Final

Explain what efflorescence is and how it can be mitigated

- Efflorescence is the deposit of a white substance on a masonry wall. Brick has salt mixed with clay. When it rains and absorbs water it breaks down the salt and when water evaporates it comes to the surface taking the salt with it and the water evaporates but leaves salt behind. To mitigate it you can apply a water-repellent coating to the surface can help reduce the amount of water that enters the material and choose higher-quality of bricks that don't have salt

What is soft story and how should it be prevented?

- When a shear wall is removed from a story of a building it is a soft story. -Can be prevented by continuing the wall through the height of the building -Or It can be prevented with a heavy transfer structure

The compressive strength of concrete is generally measured

-28 days after casting the concrete in a test specimen.

Masonry grout has a slump of approximately

-8-11 in -For CMU concreate it is zero

If a CMU wall is vertically reinforced at 16 in. on centers, which of the following units will you recommend for use in the wall

-A unit -If 8 in, use H unit

Briefly list one advantage and one disadvantage of lightweight CMU units over normal weight units.

-Advantage: Lightweight units reduce the dead load on a structure, and they are easier to work with. Better sound resistance and fire rating -Disadvantage: lightweight aggregate costs more so lightweight units are generally more expensive than normal-weight units. Lightweight CMU are also weaker

What is air-entrainment of concrete?

-Air entertainment increases the durability of concrete against freezing and thawing. -When concrete is poured there has to be extra water put in it so it is workable which is why there are voids when water evaporates. During freezing weather, the absorbed in voids water turns into ice and expands. To reduce freeze-thaw damage, tiny particles of air are introduced in a concrete mix, referred to as air entrainment. As the absorbed water in concrete expands on freezing, the entrained air relieves the pressure from voids that are filled with water when they freeze -water ratio is .4 -Either add it to mixture to concrete or get cement that has it mixed in

In a one-way joist floor, if the supporting beams are deeper, the cost of the formwork will be high. Briefly explain how it is possible to construct beams with the same depth as joist

-By providing post-tensioning in beams. This will make beams stronger without the need for them to be deeper. -By constructing pre-stressed beams. Can also use double T beams if post-tension is not enough

Briefly define "Reinforced-Masonry Frame".

-Combination of vertical reinforcement grounded cells and bond beams which creates a frame for a building -Vertical reinforcement and bond beams act as columns and beams to provide integrity to building so when lateral loads are applied the building moves as one unit. -The structure needs to have integrity to building so everything can connect together. Do this by providing columns and beams. This creates the frame of building, so the floors and walls are connected.

List two reasons why concrete cover is needed for the steel reinforcement

-Corrosion prevention and fire resistance -Want to keep water away from steel reinforcement so corrosion doesn't happen -Protects steel reinforcement from high temperatures in case of a fire

Explain why curing of concrete is necessary.

-Curing of concrete is adding moisture to concrete continuously. -*Curing not only increases the strength of concrete, but also reduces its permeability to water. A well-cured concrete is denser and, hence, stronger and more durable.* -Cover it with a blanket and spray water. Do this because some water will evaporate

Per ASTM standards, facing bricks are classified as Types FBS, FBX and FBA. Which of these types has the most stringent requirements for dimensional tolerance, chippage and warpage?

-FBX -FBX: Special and has higher quality for requirements -FBS: Standard requirements -FBA: Architectural

A lintel over an opening in all masonry walls is always designed to carry the load from triangle-shaped superimposed masonry

-False -Only happens with arching action

1. Bricks that are highly absorptive may need to be wetted right before being laid in the wall

-False -Should wet the day before so outside of brick is dry and inside is wet

List two methods to increase fire-resistance and sound-insulation of CMU wall?

