Retarder
Retarder turns up in 2 fields: concrete, automotive. Here is what it means to the people in each one.
Retarder in concrete
An admixture that delays setting, used in hot weather, on long hauls and for big continuous placements.
Set-retarding admixtures built on sugars, lignosulfonates or hydroxycarboxylic acids slow early cement hydration so the mix stays plastic longer. Contractors call for them on summer pours, long pump runs, mat foundations and decks where each load must blend into the last before it sets. An overdose can hold off set for a day or more, and a separate surface retarder sprayed on fresh concrete is used to expose aggregate.
"Put a half dose of retarder in the afternoon loads, the deck crew can't keep up when it's 95 and windy."
Retarder in automotive
A supplementary braking device used on heavy vehicles to maintain steady speeds on steep downgrades.
A retarder is a secondary braking system installed on heavy trucks and buses to slow the driveline without using the primary friction brakes. It operates using hydraulic fluid drag or electromagnetic induction to generate resistance against the driveshaft or transmission. This system absorbs massive amounts of kinetic energy, preventing the service brakes from overheating and failing during long downhill descents.
"Hit the retarder before we crest this grade so we don't cook the drums on the way down."