Ready-mix concrete is concrete that is manufactured in a factory or batching plant, according to a set recipe, and then delivered to a work site by truck mounted in–transit mixers. This results in a precise mixture, allowing specialty concrete mixtures to be developed and implemented on construction sites. The first ready-mix factory was built in the 1930s, but the industry did not begin to expand significantly until the 1960s, and it has continued to grow since then.Ready-mix concrete is often preferred over on-site concrete mixing because of the precision of the mixture and reduced work site confusion.Ready-mix 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. Concrete itself is a mixture of Portland cement, water and aggregates comprising sand and gravel or crushed stone. Ready-mix concrete is bought and sold by volume – usually expressed in cubic meters (cubic yards in the US).Ready-mix concrete is manufactured under controlled operations and transported and placed at site using sophisticated equipment and methods. In 2011, there were 2,223 companies employing 72,924 workers that produced RMC in the United States
Raw material used to produce concrete:
Aggregates
Aggregates, which make up roughly 60% to 75% of ready-mix concrete’s volume, are obtained from quarries and aggregate banks.
Additives
Additives are solid or liquid chemical substances that can be added to ready-mix concrete before or during preparation. Most commonly used additives either improve a hardened concrete’s durability or reduce a concrete’s water content in an effort to shorten setting times.
Water
This is the mix’s vital fluid, which sets of a chemical reaction when it comes into contact with the cement.
Cement
No other material rivals cement’s importance in the mix; it’s the ingredient that gives concrete its resistance. Although types II and IV are also employed, the most widely used cements are gray Portland type I and Pozzolana Portland type C-2.
Concrete mixing
During the mixing phase the different components come together to produce a uniform mass of concrete. Mixing time is registered from the moment material and water are poured into the cement mixer, and it begins rotating.
While transporting concrete to a site, the cement mixer never stops revolving at a speed of two to six rotations per minute.
