Shape and size: –
- Shape and Size of the aggregates decides the cement required for concrete. This means If shape and size of the aggregates are good then concrete will need optimum cement hence concrete will be economical.
- Maximum size of aggregates reduces the quantity of cement required.
- Size and shape directly impacts strength of the concrete as well. Workability of fresh concrete, Segregation control all these can be achieved with good quality of aggregates.
- Flaky or elongated aggregates may lead to segregation.
- Rounded shapes of aggregates will help to maintain water cement ration for concrete
- Texture of the surface is also an important property of the aggregates. Texture of the surface can be Glassy, Smooth, Granular, Crystalline, Or Porous.
- Texture or surface of the aggregates have significant impacts on requirement of water for Concrete making.
- Workability of the fresh concrete is also impacts with respect to the texture of the aggregates.
- Rough texture aggregates are found to form more strong bonds with cement paste than another textured aggregate due to the presence of voids and pores.
- On the other hand, glass, smooth aggregates absorb less water than rough aggregates which may influence the water requirement as mentioned above.
Specific Gravity: –
- The ratio of weight of oven dried aggregates maintained for 24 hours at a temperature of 100 to 1100C, to the weight of equal volume of water displaced by saturated dry surface aggregate is known as specific gravity of aggregates.
- Specific gravities are primarily of two types.
- Apparent specific gravity
- Bulk specific gravity
- Specific gravity is a mean to decide the suitability of the aggregate. Low specific gravity generally indicates porous, weak and absorptive materials, whereas high specific gravity indicates materials of good quality.
- Specific gravity of major aggregates falls within the range of 2.6 to 2.9.
- Specific gravity values are also used while designing concrete mix.
Bulk Density: –
- Bulk density or also called unit weight or unit mass is the density of the aggregate at a certain degree of compaction.
- It is measured in kg/Cum.
- Bulk Density of the aggregates are depends on the particle size distribution and shape of particles.
- Porosity of the aggregates may be formed at the time of aggregate formation.
- Porous aggregates required water for itself to fill the pours, hence porous aggregates concrete required more water.
- Porous concrete is good in binding.
Water absorption: –
- Water absorption or water content of the aggregates decides the water required for the concrete formation.
- Water content may change the physical properties like Impact, Crushing and abrasion value of aggregates.
- Water cement ratio is less for aggregates having more water content.