Analysis on advantages and disadvantages of manufactured sand by hydroxypropyl methylcellulose manufacturers

At present, there is a shortage of sand and stone in some areas of China, the supply of sand and stone is insufficient, and the price of sand and stone is rising, which has seriously affected all links of the construction industry. In order to speed up the construction period, some projects take risks and use inferior sand and gravel, sand and gravel of unknown origin and other phenomena from time to time. These problems have seriously affected the safety of the project. So, what kind of machine-made sand belongs to inferior machine-made sand? How to judge? The following introduces several categories of low-quality machine-made sand and which rocks are suitable and unsuitable for the production of machine-made sand.

Severely weathered

The phenomenon of rock fragmentation, looseness and secondary change of mineral composition under the action of solar radiation, atmosphere, water and biology is called "Weathering", which generally includes physical weathering, chemical weathering and biological weathering. It refers to the machine-made sand produced by strongly weathered hard rock. This kind of sand has poor firmness, large water demand (specific hydroxypropyl methylcellulose and other water retaining agents need to be added), poor adhesion with cement slurry, and poor performance indexes of produced concrete.

Clay minerals

The main minerals that make up clay rock and soil are some silicate minerals mainly containing aluminum and magnesium, which generally have layered structure, water absorption and ion exchange. Several types of clay minerals that do great harm to manufactured sand are mainly montmorillonite, bornite, kaolinite and so on.

1. Montmorillonite

Layered minerals composed of very fine hydrous aluminosilicates, also known as Jiaoling stone and microcrystalline kaolinite, are formed by weathering and alteration of igneous rocks such as volcanic condensate in alkaline environment. They are the main component of bentonite, white, sometimes slightly red or green. Strong water absorption, volume expansion several times to more than ten times after water absorption, with strong adsorption and cation exchange performance.

2. Bornite

It is also called bentonite and bentonite rock. A fine-grained clay with montmorillonite as the main component, containing a small amount of feldspar, quartz, Bede, calcite and pyroclastic powder. It has strong water absorption, and the volume expands 10 ~ 30 times after water absorption.

3. Kaolinite

A hydroxyl containing aluminum silicate mineral, a dense block in the form of very small microcrystals or cryptocrystalline crystals. Kaolinite is the product of low-temperature hydrothermal alteration and secondary weathering of aluminosilicates such as feldspar and mica. It is common in the weathering crust of magmatic and metamorphic rocks. It has extremely complete cleavage and water absorption when dry, but does not expand.

Containing harmful impurities

Including organic matter, shale, gypsum, iron oxide, coal, light matter particles, soft particles, mica, sulfide, sulfate, chloride ion, etc. these impurities are extremely unfavorable to the strength and durability of concrete. For example, organic matter is mostly the product of plant decay, which can greatly reduce the early strength of concrete; Shale has weak weathering resistance and can not withstand freeze-thaw cycle damage; Gypsum in aggregate has potential sulfate attack and TSA attack; Iron oxide impurities will leave ugly color spots if exposed on the concrete surface; Coal particles have high adsorption and no strength, and holes will be left after dissolution; Light matter particles include plant roots, plant fibers, etc. if they exist on the concrete surface, they will leave holes and color spots; Weak particles will lead to the crushing of concrete, the decline of strength, durability and wear resistance, and may also be crushed during mixing to increase water consumption (specific water retaining agents such as hydroxypropyl methylcellulose need to be added).

Containing active substances

Free calcium oxide and free magnesium oxide in steel slag aggregate; Overburned lime particles in waste slag of waste lime yard; Pyrite, pyrrhotite (ferrous sulfide), alkali active aggregate, etc. these active components will undergo chemical reaction after concrete hardening, and the volume expansion of reaction products will cause damage to concrete.

Mud content exceeding standard

The overburden of the parent rock formation zone is too thick, the intercalated soil is rich, and the rocks are not integrated and dispersed in the soil. Mining is like selecting stones from the soil. Such rock stratum is most suitable for water stable layer, Even if wet (water washing) production, the mud content of machine-made sand and mud block content exceed the standard. Mud and mud block can reduce the workability of concrete and affect the compression, crack resistance, bending resistance, permeability, frost resistance, elastic modulus and shrinkage of concrete. The higher the concrete strength, the greater the impact. After the mud block dissolves, it will leave scaly holes on the hardened concrete surface, affect the durability, and the mud block will break during mixing Crushing will increase water consumption (specific water retaining agents such as hydroxypropyl methylcellulose need to be added).

Irregular grain class

The crushing process and equipment selection are unreasonable. Generally, the two-stage crushing process of coarse crushing and fine crushing is simply adopted in small mines, and no shaping process is designed, such as Hubei crushing + cone crushing. This two-stage crushing process combination produces more irregular particles for sand and gravel products produced by most rock types. The production of fine manufactured sand generally adopts at least three-stage crushing process of coarse crushing + fine crushing + ultra-fine crushing (shaping) and multi-stage screening process. The combination form of crushing process and equipment shall be selected according to the characteristics, cleavage, strength and hardness of rock.

Graded broken class

The particle size distribution in the sand is uneven and discontinuous, showing a state of "more at both ends and less in the middle", such as stone chips, some natural sand with incomplete screening, mountain sand without crushing and screening processing, and the particles below 0.315mm are washed away in the process of wet production water washing, leaving only the machine-made sand above 0.315. The concrete prepared by this graded broken molding sand has poor workability, It is easy to separate, and the sand rate is usually very high. Some ultra-fine sand must be added or the amount of admixture powder must be adjusted to make up for the broken gap of fine particles in the sand.

Parent rock radioactivity exceeding standard

The key reason for poor quality manufactured sand is the poor quality of parent rock, followed by unreasonable processing technology and equipment, as well as the lack of supervision system and inspection control means. In order to produce high-quality machine-made sand and ensure the quality of concrete, great attention should be paid to the quality of parent rock. Before setting up mining rights, investing in mine construction and purchasing sand and gravel materials, the quality of parent rock must be comprehensively analyzed and inspected, and concrete trial mixing test must be carried out.

Shandong chuangyao Biotechnology Co., Ltd. specializes in the production and operation of hydroxypropyl methylcellulose and other powder building materials additives. Welcome to leave a message.