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70 Cards in this Set
- Front
- Back
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How much does concrete weigh per Cubic Foot? |
-150 lbs |
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How much does 1 bag of cement weight? |
- ~94 lbs |
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What must you ensure your form is before you pour your concrete? |
-Square -Straight -Level |
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What is a slab form constructed out of? |
- 2x wood |
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How far appart should stakes be placed on a slab form? |
-2 to 4 feet |
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What are the 6 components of a continuous wall form? |
-Sheathing -Studs -Wales -Tie wire -Braces -Spreaders |
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What type of nails should be used when making a form? |
-Form Nails |
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What should be applied to a form to aid in the removal of the form? |
-Oil or oil alternative such as asphalt paint, Varnish, or linseed oil. |
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What is a vapor barrier and what does it do? |
-Any number of materials placed over drying concrete to prevent the unwanted loss or gain of water. |
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In what ways is concrete strong and weak? |
-Strong in compression -Weak in tension |
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In what ways is rebar strong and weak? |
-Strong in tension and sheer strength -weak in compression |
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Why is rebar added to concrete? |
-To help the concrete to have better tensile strength and prevent cracking under pressure. |
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How many sizes does rebar come in? |
- 11 |
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How much does the diameter of a piece of rebar increase by moving up one number? |
-1/8th of an inch |
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What is the diameter of a piece of rebar numbered 11? |
-11/8 inches or 1 3/8 inches |
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How should rebar be joined together in a form? |
-Overlapping, either vertically or horizontally, with offset joints to stagger weak points. -Never end to end |
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What are the 4 ways to cut rebar? |
-Rebar cutting set -Reciprocating saw -Hacksaw -Bolt Cutters -Knife hand |
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How much concrete should be placed around each piece of rebar? |
-1 1/2 to 3 inches depending on the size of rebar and what the blueprints call for. |
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How far appart should rebar supports be placed? |
-5 to 6 feet appart |
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What is used to secure the supports to the rebar? |
-18 guage wire |
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In what two ways can you buy wire mesh? |
-In sheets or rolls |
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What is the primary purpose of wire mesh in concrete? |
-To control shrinkage and contraction while providing reinforcement |
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What is used to cut wire mesh? |
-Bolt cutters |
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How far should sliced wire mesh be overlapped? |
-One square plus 2 inches |
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What are some advantages to concrete as a building material? |
-Economical -Versital -Can be cast into almost any desired shape -Produces lasting structures -Will support almost any weight if placed correctly -High compressive strength -Low maintenance |
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What are some disadvantages of concrete? |
-Low in tensile strength unsupported -Contracts and expands -It is porous to a degree |
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-What are the ingredients of Concrete? |
-Water -Portland cement -Aggregates |
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What are the two aggregates added to cement to make concrete? |
-Sand (Fine aggregate) -Gravel (Course aggregate) |
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How many types of cement are there? |
-5 |
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What are the main types of cement? |
-Type 1: Normal Cement -Type 2: Modified Cement -Type 3: High Early Cement -Type 4: Low Heat Cement -Type 5: Sulfate Resistant Cement |
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What is Type 1: Normal Cement used for? What is it's cure time? |
-General purpose non-critical construction -Ex: Paving, sidewalks, buildings, and bridges -Cures in about 28 days |
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What is Type 2: Modified Cement used for? What is it's cure time? |
-Typically used in drainage structures with higher than normal sulfate levels -Cures in about 45 days |
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What is Type 3: High Early Cement used for? What is it's cure time? |
-Typically used in cold environments. Permits fast form removal -Cure time is usually 7 days or less |
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What is Type 4: Low Heat Cement used for? What is it's cure time? |
-Used in very large structures where the heat of curing could damage the structure - Ex: Dams -Cures in about 90 days |
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What is Type 5: Sulfate Resistant Cement used for? What is it's cure time? |
-Used where soil or ground contacting concrete has a high sulfate content. Resists sulfate degradation. -Cures in about 60 days. |
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What percentage of concrete is aggregates? |
