CGN3501C Test 1 Study Materials - Engineering Concepts and Definitions

What are the SI (International System) units for length, mass, force, pressure and energy, and the corresponding standardized symbols for these units? What are the American (old English) units for these measurements?

LENGTH: m/ft,in

MASS: g/pound mass (lbm)

FORCE: N/pound force (lbf)

PRESSURE: pascal(Pa=N/m^2)/pound/in^2(psi)

ENERGY: joule(J=N*m)/foot-pound (ft-lbf)

What are the standardized prefixes for 109, 106, 103, 10-2, 10-3, 10-6 and 10-9?

10^9: Giga (G)

10^6: Mega (M)

10^3: Kilo (k)

10^-2: Centi (c)

10^-3: Milli (m)

10^-6: Micro (mu)

10^-9: Nano (n)

How many grams (g) are equal to one pound mass (lbm)?

1 lbm = 454 g

How many centimeters (cm) are equal to one inch (in)?

1 in. = 2.54 cm

How many newtons (N) are equal to one pound force (lbf)?

1 lbf = 4.45 N

What is the density of water in both units?

1 g/cm^3 = I Mg/m^3 = 62.4 lbm/ft^3

What are the three major types of rock and how were they formed? Give an example for each type of rock.

1. Igneous: formed on cooling of the magma. Ex: granite, trap rock, basalt, perlite.

2. Sedimentary Rock -formed from disintegration of other rocks and deposited as sediments. Examples: limestone, sandstone, shale

3. Metamorphic Rock -Igneous or sedimentary rocks that have changed its structure due to heat and pressure. Usually harder and denser. Examples: marble, slate.

What are the differences between intrusive igneous and extrusive igneous rocks?

Intrusive igneous -formed by slow cooling beneath earth's surface. Characteristics: completely crystalline minerals, coarser grain. Examples: granite, trap rock.

Extrusive igneous -formed by more rapid cooling at or near earth's surface. Characteristics: finer grain, minerals with smaller crystals or glassy structures. Examples: basalt, perlite.

Give a few examples of artificial aggregates.

blast-furnace slag, expanded clay, expanded shale.

What are the definitions of coarse and fine aggregates?

Coarse aggregate: particles retained on No.4 sieve (4.75mm or 3/16 in.)

Fine aggregate: particles passing No. 4 sieve.

What are the functions of aggregate in concrete?

1. Economy (aggregate as space filler)

2. Strength

3. Reduction in shrinkage and expansion

Describe (A) the purpose of the test, (B) how the test results are reported, (C) the meaning of the test results, and (D) the typical threshold test values (if any) required in material specifications, for each of the following tests on aggregates:(1) L.A. Abrasion Test

Purpose: To determine hardness or resistance to abrasion of an aggregate

Reported: Change in weight/original weight (%)

Meaning: Loss of material

Results: Loss should be less than 45%

Describe (A) the purpose of the test, (B) how the test results are reported, (C) the meaning of the test results, and (D) the typical threshold test values (if any) required in material specifications,for each of the following tests on aggregates:(2) Soundness Test

Purpose: To measure resistance to weathering

Reporting: Weighted % loss

Meaning: Loss of material

Results: Loss less than 12%

Describe (A) the purpose of the test, (B) how the test results are reported, (C) the meaning of the test results, and (D) the typical threshold test values (if any) required in material specifications,for each of the following tests on aggregates:(3) Sieve Analysis

Purpose: To determine gradation (size distribution)of aggregates.

Describe (A) the purpose of the test, (B) how the test results are reported, (C) the meaning of the test results, and (D) the typical threshold test values (if any) required in material specifications,for each of the following tests on aggregates:(4) Potential Reactivity

PURPOSE: To determine the potential alkali reactivity of an aggregate

Reporting: % Length change of mortar bars

Meaning: Expansion of mortar bars

Results: Greater than .10% expansion after 6mo, alkali reactive

Describe (A) the purpose of the test, (B) how the test results are reported, (C) the meaning of the test results, and (D) the typical threshold test values (if any) required in material specifications, for each of the following tests on aggregates:(5) Organic Impurity Test

