21. Portland pozzolana cement (PPC) is characterized by the addition of:
a) Fly ash
b) Silica fume
c) Slag
d) Gypsum
View Answer
Correct answer: a) Fly ash
Explanation: Portland pozzolana cement (PPC) is a type of cement that contains fly ash as a supplementary cementitious material. Fly ash enhances the workability, durability, and sustainability of the cement.
22. The term “bulk density” in cement refers to its:
a) Weight per unit volume in a loose state
b) Weight per unit volume in a compacted state
c) Compressive strength
d) Setting time
View Answer
Correct answer: a) Weight per unit volume in a loose state
Explanation: Bulk density of cement refers to its weight per unit volume in a loose state, typically expressed in kilograms per cubic meter (kg/m³).
23. The term “specific gravity” in cement refers to the ratio of the density of cement to the density of:
a) Water
b) Air
c) Aggregates
d) Admixtures
View Answer
Correct answer: a) Water
Explanation: Specific gravity is the ratio of the density of a substance to the density of water at a specific temperature. In the case of cement, it represents the relative density compared to water.
24. The term “initial setting time” of cement refers to the time taken for the cement paste to:
a) Become workable
b) Reach maximum compressive strength
c) Harden and gain some rigidity
d) Fully cure and become durable
View Answer
Correct answer: c) Harden and gain some rigidity
Explanation: The initial setting time of cement is the time taken for the cement paste to undergo initial hardening and gain some rigidity, indicating the start of the setting process.
25. The term “final setting time” of cement refers to the time taken for the cement paste to:
a) Become workable
b) Reach maximum compressive strength
c) Harden and become fully rigid
d) Fully cure and become durable
View Answer
Correct answer: c) Harden and become fully rigid
Explanation: The final setting time of cement is the time taken for the cement paste to fully harden and become fully rigid, indicating the completion of the setting process.
26. Rapid hardening cement is produced by:
a) Grinding the clinker to a finer particle size
b) Adding gypsum to the cement during manufacturing
c) Increasing the proportion of tricalcium aluminate in the clinker
d) Decreasing the proportion of dicalcium silicate in the clinker
View Answer
Correct answer: c) Increasing the proportion of tricalcium aluminate in the clinker
Explanation: Rapid hardening cement is produced by increasing the proportion of tricalcium aluminate in the clinker, which accelerates the early strength development of the cement.
27. The term “heat of hydration” in cement refers to the:
a) Heat generated during the manufacturing process
b) Heat generated when cement comes into contact with water
c) Heat loss during curing
d) Heat required for cement to reach its final setting time
View Answer
Correct answer: b) Heat generated when cement comes into contact with water
Explanation: The heat of hydration refers to the heat generated when cement reacts with water during the hydration process. This heat is responsible for the initial setting and hardening of the cement paste.
28. The term “gypsum” is added to cement during manufacturing to:
a) Enhance the workability of the cement
b) Reduce the setting time of the cement
c) Increase the final compressive strength of the cement
d) Improve the durability of the cement paste
View Answer
Correct answer: b) Reduce the setting time of the cement
Explanation: Gypsum is added to cement during manufacturing to control the setting time of the cement. It retards the hydration process, delaying the setting time and allowing for more workability.
29. The term “blended cement” refers to a type of cement that is produced by blending:
a) Different types of cement together
b) Cement with supplementary cementitious materials
c) Cement with aggregates
d) Cement with chemical admixtures
View Answer
Correct answer: b) Cement with supplementary cementitious materials
Explanation: Blended cement is produced by blending cement with supplementary cementitious materials, such as fly ash, silica fume, or slag. This blending enhances specific properties of the cement and improves sustainability.
30. The term “pozzolanic materials” refers to:
a) Aggregates used in concrete production
b) Chemical admixtures used in cement
c) Supplementary cementitious materials that react with lime
d) Lightweight materials used in insulation
View Answer
Correct answer: c) Supplementary cementitious materials that react with lime
Explanation: Pozzolanic materials are supplementary cementitious materials that react with lime in the presence of water to form cementitious compounds. Examples include fly ash, silica fume, and slag.
