阅读说明：本技术 用机制砂替代天然砂制备中国iso标准砂的方法及产品 (Method for preparing China ISO standard sand by using machine-made sand instead of natural sand and product ) 是由 王昕� 杜勇 张金山 郑旭 宋立春 刘潭 郭俊萍 刘晨 肖忠明 于 2020-03-26 设计创作，主要内容包括：本发明是关于用机制砂替代天然砂制备中国ISO标准砂的方法及产品,该方法包括：将机制砂原料进行第一处理,控制湿含量＜0.05％,石粉含量＜0.03％,得到1.0mm～2.0mm粒级的机制粗砂；和/或,将机制砂原料进行第二处理,控制湿含量＜0.05％,石粉含量＜0.03％,得到0.5mm～1.0mm粒级的机制中砂；和/或,将机制砂原料进行第三处理,控制湿含量＜0.05％,石粉含量＜0.03％,得到0.08mm～0.5mm粒级的机制细砂；将所述1.0mm～2.0mm粒级的机制粗砂、0.5mm～1.0mm粒级的机制中砂和0.08mm～0.5mm粒级的机制细砂一种或多种分别替代相应粒级的天然石英砂,得到中国ISO标准砂。通过对机制砂化学成分、颗粒分布、颗粒形貌等技术参数特定控制,以实现用制砂替代天然砂生产中国ISO标准砂,用于水泥胶砂强度检验。(The invention relates to a method for preparing China ISO standard sand by using machine-made sand to replace natural sand and a product, wherein the method comprises the following steps: performing first treatment on a machine-made sand raw material, controlling the moisture content to be less than 0.05 percent and the stone powder content to be less than 0.03 percent, and obtaining machine-made coarse sand with the grain size of 1.0-2.0 mm; and/or performing second treatment on the machine-made sand raw material, controlling the moisture content to be less than 0.05 percent and the stone powder content to be less than 0.03 percent, and obtaining the machine-made sand with the grain size of 0.5-1.0 mm; and/or performing third treatment on the machine-made sand raw material, controlling the moisture content to be less than 0.05 percent and the stone powder content to be less than 0.03 percent, and obtaining machine-made fine sand with the grain size of 0.08-0.5 mm; and respectively replacing one or more of the machine-made coarse sand with the size fraction of 1.0-2.0 mm, the machine-made medium sand with the size fraction of 0.5-1.0 mm and the machine-made fine sand with the size fraction of 0.08-0.5 mm with the natural quartz sand with the corresponding size fraction to obtain the Chinese ISO standard sand. The technical parameters such as chemical composition, particle distribution, particle morphology and the like of the machine-made sand are specifically controlled to realize that the manufactured sand replaces natural sand to produce the Chinese ISO standard sand for the strength test of cement mortar.)

1. A method for preparing the Chinese ISO standard sand by using machine-made sand instead of natural sand is characterized by comprising the following steps: performing first treatment on a machine-made sand raw material to ensure that the content of the more than 2.0mm size fraction is less than or equal to 1.0 percent, the content of the more than 1.6mm size fraction is (21 +/-4)%, the content of the more than 1.0mm size fraction is more than or equal to 94 percent, controlling the moisture content to be less than 0.05 percent and the stone powder content to be less than 0.03 percent, and obtaining machine-made coarse sand with the size fraction of 1.0-2.0 mm; and/or the presence of a gas in the gas,

performing second treatment on the machine-made sand raw material to ensure that the content of the grain size fraction of more than 1.0mm is less than or equal to 5 percent, the content of the grain size fraction of more than 0.5mm is less than or equal to 5 percent, controlling the moisture content to be less than 0.05 percent and the stone powder content to be less than 0.03 percent, and obtaining the machine-made sand with the grain size fraction of 0.5-1.0 mm; and/or the presence of a gas in the gas,

performing third treatment on the machine-made sand raw material to ensure that the content of the grain size fraction of more than 0.5mm is less than or equal to 5 percent, the content of the grain size fraction of more than 0.16mm is (61 +/-3 percent), the content of the grain size fraction of more than 0.08mm is more than or equal to 98 percent, controlling the moisture content to be less than 0.05 percent and the stone powder content to be less than 0.03 percent, and obtaining the machine-made fine sand with the grain size fraction of 0.08-0.5 mm;

and respectively replacing one or more of the machine-made coarse sand with the size fraction of 1.0-2.0 mm, the machine-made medium sand with the size fraction of 0.5-1.0 mm and the machine-made fine sand with the size fraction of 0.08-0.5 mm with the natural quartz sand with the corresponding size fraction to obtain the Chinese ISO standard sand.

