Lime Shortage

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Author Message Brett M. Wilbur CSI, CDT, AIA Senior Member Username: brett Post Number: 52 Registered: 12-2004 Posted on Tuesday, July 19, 2005 - 10:37 am:    Anyone else in the south central region (Texas) experiencing a lime shortage? I’ve received several letters recently from masonry contractors requesting to substitute masonry cement in lieu of specified portland cement and lime? The only 4specs thread I could find which addressed the pros and cons of masonry cement and mortar cement was from August of 2004. It did not address the lime shortage and did not offer other possible options. Only a few responded at that time, but it looks like the consensus was against masonry cement. If so, what other options are there? If not, then what limitations with the masonry cement should I be aware of for this region and climate? Susan McClendon Senior Member Username: susan_mcclendon Post Number: 16 Registered: 01-2005 Posted on Tuesday, July 19, 2005 - 01:46 pm:    Contact the National Lime Assoc, www.lime.org. Masonry cement has long been offered as a substitute for portland-cement lime mortar. It's "easier" for the contractor but not necessarily a better product in all situations. If you can't find any substantiation for a lime shortage, this would be what I would suspect. Try BIA Tech Note 8. Brett M. Wilbur CSI, CDT, AIA Senior Member Username: brett Post Number: 53 Registered: 12-2004 Posted on Tuesday, July 19, 2005 - 02:47 pm:    Thank you Susan. I contacted the National Lime Association, and they got me in touch with the plant that supplies lime to this area. Yes, they did have a shortage. However, it was not a shortage in material, it was a shortage due to manufacturing changes and upgrades. They apparently have changed out their pumps and had to recalculate their lime/water mixes. It took about 6-8 weeks. They are in production again, and are trying to fulfill back orders. They should be in full operation shortly. Still, I'd be interested in getting more information about masonry cement. My masonry supplier tells me masonry cement is an excellent product and easier to use, and as long as compressive strength is equal to the specified portland/lime mix, it is an acceptable substitution. I need a better explanation than that. I'll keep digging. Thanks again. William C. Pegues, FCSI, CCS Senior Member Username: wpegues Post Number: 421 Registered: 10-2002 Posted on Tuesday, July 19, 2005 - 02:57 pm:    Brett, You should check out the BIA web site then for their technical notes on mortar. There was also several years of research that ended just a couple years ago about how to pair your brick with the right mortar looking at from different characteristics of brick. Those years, the BIA seminars at the CSI Show were really good. You might contact them, ask for that information specifically. All 3 generic types were cross referenced with different qualities of the brick - masonry cement, masonry mortar (never sure if I get that term correct) and portland cement mortar. There are times when you would use a different grade of each product with the same brick due to the different qualities. That's why you can't just let someone substitute the same grade of the different products. Email Greg Borchelt at BIA borchelt@bia.org He will send you or point you to the correct source material. I have known him for years and he is in our local chapter (BIA is just down the highway a bit from our regular meeting location). Feel free to mention that I recommended you contact him. William Susan McClendon Senior Member Username: susan_mcclendon Post Number: 17 Registered: 01-2005 Posted on Tuesday, July 19, 2005 - 03:01 pm:    Many years ago, my firm's specifiers (I was just a novice then, so took their word for it) believed that portland-lime mortar was more waterproof than masonry cement mortar. This was in the era when brick veneer over metal studs first showed up with severe corrosion problems, so it was a big deal. Another factor is how well the mortar sticks to the brick -- bond strength, which was also considered better for portland-lime. ASTM C270, for masonry mortar, has a huge non-mandatory appendix on mortar properties. It says bond is not only the most important single property of mortar but the most inconsistent and unpredictable. My mentors believed that it was easier to get consistency with portland-lime because masonry cement is allowed to have "mystery" materials -- all masonry cements are proprietary mixtures. Basically, if you have a lot of brick (especially high-rise), you should learn about this -- if not, masonry cement will probably be ok. After all, whenever portland-lime is not specifically specified, contractors use masonry cement, so there are a lot of buildings out there using that. John McGrann Senior Member Username: jmcgrann Post