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4 May 2011

Wednesday 4th May 2011; Mortar Analysis

Week 4 of 12

Module 3: Material Characteristics and as a Building Material

The topic of discussion today with David Odgers was 'Mortar Analysis'. I have been looking forward to today's topic as it is my day-to-day work at the Scottish Lime Centre Trust (SLCT) and I have been interested to know how the basic and more complicated techniques vary internationally. In fact, from what I have seen today there is not a great variation in analysis techniques and everything we were shown are things that we do at SLCT. The most important message that David put across today was the importance in how the results are interpreted, which a message that we always try to reinforce to our clients at SLCT; mortar analysis is just one stage in the interpretation and writing of specifications for new work. We would always prefer to carry out the site visit, mortar analysis and write the specifications for new work ourselves in one package. Unfortunately this is not always financially possible for our clients which is why we carry out stand-alone analysis services as well, but it relies on each client carrying out the other important parts of the work and having a good knowledge of the materials.

David made the point that it is always best to take mortar samples from the least accessible areas on a building/structure. This is because they're the least likely to have been repaired/replaced (due to accessibility) and are more likely to reflect the original materials. Of course, these are also the least easy to access so unless there is a scaffold it is often necessary to make do with a sample from a more easily accessed area- this needs to be taken into account when carrying out any work associated with the samples. We were shown 6 images of mortars used on York Minster, UK and all were visibly different, which was a good demonstration that you need to know what is being analysed and whether it is representative. At SLCT we always make the proviso with all of our mortar analyses that the analysis is based on the single sample and does not tell you how the mortar varies across a building, hence the need for methodical and documented sampling in the first instance. When we make the site visit we will always aim to locate a representative sample or samples.

David gave us a reference for a book which has many good illustrations of materials to aid basic analysis work; Jeremy Ingham 'Geomaterials Under the Microscope'.

We followed the lecture with a lab session carrying out basic acid dissolution analyses on mortar samples that we have brought from our home countries. We will continue the analyses and interpretations tomorrow.

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