Which grouping of concrete making materials is needed as part of the concrete mi

Question

Which grouping of concrete making materials is needed as part of the concrete mix design to produce ultra-high strength concrete? o a. The use of cement, fly ash, slag and fine sand only, without the inclusion of any fibres D. The use of cement, fly ash and fine sand only, without the inclusion of any fibres OC The use of strong coarse aggregates of 40 mm maximum size o d The use of cement, silica fume and fine sand with the inclusion of a considerable amount of fibres QUESTION6 A bridge operating in a satisfactory condition in a coastal region for a period of 10 years is starting to show signs of extensive cracking. The cracks that have developed on the prestressed bridge girders have been identified to be mostly longitudinal in direction but map (pattern) cracking has also been found at a few locations. The formation of a white coloured deposit has also been observed around most of the cracks. What is the most likely cause of these cracks? oa. Sulphate attack of the concrete DCarbonation-induced corrosion of the steel reinforcement OAlkali-silica reaction of the concrete O d. Chionde-induced corrosion of the steel reinforcement QUESTION 7 A pre-tensioned concrete beam has undergone prestress loss at the time of load transfer to the concrete due to cutting of the tendons at the age of 7 days. Which feature of the prestressed concrete member will most likely contribute to this loss of prestress? O a. The shrinkage component of the concrete D. Slippage at the point of anchorage C The creep component of the concrete O d. The elastic shortening of the concrete

Explanation / Answer

5. d) The use of cement, silica fume and fine sand with inclusion of a considerable amount of fiberes.

         Ultra-High Performance Concrete (UHPC), also known as reactive powder concrete (RPC)

6. c) Alkali-silika reaction of the concrete

7. d) The elastic shortning of the concrete

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