Number: 53 Registered: 03-2002 Posted on Wednesday, July 20, 2005 - 08:34 am:    Several years ago our chapter’s technical committee had some fun with the masorny students at a local vocational school. The test program wasn’t scientific, but I’ll bet the results would be repeatable just about anywhere. Simply construct three sample panels, one using PCL mortar and “by the book” techniques (wetting the brick, good flashing details, keeping the cavity clear), one using masonry cement and what amounts to the local "commercial standard" techniques (not wetting the brick and high-production rate construction), and one using masonry cement and poor construction techniques, like partially filled head joints and no weeps as we often find in residental construction, and sometimes on larger projects when the mason doesn’t think anyone is looking. Allow the panels to cure for a couple of weeks, then invite the fire department to apply some “wind-driven rain” with a fire hose equipped with a combination fog nozzle. Your results may vary, but one panel will likely perform substantially better than the others. Susan McClendon Senior Member Username: susan_mcclendon Post Number: 19 Registered: 01-2005 Posted on Wednesday, July 20, 2005 - 09:05 am:    Great idea, John. But it's unlikely the contractor wanting to substitute masonry cement will admit he's intending to use less than specified construction techniques. Did you ever test PCL vs masonry cement both using the best techniques? John McGrann Senior Member Username: jmcgrann Post Number: 54 Registered: 03-2002 Posted on Wednesday, July 20, 2005 - 12:59 pm:    Susan: The committee at that time was more focused on workmanship issues (and to help the students understand those issues) as opposed to material issues. I would have liked to see a more direct comparison, but “best techniques” for PCL don’t necessarily translate to masonry cement. For example, some masonry cements have enough water retention agents in them to retain sufficient water for hydration and stability without the need to wet some types of brick with low to moderate rates of initial absorption. David Axt, AIA, CCS, CSI Senior Member Username: david_axt Post Number: 480 Registered: 03-2002 Posted on Wednesday, July 20, 2005 - 01:02 pm:    What?! Lime shortage! Now what the heck am I supposed to put in my Corona beer?! Maybe this: http://www.gibco-usa.com/ Robin Dale Rund Member Username: rdrund Post Number: 3 Registered: 06-2005 Posted on Wednesday, July 20, 2005 - 01:08 pm:    As William noted, there are three types of mortars available: portland cement-lime (PCL) mortar, masonry cement mortar and mortar cement mortar. The following is from BIA Tech Note 8Rev (2003): "Mortar cements are hydraulic cements, consisting of a mixture of portland cement, plasticizing materials such as limestone or hydrated or hydraulic lime, and other materials intended to enhance one or more of the properties of mortar. In this respect, mortar cement is similar to masonry cement. However ASTM C 1329, Specification for Mortar Cement, includes requirements for maximum air content and minimum flexural bond strength that are not found in the masonry cement specification. Because of the strict controls on air content and the minimum strength requirement, mortar cement and portland cement mortars are treated similarly in the Masonry Standards Joint Committee (MSJC) Code and Specification." The key here is the difference between masonry cement and mortar cement. Masonry cement appeared in the 1920's and 1930's. The intervening decades have been filled with acrimony between the masonry cement makers and lime producers. The proprietary nature of masonry cement led to charges that it was full of mysterious stuff. In the mid-seventies, Clayford Grimm, among others, did some testing that revealed very high air content (over 18 percent) for some manufacturer's products. Investigation also revealed masonry cements typically achieved lower bond strengths than PCL mortar. Masonry cement producers continued to claim equality with PCL mortars. Finally, after UBC rebuffed their efforts to have masonry mortars approved for use in seismic-reinforced masonry, the manufacturers decided they would have to do something to address the issues of air content and bond strength. Their response was to develop mortar cement (as opposed to masonry cement). The chief difference is that mortar cements are limited to 8-to-12 percent air content (vs. 3-to-5 percent for PCL) and flexural bond strength equivalent to PCL. These changes were codified in 1996 (I think) in the ASTM C 1329 standard referenced above. Today, UBC and IBC recognize (and require) either PCL mortar or mortar cement mortar for seismic reinforced structures. William also mentioned the recent testing of bond strength. I admit I've stopped paying close attention to this issue in the past few