Competencia

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  • Publicado : 9 de febrero de 2011
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1) | Aggregate is granular material such as sand, gravel, crushed stone and blast furnace slag that usually occupies approximately    ?    of the volume of concrete. |
  |   | a) 30 to 40% |
  |   | b) 35 to 50% |
  |   | c) 40 to 60% |
  |   | d) 60 to 75% |

2) | Fine aggregate is material that passes the 4.75 mm (No. 4) sieve and is retained on the    ?    sieve. |
  |   | a) 75μm (No.200) |
  |   | b) 150 μm (No.100) |
  |   | c) 300 μm (No.50) |
  |   | d) 600 μm (No.30) |

3) | Individual percent (%) retained is the percentage of material contained between successive sieves, recorded to the nearest    ?   . |
  |   | a) 1/4 percent |
  |   | b) 1/2 percent |
  |   | c) whole percent |
  |   | d) two percent |

4) | The Fineness Modulus for thefollowing fine aggregate is    ?   .   Sieve data for Fine Aggregate |
Sieve Size | Total % Retained |
4.75 mm (No. 4) | 2 |
2.36 mm (No. 8) | 15 |
1.18 mm (No. 16) | 35 |
600 μm (No. 30) | 55 |
300 μm (No. 50) | 79 |
150 μm (No. 100) | 97 |
   |
  |   | a) 2.68 |
  |   | b) 2.75 |
  |   | c) 2.83 |
  |   | d) 2.93 |

5) | Aggregate meeting the specification limits shown belowwould have a maximum size of 37.5 mm (1.5 inches) and a nominal size of    ?   .     Specification Limits |
Sieve Size | Percent Passing |
37.5 mm (1.5 in.) | 100 |
25.0 mm (1 in.) | 95-100 |
12.5 mm (1/2 in.) | 25 – 60 |
4.75 mm (No. 4) | 0 – 10 |
2.36 mm (No. 8) | 0 – 5 |
|
  |   | a) 37.5 mm (1.5 in.) |
  |   | b) 25.0 mm (1.0 in.) |
  |   | c) 12.5 mm (1/2 in.) |
  |   |d) 4.75 mm (No. 4) |

6) | Usually as the maximum size of well-graded coarse aggregate increases, the amount of paste to produce concrete of a given slump or consistency    ?   . |
  |   | a) stays the same |
  |   | b) decreases |
  |   | c) increases |

7) | Most normal mass aggregates have a bulk specific gravity between 2.4 and 2.9. Bulk specific gravity is the oven-dry massdivided by the mass of a volume of water equal to the    ?    aggregate volume. |
  |   | a) wet |
  |   | b) saturated surface-dry |
  |   | c) air-dry |
  |   | d) oven-dry |

8) | Use the following information to calculate the volume of a batch of concrete. Assuming an air content of 0 percent (0%), the volume of concrete would be    ?   .    Material | Mass, lb | Specific Gravity |Absolute density, lb/ft3 | Absolute Volume, ft3 |
Cement | 470 | 3.15 | 196.6 | 2.39 |
Water | 280 | 1.0 | 62.4 | 4.49 |
SSD Fine Aggregate | 1315 | 2.60 | 162.2 | 8.11 |
SSD Coarse Aggregate | 1838 | 2.63 | 164.1 | 11.20 |
|
  |   | a) 25.55 ft3 |
  |   | b) 26.35 ft3 |
  |   | c) 26.19 ft3 |
  |   | d) 26.80 ft3 |

9) | Mixing water is defined as the sum of the mass of water addedto the batch and the masses of    ?   . |
  |   | a) free or surface water on the fine and coarse aggregate |
  |   | b) absorbed water in the fine and coarse aggregate |
  |   | c) saturated surface-dry water on the fine and coarse aggregate |
  |   | d) absorbed and surface water in the fine and coarse aggregate |

10) | Calculate the water-cementitious materials ratio given thefollowing information.    | Batch mass, lb | Total Moisture,% | Dry Mass, lb | Surface Moisture,% | Mixing Water, lb |
Cement | 450 | 0 | 450 | 0 | — |
Fly Ash | 150 | 0 | 150 | 0 | — |
Sand | 1590 | 5.5 | 1503 | 4.8 | 72 |
Gravel | 1840 | 1.2 | 1818 | 0.5 | 9 |
Water | 242 | — | — | — | 242 |
|
  |   | a) 0.52 |
  |   | b) 0.54 |
  |   | c) 0.56 |
  |   | d) 0.58 |

Examen 2Bulk density of an aggregate is the mass of the aggregate divided by the volume of particles and voids between the particles. Calculate the bulk density to the nearest 1 lb/ft3 of an aggregate given the following information.  Mass of aggregate and container = 83.0 lbMass of empty container = 29.0Volume of container = .495 ft3  |
  |   | a) 119 |
  |   | b) 115 |
  |   | c) 109 |
 ...
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