Deicers and New Concrete

Every year the topic of new concrete and what type of deicing materials should property owners use on icy or snowy surfaces starts to be heard around the store like that nagging feeling about what gift to get your better half for Christmas.

Home owners ask us what deicing materials are “safe” for their new concrete or existing concrete walks and we customarily tell them not to use salt especially on “new” concrete.

“What do you suggest?’ they would ask.  “Sand or Grit are safe alternatives.’  We reply.   This is a great response but they can get messy and do not work as fast or easy as deicing materials.  Property owners want to stay out of possible litigation from today’s excessively expensive court system and keep their pathways safe and slip-free but little else can be used without possible damage to new concrete.  It’s a constant battle against Jack Frost and Old Man Winter.  Many Deicers say that they are safe for concrete and some can be less damaging but all melt water and let water penetrate into the concrete.  The freeze and thaw cycle is where the damage to the surface can occur.  As a contractor you should tell your customer not to use salt or calcium on their new concrete for at least one year after the concrete has been placed and that Ammonium Nitrate or Ammonium Sulfate should never be used. Concrete contactors will want to take certain precautions to avoid call-backs for surface spalling.

Water is one of the only liquids that will expand when it turns to a solid.  At 39 degrees it is at its most dense state and can increase almost 10 percent in volume when it turns to ice.  As the snow and ice melts it will penetrate into the surface of the concrete, can refreeze when it gets below freezing and as it does the water expands.  This expansion is what causes the surface area to break off or spall.  Air-entrained concrete helps give the water an area in which to expand because the cured concrete has little air bubbles to act as buffers.  A core temperature of 50 degrees for seven days and avoidance of any freeze-thaw cycles of the concrete for 30 days will help to give nearly 95% of the concrete PSI strength.  Use a minimum of water in the mix (four slump or less).

A good sealer or cure/seal can be applied that will help to repel the salt laden moisture from getting carried beneath the surface of the concrete.  Make sure to use a breathable sealer that is silane or siloxane based.  Aquron 2000 is PennDOT approved and used by many townships because it has been proven to resist salts and other chemicals on concrete surfaces.  Vexcon Chemicals and B/C Admixtures also have some sealers that will help resist damage from salts.  Call Landis Block and Concrete at 215-723-5506 to ask about some of these products.

Ref:  NRCMA CIP 2 “Scaling Concrete Surfaces”.

News on December 10th, 2010