Machinery

Following are the machines used on the construction site

Batching Plant

-An in-site plant for large scale production of design-mixed concrete. A thorough study of working of batching plant under the guidance of Mr. M. Sahoo was conducted.

The studied plant constituted of Schwing Stetter MIR-360 Mobile Mixing Plant, which is as the name suggests a movable plant fully installed pre-assembled compact units. It has a Twin Shaft Mixer and boasts an output of 60m3/h, making it comparable to a medium sized stationary batching plant.

Each batch has a volume of 1m3. The different divisions of batching plant can be numbered as

1. Cement Storage, transportation and supply.2. Water Supply system3. Aggregate Supply4. Admixture Supply5. Twin Shaft Mixer6. Transportation of prepared cement via transit mixer7. Quality Control Measures and Control Room Operations

Cement Storage, Transportation and Supply

Notable points in this regard are as follows:-The Cement Store-house studied has a capacity of 35,000 bags, with each bag of 50kg capacity.

-Bags are arranged with 12 bags per stack, this is done in-order to comply with safety standards and to avoid cement hardness

-Stacks are placed at a distance of 1ft. from wall so as to avoid effect of moisture and seepage. Such problems can lead to unwanted setting up of cement.

-Masks are made compulsory inside the storage area to avoid respiratory diseases common among cement works.

-Cement gets supplied to the mixing division through a hopper (with max. capacity of 410 kg) which is thereby connected to a 10hp supply motor.

Water Supply System

-Water supply is mainly through two valves and is controlled by one of the sensors.

-A hopper with max. capacity of 230ltr. collects water for each batch.

-The water gets supplied through a 20hp motor.Aggregate Supply

-The aggregates used are 10mm, 20mm and sand as fine aggregates. Observed plant had two stacks of 20mm aggregates and one each of 10mm and sand. Each of these being properly sieved

-A mechanically operated skip is used to bring the aggregates overhead where its tilted into the mixer. Gear mechanism on a 20mm wire pulley system is effectively used to control the speed.

Admixture Supply

-Cico Plast PPR, retarding pumping admixtures and concrete plasticizers was primarily used as admixture.

-The admixture is supplied through a 10ltr capacity cylinder and is discharged via discharge pumps that are automatically rinsed.

Twin Shaft Mixer

-This consists of 8 arms oriented with proper vertical spacing.

-The movement of arms is controlled through two compressors and this has a max. capacity of 1m3. A thoroughly mixed concrete has an average density of 2300-2400kg/m3.

-This mixer has an output of 60 batches per hour and can be manually operated through the soft skill of an operator and a labor.

Chipping- In the occurrence of elongated use, aggregates get coagulated on the arms and need to be removed regularly through a chisel. This process is hence called chipping.

-Dust removal and control mechanism was also observed through a suction duct which re-introduces it into the system.

-A sensor controlled door at the bottom of this mixer enables the exit of finally mixed concrete into the transit mixer truck with a tolerance of 2-3 kg per batch.

The plant generally works to give an output of 3-4 such trucks on a general working day.

Quality Control Measures and Control Room Operations

There exists scope of error due to moisture present hence moisture correction factors are applied properly.

Basically there exists two ways to control such plants

a. Automaticb. Manual

Automatic operations are carried out via company made software whereas manual skills are induced via sematic panel provided in the control room.

In the occurrence of a blockage- as was observed on site- an error message pops out on the panel screen.

To ensure the quality of concrete obtained slump test was conducted followed by checking up of compressive strength of concrete blocks. Various design mixes obtained out of companies namely, Ultratech, Ambuja and Prism were used. The mixes were prepared and verified by NIT Raipur CED.

Transit Mixer

The freshly prepared concrete is carried away in transit mixer trucks. Each truck has a max. capacity of 7 batches but for safety reasons an optimum of 6 batches is filled in one mixer truck.

Once filled mixed concrete should be used within half an hour, but practicality considered on-site, results in a delay of one hour.

Concrete Boom Truck

Concrete Boom truck is used to pump to higher level. The prepared concrete is brought to the boom truck by transit mixer. The arms of pump is remotely controlled by its operator.

Backhoe LoaderBackhoe loader is used for the excavation and filling purposes mainly.

Tower CraneTwo tower cranes were used on the construction site in order to carry materials to the higher ground. Safety norms were strictly followed.

Skid SteerThese were used to carry fewer materials at a short distance and at a quick pace.