(SEM V) THEORY EXAMINATION 2019-20 CONCRETE TECHNOLOGY

CONCRETE TECHNOLOGY (RCE-052)

B.Tech (SEM-V) – AKTU

SECTION A

(Attempt all questions – 2 × 7 = 14 marks)

Q1 (a) Write wet process of cement.

In the wet process of cement manufacturing, raw materials like limestone and clay are mixed with water to form a slurry. This slurry is fed into a rotary kiln, where it is heated to high temperatures. The chemical reactions produce clinker, which is then cooled and ground with gypsum to form cement. The wet process ensures good mixing but consumes more fuel.

Q1 (b) What are supplementary cementitious materials?

Supplementary cementitious materials are materials added to concrete to improve its properties. Common examples include fly ash, silica fume, ground granulated blast furnace slag, and rice husk ash. These materials improve strength, durability, and reduce cement consumption.

Q1 (c) Define creep of concrete.

Creep of concrete is the gradual increase in strain with time when concrete is subjected to a sustained load. It depends on factors such as stress level, age of concrete, humidity, and temperature.

Q1 (d) Write short note on cellular concrete.

Cellular concrete is a lightweight concrete containing air voids created by foaming agents or gas-forming chemicals. It has low density, good thermal insulation, and is commonly used for non-load-bearing walls and insulation purposes.

Q1 (e) What is durability of concrete?

Durability of concrete is its ability to resist weathering action, chemical attack, abrasion, and other environmental effects without deterioration over its service life.

Q1 (f) What are the statical methods of mix design?

Statical methods of mix design use statistical analysis and probability concepts to achieve desired strength and quality. These methods consider variability in materials and provide more reliable mix proportions.

Q1 (g) Define mix concrete.

Mix concrete refers to concrete produced by mixing cement, aggregates, water, and admixtures in specified proportions to achieve required strength and workability.

SECTION B

(Attempt any three – 7 × 3 = 21 marks)

Q2 (a) Write names of important compounds of cement and explain influence of each.

The main compounds of cement are tricalcium silicate, dicalcium silicate, tricalcium aluminate, and tetracalcium aluminoferrite.
Tricalcium silicate provides early strength.
Dicalcium silicate contributes to long-term strength.
Tricalcium aluminate causes quick setting and heat generation.
Tetracalcium aluminoferrite improves resistance to chemical attack and reduces cost.

Q2 (b) Differentiate between controlled concrete and ordinary concrete.

Controlled concrete is produced under strict quality control with precise proportions and testing, while ordinary concrete is mixed with less control. Controlled concrete offers higher strength, durability, and uniformity compared to ordinary concrete.

Q2 (c) Write the factors to be considered for mix design.

Important factors include strength requirement, workability, water-cement ratio, aggregate size and grading, durability requirements, exposure conditions, and quality of materials.