Why we use aggregates in concrete?
Apr 19, 2017
Being the manufactured, recycled or natural filler in concrete, aggregate play a more critical role than what is commonly assumed by many. The term is used for any particulate material that includes sand, slag, gravel, crushed stone, geosynthetic aggregates and recycled concrete.
It accounts for approximately 60 to 80 percent of concrete’s volume and between 75 and 80 percent of its weight, and that is why the filler theory came to be. However, some of the top qualities of concrete originate from the presence of aggregate, and these are dimensional stability, and elastic and thermal properties and others.
Since the proportion of aggregate in concrete is highest and being the least expensive material used, builders can measure the economic impact that results. The final cost of concrete can, thus be lowered, depending on the ratio of aggregate used. You can also lower construction costs by selecting large, coarse aggregate because such a move will reduce cement requirements considerably. Note that cement is the costliest component in a concrete mixture.
There are certain types of construction projects that have to possess aesthetics, in addition to practicality. In such cases, exposed-aggregate concrete is required to give off an appealing appearance.
The aggregate used here has to be of a particular colour, shape, texture and overall appearance if it is to serve the purpose intended appropriately. Natural stones such as limestone, basalt, marble, quartz and granite are perfect for such uses.
Aggregates have been found to offer volume stability to a concrete mixture that has hardened. Note that aggregate has a lower shrinkage potential than cement, which is a quality that prevents the possibility of cracking of the concrete surface.
Depending on the results desired, building experts will choose the texture and shape of aggregate because it affects workability to a significant extent. For instance, the use of rounded and smooth aggregate makes concrete more workable than when elongated, angular or rough alternatives are used. The former types also result in the use of less cement when builders are coming up with workable mixtures and are commonly the gravel and sand that you will find in seashores and river beds.
Builders prefer them because they require little cement when making concrete. On the other hand, the elongated and angular types are sourced from crushed stone and require a lot of cement to come up with workable mixtures. However, they are preferred due to their desirable bond characteristics and the fact that they have high surface-to-volume ratios.
Overall, aggregates are useful in making concrete economical, in addition to determining the physical features of the resultant mixture. The varying characteristics of different aggregate types are what contribute to such effects. With the differing properties that aggregate exhibits, builders and contractors are given the flexibility to satisfy the numerous construction and design requirements of their projects.