ballast
BAL-uhst
/ˈbæləst/
Crushed stone or gravel used to form the bed upon which railway ties and tracks are laid, providing stability and drainage.
In rail engineering, it specifically means angular crushed rock engineered to lock together under load.
The story behind the word. Originally a maritime term from Middle Low German meaning 'bare load'—weight added to ships when empty of cargo to maintain stability. Early railway engineers borrowed the term when using crushed stone beds to hold timber ties firmly in place.
Word relationships
- aggregate: Aggregate is a general civil engineering term for construction stone; ballast refers specifically to trackbed stone or stabilizing weight.
Commonly confused with
- gravel: Gravel consists of naturally weathered, rounded stones, whereas ballast uses crushed, angular basalt or granite.
Word family
- ballasting (noun): The process of laying or compacting track stone.
Collocations
- track ballast
- ballast bed
- ballast tamper
- ballast cleaning
Example sentences
- "Heavy rain caused soil erosion beneath the track, requiring maintenance crews to pack fresh ballast under the sleepers." Civil Engineering
Memory hook
BALancing the LASTing stability of the tracks with heavy stones. Heavy stone bed providing balance and support.
When not to use
Do not use for smooth round river pebbles; railway ballast must be crushed, angular stone to interlock properly.
Fun facts
- Without ballast rock, rail tracks would bend, warp, and sink into the soil under the extreme dynamic weight of freight trains.
Related words
Explore more words
embankment, bale, locomotive, culvert, foundation, substrate
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