St. Astier Natural Hydraulic Lime for Historic Restoration, Conservation and New Build Projects

Prior to the 1940’s many brick and stone buildings were constructed with lime and sand for mortar. Many times these limes were inadvertently hydraulic limes. The lime putty used may have had a hydraulic set because of impurities in the limestone when a limestone contained various degrees of reactive silica and was burned along with the pure calcium carbonate stone. Today, it is unfortunate that many of these pre-1940 buildings have been repaired using Portland cement based mortars and stucco. There are some consequences with this remedy. All buildings move and cracks develop in rigid Portland cement mortars and stucco. When a Portland cement mortar is stronger than the brick or stone laid up in the mortar, cracks that develop will transfer to the face of the exterior masonry allowing water penetration. Water can then be driven deeper into the masonry as it migrates to inside spaces.Portland-needle-lime-hexagonal

A contribution of the National Institute of Standards and Technology.

Portland cement has a dense pore structure and a needle-like crystal structure that has the same expansion and contraction coefficient as steel, the unyielding joints and stucco will eventually crack in various places. This is especially true with free standing church bell towers and the like. Water that does not migrate to the inside of the building may evaporate out of the more porous soft brick or sandstone and only accelerate its decay. The mortar on the other hand will remain proud as the masonry units will decay back and finally hollow out from their original face plane.

Tricalcium aluminates and Tricalcium silicates which form during the burning process of Portland cement have a detrimental chemical reaction when they come in contact with water that gets trapped in the bedding mortar and salts which are found in old buildings. This reaction results in what is called “The Sulphation of Cement”. It is known to bulge once sound masonry walls as expansion occurs with this reaction sometimes causing even massive stone walls to topple over. Lime, however, has an open pore structure and a hexagonal crystal structure which allows the plates to shift between one another and yields flexibility and high vapor and liquid permeability. Some advantages of lime mortars are:

  • Walls breath better and moisture can escape
  • Mortar and stucco does not set too hard
  • Thermal movement can be accommodated without damage
  • Expansion joints can be avoided
  • Insulation is improved and cold bridging reduced
  • There is a reduced risk of condensation
  • There is little risk of salt staining because salts get flushed from wall surfaces
  • Masonry life is increased
  • CO2 emissions in the manufacture of lime are 20% less than cement and during carbonation of the lime, the mortar and stucco reabsorb considerable quantities of CO2
  • Natural Hydraulic lime gives an excellent reproduction of sand color

All St. Astier NHL mortars can be reworked (8-24 hours), reducing waste of material and increasing work rate due to its hydraulic set. St. Astier NHL contains no cement, gypsum, pozzolans, tetra calcium Aluminoferrites, (high in Portland cement and contribute to expansion when reacting with gypsum.) St. Astier NHL does not have high aluminates, Sulphates, Alkalis making it suitable for marine environments.

For additional information or to purchase Natural Hydraulic Lime  click here

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Another Successful Straw Bale Building with Natural Hydraulic Lime Plaster – Little Rock Arkansas

Straw bale construction is the best of both worlds, it is a green and sustainable way of building and can be affordable with low maintenance and amazing insulation that will help keep energy prices low.

Natural Hydraulic Lime is crucial for success when building with straw bales. Two factors that make Natural Hydraulic Lime so great include its breathability and its ability to self heal and repair cracks through “autogeneous healing.”

Recently a team of volunteers spent 7 days working with Andrew Morrison of strawbale.com to construct a 10,000 sq. ft. straw bale eco center.

Presented by LimeWorks.us
Phone: 215-536-6706

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Limelight on the Restoration of the Rotunda at the University of Virginia

The University of Virginia is the only US university with a World Heritage designation, it’s conservation is of the utmost importance and is currently undergoing the largest restoration campaign in decades. Matt Wolf and his team from Centennial Preservation are currently working on the repointing and window repairs for the Rotunda at Thomas Jefferson’s Academical Village.

Mortar studies showed the original mortar was made with hydraulic lime which led to the specification of a customized LimeWorks.us Ecologic™ Mortar for the repointing campaign. Ecologic™ Mortar is an environmentally friendly, breathable, Natural Hydraulic Lime based mortar available in 8 stock and countless custom colors.

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Repointing the First Congregational Church Hudson, OH – A Restoration Success

Here’s a brief summary of the project at the First Congregational Church of Hudson (OH) project by John Burnell, Principal, Mason’s Mark LLC.

The church was originally built in 1865 in historic Hudson, Ohio. It was repointed several decades ago with a cement-based mortar and started to develop brick deterioration problems in both interior and exterior upwards of 10 years ago. We performed an extensive survey of the building in 2003 and were contracted to undertake removal of the cement beginning in 2010. We completed Phase 2 last spring and are scheduled to complete the tower this summer. We used NHL 2 which we custom-tinted to match the original mortar color, and for sections that needed some brick repair, we used custom-tinted Lithomex repair mortar and some of the custom tints of Silicate stain, both to match the color and patina of the original bricks.

