Various stages involved in concrete manufacturing
Batching of concrete
Mixing of concrete
Transporting of concrete
Placing of concrete
Compacting of concrete
Curing of concrete
Finishing of concrete
BATCHING
Batching is the process of measuring concrete mix ingredients by either mass or volume and introducing them into the mixer . To produce concrete of uniform quality, the ingredients must be measured accurately for each batch.
This method is generally adopted for small jobs .
Gauge boxes are used for measuring the fine and coarse aggregate.
The volume of gauge box is equal to the volume of one bag of cement.
Gauge box are also called as FARMAS, They can be made of timbers or steel.
They are made generally deep and narrow Bottomless gauge boxes are generally avoided.
While filling the gauge boxes the material should be filled loosely,no compaction is allowed.
Weigh Batching
Batching by weight is more preferable to volume batching ,as it is more accurate and leads to more uniform proportioning.
It does not have uncertainties associated with bulking.
It‘s equipment falls into 3 general categories :
Manual,
Semi automatic,
Fully automatic.
In case of manual batching all weighing and batching of concrete are done manually. It is used for small jobs.
Semi automatic In case of semi automatic batching the aggregate bin gates are opened by manually operated switches . And gates are closed automatically when the material has been delivered. This system also contains interlock which prevents charging and discharging. 3)Fully automatic In case of automatic batching the material are electrically activates by a single switch and complete auto-graphic record are made of the weight of each material. The batching plant comprises 2,3,4 or 6 compartment bins of several capacities. Over the conveyor belt the weigh batchers discharging are provided below the bins
Mixing
The mixing should be ensure that the mass becomes Homogeneous , uniform in color and consistency .
Methods of Mixing :
Hand Mixing
Mixing ingredients of concrete by hands using ordinary tools like, hand shovels etc. This type of mixing is done for Less output of concrete.
Stationary Mixers
Concrete is sometime mixed at job-site in a stationary mixer having a size of 9 cubic meter .
These mixers may be of :
Tilting type ,
Non-Tilting type ,
Tilting type mixer
It consist a conical drum which rotates on an inclinable axis.
It has only one opening.
The drum charged directly and discharged by tilting and reversing the drum.
Non tilting type mixer
The mixing drum is cylindrical in shape and revolves two – horizontal axis.
It has opening on both sides.
The ingredients are charged in from one opening.
For discharging concrete chute is introducing to other opening by operating a lever.
Ready Mixed Concrete
Ready mixed concrete is proportioned and mixed off at the project site and is delivered to the construction area in a freshly mixed and unhardened state. It can be manufactured by any of the following methods:
Central-mixed concrete
Truck-mixed concrete
Central Mixed Concrete
Central-mixed concrete mixed completely in a stationary mixer delivered in Agitator Trucks or A non-agitating truck
Agitator Trucks
A vehicle carrying a drum or agitator body, in which freshly mixed concrete can be conveyed from the point of mixing to that of placing, the drum being rotated continuously to agitate the contents.
Advantages: Operate usually from central mixing plants
Watch for: Timing of deliveries should suit job organization. Concrete crew and equipment must be ready onsite to handle concrete.
Used for: Transporting concrete for all uses. Haul distances must allow discharge of concrete within 1½ hours.
Non Agitator Trucks
Used for: Transport concrete on short hauls(small distance) over smooth roadways.
Advantages: Cost of non-agitating equipment is lower than that of truck agitators or mixers.
Watch for: Slump should be limited. Possibility of segregation. Height upon discharge is needed
Truck-mixed concrete
Used for: Intermittent (periodic) production of concrete at job-site, or small quantities.
Advantages: Combined materials transporter and batching and mixing system. One-man operation.
Transporting
Mortar Pan : Concrete is carried in small Quantities
Wheelbarrows and Buggies : Short flat hauls on all types of onsite concrete construction
Belt Conveyors : Conveying concrete horizontally or higher/lower level.
Cranes and Buckets : Used for Work above ground level , Buckets use with Cranes, cable-ways, and helicopters.
Pumps : Conveying concrete from central discharge point to formwork.
Transit Mixer : used for transporting the concrete over long distance particularly in RMC plant .
Compaction of concrete
Compaction of concrete is process adopted for expelling the entrapped air from the concrete
In the process of mixing , transporting and placing of concrete air is likely to get entrapped in the concrete .
It has been found from the experimental studies that 1% air in the concrete approximately reduces the strength by 6%.
