REINFORCED CEMENT CONCRETE (RCC) BASICS AND TUTORIALS

REINFORCED CEMENT CONCRETE (RCC) BASIC INFORMATION
What Is Reinforced Cement Concrete (RCC)?

Concrete is good in resisting compression but is very weak in resisting tension. Hence reinforcement is provided in the concrete wherever tensile stress is expected. The best reinforcement is steel, since tensile strength of steel is quite high and the bond between steel and concrete is good.

As the elastic modulus of steel is high, for the same extension the force resisted by steel is high compared to concrete. However in tensile zone, hair cracks in concrete are unavoidable. Reinforcements are usually in the form of mild steel or ribbed steel bars of 6 mm to 32 mm diameter.

A cage of reinforcements is prepared as per the design requirements, kept in a form work and then green concrete is poured. After the concrete hardens, the form work is removed.

The composite material of steel and concrete now called R.C.C. acts as a structural member and can resist tensile as well as compressive stresses very well.

Properties of R.C.C./Requirement of Good R.C.C.

1. It should be capable of resisting expected tensile, compressive, bending and shear forces.

2. It should not show excessive deflection and spoil serviceability requirement.

3. There should be proper cover to the reinforcement, so that the corrossion is prevented.

4. The hair cracks developed should be within the permissible limit.

5. It is a good fire resistant material.

6. When it is fresh, it can be moulded to any desired shape and size.

7. Durability is very good.

8. R.C.C. structure can be designed to take any load.

Uses of R.C.C.

It is a widely used building material. Some of its important uses are listed below:

1. R.C.C. is used as a structural element, the common structural elements in a building where

R.C.C. is used are:

(a) Footings (b) Columns

(c) Beams and lintels (d) Chejjas, roofs and slabs.

(e) Stairs.

2. R.C.C. is used for the construction of storage structures like

(a) Water tanks (b) Dams

(c) Bins (d) Silos and bunkers.

3. It is used for the construction of big structures like

(a) Bridges (b) Retaining walls

(c) Docks and harbours (d) Under water structures.

4. It is used for pre-casting

(a) Railway sleepers (b) Electric poles

5. R.C.C. is used for constructing tall structures like

(a) Multistorey buildings (b) Chimneys

(c) Towers.

6. It is used for paving

(a) Roads (b) Airports.

7. R.C.C. is used in building atomic plants to prevent danger of radiation. For this purpose R.C.C. walls built are 1.5 m to 2.0 m thick.

EXCAVATING AND EARTH PLACING MACHINERY BASICS AND TUTORIALS

EXCAVATION AND EARTH MOVING EQUIPMENT AND MACHINES
What Are The Different Excavation and Machine Moving Equipment?


Bulldozers (‘dozers’) are used for cutting and grading work, for pushing scrapers to assist in their loading, stripping borrowpits, and for spreading and compacting fill. The larger sizes are powerful but are costly to run and maintain, so it is not economic for the contractor to keep one on site for the occasional job.

Its principal full-time use is for cutting, or for spreading fill for earthworks in the specified layer thickness and compacting and bonding it to the previously compacted layer. It is the weight and vibration of the dozer that achieves compaction, so that a Caterpillar ‘D8’ 115 h.p. weighing about 15 t, or its equivalent, is the machine required; not a ‘D6’ weighing 7.5 t which is not half as effective in compaction. The dozer cannot shift material very far, it can only spread it locally.

A dozer with gripped tracks can climb a 1 in 2 slope, and may also climb a slope as steep as 1 in 1.5 provided the material of the slope gives adequate grip and is not composed of loose rounded cobbles. On such slopes of 1 in 1.5 or 1 in 2 the dozer must not turn, but must go straight up or down the slope, turning on flatter ground at the top and bottom. It is dangerous to work a dozer (and any kind of tractor) on sidelong ground, particularly if the ground is soft.

Dozers cannot traverse metalled roads because of the damage this would cause, and they should not be permitted on finished formation surfaces. Sometimes a flat tracked dozer (i.e. with no grips to the tracks) can be used on a formation if the ground is suitable.

Motorized scrapers are the principal bulk excavation and earth-placing machines, used extensively on road construction or earth dam construction. Their movement needs to be planned so that they pick up material on a downgrade, their weight assisting in loading; if this cannot be managed or the ground is tough, they may need a dozer acting as a pusher when loading.

This not only avoids the need for a more expensive higher powered scraper, but reduces the wear on its large balloon tyres which are expensive. The motorized scraper gives the lowest cost of excavation per cubic metre of any machine, but it needs a wide area to excavate or fill and only gentle gradients on its haul road. It cannot excavate hard bands or rock, or cut near-vertical sided excavations.

The face shovel, or ‘digger’ can give high outputs in most types of materials, including broken rock. It comes in all sizes from small to ‘giant’; but for typical major excavation jobs (such as quarrying for fill) it would have a relatively large bucket of 2–5m3 capacity. The size adopted depends on what rate of excavation must be achieved, the capacity of dump trucks it feeds to cart away material, and the haul distance to tip or earthworks to be constructed.