29 Questions
What is the primary purpose of using supplementary cementitious materials in concrete?
To reduce the carbon footprint of concrete by reducing portland cement consumption
What type of materials react chemically with calcium hydroxide to form calcium silicate hydrates?
Pozzolans
What is the typical size range of fly ash particles?
0.5 to 100 µm
What is the fineness range of fly ash in m²/kg?
250 to 600 m²/kg
What is the byproduct of coal-fired thermal power plants used as a supplementary cementitious material?
Fly ash
What is the chemical reaction between pozzolans and calcium hydroxide that contributes to the strength development in concrete?
Pozzolan + calcium hydroxide → calcium silicate hydrates
What is the primary reason why sand is usually well graded in a concrete mix?
To ensure good workability and packing of materials
What is the primary reason for the higher rate of hydration in cement with higher fineness?
Larger surface area
What is the effect of a larger maximum size of aggregate on the concrete mix?
It reduces the water content required for the concrete
What is the typical specific surface area range of Rapid Hardening Portland Cement (ASTM Type III)?
450 to 600 m 2 /kg
What is the primary purpose of Stage II in the hydration process of concrete?
To allow for proper mixing, transporting, and placement of concrete
What is the primary reason why elongated and flaky aggregates are not desirable in concrete?
They adversely affect the durability and strength of the concrete
What is the primary cause of the initial set of cement paste?
Hydration of C 3 A and C 3 S
What is the main factor that determines the increase in temperature of concrete due to hydration?
All of the mentioned factors
What is the primary difference between coarse aggregate and sand in terms of grading?
Coarse aggregate can be graded or single-sized, while sand is always well-graded
What is the relationship between the carbon content and the elongation of carbon steel?
Increasing carbon content results in decreased elongation
What is the primary purpose of the Vicat needle test (ASTM C191, 2008)?
To determine the consistency and setting time of cement paste
What is the characteristic of round aggregates that makes them beneficial in concrete?
They have a lower water demand
What is the characteristic of the hydration reaction during Stage III?
It is rapid and generates significant heat
What is the purpose of controlling the grading of aggregates in a concrete mix?
To enhance the workability of the concrete mix
What is the primary advantage of using angular aggregates in concrete?
They bond well with the cement paste
What is the primary consequence of high heat of hydration in massive concrete constructions?
Thermal cracking
What happens to the electrical conductivity of the cement paste after the final set?
It decreases significantly
What is the classification of coarse aggregates with a density of 3000-5000 kg/m³?
Heavy weight
What is the characteristic of a cement with normal consistency?
A 10 mm diameter plunger penetrates to 4-6 mm from the bottom of the mold
What is the stage during which the concrete densifies over time?
Stage V
What is the primary reason for the decrease in hydration of cement during Stage IV?
The formation of layers of hydration product covering cement particles
What is the effect of coarse surface texture on the workability of concrete?
It reduces the workability
What is the primary reason why aggregates with a coarse surface texture bond well with the cement paste?
They have a larger surface area
Understand the different stages of concrete development, including the induction period, acceleration period, and more. Learn about the hydration reaction, heat generation, and mechanical strength of concrete.
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