years, but as of 2000, the initial results done on face brick indicated that brick with a low IRA (initial rate of absorption, or "suction") actually had better bond with mortar cement mortar than PCL mortar. On the other hand, PCL provided superior bond with high suction brick. This is probably because a workable PCL mortar contains more water than a workable mortar cement mortar (at least of those tested at that time). But, while it's true that good bond is critical to the performance of a wall, it’s entirely possible to put too much faith into simply achieving the strongest bond possible. For example, the solution to water penetration issues related to masonry veneer on steel stud framing construction was not to increase the bond strength of the mortar but to reduce the deflection of the steel studs. Likewise, it would be better to carefully select brick with good IRA values rather than obsessing about whether mortar cement (or even masonry cement) has better bond than PCL mortars. The key is not only to avoid specifying brick with an exceptionally high or low IRA, but also to avoid blends that combine very high suction brick with very low suction brick. Such blends ensure that the mason can't take any measures (i.e. wetting brick, slightly increasing or decreasing water content of the mortar, etc.) to achieve good bond, since what helps bond for one brick hurts it for the next. So, to address Brett's concerns (finally!) First, there is no inherent reason to fear mortar cement (or masonry cement either). If your structure is seismic-reinforced, mortar cement is mandatory. Otherwise, I can tell you that in the Metro Detroit area, masonry cement has held the vast majority of the market for decades (even before the advent of mortar cement) without any obvious problem emerging. That said, if your mason hasn't had much experience with whatever type of mortar you finally accept, your project will be on the wrong side of his or her learning curve. Ask about the extent of their experience. At best, they should have experience using the same mortar used for your project, with masonry units having suction rates comparable to those on your project, and under similar weather conditions. You can boost your confidence by requiring more extensive mock-ups than you would otherwise, reviewing the results in person, and discussing special methods he plans to use (mortar water content adjustments, etc.). If you are using brick, the other thing you can do (at least in the future) to decrease your risk (regardless of mortar type used) is to use make sure the IRA is not too high or low and to avoid blends where the individual brick are vastly different. Susan McClendon Senior Member Username: susan_mcclendon Post Number: 20 Registered: 01-2005 Posted on Wednesday, July 20, 2005 - 03:06 pm:    Thanks so much for the updata! Helaine K. Robinson CCS Senior Member Username: hollyrob Post Number: 179 Registered: 07-2003 Posted on Thursday, July 21, 2005 - 12:10 pm:    90% of the time the brick is selected to match existing or else by someone primarily concerned with appearance, not suction rate. "The key is not only to avoid specifying brick with an exceptionally high or low IRA, but also to avoid blends that combine very high suction brick with very low suction brick. Such blends ensure that the mason can't take any measures (i.e. wetting brick, slightly increasing or decreasing water content of the mortar, etc.) to achieve good bond, since what helps bond for one brick hurts it for the next." Robin Dale Rund Intermediate Member Username: rdrund Post Number: 4 Registered: 06-2005 Posted on Thursday, July 21, 2005 - 03:32 pm:    Helaine, Yup, that's my experience too, sad to say. We need to do more educating on the subject. William C. Pegues, FCSI, CCS Senior Member Username: wpegues Post Number: 425 Registered: 10-2002 Posted on Thursday, July 21, 2005 - 07:11 pm:    It is just fine to select brick to match existing or for aesthetic purposes. The point of the BIA research and revisions it produced was not to create a list of cautions about not using high or low IRA bricks, but to provide guidance to what kinds and types of mortar should be used with what kinds and types of bricks. All else on this thread of discussion is pretty much just missing the point. Call them, find out for yourselves. I suffer a privileged life in that BIA is local to my area - heck, its closer to my house than my office, they host our special board meeting events by providing space for us, and I count both personal and professional friends among their technical group. Our chapter was fortunate in that they made their presentations to our chapter before they offered Institute programs at the CSI shows several years ago. Just call them, find out for yourselves what the intent of their various advice is if you don't actually have their current publications in hand.