Products Used: Natural Hydraulic Lime 2, Lithomex, Silazur

Work Done: Repointed mortar joints, damaged brick repair, brick staining

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Preserving America’s Historic Barns – A Conversation With Historian Jeff Marshall

Screenshot 2015-08-04 09.58.49 (2)Watch our Limelight on America’s historic barns. Historian Jeff Marshall discusses his appreciation and understanding of barns, barn builders and their lasting legacy.

BARN AGAIN!!  Preserving and Repurposing the Past

Presented by LimeWorks.us
Phone: 215-536-6706

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Historic Lime Stucco and Plaster Repair in New Jersey

The Technical Install Team of LimeWorks.us was called in to reverse some of the inappropriate finish that had occurred over the years at this Historic New Jersey home. When the team arrived they found this 19th century brick home covered in layers of peeling latex paint and years of well meaning repair attempts using harmful Portland Cement based mortars and stucco.

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Besides the peeling paint and gaping holes, water was trapped within the masonry walls which made it incredibly inefficient to heat which can often will lead to build up of mold growth within the building.

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The LimeWorks.us Technical Install Team removed the layer of latex paint and localized areas of the Portland cement based materials which were contributing to an adjacent wall system failure. They repointed with lime-based Ecologic™ Mortar and applied Ecologic™ Mortar SCG (non-pigmented) as a stucco. Finally, the lime stucco was whitewashed using breathable St Astier Lime Paint “Natural” (non-pigmented) to finish the repair campaign with this traditional whitewash.

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ColorWash Stain, For Brick Walls With Mismatched Brick

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Q: There are some bricks in wall that are mismatched in color. Is there a way to have them match without removing them?

A: While this question comes up from time to time, most often people don’t know that they can easily remedy such a problem and don’t bother to ask. By using silicate stains many colors and variations can be achieved to change the color of masonry permanently.

These stains are applied with a simple foam brush when the bricks are clean and free of moisture. They can only be applied in weather conditions above 40 degrees (F). Prior to a repointing campaign, bricks can be very easily stained and then repointed to achieve a uniform appearance. Since silicate stains are acid resistant gentle masonry detergents can be used to clean smeared brickwork after repointing. Make sure that the silicate staining work is fully cured before any light cleaning, as necessary, so that there is no damage to the stained finish.

Example of brick stained in two different solid colors and 1 example modeled with three different colors to achieve a more distinctive distressed appearance

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Preserving Historic Brick at the Shirley Plantation

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The historic Shirley Plantation is situated along the James River right outside Richmond Virginia. It was constructed in the early 17th century and is the oldest family-owned business in North America as stated on their website. Today, unfortunately much of the brick that makes up the various buildings is literally falling apart. Spalling of the brick faces is occurring in a number of areas. One major contributor to this problem was the use of harmful Portland Cement installed in previous repairs throughout the structures.

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Preserving the irreplaceable brick is currently the top priority. One method that has been very successful is the use of a very simple and natural product called Ecologic™ Waterglass Primer & Consolidant for Masonry. This is a mineral-based fixative, conditioner, and a mild consolidating repair material, sometimes also referred to as a “liquid stone primer.” It can turn the once brittle and crumbling historic red brick back into a more substantial and solid masonry unit once again. The use of Ecologic™ Waterglass Primer for brick and stone consolidation will allow the masonry to continue to breathe and possibly achieve a permanent repair, if the root cause of the masonry decay is also addressed.

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Click here for more information on Ecologic™ Waterglass Primer and our other mineral based paints and stains.

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FAQ Friday: What are Silicate Paints?

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Silicate Dispersion Paint is also known as Inorganic Mineral Paints and is unique in regard to its ability to breathe and supply a long service life to masonry materials. Chemical mineral paints are based on “Waterglass” AKA Potassium Silicate, which has been described as liquid stone. When silicate Paint petrifies a mineral substrate such as brick, stone or concrete, it chemically bonds to not only the surface but also beneath. Upon curing, called Silicification the paint becomes part of the substrate, forming a micro-crystalline coating. Because silicate paint becomes one with the substrate it will mimic the natural water vapor transfer and cannot blister or peel due to the laws of chemistry.

Learn more about silicate paints here

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Repointing A Historic New Jersey Home

Historic masonry restoration completed by the Technical Install Team of LimeWorks.us in Moorestown, New Jersey. This circa 1790 historic brick home was repointed using Ecologic™ Mortar. Ecologic™ Mortar is made with Natural Hydraulic Lime (NHL) and contains NO harmful Portland Cement. The use of Portland Cement to repoint historic buildings will cause premature degradation which may include spalling of historic bricks, moisture build up within the walls, damage from salts, and poor water vapor transmission. Water trapped within masonry walls may negatively encourage moisture issues to begin within the building including mold, mildew, and interior wall damage as well as increase heating and cooling costs.

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What is especially unique about this repointing job is that the entire front façade was found to have remnants of the original white highlighting done within a narrow keyway incised into the center of the joint work. Many photos in the video correspond to the side walls which were simply repointed using the Natural Hydraulic Lime and sand Ecologic™ Mortar struck flat and having no such embellishment. However, the front was accurately reproduced with the highlighting work which is referred to historically as “Penciling.” To learn more about the methods and materials used for appropriate historic masonry restoration visit LimeWorks.us.

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