Mortar testing is a primary service that we offer at Sandberg. We have many years of experience and have encountered a wide range of different mortar compositions, both modern and historic.
Mortar testing, in the case of modern mortars, may be required to establish compliance with a specification or as part of a failure investigation and can also highlight any deleterious materials such as sulfates, which can attack cement binders, causing cracking and eventual mortar failure.
When dealing with historical mortars, Sandberg can analyse mortars so that suitable replacement materials can be used to repair damaged or failing material. This can not only serve to maintain the authenticity of the materials but will also help historical structures as like for like materials will age and behave in a similar manner to the original mortar, preventing further mortar failure.
We can undertake mortar testing on both modern and historic mortar to establish both a mortar’s composition (mix proportions) and undertake an aggregate particle size distribution or grading. Sandberg has UKAS accreditation to undertake mortar testing using a range of British Standards, including BS 4551 or our own in-house methods.
Information about Mortar
Mortar is a fundamental building material found in most modern and historical buildings. It has been used in some form or another dating back to early civilisations such as the Romans, Greeks and Egyptians. The constituent materials used have changed somewhat over time but their function has remained the same: to be used as a binder for brick and stone blocks in construction and as a bedding material in pavement construction.
Today the most commonly used materials in mortar are ordinary Portland cement (OPC), with or without lime, which is mixed along with sand and water in various proportions to form a hardened adhesive material.
One of the earliest and strongest binders used in construction was called Roman cement which is a hydraulic lime which develops strength properties similar to a modern Portland type cement. Lime was found to be an excellent building material and was used extensively in the past and is still used today due to its excellent binding properties and workability. Depending on other minerals found within the original quarried limestone, it can have various hydraulic properties. Today we see the use of NHL 2, NHL 3.5 and NHL 5 as modern-day equivalents of the different hydraulic limes used in the past. Occasionally gypsum is incorporated into lime mortar mixes. Historic mortars have also been found to contain materials such as eggs, animal hair and even dung.
In the 19th century, Portland cement was introduced as a binder and is now the most commonly used binder found in modern buildings. Along with its very desirable binding ability, it provides excellent compressive strength and is highly durable.