CM final

List various types of Portland cement and where they are typically used

1- genereal purpose (no special req.) 2- modereate sulfate resistant and moderate hat of hydration 3- High early strength -used in precast element, High early strength like in cold weather 4 -low heat of hydration - used in massive civil engineering structures. 5- Sulfate resistant - used where high sulfate resistance is req

The yield strength of prestressing steel is

270 ksi yield strength

High-strength concrete is defined as concrete whose compressive strength is greater than or equal to

6,000 psi 6ksi

A reinforced-concrete, four-side-supported slab panel measuring 15 ft X 22 ft is

A two way slab. if you divide 22/15 =less than two if more than two =one way slab.

1. Concrete is made by mixing __________, _____ ___ and _______ __.

Aggregate, cement, water

What is air-entrained Portland cement? Where is it typically specified?

Air entrained portland cement - type of cement that to which air entraining chemicals are added. Excess amount of water will be evaporated after casting concrete leaves beehind some voids. These voids can be filled with water and if water freezes it can cause some damage to concrete. The pressure due to the freezing of water will be released due to the air pockets in the concrete

Concrete cures by a process of ________________.

Chemical Hydration reaction with cement and water

In a welded wire fabric mat that has a designation of 8 X 8-D4.0 X D4.0, the number 4.0 indicates that the wires are

Deformed wires, each with a cross-sectional area of 0.04 in^2 #4 indicates defomed cause letter D

The formwork used for a waffle slab has a

Dome profile.

Architectural precast concrete refers to concrete members used in building interiors

False

Everything else being the same, a concrete with a larger coarse aggregate requires less Portland cement and water paste to give the same concrete strength.

False Aggregate which has different sizes. or large variety of different sizes.

After the concrete has been placed in the form, it should be consolidated as much as is economically practical.

False, if you consolidate concrete more than required can cause bleeding of concrete. Done for specific amount of time according to standard codes.

Commonly used beamless concrete floors are

Flat-plate and flat-slab floors

In mixed precast construction, precast concrete members are generally used for

Floors

In site-cast concrete construction, shores are used

In elevated concrete slabs concrete slab is above surface of ground need short support under concrete slab.

Concrete reinforcing bars come in limited lengths. Explain how we ensure their continuity in a long structural element. Such as a column in a high-rise building or a long, continuous beam (Briefly explain two methods.

Lap splicing or using mechanical couplers lap splicing- connects reinforcement bars to each other and provide continuity. however they may produce reinforcement congestion. in heavily reinforced columns. Mechanical coupling- used instead of lap splicing when working in heavily reinforced columns.

What is lightweight structural concrete? How does it differ from normal-weight concrete? What are the advantages and disadvantages of using lightweight structural concrete?

Lightweight structural concrete - obtained using light-weight aggregate. commonly used lightweight aggregate is expanded shale. Used in floor and beams of high-rise buildings, and normal-weight concrete is used for columns. reduces dead load of building. lightweight concrete is not as strong as normal weight concrete.

Double-tee units are used where the spans are ________ and cannot be provided economically with __________ slabs

Long, site cast

The fire-resistance rating of concrete members is a function of

Member thickness - thicker means more fire resistant type of coarse aggregate- have different resistance against fire. Concrete cover for corrosion protection.

Pre-cast double Tees and bridge beams are typically _____________ concrete components

Pre-stressed

What is the function of stirrups in a column (mention 3 reasons for using stirrups)?

Prevent the buckling of the longitudinal reinforcement. increases shear strength of column increases strength of column by providing confinement.

The primary reason for using posttensioned concrete floors is to

Reduce floor depth. if apply initial compressive stress to concrete then it means you do not have to build as thick concrete floor.

In a one-way joist floor, the supporting beams run in one direction and the joists run in the other direction. If the spans in the two directions are unequal, the beams should preferably span along

Shorter direction. they will not bend as much.

Discuss the importance of the water-cement ratio in concrete

The more water you add to concrete the less strength concrete will have. The amount of water needed for complete water hydration reaction is almost 40 % of the weight of the cement, but add more than this because want enough workability.

Explain what concrete cover is and the functions it serves.

To protect steel reinforcement from corrosion, a minimum amount of concrete cover is req.

A well-graded coarse aggregate is one in which the size of all aggregate particles is approximately the same.

True

The rate at which concrete gains strength increases as the ambient air temperature increases

True

In a post-tensioned elevated concrete floor, pre-stressing tendons are combined with conventional steel reinforcement

True both reinforcement and conventional reinforcemnt pre-stressing tendons to build post tension reinforced concrete.

Pans used as formwork for one-way joist floors have a

U-shaped profile.

Which types of elevated, structured concrete floors use metal forms to create beams?

Waffle slab - Dome Pan and joist slab - cast concrete for beams.

Double-tee floors are commonly used

Where spans are in excess of 50 ft double tees are used when spans are long. Used to reduce deflection.

A flat slab floor consists of

a slab with drop panels at each column provided around each column to give some more thickness to slab to prevent punch-failure around columns.

____________ are cut into concrete slabs-on-grade to help control cracking

control joints

In a high-rise building, the concrete may be brought from the ground to the location of placement by

depending on size of concrete use buckets or pumping (pumping is better)

Explain what curing of concrete is, and why it is necessary.

increases the strength of concrete and reduces permeability to water. water cannot penetrate concrete. Resulting in a more denser and durable concrete.

Double Tee precast concrete slabs are usually supported by ___________ beams

inverted tee

Epoxy-coated bars are generally used in

parking garages built in cold climates required to protect concrete

The chairs used to support reinforcing steel bars are generally

plastic chairs or steel chairs which has plastic coated feet.

After forms are removed from an elevated concrete slab, ___________ is added to support the formwork above per the ______________ drawings

shoring, subcontractor's

What is slump test?

slump test is a measure of the workability of concrete. Done with fresh concrete

The most important reason for providing ties in a concrete wall is to

ties are generally not provided in concrete wall. ties in reinforcement column or beam provided to give enough shear strength to member.

Hooks are used

to make sure steel reinforcement has enough embedment, so theres enough length of steel reinforcement in concrete, so concrete does not slide under loads.

The term prestressed concrete refers to both pretensioned and posttensioned concrete

true concrete is under initial compressive stress before actual loads of building applied "pre-stressed"

Portland cement used in precast concrete members is generally

type 3

A vapor retarder is required under

under some interior concrete slabs-on-ground prevents water vapor to reach concrete slab and get into surface of building.

A high-strength concrete generally requires a

water reducing agent