The biggest factor by far affecting the strength of concrete is the water cement/ratio. Basically the more water added, the less strength the cement paste will develop.
The biggest factor for durability of concrete is the addition of microscopic entrained air (brought about by addition of chemical additives). But too much air will reduce strength.
Placing reinforcing steel in concrete greatly increases its tensile strength.
Other factors are hot weather and cold weather especially while the concrete is still in a plastic state.
The Potrland Cement Association is the best reference for cement products:
www.cement.org
The biggest factor for durability of concrete is the addition of microscopic entrained air (brought about by addition of chemical additives). But too much air will reduce strength.
Placing reinforcing steel in concrete greatly increases its tensile strength.
Other factors are hot weather and cold weather especially while the concrete is still in a plastic state.
The Potrland Cement Association is the best reference for cement products:
www.cement.org