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Discuss the two methods that the cement industry employs to produce cements having different rates of strength development or heat of hydration.
Define the terms initial set and final set. For a normal portland cement draw a typical heat evolution curve for the setting and early hardening period.
Justify this statement by discussing how the phenomena of quick-set, flash set, and false set occur in freshly hydrated portland cements.
Which one of the four major compounds of portland cement contributes most to the strength development during the first few weeks of hydration?
The presence of high free-lime in portland cement can lead to unsoundness. What is meant by the term, unsoundness?
What is the significance of fineness in cement? How is it determined? Can you give some idea of the fineness range in industrial portland cements?
Why is C3S more reactive, and gC2S nonreactive with water at normal temperatures?
In regard to sulfate resistance and rate of strength development, evaluate the properties of the portland cement which has the following chemical analysis.
As a consultant to the primary contractor, write a report explaining the state-of-the-art on the choice of cement type, aggregate size and admixtures.
With coastal and offshore concrete structures directly exposed to seawater, why does most of the deterioration occur in the tidal zone?
explain the significance of the following terms: carbonation of concrete, passivity of steel and Cl- /OH- molar ratio of the contact solution.
What do you know about the origin and characteristics of the following mineral admixtures: pumice, zeolitic tuff, rice husk ash, and silica fume?
When used as an accelerator, what effect would calcium chloride have on the mechanical properties, dimensional stability, and durability of concrete?
What type of admixtures would you recommend for concreting in: (i) hot weather, (ii) cold weather.
Why doesn't calcium sulfate behave like accelerator for portland cement as calcium chloride? Why isn't sodium chloride as effective as calcium chloride?
In their composition and mechanism of action, how do the super plasticizers differ from the normal water-reducing admixtures?
Some manufacturers claim that application of water-reducing admixtures can lower. Explain why all three benefits may not be available at the same time.
After reviewing the ASTM C 618 and C 989 Standard Specifications and other published literature, write a critical note comparing the two standards.
Why are plasticizing admixtures called water reducing? What is distinction between normal and high-range water-reducing admixtures according to ASTM Standard?
Explain the terms sphericity, flat particles, and angular particles. Explain how the surface texture of fine aggregate may influence the properties of concrete.
What considerations control the choice of the maximum aggregate size of aggregate in a concrete? Discuss the reason why grading limits are specified.
If the dry-rodded unit weight of an aggregate is 105 lb/ft3 (1680 kg/m3 ) and its specific gravity is 2.65, determine the void content.
List any three characteristics of concrete aggregate and discuss their influence on both the properties of fresh concrete and hardened concrete.
How are aggregates made from expandable clays, fly ash, and blast-furnace slag? What are some of the interesting characteristics of the products?
In a brief note to your superiors, discuss the equipment needed, deleterious constituents to be avoided, and the cost economy of using the crushed concrete.