Purpose: To determine the presence of injurious organic compounds in natural sands

Reporting: Color strength ratio (%)

Meaning: Liquid color

Results: Liquid is darker, organic impurities present

Describe (A) the purpose of the test, (B) how the test results are reported, (C) the meaning of the test results, and (D) the typical threshold test values (if any) required in material specifications,for each of the following tests on aggregates:(6) Effect of Organic Impurity of Fine Aggregate on Strength of Mortar

Purpose: Effect of Organic Impurity of Fine Aggregate on Strength of Mortar

Reporting: % Strength Ratio

Meaning: Avg. mortar strength ratio

Results: Ratio should be greater than 95%

Describe (A) the purpose of the test, (B) how the test results are reported, (C) the meaning of the test results, and (D) the typical threshold test values (if any) required in material specifications,for each of the following tests on aggregates:(7) Materials Finer than No. 200 Sieve

It is desirable to have low percentage of material passing No. 200 sieve.

Reporting: % passing No. 200 sieve by wet sieving and drying

Results: Maximum allowable percentage 1% for coarse agg., 3-5% for fine aggregate

Describe (A) the purpose of the test, (B) how the test results are reported, (C) the meaning of the test results, and (D) the typical threshold test values (if any) required in material specifications,for each of the following tests on aggregates:(9) Clay Lumps and Friable Particles in Aggregate

Purpose: Finding amount of lumps in aggregate

Reporting: % of material that is broken

Results: 3% allowable for fine agg., 2-10% for coarse agg.

Describe (A) the purpose of the test, (B) how the test results are reported, (C) the meaning of the test results, and (D) the typical threshold test values (if any) required in material specifications,for each of the following tests on aggregates:(10) Specific Gravity Test

dry wt in air/(SSD wt in air - wt in water)

Describe (A) the purpose of the test, (B) how the test results are reported, (C) the meaning of the test results, and (D) the typical threshold test values (if any) required in material specifications,for each of the following tests on aggregates:(11) Absorption and Surface Moisture Test

% Absorption: (SSD wt - oven-dry wt)/(oven-dry wt)*100

% Natural Moisture: (Natural Wt. - Oven-Dry Wt.)/(Oven-Dry Wt.)*100

Describe (A) the purpose of the test, (B) how the test results are reported, (C) the meaning of the test results, and (D) the typical threshold test values (if any) required in material specifications,for each of the following tests on aggregates:(12) Bulk Unit Weight Test

Wt. of Agg/Bulk Vol. of Agg.

Know the standard sieve sizes

6", 3", 1.5", 3/4", 3/8", #4 (3/16"), #8 (3/32"), #16 (3/64"), #30 (3/120"), #50, #100 & #200.

Know how to compute the Fineness Modulus of a fine aggregate given the results of a sieve analysis. What are highest and lowest possible values of F.M.?

SUM(%Pass in Standard sieves - 100)/100

Range: 2.15-3.38

What are the Fuller's Maximum Density Curve and the FHWA's Maximum Density Curve?

Fuller's Maximum Density Curve (THEORY): %P = (d / D)^(0.5)X 100% where: %P = % Passing the sieve d = Size of the sieve D = Maximum aggregate size

FHWA Maximum Density Curve (ACTUAL): %P = (d / D)^(0.45)X 100%

What is the (A) maximum aggregate size, and (B) nominal maximum aggregate size?

Maximum Size -The smallest sieve that 100% of the aggregate must pass.

Nominal Maximum size -The smallest sieve which the major portion of the aggregate must pass. It may retain 5% to 15% of the aggregate, depending on the size number of the aggregate.

What are (A) a uniform, (B) a gap-graded, and (C) a well-graded or dense-graded gradations? What are the typical plots of these gradations on a gradation chart? Which of these gradations are open-graded?

