20-03-2012, 12:55 PM
READY MIX CONCRETE
READY MIX CONCRETE.ppt (Size: 1.02 MB / Downloads: 835)
INTRODUCTION
Ready mix concrete that is manufactured in a factory or batching plant, according to a set recipe, and then delivered to a worksite, by truck mounted transit mixers . This results in a precise mixture, allowing specialty concrete mixtures to be developed and implemented on construction sites.
It is popularly called as RMC, specially manufactured for delivery to the customers construction site in a freshly mixed and plastic or unhardened state. It is sold by volume expressed in cubic meters.
ADVANTAGES
A centralized concrete batching plant can serve a wide area.
The plants are located in areas zoned for industrial use, and yet the delivery trucks can service residential districts or inner cities.
Better quality concrete is produced.
Elimination of storage space for basic materials at site.
Elimination of hiring of plant and machinery.
Wastage of basic materials is avoided.
Labors associated with production of concrete is eliminated.
Time required is greatly reduced.
Noise and dust pollution at site is reduced.
DISADVANTAGES:-
The materials are batched at a central plant, and the mixing begins at that plant, so the traveling time from the plant to site is critical over longer distances.
Access roads, and site access have to be able to carry the weight of the truck and load concrete is approx 2.5tonne per cuM.
concrete’s limited time span between mixing and going-off means that readymix should be placed within 2hours of batching at the plant
Transit Mixed (or "truck-mixed") Concrete:-
In transit-mixed concrete, also called truck mixed or dry-batched, all of the raw ingredients are charged directly in the truck mixer. Most or all water is usually batched at the plant.
Concrete mixed at the job site:- While traveling to the job site the drum is turned at agitating speed (slow speed). After arriving at the job site, the concrete is completely mixed.
Concrete mixed in the yard:- The drum is turned at high speed or 12-15 rpm for 50 revolutions. This allows a quick check of the batch. The concrete is then agitated slowly while driving to the job site.
Concrete mixed in transit:- The drum is turned at medium speed or about 8 rpm for 70 revolutions while driving to the job site. The drum is then slowed to agitating speed.