Authenticity

The Mortar Selection Decision Tree

For most projects, the place to start is with an accurate analysis of the original materials. The most useful analyses will employ Thin-Section Microscopy and Chemical Analysis (ASTM C1324). Microscopy is used to identify mortar components and chemical analysis quantifies their proportions and separates out the sand so it can be matched.

Evaluate the original mortar. Did it perform well?
If so, replication may be the best approach. Are there basic flaws (e.g., oversanded, undersanded, poorly graded, over-pigmented) that should be corrected? If simple corrections will allow the use of what is otherwise a near-replication mortar, this is often the best approach.

Are the original materials available?
Historically, a wide variety of mortar-making materials were used. Many of these, or their modern near-equivalents, are still available today. Some are not. If they are available, it is usually better to use them, rather than substitute materials. If they are not, a performance-based analog should be formulated.

Will the original materials perform well as restoration materials?
Conditions change over time, and materials that worked well in a new construction setting may not perform well in a restoration setting. Lime mortars, for example, worked well in foundations built from new brick or stone. But after 100 or more years of groundwater exposure, the salts absorbed by the masonry can prevent lime mortars from properly bonding. If the original materials will perform well, use them. If not, a performance-based analog can be formulated.

Need Help? Call Us!
We have the knowledge, authentic materials and experience to make your project a success! Call us at: 1-800-341-6621