Concrete Repair Posts

Baby carrots, F-16's and flexible epoxy

Posted by John Bors on Wed, Jun 13, 2012 @ 12:06 PM

What do F-16’s, F-18’s and baby carrots have in common? They have all landed on CCS Binder Patch, Nosing, Slurry (PNS) which is our low modulus (flexible) epoxy.F 18 lands on flexible epoxy

PNS is our most popular binder for use in repairing control joint nosings and spalls, often located in very tough applications like Navy and Air Force runways, municipal refuse handling facility floors, large vehicle repair shops, machine shops and even food processing grinding wheels.

These days, it is very popular to reuse old concrete floors in some buildings that have been repurposed from industrial use to retail or commercial. The control joints in the old floor often need repair or rebuilding. To accomplish the joint repair, a horizontal section is cut out on each side of the joint and a plastic piece is placed in the old opening as a block out, then a PNS-based grout or polymer concrete extended with aggregates is poured or troweled into the new slots on both sides of the joint.

Most of the time, PNS is extended with 4-5 volumes of gap graded aggregates to provide a durable (5000 psi) surface that is highly resistant to chipping, impacts, point loads and large temperature swings. When used as an extended binder, it has a useful working life of up to 45 minutes at 72°F, so there is time to properly place the entire batch you just mixed. It should be noted that a mortar mixer is the best way to obtain the shear needed for optimum blending of aggregates although some contractors use a rotary 5 gal pail mixer with a scraper blade. If the aggregate extension is not extreme and the application is small, a Jiffy mixer can be used in a pinch. Just don’t use a cement mixer—it does not generate sufficient shear to properly wet out the aggregates.

PNS is a very good substrate wetting binder and will bond to damp and even completely saturated concrete. It will also adhere to steel, wood, FRP and many elastomers and is ideal for bonding flexible materials to concrete. For best results, ensure that the substrate surface has no contaminants and preferably is roughened to the texture of 40 mesh sandpaper.

flexible epoxy polymer concreteWhat is the role of the aggregates? Depending on the size distribution, shape, hardness and quantity used, they can dramatically affect the placement properties, strength, wear, impact resistance and thermal behavior of the grout. Because the material is flexible and is extended, it will tolerate deeper placements than more rigid epoxy polymer concretes. It’s possible to achieve workable mixes that are only ~10% epoxy with excellent trowelable properties or you can use a slightly lower quantity of aggregates and obtain self leveling. Unlike cementitious patches, there’s rarely a bonding problem and in most cases, priming isn’t necessary. Note that it is critical that the aggregates are dry and should have less than 0.2% moisture. Please call us if you need some advice on locating the best aggregates locally—it is far more cost effective if you buy the aggregate this way rather than shipping a low cost heavy material around the country.

So what’s the deal about baby carrots? Well, we can’t reveal secrets of our best customers. We can tell you that baby carrots are formed from larger carrots that have been cut and ground. The longest-lived grinding wheels are made with a high mod epoxy and a low mod epoxy in a special combination. Similar wheels handle even harder tasks like pistachio nut hulls.

Tags: spall repair, low mod epoxy, low modulus epoxy, flexible polymer concrete, concrete overlay, concrete patch, flexible epoxy