The difference between river sand, machine-made sand, and tailings sand

2021-05-28

At present, there are many types of sand on the market, and the price difference is relatively large. You need to understand them when buying sand
River sand properties and uses.

River sand
River sand is a non-metallic ore with complicated composition, smooth surface and high impurity content, which is produced by rocks washed by water for a long time. River sand particles are smooth, relatively clean, and come from a wide range of sources. Uses: River sand is cement standard sand, which is mostly used in construction, concrete, cementitious materials, road construction materials, artificial marble, cement physical performance inspection materials (ie cement standard sand), etc. The configured concrete mixture slurry is rich, full and dense, with good fluidity.

Machine-made sand

The machine-made sand refers to the rock particles whose particle size is less than 4.75mm after being broken by machinery. The finished product is more regular and can be processed into sand of different rules and sizes according to different technological requirements. The paste has the strongest binding force in concrete and can better meet daily needs.

Construction waste Recycled aggregate

Simple crushing of construction waste recycled aggregate has many edges and corners, rough surface, and hardened cement mortar in its components. In addition, the damage accumulated in the concrete block during the crushing process causes a large number of micro-cracks in the interior, resulting in the pores of the construction waste recycled aggregate itself It can not be used on a large scale due to its high rate, high water absorption rate, high bulk porosity, high crushing index value, and low bulk density.

Sea sand

After desalination treatment, sea sand with a chloride ion content of not more than 0.02% can be used in engineering.

Sand making from waste residues and tailings

At present, steel slag sand and quicklime granular sand are currently used in the market. The disadvantages of these two types of sand are poor volume stability or high heavy metal ion content, high post-processing costs and high quality risks.

Utilization of iron tailings sand
The chemical composition of iron tailings is SiO, which amounts to 65% to 75%, and FeB% to 14%. They are high-silicon and high-iron tailings and generally do not contain price-associated elements. Its main component is quartz, a small amount of hornblende, chlorite, biotite, calcite and dolomite. They are generally crushed and classified, with finer particles and good gradation, and some have certain chemical activity due to a certain degree of calcination or chemical treatment.

The iron-phase minerals in iron tailings mostly exist in the form of magnetite, and the content fluctuates depending on the process, generally below 10%, and 10%-20% in the case of backward process. Iron tailings sand also contains a small amount of other metals, mostly in the form of stable oxides.

a) The screening of iron tailings is medium-coarse, and the gradation can meet the standard requirements; after screening, the tailings belong to the single-grain gradation of 16-25mm, with more particles above 19.0mm and fewer particles below 16.0mm.

b) The surface morphology of iron tailings sand and gravel particles is rough, and the concrete prepared with tailings sand has poorer workability than ordinary concrete and is easy to segregate.

c) Iron tailings sand and gravel can be used in the preparation of C50 concrete. The 7d compressive strength is slightly lower than that of ordinary concrete, and the 28d strength is basically close to the strength of ordinary concrete.

d) The frost resistance, water penetration resistance, and chloride ion penetration resistance of iron tailings and gravel concrete are better than ordinary concrete.