applied load, but those with HCP will not
True
TF: Silica fume particles are very small compared to cement grains, and fit in the tiny spaces between cement grains and react very fast, so that within 2-4 weeks of hydration, the silica fume action is completely finished
True
TF: Solid aluminum always has a FCC structure
True
TF: The maximum amount of ground blast furnace slag that is allowed by ACI for use as an SCM in concrete for structures is 40%
True
TF: The primary problem for concrete that suffers carbonation is that the pH of HCP is reduced when CO2 attacks the Portlandite and creates Ca(CO3) and H2O
True
TF: The transition zone around coarse aggregate is a very thin zone that had high W/C, is righ in Ca(OH)2 and Ettringite, and contains very little CSH
True
TF: The typical amount of old asphalt pavement that is used as recycled material in making new asphalt concrete usually averaged about 40%
True
TF: To achieve concrete that is very high strength, the mix must have: silica fume, low w/c, high cement content, and clean crushed stone for coarse aggregate
True
TF: Viscosity of a liquid decreases when temperature increases
True
TF: When a liquid has a low contact angle it will readily spread out over a large area
True
TF: When aggregate is at its SSD condition, the interior voids will be filled with water and the surface will be slightly damp
True
TF: When molten low-carbon (.2%) steel is cooled, austenite (having FCC structure) forms first, and on further cooling, the austenite structure changes into a mix of ferrite (that is FCC) and Fe3C
True
Explain why very high strength steel wire and cable used in construction is not tempered to return it to a ductile condition
You want the high strength steel wire and cable to keep its strength and not decrease its yield point
What type of glass fiber that is used in FRP is most often used because of its resistance to alkali?
Z-glass
In a typical sacrificial metal protection system, bars of what metal are buried in ground as sacrificial anodes and connected with wires to a buried steel pipelines to keep the steel from rusting away
Zinc
Define what a gel is
a liquid with lots of fine particles
List three different polymers that are thermo-setting
epoxy, polyester and vulcomned rubber
Write the names of the four different types of defects and impurities that occur in the crystal structure of metals, and which have large effects in determining the strength of metals
interstitial atoms, substitutional, vacancies, and edge dislocations
Explain the details of how silica fume acts to greatly reduce the permeability of concrete
it increases the amount of CSH in the transition zone and coarse aggregate which reduces permeability
Explain what is the primary benefit to the behavior of the eventual solid metal of including small amounts of an alloy element in the melted metal before making the casting
it will cause smaller grains which will increase the yield point
To achieve maximum fiber stress utilization in a polymer matrix, what is the maximum length that the fibers must have?
twice the engagement length
What is the name for the H2O molecules that react with the chemicals of cement grains to form hardened concrete gel known as Calcium Silicate Hydrate in which there molecules remain as H2O within the CSH molecular structure
water of crystallization
What are 3 of the primary reasons why excessive amounts of soil fines are very undesirable in concrete aggregate?
weakens HCP bonds, clumps up and reduces workability
