is concrete that is manufactured in a batch plant, according to each specific job requirement, then delivered to the job site “ready to use”
There are two types with the first being the barrel truck or in–transit mixers. This type of truck delivers concrete in a plastic state to the site. The second is the volumetric concrete mixer. This delivers the ready mix in a dry state and then mixes the concrete on site. However, other sources divide the material into three types: Transit Mix, Central Mix or Shrink Mix concrete.
Ready-mix concrete refers to concrete that is specifically manufactured for customers’ construction projects, and supplied to the customer on site as a single product. It is a mixture of Portland or other cements, water and aggregates: sand, gravel, or crushed stone. All aggregates should be of a washed type material with limited amounts of fines or dirt and clay. An admixture is often added to improve workability of the concrete and/or increase setting time of concrete (using retarders) to factor in the time required for the transit mixer to reach the site. The global market size is disputed depending on the source. It was estimated at 650 billion dollars in 2019. However it was estimated at just under 500 billion dollars in 2018.
Materials are combined in a batch plant, and the hydration process begins at the moment water meets the cement, so the travel time from the plant to the site, and the time before the concrete is placed on-site, is critical over longer distances. Some sites are just too distant. The use of admixtures, retarders, and cement-like pulverized fly ash or ground granulated blast-furnace slag (GGBFS) can be used to slow the hydration process, allowing for longer transit and waiting time.
Concrete is formable and pourable, but a steady supply is needed for large forms. If there is a supply interruption, and the concrete cannot be poured all at once, a cold joint may appear in the finished form.
Certification of Ready Mix Concrete (RMC) plants by the National Accreditation Board for Certification Bodies (NABCB) typically involves adherence to […]
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