Certain recurring problems can be readily prevented by an adjustment in the concrete mix or in the construction practices.
THE PLASTIC MIX
Bleeding--Just after concrete has been placed, sometimes an excessive amount of water rises to the surface, bringing with it very fine material, cement and sand.
Harsh finishing--This is very likely a problem caused by coarse sand, possibly in a mix having a low cement content.
Sticky finishing--This could be from an overabundance of fines.
Low air content in air-entrained concrete--There are several factors that will change the air content even though the amount of air-entraining agent remains the same.
Slump adjustment--When concrete reaches the job, some water may have to be added to bring the slump up to the level permitted.
Setting time--Rapid setting becomes a problem in hot weather. A retarding admixture is used to delay the set.
Plastic cracking--Plastic cracks often occur as numerous parallel cracks several inches to several feet in length.
Shrinkage cracking--This is the cracking that occurs with the loss of moisture from the concrete after it has hardened and from volume change (shrinkage) that occurs when the concrete is cooled by lower air temperatures. The cracking can be controlled by providing control joints.
Pavement scaling occurs in the vast majority of cases on non-air-entrained concrete exposed to freezing and thawing and the application of salt or calcium chloride as deicing agents during the winter season.