Understanding Crushed Stone Specifications: to Quality Construction

Crushed stone is a fundamental building block of modern infrastructure, forming the backbone of roads, nền móng, hệ thống thoát nước, và bê tông. Its performance and longevity are critically dependent on meeting precise specifications. Understanding these specifications – often detailed in documents titled "Specification of Crushed Stone" or similar – is essential for engineers, nhà thầu, and suppliers to ensure project success and durability.

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Unlike naturally occurring gravel, crushed stone is produced by mechanically breaking down larger rocks. This process allows for greater control over the final product's physical properties. Specifications define the exact requirements the crushed stone must meet for a particular application. Using stone that doesn't conform can lead to:

Lỗi kết cấu: Weak aggregate in concrete or insufficiently compacted base layers can collapse.
Premature Deterioration: Poor resistance to wear (ví dụ., on road surfaces) or weathering leads to costly early repairs.
Drainage Problems: Incorrect gradation can cause water pooling or erosion.
Construction Difficulties: Stone that is too dusty hinders compaction; oversized stones are hard to place and finish.

Parameters Defined in Specifications

A comprehensive crushed stone specification will typically address the following critical characteristics:

1. Cấp độ (Phân bố kích thước hạt):
This defines the range of particle sizes present and their relative proportions.

Specified by sieve analysis results (ví dụ., passing percentages through various mesh sizes like 1", 3/4", 3/8", No.4, No.200).
Different applications demand specific gradations: well-graded for base courses (providing interlock and stability), uniformly graded for drainage layers, or gap-graded for specialized applications like asphalt surface courses.
Common nominal sizes include 57, 67, 78, 8, vân vân., each with defined size ranges.

2. Sạch sẽ / Deleterious Materials:
Limits are set on harmful substances like clay lumps, friable particles (dễ dàng sụp đổ), đá phiến sét, than đá, lightweight pieces (ví dụ., chert), và chất hữu cơ.
Excessive fines (material passing the No.200 sieve - often clay or silt) are strictly controlled as they can weaken bonds in concrete/asphalt and impede drainage/compaction in bases.

3. Độ chắc chắn / Độ bền:
Measures resistance to weathering cycles like freezing and