1. Railway manufactured sand standards: where they are stricter than ordinary construction sand
Sand for railway concrete is usually subject to "Railway Concrete" (TB/T 3275-2018), "Standard for Constructional Quality Acceptance of Railway Concrete Engineering" (TB 10424-2018), and "Manufactured Sand for Railway Concrete" (Q/CR 865-2022). During project implementation, attention should also be paid to the latest special regulations issued by China Railway Group on the application of manufactured sand concrete, such as "Technical Specification for Application of Manufactured Sand Concrete in Railway Engineering" (Q/CR 9404-2026), etc., and the latest valid version and the project technical specifications shall prevail.
Bosses should first focus on four core indicators.
The first one, crushing index
The crushing index of manufactured sand shall not exceed 25%. It reflects the ability of the sand grains themselves to resist crushing — if the crushing value exceeds the limit, it means the sand grain strength is insufficient, and the aggregate in the prepared concrete may fail before the paste under load.
Second checkpoint: stone powder content, graded and controlled by MB value
Stone powder refers to fine particles smaller than 0.075mm in manufactured sand, while mud refers to natural clay-type impurities; the MB value can be understood as a ruler for judging how much "mud" is present in the stone powder. Q/CR 865—2022 adopts dual control of "MB value + concrete strength grade" for stone powder content, with common control limits as follows: when MB is less than 0.5, stone powder may be relaxed to 15.0%; when MB is between 0.5 and 1.40, it is limited to 10.0%~5.0% according to concrete strength grade; when MB value is above 1.40, it is limited to 5.0%~2.0%. Actual implementation shall be subject to the original standard text and project technical specifications.
Third checkpoint: mud content
Classified by strength grade. Taking C50 and above as an example, mud content shall not exceed 2.0%, and mud lump content shall not exceed 0.5%; other strength grades shall be implemented according to the standard's classification. Note that mud content and stone powder content are not the same thing and must not be confused.
Fourth checkpoint: alkali reactivity
Controlled by the accelerated mortar bar expansion rate, Class 1 manufactured sand shall be less than 0.20%. If this item fails, the concrete may be slowly cracked apart in the later stage.
In addition, attention shall be paid to indicators such as particle morphology, fineness modulus, particle gradation, soundness, apparent density, and saturated surface-dry water absorption. Particle morphology generally requires roundness of not less than 0.80 and aspect ratio of not more than 1.60; the fineness modulus is set at 2.3~3.4 in Q/CR 865-2022, and premium manufactured sand shall achieve 2.3~3.0. For specific projects, the technical specifications often impose tighter limits, and the project documents shall prevail.
II. How to Produce Manufactured Sand: Three-Stage Process and Sand Making Machine Selection
The standard approach is a three-stage process: jaw crushing for primary crushing, cone crushing for secondary and tertiary crushing, and vertical shaft impact crushing for final sand making. The first two stages determine the particle size, while the last stage determines particle shape and gradation. For equipment selection in the primary crushing stage, seeSJ.E Series Jaw Crusher.
Cone crushers use inter-particle compression crushing — material is squeezed and broken inside the crushing chamber, producing well-shaped output with few elongated or flaky particles, which reduces the load on the downstream impact crusher. Fewer flaky particles mean lower load on the sand making machine and less wear part consumption — an invisible but unavoidable part of the cost per ton. For secondary and tertiary crushing equipment selection, seeSK.D Series Multi-cylinder Hydraulic Cone Crusher.
The vertical shaft impact crusher is responsible for crushing material below 5 mm into sand. Taking the Shuangjin SJ.L series as an example, the maximum feed size covers approximately 40–50 mm depending on the model, with a processing capacity of 220–700 t/h; rock-on-rock and rock-on-iron chamber types are switchable. Adjust the impeller linear speed by one setting, and the fineness modulus and stone powder content change accordingly. For sand making stage equipment selection, seeSJ.L Series Vertical Shaft Impact Sand Making Machine.
One reminder for selection: stone powder is not the less the better. 4%~6% stone powder is beneficial to concrete workability, provided there is little "mud", i.e., a low MB value. If stone powder exceeds the limit, an air classifier or dust collector can be equipped for recovery; for raw materials with heavy mud content, a sand washing stage must be added at the front end. Which route to take specifically depends on the material source and environmental assessment requirements.
III. Sand and gravel production line configuration example: How the 300 t/h line of Xinchang Jiaotou is configured
A complete railway material supply line requires five stages: coarse crushing, medium-fine crushing, sand making and shaping, screening, and dust removal. The 300 t/h sand and gravel production line of Xinchang Jiaotou in Zhejiang supplies roads and municipal projects across the county, and passed item-by-item inspection and acceptance at commissioning. The configuration logic of this line is: coarse crushing as the foundation, cone crusher for quality assurance, impact crusher for shaping.
| Process | Equipment model | Quantity | Function |
|---|---|---|---|
| Primary crushing | Jaw crusher SJ.E.75.10 | 1 unit | First-stage crushing of large stones |
| Secondary and tertiary crushing | Multi-cylinder hydraulic cone crusher SK.D.1500 | 1 unit | Laminated crushing, regular particle shape |
| Sand making and shaping | Vertical shaft impact sand making machine SJ.L.500 | 1 unit | Sand output, controlled fineness modulus |
| Screening | Circular vibrating screen | 3 units | Finished material grading |
| Environmental protection package | Pulse bag filter | 4 sets | Dry production, with full dust capture |
Table: Core configuration of the 300 t/h sand and gravel production line for Xinchang Jiaotou. A 300-ton ash storage tank is additionally provided, with dust emissions controlled within 10 mg/m³ as required by the project; the actual production line is also equipped with auxiliary equipment such as a bar feeder and a vibrating feeder.
In Ningde, Fujian, there is an 800 t/h granite production line: two jaw crushers for primary crushing, cone crushers for secondary and tertiary crushing, and two impact crushers for shaping. It produces five specifications of material, supplying large-scale projects such as expressways and railways. The larger the line, the more critical the matching of upstream and downstream equipment—primary crushing capacity, screening efficiency, and sand maker load must all be calculated in one account. No matter how well a single machine is selected, it is useless if the line is not balanced.
Conclusion
The threshold for railway sand is set, and if the indicators are not met, the material cannot enter the site. Only with the right equipment and a balanced line can the finished sand remain stable and fetch a good price.
Shuangjin was founded in Hangzhou in 1987 and has been engaged in complete sets of mining machinery equipment for over 30 years, with extensive practical engineering experience in sand makers and complete production lines. For projects requiring line configuration, you are welcome to call 400-006-1987, leave a message on our official website, or visit our Hangzhou headquarters to inspect the production line on site.