Mortar Composition Analysis and Matching

AMR Labs
817-366-8376
MortarLab@gmail.com 

You can send samples of hardened mortar for testing to us at the following address.

AMR Labs
1525 Corona Dr.
Granbury, TX 76048

We are making brick mortar cracks disappear. - AMR

AMR Labs is dedicated to matching mortar.
This is why we offer various forms of matching mortar including mortar analysis, mortar testing, sand analysis, mortar composition testing, and custom mortar color matching.

Click here to order/get prices and procedure for mortar composition testing.

Composition Formula of Mortar Mix

Traditional masonry mortar mix was composed of primarily lime, and sometimes hair, grasses, calcium, or Portland cement were added to increase strength, crushing pressure, or help the mortar set more rapidly. This is different from the mortars used today. More recent mortars are designed to have much higher crushing pressure and moisture resistance, and are primarily composed of Portland cement and lime. These are know as Portland based mortars.

Mortar Mix

Mortar mix is used to bind together masonry walls, but it has a greater function. While holding the bricks in place, it has to allow for movement or settling, and is designed to be strong enough to hold the weight of the masonry and soft enough to prevent damage to the bricks if settling occurs.
When repointing masonry, it is important to replace the existing mortar with a similar mortar, and should be matched as closely as possible. Mortars of different crushing pressures and composition tend not to bond together and may cause damage to the bricks. It is for this reason, you must match your mortar type and composition.
In traditional mortars, you have clay based mortar, lime mortar, type k mortar, and type o mortar, and more recent mortars are type N mortar, type s mortar, and type M mortar. The compressive strength of these mortars range from under 75 PSI to about 3000 PSI depending on the mortar type and its composition ratio. The lime based mortars (lime, type k, and type o) crush under 350 PSI, and new mortars (type N, S, and M) crush above 750 PSI. This makes it very important to identify mortar composition ratios.

Mortar Composition Formula/Ratio

The type of binders and the ratio of Portland, lime, and sand in mortar determine the mortar type. With in each mortar type, the composition ratio can vary dramatically. This is because a mortar type can be base on performance (compressive strength) or on composition. For instance, using the formula for type N mortar (1 to 1.25 mix) with more sand or fine rounded sand particles will make a mortar that is "type N" based on composition, but have a much lower crushing pressure similar to a type o in strength. When matching mortar, the ratio and type of binders are important, and can only be identified by testing samples of the existing mortar.

Mortar Testing

Mortar testing is a detailed process of analyzing the performance of mortar and breaking down the composition materials and their ratio. When mortars are analyzed, they are crushed and digested in acid. The remaining aggregate and the weight loss help to determine the total mix and the ratio of sand to mix in the mortar formula. By crushing the sample and analyzing the chemical reaction with acid, the proportions of mix are identified and the ratio of mix to sand is used to finish rendering a formula for replicating the original mortar.

Mortar Composition Test/Analysis

A mortar composition test is the only way to identify the composition and ratio of mix in mortar. During testing mortar samples, there are more factors to identify than just the mortar type and binders. In historic mortar, there are often hairs and grass fibers to identify before acid digestion, and the lime used. Historic mortars tend to use a larger lime particle known as historic lime due to the available screens when the lime was slacked on location for its use. Examining mortar samples for these particles is the first step in testing mortar. Then samples are measured, crushed, weighed, and chemically tested to determine the composition and ratio of mix. Most mortar testing methods use some form of sand analysis to provide basic details about the sand and gradation of particles and their color. For more detailed information about the sand gradation, it is recommended to get a sieve analysis of the sand particle sizes.

Sand Sieve Analysis
The sand analysis provides detailed information about the original sand used. This includes a gradation analysis of the sand particle sizes, color description of particles, and identifies the shapes of sand particles.

Ordering Mortar Composition Testing

We provide mortar matching and composition testing of mortar samples across the country. For pricing or ordering details, click the Services or Pricing link near the top of the page, or click here to learn more about mortar testing.