RAP
RAP turns up in 2 fields: asphalt, metallurgy. Here is what it means to the people in each one.
RAP in asphalt
Reclaimed asphalt pavement: old asphalt milled or crushed and fed back into new mix as aggregate and binder.
Reclaimed asphalt pavement, the processed material from milling or tearing up old asphalt, crushed and screened into stockpiles and metered into new mix through its own feed. RAP brings back both aggregate and aged binder, which cuts virgin binder and stone costs, but the old binder is stiff, so high-RAP mixes get a softer virgin grade or a rejuvenator. Mixes commonly carry 15 to 30 percent RAP, with surface lifts held to the low end, and plants often split it into coarse and fine fractions to control gradation.
"RAP pile's soaked from last night's rain, drum's going to burn a ton of fuel and run cold till it dries out."
Rap in metallurgy
To strike a casting pattern lightly to free it from the sand mold.
Rapping involves tapping a wooden or metal pattern with a mallet or rapping bar before drawing it out of the sand. The vibration slightly enlarges the mold cavity and breaks the surface tension, allowing the pattern to lift out cleanly without tearing the sand walls. Excessive rapping can distort the final casting dimensions.
"Give the corebox a good rap before you try to pull it, or you'll tear the sand."