CE332 Engineering Materials Exam 2 MCQ Practice

[Aggregates] What is aggregate?

Mineral particles used in foundations, embankments, erosion protection, and concrete or asphalt mixtures.

[Aggregates] What is the primary challenge in aggregate use?

Controlling variable source properties to obtain consistent materials that meet specifications.

[Aggregates] Give natural aggregate sources.

Gravel pits, river deposits, and rock quarries.

[Aggregates] Give industrial or recycled aggregate sources.

Slag, expanded shale, recycled asphalt, and recycled concrete.

[Aggregates] Which sieve separates coarse and fine aggregate in these notes?

The #4 sieve, 4.75 mm; coarse is retained and fine passes.

[Aggregates] What particle properties generally improve stability?

Cubic or equidimensional shape, angularity, and rough texture.

[Aggregates] What particle properties generally improve workability?

Equidimensional, rounded, smooth particles; avoid flat and elongated shapes.

[Aggregates] Why avoid flat or elongated particles?

They can orient poorly and break during construction or service loading.

[Aggregates] What is angularity?

The degree of sharp edges and corners; angular particles improve mechanical interlock.

[Aggregates] What is surface texture?

The roughness or smoothness of a particle surface; roughness can improve binder or paste bonding.

[Aggregates] What does a proportional caliper assess?

Flat and elongated coarse particles using a specified dimensional ratio.

[Aggregates] What does fractured-face inspection assess?

The percentage of coarse particles with a required number of fractured faces.

[Aggregates] What does the fine aggregate angularity test measure?

Uncompacted void content; higher voids usually indicate greater angularity or roughness when grading is controlled.

[Aggregates] What is toughness?

Resistance to degradation from impact and abrasion.

[Aggregates] What does LA abrasion measure?

Aggregate degradation resistance, reported as mass loss; lower loss indicates better resistance.

[Aggregates] What is soundness?

Resistance to weathering-related breakdown, such as repeated freezing and thawing.

[Aggregates] What is the sulfate soundness outcome?

Percentage mass loss after prescribed salt exposure cycles.

[Aggregates] Why are clay coatings undesirable?

They can interfere with bonding between aggregate and cement paste or asphalt binder.

[Aggregates] What does a higher sand equivalent generally indicate?

Cleaner aggregate with less claylike material relative to sand.

[Aggregates] What is gradation?

Particle-size distribution expressed by mass fractions or percentages passing sieves.

[Aggregates] What is individual percent retained?

Mass retained on one sieve divided by total aggregate mass, times 100.

[Aggregates] What is cumulative percent retained?

The total percentage retained on a sieve and all larger sieves.

[Aggregates] How do you calculate percent passing?

100 minus cumulative percent retained at that sieve.

[Aggregates] Must pan mass be included in total sample mass?

Yes, it contributes to the total sample used to calculate percentages.

[Aggregates] What is the generic maximum aggregate size definition in the notes?

The smallest sieve through which 100% passes; always check the specification convention.

[Aggregates] How is Superpave NMAS found in this review?

Find the first sieve retaining more than 10% individually, then select one sieve larger.

[Aggregates] Under the stated Superpave convention, how is MAS related to NMAS?

MAS is one sieve larger than NMAS; do not mix this rule with a different generic MAS definition.

[Aggregates] Does exactly 10% individual retention satisfy the Superpave greater-than-10% trigger?

No. The stated trigger is more than 10%.

[Aggregates] What does FM measure approximately?

Relative fineness or coarseness as a surrogate for aggregate surface area.

[Aggregates] What does higher FM mean?

Coarser aggregate, with more cumulative retention on the specified sieve series.

[Aggregates] How is FM calculated in the supplied aggregate notes?

Sum cumulative percentages retained on 3/8 inch, #4, #8, #16, #30, #50, #100, then divide by 100.

[Aggregates] Is #200 or pan included in the FM sum?

No.

[Aggregates] Does equal FM imply identical gradation?

No. Different sieve distributions can give the same FM.

[Aggregates] What is dense grading?

A broad particle-size distribution that can pack with relatively few interparticle voids.

[Aggregates] What is open grading?

A distribution deficient in fines, typically leaving connected interparticle voids.

[Aggregates] What is gap grading?

A distribution missing or deficient in an intermediate size range.

[Aggregates] What is one-sized or uniform grading?

A distribution concentrated within a narrow range of particle sizes.

[Aggregates] What is plotted horizontally on a 0.45-power gradation graph?

Sieve opening raised to the 0.45 power.

[Aggregates] What is the maximum-density power relationship?

Percent passing = 100(d/D)^n; use n = 0.45 for the course maximum-density line and consistent units for d and D.

[Aggregates] What does a lower passing curve generally imply at the same sieve?

Coarser aggregate and typically higher FM.

[Moisture] What is oven-dry aggregate?

Aggregate with accessible pore water removed by the prescribed drying process.

[Moisture] What is SSD?

Saturated surface dry: water-accessible pores filled, with no surface water.

[Moisture] What is SSW in the course notes?

Saturated surface wet, the wet stockpile state with surface water beyond SSD.

[Moisture] How are total, absorbed, and free moisture related?

Total moisture = absorption + free moisture, all on the same dry-mass basis.

[Moisture] What is the denominator for moisture percentages?

Oven-dry aggregate weight.

[Moisture] How is absorption fraction A calculated?

A = (WSSD - Wdry)/Wdry.

[Moisture] How is total moisture fraction T calculated?

T = (Wwet - Wdry)/Wdry.

