Materials Final Exam

list the three primary uses of aggregates in civil engineering applications

- base material in foundations and pavement - in Portland cement concrete - in asphalt concrete

list the three raw materials required to produce portland cement

- calcium oxide - gypsum - silica

list three advantages of using engineered wood products over standard sawn lumber

- customized shapes - efficient use of scrap materials - more consistent material properties - distributes defects - longer/bigger sizes/lengths

list the 5 steps required to produce steel

- obtain iron ore - refine iron ore - reduce iron ore to pig iron - refine pig iron to steel - form steel into products

list two common types of recycled aggregates used in civil engineering applications

- reclaimed (recycled) asphalt pavement (RAP) - recycled concrete aggregate - recycled glass aggregate

what three categories are used to classify the tabulated mechanical properties of wood such as tensile capacity, flexural capacity, etc. in the NDS?

- size classification - grade - species group

list 3 ways you could modify the mixture design or materials used to increase the modulus of elasticity of concrete

- use aggregates with higher E's - increase amount of aggregates used (volume fraction) - lower w:c ratio increase density increase compressive strength decrease porosity increase MC

if you are placing concrete in an environment where sulfates are present, what are three steps you can take to reduce the risk of sulfate attack?

- use cement low in C3A (type II or V) - use less cement - use SCMs - lower w:c ratio

which chemical componants of portland cement (C3A, C4AF, C3S, and C2S) correspond to the following statements 1. has hydration reactions that are affected by gypsum (sulfate) content 2. responsible for the majority of late strength gain 3. hydration reaction produces C-S-H

1. C3A, C4AF 2. C2S 3. C3S, C2S

mortar type applications type S type N type M

2nd story exterior load bearing wall 2nd story exterior non-load bearing wall; chimney basement wall (MaSoNwOrk) M: exterior, at/below grade S: exterior, above grade, load bearing N: exterior (above grade, non load bearing); interior (load bearing/partitions) O: restoration projects; interior - non load bearing walls

which aggregate would result in a more stable asphalt concrete, one with 60% of the particles having 1+ fractured face, or one with 80% of the particles having 1+ fractured face? why?

80% - more angular - more stable aggregate is aggregate with cubical and angular shape, and rough texture. flat and elongated particles are more prone to fracturing and less stable

provide the details below for the test that would be run on an asphalt binder to evaluate its resistance to fatigue cracking name of test: temp of test: binder used for testing:

DRS - dynamic shear rheometer intermediate RTFO + PAV

describe (not just list) the heat treatment process that would provide the greatest increase in strength for a typical steel

Hardening followed by tempering would provide the greatest increase in strength metal would be heated above austenite temperature, then quenched in water/oil --> results in a hard and brittle material following this with tempering would increase the ductility, resulting with a material that is strong, hard, and tough, but not as brittle

**wood calculations eqns

MC = (Wmoist-Wdry)/(Wdry) * 100 specific gravity G = Wdry/(Vwood @ x% MC * 62.4 lb/ft^3) Gm = Gb/(1-0.265((FSP-M)/FSP)Gb) Gb = basic SG in green condition (@FSP) Gm = SG @ moisture content M density = Gm(62.4lb/ft^3)(1+M/100) remember conversions!! quartersawn: curves vertical (R bottom, T side) plainsawn: curves horizontal (T bottom, R side) change in length - get radial and tangential shrinkage shrinkage from table for species linear interpolation to find shrinkage from FSP to MC multiply by initial T or R length for change and find new length

**aggregate equations

MC = (Wwet-Wdry)/Wdry * 100 A = (Wssd-Wdry)/Wdry * 100 SG of water = 62.4 lb/ft^3 bulk SSD SG = Wssd/(Vtot*62.4) free water = MC - A weight of free water = Wwet - Wssd

the rutting resistance of two different binders, PG70-28 and PG64-22 are evaluated at the same temp. which binder should exhibit more resistance to rutting? justify

PG70-28 - it is designed to withstand higher temperatures, and rutting occurs at higher temperatures

list two advantages and two disadvantages of aluminum as a civil engineering material

advantages - light weight - high strength-weight ratio disadvantages - low modulus of elasticity - high cost of production

explain the basic mechanism that causes concrete deterioration due to ASR

alkali silica reaction the silica in the aggregates reacts with the alkali in the cement paste this causes expansive reactions that lead to relative uniform excessive cracking (map cracking)

wood is isotropic/anisotropic? what does this mean?

