Utilization of Iron Ore Tailings as Fine Aggregates in Concrete

For countries with large iron ore resources such as Australia, Brazil, and South Africa, there will always be a large amount of iron ore tailings after the beneficiation process of iron ore. These tailings are the main raw materials of construction waste, which has greatly caused waste of resources and environmental pollution.

The study found that using iron ore tailings as fine aggregate to produce concrete is an effective solution. This aggregate concrete exhibited good mechanical strength and even in the case of compressive strength, there was an improvement of 11.56% over conventional aggregate concrete.

This blog seeks to add value to the tailings by utilizing iron ore tailings as fine aggregate in concrete.

How to make concrete aggregate from iron ore tailings?

If the iron ore tailings are used as fine aggregate, a certain particle size is required. Coarse sand makes the concrete relatively dry, reduces viscosity, and has poor workability. Ultra-fine sand not only makes the concrete very easy to segregate, but also requires a large amount of water, thereby increasing the amount of cement.

Production Process:

Step 1 Reduce mineral particle size

The iron ore tailings are crushed by a crusher and become lumps of a certain size. It enters the ball mill and wet milling with water.

Fine grinding before beneficiation can dissociate the iron-containing mineral monomers, thereby improving the magnetic separation effect.

Step 2 Beneficiation

The joint beneficiation method of gravity separation and magnetic separation is adopted to improve the recovery rate and grade of iron tailings.

• Gravity separation: Through the pre-enrichment by a shaking table, it can improve the magnetic select recovery rate and remove mud and impurities.
• Magnetic separation: Since iron tailings often contain magnetite and weakly magnetic hematite and limonite, a magnetic separator is used for separation. After sorting, it becomes iron tailings sand.

Iron tailings sand is a kind of fine aggregate with material properties similar to natural river sand. Its particle size is relatively uniform, the fineness modulus is generally 0.7-2.2, and the surface is rough and angular.

Step 3 Washing sand

If the impurity content of the iron tailings sand is too high to meet the production requirements, the sand can be further washed.

According to the impurity content, fineness and process capacity of iron tailings sand, choose the appropriate sand washing machine.

• The wheel-type sand washing machine: It is used for fine tailing sand with a low impurity rate and low output.
• The spiral washing machine: High impurity rate, fine and coarse particles, and high output.

Step 4 Prepare concrete

Raw materials are prepared to make high-strength concrete materials. Take the iron tailings concrete prepared by Ftmmachinery as an example:

Raw materials

• Cement: Ordinary Portland cement. Know more about the cement grinding station.
• Aggregate: (1) Fine aggregate: Mixed sand of iron tailing sand and artificial sand. Among them, the fineness modulus of artificial sand is 3.1-3.3, and the stone powder content is less than 10.0%. For the iron tailing sand, its fineness modulus is 1.5-2.0 and the mixing amount is 70%. (2) Coarse aggregate: 5-25mm crushed stone.
• Admixtures:  Secondary fly ash, slag powder, etc.
• Wate reducer: polycarboxylate high-performance water reducer. The water reducing rate is 28%, the chloride ion content is 0.04%, the total alkali content is 1.91%, and the pH value is 6.89.
• Water: Tap water for drinking, meeting the mixing water requirements stipulated in the concrete water standard.

Mix ratio design

• Ordinary gravel was used as coarse aggregates.
• Artificial sand and 70% iron tailing sand were used as fine aggregates.
• Fly ash and slag powder were used to replace part of the cement.
• Concrete was prepared according to a fixed water-binder ratio.
• The 28-day compressive strength of this aggregate concrete reached 97.63MPa.

Conclusion

For iron ore and concrete producers, using iron ore tailings as fine aggregate to produce concrete is an effective method of recovering iron ore tailings.

Iron tailings can be made into iron tailing sand, which is mixed with conventional aggregates such as artificial sand to produce concrete that meets demand, such as C50 concrete. This kind of aggregate concrete has better frost resistance, water penetration resistance, and chloride ion penetration resistance than ordinary concrete.