Stable entrained air
Entrained air is critical for freeze/thaw protection but bubbles can be lost during pumping or extended mixing, when used in mixes with high carbon content from ash, or by interference with other admixtures. A new air-entraining system called Miracon appears to produce stable entrained air regardless of these factors. The polymer-based chemical is injected into the mix from a patented bubble generator. The “Tough Air” also can be used to create lightweight concrete or flowable fill.
U.S. Concrete is licensing its patented Aridus rapid-drying concrete nationwide to ready-mixed concrete producers. Once a mix design has been developed, Aridus is guaranteed to attain ASTM F 710 recommendations for moisture vapor emission rate (MVER) of 3 lbs./1000 sq. ft./24 hours and an internal relative humidity (RH) of 75% within 45 days after placement. U.S. Concrete’s Ken Nigro says that it is the first concrete to solve the problem of vapor emissions. He reports that Aridus also has negligible curling and results in greater strength and less shrinkage than standard slab mixes. Placing and finishing is similar to other low water-cement-ratio concrete with admixtures to increase slump. When combined with a quality vapor barrier, Aridus is warranted to maintain low MVER and RH for five years.
Decorative concrete market
A recent survey cosponsored by Concrete Construction and the Portland Cement Association assesses attitudes about decorative concrete. We’ll have a full review of this survey in the December issue, but one interesting response concerns what different groups see as decorative’s most marketable attributes. Contractors report that customers choose decorative concrete mostly for aesthetics (80% say this is a reason, no surprise there), but also for its durability (75%) and because it alleviates the need for other finishes (56%). Material suppliers also find that aesthetics (81%), durability (64%), and alleviates need for other finishes (44%) are the top three attributes.
App of the Month
OSHA Construction Safety Auditing