limestone or river gravel aggregate in concrete?

Around here (SW Wisconsin) a truckload of river gravel costs about 5 times as much as limestone gravel. But conventional wisdom dictates that we use river gravel because the limestone supposedly somehow chemically reacts with the cement to make an inferior product.

On the other hand, I have seen some good old concrete made with limestone gravel. What gives? why does everyone pay more for aggregate? Is their a lost recipe for cement to mix with limestone?

Are you sure you mean river gravel ? Much of the sand in Wisconsin comes from glacial deposits. The individual grains are more angular and give a stronger cement than does river sand.

They could be paying more for the river gravel aggregate out of habit. The architects could simply be unwilling to break with tradition and try something different. It could also be the ready mix plants aren’t willing to take a cance and change the batch design they are using. It could even be something as far out as the river gravel is being washed by a company owned by someone who is well connected politically. Something along the lines of “use my material, or you don’t get any more contracts.” It’s amazing some of the crap that goes on behind the scenes when decisions are being made as to what materials or fixtures go into a project. I have been told that the angular shape of the individual rocks gives better results in the cylinder break test.