Which Lime Is Best?

 

By: Herb Nordmeyer, author of The Stucco Book—The Basics

 

We have all heard that mixing lime with Portland cement makes an excellent mortar or stucco, but which lime is best? In answering that question, we have identified the different products that are sold as lime and explained why they are appropriate or not appropriate.

 

 

Agricultural lime is calcium carbonate. That is ground limestone and for our purposes is of no value.

 

 

 

Quick lime is limestone that has been heated to about 1,650⁰ F to drive off the carbon dioxide. It is calcium oxide. When it comes into contact with water, it reacts to form calcium hydroxide. In the process, heat is given off, often enough to boil the water; and if the chucks of quick lime are fist-sized, they may explode. Quick lime can be used to make lime putty, but should never be considered as a component to be added to a mortar mixer.

 

 

Lime putty is quick lime that has been hydrated and has a toothpaste consistency. It can be made directly from quick lime, or it can be made by adding water to hydrated lime. It has a place in historic restoration and a few other places, but it is not worth the effort for most mortar and stucco work.

 

 

High-cal lime is a hydrated lime that is produced for water purification, wastewater treatment, and many other industrial processes. There are people, including some who should know better, who use it for making mortars and stuccos, but the quality testing is such that sometimes it has oversized (problems can be caused by particles that are less than 1/8″ in diameter) particles that can lead to lime-pops months after a job is complete. The oversized particles are calcium oxide particles, and it takes them a while to hydrate. When they do, the resulting calcium hydroxide takes up more space, so a bit of the mortar is broken off. Usually this results in a conical hole in the plaster or mortar with a white dot in the center. An additional problem with high-cal lime is that it is more prone to causing lime burns than Type S dolomitic hydrated lime.

Type N hydrated lime is very similar to the high-cal lime, but there are more quality checks, and the oversized particles that cause lime-pops are not present. With Type N hydrated lime, over 8% of the lime can be unhydrated. The unhydrated portion may be fine particles that fairly easily hydrate, or it can be hard-burned particles that are very difficult to hydrate. Hard-burned particles usually have a glassy layer around them that takes a long time for the water to penetrate and bring about the hydration process. Since there is unhydrated calcium oxide in the Type N hydrated lime, it can cause lime burns on skin.

 

Type S hydrated lime has less than 8% unhydrated particles. Much of the Type S is produced from dolomitic limestone (calcium-magnesium carbonate). Since magnesium oxide is harder to hydrate than calcium oxide, the hydration usually is done in a pressure hydrator. As a result, virtually all of the calcium oxide is hydrated, and the magnesium oxide which is not hydrated is less likely to cause skin burns than calcium oxide. Type S hydrated lime particles are usually larger than the Type N hydrated lime particles and give the resulting mortar or stucco more body and more workability. Where it is available, the Type S dolomitic hydrated lime is well worth the extra money it costs.

 

Resource Box

Herb Nordmeyer, author of The Stucco Book—The Basics

http://nordybooks.com/stucco/

By Ted Uram

 [youtube]https://www.youtube.com/watch?v=Emt1udTLGGo[/youtube]

Power to the People

When last we left Andrew Bui, an engineer with Engineers Without Borders, he was in Guatemala trying to build a ferrocement water tank for the people of San Lorenzo. But they had run into some problems…

Continue reading Ferrocement Water Tank, Part 2

Ferrocement Water Tank: Part One

By Ted Uram

Ferrocement Water Tank Definition: a water containment structure built from a mixture of Portland cement and sand reinforced with layers of woven or expanded steel mesh, and closely spaced small-diameter steel rods (rebar) – source: Wikipedia.org Continue reading Ferrocement Water Tank

by Ted Uram

David Kottman of Roanoke, Mo. is no fool. Like many savvy shoppers, he clocks a lot of research hours before making any purchase. It’s the smart thing to do. So when looking for a solution to resurface the block wall foundation of an old homestead building on property he had purchased, he spent lots of time on the Internet, several hours of which were on MortarSprayer.com.

“I searched numerous websites to try and see what to do with this foundation,” David explains. “We wanted the solution for the foundation to be something we could do as a do-it-yourself project.”