2. The method for preparing the Chinese ISO standard sand by using the machine-made sand to replace the natural sand according to claim 1, wherein the method comprises the following steps:

the first treatment comprises crushing, screening, particle morphology improvement, water washing and drying;

the second treatment comprises crushing, screening, particle morphology improvement, water washing and drying;

and the third treatment comprises crushing, screening, particle morphology improvement, water washing and drying.

3. The method of preparing chinese ISO standard sand using machine-made sand instead of natural sand according to claim 2, wherein the crushing comprises: coarse crushing and fine crushing.

4. The method for preparing the Chinese ISO standard sand by using the machine-made sand to replace the natural sand according to claim 2, wherein the particle morphology improvement comprises impact crushing, ball milling and forced stirring, the particle roundness factor is controlled to be 0.58-0.69, and the particle repose angle is controlled to be 31.5-37.5 degrees.

5. The method for preparing ISO standard sand of china according to claim 1, wherein the raw material of the machine-made sand is quartzite, granite or feldspar instead of natural sand.

6. A China ISO standard sand prepared by using machine-made sand to replace natural sand is characterized in that the particle size distribution of the machine-made sand is as follows:

the content of a size fraction of >2.0mm is 0%,

the content of the size fraction of >1.6mm is (7 +/-5)%,

the content of the size fraction of >1.0mm is (33. + -. 5)%,

the content of the size fraction of >0.5mm is (67. + -.5)%,

the content of the grain size fraction of >0.16mm is (97 +/-5)%,

the content of the grain size fraction of >0.08mm is (99 +/-1)%,

wherein the particle roundness factor of the machine-made sand is 0.58-0.69, and the particle angle of repose is 31.5-37.5 degrees.

7. The manufactured ISO standard sand of china prepared using machine-made sand in place of natural sand of claim 6 wherein the machine-made sand has a moisture content of < 0.05%.

8. The ISO standard sand of china prepared using machine-made sand instead of natural sand according to claim 6, wherein the stone dust content of the machine-made sand is < 0.03%.

9. The manufactured ISO standard sand of china prepared using machine-made sand instead of natural sand according to claim 6, wherein the raw material of the machine-made sand is quartzite, granite or feldspar.

10. The manufactured ISO standard sand of china prepared by using machine-made sand instead of natural sand according to claim 6, which is used for cement strength test.

Technical Field

The invention relates to the technical field of building materials, in particular to a method for preparing China ISO standard sand by using machine-made sand instead of natural sand and a product.

Background

China is a world cement production country, and the annual cement yield accounts for about 60% of the total world cement yield. The cement strength detection is an important basis for evaluating the quality of cement products, the standard sand is an indispensable standard sample in the quality detection of the cement products, the accuracy and the reliability of cement strength detection results are directly related, and the method is a key for scientifically evaluating the quality of the cement products.

In order to ensure the stable quality of standard sand products, natural quartz sand is adopted by all countries in the world to produce and prepare ISO standard sand. The standard sand for cement strength inspection in China complies with the standard specification of the GB/T17671-1999 cement mortar strength inspection method (ISO method), and is produced and prepared from high-purity natural quartz sand. However, with the enhancement of the protection consciousness of natural resources of the environment in China in recent years, the exploitation and long-term stable supply and exploitation of the natural quartz sand face the completion challenge.

At present, although the research and application of the machine-made sand to replace natural quartz sand in the concrete industry are mature, the standard sand for cement strength inspection has more strict quality requirements and higher requirements on the accuracy and stability of the cement strength inspection, and the standard sand prepared by the machine-made sand hardly meets the requirements on the cement strength inspection, so the research and application in the cement industry are relatively less.

Disclosure of Invention

The invention mainly aims to provide a method for preparing Chinese ISO standard sand by using machine-made sand instead of natural sand and a product, and aims to solve the technical problem that the standard sand prepared by using machine-made sand hardly meets the requirement of cement strength inspection.

The purpose of the invention and the technical problem to be solved are realized by adopting the following technical scheme.

