low grade material
低级别材料 low grade material
低廉的，低劣的用低级材料制成的；廉价的或质地差的。
Made of low-quality materials; cheap or shoddy.
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甚至有些低级路面也采用半刚性材料做基层。
Even some low grade pavements also use the semi-rigid base material as the base.
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