With the increasing number of construction projects in my country, the amount of concrete is increasing, and the demand for sand is also increasing. High-quality manufactured sand can meet the needs of different construction projects. So how to get high-quality machine-made sand? It needs to start from the following six aspects: material selection, technology, quality control, stone powder content control, phenomenon control, process & equipment, etc.
1. Choice Of Material
The parent rock used for processing manufactured sand shall not have potential alkali-aggregate reactivity, and its compressive strength shall not be less than 80MPa. Before the material selection, the rock parent 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 parent material is qualified. Many raw materials can be manufactured sand, generally granite, basalt, river pebbles, cobblestone, limestone, calcite, andesite, rhyolite, diorite, diabase, sandstone, tailings, slag, quartz stone, etc. sand making production line. The artificial sand made of different rocks has differences in strength and particle size, and the corresponding uses will also be different.
The mud blocks in the manufactured sand are mainly entrained by the boulders that produce the sand. When mining the mine, the surface vegetation and mud should be removed to prevent the sundries such as weathered sand and mud from being mixed into it. During the feeding process, the block stone should be further screened by the vibrating feeder to remove the soil, and the screened soil and small pieces of gravel should be treated as waste, and cannot be mixed into the sand for use.
After the production of crushed stone, the leftovers are processed into machine-made sand or stone powder and stones, which can effectively supply the sand and gravel aggregate market and form a circular industrial chain. It not only achieved good economic benefits, but also effectively solved the problems of waste water pollution and resource waste.
2. Particle gradation (fineness modulus) control
Currently, the general requirement for the fineness modulus of manufactured sand is zone 2 (medium sand). Through practice, the screen aperture of dry-processed sand can be easily controlled below 5mm, and the screen aperture of water-washed manufactured sand can be easily controlled below 3.2mm. However, the aperture of the water-washed machine-made sand screen is controlled at 4mm, which can greatly increase the output, but the fineness modulus reaches zone 3 (coarse sand), which can be mixed with natural zone 1 (fine sand) to reach zone 2 (medium sand).
The shape of the machine-made sand is mainly affected by factors such as the development of lithological joints in the parent rock, the type of crushing equipment and the type of screen. The lithology of the parent rock affects the rock crushing surface and degree of crushing. The square-hole screen has better control of particle shape.
3. Stone powder content control
In the production process of machine-made sand, a small amount of stone powder with particles less than 0.075mm is inevitably attached. According to the quality standard of natural sand, particles smaller than 0.075mm are defined as mud, and the content limit of mud is very strict. The stone powder in machine-made sand is different from mud. Many experimental studies and engineering application practices show that a certain amount of stone powder in machine-made sand is of great help in improving the working performance of low- and medium-strength concrete, and has little effect on the strength of concrete. However, when the content of stone powder is high, it hurts the preparation of high-strength concrete. So removing and controlling the excess stone powder in manufactured sand is one of the key steps in producing manufactured sand.
The smaller the fineness modulus of machine-made sand, the finer the particles as a whole, and the more stone powder content. It is not advisable to simply increase the stone powder content to reduce the fineness modulus in production. Since these two technical indicators conflict, it is necessary to seek an interval where both meet the requirements of the specification.
The crushing index of manufactured sand is used to measure the ability of manufactured sand to resist crushing under gradually increasing loads to evaluate its applicability in engineering and is an important indicator to indirectly express the firmness of manufactured sand. The crushing index directly affects the strength of the prepared concrete, especially for high-strength concrete.
4. Crushing index control
The crushing index value of machine-made sand with better particle shape ranges from 20% to 25%. The content of needle flakes in machine-made sand is most sensitive to the crushing index value. The crushing index value of machine-made sand is generally above 30%, or even higher. For mixing ordinary concrete, machine-made sand with crushing index value below 30% should be used. The production control measures mainly select the rock with high compressive strength of parent rock and good rock mass integrity to make sand.
5. Segregation phenomenon control measures
The finished manufactured sand should be stacked reasonably, and the escalating inclined stacking method should be adopted to prevent the small particle size from slipping and accumulating. Choose a relatively flat public transportation road, try to level the construction access road into the concrete station area, properly control the speed of the vehicle, and reduce the segregation of machine-made sand caused by the bumping of the vehicle. During the unloading process, try to elevate the box to facilitate the rapid sliding of the material and reduce the accumulation of coarse particles of the material on the outside.
6. Manufactured Sand Production Process & Equipment
The basic production process can generally be divided into the following stages: ore hopper → coarse crushing → medium crushing (partially set screening) → fine crushing → screening → dust removal → machine-made sand.
The common crushing process and equipment combination produced are:
a. Jaw Crusher + Impact Crusher;
b. Jaw Crusher + Cone Crusher;
c. Jaw Crusher + Roll Crusher;
d. Jaw crusher + impact crusher + impact sand making machine;
e. Jaw crusher + Cone crusher + Impact sand-making machine or sand making system.
High-quality machine-made sand production process:
I. According to the separation method of stone powder, it can be divided into “wet sand making”, “dry sand making” and “semi-dry sand making”;
II. According to the technological process, it can be divided into “separate sand making” and “joint sand making”;
III. According to the structural form, it can be divided into “planar sand making” and “floor sand making.”
At present, there are three main production methods of stone powder separation: dry method, wet method and semi-dry method. Dry production adopts wind separation of stone powder, and through wind separation process, particle size adjustment and stone powder screening are realized;
In wet production, sand washing machine is used to wash stone powder. The equipment mainly includes wheel and spiral sand washing machine. Because the loss of fine-grained sand and stone powder is less, the produced machine-made sand is relatively well-graded.
There are many varieties of diversified ore sources for machine-made sand, so that machine-made sand can meet the needs of various industries. Most of the sand and gravel aggregates continue to rise, the production of machine-made sand has received strong support from various industries, and the demand has increased. The production of machine-made sand is not only energy-saving and environmentally friendly, but also can be produced and applied on a large scale. And you can use all kinds of waste resources, which is in line with the scientific development concept and circular economy, to maximize your benefits. Our process and equipment can guarantee the quality stability and controllability of finished products. Fixed and mobile crushers can be customized according to site conditions. Contact us for factory prices!