The method for preparing the Chinese ISO standard sand by using the machine-made sand to replace the natural sand comprises the following steps: performing first treatment on a machine-made sand raw material to ensure that the content of the more than 2.0mm size fraction is less than or equal to 1.0 percent, the content of the more than 1.6mm size fraction is (21 +/-4)%, the content of the more than 1.0mm size fraction is more than or equal to 94 percent, controlling the moisture content to be less than 0.05 percent and the stone powder content to be less than 0.03 percent, and obtaining machine-made coarse sand with the size fraction of 1.0-2.0 mm; and/or the presence of a gas in the gas,

performing second treatment on the machine-made sand raw material to ensure that the content of the grain size fraction of more than 1.0mm is less than or equal to 5 percent, the content of the grain size fraction of more than 0.5mm is less than or equal to 5 percent, controlling the moisture content to be less than 0.05 percent and the stone powder content to be less than 0.03 percent, and obtaining the machine-made sand with the grain size fraction of 0.5-1.0 mm; and/or the presence of a gas in the gas,

performing third treatment on the machine-made sand raw material to ensure that the content of the grain size fraction of more than 0.5mm is less than or equal to 5 percent, the content of the grain size fraction of more than 0.16mm is (61 +/-3 percent), the content of the grain size fraction of more than 0.08mm is more than or equal to 98 percent, controlling the moisture content to be less than 0.05 percent and the stone powder content to be less than 0.03 percent, and obtaining the machine-made fine sand with the grain size fraction of 0.08-0.5 mm;

and respectively replacing one or more of the machine-made coarse sand with the size fraction of 1.0-2.0 mm, the machine-made medium sand with the size fraction of 0.5-1.0 mm and the machine-made fine sand with the size fraction of 0.08-0.5 mm with the natural quartz sand with the corresponding size fraction to obtain the Chinese ISO standard sand.

The object of the present invention and the technical problems solved thereby can be further achieved by the following technical measures.

Preferably, the method for preparing the Chinese ISO standard sand by using the machine-made sand instead of the natural sand comprises the following steps of crushing, screening, improving the particle morphology, washing and drying;

the second treatment comprises crushing, screening, particle morphology improvement, water washing and drying;

and the third treatment comprises crushing, screening, particle morphology improvement, water washing and drying.

Preferably, the method for preparing the ISO standard sand of china using machine-made sand instead of natural sand as described above, wherein the crushing comprises: coarse crushing and fine crushing.

Preferably, the method for preparing the Chinese ISO standard sand by using the machine-made sand instead of the natural sand comprises the steps of impact crushing, ball milling and forced stirring, wherein the particle morphology improvement comprises the steps of controlling the particle roundness coefficient to be 0.58-0.69 and controlling the particle repose angle to be 31.5-37.5 degrees.

Preferably, the method for preparing the Chinese ISO standard sand by using the machine-made sand instead of the natural sand is implemented, wherein the raw material of the machine-made sand is quartzite, granite or feldspar.

The object of the present invention and the technical problem to be solved are also achieved by the following technical means. According to the invention, the machine-made sand is used for replacing natural sand to prepare the Chinese ISO standard sand, and the granularity distribution of the machine-made sand is as follows:

the content of a size fraction of >2.0mm is 0%,

the content of the size fraction of >1.6mm is (7 +/-5)%,

the content of the size fraction of >1.0mm is (33. + -. 5)%,

the content of the size fraction of >0.5mm is (67. + -.5)%,

the content of the grain size fraction of >0.16mm is (97 +/-5)%,

the content of the grain size fraction of >0.08mm is (99 +/-1)%,

wherein the particle roundness factor of the machine-made sand is 0.58-0.69, and the particle angle of repose is 31.5-37.5 degrees.

The object of the present invention and the technical problems solved thereby can be further achieved by the following technical measures.

Preferably, the aforementioned china ISO standard sand prepared by using machine-made sand instead of natural sand, wherein the machine-made sand has a moisture content of < 0.05%.

Preferably, the machine-made sand replaces the natural sand prepared China ISO standard sand, wherein the stone dust content of the machine-made sand is less than 0.03%.

Preferably, the raw material of the machine-made sand is quartzite, granite or feldspar instead of the natural sand prepared China ISO standard sand.

Preferably, the aforementioned china ISO standard sand prepared by using machine-made sand instead of natural sand is used for cement strength test.

By the technical scheme, the method for preparing the Chinese ISO standard sand by using the machine-made sand to replace the natural sand and the product have the advantages that:

1. according to the method for preparing the Chinese ISO standard sand by using the machine-made sand to replace the natural sand, the technical parameters such as chemical components, particle distribution, particle morphology and the like of the machine-made sand are specifically controlled, so that the machine-made sand is used for replacing the natural sand to produce the Chinese ISO standard sand and is used for testing the strength of cement mortar.

