please write the number question Under what conditions may salt solutions damage concrete without involving chemical att

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please write the number question
Under what conditions may salt solutions damage concrete without involving chemical attack on the portland cement paste? Which salt solutions commonly occur in natural environments?
5.7 Briefly explain the causes and control of scaling and D-cracking in concrete. What is the origin of laitance; what is its significance?
5.8 Discuss Powers’ hypothesis of expansion on freezing of a saturated cement paste containing no air. What modifications have been made to this hypothesis? Why is entrainment of air effective in reducing the expansion due to freezing?
5.9 With respect to frost damage, what do you understand by the term critical aggregate size? What factors govern it?
5.10 Discuss the significance of critical degree of saturation from the standpoint of predicting frost resistance of a concrete.
Durability 195
196 Microstructure and Properties of Hardened Concrete
References
5.11 Discuss the factors that influence the compressive strength of concrete exposed to a fire of medium intensity (650°C, short-duration exposure). Compared to the compressive strength, how would the elastic modulus be affected, and why?
5.12 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?
5.13 List some of the common sources of sulfate ions in natural and industrial environments. For a given sulfate concentration, explain which of the following solutions would be the most deleterious and which would be the least deleterious to a permeable concrete containing a high-C3A portland cement: Na2SO4, MgSO4, CaSO4.
5.14 What chemical reactions are generally involved in sulfate attack on concrete? What are the physical manifestations of these reactions?
5.15 Critically review the BRE Digest 250 and the ACI Building Code 318 requirements for control of sulfate attack on concrete.
5.16 What is the alkali-aggregate reaction? List some of the rock types that are vulnerable to attack by alkaline solutions. Discuss the effect of aggregate size on the phenomenon.
5.17 With respect to the corrosion of steel in concrete, explain the significance of the following terms: carbonation of concrete, passivity of steel, Cl−/OH− molar ratio of the contact solution, electrical resistivity of concrete, state of oxidation of iron.
5.18 Briefly describe the measures that should be considered for the control of corrosion of embedded steel in concrete.
5.19 With coastal and offshore concrete structures directly exposed to seawater, why does most of the deterioration occur in the tidal zone? From the surface to the interior of concrete, what is the typical pattern of chemical attack in sea structures?
5.20 A heavily reinforced and massive concrete structure is to be designed for a coastal location in Alaska. As a consultant to the primary contractor, write a report explaining the state-of-the-art on the choice of cement type, aggregate size, admixtures, mix proportions, concrete placement, and concrete curing procedures.