anisotropic different properties in different directions

list an application where masonry is commonly used, and then list 3 advantages of masonry systems that makes masonry a good choice for those applications

application - school buildings advantages - speed of construction - cost - insulating qualities/fire resistance - availability - aesthetics

functions of masonry system components mortar grout reinforcement

bond masonry units together fills cells of masonry units to increase axial capacity; bond reinforcement to masonry unit carry any significant tensile loads generated

descriptions of slag fly ash silica fume

classified as grade 80, 100, or 120; is classified as cementing material byproduct of burning coal does not decrease the early strength gain of concrete

**know how to use a phase diagram

composition on x axis, temperature on the y axis composition and phases shown composition on y axis usually wrt a certain compound

**in the sketch of a steel bar below indicate the movement of electrons and ions. also, indicate the location where the material is being corroded diagram on quiz

electrons go from anode to cathode ions go from cathode to anode oxidation at anode, reduction at cathode corrosion most likely at anode, bc of lower potential

which of the three types of asphalt pavement failure modes would you expect to see at a toll plaza in PA? why?

fatigue cracking - constant wait of traffic on the surface rutting - wheel paths being engraved on the surface from weight of traffic and horizontal motion and especially when temperature is warmer; **slower traffic his answer: rutting - traffic forced through specific lanes; traffic is slow -- repeated loading in specific areas and more load in one spot

**develop concrete mixture

find values for water, cement, CA, and FA use tables step 1: choice of slump; table or use slump given step 2: choice of max aggregate size; given step 3: estimate water and air content - inside (not air entrained); outside (air entrained) - use table, select water (lb/yd^3) and air (%) contents based on slump, max agg size, and entrained or not step 4: w:c ratio - based on compressive strength and air entrained - compare to severe exposure value if applicable and use lower value step 5: calc cement content - cement = w/(w:c) (lb/yd^3) step 6: estimate CA content - based on max agg size and fineness - linear interpolation - (table value)*(27ft^3/yd^3)*(DRUW) = lb/yd^3 DRY - (lb/yd^3 DRY)(1+A) = lb/yd^3 SSD step 7: estimate FA content - find ft/yd^3 of air, water, cement, CA - subtract from 27 to get ft^3/yd^3 FA - divide by SG and 62.4 to get lb/yd^3 FA SSD step 8: adjust for MC - MC - A >0 = too wet (<0=too dry) - x% too wet --> multiply SSD by that number and add to SSD weight for FA and CA; subtract that number from water if too wet, add if too dry

define the three moisture content conditions green fiber saturation point (FSP) equilibrium moisture content (EMC)

freshly cut (relatively high MC) when there is no free water in the cell cavities but the cell walls are saturated with bound water average MC in service; when wood and environment are in equilibrium

**which type of corrosion is occurring at which picture pictures on quiz

galvanic - if two different materials are being used here, galvanic corrosion would be occurring crevice - this may be the corrosion if they are not two different metals. the threads/crevices between the bolt/washer/surface would cause corrosion pitting - concentrated points on the surface are corroding - pits form at location where corrosion initiates uniform corrosion - happening over whole surface

**determine design compression strength of masonry f'm

given: concrete or clay masonry units, avg compressive strength, type use table for either concrete or clay linear interpolation around correct avg strength and mortar type

**understand how to use 0.5% extension and how to find ultimate stress and strain, finding permanent (plastic) strain if loaded to certain stress

go to 0.005 on x axis, draw a line directly vertical - where this line intersects with graph is the yield stress ult. stress and strain found where stress is max ex. if loaded to 50ksi, go to 50ksi on y axis, draw horizontal line, then draw line down with same slope as beginning of graph (E); this gives plastic strain

what is the primary purpose for adding air entraining admixture to concrete? what are two other properties that are affected by adding air entraining admixture and how are they affected (increased/decreased)?

