Split Face Masonry Sealer

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Author Message Jeff Williams RA Senior Member Username: architectjw Post Number: 15 Registered: 10-2013 Posted on Thursday, March 26, 2015 - 12:28 pm:    I am working on an older school that has split face masonry block. The owner wants to seal the block to reduce moisture getting into the block. I have looked at Silanes, Siloxanes, Vulcanizing Silicone Rubber and Solvent-Based Silicone Elastomer. It appears that Silanes, Siloxanes are out due to the porosity of the block. Vulcanizing Silicone Rubber is a good product but picks pick up dirt and can ghost over time. Solvent-Based Silicone Elastomer appears to be the best. Does anyone have any comments or disagree with my findings? Liz O'Sullivan Senior Member Username: liz_osullivan Post Number: 176 Registered: 10-2011 Posted on Thursday, March 26, 2015 - 12:44 pm:    Does the owner want it to look like it's painted? Or would they rather that it just have the split face surface? If they'd rather keep it natural, you might want to talk to a rep at Evonik or BASF about options. I think it'll look painted with a silicone elastomer. J. Peter Jordan Senior Member Username: jpjordan Post Number: 808 Registered: 05-2004 Posted on Thursday, March 26, 2015 - 12:47 pm:    Ah; split-faced block-- the cementitious sponge. The best thing you can do for the moisture absorption is to put a good elastomeric coating over it. This will change the appearance, but so will the silicones you are investigating. The "sealers" are really water repellants which do have their place, but if you know you have moisture problems, using an elastomeric coating is probably going to be the best solution. Jeff Williams RA Senior Member Username: architectjw Post Number: 16 Registered: 10-2013 Posted on Thursday, March 26, 2015 - 12:52 pm:    The product I was looking at was a Prosoco Sure Klean that is clear. They didn't say it would change the appearance of the building. I will check on that. Thanks. Robert E. Woodburn, AIA, CSI, CCS, CCCA Senior Member Username: bob_woodburn Post Number: 157 Registered: 11-2010 Posted on Thursday, March 26, 2015 - 12:56 pm:    You might take a look at (IIRC) "Professional Water Sealant" by Professional Products Co. in Kansas. It's a silicone rubber dissolved in mineral spirits that soaks in and disappears (unless it's put on too thick). Ronald L. Geren, FCSI, AIA, CCS, CCCA, SCIP Senior Member Username: specman Post Number: 1291 Registered: 03-2003 Posted on Thursday, March 26, 2015 - 05:51 pm:    I'm curious as to why you discounted the idea of using a silane or siloxane. These are penetrating water repellents and do very well with concrete and concrete masonry. They do not change the color and they do not need reapplication over time that is common with many surface coatings. Ron Geren, FCSI, AIA, CCS, CCCA, SCIP www.specsandcodes.com Jeff Williams RA Senior Member Username: architectjw Post Number: 17 Registered: 10-2013 Posted on Thursday, March 26, 2015 - 06:27 pm:    Ron, what I have found is that silane and siloxane are great for brick and normal weight smooth face block. The pores are very small and those sealers can close the gaps. From speaking to several reps and reading an article on the subject, the pores on split face block are very large. Silane and siloxane cannot fill the gaps. Their molecular structure is too small. Vulcanizing Silicone Rubber and Solvent-Based Silicone Elastomer have a larger molecular structure allowing it to fill the pores in the masonry. That was the basis of my statement. I am open to other opinions though. Ronald L. Geren, FCSI, AIA, CCS, CCCA, SCIP Senior Member Username: specman Post Number: 1292 Registered: 03-2003 Posted on Thursday, March 26, 2015 - 07:34 pm:    The intent of silanes and siloxanes is not to "fill the gaps." They are hydrophobic chemicals that bond with the concrete material deep inside the material to develop a barrier that remains breathable (i.e. still has openings), but creates openings so small that they do not allow water molecules to pass. Silanes, being the smallest of the two molecules, will penetrate deeper. Split-face CMU is just like any other CMU inside, depending on the weight (i.e. lightweight, medium weight, and normal weight). The only difference between split-face and other CMU is that the tighter surface made by the molding process is not present in the split-face portions of split-face CMU. But silanes and siloxanes do not need that tight surface, they will penetrate deep into the CMU material (about 3/8"), which is just like the exposed split-face material, to create the barrier. The only way the repellent can be removed is by physically removing the concrete material containing the repellent. Silane is best for normal weight CMU, but siloxane, with its larger molecule, may be better for medium weight CMU. I'm not sure if either of these would work well with lightweight CMU. Ron Geren, FCSI, AIA, CCS, CCCA, SCIP www.specsandcodes.com John Regener, AIA, CCS, CCCA, CSI, SCIP Senior Member Username: john_regener Post Number: 740 Registered: 04-2002 Posted on Friday, March 27, 2015 - 12:58 am:    Is anti-graffiti a consideration? ken hercenberg Senior Member Username: khercenberg Post Number: 887 Registered: 12-2006 Posted on Friday, March 27, 2015 - 12:28 pm:    Jeff, I normally don't like silanes and siloxanes because I've found that they do require reapplication after about 10 to 12 years and most Owners and Facility Managers don't arrange for long-term maintenance items such as that. Having said that, I've used Evonik products successfully on split-face CMU. With the changes that have been going on over the years with VOC content and formulations I would suggest calling your Evonik and BASF reps as Liz noted and find out their best guess for solving your problem. Once identified, get samples of all you options and a RILEM tube and test every one on your building. It's the only way I've found that works in selecting a solution for this type of situation. If you've got lightweight split-face CMU, you probably are going to have to consider an elastomeric coating and yes, that will change the appearance. My preference would be Nawkaw Lithium (http://www.nawkaw.com/lithium.html) stain or Sinak HLQ 125 Clear. More expensive but I believe you have a higher probability of getting a good end result that will last a very long time. A couple of other factors to consider: 1. You are about to change the equilibrium (good, bad, or otherwise) of the building. Advise your client that despite all of your research and best intentions, there may be unforeseen repercussions to this action. 2. Try to get a certification from the manufacturer stating that application of this product will not result in spalling of the CMU due to trapped moisture, freeze-thaw, or other causes. Presuming that the CMU does not now exhibit signs of such damage, tell the manufacturer that you're not using their product until they acknowledge in writing that they are aware of how and why their product is being used and that it is fit for use in this application. 3. Find an area of the building where you can conduct mockups of the proposed solution and make sure it doesn't result in an adverse appearance. Jeff Williams RA Senior Member Username: architectjw Post Number: 18 Registered: 10-2013 Posted on Friday, March 27, 2015 - 02:23 pm:    Ken, thanks! We do not specify exterior masonry sealers often so I appreciate your insight. I hadn’t considered spalling. That could be a real problem. I will definitely take your advice into consideration. John, graffiti has not been an issue so it has not been mentioned by the school. I will ask those questions prior to bidding. Ron, thanks for the info. Phil Kabza Senior Member Username: phil_kabza Post Number: 554 Registered: 12-2002 Posted on Monday, March 30, 2015 - 04:07 pm:    Jeff: You may want to investigate the potential impact of silicone-based compounds on the adhesion of any future coating application. Silicone's great strength is also sometimes a disadvantage when it comes to trying to bond something to a surface that had received a silicone treatment.