How to produce high quality artificial sand?

How to produce high quality artificial sand?

With the increasing number of construction projects in China, the amount of concrete is increasing, and the demand for sand is also increasing. However, over-exploitation has depleted China ’s natural sand and gravel resources and it is difficult to meet the demand. The increasing demand for sand and gravel in various industries has led to the emergence of artificial sand. High-quality artificial sand can meet the different sand use needs of different construction projects. So how to produce high-quality artificial sand? Need to start from the following aspects: material selection, equipment, technology, quality control, etc.

First, make a good selection of base materials

01. The parent rock used for processing artificial sands must not have the potential to react with alkaline aggregates, and the compressive strength should not be lower than 80 MPa. It should be produced using clean, hard texture, no weak particles, and no weathered rocks. Before selecting the material, the rock base material should be sampled and tested. The compressive strength, lithology, sulfide, and sulfate content of the rock must meet the requirements to ensure that the quality of the base material is acceptable.

There are many raw materials that can be used as mechanism sand. Generally, there are granite, basalt, river pebble, cobblestone, limestone, calcite, andesite, rhyolite, diorite, glauconite, sandstone, tailings, slag, quartzite, etc., different. The artificial sand made of high-quality rock has different strengths and granularities, and the corresponding uses will also be different. The following is a general description of the use of several kinds of ore to make sand:

artificial sand materials

02. The mud content and mud content in artificial sand are mainly caused by the sand that produces the sand. When mining is carried out, the vegetation and soil on the surface should be cleaned to prevent weathered sand, mud and other debris from being mixed into it. During the feeding process, the block stone should be further screened by a vibrating feeder. The screened out soil and small pieces of crushed stone should be treated as waste, and cannot be mixed into the sand for use.

03. The scraps produced after the production of crushed stones are processed into artificial sand or stone powder and stones, which can effectively supply the sand and stone aggregate market and form a circular industrial chain. Not only has achieved good economic benefits, but also effectively solved problems such as wastewater pollution and resource waste.

Production process of artificial sand

The basic production process can generally be divided into the following stages: Mining stones → coarse crushing → medium crushing (partial screening) → fine crushing → screening → dust removal → artificial sand.

main equipment of sand making production line

Common production crushing processes and equipment combinations are:

High-quality artificial sand production process:

At present, there are three main production methods for stone powder separation: dry method, wet method and semi-dry method. Dry production adopts wind-selected stone powder. Through wind separation technology, particle size adjustment and stone powder screening are realized.

Sand washing machine is used to wash stone powder in wet production. The equipment mainly includes wheel and spiral sand washing machines. Because the wheel sand making machine has less loss of fine-grained sand and stone powder, the produced sand has a relatively better gradation.

Advantages and disadvantages of two dust removal methods

The dry sand production process has low moisture content and high yield, but it is difficult to control the fineness and stone powder content, and the finished materials are prone to segregation. The wet sand production process is easy to control, but pollutes the environment The output is low, which is likely to cause unqualified grading and large fineness modulus.

Third, particle gradation control

The grain shape of the mechanism sand is mainly affected by the lithological joint development of the parent rock, the type of crushing equipment and the screen type. The rock lithology of the parent rock affects the rock crushing surface and the degree of crushing. Shape control is better.

Grain grading of machine sand can be achieved by adjusting the feed gradation, feed amount, crusher speed, screen size and other aspects.

Fourth, fineness modulus control

artificial sand specifications

At present, the general requirement for fineness modulus of mechanical sand is zone 2 (medium sand). Through practice, the diameter of the screen mesh of the machine-made sand produced by the dry process is easily controlled below 5mm, and the diameter of the screen mesh of the water-washed machine sand is easily controlled below 3.2mm. However, the diameter of the sand screen of the water washing mechanism is controlled at 4mm, which can greatly increase the output, but the fineness modulus reaches 3 zones (coarse sand), and it can be achieved by mixing with natural 1 zone (fine sand) to 2 zone (medium sand).

Screen types generally use square-hole screens as much as possible, which is very beneficial for particle shape control. Round-hole screens or long screens can be used less frequently. It is also necessary to constantly monitor the screen for blockage and damage to the instability of the fineness modulus. .

Five, stone powder content control

According to the requirements of the test specification, when the value is less than 1.4, the content of vermiculite powder below C45 is ≤7.0%; the content of vermiculite powder above C50 is ≤5.0%. However, different national standards are different. For example, the US standard specifies an ideal limit for stone powder content of 5-7%, and the British standard is 15%.

The smaller the fineness modulus of the machine sand, the finer the particles as a whole, and the more the stone powder content, it is not desirable to reduce the fineness modulus simply by increasing the stone powder content in production. Because these two technical indicators have disappeared and conflicted with each other, it is necessary to find a range where both meet the requirements of the specification.

The dry production method adjusts the stone powder content interval by adjusting the production equipment parameters, and the wet production method adjusts the water injection amount and the speed of the sand washing machine. Both methods need to be combined with the actual situation, trial production multiple times, and continue to make specific adjustments to the amount of sand washing machine or air sieve to meet the requirements of grading and stone powder of machine sand.

Six. Control measures for segregation of mechanical sand

Practice has proved that the mechanism of sand separation is more serious, resulting in large differences in gradation and fineness index before and after entering the market. For example, this phenomenon exists in some construction bid sections of Zhengwan Railway. The fineness of inspection in the production process of the mining area meets the requirements, but unqualified samples often appear in the warehouse.

For dry production, wet mixing treatment should be performed. A water spray device can be installed on the belt conveyor, but it is necessary to avoid excessive concentration of stone powder and small particle size particles caused by excessive water spray.

The finished product sand is reasonably stacked, and the ascending inclined stacking method is adopted to prevent small particles from slipping and accumulating. The inclined slope should be reasonably set according to the area of the reservoir and the height of the accumulation. Choose a relatively flat public transportation road, try to smooth the construction access road into the concrete station area, properly control the vehicle speed, and reduce the mechanism sand caused by vehicle bumps. During the unloading process, try to raise the box as much as possible to facilitate the rapid decline of the material and reduce the accumulation of coarse particles of the material to the outside.

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