UNWANTED BALLAST
Back in my youth when I was just a boy pilot, we flew enormous quantities of freight into the New Guinea Highlands on DC3s, there was no other way, no roads, so everything went by air.
One particular DC3, known as being 'gutless', had, over the years carried literally thousands of tons of cement into the highlands. Slowly, oh so slowly, the cement dust was sifting down through the floor cracks and settling on the keel, and in the tropical humidity became hard.
At the next major overhaul, 2000 Lb of hardened cement was removed from the keel. After that, the aircraft performed just as well as any other.
A bit off topic sorry, but there's ballast you want, and ballast you definately don't want.