Welcome to the Architectural Resource Center, which contains information that is designed to make it easier for you to specify a job and to use our materials and services.
If you need additional information, please contact our office at 773-286-2100 or info@usheritage.com |
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| Benefits of USHG Type O Mortar Versus Conventional Type N |
| Posted by: John Speweik, Director of Education |
| 11/03/2008 13:07:52 |
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When ASTM-C270 is specified, two mortars meet the specification:
• Type N qualifies under ASTM-C270
• Type O qualifies under ASTM-C270
U.S. Heritage type O mortar is blended to the ASTM-C270 proportion specifications:
One (1) part portland cement
Two (2) parts hydrated lime
Eight (8) parts sand
Note that ASTM-C270 does not specify sand gradation sizes. Instead “mason’s sand,” which is essentially a one size fits all product, is considered an acceptable aggregate choice, and most contractors do not appreciate the importance of appropriate sand gradation. U.S. Heritage Group trains contractors to recognize the importance of selecting sand gradation that accommodates various joint widths, and similarly, this is an opportunity for contractors to educate their customers why selecting the appropriate sand gradation is important to long lasting performance of masonry repairs.
U.S. Heritage uses the maximum amount of lime in the formula and slightly reduces the sand to enhance workability and deliver optimum bond strength. The USHG Type O is a neutral, natural light grey, and it is an excellent medium for color pigments. By contrast, most type O mortars that are manufactured by high-yield cement plants use more portland cement, producing cool grey color this lacks the warmth of the more traditional Type O, and it is less likely to match historic masonry.
Benefits of USHG Type O Mortar Versus Conventional Type N
Our high lime formula offers the following benefits:
• Better bond strength
• Higher flexibility
• Increased porosity (Larger sand offers increased porosity)
• Breathability
• Improved vapor transmission
• Improved self-healing (Type N mortar, if made according to ASTM property specifications, requires no lime in the formula. Since autogenesis healing relies on lime, Type N mortar has no self-healing properties)
• Color enhancement (less pigment is needed to achieve desired color)
• Compressive strength is 750 – 950 psi after 28 days (equal to type N)
Type O mortar offers another substantial advantage for the contractor: the flexibility to easily match color in the field. Our premeasured color pack system, which is one bag of pigment to one 80 lbs. bag of mortar, offers 24 colors in stock and ready to use. To achieve a darker color, add two color packs. This offers a total of 48 instantly available color options.
U.S. Heritage Type O Program
Replacement of all Type N ASTM-C270 specifications
• Purchase pre-blended type O by pallet quantities (42 per pallet, medium sand)
• Stock the pigments for 48 standard colors
• USHG to provide 2- 24 piece color kits, additional color kits can be purchased at a reduced cost
• Contractor specific information sheet explaining the advantages of type O with the intent to educate your customer and differentiate yourself from the competition. |
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| Why Specify Preblended Products? |
Achieve a Precise Match
U.S. Heritage Group is the only mortar manufacturer in the United States that offers a quality mortar matching and custom blending service utilizing a national sand library. Our commitment to quality starts with identifying the raw materials used in the original mortar through laboratory procedures that correspond to the U.S. Department of the Interior, National Park Service guidelines for historic masonry. All mortar formulations are designed specifically for each application condition to maximize life cycle performance. All mortar products comply with appropriate ASTM or ACI compliance when applicable.
Mortar products are weigh batched, in contrast to volume batched at the jobsite, which eliminates the chance of any inconsistencies. The use of "wet" lime putty is new to the modern jobsite, and a lack of familiarity with the material accounts for many contractor mixing mistakes. By contrast, our production process accounts for each mix component, wet or dry, to ensure that the finished mortar complies to design and specification requirements.
Consistency
Consistency is maintained in each production run by using dried sand from our national sand library, which eliminates the bulking effect associated with varying moisture within the aggregate. (The size of the sand and its moisture content at the time of mixing can change in volume by as much as 30 percent at a jobsite.) Additionally, it is well documented that hydrated lime has a volumetric loss of 25 percent when converted to putty with the addition of water. To protect against problems associated with improper proportioning, all sand, cement, hydrated lime, lime putty, hydraulic lime and pigments are preblended together at our factory in controlled conditions.
Efficiency
U.S. Heritage Group custom preblended mortars significantly reduce the labor required to formulate and install mock ups for architect approval. Most projects require a contractor to install mortar mock up samples for comparison against the original material, and while this requirement seems straightforward it is often complicated by vague testing report results and the difficulty of obtaining satisfactory raw materials to make the mortar.
U.S. Heritage Group's preblended materials allow the masonry crew instead to concentrate on wall preparation, mortar installation and finishing. Consistent mortar is guaranteed, with the result being higher quality, consistent materials. We also archive our material formulas and testing results, so we can replicate the mortar upon request at any time. |
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