-Fully grouting the cells -Using lightweight aggregate gives a higher fire-resistance rating for the same equivalent thickness than a wall with CMUs containing normal-weight aggregate. -Increase thickness of wall

Why is it important that concrete should be placed in position carefully and not thrown from a large distance

-If concrete is not carefully placed in the forms or if it is compacted excessively, larger aggregates settle down and smaller ones rise to the top. The segregation of reduces its strength. -Prevent segregation and bleeding of concrete

Explain why a running-bond wall has higher horizontal bending strength than a stack-bond wall, whereas the vertical bending strength of both walls is equal

-In stack bond only vertical joint will resist but in a running bond there is vertial joint and sliding resistance -A stack-bond wall is much weaker in horizontal bending than a running-bond wall because the continuous head joints open easily, presenting little resistance to horizontal bending. In a running-bond wall, the masonry units have to overcome the shear (sliding) resistance at the bed joints before the head joints can open. A running bond can withstand higher bending loads because of the patter that it creates because the courses are interlocking which is why when they move horizontally they slid with each other. The pattern also distributes the load more evenly. -Vertically they can both withstand the same amount of loads because the compressive strength is the same for the bricks in a running bond and a stack bond. Compressive strength is a function of the vertical bending strength

What is the purpose of removing all domes around the columns in a waffle slab?

-Increase strength of slab against punch failure -To increase shear strength. The thickening of the slab at the columns provides shear resistance (against the slab punching through the columns)

1. List two means of controlling shrinkage in CMU walls

-Joint reinforcement -Control joints

What is lightweight structural concrete? (2points) What is the application of lightweight structural concrete? (2points) What are the advantages and disadvantages of using lightweight structural concrete? (2points)

-Lightweight structural concrete uses lightweight aggregate, for example, expanded shale -Lightweight concrete is used in beams and slabs (floor) of high-rise buildings. Normal weight is used as columns -Advantage: reduces overall dead load on building which reduces wind and earthquake loads, requiring a smaller foundation, saving money -Disadvantage: High-strength concrete is difficult to obtain using lightweight aggregates. It is weaker than normal weight

Briefly explain two methods of connecting steel reinforcement to provide reinforcing bars with required length. (2points) Which one addresses the congestion issue?

-Mechanical coupling and lap splicing -Mechanical couples are used when lap splicing causes too much congestion -Lap splicing includes overlapping two reinforcing bars and tying them together with a wire. The concrete then works as a glue to make them function as a continuous strip. -Mechanical couples involve joining the ends of two reinforcing bars using a coupler

Epoxy-coated bars are generally used in

-Parking garages built in cold climates. -In parking garage bars are exposed to weather condition -Cras can bring in chemicals and water -water can get into small cracks and when it freezes it will cause more cracks

List three reasons for providing ties in a concrete column

-Prevent buckling of longitudinal columns -Increases compressive strength of column -Increases shear strength of column -If lateral load is applied to building the tires will provide shear resistance and add shear strength to column -If a load is applied to a concreate column it will start bulging but having ties will provide confinement to concrete. Increase compressive strength

List two CMU units that are used in control joints instead of plain-end units.

-Projecting face shells -Slash units

Describe the difference shoring and reshoring.

-Shoring: Putting up vertical supports for the formwork so concrete can be placed -Reshoring: After concrete has gained 70% of strength The formwork for the concrete is removed and shors are placed back under to act as a support for the concrete so no creep or deformation will happen since the concrete hasn't gained all of its strength yet

What is the importance of Initial rate of absorption of bricks

-Shows how much water can be absorbed by bricks -if IRA > 30, bricks should be wetted before laying -If bricks are too porous, they can suck too much water out of the mortar, leaving insufficient water for the hydration reaction. This can weaken the mortar and the wall.

A masonry unit that has 20% voids (e.g., 20% core holes area) is referred to as a

-Solid unit -0% voids it is 100% solid -A Hollow unit is more than 20%

Discuss the importance of the water-cement ratio in concrete. (2points)

-The water-cement ratio will tell the workability of concrete. Reduce strength but increase workability -*The strength of concrete is inversely proportional to w-c ratio so water should contain the smallest amount of water it can have* -Having a low amount of water gives a concrete that will not completely flow in the form and will require careful compaction. Having too much water means there is too much water which will reduce concreate strength because as water evaporates it leave voids and concrete could bleed reducing the strength. -Adding water reducing agent reduces the water but also increases workability

Explain why the walls in a traditional masonry structure had to be extremely thick.