Uniform Gradation -mostly one size. (horizontal, constant slope, horizontal)

Gap-graded -missing a few sizes. (constant slope, horizontal, constant slope)

Well-Graded or Dense-Graded - Well distributed in various sizes, resulting in low air voids and high density when compacted. (constant slope)

Describe a gradation chart with the sieve sizes raised to 0.45 power.

constant slope

Know how to compute for (B) the S.S.D. bulk specific gravity

SSD Bulk Specific Gravity =SSD Wt. in Air/(SSD Wt. In air) -(Wt. in water)

Know how to compute for (A) the dry bulk specific gravity

Dry bulk specific gravity = (Dry wt in air)/((SSD Wt in air)-(Wt in water))

Know how to compute for (C) the absorption of an aggregate from the raw laboratory data.

% Absorption =(SSD Wt. - Oven Dry Wt.)/ (Oven Dry Wt)X 100%

What are the difference between the bulk density and the bulk unit weight of an aggregate?

bulk density always higher than unit weight

Describe a few principles which could be followed to reduce segregation of aggregate during handling and storing.

(1) Do not store in high cone-shape pile.

(2) Do not let aggregate run down slope.

(3) Avoid a blowing wind.

What are the desirable properties of aggregate for use in Portland cement concrete? What tests would you run on the aggregate to ensure that an aggregate has these desirable properties?

-rough textured and angular aggregates.-LA abrasion test, SG test, soundness test, etc

Coarse aggregates produced in Florida are primarily porous limestone with a relatively higher water absorption (3 to 10%). Are there any limitations in producing quality concrete using these indigenous aggregates?

Higher moisture content in concrete can result in a lower overall strength, so a highly water absorbent aggregate can possibly decrease the concrete strength.

What are the effects of particle shape and surface texture of aggregate on the properties of fresh and hardened concrete?

-Rough textured and angular aggregates give better bonding between the aggregate and the cement paste and thus higher strength for the same water cement ratio.-However, rough and angular aggregates requires more water to produce the same workability in a fresh concrete.The two effects offset one another. With satisfactory gradation, both crushed and noncrushed aggregates (of the same rock type) generally give about the same strength for the same cement content.It is undesirable to have flat and elongated particles.

Compare and know the typical bulk unit weights of (A) normal natural aggregates. (B) lightweight aggregates, (C) heavyweight aggregate and (D) blast-furnace slag.

(A)95 to 105 pcf

(B)70 pcf

(C)130 pcf

(D)70 to 85 pcf

Describe the typical properties of recycled concrete as aggregate, and the properties of concrete made with recycled concrete.

-Old concrete crushed to proper gradation can be used as aggregate.-The strength and durability of the concrete produced are limited by those of the old concrete.-Generally has a higher absorption, a lower specific gravity, and a lower strength than a normal natural aggregate.-FDOT spec. allows a maximum L.A. Abrasion Loss of 50% for recycled concrete aggregates.

Who invented Portland cement and when?

(Joseph Aspdin, an English brick mason, obtained a patent for Portland cement in 1824.)

Why is it called Portland cement?

the concrete it produced resembled the color of the natural limestone quarried on the Isle of Portland, a peninsula in the English Channel

What is the difference between a hydraulic and a non-hydraulic cement? Is Portland cement a hydraulic cement?

Hydraulic cement-hardens by reacting with water to form a water-resistant product. The presence of air is not required for the hardening process. Example: Portland cement.

Nonhydraulic cement-reacts with water to form a product which is not stable in water. The hydration product may then react with air to form a water-resistant product. Example: Quick Lime.

What is the maximum size of Portland cement particles?

No. 200 sieve

What is the typical specific gravity of Portland cement?

3.15

What is weight of a commercial sack of Portland cement? What does a six-bag mix mean?

94 lbs

3500 psi concrete is called a 6 sack mix or 6 bag mix of concrete.

What are the four main oxides Portland cement contain and the abbreviations used for these four oxides in cement chemistry?

Tricalcium Silicate (C3S),

Dicalcium Silicate (C2S),

Tricalcium Aluminate (C3A), Tetracalcium AluminoferriteC4AF

What are the characteristics and functions of the four main compounds in Portland cement?

C3S: initial set and early strength

C2S: strength increase beyond one week

C3A: increases sulfate attacks

C4AF: reduces cost

Is cement hydration an exothermic or endothermic process? What are the two main chemical compounds produced as the result hydration of C2S or C3S?

