What is type G concrete?

Type G is a type of shrinkage-compensating concrete that is used:

(1) to compensate for volume decrease due to drying shrinkage,

(2) to induce tensile stress in reinforcement, and

(3) to stabilize long-term dimensions of post-tensioned concrete structures.

One of the major advantages of using expansive cement is in the control and reduction of drying-shrinkage cracks. In recent years, shrinkage-compensating concrete has been of particular interest in bridge deck construction, where crack development must be minimized."

-http://www.cement.org/basics/concretebasics_history.asp

(Other expansive concretes do exist but are largely unavailable to the United States due to cost.) 

Better Than Type K?

Expansive Concrete is the term used for a concrete mix that is designed to reduce or eliminate cracks and curling due to dry shrinkage. 

You may have heard of type K concrete and in more recent years, type G. These classes of concrete are designed to create a stronger slab and reduce or eliminate cracking due to dry shrinkage.

Here is a comparison of the two types:

Expansion curve by percentage of Type G expansive component in the mixture:

(courtesy of Green Umbrella Systems™)

Additional Information on Type G: