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The proportions by mass for a concrete mixture are given as follows. If the unit weight is 2400 kg/m3, compute the cement content.
Determine the SSD mix proportions of concrete required for an outdoor pavement subject to frequent freeze-thaw cycles.
What is the principle behind consolidation of concrete mixtures? Describe the sequence of actions that take place in a fresh concrete mixture.
How would you define workability? Is workability a fundamental property of fresh concrete? If not, why?
Suggest at least two methods to reduce bleeding of a concrete mixture. Give significance and the factors affecting them: slump loss, segregation, and bleeding.
If this rate is too high from the standpoint of risk of plastic-shrinkage cracking, what precautionary measures would you take?
Define the initial and the final setting times as measured by the penetration resistance method (ASTM C-403).
What is the most efficient way of reducing the temperature of a fresh concrete mixture? Explain why.
What is the alkali-aggregate reaction? List some of the rock types that are vulnerable to attack by alkaline solutions.
What chemical reactions are generally involved in sulfate attack on concrete? What are the physical manifestations of these reactions?
List some of the common sources of sulfate ions in natural and industrial environments.
What is the effect of pure water on hydrated portland cement paste? With respect to carbonic acid attack on concrete, what is the significance of balancing CO2?
Discuss the significance of critical degree of saturation from the standpoint of predicting frost resistance of a concrete.
What modifications have been made to this hypothesis? Why is entrainment of air effective in reducing the expansion due to freezing?
Briefly explain the causes and control of scaling and D-cracking in concrete. What is the origin of laitance; what is its significance?
How does aggregate size influence the coefficient of permeability of concrete? What is the difference between erosion and abrasion?
What do you understand by the term durability? How much importance should be given to durability in the design and construction of concrete structures?
What is the usefulness of the extensibility concept? Why would high-strength concrete be more prone to cracking than low-strength concrete?
What is the significance of the term theoretical thickness? Which other factors determine the risk of cracking in a concrete element?
What are the typical ranges of drying shrinkage strain and creep strain in concrete; what is their significance?
What is the significance of adiabatic temperature in concrete? Can we control the coefficient of thermal expansion of concrete? If so, how?
How does the moisture state of a concrete test specimen affect the elastic modulus and strength values?
What is the distinction between the terms rocks and minerals? Basalts, which are generally fine-grained or glassy, are not alkali-reactive.
Discuss the physical-chemical factors involved in explaining the development of strength in products containing the following cementitious materials.
What is the distinction between shrinkage-compensating and self-stressing cements? What are Types K, M, S, and O expansive cements?