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Courses » Hydration, Porosity & Strength of Cementitious Materials
Unit 6 - Week 4 -
Portland Cement Based Paste System (contd.) and heat of hydration
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How to access the portal Assignment 0
Week 1 - General Discussion on Concrete and its Properties
Week 2 - Aggregates, Mix Design of concrete and Chemical Admixtures
Week 3 - Portland Cement Based Paste Systems
Week 4 - Portland Cement Based Paste System (contd.) and heat of hydration
Lecture 16 -18 Part 1 - Portland Cement Based Paste Systems - VI
Lecture 16- 18 Part 2 - Portland Cement Based Paste System - VII
Due on 2019-02-27, 23:59 IST.
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Assignment-4
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Identify the FALSE statement with regard to the Power’s model for hydration of portland cement based paste system (PCBPS)
Cement gels are basically considered as colloids
The model establishes the relationship between volume of gel and strength of PCBPS
The model establishes the relationship between porosity and strength of PCBPSThe model is applicable for all curing conditions No, the answer is incorrect.
Score: 0
Accepted Answers:
The model is applicable for all curing conditions
Identify the FALSE statement with regard to portland cement based paste systems (PCBPSs)
C-S-H gel does not exert crystal pressure during its growth due to limited space within the system
Aft exerts crystal pressure during its growth due to limited space within the system Degree of hydration increases with increase in the time of curing
Degree of hydration of cement system is unaffected by the presence of impurities in C3S and C2S
No, the answer is incorrect.
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Accepted Answers:
Degree of hydration of cement system is unaffected by the presence of impurities in C3S and C2S Identify the TRUE statement with regard to degree of hydration of ordinary portland cement
Degree of cement hydration is independent of w/c ratio
Both degree of cement hydration and porosity increases as the period of curing increases Evaporable water content is a measure of the chemically combined water directly present in hydrated compounds
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Week 5 - Mineral Admixtures
Week 6 - Mineral Admixtures (Contd.)
Week 7 - Paste and Concrete
Week 8 - Concrete
Lecture 19 - Heat of hydration of Portland Cement Lecture 20 - Mass Concrete Quiz : Assignment-4 Assignment-4 Solution Hydration, Porosity &
Strength of Cementitious Materials:
Feedback For Week 4
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The hydration of C3A is rapid without gypsum No, the answer is incorrect.
Score: 0
Accepted Answers:
The hydration of C3A is rapid without gypsum
Identify the TRUE statement with regard to portland cement based paste systems (PCBPSs)
Evaporable water considers only the water present in capillary pores
The amount of water in the pores (both gel and capillary pores) is independent of the w/c ratio
The amount of gel pores at 28 day curing period in PCBPSs having different w/c ratio may be taken to be equal
The minimum w/c ratio for complete hydration of PCBPS with gel pores fully saturated is 0.42 No, the answer is incorrect.
Score: 0
Accepted Answers:
The minimum w/c ratio for complete hydration of PCBPS with gel pores fully saturated is 0.42 Identify the TRUE statement with regard to portland cement based paste systems
(PCBPSs)
For a fully saturated system, the amount of non-evaporable water is higher than evaporable water
For a fully saturated system, the sum of evaporable and non-evaporable water is about 36%
The strength of PCBPSs increases as the gel-to-space ratio in the system increases Compared to
C
3S
, the rate of hydration for bothC
3A
andC
2S
is lowerNo, the answer is incorrect.
Score: 0
Accepted Answers:
The strength of PCBPSs increases as the gel-to-space ratio in the system increases Identify the FALSE statement with regard to portland cement based paste systems (PCBPSs)
Washburn’s equation is used to calculate the porosity of PCBPSs
At early curing periods, the porosity of the system is low since the capillary pores are disconnected
Irrespective of the w/c ratio, the permeability of PCBPS typically in the range of about 10-5 to 10-13 m/s
The size of connected capillary pores in system is measured in terms of effective or critical pore access diameter
No, the answer is incorrect.
Score: 0
Accepted Answers:
At early curing periods, the porosity of the system is low since the capillary pores are disconnected Identify the FALSE statement with regard to heat of hydration of portland cement based
paste systems (PCBPSs)
The total heat evolved at any instant of time within the system is related to the heat of hydration of the individual Bogue’s compounds and their quantities present in cement
For casting concrete in low temperature environments, the heat of hydration values are
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beneficial as its provides information about the activation energy for hydration
The total heat evolution trend helps to understand precisely the chemical reactions occurring during the cement hydration process
Specific heat of concrete is one parameter that determines the dissipation of heat within concrete
No, the answer is incorrect.
Score: 0
Accepted Answers:
The total heat evolution trend helps to understand precisely the chemical reactions occurring during the cement hydration process
Identify the FALSE statement with regard to heat of hydration of portland cement based paste systems
Thermal stresses are generated inside concrete if the rate of dissipation of heat is lower than the rate of evolution of heat
The time taken to reach the maximum temperature in a concrete mixture increases with the increase in the thickness of the member
The rate of heat evolution during hydration of C3A decreases with increase in the amount of the gypsum present in cement
Coefficient of thermal expansion of coarse aggregates is one parameter that determine the heat of hydration in concrete
No, the answer is incorrect.
Score: 0
Accepted Answers:
Coefficient of thermal expansion of coarse aggregates is one parameter that determine the heat of hydration in concrete
Identify the TRUE statement with regard to mass concrete
Cement used should have lower
C
2S
andC
3A
from the standpoint of temperature rise in concreteReducing the cement content by using higher coarse aggregate content helps in reducing the temperature rise
Cement having lower fineness is preferred as it allows the dissipation of heat at a faster rate The heat dissipation is easier in members having larger volume-to-surface area ratio No, the answer is incorrect.
Score: 0
Accepted Answers:
Reducing the cement content by using higher coarse aggregate content helps in reducing the temperature rise
Identify the TRUE statement with regard to Thermal Cracking Index (TCI)
Thermal Cracking Index (TCI) as defined as the ratio of the instantaneous thermal stress to the instantaneous tensile strength of the concrete
Thermal Cracking Index (TCI) is an intrinsic property of a given concrete An equation of the type E=5000√fck can be used in the computation of the TCI
As the TCI increases, the likelihood of occurrence of thermal cracking in the concrete also increases
No, the answer is incorrect.
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Accepted Answers:
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Thermal Cracking Index (TCI) as defined as the ratio of the instantaneous thermal stress to the instantaneous tensile strength of the concrete