AZRAQ | My Site 1

Study of traditional mortar production techniques at Qasr Azraq, Jordan

PROJECT OVERVIEW

We explored the mortar production techniques used at the Roman castle Qasr Azraq in Jordan, by conducting field visits and analyses.

PROBLEM

There are very few published works about traditional production technology in the country, based on a scientific approach.

MAIN GOALS

Provide relevant information about traditional mortar production technology.
Provide information about different technologies used during time.
Reconstruct the timeline of different phases of the site.

RESPONSIBILITIES

Led the full research process: designing, planning, and executing the research, and communicating results.
Kept contacts with external partners, and other stakeholders.

TEAM

I was a 'research team of one’, with participation from many other stakeholders, as scientists of the NCSR "Demokritos", architects, archaeologists, and other stakeholders.

METHODOLOGY

A) Several field studies structured as follow:

Unstructured interviews: I spoke with, and asked questions to, archaeologists, architects, members of the Department of Antiquities (DoA), and other stakeholders.
Purpose: to know about the more recent history of the site, including restoration activities and archaeological excavations, and about traditional and historical building techniques in Jordan.

Contextual inquires: with people living in Azraq, whose family members inhabited the castle at the beginning of the 1900.
Purpose: to know about the occupation of the site in recent years.

12 contextual visits to Qasr Azraq and other coeval castles in the area, also together with relevant stakeholders, for in situ observations, to take pictures, to observe similar construction techniques in coeval sites.
Purpose: to plan and conduct the sampling campaign, and to conduct the photogrammetry.

B) Cross-functional data analytics

Methodologies: optica microscopy (om), XRD, pXRF, SEM, statistics. Each of these methodologies provides different kinds of information about the composition of the analysed objects.
Purpose: to characterise the building materials, to find patterns that represent different types of mortars and different technological choices.
Software used: Photoshop, Gimp, AgisoftPhotoscan, Excel, Minitab, R, X’Pert HighScore Plus.

C) Analysis of other similar researches

Exploration of other works about same or similar research questions and how they approach their challenges or interpreted results.

D) Triangulation

Cross-functional insights obtained from data science, and field studies were triangulated.

KEY INSIGHTS

Qasr Azraq had been reused and inhabited from Roman times until the 1930 when it was declared a 'cultural heritage site' by the DoA.

In recent years the castle underwent several restoration and excavation interventions.

In different historical periods, different building materials (lime/gypsum/... mortars) and architectural structures (arches, linear corbel stone ceiling, ...) were used.

At least 7 different types of mortar reflecting different technological choices in different times were used.

RESEARCH PROCESS SUMMARY

IMPACT

We achieved a better understanding of the building materials and techniques employed at the site, and more in general in the Near East, during time.

The project results were well received by the members of the DoA, as they will help to plan focused restorative interventions in the future.

The research was published as a chapter in a book, and in a peer reviewed journal. So far the paper has received 12 citations and 5 recommendations.

SUGGESTIONS FOR NEXT STEPS

Due to the bad state of conservation of the building materials, it was not possible to precisely date the use of different techniques. However, we could define a relative chronology of the mortars, thanks to superimpositions of different types and make hypotheses based on historical data. In order to gain precise information about the chronology of different mortars and techniques adopted at Quasr Azraq, an accurate stratigraphic study should be done.

DESIGN OF MORTAR TECHNOLOGY

Based on what learned along the journey, and in collaboration with stakeholders, I was able to characterise the mortars used at Qasr Azraq and to achieve a better understanding of the building materials and techniques employed during its life-time.

Some more insights on the research process:

RESEARCH PLAN

1. Documentation

2. Fieldwork

3. Photogrammetry

4. Sampling

5. Mortar characterization

6. Synthesis & interpretation of results

7. Dissemination of results

FIELD STUDIES

Conducted several field studies comprising:

- contextual inquiries

- contextual visits

- stakeholders interviews

Goals: to learn about the most recent history of the site (recent restoration activities, archaeological excavations, ..) and traditional building techniques in Jordan.

linear corbel stone ceiling type

stone blocks

transverse arch (or other supporting structures)

PHOTOGRAMMETRY

Photogrammetry is the science of obtaining reliable information about physical objects through the process of recording, measuring and interpreting photographic images.

Since the existing graphic documentation of the castle was insufficient, I performed photogrammetry to obtain reasonably true-to-scale images of the facades of the castle.

These images allowed us to take precise measurements, and to record the position of the sampled mortars.

SAMPLING CAMPAIGN

According to the macroscopically recognizable characteristics of mortars, the available quantities, and their location, a sample of the identified mortars was selected, in order to have as representative picture as possible of the site

MACROSCOPIC GROUPS

The initial grouping of the mortar samples was based on macroscopic observation of mortars, giving emphasis to the color, and size, shape, type and amount of the inclusions.

Five groups were macroscopically recognized.

A1

A2

B

C

D

E

ANALYTICAL METHODOLOGIES

Analytical methodologies were applied to characterise the building materials used, to find patterns among the samples, to reconstruct their production technology, and to explain cultural choices.

Optical Microscopy

17 samples representative of all initial groups were analyzed under a microscope and 4 groups were recognised.

F1a

F1b

F2

F3

F4

XRD

A mineralogical examination was performed by XRD. Results were compared with those obtained through other techniques.

1 = scarce

2= common

3 = abundant

4 = very abundant

pXRF

A chemical analysis was conducted by pXRF and statistics were performed on the results obtained. Multivariate statistics as PCA were performed to see how well defined the mortar groups are.

A simple linear regression was performed selectively on mortars of groups B and C (lime-gypsum mortars), on the var S vs. Ca contents.

The scatter plot showed that groups B and C differ in their Ca:S ratio, confirming their existence.

Cross-functional insights obtained from data science, and field studies were triangulated.

The initial grouping of the mortars based on macroscopic observation identified five groups (A-E). In the first group (A) two subgroups were suggested based on different shapes and colors of the aggregate.

Both optical microscopy and XRD analyses distinguished subgroups A1 and A2, confirming that they were real and provided important information about their composition, while they couldn't recognise differences between samples belonging to mortars B and C (= F2 and XRD4). Therefore, it was necessary to find other ways to check if the two groups existed.

With this purpose, a linear regression analysis was performed selectively on mortars B and C. The high value of R^2 indicates that the results are significant, and the scatter plot shows that groups B and C differ in their Ca:S ratio, confirming their existence.

TRIANGULATION