Types of Concrete Block.

Types of Concrete Block:

Hollow Block

Solid Block

Hourdi Block

Thermal Block

Cement Manufacturing Process.

Manufacturing Process

What is cement?
Cement is a fine powder which sets after a few hours when mixed with water, and then hardens in a few days into a solid, strong material. Cement is mainly used to bind fine sand and coarse aggregates together in concrete.  Cement is a hydraulic binder, i.e. it hardens when water is added.
There are 27 types of common cement which can be grouped into 5 general categories and 3 strength classes: ordinary, high and very high.  In addition, some special cements exist like sulphate resisting cement, low heat cement and calcium aluminate cement.

The quarry is the starting point
Cement plants are usually located closely either to hot spots in the market or to areas with sufficient quantities of raw materials. The aim is to keep transportation costs low. Basic constituents for cement (limestone and clay) are taken from quarries in these areas.

A two-step process
Basically, cement is produced in two steps: first, clinker is produced from raw materials. In the second step cement is produced from cement clinker. The first step can be a dry, wet, semi-dry or semi-wet process according to the state of the raw material.

Making clinker
The raw materials are delivered in bulk, crushed and homogenised into a mixture which is fed into a rotary kiln. This is an enormous rotating pipe of 60 to 90 m long and up to 6 m in diameter. This huge kiln is heated by a 2000°C flame inside of it. The kiln is slightly inclined to allow for the materials to slowly reach the other end, where it is quickly cooled to 100-200°C. 
Four basic oxides in the correct proportions make cement clinker: calcium oxide (65%), silicon oxide (20%), alumina oxide (10%) and iron oxide (5%). These elements mixed homogeneously (called “raw meal” or slurry) will combine when heated by the flame at a temperature of approximately 1450°C. New compounds are formed: silicates, aluminates and ferrites of calcium. Hydraulic hardening of cement is due to the hydration of these compounds. 
The final product of this phase is called “clinker”. These solid grains are then stored in huge silos. End of phase one.

From clinker to cement
The second phase is handled in a cement grinding mill, which may be located in a different place to the clinker plant. Gypsum (calcium sulphates) and possibly additional cementitious (such as blastfurnace slag, coal fly ash, natural pozzolanas, etc.) or inert materials (limestone) are added to the clinker. All constituents are ground leading to a fine and homogenous powder. End of phase two. The cement is then stored in silos before being dispatched either in bulk or bagged.

Manufacturing Process of Steel.

Manufacturing Process of Iron(Fe) and Steel.Manufacturing Flow Chart of Steel Pipes-Bend Rolling Process.

How To Identify a Good Brick.

5 Characteristics of Good Bricks – How To Identify a Good Brick:

1.Bricks should be of same color, size and shape.

Brick(190*90*90)

2.Collision of 2 good bricks will produce a metal sound.

3.A good brick won’t break if it is given to fall from approximate 1 meter height.

4.The upper surface of the brick should be plane and without any crack.

5.Bricks should be soaked into water for atleast 12 hours.

7 Test to Justify Brick Quality

To know the quality of bricks following 7 tests can be performed. In these tests some are performed in laboratory and the rest are on field.

1. Compressive strength test
2. Water Absorption test
3. Efflorescense test
4. Hardness test
5. Size, Shape and Color  test
6. Soundness test
7. Structure test

Compressive strength test: This test is done to know the compressive strength of brick. It is also called crushing strength of brick. Generally 5 specimens of bricks are taken to laboratory for testing and tested one by one. In this test a brick specimen is put on crushing machine and applied pressure till it breaks. The ultimate pressure at which brick is crushed is taken into account. All five brick specimens are tested one by one and average result is taken as brick's compressive/crushing strength.

Water Absorption test: In this test bricks are weighed in dry condition and let them immersed in fresh water for 24 hours. After 24 hours of immersion those are taken out from water and wipe out with cloth. Then brick is weighed in wet condition. The difference between weights is the water absorbed by brick. The percentage of water absorption is then calculated.

The less water absorbed by brick the greater its quality. Good quality brick doesn't absorb more than 20% water of its own weight.

Efflorescense test: The presence of alkalies in bricks is harmful and they form a gray or white layer on brick surface by absorbing moisture. To find out the presence of alkalis in bricks this test is performed. In this test a brick is immersed in fresh water for 24 hours and then it's taken out from water and allowed to dry in shade.

If the whitish layer is not visible on surface it proofs that absence of alkalis in brick. If the whitish layer visible about 10% of brick surface then the presence of alkalis is in acceptable range. If that is about 50% of surface then it is moderate. If the alkalis's presence is over 50% then the brick is severely affected by alkalies

Hardness test: In this test a scratch is made on brick surface with a hard thing. If that doesn't left any impression on brick then that is good quality brick.

Size, shape and color test: In this test randomly collected 20 bricks are staked along lengthwise, widthwise and heightwise and then those are measured to know the variation of sizes as per standard. Bricks are closely viewed to check if its edges are sharp and straight and uniform in shape. A good quality brick should have bright and uniform color throughout.

Soundness test: In this test two bricks are held by both hands and struck with one another. If the bricks give clear metallic ringing sound and don't break then those are good quality bricks.

Structure test: In this test a brick is broken or a broken brick is collected and closely observed. If there are any flows, cracks or holes present on that broken face then that isn't good quality brick.