Question

1. Why is water adjustment necessary in carrying out concrete mix proportioning? How to adjust the water content in concrete mix when the aggregate is air-dried?              

2. Which ASTM cement is most appropriate for the following construction applications? What types of mineral and/or chemical admixtures could be used for each application?

Give reasons for your choices.                                                                                

• Construction of a bridge pier in sea.
• Construction of concrete pavement (open traffic on the next day).
• Construction of a transfer plate with a thickness of 2 metres.
• Construction of a bored pile with a depth of 25 metres.
• Construction of an exposed aggregate concrete wall.

Question 2

1. List 7 measures that may be used to prevent the corrosion of reinforced concrete structure and give reasons in details.                                                                                  

2. With the aid of a series of appropriate schematic diagram(s), demonstrate the alkali-aggregate reaction and indicate the control techniques during reaction in details.

                                                                                                                         

Question 3

1. What causes thermal cracking of concrete in early day of concreting? Name 4 methods that can be used to control it and give reasons in details.                                          

2. Use an appropriate diagram, describe the distribution of hydration products in the interfacial transition zone (ITZ). Why is there such a distribution? And name 4 measures to improve the ITZ with reasons in details.                                                           

Answer 1

so in this case "air dried aggregate" extra water should be added to account for the loss as explained.

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