EXOTHERMICC3S2H3 and CH

What are the five main types of Portland cement and their applications?

Type I-For general use. Type II-Moderate sulfate resistance & moderate heat of hydration. Type III-High early strength. Type IV-Low heat of hydration.

Type V-High sulfate resistance.

What are the main raw materials used in the manufacturing of Portland cement? Describe the basic steps in the manufacturing of Portland cement.

- limestone, shells, and chalk or marl combined with shale, clay, slate, blast furnace slag, silica sand, and iron ore.Milling produces a fine powder, known as raw meal, which is preheated and then sent to the kiln for further processing.The kiln is at the heart of the manufacturing process. Once inside the kiln, the raw meal is heated to around 1,500 degrees C - a similar temperature to that of molten lava. At this temperature, chemical reactions take place to form cement clinker, which contains hydraulic calcium silicates.In order to heat the materials to this very high temperature, a 2,000-degree C flame is required, which can be produced through the use of fossil and waste-derived fuels. The kiln itself is angled by 3 degrees to the horizontal to allow the material to pass through it, over a period of 20 to 30 minutes.

Upon exiting the kiln, the clinker is cooled and stored, ready for grinding, to produce cement.

Describe (A) the purpose of the test, (B) how the test results are reported, (C) the meaning or significance of the test results, (D) the typical threshold test values (if any) required in cement specificationsfor each of the following tests on Portland cement:(1) Wagner Turbidimeter

Purpose: To measure the fineness of a cement

Results: specific surface (higher is finer)

Describe (A) the purpose of the test, (B) how the test results are reported, (C) the meaning or significance of the test results, (D) the typical threshold test values (if any) required in cement specificationsfor each of the following tests on Portland cement:(2) Blaine Air Permeability

Purpose: To measure the fineness of a cement

Results: specific surface (higher is finer)

Describe (A) the purpose of the test, (B) how the test results are reported, (C) the meaning or significance of the test results, (D) the typical threshold test values (if any) required in cement specificationsfor each of the following tests on Portland cement:Autoclave Expansion

Purpose: Test for Soundness of Portland Cement (ability to retain its volume after setting)

Results: autoclave expansion

Describe (A) the purpose of the test, (B) how the test results are reported, (C) the meaning or significance of the test results, (D) the typical threshold test values (if any) required in cement specificationsfor each of the following tests on Portland cement:(4) Vicat

Purpose: tests for Time of Setting

Results: initial and final setting time

Describe (A) the purpose of the test, (B) how the test results are reported, (C) the meaning or significance of the test results, (D) the typical threshold test values (if any) required in cement specificationsfor each of the following tests on Portland cement:(5) Gillmore

Purpose: tests for Time of Setting

Results: initial and final setting time

Describe (A) the purpose of the test, (B) how the test results are reported, (C) the meaning or significance of the test results, (D) the typical threshold test values (if any) required in cement specificationsfor each of the following tests on Portland cement:(6) Compressive Strength Test on Mortar Cubes

the purpose of this test is to ensure the quality of a cement with regards to strength development.

Results: compressive strengths

Describe (A) the purpose of the test, (B) how the test results are reported, (C) the meaning or significance of the test results, (D) the typical threshold test values (if any) required in cement specificationsfor each of the following tests on Portland cement:(7) Loss on Ignition

Purpose: To measure the level of pre-hydration of a cement.

Results: A high % Loss on Ignition gives an indication of high prehydration and carbonation,

Describe (A) the purpose of the test, (B) how the test results are reported, (C) the meaning or significance of the test results, (D) the typical threshold test values (if any) required in cement specificationsfor each of the following tests on Portland cement:(8) Heat of Hydration

What is a pozzolan?

a siliceous or siliceous and aluminous material which in itself possesses no cementing property but will, in the presence of water, react with calcium hydroxide to form a cementitious product which is stable in water.

What is a ground granulated blast furnace slag?