improving freeze thaw resistance - compressive strength - decreased - cohesion - increased (less prone to segregation)

indicate if each change below would cause an increase or decrease in the creep and shrinkage within the concrete decrease in the amount of aggregate in mixture increase length of curing decrease the amount of cement in mixture

increase decrease decrease

indicate if the condition described would result in an increase or decrease in the allowable bending stress in a wooden beam exposure to short term loads use in a repetitive system exposure to moist conditions

increase increase decrease

**determine approx. allowable design strength for wood material using a 95% confidence interval

lab testing for compressive strength FS!!! find compressive strength at bottom 5% allowable = actual/FS = (comp strength @ 5%)/FS

describe the composition of the two types of structural composite lumbers LVL PSL

laminated veneer lumber - thin veneers - veneers are bonded into large billet under temp and pressure, and cut to desired size - grains parallel to length - most common SCL - similar to plywood but orientation of veneers is different parallel strand lumber - strands - strands are bonded together parallel to the length of the member - bonded into a condensed billet - made stronger by the parallel orientation

does the mixture meet the requirements for the target design strength?

less than 15 samples: f'c<3000psi --> f'cr = f'c + 1000psi 3000</=f'c</=5000psi --> f'cr = f'c + 1200 f'c>5000psi --> f'cr = 1.10f'c+700psi more than 15 samples f'c</=5000 ---f'c+1.34s ---f'c+2.33s-500 F'c>5000 ---f'c+1.34s ---0.9f'c+2.33s if less than 30, need modification factor # samples/mod factor: 15/1.16 20/1.08 25/1.03 30/1 use linear interpolation if between value received from equation has to be less than the average to meet requirements

**use phase diagram to determine different percent compositions

linear interpolation! find values you know - at x% carbon, you have y% __ using your two known values, use linear interpolation to find unknown

briefly describe the process used to produce clay masonry units

mine the raw clay materials mix materials with water and form into shape dry and fire the clay drying occurs in an oven for 1-2 days (T=200-400 deg F) and most evaporation occurs before firing fire in a kiln for 40-150 hours (up to 2400 deg F) both steps are controlled then cool for 48-72 hours

describe the two test methods that are most commonly used to determine the tensile strength of concrete (pictures are also fine)

modulus of rupture (MOR) - loading 6x6x18" beam on its side at third points, and measuring the height and width at the location of failure; it will fail in the middle third portion split cylinder - load cylinder on its side with 1/8" wood slabs on top and bottom; load slowly until failure (cracking) and measure max load

explain why a 0.45 power chart is commonly used to plot aggregate gradations instead of a linear or log chart

more commonly used because it produces a straight line when maximum density is achieved

what are the materials that are combined to produce mortar grout

mortar: - fine aggregate (no CA) - cememt - water - lime - admixtures grout - fine aggregate - coarse aggregate - portland cement - water - lime - admixtures

list two methods for verifying the compaction level of asphalt pavements

nuclear density gage intelligent compaction **ok - non movement criteria - optimum rolling pattern - pavement cores

circle the preferred orientation for the beams supporting the 4x8' structural panel shown below. the supporting beams are indicated by dashed lines. why is that orientation preferred?

orientation with vertical dashed lines = strong orientation this is bc wood is stronger when the grains are parallel to the length of the beam. the panel needs more support from the beams in the orientation circled

what material property has the largest effect on the durability of concrete? list three ways to decrease this property

permeability lower w:c ratio add SCMs curing lower air content

shrinkage can be classified as plastic or drying shrinkage. briefly describe each type and indicate if it is preventable, and if it is, how to prevent it

plastic shrinkage - when concrete is still plastic - can lead to cracking/warping if shrinkage is too rapid/restrained - preventable - due to improper curing; lower w:c ratio drying shrinkage - occurs when concrete is drying and can cause cracking - not preventable, but steps can be taken to reduce effect (adding reinforcement, adding contraction joints, delaying drying to increase strength)

describe the ideal aggregate particle shape and texture to produce the most stable aggregate base when compacted

produced by aggregates having angular shapes and rougher textures achieved by crushing more angularity/roughness means more stability when compacted, and there is more friction between particles, so it's harder for the particles to move past each other

explain the difference between a property and a proportion specification for grout

property - testing is required - grout must be designed and tested in order to meet certain required property proportion - NO testing is required - grout is made using predetermined proportions that are known to produce specific properties use property OR proportion. proportion is the default if neither is specified

