Concrete Construction Flashcards
Before placing concrete, you should inspect all supporting members because wet concrete will always exert what type of pressure on them?
Hydrostatic
Nailing requirements must comply with directives?
Plans and specifications
Supervisors should inspect all forms before and after each pour.
True
When working with concrete, personnel should wear gloves and protective goggles and have their shirt sleeves rolled down to prevent what hazardous results?
Cement poisoning (lime)
When working with concrete, personnel should stand with their backs to the wind to prevent cement and sand from being blown into their eyes.
True
What term is used to refer to a temporary structure that can support its own weight and that of freshly place concrete, as well as the weight of materials, workmen, and equipment imposed upon it?
Formwork
As a supervisor of a form building crew, you should consider what factors as your principal objectives?
Economy, quality, and safety
Formwork may represent as much as what percentage of the cost of a concrete structure?
33%
Concerning formwork, in what areas will good judgment and ingenuity on the part of the supervisor help reduce costs?
- Selection of materials and equipment
- Planning fabrication and erection procedures
- Scheduling reuse of forms
Forms must be designed to meet what weight factor?
Total weight to which they may be subjected
Earth, metal, lumber, plywood, and fiber are the most commonly used types of form material.
True
The majority of all formwork involves concrete. Concrete ways a total of how many pounds per cubic foot?
150
For each inch of slab thickness, concrete slabs place a total load of how many pounds per cubic foot on the formwork?
12.5 pounds per square foot
In pounds per square foot of horizontal projection, what is the minimum recommended construction live load provision for the weight of crewmembers and equipment?
50
When powered concrete buggies are used in concrete operations, what is the minimum construction live load recommended for use in PSF?
75
What bracing technique is most often used to brace forms against lateral pressure?
Nailing a diagonal member and a horizontal number to a stud or wale with the diagonal member at a 45° angle to the horizontal number
Which of the following factors does not have an affect on lateral pressure?
Sulfate content
You have been given the assignment of determining the maximum concrete pressure for a form. The rate of placement is 5 ft./h and the temperature is 70°. What is the maximum concrete pressure for the form in PSF?
800
To determine the uniform load on a stud, you multiply the maximum concrete pressure by the maximum stud spacing. Then, by dividing the result by 12, you convert the answer into what unit of measurement?
Pounds per linear foot
To determine the time required to place concrete, you divide the height of the form by the rate of placement.
True
Braces are used against wall forms to protect from mishaps due to external forces. The value of the external force is estimated to be how many times the wall height in feet?
12.5
Designing wall forms and the bracing for them should be the responsibility of what person?
Project engineer
What is the first step in designing wooden forms for a concrete column?
Determine the materials available for sheathing, yolks, and battens.
In which of the following forms may reinforcing steel be used?
Bars or rods
To calculate manpower estimates, you must first estimate what factor?
Square footage of contact surface (SFCS)
Reinforced concrete refers to concrete containing steel to reinforce and absorb what type of stress?
Tensile and shearing
Reinforcing bars are hot rolled from steel recovered from which of the following sources?
Steel billets, railroad car axles, and railroad rails
When mixing properly, a good uniform batch of concrete should possess maximum values in durability, economy, and ______?
Strength
What type of mix is considered the simplest form of concrete patching?
1:2:4 Carpenters
When a very rich mix is needed because great strength is required, you should use what mix design?
1:1:2 mix
When a mix is required for large foundations or as a backing for masonry, you should use what mix design?
1:3:5
When large slabs and walls are to be poured, you should use what mix design?
1:2:5
You can use one of which of the following methods to achieve more control over the proportional quantities of the cement, water, and aggregate for a concrete mix?
Book, trial batch, or absolute volume
Construction crews in the field must convert the designed trial mix proportions into field mix proportions by adjusting the mix for moisture and ____?
Entrained air
Add mixtures are added to concrete, mortar, or grout immediately after mixing.
False, added before or during
What admixture is most commonly used in concrete mixtures?
Air entrained agent
The primary reason for using an air entraining agent in a concrete mix is to improve what property of the concrete?
Resistance to freezing and thawing exposure
When sampling for a strength test, you should get a sample of not less than how many cubic feet?
1
Samples taken from revolving drum truck mixers must be taken at a minimum of how many intervals?
3
In obtaining a sample of concrete from a paving mixer, it should be collected from at least how many portions of the pile?
5
You must take a sample to another location to conduct a Compressive strength test. The time lapse between taking and molding the sample cannot exceed how many minutes?
15
With how many strokes should you rod each layer of concrete placed in the compressive strength test mold?
25
The flexural strength of concrete is its ability to resist ____.
A breaking force
you have a concrete pad that has a length of 60 feet, a width of 15 feet, and a thickness of 6 inches. What is the volume of the concrete pad in cubic feet?
450
Test cylinders are cast in either metal or wooden molds.
False, Cardboard and metal
A total of how many layers of concrete should you place in the mold when preparing a compressive strength test specimen?
3
To calculate the number of cubic yards required for a pad, divide the cubic feet of the pad by what number?
27
Concrete specification most often require that batching be performed by volume.
False, by weight
How many rotations of the drum on a transit mixer at mixing speed are required to produce concrete of the specified uniformity?
70-100
Which of the following structures is not an example of a precast concrete structure?
Cast in place concrete wall
You should not continue to operate a mobile concrete mixer plant if the hydraulic oil temperature exceeds what temperature?
190°
What type of panel consist of two thin, dense reinforced concrete faced slabs separated by a core of insulating material?
Sandwich
Post tensioning is used if a unit weighs over 7 tons or is over how many feet long?
45
Conventional concrete weighs approximately how many pounds per cubic foot?
150
Depending on its intended use, the weight of light weight concrete falls within what range, in pounds per cubic foot?
90-120
Heavy weight concrete has a density of up to how many pounds per cubic foot?
400
What type of construction is a special form of precast concrete building?
Tilt up concrete
When building casting surfaces for precast concrete panels, you should use 3000 psi or higher reinforced concrete and ensure the slabs are at least how thick, in inches?
6 inches
What material is most often used for edge forms?
2 by lumber
Bond breaking agents are classified into what two types?
Sheet materials and liquids
A good bond breaking agent can be made by mixing 5 pounds of paraffin with how many gallons of kerosene?
1 1/2
When welded wire fabric (WWF) is used, dowels or bars are NOT needed between the columns and panels.
False
To achieve proper strength, cast panels must be cured just like any other concrete.
True
At the job site, what type of lifting attachments can be made from rebar?
Hairpins