Blast-furnace slagis a nonmetallic waste product from the blast-furnace process in the manufacturing of iron and steel. Granulated slag is a glassy product formed by rapid cooling of the molten blast-furnace slag. It consists mainly of silicates and aluminosilicates of calcium. it is self cementing and the calcium hydroxide is consumed by the slag in a pozzolanic reaction.

What is a pozzolanic reaction?

the chemical reaction that occurs in Portland cement upon the addition of pozzolans

The pozzolanic reaction converts a silica-rich precursor with no cementing properties, to a calcium silicate, with good cementing properties.

what are the effects of pozzolan and ground granulated blast furnace slag on the strength and durability of concrete?

•Lower early strength & lower heat of hydration as compared with normal concrete.

•Ultimate strength can be higher than that of normal concrete.

•Portland blast-furnace slag cement has a more rapid strength gain than Portland pozzolan cement.

•Water resistance is increased since calcium hydroxide is consumed.

•Permeability is reduced since more pores are filled by the products of pozzolanic reaction.

•The sulfate resistance of the concrete is increased (with the reduction in permeability and calcium hydroxide.) •Alkali-aggregate expansion is reduced.

What is the main difference between a pozzolan and a ground granulated blast furnace slag?

ground granulated blast furnace slag is self cementing

What is a Portland-pozzolan cement? What are the differences in properties between a Portland-pozzolan cement concrete and a normal Portland cement concrete?

-Portland pozzolan cement(Type IP & P) - blend of Portland cement with 15 to 40% fine pozzolan by weight. Type P has a lower early strength than Type IP, and is used when high early strength is not required.

What is a Portland-blast-furnace-slag cement? What are the differences in properties of a Portland-blast-furnace-slag cement as compared with those of a normal Portland cement concrete?

Portland blast-furnace slag cement(Types IS) - blend of Portland cement with 25 to 70% by weight of granulated blast-furnace slag.

CONTINUE

What is the main difference between a white Portland cement, a colored Portland cement and a normal Portland cement?

Just the color, properties remain the same

What are the three main ingredients in Portland cement concrete?

1) water

2) cement

3) aggregate

What are the desirable properties of a fresh concrete?

a) ease of transportation

b) resistance to bleeding and segregation

c) consistency

d)cohesiveness

e)workability

What are the two commonly-used methods to measure the consistency of a fresh concrete? What is the relationship between the results obtained by these two methods?

1) slump test

2) ball penetration test

Both test measure the displacement of concrete.

What are the typical specified slump of fresh concrete for (A) large foundations, (B) pavements, and (C) columns?

(A) 0.5 - 2.5

(B) 2 - 5.5

(C) 5 - 8

What is the most important factoraffecting the consistency of a fresh concrete? What are the other factors affecting the consistency of a fresh concrete? Describe these factors and their effects.

-Water content

-Cement content: increasing the cement content gives better cohesiveness but higher stickiness.

-aggregate size: increasing max aggregate size increases the slump of the fresh concrete.

-aggregate angularity/roughness: higher angularity/roughness produces lower slump.

-admixture: water reducing, air entraining and fly ash admixtures increase the slump.

What is bleeding in fresh concrete? What are the effective remedies to reduce bleeding problems?

-Bleeding of fresh concrete is manifested by the appearance of water on the surface after a concrete has been placed and compacted.

Remedies:

-use air entrainment and reduce water content.-increase the proportion of sand/cement in the mix.

-use mineral admixtures such as fly ash or blast-furnace slag to reduce water content.

What are two convenient tests to check whether or not a concrete mix has been properly batched?

1)slump test

2) unit weight test

What is the typical range of 28-day compressive strength of normal concrete?

2000-6000 psi

What are the approximate relationships between the tensile strength, flexural strength and elastic modulus with the compressive strength of concrete?

Tensile strength: 1/10 OF COMP

Flexural strength:

elastic: appx 1000*compressive

What is the most important mix parameteraffecting the strength of concrete? What are the other factors affecting the strength? Describe thesefactors and their effects.

-water to cement ratio- Age: strength increases with time- curing condition: longer moist curing and higher temperature = higher strength- type of cement and admixture: can affect rate of strength and ultimate strength-strength of aggregate: strength of concrete is limited by the strength of aggregate-moisture content of concrete: higher moisture = lower strength

What is creep property, and why is it important to evaluate the creep property of concrete?