2. When the machine-made sand is used for replacing the corresponding natural sand to prepare the Chinese ISO standard sand for testing the strength of the cement mortar, the 28-day strength D values of the standard sand of different types of cement are all less than 2.5 (the lowest value is 0.4), and the accuracy and the reproducibility of the test result are good; and the fluidity difference of the cement mortar is less than 10mm, the performance of the cement mortar is basically consistent with that of ISO standard sand, and the cement mortar conforms to the regulation of a GB/T17671-1999 cement mortar strength test method (ISO method).

3. The method has the advantages of simplicity, convenience, low cost and reliable performance, and the machine-made sand is used for replacing natural sand to be successfully applied to the preparation of the ISO standard sand, so that a new way is provided for the stable production of the ISO standard sand in China, a technical guarantee is provided for the smooth implementation of a cement strength detection method and the scientific evaluation of the quality of cement products in China, and an important positive effect is played on the healthy sustainable development of the cement industry in China.

The foregoing is a summary of the present invention, and in order to provide a clear understanding of the technical means of the present invention and to be implemented in accordance with the present specification, the following is a detailed description of the preferred embodiments of the present invention.

Drawings

FIG. 1 is a graph showing the effect of stone dust content in the machine-made sand of the present invention on the D value of 28-day strength;

FIG. 2 is a graph showing the influence of stone dust content in the machine-made sand on the fluidity of cement mortar;

FIG. 3 is a graph showing the relationship between the angle of repose of the machine-made coarse sand and the fluidity of the cement mortar.

Detailed Description

To further illustrate the technical means and effects of the present invention adopted to achieve the predetermined objects, the following detailed description will be given to the method for preparing the ISO standard sand of china by using machine-made sand instead of natural sand and the implementation, structure, features and effects thereof according to the present invention in combination with the preferred embodiments. In the following description, different "one embodiment" or "an embodiment" refers to not necessarily the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

The embodiment of the invention provides a method for preparing China ISO standard sand by using machine-made sand to replace natural sand, which comprises the following steps:

s1, performing first treatment on the machine-made sand raw material to ensure that the content of the more than 2.0mm size fraction is less than or equal to 1.0 percent, the content of the more than 1.6mm size fraction is (21 +/-4 percent), the content of the more than 1.0mm size fraction is more than or equal to 94 percent, controlling the moisture content to be less than 0.05 percent and the stone powder content to be less than 0.03 percent, and obtaining machine-made coarse sand with the size fraction of 1.0-2.0 mm; and/or the presence of a gas in the gas,

s2, carrying out second treatment on the machine-made sand raw material to ensure that the content of the grain size fraction of more than 1.0mm is less than or equal to 5 percent, the content of the grain size fraction of more than 0.5mm is less than or equal to 5 percent, controlling the moisture content to be less than 0.05 percent and the stone powder content to be less than 0.03 percent, and obtaining the machine-made medium sand with the grain size fraction of 0.5-1.0 mm; and/or the presence of a gas in the gas,

s3, carrying out third treatment on the machine-made sand raw material to ensure that the content of the grain size fraction of more than 0.5mm is less than or equal to 5 percent, the content of the grain size fraction of more than 0.16mm is (61 +/-3 percent), the content of the grain size fraction of more than 0.08mm is more than or equal to 98 percent, controlling the moisture content to be less than 0.05 percent and the stone powder content to be less than 0.03 percent, and obtaining the machine-made fine sand with the grain size fraction of 0.08-0.5 mm;

s4, replacing the natural quartz sand of the corresponding size fraction with one or more of the machine-made coarse sand of the size fraction of 1.0-2.0 mm, the machine-made medium sand of the size fraction of 0.5-1.0 mm and the machine-made fine sand of the size fraction of 0.08-0.5 mm respectively to obtain the Chinese ISO standard sand.

In the embodiment of the invention, the reason why the moisture content in the control sand is less than 0.05 percent and the stone powder content is less than 0.03 percent is that: (1) the moisture content has a great influence on the accuracy of standard sand measurement. The moisture content is less than 0.05 percent, so that the moisture content is consistent with the daily production quality control of the current standard sand, and unnecessary test errors are reduced; (2) the content of the stone powder is a main influence factor of the quality of the machine-made sand, and has important influence on the strength development of cement mortar and the rheological property of mortar. The content of stone powder is large, the water requirement of cement mortar is increased, and the rheological property is high. As shown in figure 1, when the content of stone powder in the machine-made sand is increased from 0.02% to 0.20% of water, the fluidity of the cement mortar is obviously deteriorated, and the fluidity is increased and reduced by more than 10 mm; at the same time, the strength of the cement changes to different degrees in 28 days, and the D value is increased from 1.7 to 3.0 (exceeding the relevant requirement in the standard, namely that D is less than or equal to 2.5). Therefore, the content of the machine-made sand powder needs to be strictly controlled, and is preferably less than 0.03%.

