A Visual about the visit…. RMC BATCHING PLANT A Visual about the visit….

CONTENTS Process of Manufacture of Concrete Mixing of concrete Transporting of concrete Concrete pump Placing concrete Compaction of concrete Curing of concrete Finishing of concrete Strength of concrete Conclusion

PROCESS OF MANUFACTURE OF CONCRETE Production of quality concrete requires meticulous care exercised at every stage of manufacture of concrete. It is interesting to note that the ingredients of good concrete and bad concrete are same. If meticulous care is taken at every stage, it will result in good concrete.

Various stages of manufacture of concrete are: (a) Batching (b) Mixing (c) Transporting (d) Placing (e) Compacting (f) Curing (g) Finishing

Modern Ready Mixed Concrete (RMC) Batching plant

BATCHING Volume batching Weight batching The measurement of materials for making concrete is known as batching. The types of batching are: Volume batching Weight batching

VOLUME BATCHING Volume batching is not a good method for proportioning the material because of the difficulty it offers to measure granular material in terms of volume. Volume of moist sand in a loose condition weighs much less than the same volume of dry compacted strength. Because of this, for quality concrete materials have to be measured by weight only. However, for unimportant concrete work or any small job, concrete may be batched by volume. .

WEIGH BATCHING Weigh batching is the correct method of measuring the materials. For important concrete works, invariably, weigh batching system should be adopted. Use of weigh system in batching facilitates accuracy, flexibility and simplicity. In modern batching plants the moisture content of the aggregates with the help of sensors and corrective action is taken to deduct that much quantity of water contained in sand from total quantity of water.

MIXING Thorough mixing of the materials is essential for the production of uniform concrete. The mixing should ensure that the mass becomes homogeneous, uniform in colour and consistency. There are two methods adopted for mixing concrete: (1.) Hand mixing (2.) Machine mixing

HAND MIXING Hand mixing is practised for small scale unimportant concrete works. As the mixing is not thorough and efficient, it is desirable to add 10 % more cement to cater for the inferior concrete prepared by this method Hand mixing should be done over impervious concrete or brick floor of sufficiently large size to take one bag of cement. Spread out the measured quantity of coarse aggregate and fine aggregate in alternate layers. Pour the cement on top of it, and mix them dry by shovel, turning the mixture over and over until the uniformity of colour is achieved. This uniform mixture is spread out in thickness of about 20 cm. Water is taken in a water can fitted with a rose-head and sprinkled over the mixture and simultaneously turned over. This operation is continued till such time a good uniform, homogeneous concrete is obtained.

MACHINE MIXING Ready Mixed Concrete, or RMC as it is popularly called, refers to concrete that is specifically manufactured for delivery to the customer's construction site in a freshly mixed and plastic or unhardened state.

TRANSPORTING OF CONCRETE Transporting of concrete is done with the help of: Transit mixers, mortar pans, wheel barrows, crane bucket and ropeways, truck mixer and dumpers, belt conveyers, chute, skip and hoist

TRANSIT MIXER Transit mixer is one of the most popular equipments for transporting concrete over a long distance particularly in RMC plant. There are over 600 transit mixers in operation in India. They are truck mounted having a capacity of 4-7m3. In a transit mixer, mixed concrete is transported to the site by keeping it agitated all along at a speed varying between 2-6 revolutions per minute.

CONCRETE PUMP Concrete pumping is the pouring of concrete from a concrete pumping truck into the form. Once concrete pumping is complete and the forms used during concrete pumping are removed, waterproofing is next. After pumping the concrete allow about 7-days to cure.

Pumping of concrete to upper floors

PLACING OF CONCRETE Construction formwork is the use of support structures to mould and set concrete that has been poured into moulds. The type of formwork that is used in a construction project is determined by many different aspects such as the height of a pillar, which will determine what type of materials will be used to create the specific mould wherein the concrete will be poured. These materials are normally stripped away from the concrete structure once the concrete has set but can also be left to form part of the structure. This type of formwork is known as stay-in-place formwork.

Formwork is kept on the columns for maximum a day while on the beams and slabs for almost 14 days.

COMPACTION OF CONCRETE Compaction begins immediately after placement which is how the concrete attains its level of smoothness, density, surface texture and strength. This stage continues until the density requirements are met. The final stage is curing where moisture is applied, allowing hydration of the concrete, thus causing it to harden and strengthen.

Compaction of concrete using Vibrator

CURING OF CONCRETE With the knowledge that wet cured concrete develops the best performance characteristics, it's believed that wet curing floors have better surface hardness and resistance to abrasion. After finishing steps are complete, workers flood the surface of a slab with water and roll down cover- curing plastic, being careful to eliminate air voids between the cover and the concrete. During the next seven days, covers are removed when needed to add water if surfaces start to dry out.

After curing is completed, the blankets are removed followed immediately by floor maintenance scrubbing and pickup equipment. Floors are then allowed to dry out for a minimum 48-hour period before the application of a penetrating densifier , which is worked into the surface with strip pads.

FINISHING OF CONCRETE Finishing makes concrete attractive and serviceable. The final texture, hardness, and joint pattern on slabs, floors, sidewalks, patios, and driveways depend on the concrete’s end use. Warehouse or industrial floors usually need to be level and smooth, while other interior floors that are covered with carpet do not have to be as exact.

STRENGTH OF CONCRETE Many factors influence the rate at which the strength of concrete increases after mixing. Some of these are discussed below. First, though a couple of definitions will be useful. The process of strength growth is called 'hardening.' This is often confused with 'setting' but setting and hardening are not the same. Setting is the stiffening of the concrete after it has been placed.

WATER-CEMENT RATIO This is defined as the mass of water divided by the mass of cement in a mix. For example, a concrete mix containing 400 kg cement and 240 litres (=240 kg) of water will have a water/cement ratio of 240/400=0.6. Consequently, as the w/c ratio increases, the porosity of the cement paste in the concrete also increases. As the porosity increases, the compressive strength of the concrete will decrease.

GAIN OF STRENGTH WITH AGE It is a well established fact that concrete gets stronger with age. This is particularly true for concrete pipe which is installed in a moist buried environment. Concrete is the only pipe that gets stronger with age. Increasing in strength with age continues as long as any anhydrous cement is still present, provided the concrete remains moist and the concrete temperature remains favourable. When the temperature of the concrete drops below freezing temperature the strength gain virtually stops.

CONCLUSION Today, RMC is playing a very important role in building road and civil structures. They offer unmatched rigidity and long life to the structure. Hence it is getting popular and the use is increasing day by day. There are many advantages of ready mixed concretes some of which are: Less wastage of basic materials Increased concrete quality No labour required Reduced noise and dust pollution No storage space required for basic materials Reduced required time

This is not the end……….