The aggregate size most commonly used in construction is 20mm, 40mm and 75mm. 20mm aggregate size is used in RCC structures, 40mm aggregate size is used in PCC structures or mass concreting and 75mm and more size is used in retaining wall construction. Coarse-grained aggregates are all aggregates larger than 4.75 mm in size per piece. This includes boulders, cobblestones, and gravel.
Fine or crushed gravel is usually 4 to 8 mm; medium or partially crushed gravel measures 8 to 16 mm; coarse-grained or uncrushed gravel measures 16 to 64 mm; pavers measure 64 to 256 mm; and rocks have anything above 256 In general, aggregate of diameter range of 9.5-37.5 mm is used in concrete work RCC. But the maximum aggregate size generally used on the site is 40 mm. To facilitate compaction and workability, aggregates of 10-15 mm are sometimes used on site. There are mainly two types of aggregates that are used in civil engineering construction work to prepare concrete. Concrete is used for different purposes, such as foundations, pavements, etc.
About 40 to 80 percent of concrete is composed of aggregates. Therefore, the aggregates used in concrete must be free of dust, clay, organic materials such as vegetables, leaves, etc. They must be washed clearly with the aid of non-acidic water before use to prepare the concrete. Vermiculite concrete aggregate is used to create a lightweight, insulating concrete that can be used in various forms of foundations suitable for a variety of engineering designs. The ancient river sediment has been reworked by the action of the sea to leave clean and well-classified aggregates.
In general, smaller coarse-grated aggregates are needed for stronger concrete, with 20mm aggregates meeting the threshold for strong concrete and 40mm aggregates for normal strength concrete. For reinforced concrete slabs, such as bridge decks, deck slabs and columns, and prestressed concrete elements, the MSA (Maximum Aggregate Size) is 16 to 20 mm. Aggregates greatly influence freshly mixed and hardened concrete properties, mix ratios and economy. In your contract, construction or purchase agreement, the term “maximum aggregate size” refers to the smallest sieve that 100% of your aggregate can pass through. To obtain a good concrete mix, aggregates must be clean, hard and strong particles, free of absorbed chemicals or coatings of clay and other fine materials that could cause concrete deterioration. The alkali content and type of aggregate in the system are likely to be unknown, and therefore, if mixed with unsuitable materials, a risk of alkali-silica reaction is possible.
Recycled concrete as an aggregate will generally have higher absorption and lower specific gravity than natural aggregate and will produce concrete with slightly higher drying shrinkage and creep. Therefore, it is essential to know the aggregates in depth to study more about concrete.