If we don‘t expel this air, it will result into honeycombing and reduced strength
Batching of concrete
Mixing of concrete
Transporting of concrete
Placing of concrete
Compacting of concrete
Curing of concrete
Finishing of concrete
BATCHING
Batching is the process of measuring concrete mix ingredients by either mass or volume and introducing them into the mixer . To produce concrete of uniform quality, the ingredients must be measured accurately for each batch.
- Volume batching
- Weight batching
This method is generally adopted for small jobs .
Gauge boxes are used for measuring the fine and coarse aggregate.
The volume of gauge box is equal to the volume of one bag of cement.
Gauge box are also called as FARMAS, They can be made of timbers or steel.
They are made generally deep and narrow Bottomless gauge boxes are generally avoided.
While filling the gauge boxes the material should be filled loosely,no compaction is allowed.
Weigh Batching
Batching by weight is more preferable to volume batching ,as it is more accurate and leads to more uniform proportioning.
It does not have uncertainties associated with bulking.
It‘s equipment falls into 3 general categories :
Manual,
Semi automatic,
Fully automatic.
In case of manual batching all weighing and batching of concrete are done manually. It is used for small jobs.
Semi automatic In case of semi automatic batching the aggregate bin gates are opened by manually operated switches . And gates are closed automatically when the material has been delivered. This system also contains interlock which prevents charging and discharging. 3)Fully automatic In case of automatic batching the material are electrically activates by a single switch and complete auto-graphic record are made of the weight of each material. The batching plant comprises 2,3,4 or 6 compartment bins of several capacities. Over the conveyor belt the weigh batchers discharging are provided below the bins
Mixing
The mixing should be ensure that the mass becomes Homogeneous , uniform in color and consistency .
Methods of Mixing :
- Hands(using hand shovels)
- Stationary Mixers
- Ready mix concrete
Hand Mixing
Mixing ingredients of concrete by hands using ordinary tools like, hand shovels etc. This type of mixing is done for Less output of concrete.
Stationary Mixers
Concrete is sometime mixed at job-site in a stationary mixer having a size of 9 cubic meter .
These mixers may be of :
Tilting type ,
Non-Tilting type ,
Tilting type mixer
It consist a conical drum which rotates on an inclinable axis.
It has only one opening.
The drum charged directly and discharged by tilting and reversing the drum.
Non tilting type mixer
The mixing drum is cylindrical in shape and revolves two – horizontal axis.
It has opening on both sides.
The ingredients are charged in from one opening.
For discharging concrete chute is introducing to other opening by operating a lever.
Ready Mixed Concrete
Ready mixed concrete is proportioned and mixed off at the project site and is delivered to the construction area in a freshly mixed and unhardened state. It can be manufactured by any of the following methods:
Central-mixed concrete
Truck-mixed concrete
Central Mixed Concrete
Central-mixed concrete mixed completely in a stationary mixer delivered in Agitator Trucks or A non-agitating truck
Agitator Trucks
A vehicle carrying a drum or agitator body, in which freshly mixed concrete can be conveyed from the point of mixing to that of placing, the drum being rotated continuously to agitate the contents.
Advantages: Operate usually from central mixing plants
Watch for: Timing of deliveries should suit job organization. Concrete crew and equipment must be ready onsite to handle concrete.
Used for: Transporting concrete for all uses. Haul distances must allow discharge of concrete within 1½ hours.
Non Agitator Trucks
Used for: Transport concrete on short hauls(small distance) over smooth roadways.
Advantages: Cost of non-agitating equipment is lower than that of truck agitators or mixers.
Watch for: Slump should be limited. Possibility of segregation. Height upon discharge is needed
Truck-mixed concrete
Used for: Intermittent (periodic) production of concrete at job-site, or small quantities.
Advantages: Combined materials transporter and batching and mixing system. One-man operation.
Transporting
Mortar Pan : Concrete is carried in small Quantities
Wheelbarrows and Buggies : Short flat hauls on all types of onsite concrete construction
Belt Conveyors : Conveying concrete horizontally or higher/lower level.
Cranes and Buckets : Used for Work above ground level , Buckets use with Cranes, cable-ways, and helicopters.
Pumps : Conveying concrete from central discharge point to formwork.
Transit Mixer : used for transporting the concrete over long distance particularly in RMC plant .
Compaction of concrete
Compaction of concrete is process adopted for expelling the entrapped air from the concrete
In the process of mixing , transporting and placing of concrete air is likely to get entrapped in the concrete .
It has been found from the experimental studies that 1% air in the concrete approximately reduces the strength by 6%.
If we don‘t expel this air, it will result into honeycombing and reduced strength
