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30 Cards in this Set
- Front
- Back
Four ingredients of concrete are: |
Portland cement Fine aggregates Course aggregates Water |
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Concrete is a mixture of: |
Cement paste and aggregate |
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Cement paste fills voids and acts as a ____ |
Glue/binder |
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Aggregates are precisely proportioned in order to: |
Reduce the amount of cement paste needed |
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Excessive cement paste results in: |
-Better workability -High shrinkage -Expensive batch |
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Insufficient paste results in: |
-Entrapped air -Weaker and increased porosity |
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The chemical reaction that happens when water and cement are mixed is: |
Hydration |
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Applications of type 1 (normal) cement: |
General construction such as floors, foundation walls, sidewalks, high rise structures |
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Applications of type 2 (moderate) cement |
Moderate danger of sulphate attack from ground water. Generates less heat. Massive concrete pours or hot weather |
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Applications of type 3 (High early strength) cement: |
High Early Strength: used where fast curing is needed (highrise columns). Can be used in cold weather |
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Applications of type 4 (Low heat of hydration) cement: |
Low heat of hydration: massive concrete pours (expansion and contraction is reduced furing pour) |
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Applications of type 5 (Sulphate resistant) cement: |
Sulphate resistant: used for concrete exposed to high concentrations of sulphates in soil or ground water. |
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Aggregates account for ____% of the total volume of concrete |
65% - 75% |
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Fine aggregates are typically equal to ___mm or smaller |
5mm |
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Coarse aggregates are larger than 5mm and typically between ___mm and ___mm |
10mm-40mm |
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Increased aggregate gradation results in a reduced: |
Amount of cement paste required |
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The maximum aggregate size of non-reinforced members (walls and footings) is: |
1/5 the smallest dimension |
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The maximum aggregate size of unreinforced slabs on the ground is: |
1/3 the depth or thickness of the slab |
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Maximum aggregate size of reinforced forms (foundation walls) |
3/4 of the spacing between the rebar and forms or the surface |
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Maximum aggregate size in general construction is: |
20mm-25mm (3/4"-1") |
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Most critical ratio of concrete: |
Water to cement |
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Porosity is the: |
Ratio of voids in the concrete to the total concrete volume |
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Excess water in concrete results in: |
Increased shrinkage and structural cracking |
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Excess bleed water (water that gets pushed to the top of a pour) results in: |
Weak, chalky surface |
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Mix ratio of finished concrete (floors, slabs or sidewalks) is: |
1:2:3 |
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1:2:3 ratio components: |
1 part cement to 2 parts fine aggregate to 3 parts coarse aggregate |
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How many premix bags does it take to produce 1 cubic foot of concrete? |
3 |
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How many premix bags does it take to produce 1 cubic metre of concrete? |
36 |
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Concrete gains 50% of it's strength in: |
3-7 days after pour |
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Concrete is assumed to be at full strength: |
28 days after initial pour |