2277 Longyang Rd. Pudong, Shanghai, China info@mixingchina.com

Manufactured Sand, Principal Properties of Manufactured Sand

    You are currently here!
  • Home
  • Blog Manufactured Sand, Principal Properties of Manufactured Sand

Manufactured Sand, Principal Properties of Manufactured Sand

June 21, 2023 nflg 0 Comments

In this report the term manufactured sand is used for aggregate material less than 4 mm that is processed from crushed rock or gravel and intended for construction use. Manufactured sand is a material of high quality, in contradiction to non-refined surplus from coarse aggregate production. By using the Internet in search for information of this topic it is evident that a variety of terms are used for this or similar product internationally, including:

• Manufactured stone sand
• Manufactured fine aggregate
• Crushed fine aggregate
• Crusher sand
• Crushed rock sand
• Stone sand
• Stone powder
• Quarry fines
• Quarry sand
• Artificial sand
• Leftover rocks from mining and quarrying
• Surplus materials

In addition different other languages operate with other definitions of manufactured sand. The term sand refers to relatively small particles; however, there are some variations in the definitions of sand with regard to particle size. According to geological terminology sand is of the particle size 63 μm – 2 mm but in the practical life of aggregate production material ranging from 0/4 mm, 0/8 mm, 0/10 mm and even 0/12 mm is often called sand. In the context of this report, material of the particle size 0/4 mm is referred to as sand and this reflects the common practice.

According to the machinery producer Nordberg (1999)3, now Metso, manufactured sand has been used for many years in a variety of concrete applications including waterway and dam projects, highway and airport paving, bridges, power plants, all types of industrial and commercial construction, and concrete products (pipes, blocks and precast) of all kind. Manufactured sand is also used in plasters and mortars, where sand has a full role as aggregate. Furthermore, sand is used partly in asphalt, road building, earth fillings, bricks, glass etc. Table 1-1 shows aggregates average utilization in the world.

Destination Proportion
Ready mix concrete (30% sand) 36 %
Mortars 18 %
Pre‐cast concrete (25‐35% sand) 12 %
Asphalt (35‐45%) 9 %
Sub‐bases 18 %
Ballast 2 %
Others 5 %

Principal Properties of Manufactured Sand

The Particle Size Distribution (PSD) curve of manufactured sand is more often than not dense. In an optimal crushing process it is possible to obtain particles which are cubical and angular, but with a rough surface texture. Lithology has not so much impact on geometric properties for the sand fraction, i.e. 63 μm – 4 mm, however it may govern these properties for the fines. The effects of secondary minerals on properties and quality of the fines, for use in for instance concrete, are only partly known.

Properties of aggregates from natural sand and gravel deposits (natural aggregates) differ compared to aggregates from crushed rock (crushed aggregates). Natural aggregates are weathered and their surface is often smooth and particles are sub angular to rounded.

Crushed aggregates on the other hand have a rough surface texture, particles are angular and, if the production process is adequate, their shape is cubical. However, with traditional crushing techniques a high content of flaky and/or elongated particles may occur especially in the particle size range < 8mm. This difference in surface texture and shape properties indicates that natural and crushed aggregates are two different types of material and must be treated accordingly, i.e. different requirements apply to the two types, for instance regarding particle size distribution. Knowledge and experience for natural aggregates can for instance not be used without suitable adjustments.

The PSD curve, for manufactured sand normally resembles a Füller curve, i.e. is hanging or dense with high proportions of fines content, opposite to what is normal for natural sand. A dense PSD in concrete sand can reduce the water requirement, and thereby improve workability – given the fines content is not too high.

On the other hand, if the particle shape is sharp/flaky, a dense grading may cause a harsh mix, requiring much fines to compensate the voids content – again increasing the water demand. So this is a tight balance to be played with the parameters in each case. Often good results have been obtained with a blend of natural and manufactured sand, in which case an optimised grading curve as well as a mix of rounded and sharp particles can give a better solution than any of the singular alternatives.

The first and basic issues will be related to the raw material – the inventory, classification and excavating. Material parameters will depend on the parent rock, whether the aggregates are excavated and crushed from hard rock, or they are present as sand/gravel deposits of one kind or the other. Geological parameters such as rock type/mineral composition and texture, weathering, contamination and sediment structure, will always be the initial criteria for selection and evaluation of resources.

The production process, comprising initial transport, crushing, sorting and storage, will then be the decisive stage in providing a useful aggregate. Adequate production equipment and methods, based on the geological conditions given, are key elements in obtaining the necessary results.

leave a comment