This is can be a frustrating problem in our Industry that has shown up in the past 5-6 years. There are many reasons why this happens that we are aware of and others that we are addressing. The American Society of Concrete Contractors in St. Louis that we are a Member of is taking the lead in identifying all the causes and possible solutions pertaining to Whitening of Sealer or as it is also known Blushing.
ASCC is having a symposium that Contractors and Suppliers are going to attend on Dec 1-2 to discuss what we are going to do to correct this condition. We will keep you informed on the outcome.
This condition in most causes is associated with applying sealers to soon after pressure washing. Sealing the same day can almost guarantee that you will have problems. As you would never paint a wet wall with paint the same precaution needs to be adhered to regarding sealing Decorative Concrete.
Unfortunately there are those Concrete Contractors who will tell you that you need to reseal every year. This is an utterly false statement that has been used by those who are either not well schooled in this aspect of our business or they are trying to make money by instilling false fears on you the customer.
Good quality sealers do last longer than 1 year if they are Resin –Solvent based sealers. Unfortunately in some States there are VOC regulations that prohibit the use of the Sealers that we had great success with for over 20 years. It is my understanding from talking to my supplier at The Sealant Depot in Cinnaminson New Jersey that the EPA reached out to producers and asked how the changing the formulation of sealers to make them VOC compliant would affect the this industry.
I don’t know how many producers were asked but apparently not enough to have changed the minds of the EPA regarding changing the formulation.
It seems that the main ingredient being the solvent was replaced in part with a Tertiary Butyl Acetate to a degree that makes the sealer compliant. We will be addressing this I am sure at the Symposium to see if there is any validity to the claim that this has caused some of the problem.
Problems caused by:
Sealing the same day
Not cleaning thoroughly prior to sealing. Bad adhesion of sealer.
Applying to many thick coats of sealer.
Trapped moisture shows up a white condition since water is trapped between the surface of the concrete and the bottom of the sealer. Sunlight causes evaporation and the moisture is trapped. Sealer actually needs to breath. Allowing ground water and surface water to freely evaporate. Too many coats and incompatible sealers will cause problems.
Sealing to frequently 3-4 years is an approximately the time a good sealer should last. Multi coats will trap water and cause blushing.
The above problems don’t show up immediately in some cases but will occur if those applying sealers incorrectly or using incompatible sealers insist on improper installation.
Stripping- Messy and Costly and might not remove all the bad sealer. You reapply and the same problem occurs.
Sandblasting – The most cost effective solution to correcting this. CAUTION: This needs to be done by a sandblasting Professional that has a great eye and believe this or not some degree of passion about what they do. This can be used using Coal Slag as a blasting medium. Coal Slag is the preferred blasting agent due to it being more environmentally friendly due in part to it being biodegradable. Silica Sand that is typically used is harder and can cause health issues. The application of Sealer needs to be done in very thin coats too not create the same problem.
Shot Blasting and Overlay- Extremely costly and I feel and unnecessary approach due to the advent of Sandblasting as an option.
Remove and Replace- We don’t even want to go there.
Surface Aid by The Sealant Depot. Only good for trapped moisture on a new application. It can sometimes work on older applications or reseals but generally takes to many applications to make the blushing go away for good. We find that spray followed by scrubbing works best. It emulsifies the sealer and allows the water to evaporate that was trapped.
This is only a brief description of Causes and Solutions that I am sure will be elaborated on and discussed to see if both are plausible or not at the ASCC meeting this December 1-2
I can always be reached at Ted@split-rok.com or by calling our office at 732-915-6391. We are always trying to better this industry that we are passionate about by helping those who need our help. Helping each other benefits all.
The Concrete Professor