NS UNIT TRAIN

I've seen all sorts of unit trains over the last 30 or so years, but this one's got me stumped - a string of KRL heavy duty flat cars with some sort of concrete things on each car. Shot at Stryker, OH on 3/1/11 westbound. NS (ex-CR) GP-38-2 5297 leads with SD-60 6610 trailing. Anyone know what the concrete things are? If so, please send me an e-mail at bob @ railheadphotography . com. RE Holmes digital photo. See a closer look at one of the KRL (and the concrete thing) cars by clicking here.