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Concrete has been known to mankind from the 19th century. In recent days, the evolution of use of concrete technologies has been vast. But the conventional concrete construction technology holds a significant role in worldwide construction.
The conventional concrete construction technology involves estimation of material, site preparation, building formwork, placing reinforcement, mixing, pouring, finishing and curing of concrete.
1. Estimation of Materials
To make the excellent quality of concrete, the proportion of concrete ingredients should be measured properly and accurately. The accurate measurement of the concrete ingredients can be carried out by the batching process. Estimating materials is the process in which the quantity or proportion of materials like cement, aggregates, water, etc. are measured on the basis of either weight or volume to prepare the concrete mix.
2. Site Preparation
Soil preparation is the most important aspect of pouring concrete. The soil upon which the concrete is poured must be well-drained and compacted. Properly preparing the subsurface helps to limit the potential for cracks in the finished concrete structure.
Excavation is the first step in soil preparation for concrete works. Depending upon the type of structure, excavation is carried out. Additional 2 inches is added in the excavation for gravel if the soil is normally moist or has a high concentration of clay.
Smooth out the ground with the flat side of a rake so that you have a level surface. Fill in any low spots with soil.
Tamp the ground with a hand tamper or mechanical tamper. The tamper packs the soil down upto the desired density. The finished product should barely leave footprints when walking across it.
3. Building Formwork
Formwork in construction is the used to support structures and act as molds to create structures out of concrete which is poured into the molds. Formwork can be made using moulds out of steel, wood, aluminum or prefabricated forms.
The construction of formwork takes time and involves expenditure up to 20 to 25% of the cost of the structure or even more. The operation of removing the formwork is known as stripping. Reusable forms are known as panel forms and non-usable are called stationary forms.
Good Formwork Requirements
- Strong enough to withstand all types of dead and live loads - Rigidly constructed and efficiently propped and braced both horizontally and vertically, so as to retain its shape.
- The joints in the formwork should be tight against leakage of cement grout.
- Construction of formwork should permit removal of various parts in desired sequences without damage to the concrete.
- The material of the formwork should be cheap, easily available and should be suitable for reuse.
- The formwork should be set accurately to the desired line and levels should have plane surface.
4. Placing of Reinforcement
Reinforcement shall be accurately placed and adequately supported before concrete is placed, and shall be secured against displacement. Reinforcement should be placed as shown on the placing drawings which indicates the number of bars, bar lengths, bends, and positions. The cover is also necessary to assure that the steel bonds to the concrete well enough to develop its strength.
5. Mixing of Concrete
Proper mixing of concrete ingredient is very much necessary as it affects the quality of concrete in its fresh state as well as in the hardened state. A concrete is said to be well mixed if it fulfills the following requirements.
- The concrete mix should be uniform in color.
- Concrete should achieve proper consistency for which it is designed.
- The complete blending of all concrete ingredients.
- Cement paste should cover all the surface of the aggregate.
6. Pouring of Concrete
The mixed concrete is transported to the site of concreting within the initial set time. The poring of concrete can be various methods such as pumping and manual transporting. the poured concrete is compacted using a vibrator for ensuring proper compaction. Care must be taken to prevent air pockets and ensure an even surface.
7. Finishing of Concrete
The most basic type of concrete finish is a smooth surface created through the use of screeds and trowels. Immediately after the concrete has been placed in forms, the screed is used to level out the concrete surface. Screeds often consist of long pieces of metal or wood that are pulled and pushed across the concrete surface to remove excess concrete and fill in gaps in the concrete surface.
8. Curing of Concrete
Curing of concrete is the last and one of the most important activities required to be taken in the process of concrete construction. Curing of concrete is the process of keeping the concrete moist to enable it to gain full strength. This last step plays a very significant role in concrete performance and needs full and minute attention.