-66 to 78 percent of concrete volume |
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How are sieves measured? |
-Larger sieves are given an inch designation based on the size of the square holes -Smaller sieves are given a number based on the number of square holes per linear inch. |
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What number sieve will sand pass through? |
- Number 4 |
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Why are aggregates added to cement? |
-To increase strength -To minimize shrinkage -To cut down on cost |
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Where can aggregates be found? |
s -Streams and riverbanks-Valleys or Alluvial fans riverbanks-Valleys or Alluvial fans riverbanks-Valleys or Alluvial fans -Valleys or Alluvial fans |
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What are the desired properties of Aggregates? |
-Partially rounded -Hard -Durable -Well graded -Free of organics |
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What is Air Entrained Concrete? |
-It is concrete with tiny, well distributed, completely seperated air bubbles. |
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Why is Air Entrained Concrete used? |
-To produce concrete that is resistant to freezing and thawing erosion as well as chemicals used for frost removal. |
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How much water does concrete contain? |
-15 to 20 percent. |
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How much is the strength of concrete degraded when using salt water? |
-10 to 30 percent |
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What are the proportions for concrete? |
-One part cement -Two parts sand -Three parts gravel |
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What are the two ways to mix concrete? |
-By hand -With a mixer |
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What is the capacity of the mixing machines we use? |
-12.5 cu. ft. |
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What is the sequence for mixing concrete? |
-Add gravel first with a small amount of water -Add sand second -Add cement third -Add water slowly and as needed to obtain desired consistency. |
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What is a slump test? |
-A test used to measure the consistency of the proportions of a concrete mixture |
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How many times do you pack the concrete in a slump test? |
-25 times per layer (per 3rd of the form) -75 times total |
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What is the sequence for hand mixing concrete? |
-Add 1/2 Sand first -Add cement over sand -Add remaining sand over cement -Blend together -Once done blending, level off and add gravel -Make trough in center and add water to trough -Mix until water is absorbed -Add water as needed and mix until mix has a uniform consistency |
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What is the capacity of a mixing truck? |
-7-12 cubic yards |
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How do we minimize concrete segregation? |
-Place, never throw, concrete -Do not allow concrete to fall more than 3 feet -Place concrete in 6 to 12 inch lifts |
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What is consolidation? |
-Vibration or agitation of concrete -Helps to achieve maximum density for concrete -Prevents rock pockets and air bubbles |
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How is a vibrator applied to concrete? |
-Vertically never horizontally -In 18 inch intervals |
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How long should Non-Air Entrained Concrete be vibrated? |
-10-15 sec |
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How long should Air-Entrained concrete be vibrated? |
-5 to 10 sec |
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What are some methods of hand consolidation? |
-Spading -Tamping -Puddling sticks |
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What is screeding? |
-Using a board, mechanical screed, or other strong, straight material to level off the surface of the concrete to the desired height. |
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How do you use a screed? |
-In a sawing motion, moving forward very slowly. |
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What are the types of concrete finishes? |
-No finish -Floated finish -Broom/Wire brush finish -Trowel finish |
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When do you float the surface of concrete? |
-After screeding to smooth the top of the concrete |
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When do you edge concrete? |
-Immediately after floating while still wet |
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When do you trowel concrete? |
-After concrete has no water/pooling at its surface and is semi hard. -Delay as long as possible without letting concrete harden too much. |
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What are the 3 types of concrete joints? |
-Isolation -Control -Construction |
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What is the purpose of an isolation joint? |
-To isolate two pieces of concrete so expansion and contraction do not crack or adversely effect eachother. -Allows for movement. |
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What is the purpose of a control joint? |
- It is a cut in the concrete to create a weak point to control and/or stop cracks. -minimum 1/4 inch |
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What is a construction joint? |
-A keyed or doweled joint used to allow some load transfer between two pieces of concrete that were cast at different times. |
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7 Types of moisture barriers |
-Burlap cloth -Straw -Puddling -Curing compounds -Waterproof paper -Plastic -Moist earth |
