Civil Engineering Basics

Civil Engineering: It is the oldest branch of engineering which deals with planning, designing, construction and maintenance of structures.

Branches in civil engineering

1.      Surveying

2.      Structural Engineering

3.      Geotechnical Engineering

4.      Transportation Engineering

5.      Environmental Engineering

6.      Water resource Engineering

   

1. Surveying: It is the technique of determining the position of some point with respect to the reference points directly or indirectly.

Types of surveying:

1      Plane surveying

2.     Geodetic surveying

Plane Surveying: It is that type of surveying in which the mean surface of the earth is considered as a plane and the spheroidal shape is neglected.  All triangles formed by survey lines are considered as plane triangles.  The level line is considered as straight and plumb lines are considered parallel.  In other words, when small areas are to be surveyed, the curvature of the earth’s surface is ignored and such a surveying is called plane surveying.

Geodetic Surveying: It is that type of surveying in which the curved shape of the earth is taken in to account.  The object of geodetic survey is to determine the precise position on the surface of the earth, of a system of widely distant points, which form control stations in which surveys of less precision may be referred.

2. Structural Engineering: It is the branch of civil engineering, which deals with

a)      Planning

b)      Designing

c)      Construction of infrastructure

d)     Analysis of structure for different combination of loads

e)      Analysis of serviceability of the structure

3. Geotechnical Engineering:  It is the branch of civil engineering, which deals with

a)      Property of soil in the site to be constructed.

b)      Bearing capacity of soil from the building.

c)      Selecting type of foundation required for the particular structure.

d)     Study of soil structure interaction.

e)      Study the effect on soil during mining, earthquake, landslides etc…

4. Transportation Engineering: It is the branch of civil engineering, which deals with

a)      Planning, designing and construction of runways, railways and highways.

b)      Study the accident zones for safe and comfort transport system.

c)      Promoting public transport and mass transport system.

d)     Traffic studies in the particular mode and designing to reduce the volume of traffic.

Difference between dry process and wet process of cement production.

Difference between dry process and wet process of cement production.

Dry process	Wet process
Raw materials are mixed in its dry state	Raw materials are mixed in wash mill along with 30-50% of water
Dry mixed raw materials entering to the kiln are called as kiln feed	Wet mixed raw materials entering to the kiln is called as slurry
Size of kiln required in this process is less	Size of kiln required in this process is more
Since the mix is in dry state, therefore achievement of homogeneity of the mix is of lesser degree	Raw materials are mixed in wet state , degree of homogeneity of the mix achieved is high
Fuel consumption for this process is less	Fuel consumption for this process is more
Energy required is less	Energy required is more
Cost of production is less	Cost of production is more
Carbon di oxide emission is comparitively less in this process	Carbon di oxide emission is comparitively more in this process

CEMENT AND ITS MANUFACTURING PROCESS

Cement Introduction: Cement is the world’s second largest consumed product next to water. It is a fine powdery, inorganic, hydrophilic material which forms a paste, sets and hardens due to hydraulic reaction when mixed with water. Cement is the important binding material which adheres to the other materials of construction and there by results in homogeneity of the resultant product.

Currently, India is second largest producer and consumer of cement after China. However, China’s production is nearly nine times higher than India.

Manufacturing process of cement

Manufacturing process of the cement involves the following stages

1     Stage 1:

Collection of raw materials: Raw materials, which are of mineralogical origin or industrial waste products can be used for cement production. Major components used for cement production are of calcareous and argillaceous materials. Calcareous materials are those containing maximum part of calcium based compounds in its composition. Whereas argillaceous materials are those containing fine grained alumina (clay) minerals in its composition. Some of the calcareous and argillaceous based rocks which are commonly used for cement production are listed in table 1 below

Table 1: list of Calcareous and argillaceous materials

Calcareous materials	Argillaceous materials
	Silicon based	Aluminum based	Iron based
Limestone	Sand stone	Fly ash	Blast furnace slag
Marl	Fly ash	Aluminum ore refuse	Iron ore
Calcite	Rick husk Ash		Shale
Aragonite	Slag
Shale
Sea shell

  

Stage 2:

Grinding, Mixing and proportioning of the raw materials: The collected raw materials are crushed into small sizes and then stored in large tanks. Further, the raw materials are mixed and proportioned before feeding it into the rotary kiln. In order to obtain good quality of cement, the raw materials should be mixed and fed proportionately. The quantity of raw materials feeding into the kiln depends on the purity of the material. Generally, if the material is pure to its maximum extent, then lime stone is fed 80% and clay is taken as 20% of the total weight of raw material.

 Stage 3:  

Pre heating of the raw material: After final grinding, the material is ready to face the pre-heating chamber. Pre-heater chamber consists of series of vertical cyclone from where the raw material passes before facing the kiln. Pre-heating chamber utilizes the emitting hot gases from kiln. Pre-heating of the material saves the energy and make plant environmental friendly.

Stage 4:

Burning phase: In this phase the preheated raw materials are burned up to 1500^oC in the huge rotating furnace called as kiln. At this temperature limestone releases huge amount of carbon di oxide, and the process is called decarbonation. Further due to the exposure of high temperature there will be series of chemical reaction between limestone (calcium carbonate) and clay (silicon di oxide) compounds to form primary constituents of cement. When the material reaches lower part of the kiln, it forms clinkers.

Stage 5:

Cooling and final grinding: The clinkers are finally cooled by lowering the temperature by means of forced air. After cooling the clinker, it is then passed to the horizontal rotating drum, filled with steel balls. Here, steel balls tumble and crush the clinker into a very fine powder. During grinding gypsum is also added to the mix in small percentage that controls the setting of cement.

Stage 6:

Packing

Material is directly conveyed to the silos (silos are the large storage tanks of cement) from the grinding mills. Further, it is packed to about 50 kg bags. Only a small percent of cement is packed in the bags only for those customers whom need is very small.