Creep: continued yielding under sustained stress

Important bc creep of concrete under sustained stress may cause reduction of prestress in prestressed concrete structures

What are the effects of concrete permeability on its performance?

Permeability: ease of flow of fluid or gas through the concrete

Low permeability of concrete prevents:

- disintegration caused by freezing of saturated porous concrete

- dissolving of slowly soluble components in concrete

- chloride intrusion causes corrosion of rebars

What is a typical density of normal concrete ?What is the typical density of concrete made with Florida limestone?

Normal: 150pcf

Limestone:140pcf

How do we ensure uniformity in batching for a concrete mix?

Batching by weight and loss of fines should be minimized

How long should we mix a concrete mixture?

1 to 3 minutes

What are the different ways concrete can be batched, mixed and transported to the job site? What are the different kinds of truck used to transport concrete to the job site?

Mixed:

a. Central mixed: mixed completely in a stationary mixer

b. Shrink mixed: mixed partially in a stationary mixer; mixing completed in a truck mixer

c. Truck mixed: mixed completely in a truck mixer

Transported:

a. trucks

b. bucket

c. buggy

Trucks:

a. Mixer Truck

b. Special Dump Truck

What is "false set"? What could we do if a concrete false set? How could false set be prevented?

stiffening of concrete shortly after mixing with no generation of heat due to improper composition of cement or pre-hydration of cement

To fix this, rigorously remix

It could be prevented by longer mixing time

What are the different equipment used to convey fresh concrete at the construction site?

belt conveyorpumpchute

What are a few effective measures to reduce segregation of fresh concrete during placement?

1)avoid concrete hitting the form by using a hopper.

2)avoid concrete running down a slope.

3) use a baffle and drop at the end of the chute.

How do we consolidate the fresh concrete that is placed?

1)hand rodding or tamping

2)internal vibrator

3)external vibrator

What the basic steps in finishing a concreteslab? Describe the purpose of each step.

1. Strikeoff/Screeding: Striking off excess concrete to bring the top surface to proper grade

2. Bullfloating: Leveling to eliminate high and low spots

3. Floating: Firmly embeds the aggregate, to compact the surface and remove any surface imperfections

4. Troweling: Finishing to obtain a smooth, dense surface

5. Texturing: Finishing to obtain desired surface texture

How can we produce the different textures in the concrete surface?

brooming to obtain slip resistant surface.

What are isolation joint, construction joint & control (or contraction) joint? What is the main purpose of each joint and how is it constructed?

Isolation joint (or expansion joint): isolates one concrete structure from another; permits vertical and horizontal movement

Construction joint: stops places during construction

Control joints (most common): control where crack is going to be (no random cracks); permits thermal shortening and drying shrinkage in the plane of slab

Why is it important that a concrete be properly cured? What is the basic principle to follow to ensure proper curing of concrete?

2 objectives: to keep the concrete moist and control the temperature of the concrete

Basic principle: preventing loss of moisture, supplying additional moisture, accelerating strength gain

Describe the following curing methods: (A) Sprinkling

Continuous sprinkling to keep the surface wet

Describe the following curing methods: (B) Wet covering

Covering with moisture retaining fabrics and intermittent sprinkling

Describe the following curing methods: (C) Ponding

Retaining a pond of water by means of earth dikes

Describe the following curing methods:(D) Waterproof covers

covering with waterproof paper or plastic sheets, or spraying surface with a curing compound which acts as a water barrier.

Describe the following curing methods: (E) steam curing

Steam curing keeps the surface moist and raises the temperature of concrete to quicken the rate of strength achievement.

What are the effects of replacing a portion of Portland cement with fly ash in Portland cement concrete on the durability of the concrete? Explain why this is so.

Replacing cement with the same amount of fly ash can reduce the heat of hydration of concrete. This reduction in the heat of hydration does not sacrifice long-term strength gain or durability. The reduced heat of hydration lessens heat rise problems in mass concrete placements.