In this article we will discuss the process of Concreting in details..
Concreting is the process of BATCHING, MIXING, TRANSPORTATION, PLACING, COMPACTION, FORMWORK, CURING, etc of concrete.
- BATCHING – Batching process of measuring and combining ingredients of concrete like cement, coarse aggregate, fine aggregate, cement and water, in proper proportion governed by mixed design.Batching is the process of controlling the proportion of ingredients in each batch of concrete for work. It involves two types of batching weight batching and volume batching.
- Weight batching is more professional batching process preferred in practice. Large capacity batching plants are installed for concrete work. According to BIS, volume batching is preferred.
- MIXING – Mixing can be manual or machine. The ingredients are stirred to make a homogeneous mixture of concrete. Machine mixing is done by drum mixer on site and there are many types of mixers. Mixers have a chute in which all the measured batch of materials is added manually. Then the chute transfers that into a rotating drum on the other side. Then water in also added to form wet mix. The RPM of drum can be monitored manually on site. After proper mixing the concrete is poured in formwork.
- TRANSPORTATION – Not always concrete can be prepared on site. Sometimes for the shortage of land, storage, quantity of concrete required, uniformity of quality of concrete. We have to prepare concrete at a place called as RMC plant, which stands for Ready Mix Concrete. A concrete mixing plant operated by a simple program on computer is installed at a nearby locality which will be easy for customers to reach out and supply can be done before setting time. The figure shows details of a RMC plant, in which there are three storage pits for sand(FA), coarse aggregate and cement which are maintained at their minimum level. The conveyor belt transports the material into drum. At the top of drum there is a storage for water and admixtures. The controls of the process are governed from cabin with a simple program on computer. The batching proportions are programmed and mixer mixes the material homogeneously. then it is poured into the Transit Mixer which is a rotating drum mounted on the back of a truck which prevents concrete from setting while on the route to the site.
- PLACING & COMPACTION –
- The hardest thing in whole concreting is placing concrete into formwok properly. When done manually, concrete wastage is maximum thus for bigger work concrete is pumped into formwork directly from transit mixer.
- The main purpose of Compaction is to remove entrapped air in concrete so that Honey-combed structure, which is harmful for structure can be avoided. And for the compaction we have variety of vibrators like
- Steel rod – Manual way.
- Needle vibrator – For dense reinforcement & mostly used.
- Surface Vibrator – Used for compaction of slab concreting.
- Formwork Vibrato
- FORMWORK – The formwork is classified based on material wooden and steel. Wooden was widely used in old days but nowadays steel has covered all the cons in wooden formwork so steel formwork is used.
- Wooden formwork
- easily available
- cheap, reusable at some extent
- scrap value low
- decays due to contact with water
- Steel Formwork
- Costly, durable, non absorbant
- long life, smooth surface finish, low maintenance
- sizes are restricted, excessive loss of heat
- Wooden formwork
- CURING – The concreting is an exothermic process. A lot heat is thrown out which is countered by the process of curing, otherwise the heat will form cracks in the structure. Curing can be done by two ways-
- Moist curing – The exposed surface of concrete is kept wet or moist continuously for at least 7 days. Use of sprinkling water, layer of sacking, etc can be done. Steam curing also can be done for high strength concrete. Railway sleepers are steam cured.
- Membrane Curing – In this process a compound is applied on the surface of exposed surface of concrete. This compound will prevent evaporation of water from concrete. Thus maintaining the water content and heat can be dealt.
This was all about CONCRETING, if you want to know more stay tuned…
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