What is the probability of popouts due to stresses incurred by freezing and thawing in a slab of regular-aggregate concrete that has been roll-abugged prior to bull floating as compared with a slab of crushed stone or white rock concrete?
Although we are not familiar with the specific characteristics of the particular aggregates used in your area, the key point regarding the aggregate is whether or not it is sufficiently porous to be the cause of popouts. Any kind of particle that absorbs a significant amount of water tends to cause popouts after freezing and thawing. One example of an aggregate causing popouts is chert. If you are using sand and gravel they may contain a miscellaneous collection of rocks, some more porous than others. In such a case the more absorptive particles might cause popouts while the others do not. If you are using crushed stone that is relatively uniform in composition and nonporous you will probably have no difficulty with popouts. In general, the more deeply the aggregate is embedded in the concrete the less likely it is to cause a popout. When a concrete contains porous aggregate, it is sometimes recommended that a topping of concrete containing no porous aggregate be put over it; the topping protects the aggregate below from absorbing any significant amount of water and causing popouts. The use of a roll-a-bug might cause deeper embedment of coarse, absorptive particles and thus tend to reduce the amount of trouble with popouts. It is, of course, desirable to keep the slump low and use an adequate air content in the mix not only to resist damage from freezing and thawing but also to prevent scaling due to application of deicers.