EC

- Electrical Conductivity -

Used to identify the presence and measure the amount of soluble salts in building materials based on their response to electric conductivity.

WHAT IS IT FOR

dating

morphology

technology

origin

composition

alteration

APPLICABLE MATERIALS

Ceramic

Mortar

Stone

Stone, Mortar & Plaster, Ceramic Building Materials (CBM)

EC tests are performed in order to monitor both surface and internal soluble salts, to quantify their concentration in a specimen, to test the “state of health” of a building material before salt reduction/extraction treatments, to locate possible humidity sources (which will present higher soluble salt concentrations) and to test the resistance to saline attack of replacement materials in the laboratory prior to their use.

BRIEF DESCRIPTION

Electrical conductivity test diagram

Electrical conductivity tests are used in order to map the presence and distribution of soluble salts, as well as to quantify them in a material. EC does not identify the nature of those salts, but can be used to measure their concentration in a given material. Produces graphs depicting the salinity percentage of the sample.

Electrical conductivity test diagram

Metrics

accuracy
time
cost

Sampling

in situ

invasive

destructive

TIPS

Used to identify the presence of soluble salts and quantify them
To determine the nature of these salts complementary analyses like: XRD, SEM-EDS, Ion Chromatography, Raman, etc are reacquired

Advantages

fast
readily interpretable results
applicable on any kind of building material
non-invasive towards the specimen
does not require high expertise

Limitations

duration can be long for materials with very low porosity
only provides qualitative information

HOW DOES IT WORK?

Electrical conductivity (EC) refers to the ability of a material to conduct an electric current. Electrical conductivity increases proportionally to the concentration of soluble salts. However, not all salts are equally soluble in H2O. To perform EC tests an alternating current source produces an electric current which flows from one electrode to the other, through the specimen or through the salt-bearing water solution of a sample which has previously been immersed in distilled water. A temperature sensor collects temperature measurements and a converter transforms electrical conductivity into salt content data.

References

Blanco, M., Colucci, M. F., Franco, B., Gisbert, J., López, P., Sanchez, A., 2006. I Sali Negli Interventi di Restauro: Cartografi a e Diagnostica. In: Vanni Badino & Giuseppe Baldasarre eds., Le Risorse Lapidee dall’antichità ad oggi in Area Mediterranea. Atti del convegno. Canosa di Puglia (Bari) 25-27 September 2006, pp. 123-128. [online] Available at http://www.researchgate.net/publication/39711158_I_Sali_Negli_Interrventi_di_Restauro_Cartografa_e_Diagnostica [Accessed 16 February 2015].
Blanco, M., Colucci, M. F., Gisbert, J. 2006. Modello di Distribuzione e Movimento dei Sali nei Materiali Lapidei Porosi. In: Vanni Badino & Giuseppe Baldasarre eds., Le Risorse Lapidee dall’antichità ad oggi in Area Mediterranea. Atti del convegno. Canosa di Puglia (Bari) 25-27 September 2006.
Genestar, C., Pons, C., 2003. Ancient covering plaster mortars from several convents and Islamic and Gothic palaces in Palma de Mallorca (Spain). Analytical characterization. Journal of Cultural Heritage 4, pp. 291–298. [online] Available at http://isiarticles.com/bundles/Article/pre/pdf/1226.pdf [Accessed 8 February 2015].
Klenz Larsen, P., 2000. Salt damage to the Medieval plaster on a vault in Fanefj ord Church. In: P.Bartos, C. Groot & J. J. Hughes eds., PRO 12: International RILEM Workshop on Historic Mortars: Characteristics and Tests, pp. 43-50.
Svahn, H., 2006. Chapter 4: NDT Methods – Theory and Application. In: Final Report for the Research and Development Project. Non-Destructive Field Tests in Stone Conservation - Literature Study, Stockholm: Riksantikvarieδmbetet, pp. 21-27. [online] Available at http://www.raa.se/publicerat/9172094354.pdf [Accessed 8 February 2015].