test methods charpy v notch test torsion test hardness

provides an indication of a metal's resistance to fracture; the results of this test are very sensitive to the temperature of the metal used to assess the shear resistance of the metals is considered a nondestructive test used to indirectly measure yield strength

define RAP and list two advantages of using RAP

reclaimed asphalt pavement - milled asphalt mixed with virgin binder at the plant economy - >25% savings on materials environmental - reduces new materials needed and makes better use of old materials / less waste energy - savings in manufacturing and transportation eliminates problem of reconstruction of utilities, curbs, and gutters associated with overlays maintains bridge and tunnel clearances

describe how concrete cylinders should be stored if they are being used to determine if the concrete meets the specified design strength

remove forms after 1-2 days and place in moist room or saturated lime water at 73F

bond descriptions covalent metallic ionic

requires sharing of electrons between atoms; behavior of materials with this bond are largely dependent on intermolecular attractions results in a material that is good at conducting heat one element loses electron(s) the other gain electron(s)

for each application, list curing method that would be most appropriate roadway prestressed girder bridge deck

seal - this is the most common and good for general use steam - this is less common, but often used when prestressing is involved moist curing - more critical application

list the first 4 steps in the superpave mixture design process

select aggregate select binder design aggregate structure design binder content

**bending problems

simply supported beam with load stress = Mc/I I = 1/12bh^3 c = h/2 compression at top, tension at bottom max stresses in center at top/bottom

four cylindrical samples of the same concrete were made and tested to determine their compressive strength. which sample would be expected to fail at the highest stress?

smallest sample would fail smaller = stronger due to the concept of the weakest link failing first. larger specimen are more likely to have a weaker weakest link...so lowest stress

**stress and strain equations

stress = P/A stress = E*strain

**determine if wall described meets design limits for tensile and compressive capacity of masonry

stress limits - compression: f'm from table and linear interpolation - tension: MOR from table section properties - A = bh - I = 1/12 bh^3 - multiply A and I by 12/16 to get units /ft of wall (currently are /16" bc of 16" block) stress - axial: stress = P/A (c) - moment: M = wL^2/8 (w=wind, L=wall height) (lb-ft/ft) ==> stress = Mc/I (mult by 12 to convert to psi) (c or T) combined - c = axial + moment < f'm --> ok - T = axial - moment < MOR --> ok - make values positive if they're negative if both are ok, design meets limits; if either is not ok (>f'm or MOR), design does not meet limits

why does steel not corrode when embedded in sound, uncontaminated concrete?

this is due to passivation the passivation layer is stable if the pH is high enough (approx. 11.5), and the pH of concrete is abt 13 also impacted by the presence of ions (especially chloride) therefore, concrete acts as a layer protecting the steel

what type of cement, supplementary cementitious material(s) and chemical admixture(s) would be used in a large concrete dam on soil containing sulfates in PA? justify

type V cement - high sulfate resistance air entraining admixture - prevent freeze/thaw due to changing temps in PA slag - applications to mass concrete and its ability to help with sulfate resistance

define: homogeneous isotropic elastic

uniform material same properties in different directions deforms immediately under applied load and returns to undeformed state when unloaded

explain the basic produce for determining the air content of fresh concrete

uses pressure to compress air and measure change in volume - fill bucket at bottom with concrete - add water to fill void space above concrete - close valves and apply pressure - release pressure and read air content filling the measurement device w the fresh concrete until the specified point water should be filled above that point hit the side of the container w a hammer (or something similar) read the air content off the dial

**determine VTM, VMA, VFA for mixture design

voids, effective binder, absorbed asphalt binder, effective aggregate VTM = Vv/Vm x 100 VMA = (Vv+Vbe)/Vm x 100 = (Vm-Vab)/Vm x 100 VFA = Vbe/(Vv+Vbe) x 100 *Wair = 0 given weights/volumes/SGs V=W/(62.4*SG) bulk agg = ae + ab binder = be + ab determine volumes for aggregates, then binder, then mix

**gradations; coarse and fine aggregate blend nominal maximum aggregate size maximum aggregate size

x%(coarse)+y%(fine) = gradation% guess and check or ex. 75(x)+100(1-x) = 85 nominal: first sieve to catch something max: last sieve that everything passes through