Detailed process for concreting
This construction article briefly analyzes the detailed procedure of Concreting :- Concreting sums up the various methods like BATCHING, MIXING, TRANSPORTATION, PLACING, COMPACTION, FORMWORK, CURING, etc of concrete.
• BATCHING – Batching process involves computation and blending various concrete elements like cement, coarse aggregate, fine aggregate, cement and water, in perfect ratios with adherence to the mixed design. Batching refers to the method of managing the ratios of elements in every batch of concrete for work. There are two types of batching like weight batching and volume batching.
o Weight batching refers to more professional batching method ideal for practice. Batching plants having huge capability are set up for concrete work. Volume batching is recommended by BIS.
• MIXING – Mixing is done by hand or machine. The elements are blended to produce a uniform mixture of concrete. Mixing through machine is performed with drum mixer on the jobsite and there exist various types of mixers. Mixers contain a channel in which all the quantified batch of materials is attached by hand. Then the channel transfers that into a revolving drum on the other side. Then water is also applied to produce wet mix. The RPM of drum is checked by hand on jobsite. After blending properly, the concrete is poured in formwork.
• TRANSPORTATION – It is not always necessary to form concrete on the jobsite due to the scarcity of land, storage, quantity of concrete required, standardization of quality of concrete. Therefore, the concrete should be formed at a place known as RMC plant alias Ready Mix Concrete. A concrete mixing plant functions through a simple program on computer and it is set up at an adjacent locality where customers can smoothly reach out and supply can be completed prior to setting time. In a RMC plant, there are three storage pits for sand(FA), coarse aggregate and cement which are retained at their minimum level. The conveyor belt transmits the material into drum. At the uppermost position of drum there is a storage for water and admixtures. The controls of the method are managed from cabin through a simple program on computer. The batching ratios are programmed and mixer blends the material equally. Then it is poured into the Transit Mixer which is a revolving drum attached on the back of a truck that resists concrete from setting when in transit to the site.
PLACING & COMPACTION:
• This is the most difficult task in entire concreting system for placing concrete into formwork perfectly. If it is done by hand, extreme concrete wastage occurs. Thus for large work, concrete is directly pumped into formwork from transit mixer.
• The primary objective of compaction is to eliminate choked air in concrete to facilitate Honey-combed structure, which is damaging for structure and it should be avoided. There are different types of vibrators for the compaction :-
o Steel rod – Manual way.
o Needle vibrator – For dense reinforcement & mostly used.
o Surface Vibrator – Used for compaction of slab concreting.
o Formwork Vibrator
Ref: abhidnya.wordpress.com and Image Courtesy: en.wikipedia.org
FORMWORK – The formwork is categorized on the basis of wooden and steel material. It is recommended to use steel formwork.
• Wooden formwork
o easily accessible
o inexpensive, recyclable to some extent
o scrap value low
o degenerates because of contacting with water
• Steel Formwork
o Expensive, long-lasting, nonabsorptive
o long lifespan, smooth surface finish, low maintenance
o sizes are limited, extreme loss of heat
CURING – As the concreting is an heat-releasing process, significant portion of heat is produced which is resisted by the curing method, otherwise the heat may cause cracking in the structure. Curing is performed with two ways :-
• Moist curing – The uncovered surface of concrete is retained wet or moist constantly for minimum 7 days. Application of sprinkling water, layer of sacking, etc can be performed. Steam curing is also performed for high strength concrete.
• Membrane Curing – Under this method, a compound is used on the uncovered surface of concrete. This compound will resist vaporization of water from concrete. So the heat can be controlled by preserving the water content.