Concrete (Tony) Flashcards
Entrained air does what?
It improves placeability, workability, and pumpability, as well as increases slump and reduces bleeding
1/2 of the 28thday strength is called what?
3 day compressive strength
2/3 of the 28thday strength is called?
7 day compressive strength
20 degree increase in temperature reduces setup time by what how much?
50%
A chemical agent that slows down a chemical reaction is called?
Retarder
Concrete cover specifies what?
Minimum distance between reinforcement and outer surface of concrete
When are concrete forms removed?
Specified by engineer
Concrete Saw Joints should be cut between ____ and ____ hours after concrete is poured.
First 6 - 18 hours and never more than 24 hours after pouring
How much does concrete weigh?
150 lb/CF
Concrete, mixed in a transit mixer, should be delivered and discharged within ______ or before the drum has revolved _____ after the introduction of water to cement and aggregates?
1 ½ hours or 300 revolutions
Curing cylinders in job site should be kept in box at what temperature?
60-80 degrees
When does concrete curing start?
Immediately
Epoxy coating on rebar is used for?
Corrosion protection
Fiber Tube Forms require?
Stiffeners
Type I
Normal
Imperial Rebar sizes are measured in what?
Inches
Imperial Rebar sizes increase in what increments?
1/8 inch
Last step in concrete slab work is?
Edging
What is the maximum drop of concrete?
5 ft
Metric rebar system is measured in what?
mm
Never pour concrete on what?
Frozen ground
Plastic shrinkage cracks are caused by what?
Rapid evaporation
Progressive loss ofconcretemass due to mechanical degradation such as friction, grinding action, impact, overloading and local crushing is called?
Abrasionofconcrete
Pump mix stone should be?
Rounded
Rectangular steel piece which is wrapped around top and bottom bars of the beams and helps hold in place the primary reinforcement bars is called?
Stirrup
Stirrup tolerance is?
Equal to +/- 1 inch
Smallest Rebar size imperial diameter is?
1/4 inch
Smallest Rebar size imperial number is?
2
Smallest Rebar size metric number is?
6
Smallest Rebar size metric number diameter is?
6 mm
Step before last in concrete flat work is called?
Troweling
The addition of this material speeds up setting time and causes the cure time to start earlier.
Accelerator
The use of stirrups is needed to prevent the columns and beams from?
Buckling
These chemicals are compounds that enable the production ofconcretewith approximately 15% less water content.
Plasticizers
The strength ofconcreteincreases when?
The water to cement ratio decreases.
These nailsare used for temporary construction wherenailremoval is required, such asconcreteforming and scaffoldings.
Duplex
This kind offootingis used to support single-columns and when the columns are arranged relatively at long distance. This the most inexpensive kind offooting.
Isolated Footing
This material used inconcreteimproves the workability of concrete, and the strength and durability of hardenedconcrete. This material is called?
Fly Ash
This test measures the consistency of fresh concrete before it sets. It is performed to check the workability of freshly made concrete, and therefore the ease with which concrete flows. It can also be used as an indicator of an improperly mixed batch. The test is used to ensure uniformity for different loads of concrete under field conditions.[1]
Slump test
Troweling too soon will cause what?
Surface to be rough
What are the 5 types of concrete forms?
1) Wooden CF
2) Insulated CF (ICF)
3) Foam CF (for decoration)
4) Concrete wall forms
5) Steel Forms
Wht are the 3 types of concrete joints?
Contraction, Construction, Isolation
Joints where construction needs to stop such as between work days are called what?
Construction Joints
Exterior joints designed to prevent water infiltration are called?
Wrap joints
What is the most typical release agent?
Diesel oil
What are temporary concrete supports called?
Shoring
What controls drying of concrete?
Curing
What determines quality of concrete?
Water Cement Ratio (Weight Ratio)
What does Non-Destructive testing test?
Strength and Durability
What do Test Cylinders test?
Compressive Strength
What do you do before removing shoring?
Get Cylinder Test Results
What increases abrasion resistance?
Strong Stone
What is considered cold weather for concrete?
Below 40 degrees
What is the purpose of concrete vibrator?
To Consolidate concrete
Another purpose of concrete vibrator is to?
To make stiff concrete more fluid
What knocks down highs and lows?
Bull float
What should be done before concrete is poured in a slab and why?
Wet down the slab to prevent water loss
____ is air that is naturally ____ in all concrete, occurring without the use of an agent. These bubbles or voids have no consequential positive or negative effect on the performance of concrete
Entrapped air
____ air is purposely put into the concrete by the addition of an agent. These bubbles are microscopic in size.
Entrained air