Econocrete

[7515325]

Getting ready to place some Econocrete, Lean Mix. Spec calls for 1200 @ 28 day. If strength exceeds 1200 spec requires us to saw the joints in the econocrete. 28 day breaks came in at an average of 1130 psi. I was wondering if sawing the joints exactly on the same pattern that the 14" PCC will be will cause a problem? I was thinking they should be offset a very small amount. Like 2" or so. Should we even saw them? ANy info will be appreciated. SB

 

[Ron]

You should saw the joints and they should correspond to the same joint pattern as the overlying concrete. Don't offset them.

The reason you should saw the joints is that the Econocrete strength gain doesn't stop at 28 days...it will continue. Many lower strength concretes will achieve 1500 to 2000 psi in a year or so, depending on the mix, the aggregates and moisture conditions.

Offsetting the joints can cause more differential shear between the upper and lower concrete from drying shrinkage than keeping the joints the same.