Codes and Specs. Conceptual

Three Materials in Slabs

Cement, Aggregates, Rebar

2 Examples of Ductile Material

Gold and Copper

2 examples of Brittle Material

Bismuth and Quartz

Name 3 Important Physical Properties of Materials

Density, Void Content, and Porosity

What is the Equation for Strain?

E= Change in Length/ Original Length

Define Poisson’s Ratio (word definition)

Poisson’s Ration is the ratio of lateral strain to the axial strain

Define Poisson’s Ratio (equation)

V= -Etrans / Elong

What is the Equation for Surface Moisture?

SM= Moisture Content - Absorption Content

What is Gap-Graded Aggregate?

A mix of aggregate where one or more intermediate sizes are missing

How does Fineness Modulus Work When Finding the Average Size of a Sample?

If given FM=#, we then move # from the smallest sieve tested up (We include the first sieve in the count and the last we count is the answer).

What is the Maximum Size of Fine Aggregate?

4.75 mm

What is the Equation for Moisture Content?

MC = (OG W- OD W) / (OD W)

What is the Maximum Size of an Aggregate That Will Be Used in a 5in Retaining Wall?

For Retaining Wall, Max Size is 1/5in of narrowest part. So for 5 in it will be 1 in.

What is the Nominal Aggregate Size?

It is the smallest sieve size that 95% of the sample passes through.

What is a Full vs Half size sieve?

A Full size sieve is half the size of the sieve before it whereas a Half size sieve does not follow this pattern.

How to Calculate FM given % Coarser?

FM = (Sum of % Coarser)/100

Sieve Analysis: Percent Coarser

% Coarser = Sum of larger samples retained including the current sample retained.

Sieve Analysis: Percent Finer

% Finer is all of the percent of the sample that passed the current sieve size (do NOT include current size retained).

Why add Gypsum to Cement?

It acts as a retardant, preventing flash setting.

What are The Four Major Compounds of Cement?

Tricalcium Silicate

Dicalcium Silicate

Tricalcium Aluminate

Tetracalcium Aluminoferrite

Which of The Four Major Compounds is Most Reactive To Cement?

Tricalcium Aluminate

What type of Cement Gives High Early Strength?

Type III

Define Consistency (cement)

Consistency is a property used in ASTM C187 to establish the setting properties of cement. It is also a measure of wetness and fluidity.

Define Workability (cement)

Workability is the ease of how a mixture can be handled from mixer to the fixed structure.

What is slump and how is it measured?

Slump is a result of a slump test that can be used to measure characteristics of workability. You fill and pack a mold, remove the mold, and measure the change in height due to the material “slumping”.

What is Air-Entrainment?

This is when a measured amount of air is added into a cement mix, usually 3-8%, to allow air pores to form. This results in a mixture resistant to freeze/thaw damage.

What is Freeze/Thaw Resistance?

This is a material’s characteristic to resist water entering voids and causing damage due to freezing/thawing cycles. It can be increased by air entrainment.

What is the average weight of a sack of cement in the US?

I sack = 94 lbs

If the W/C ratio = .55, with 270 lbs of water, how much cement is needed?

W/C = 270 lbs/ X lbs = .55

X lbs = 490.9 lbs

What is the primary reason to provide reinforcement in concrete?

Concrete has great compressive strength but has awful tensile strength. Therefore, reinforcing materials are added to improve the tensile capability of the concrete.

What is the bulk density of cement?

B = 1440 kg/m³ (from google)

Name two common chemical admixtures.

Calcium Chloride (accelerant)

Calcium Nitrite (accelerant)

What advantages come from adding fly ash to concrete?

Fly ash improves placement, workability, and pumping of concrete.

Give two reasons for adding superplasticizers to concrete?

They increase the slump/workability of concrete.

They reduce the W/C ratio, needing less water, while preserving high strength.

What are 3 considerations in mix design?

Workability, Strength/Durability, and Economics

Draw a typical graph of Compressive Strength VS W/C Ratio

Do and example of cement ratio and weight calculations.

In the mix procedure, which property controls the w/c ratio?

The main property that controls w/c ratio is needed compressive strength.

What property controls the amount of cement?

The W/C ratio

Define Curing

Curing is any procedure that maintains proper moisture and temperature to insure continuous hydration for proper strength development.

What is the tensile strength of concrete of a compressive strength of 4,000 psi?

ft = 6.7(fc)^1/2 , ft = 423.7 psi

Calculate Modulus Elasticity given compressive strength?

example on hw 2

Calculate 28 day strength from 7 day strength

example on HW 2

Calculate expected average strength given specified strength.

example HW 2

Show position of reinforcement in a concrete cantilever beam.

What are the two most important pieces of information inscribed on the surface of a reinforcing steel bar?

Steel Type and Bar Size

What is the purpose of adding fibers to concrete?

Fibers are added to reduce early age shrinkage cracks.

Describe the effects of creep and shrinkage.

Creep causes the concrete to deform over a period of time due to a constant load. Shrinkage causes the concrete to crack and may cause differential volume throughout project.

