Articles

Re-Sealing Stamped Concrete
Know what your sealing over!

            Most manufacturers of acrylic sealers recommend re-sealing with the identical product that was used originally for concerns of incompatibility or weakened bond strength.  As residents of one of thirteen states in the U.S.A. with recently increased chemical restrictions, nearly all of the sealers used prior to 1/1/2005 are now outlawed and we are forced to find alternatives to use for re-sealing older projects.  Because of this legal change, we have worked hard to find a user-friendly, good-performing sealer for exterior decorative concrete, i.e. SDI Stamp Seal – Klear Gloss # 2.  We firmly believe that this is the single best NJVOC compliant formulation available.  With that, we have worked specifically on making sure that our Klear Gloss # 2 will work compatibly with our original formulation (SDI Stamp Seal – Klear Gloss), and our penetrating version (SDI Stamp Seal – Penetrating). 
            For your projects that you know have been sealed last with something other than one of our Stamp Seal formulas, please contact us or the manufacturer of the product last used (if used successfully).  It will likely be recommended that you first test a small area and allow it to weather for a while.  If the new and old sealers do not bond to each other with enough strength or if they are not bonded strongly to the concrete, that bond will be compromised under the pressure of moisture, sun, and time, resulting, sometimes, in a whitened film.  Evidence of a problem is most likely to develop within a month but will occasionally take longer to identify itself so please allow enough time to pass for your test results.   There is still no agreed reason between chemists and authorities as to why this occurs but the consensus is that it is related to film thickness and moisture vapor pressure, which is why most problems arise shortly after, or during, periods of excessive precipitation.  It is also debated whether or not there is, in fact, an identifiable compatibility issue between different acrylic sealers with different resins and different chemistry.  There has been no definitive testing that suggests there is a specific incompatibility that results in consistent failure or delamination of any one acrylic sealer when used with any particular other.  However, it is FAR more rare to see a sealer failure occur with the exclusive use of a single product applied in very thin coats.  This seems to hold true for re-sealing as well, as long as the surface is clean and very dry before the re-seal coat is applied (again, very thinly).
            We now understand that changing products too often can only increase the likelihood of problems arising if re-sealing with a new sealer.  Sealant Depot, Inc. acknowledges that we have changed suppliers frequently in the past in search of the best product for your application based on performance, ease of application, and cost as well as forced changes due to legal constraints.  We believed that we had found a superior sealer formulation with the SDI Stamp Seal – Klear Gloss late in 2004.  However, we were only able to stock a limited supply of that formula before the V.O.C.  restrictions were increased , making it, and nearly all other solvent-based acrylic sealers illegal in NJ as well as an additional 12 other states in the U.S. (most of the Northeastern states and California).  That legal change required us to search further for yet another formulation.  Using the same resin system as in our original Klear Gloss, Klear Gloss # 2 was developed and is compatible for use with its predecessor, keeping in mind proper application rates and conditions of the substrate and environment during its curing stage.  That is not to say that it is compatible with all sealers nor in all circumstances. 
            For a better grasp of how sealers may work together, it is important to know the product you are re-sealing over.  With some help from your supplier or manufacturer, and a light education in general sealer chemistry, most concerns of incompatibility can be reduced.  If you have questions about the chemistry of a product that has been used in the past and you would like to re-seal it, please contact Sealant Depot, Inc. or the product’s manufacturer.  If the original product is not readily available and/or you would like to use a different product to re-seal with, not all hope is lost.  It is best to use the most similar product available to you (use like resins, do not mix different resins i.e. styrene acrylics, methyl methacrylates, or pure acrylics) and perform a reasonable-sized test area (one that is large enough to yield true results, and also small enough that it can still be stripped if necessary).  For help in choosing the most similar product available, call your local supplier.  They should be able to help you.  If not, we at Sealant Depot, Inc. will do our best to help as well.

Renew-Crete Systems Concrete Overlays

Some large projects will require more than one pour to complete. Whether you are doing an overlay or stamped concrete, matching in to the previous days work is very important. Having a project look uniform from start to finish, will lessen headaches, make happier customers and sell more work. Here at Renew-Crete Systems™ we have come up with some suggestions to help multiple pours go a little easier.

Before you start applying your material, plan where you intend to stop. A good recommendation is to divide your job into areas about 300-500 sq ft. If possible utilize the existing natural breaks such as control/expansion joints. If the area has no control/expansion joints, you will need to create your own stopping point.

Stopping along expansion joints
Select the control/expansion joint, use duct tape and 36" masking paper to tape off the open side of the control/expansion joint. When you apply the material, gauge rake the stampable overlay mix over the edge of the tape and paper by 2"-3". (Photo 1) Be sure not to thin the material along that edge. Stamp the area when ready and continue the pattern over your stopping point (lay the mats right over the tape and paper). After removing the mats, find the control/expansion joint, cut along it with a trowel and remove the tape. This should be done directly after removing the stamp tool while the material is still soft. This method will make a nice clean material break. This method also works well on deco drains, along pool copings and tiles. If this will be a finished edge, when dry, use a rub stone and lightly bevel the edge to avoid chipping of the edge.

Making stopping points
Sometimes there are no expansion joints at which to stop. In this case, you will make a stop and start point using the edge of the mats as a guide. Select an appropriate stopping point, apply your stampable overlay material about one foot past where you want to stop. When the area is ready, start stamping. Continue stamping up to about one foot before the end of your material. Leaving the last row of mats in place, use a square trowel and cut along the edge of the mat scraping the unstamped material away from the edge of the mat while it is still soft. Remove the stamps and allow to dry 4-6 hours before applying the next section.

Matching back in
Whether you have stopped along an expansion joint, or made your own stopping point, starting a new section is very easy. Using tape and paper, mask off the dry, previously stamped material to protect it from any spillage. Now apply your bond coat with a paint brush along the edge leaving about a 1/4" gap between the bond coat and the previously stamped area. This will prevent any excess bond coat from squeezing up to the surface or onto the previously stamped area. (Photo 2)

Be sure to bring the level of your overlay mix even with the previously existing stamped area. When the material is ready to stamp, remove the tape and paper revealing the previously stamped area. Carefully study the previously stamped pattern. Replace the mats over the area matching the pattern underneath (be sure to pay attention to the different stamps, red, yellow and blue). (Photo 3) Now start laying the mats locking into the old pour and continuing into the new material. If you stopped along an expansion joint, when the material is dry, re-cut the expansion joint and be sure to cut at least one inch deep and as wide as it was originally. Detail your joint work with a grinder to remove any visible seams.