[Moisture] How do you convert SSD aggregate weight to dry weight?

Wdry = WSSD/(1 + A), using A as a decimal.

[Moisture] How do you convert dry aggregate weight to stockpile weight?

Wwet = Wdry(1 + T), using T as a decimal.

[Moisture] How is free water carried by aggregate found?

Wfree = Wdry(T - A) = Wwet - WSSD.

[Moisture] What if total moisture equals absorption?

The aggregate is SSD and contributes no free surface water.

[Moisture] What if total moisture is below absorption?

The aggregate has an absorption deficit; its free-water correction is negative.

[Moisture] What if aggregate free-water correction is negative?

Increase water added to compensate for water the aggregate will absorb.

[Moisture] How do you calculate water to add to a batch?

Design effective water minus the sum of aggregate free-water contributions.

[Moisture] Why correct for rain?

Increased surface moisture otherwise raises effective water and w/c and can reduce strength and durability.

[Moisture] What is 2% written as a fraction for calculations?

0.02.

[Gravity] What is specific gravity?

Material density or unit weight divided by that of water; it has no units.

[Gravity] What water unit weight is used in these problems?

62.4 lb/ft3.

[Gravity] What is aggregate bulk particle volume Vsb?

Mineral solid plus impermeable and permeable particle pores; it excludes voids between particles.

[Gravity] What does apparent particle volume exclude?

Permeable pores within particles.

[Gravity] How is coarse aggregate bulk dry G found?

Dry weight divided by SSD weight minus submerged weight.

[Gravity] How is coarse aggregate SSD G found?

SSD weight divided by SSD weight minus submerged weight.

[Gravity] How is coarse aggregate apparent G found?

Dry weight divided by dry weight minus submerged weight.

[Gravity] What physical principle supports aggregate G tests?

Buoyancy and water displacement.

[Gravity] Which G pairs with SSD weight?

GSSD.

[Gravity] Which G pairs with dry weight?

Bulk dry specific gravity, for bulk particle volume calculations.

[Gravity] What is DRUW?

Dry-rodded aggregate weight divided by container volume, including interparticle voids.

[Gravity] How are particle volume and container volume different?

Container volume includes voids between particles; bulk particle volume does not.

[Gravity] How is interparticle void percentage calculated?

[1 - DRUW/(Gbulk,dry x 62.4)] x 100.

[Gravity] At fixed particle G, what does increased DRUW imply?

Improved packing or compaction and a lower interparticle void fraction.

[Gravity] How are GSSD and Gdry related to absorption?

GSSD/Gdry = 1 + A for consistent bulk volume and data.

[Blending] How is blend percent passing computed?

Pblend = aPA + bPB + … using mass fractions that sum to one.

[Blending] How is blend FM computed?

FMblend = aFMA + bFMB + … with the same FM sieve basis.

[Blending] What must a blend satisfy?

Every sieve band, not just one selected sieve or an FM target.

[Blending] How is dry-mass blend specific gravity computed?

Gblend = 1/(a/GA + b/GB + …) when fractions sum to one and all G values use the same basis.

[Blending] Why not average specific gravities arithmetically by mass?

Component volumes add; each component volume is proportional to mass divided by its specific gravity.

[Cement] What is PCC?

Portland cement concrete: aggregate bound by hydrated cement paste, with water, air, and optional admixtures.

[Cement] How is cement different from concrete?

Cement is the binder ingredient; concrete is the composite mixture.

[Cement] What is a hydraulic cement?

A cement that reacts with water to form products capable of hardening under water.

[Cement] What is a nonhydraulic lime binder?

A binder that hardens mainly by carbonation in air rather than hydraulic reaction.

[Cement] What raw materials commonly supply cement oxides?

Limestone supplies mainly lime; clay or shale supplies silica, alumina, and iron oxide.

[Cement] What forms in the rotary kiln?

Clinker, which is cooled and ground with gypsum to produce portland cement.

[Cement] What is typical portland cement specific gravity?

About 3.15.

[Cement] What do C, S, A, F, and H mean in cement notation?

CaO, SiO2, Al2O3, Fe2O3, and H2O, respectively; S-bar denotes SO3.

[Cement] What is C3S?

Tricalcium silicate or alite; major contributor to early strength.

[Cement] What is C2S?

Dicalcium silicate or belite; slower hydration and later strength contribution.

[Cement] What is C3A?

Tricalcium aluminate; very reactive and important for early set, heat, and sulfate vulnerability.

[Cement] What is C4AF?

Tetracalcium aluminoferrite; ferrite phase with relatively minor strength contribution.

[Cement] Why add gypsum?

To regulate early C3A hydration and prevent flash set.

[Cement] What does Type I mean?

General-purpose portland cement.

[Cement] What does Type II mean?

Moderate sulfate resistance.

[Cement] What does Type III mean?

High early strength, often associated with finer grinding.

[Cement] What does Type IV mean?

Low heat of hydration for large mass placements.

[Cement] What does Type V mean?

High sulfate resistance, with low C3A.

[Cement] What does the A suffix mean in IA or IIA?

Air-entraining cement.

[Cement] Is Type III alone enough for freeze/thaw resistance?

No. The mixture still needs an appropriate air system, low permeability, and curing.

[Hydration] What is hydration?

The chemical reaction of cement with water; it is not drying.

[Hydration] What does exothermic mean?

The reaction releases heat.

[Hydration] What is setting?

The transition from workable plastic concrete to rigidity.

[Hydration] What is hardening?

The development of useful strength after the onset of rigidity.