What is Ready-Mixed Concrete – How is it Produced?
Concrete And Its Composition…
The concrete produced by mixing the materials brought together in desired proportions by computer control in a concrete plant or mixer and delivered to the consumer as “fresh concrete” is called “Ready-Mixed Concrete”.
The basic element that distinguishes ready-mixed concrete from concrete prepared at the construction site by hand or by mixing with a concrete mixer is that ready-mixed concrete is produced in modern facilities with computer control. The qualifications that the ready mixed concrete user will look for in ready mixed concrete are included in TS EN 206.
There are two different forms of ready-mixed concrete production depending on whether the water measuring and mixing processes are carried out in the plant or in the transmixer:
1. Dry System
2. Age System
Dry-mixed ready-mixed concrete is ready-mixed concrete, the aggregate and cement of which are measured at the concrete plant and mixed in the plant or in the transmixer, and the water and, if any, chemical additives are measured and mixed at the delivery site. In dry-mixed ready-mixed concrete, special attention should be paid to the amount of water (not more than what is stipulated in the formula) and mixing time (enough time for a homogeneous mixture) given to the mixture at the construction site.
Wet-mixed ready-mixed concrete is ready-mixed concrete with all its components, including water, measured and mixed in the concrete plant.
Ready Mixed Concrete Plant
The facilities where ready-mixed concrete components are stocked, mixed under control, ready-mixed concrete is produced and the transmixers are filled are called “concrete plants”. Concrete batching plants are divided into two as “wet and dry mix” according to their mixing shape, and two as “bunkered” and “star type” according to their storage type.
In the star type plant, there is a star-shaped storage area in front of the plant and the aggregates are transferred to the mixing vessel at the rear by means of a bucket. In the bunker plant, aggregate and sand are stored in the bunkers in front of the plant and transported to the mixing vessel with a belt system.
First, laboratory tests are carried out to examine the quality and compatibility of correctly selected materials (cement, aggregate, water, additives) to be used in the production of ready-mixed concrete. Continuous quality control should be carried out in order to prevent negative changes over time in materials that pass these tests.
The production process of ready mixed concrete starts when the plant operator determines the number of the formula that defines the concrete to be produced and operates the computer system. After the first command, aggregate, cement and water stored in separate compartments are weighed at the same time. Then, the weighed aggregate is transported by belt or bucket and transferred to the mixer boiler. Meanwhile, cement, water and chemical additives, if any, are transferred to the boiler and mixed.
Although the volume of a batch concrete varies from plant to plant, it is generally 1-3 m3. The mixing time in the plant is determined by the standards in proportion to the blend volume. The blend, which has been sufficiently mixed, is poured into the transmixer, and the same process continues until the filling is completed.