-They had to resist the heavy dead loads and had to be structurally sound to *resist high winds* and they didn't have steel reinforcement. *The walls had to be thickened at the base to support all the live and dead loads of the floors above it*. Increasing the thickness was the only way to increase the strength at that time

Briefly explain why slump test should be done in the construction site

-To measure the workability of concrete -A good concreate mix should be easy to pump, place, and compact, in other words it should have good workability. A slump test will determine the workability of concrete. A low value of slump gives a concrete that will not completely flow in the form and will require careful compaction. Having too high of slump means there is too much water which will reduce concreate strength because as water evaporates it leave voids. It is important to know the slump of concreate so it can be adjusted if its too high or too low to have good concrete.

Describe the importance of lime in both wet and hardened mortar. What is the disadvantage of adding lime to mortar?

-Wet: Lime improves its workability and water retentivity. A mortar without lime is coarse and less workable. -Hardened: *Lime improves the water resistance of the wall, more watertight*. A wall built with Portland cement and lime mortar is more watertight than a wall built with only Portland cement mortar. Lime improves the elasticity of hardened mortar. Lime also provides an autogenous healing (self-sealing of small cracks) property to mortar. -Disadvantage: Lowering strength of mortar

Why is a single-Wythe wall often terminated with a soldier course at the top?

-Without the soldier on top the holes in the bricks are exposed so water can fill inside of them and freeze and cause damage to the bricks. The soldier covers the holes so no water or anything can get in on the stretcher course

In general terms, which of the following stones is considered most durable?

-granite -it is the densest

Explain why granite is the most durable of all building stones

-it is the densest -It is an igneous rock and the minerals in it give it strength against heat, scratches, chipping, and staining

Double-tee units are used where the spans are ___________ and cannot be provided economically with _________ slabs.

-large - Site cast or hollow core

List 4 ways through which vertical reinforcement of the walls improve the performance of the building under loads.

-reduce horizontal deformation of building under lateral loads -Vertical reinforcement helps reduce tension caused by overturning of wall from lateral loads: resist uplifting force because it is anchored into foundation -Increase strength of wall -Increases durability - increases the sliding resistance of the wall to in-plane lateral loads (as in a shear wall), reducing horizontal displacement between floors. Vertical reinforcement connects the wall throughout it's height so it moves together

Steel reinforcing bars, generally used in concrete, have a yield strength of

60 ksi

The term flying form refers to

A large formwork assembly for floor and roof slabs.

Arching action occurs in a masonry wall with

A running-bond pattern -45 degree flaring of the load in masonry walls is referred to as the arching action because the phenomenon is similar to the behavior of an arch, which transfers the gravity loads placed on it to side abutments. Arching action occurs in all masonry walls in which the head joints in one course are (sufficiently) staggered from those in the upper and lower courses. 3 conditions -distance should be 12 inch from top of triangle to load -running patter is used -wall on either side of opening is strong enough to withstand the load The lintel over the opening, therefore, receives less load

Briefly explain the application of (A) Isolated concrete slabs (2points), and (B) Stiffened concrete slabs (2points)

A) They are not apart of the foundation and the slab is only used as a floor. used on stable, undisturbed soils. Can't have slab on unstable soil. When foundation settles it won't take slab with it B) Stiffened slabs are part of the foundation and are stiffened with reinforcement and use posttension and ribs in both directions. Slab is a part of the foundation and has to resist movement of soil

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

A. Member thickness. B. Type of coarse aggregate in concrete. C. Concrete cover for corrosion protection. Everything above

What is the reason for providing hooks on reinforced concrete members? (Choose all that apply

A. To increase embedment length B. To provide anchorage

The primary purpose of joint reinforcement in a CMU wall is to

Absorb the tensile stress in the wall caused by the shrinkage of units To control shrinkage in CMU: Add joint reinforcement and control joint

List two advantages and two disadvantages of pre-stressed reinforced concrete members

Advantage 1)Hight will be smaller. Can have higher floor to floor hight 2)Lighter weight: the reduction in the dimensions (because it is pre-stressed) of structural members, *resulting in smaller dead loads* 3) reduced cost of framework because you don't need it Disadvantages 1)higher cost of tendons compared with reinforcing bars and transportation costs 2)the need for greater quality control and a more skilled labor force.

