Welcome to AMR Labs.
Our focus is high quality masonry repair and the products and services needed to ensure the mortar repair is done right. Among these are mortar testing, mortar matching, pre-matched mortar mix, and other masonry repair products.
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Mortar Matching Services
Mortar matching is available in many forms, but not all methods of matching mortar will work for any project. This is especially true of the most commonly used method.
Mortar Matching Method
In the most common mortar matching method, there are assumptions made in matching the mortar mix type, sand color and gradation, and pigments, and the mortar is adjusted to provide a matching color only. This practice is unacceptable in the repair and restoration of masonry. Changing the mortar composition, mortar type, mortar formula, sand color, sand gradation, or the formula of sand to mix ratio also changes the compressive strength of mortar, color and texture of the mortar, and the ability of new mortar to bond with old mortar. This generally results in re-cracking of the mortar joints, chipping or spalling brick faces, and other damage to the masonry walls.
Testing Mortar Samples to Match Mortar Color and Composition
Mortar Match Test
Mortar testing provides a detailed mortar analysis for matching old mortar. This mortar matching test provides accurate usable data about the mortar and provides a detailed mortar formula for matching the original mortar samples tested from which the color can be adjusted to match as needed.
Custom Mortar Matching
Composition Matching of Existing Mortar Mix
Through analyzing and testing the composition of samples of existing mortar mix in a detailed mortar analysis, the complete mortar composition formula is provided. This is the base for any custom mortar color match or custom mortar matching. With the base formula, minor adjustments can be made to adjust mortar color for the rest of the mortar match without changing the mortar type, crushing pressure, bond ability, or ratios. By custom matching the mortar in this manner, you will reduce the inconsistencies of color matching mortar, insure a better bond, and prevent damaging the bricks with mortar that is too hard or soft.
Historic Mortar Matching
Matching Historic Mortar
In commercial and historic mortar restoration, it is common place to get the mortar analyzed and matched through testing samples of the mortar. However, many of the testing methods are over priced and inaccurate. The two most common used or recommended testing methods for historic mortar analysis are the ASTM C-1324 and acid digestion method of testing hardened mortar. These two mortar testing analyses are the most and least expensive tests, but neither provide reliable results.
Testing/Matching Mortar Composition
C-1324 is the most expensive type of historic mortar analysis which uses a spectrographic microscope to create a colorful image of the mortar sample. This image is then visually inspected and a best guess of proportions for the ratio is determined as the composition formula. There is a little more to it, but the accuracy of the results is limited to the interpretation of the analyst and their onsite experience as a mason. With their limited or likely non-existent experience in the field, they are unable to provide a quality interpretation of the testing data.
The acid digestion method for testing mortar composition is the least technical and least expensive mortar analysis, and is the most commonly used method for testing old mortar. Acid digestion analysis uses a balloon to capture the escaping gases released during analysis. The balloon swells and is measured to determine the quantity of the total binder materials. This test alone is not capable of accurate results because, the results are still an interpreted analysis of how much of the gas released is coming from each binder material. This factor alone is problematic because the sand aggregates tend to have a portion of cementious material that contaminates the results. Some sands used are entirely cementious materials. This doesn't happen often, but it does happen.
Matching Mortar Composition Mix
There is a better way to test the composition of mortar samples for historic mortar matching, and it is not much more expensive than the acid digestion test. This method is proprietary to AMR Labs and is becoming more excepted for this use due to the accuracy of the results. This testing method for matching mortar composition combines the results of some other astm testing methods such as the C-109 crushing analysis, acid digestion, E-11 sand sieve analysis, and some more scientific analyses where we collect additional data from some of these other testing methods for validations.
One example of this is the amount of weight loss during the digestion of mortar samples is cross referenced with the compressive strength and mortar type and using the specific gravity of the binder materials, we are able to validate the accuracy of the results. This is a limited example because there are other factors that change variables such as the size and shape of sand aggregates changes the compressive strength of the mortar as much as the ratio of sand to mix.
Matching Existing Mortar
Match Existing Mortar Formula
Mortar matching through our complete mortar analysis and adding a detailed mortar color match provides a exact mortar formula for matching the existing mortar color and composition. With this complete formula, we can manufacture bags of custom matched mortar for your project. This is however limited to mortars using type S/SA lime as we currently do not have a supplier for the historic lime.
Historic Lime Mortar
In the past, we provided the analysis report and the formula and Virginia Lime Works provided the manufacturing of the historic lime mortars. We have been told they are no longer around and we haven't found a suitable replacement as yet. Places we have found that may assist you if you need the historic lime mortar manufacturing are US Heritage Group and Lime.org.
Type S/SA and Historic Lime
One of the most common questions asked is the difference between historic lime and type S/SA lime in mortar. The simple answer is they are both lime, but the historic lime mortar uses a larger particle size and was sometimes not screened allowing large chunks to be mixed into the mortar. This is easily recognized by the large unmixed pieces of lime. Those that were screened are a little harder to identify, but the type S/SA lime uses a very fine screen, and tend to be used in harder mortar types and newer mortar more often. If your mortar requires type S/SA lime, we can provide the manufacturing of custom bags of pre-matched mortar mix.
Custom Mortar Mix
Pre-matched mortars are bags of mortar mix custom made to match the existing hardened mortar of your masonry repair. These bags are made using the formula from the mortar matching test.
Other Mortar Repair Products
We are in the process of building a list of onsite service providers for the brick repair and mortar restoration services to assist you in finding a local service professional. If you are a service professional, please contact us to submit your company for inclusion in this listing.
We are in the process of building a list of local consultants to assist customers involved in masonry preservation. If you are a service professional, please contact us to submit your company for inclusion in this listing.