It is important to point out that, in the present application, the steps of preparing the machine-made coarse sand, the machine-made medium sand and the machine-made fine sand are not strictly limited in order, and when in use, one or more of the machine-made coarse sand, the machine-made medium sand and the machine-made fine sand are prepared as required and used for respectively replacing natural quartz sand of corresponding size fraction to obtain the chinese ISO standard sand. When the machine-made sand is used for replacing the natural quartz sand of the corresponding grade, the machine-made sand is also used for replacing the natural quartz sand coarse sand according to the requirement, the machine-made coarse sand is used for replacing the natural quartz sand coarse sand, the machine-made sand is used for replacing the natural quartz sand medium sand, the machine-made fine sand is used for replacing the natural quartz sand fine sand, any two kinds of the natural quartz sand of the corresponding grade are used for replacing the natural quartz sand of the corresponding grade, or three kinds of the natural quartz sand of the corresponding grade are simultaneously and respectively replaced according to the actual requirement.

As a preferred embodiment, the first treatment comprises crushing, screening, particle morphology modification, water washing and drying;

the second treatment comprises crushing, screening, particle morphology improvement, water washing and drying;

and the third treatment comprises crushing, screening, particle morphology improvement, water washing and drying.

It should be noted that although the first treatment, the second treatment and the third treatment are all performed by the same treatment method, the specific treatment processes are different, and different specific parameters, such as crushing degree, screening mesh number and the like, are required for preparing machine-made sand with different size fractions.

Although the first treatment, the second treatment and the third treatment adopt technical means commonly used in the field, the specific control of technical parameters such as chemical composition, particle distribution, particle morphology and the like of the machine-made sand prepared by processing is a key for realizing the production of the Chinese ISO standard sand by replacing natural sand with the machine-made sand, and the machine-made sand is used for testing the strength of cement mortar. Experiments prove that after the machine-made quartz sand prepared by the technology replaces corresponding grain-size natural sand in ISO standard sand, the 28-day strength D values of the standard sand of different types of cement are all less than 2.5 (the lowest value is only 0.4); and the fluidity difference of the cement mortar is less than 10mm, the performance of the cement mortar is basically consistent with that of ISO standard sand, and the cement mortar conforms to the regulation of a GB/T17671-1999 cement mortar strength test method (ISO method).

As a preferred embodiment, the disruption comprises: coarse crushing and fine crushing.

Coarse and fine crushing are also carried out by means of techniques commonly used in the art.

As a preferred embodiment, the particle morphology improvement comprises impact crushing, ball milling and forced stirring, the particle roundness factor is controlled to be 0.58-0.69, and the particle repose angle is controlled to be 31.5-37.5 degrees.

The natural sand is formed under natural conditions, the particle surface is smooth, the edges and corners are few, so the natural standard sand can be prepared only by washing, screening and drying, and the particle composition, the impurity content, the moisture content and the like of the natural standard sand are controlled in daily production. Different from natural sand, the machine-made sand is prepared by manually crushing, washing, screening and the like raw materials, the particle surface is rough, the particle shape is sharp and has multiple edges, micro-cracks possibly exist in the particle, and the machine-made sand has certain difference on the performance of the natural sand. Therefore, to ensure that the performance of the machine-made sand is similar to that of natural standard sand, the particle morphology of the machine-made sand needs to be strictly controlled and is characterized by a particle roundness factor and an angle of repose.

As the round coefficient of the particles is increased, the rheological property of the cement mortar and the development of the cement strength are improved. The more the particle morphology of the machine-made sand is improved, namely the more the edges of the particles are reduced and the edges are smooth, the closer the performance of the machine-made sand is to the natural standard sand, and the more the embodiment of the invention controls the particle roundness coefficient to be not more than 0.69. This is mainly due to the fact that natural sand has a smooth surface and few edges and corners, but is not a round particle. The solid particles have different forms, the close packing degrees are different, the standard sand particles mainly play a role of aggregate in the cement paste, the combination of the paste and the surface of the paste has important influence on the cement strength, the particle forms are different, and the performances of the cement mortar are also different. At present, the roundness factor of natural coarse sand particles is basically about 0.69. The shape of the artificially prepared machine-made sand particles needs to be strictly controlled, the particles are over-round, the binding capacity of the cement paste and the surface of the cement paste is reduced, the interaction resistance is reduced, the cement strength is low, the mobility of the mortar is too high, and the accuracy of a test result is influenced to a certain extent.

