1.1 An overview
Concrete is widely used in construction work. In Bangladesh cast at site concrete is generally used in most in construction work. But in the developed countries Ready Mix Concrete (RMC) had been using since long before. Though this technology is new in Bangladesh, its uses are increasingly being practiced in the country. A few companies in Dhaka and Chittagong are manufacturing Ready mix concrete for construction; CONCORD Ready Mix Concrete Plant is one of them and they introduced Ready Mix Concrete first in Bangladesh. As RMC technology is not very old in Bangladesh, from engineering point of view it is thought to be very essential to gather knowledge on the production process and the quality control system of Ready Mix Concrete. A thorough study was made in CONCORD Ready Mix Concrete plant.
1.2 Scope and objectives of the study
The scope and objectives of the study are:
1) To study and know about the manufacturing process of Ready Mix Concrete in CONCORD starting from collection of raw materials, their storage, batching and mixing to transportation to site by transit mixer.
2) To study and know about the quality control process i.e. quality control of raw materials, trial mix and specified concrete strength, use of water and admixture, production process, transportation and placing of concrete at site etc.
READY MIX CONCRETE
When concrete is mixed readily in the plant rather than mixing it on the site and transported readily in the site by transit truck in fresh state, it is called ready mix concrete.
ACI 116R-00 defines the term admixture as “a material other than water, aggregates, hydraulic cement and fiber reinforcement, used as an ingredient of a cementitious mixture to modify its freshly mixed, setting or hardened properties and that is added to the batch before or during its mixing.” Ready-mix concrete is a type of 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. 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 sometimes preferred over on-site concrete mixing because of the precision of the mixture and reduced worksite confusion. However, using a pre-determined concrete mixture reduces flexibility, both in the supply chain and in the actual components of the concrete. Some leading ready-mix concrete suppliers worldwide are the Mexican concrete companies PCM and CEMEX; their main competitor is France-based Lafarge. Ready Mixed 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. In traditional work sites, each of these materials is procured separately and mixed in specified proportions at site to make concrete. Ready Mix Concrete is bought and sold by volume - usually expressed in cubic meters. RMC can be custom-made to suit different applications. Ready Mix Concrete is manufactured under computer-controlled operations and transported and placed at site using sophisticated equipment and methods. RMC assures its customers numerous benefits.
Why Ready-Mix Concrete?
* Appropriate Mix as well as appropriate quantity.
* Time saving for construction.
* Environmental Friendly.
* Zero Wastage.
* Economy for a project where storage space for raw materials is insufficient. * Eliminate labour dependence.
* Work time adjustment. I.e. day night service....