RVV f 2w roller. So consistency requirement play a major part in the selection of materials and mix
proportions. From the standpoint of workability, fly ash is commonly included in RcC mixtures.
As compared to conventional concrete typical RcC mixes contain less cement and cementitious
material paste (250–350 kg/m^3 ) and significantly high fly-ash proportion (25-70%) by weight
of cementitious material. The 28 day strength is comparable with OPC and even sometimes
greater.
A problem created by the drier consistency of RcC is the difficult bonding of fresh concrete
to hardened concrete. The use of special high consistency bedding mixtures for starting the
new concrete placement is helpful in reducing the tendency to form cold joints. The creep and
thermal properties of RcC are within the range of those of conventional normal concrete.
Advantages
- Cement consumption is lower because much leaner concrete can be used.
- Form work costs are lower because of the layer placement method.
- Pipe cooling is unnecessary because of the temperature rise.
- Cost of transporting concrete is lower than with the cable crane method because concrete
can be hauled by end dump trucks; it is spread by bulldozers and compacted by vibratory
rollers. - Rates of equipment and labour utilization are high because of the higher speed of concrete
placement. - The construction period can be shortened considerably.
Applications RcC finds its best application in the construction of concrete pavements because
of good aggregate interlocking, rapid construction in short time and fast rate of development
of strength permitting early opening for traffic. It also finds its applications in construction of
dams, heavy duty parting runways, storage areas and yards.
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Ready mixed concrete (RMC) is a concrete, delivered at site or into the purchaser ’s vehicle, in
plastic condition and requires no further treatment before being placed in a position in which
it is to set and harden. It is a high quality concrete of required grade produced under strictly
controlled conditions in a centralised automatic batching plant and supplied to the customer in
a transit mixer truck for its placement at site. The concrete can be mixed either dry at the
batching plant, loaded into agitator truck mixers and water added during transportation; or it
can be mixed wet at the batching plant, discharged into the agitator truck mixers and transported
to site. The first RMC plant was established in the year 1992 in Pune. At present, RMC plants
are located in almost all the cities of India.
Use of RMC to its full advantage requires more careful planning on the site as compared to
the site mixing. Due to better quality control measures adopted, RMC can be considered to be
almost a factory-made product, yet it is not. It is advantageous not only for mass concreting but
also for small quantities of concrete to be placed at intervals. RMC is extremely useful on
congested sites or in road construction where limited space is available for aggregate stock
piling and mixing plant. The major set back to the use of RMC is its cost. Though a little bit
expensive, the increasing emphasis on quality, with skilled labour becoming expensive, and its
inherent advantages out weigh the cost.