The machine-made coarse sand particle repose angle and the cement mortar fluidity have a good linear relation, and when the repose angle is reduced, the cement mortar fluidity is improved. When the angle of repose of the machine-made sand is less than 37.5 degrees, the difference between the fluidity of the cement mortar and the fluidity of the natural standard sand is small. The angle of repose is a macroscopic manifestation of the particle surface roughness, and the size of the angle of repose is closely related to the solid particle morphology. The angle of repose was too small, indicating a smoother particle surface. At present, the angle of repose of natural coarse sand is about 31.4 degrees. If the angle of repose of the machine-made sand is too small, the surface of the modified particles is too smooth, and the shape of the modified particles is greatly different from that of natural particles.

As a preferred embodiment, the machine-made sand feedstock is quartzite, granite, or feldspar.

Selecting machine-made sand raw materials according to actual needs, mining and transportation convenience, price and other reasonsSiO in the material₂The contents were different. The main raw material of the machine-made sand is quartz rock preferably; when the main raw material is granite, SiO is preferably used₂The content is more than or equal to 60 percent.

In the embodiment of the invention, quartzite (SiO) is preferably selected₂The content is more than or equal to 97.0 percent) is prepared into sand by a raw material preparation machine, and the main purpose is to ensure that the chemical components of the machine-made sand are close to those of natural sand, thereby reducing the influence of other factors on the test result.

According to the method for preparing the Chinese ISO standard sand by using the machine-made sand to replace the natural sand, the technical parameters such as chemical components, particle distribution, particle morphology and the like of the machine-made sand are specifically controlled, so that the Chinese ISO standard sand is produced by using the machine-made sand to replace the natural sand and is used for testing the strength of cement mortar.

The embodiment of the invention also provides the Chinese ISO standard sand prepared by using the machine-made sand to replace natural sand, wherein the particle size distribution of the machine-made sand is as follows:

the content of a size fraction of >2.0mm is 0%,

the content of the size fraction of >1.6mm is (7 +/-5)%,

the content of the size fraction of >1.0mm is (33. + -. 5)%,

the content of the size fraction of >0.5mm is (67. + -.5)%,

the content of the grain size fraction of >0.16mm is (97 +/-5)%,

the content of the grain size fraction of >0.08mm is (99 +/-1)%,

wherein the particle roundness factor of the machine-made sand is 0.58-0.69, and the particle angle of repose is 31.5-37.5 degrees.

The particle roundness factor and particle angle of repose of the machine-made sand are quantitative characterizations of the morphology of the machine-made sand particles. The size of the angle of repose is closely related to the solid particle morphology. The angle of repose was too small, indicating a smoother particle surface. The too large round coefficient of the particles and the too small angle of repose of the machine-made sand indicate that the improved surfaces of the particles are too smooth, have larger shape difference with natural particles and show larger performance difference.

As a preferred embodiment, the moisture content of the machine-made sand is < 0.05%.

As a preferred embodiment, the stone dust content of the machine-made sand is < 0.03%.

As a preferred embodiment, the machine-made sand feedstock is quartzite, granite, or feldspar.

As a preferred embodiment, the Chinese ISO standard sand prepared by using the machine-made sand instead of natural sand is used for testing the strength of cement.

Experiments prove that after the machine-made quartz sand prepared by the technology replaces corresponding grain-size natural sand in ISO standard sand, the 28-day strength D values of the standard sand of different types of cement are less than 2.5 and only 0.4 at least, and the accuracy and reproducibility of detection results are good; and the fluidity difference of the cement mortar is less than 10mm, the performance of the cement mortar is basically consistent with that of ISO standard sand, and the cement mortar conforms to the regulation of a GB/T17671-1999 cement mortar strength test method (ISO method).

The present invention will be further described with reference to the following specific examples, which should not be construed as limiting the scope of the invention, but rather as providing those skilled in the art with certain insubstantial modifications and adaptations of the invention based on the teachings of the invention set forth herein.

The methods used in the following examples are conventional methods unless otherwise specified.