Save my name, email and website in this browser for the next time I comment. Notify me of new posts by email. Enter your email and receive new publications. First of all, the definition of the maximum aggregate size in concrete is the smallest sieve that 100% of the aggregates will pass through.
The nominal aggregate size is the smallest screen that can hold more than 15% of total aggregates, although it is sometimes taken as the next screen size below the maximum aggregate size. Using the nominal maximum aggregate size avoids any problems with very small amounts of slightly oversized aggregates that clash the entire classification of coarse-grained aggregates in a higher band, which is not really appropriate. Maximum size of the coarse-grained aggregate used in the CCR. BS EN 13877-1 limits the maximum aggregate size to one-third of the slab depth, and this is consistent with U.S.
standards and general practice around the world, although some agencies may have slightly different restrictions. In a mass concrete or PCC work, the use of larger aggregates will be useful due to the lower consumption of cement, this will also reduce the heat of hydration and the corresponding thermal stresses and shrinkage cracks. There is also some evidence that pavements constructed with smaller coarse-sized aggregates generally achieve more uniform flexural strength than those constructed with very large coarse-grained aggregates. This is the best, perfect, ideal and standard size aggregate used in PCC, such as the construction of pavement, road, walkway, or PCC driveway.
This is a more onerous restriction than in U.S. standards that specify a maximum aggregate size of ¾ of the minimum spacing. However, there are a number of factors that need to be considered when specifying particularly large aggregates for concrete work. The designer can decide if the maximum aggregate size is likely to cause problems with closely spaced reinforcement in reinforced concrete.
All kinds of aggregate made of igneous rock crushed from igneous rock, granite rock, sedimentary rock and metamorphic rock, all kinds of aggregate unit in different purposes for the construction of pavements, roads, streets and buildings and interior and exterior design of the house. For this reason, most national standards limit the maximum aggregate size to a proportion of the slab depth. The optimum maximum aggregate size should be determined both by the desired properties of the fresh and hardened concrete and by physical limitations. Therefore, in applications where the flexural strength of concrete is critical to the design, a smaller aggregate size may be more appropriate despite the mechanical performance benefits of larger aggregates.
The aggregates should be small enough to easily pass through and around the voids in the steel reinforcement during compaction to avoid any voids around the bars or honeycombs at the edges of the concrete. Usually, the most common size of aggregate used in RCC structure, such as roof slab, column, beam and bridge deck, is 20 mm. 20 mm aggregate size used in RCC structure, 40 mm aggregate size used in PCC structure or mass concreting, and 75 mm and more size used in construction of retaining walls. When the aggregate is sieved through a size of 4.75 mm, the aggregate that is retained is known as coarse-grained aggregate.