What is a Concrete Aggregate?

Concrete aggregate refers to granular loose materials that play a role of skeleton or filling in concrete. Divided into coarse and fine aggregate. Coarse aggregate refers to pebble, crushed stone, etc., and fine aggregate refers to natural sand, artificial sand, etc.

Concrete aggregate

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Concrete aggregate refers to granular loose materials that play a role of skeleton or filling in concrete. Divided into coarse and fine aggregate. Coarse aggregate refers to pebble, crushed stone, etc., and fine aggregate refers to natural sand, artificial sand, etc.

Aggregates with a particle size greater than 4.75 mm are called coarse aggregates, commonly known as stones. There are two types of gravel and pebble. Crushed stone is made of natural rock or rock by mechanical crushing and sieving, and the particle size is larger than 4.75 mm. Pebble is a rock particle with a particle size greater than 4.75 mm formed by natural weathering, water transport and sorting, and accumulation. Pebble and crushed stone particles are longer than the average particle size of the corresponding particle size of 2.4 times the needle-like particles; thickness less than 0.4 times the average particle size is flaky particles (average particle size refers to the upper and lower limit of the size Diameter). Construction pebbles and crushed stones should meet the technical requirements of the national standard GB / T 14685-2001 "Construction Pebbles and Crushed Stones".

Aggregates with a particle size of less than 4.75 mm are called fine aggregates and are commonly called sand. Sand is divided into natural sand and artificial sand according to the source of production. Natural sand is rock particles with a particle size of less than 4.75 mm formed by natural weathering, water transport, sorting, and accumulation, but does not include particles of soft rocks and weathered rocks. Natural sand includes river sand, lake sand, mountain sand, and desalinated sea sand. Artificial sand is a collective name for machine-made sand and mixed sand treated with soil removal.

Quality requirements of fine aggregates (artificial sand, natural sand) in the Code for Construction of Hydraulic Concrete (DL / T5144-2015):

1 The fine aggregate should be hard, clean and well graded; the fineness modulus of artificial sand should be in the range of 2.4 to 2.8, and the fineness modulus of natural sand should be in the range of 2.2 to 3.0. The use of mountain sand, coarse sand, corresponding experimental demonstration should be taken.

2 During the mining process, the fine aggregate should be tested for alkali activity regularly or according to a certain amount of mining. In the period of potential harm, corresponding measures should be taken and verified by special tests.

3 The moisture content of the fine aggregate should be kept stable. The moisture content of the dry surface of the artificial sand should not exceed 6%. If necessary, accelerated dehydration measures should be taken.