Concrete is one of the main civil engineering materials at the present times. According to a certain proportion, cementing material, aggregates, skeletal materials and water are mixed into configuration. By mixing and vibration, the concrete is molded and then conserved in certain conditions. The concrete features with abundant of raw materials, low price, and simple production process. For the dosage are more and more, the concrete also features with high compression strength, well durability, wide strength grade, etc. These features make the range of application of the concrete quite wide. The concrete is not only used in all kinds of civil engineering, but also shipbuilding industry, machinery industry, marine development, geothermal projects.
In the preparation of concrete, according to the requirements of the engineering, such as workability, strength and durability, the raw materials should be chosen reasonably and the proportion should be confirmed to achieve the economical and applicable purpose.
According to the different requirements and conditions in construction, the concrete can be concentrated mixed in the construction site or station. Automatic fall type mixer can be used for the concrete mixture whose liquidity is better. Mandatory mixer is used for the concrete mixture whose liquidity is lower or the harsh concrete. Before mixed, the materials should be prepared according to the proportion and the weighting error should be controlled. Both the mixing procedure and time have influence on concrete quality so that the mixing procedure and time should be under strict control to make various components well-proportioned.
Transmission and irrigation built: the concrete mixture can be transported to the construction site by hopper, rubber belt conveyor or mixing truck. The way of built filling can use manual work or the mechanical work. Using the concrete pump to transport and irrigate concrete mixture, this method features with high efficiency, which can reach hundreds of cubic meters per hour. Both the cast-in-site concrete engineering and prefabricated part, should confirm the density of the irrigation built concrete. The methods mainly consist of: vibrating screening, centrifugation, extrusion and vacuum operation. The vibration can be left out if the liquid concrete is mixed with some efficient water reducer.
The main purpose of the maintenance is to create the proper temperature and humidity conditions so that the harden speed of normal concrete can be confirmed or sped up. Different maintenance methods of concrete have different effects on the performance of concrete. The common maintenance methods consist of: natural maintenance, steam curing, dry hot and humid maintenance, autoclaved maintenance, the electric heating maintenance, infrared maintenance and solar maintenance. The curing period is the time of maintenance. In order to be compared with conveniently, the rule is that test specimens for determining the concrete performance must be maintained in standard conditions. The standard condition of maintenance in China is that the temperature is 20±3℃ and the humidity is no less than 90%
Rock Crusher http://www.rocks-crusher.org