Go through all 10 Steps of calculating Concrete Mix

What are the three commercial forms of iron products?

Wrought Iron, Steel, Cast Iron

Explain the differences between wrought iron and cast iron.

Wrought iron has the least amount of iron whereas cast iron has the highest amount. Wrought iron is the only iron containing slag in its final form.

Explain the effect of carbon on steel and ductility of steel.

As carbon content increases within steel, its hardness, strength, and abrasion resistance also increases. But, ductility, toughness, and impact resistance all decrease with increase in carbon.

Define Yield Point

Yield point is the first stress at which an increase in strain occurs without an increase in stress.

Define Tensile Strength

Tensile strength is the maximum stress that a material can bear before breaking.

Define Modulus of Elasticity

Modulus of Elasticity is the ration of stress to strain below the proportional limit.

What is the yield stress of grade 50 steel? (Can use tables)

Sigma y = 50 ksi

What are the advantages of using high strength steel?

Designs tend to be more economical and will lead to lighter sections.

What are the three forms of reinforcing steel?

Plain Bars, Deformed Bars, Plain and Deformed Wire Fabric

What is the cross-sectional area of a No. # bar?

Diameter = #/8 in, so the area without the ribs uses this. For nominal area, tables give values.

Aggregate Definition

Granular material when bounded together into a conglomerate mass by cement forms concrete or mortar or alone as a base course.

Define the material property, Hardness

Hardness is the resistance to penetration

Fine Aggregate Diameters Range (#<x<#)

75 microns < x < 4.75 mm

Coarse Aggregate Diameter Range ( # < x < #)

4.75 mm < X

Example of a Fine Aggregate

Sand

Example of Coarse Aggregate

Gravel

Define the material property, Durable

Ability to withstand deterioration from weathering elements ( mainly water and other chemicals)

Define the material property, Porosity

Relates the number of pores to the total volume of rock

Define the material property, Absorption

Ability to retain water

Define the material property, Density

Relates mass to volume

Define the material property, Specific Gravity

Relates density of material to density of water

Absorbed Moisture

Moisture within pores

Surface Moisture

Moisture on the surface

Define Saturated Surface Dry (SSD)

When the pores are filled with water and the surface is dry.

What is Void Content?

It is the volume of voids out of the total volume of a sample.

What happens to the elastic modulus of concrete as the elastic modulus of aggregate increases?

E of concrete also increases.

Define Strength

Maximum compressive and tensile strength

Define the characteristic, Freeze Thaw

Resist cyclic freezing and melting

Define the characteristic, Abrasion Resistance

Resist wear and won’t erode

Define Well Graded Aggregates

Contains high, intermediate, and smaller sizes of aggregate.

Define Poorly Graded Aggregates

Consists of only one size of aggregate.

Define Maximum Aggregate Size (sieve analysis)

Smallest opening size through which the entire sample passes

What is the max aggregate size for non-reinforced plain concrete?

1/5 in of the narrowest dimension.

What is the max aggregate size for reinforced concrete?

¾ X the clearance distance between bars

Define Fineness Modulus

Average size of the aggregate in the sample.

Why do we use concrete?

Resistant to water and chemicals, easy to form, economical, less energy input, waste can be used as aggregates and fillers, sustainable

What are some uses of concrete?

Foundations, Pavements, Walkways, Storage Tanks, Dams, etc.

What is the three requirements for good concrete?

1. Quality

2. Workability

3. Economical

What makes concrete quality?

Strength, Durability, and Dimensional Stability

What is included in the workability of good concrete?

Transportation, plasticity, mobility, and slump

What can make good concrete economical?

Reduce cement and admixture, workable and quality at low cost, local materials, and low energy demand

Define Cement

A material that binds/unites like glue concrete, mortar, and grout

What can be a drawback of Portland Cement use?

High CO2 emissions resulting in green house gases

What are the characteristics of the compound Tri-Calcium Silicate when used in Portland Cement?

Early strength, early heat of hydration, and rapid hydration

What are the characteristics of the compound Di-Calcium Silicate when used in Portland Cement?

Hardens slowly, responsible for strength increase at later stages, and gives off the least heat during hydration

What are the characteristics of the compound Tri-Calcium Aluminate when used in Portland Cement?

Rapid hydration, gives off most heat during hydration, can not be used if hydration is not controlled

What are the characteristics of the compound Tetra-Calcium Aluminoferrite when used in Portland Cement?

lowers heat required during manufacturing, reduces needed amount of tri-calcium aluminate

What is the order of hydration speed for the Portland Cement Compounds (slowest to fastest)?

1. Di-calcium Silicate (Slowest)

2. Tri-calcium Silicate

3. Tetra-calcium Aluminoferrite

4. Tri-calcium Aluminate (Fastest)

What is Hydration?

Hydration is when water mixes with cement, causing hydrates of compounds to from giving hardness and strength to the mix

What compounds does the strength from hydration depend on?

Tri-calcium Silicate and Di-calcium Silicate