An inexpensive solution was also important. The property on which the old house rests is something of an investment in the future. One day soon, David hopes the building will be surrounded by a thriving winery.

“Approximately eight acres came up for purchase at an estate sale,” David explains. “We purchased the property with the intention of creating a winery.”

In addition to the building with the ailing foundation, a 3,700-square-foot, 1890s era, three-room schoolhouse also rests on the property.

“We hope to renovate that structure, as well, to serve as the main building for the winery,” David says.

First things first. The first hurdle was the small out-building.

“This little building sits on the corner of the property,” David explains. “At one point, we thought we were going to fix it up and flip it, but then we decided not to do that.”

Since the building did once serve as a residence, David considered making it habitable to rent. But that plan was scrapped as well. It was decided the building would be incorporated into the winery, and while there are still no concrete plans for exactly what purpose it will serve, the building most definitely needs work. Regardless of its new role as a winery structure, the foundation of the building was in desperate need of a makeover, and other issues arose.

“The whole project involves a new roof, insulation, and new siding, as well as fixing up the foundation,” David explains. “This block foundation is under the oldest part of the house, under about two thirds of it.”

Like many of the old Missouri buildings built around the turn of the Century, the small structure is supported by a block foundation. Mortar used to set and finish blocks in the old days was not nearly as efficient as it today, and several patches of block on this home had to be reset and mortared before any resurfacing could be performed.

Using jacks, the house was lifted. Failed block was replaced, and all of the loose blocks re-mortared. David was ready to tackle the foundation.

Even after straightening and re-mortaring there was some surface unevenness, so David opted for a surface bond mix enriched with glass fibers, which he laid on pretty thick using a sprayer from MortarSprayer.com. With the help of a mixer mounted on the three-point hitch of a small tractor, he was easily able to complete mixing and be underway.

             

“We combined that mixture with a stone-veneer mix (Quikrete) that has high-adhesive qualities. We covered it with a pretty quick coating.”

Once that coat had set up, David came back over with another layer of stone-veneer mix combined with Quikrete sand topping mix. This succeeded in hiding any of the remaining glass fibers still sticking out.

The amazing part about all of this is that David did not have an adequately sized compressor to push the flow. What he did have was two smaller compressors for powering air tools. His solution was to tie the two compressors together.

       

“They had small tanks with fairly low CFM pumps,” David says. “We knew that we had to increase the rate of compression.” Having enough compressed air was also an issue. Tying the two pumps together using a couple of ten-gallon air pigs did the trick.

“The guy that was helping me with the project is a roofer by trade. He already had his compressor set up for the roofing nails, so we tied his compressor in with mine.”

The two compressors were run through one manifold which fed the sprayer.

img class=”aligncenter size-medium wp-image-2829″ alt=”Mortarsprayer Compressor” src=”https://www.mortarsprayer.com/wp-content/uploads/2012/01/Mortarsprayer-Compressor-300×225.jpg” width=”300″ height=”225″ />

“It worked great.”

Since David had never sprayed plaster before, there was a learning curve involved. But it didn’t take him long to catch on.

“It took some time, but we eventually had a good feel for how to keep the tool moving, when to pull the trigger, etc.”

His mix kept leaning toward the dry side, so it also took a little playing to get the right consistency. “When we had fingers of mix coming out of the holes that didn’t drip on the ground, that was what worked best.” From start to finish, the entire job only took about two hours.

 

All in all, David was pleasantly surprised with the results. “I thought it was going to be a dull, concrete gray, but it dried up a little whiter than I expected and looks real nice.”

David says he doesn’t know how he would have completed the job without the sprayer, and he was quick to justify his purchase.

“There’s going to be some foundation work on the schoolhouse, too,” David adds. “This will work well for matching the original foundation.”

David says that since he’s completed this project, he has all kinds of additional potential projects floating around in his mind, such as stucco siding on some buildings, and even a compost containment bin.

“I don’t know which of these projects will happen, but it’s certainly opened our eyes to a whole wide range of potential projects. It’s just a new method of construction that we hadn’t considered possible before.”

In the meantime, the foundation of the house is complete. And while the grapes mature, David has his eye set on the schoolhouse.

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