DURA-MIX® Concrete Driveway Study Update
As many of you who’ve been following this study recall, Concrete Alberta in partnership with Canadian Home Builders Association (CHBA) have been following the performance of four DURA-MIX® driveways poured in Northern Edmonton in the summer and late fall of 2016 under real world conditions and subject to a range of curing and sealing regimes. As we enter our second winter of our driveway study, we’d like to bring everyone up to date on what’s been observed so far.
All four driveways in the study have stood up fairly well with, in most cases, only minor flaws that can be attributed to a number of identifiable causes. The best news so far is that all four have withstood a full winter with exposure to a number of freeze thaw cycles and road salt tracking, and none have shown any signs of scaling.
Some plastic shrinkage cracking has been observed, particularly along tooled edges and joints that were left unprotected from the wind during the initial pour that may have been prevented had evaporation retarders been employed.
There are a number of drying shrinkage cracks, some quite significant, that may have been eliminated or reduced in severity had some of the control joints been tooled deeper so that they were active and at more frequent intervals as recommended under good concreting practices. Some of these cracks have continued to widen, likely due to subsidence of the subgrade over the past year.
Two cores were taken from driveway 2 this summer to confirm the air content and the adequacy of the air void system to protect the slab from freeze thaw cycling. Plastic air content on this pour was on the high side, and of the order of 9% at the chute and 11% at the end of the pump. Hardened airs were of the order of 10% from the first concrete poured to 8% in the final portion of the load. Air void spacing factors were well within spec. The only surface deterioration observed to date on this driveway was associated with roof run off from a rain event that occurred shortly after the pour.
It will be interesting to see how these four driveways stand up to another winter in Edmonton. We will be sure to keep you posted and don’t hesitate to contact our office if you have any questions or want more information on the study.