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Concrete tochnology

Problems

$7\mathrm{.}1$ Compare internal and external vibration of concrete.

$7\mathrm{.}2$ What are the particular requirements for pumpability of a concrete mix?

$7\mathrm{.}3$ How is the mixing efficiency of a mixer assessed?

$7\mathrm{.}4$ What is the influence of mixing time on the strength of concrete?

$7\mathrm{.}5$ Comment on the relation between the maximum aggregate size and the pipe diameter.

$7\mathrm{.}6$ What are the particular problems in pumping lightweight aggregate concrete?

$7\mathrm{.}7$ What are the particular problems in pumping air$-$entrained concrete?

$7\mathrm{.}8$ Explain the differences between a tilting drum mixer, a non$-$tilting drum mixer, a pan$-$type mixer and a dual drum mixer.

$7\mathrm{.}9$ What is a good sequence of feeding the mixer?

$7\mathrm{.}10$ What are the special requirements for mix proportions of concrete which is to be pumped?

$7\mathrm{.}11$ What are the workability requirements for concrete to be pumped?

$7\mathrm{.}12$ What causes blowholes in concrete?

$7\mathrm{.}13$ What are the effects of re$-$tempering on the properties of resulting concrete?

$7\mathrm{.}14$ What is: $($i$)$ buttering, $($ii$)$ head pack?

$7\mathrm{.}15$ What is a colloidal mixer?

$7\mathrm{.}16$ How is the performance of a mixer assessed?

$7\mathrm{.}17$ How does pumping affect the workability of the mix?

$7\mathrm{.}18$ What are the two main categories of ready$-$mixed concrete?

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MIXING, HANDLING, PLACING, AND COMPACTING CONCRETE

$7\mathrm{.}19$ What are the advantages of using ready$-$mixed concrete?

$7\mathrm{.}20$ What are the disadvantages of using ready$-$mixed concrete?

$7\mathrm{.}21$ What is meant by segregation of aggregate in a stockpile?

$7\mathrm{.}22$ What is the difference between agitating and mixing?

$7\mathrm{.}23$ Why are pipes for pumping concrete not made of aluminium?

$7\mathrm{.}24$ By what method would you place concrete under water?

$7\mathrm{.}25$ Describe dry$-$process shotcreting.

$7\mathrm{.}26$ Describe wet$-$process shotcreting.

$7\mathrm{.}27$ What should you do with rebound material?

$7\mathrm{.}28$ What are the advantages of placing concrete by pumping?

$7\mathrm{.}29$ What is shrink$-$mixed concrete?

$7\mathrm{.}30$ What is the main requirement of good handling of concrete?

$7\mathrm{.}31$ What are the advantages and disadvantages of revibration of concrete?

$7\mathrm{.}32$ State alternative terms for preplaced aggregate concrete and give some typical uses of this concrete.