A bond beam in a masonry bearing wall building is required for structural reasons.

At each floor level, and roof level -put on parapet to anchor cap to wall

The keyway between precast-concrete hollow-core slabs is generally

Both a. Grouted b. Reinforced with horizontal steel dowels

Which one of the following joints is extended through the entire depth of concrete slab

Both Construction joint and Isolation joint Isolation Joint: provided to ensure that the slab is isolated from the building's structural components so that their movement (creep, foundation settlement, etc.) is not transferred to the slab -A construction joint (also called a cold joint) is a nonmovement (accommodate shrinkage of concreate and relive stress) joint in a large concrete slab. This is used when the concrete cannot be placed in one continuous operation. The time interval between two concrete placements may be a few hours or several days. Uses a shear key

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

Both pumping and buckets

*Which of the following mortar joint profiles should be specified for an exterior wall?*

Concave joint -Water can not sit on concave joint -It is compressed so it has high strength

Everything in the following concrete mixtures is the same except the size of course aggregates. Which of the flowing needs least cement?

Concrete mix with coarse aggregate size of 3 in

In a running-bond wall

Each course consists of stretchers

White Portland cement is generally weaker than normal (gray-colored) Portland cement

False

A well-graded coarse aggregate is one with uniform particle sizes

False -Needs to have wide range of aggregate size

Control joints are cut into concrete slabs-on-grade to help control cracking, and they extend through the entire thickness of the slab

False -Their purpose is to provide weakness in the slab at predetermined locations to force the slab to crack there. -Crack provides shear interlock between adjacent sections of the slab, referred to as aggregate interlock.

Reducing water ------------- strength of concrete

Increases

Double Tee precast concrete slabs are usually supported by __ beams

Inverted-tee

Some architects and engineers prefer to specify low-lift grouting in masonry walls because

It provides better quality control

Masonry grout is a mixture of

Lime, cement, aggregate and water -Grout and mortar difference: Mortar has less water, because if it has too much water it will fall off wall. Grout needs more water because it needs to fill the cells

Which of the following CMU shapes has a U-shaped profile in its vertical cross section?

Lintel unit

Which of the following materials increases the mortar's compressive strength?

Portland cement

Which of the following statements is not true?

Posttensioning is generally done at the precaster's plant and yields a posttensioned concrete member.

The commonly used floor system in high-rise and mid-rise masonry bearing wall buildings in north America is

Precast-concrete hollow-core slabs -They are lighter and require less material -Don't use if spans are large or loads are heavy

The primary reason for providing core holes in bricks is to

Provide uniform drying and firing of bricks

Where are bond beams required in a typical load-bearing masonry structure

They are below each floor level and roof level in all exterior walls and all interior load bearing/shear walls and at the top of the parapet

After the concrete has been placed in the form, consolidation of concrete for a longer than required time by standard codes causes the bleeding of concrete

True

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

True

The keyway between precast-concrete hollow-core slabs run perpendicular to the bearing walls

True

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

True

The term prestressed concrete refers to both pretensioned and posttensioned concrete

True -Concrete is under initial compressive stress before loads are applied

In a posttensioned elevated concrete floor, prestressing tendons are combined with conventional steel reinforcement

True -The steel reinforcement will control the shrinkage, if you don't need reinforcement you just need to provide a nominal amount of reinforcement

Bond beams in a CMU wall can be used to serve the same purpose as joint reinforcement

True -joint reinforcement can't do the same function of bond beam and resist loads

The most commonly specified type of Portland cement

Type I/II.

Portland cement used in precast concrete members is generally

Type III

Referring to a masonry wall as reinforced-masonry wall implies that the wall contains

Vertical reinforcing bars

A high-strength concrete generally requires a

Water-reducing agent.

*The flexural tensile bond strength of a masonry wall is a function of* -the material's ability to resist deformation under load.

a. The compressive strength of mortar b. The type of masonry units c. The quality of workmanship d. The curing of mortar