Ready-mix concrete

Ready-mix concrete is concrete that is manufactured in a batch plant, according to a set engineered mix design. Ready-mix concrete is normally delivered in two ways. Ready-mix concrete is concrete that is manufactured in a batch plant, according to a set engineered mix design. Ready-mix concrete is normally delivered in two ways. First is the barrel truck or in–transit mixers. This type of truck delivers concrete in a plastic state to the site. Second is the volumetric concrete mixer. This delivers the ready mix in a dry state and then mixes the concrete on site. Batch plants combine a precise amount of gravel, sand, water and cement together by weight, 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 used over other materials due to the cost and wide range of uses in building, particularly in large projects like high rise buildings and bridges. It has a long life span when compared to other products of a similar use, like road ways. It has an average life span of 30 years under high traffic areas compared to the 10 to 12 year life of asphalt concrete with the same traffic. Ready-mix concrete, or RMC as it's also known, refers to concrete that is specifically batched or 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. Ready-mixed concrete is used in construction projects where the construction site is not willing, or not able, to mix concrete on site. Using ready-mixed concrete means product is delivered finished, on demand, in the specific quantity required, to the specific mix design required. For a small to medium project, the cost and time of hiring mixing equipment, labour, plus purchase and storage for the ingredients of concrete, added to environmental concerns (cement dust is a particular airborne health hazard and nuisance) may simply be not worth it when compared to the linear cost model of ready-mixed concrete, where the customer pays for what they use, and lets someone else do the work up to that point. For a large project, outsourcing concrete production to ready-mixed concrete suppliers means delegating the quality control and testing, material logistics and supply chain issues, and mix design, to specialists who are already set up for those tasks, trading off against introducing another contracted external supplier who needs to make a profit, and losing the control and immediacy of on-site mixing. Ready-mix concrete is bought and sold by volume – usually expressed in cubic meters (cubic yards in the US). Batching and mixing is done under controlled conditions. In the UK, ready-mixed concrete is specified either informally, by constituent weight or volume (1-2-4 or 1-3-6 being common mixes) or using the formal specification standards of the European standard EN 206+ A1, which is supplemented in the UK by BS 8500. This allows the customer to specify what the concrete has to be able to withstand in terms of ground conditions, exposure, and strength, and allows the concrete manufacturer to design a mix that meets that requirement using the materials locally available to a batching plant. This is verified by laboratory testing, such as performing cube tests to verify compressive strength and supplemented by field testing, such as slump tests done on site to verify plasticity of the mix. The performance of a concrete mix can be altered by use of admixtures. Admixtures can be used to reduce water requirements, entrain air into a mixture, add small fibres of PPP to improve surface durability, or even superplasticise concrete to make it self-levelling, as self-consolidating concrete, but the use of admixtures requires precision in dosing and mix design, which is more difficult without the dosing/measuring equipment and laboratory backing of a batching plant, which means they are not easily used outside of ready-mixed concrete.