Products and technologies for conservation and restoration: geopolymers and hydraulic mortars

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The products for the preservation and restoration of ceramics and stone in the Cultural Heritage must be compatible with the materials on which you operate and durable and stable over time.
Geopolymers, mortars based on hydraulic lime or nano- limes + meta kaolin meet these requirements.


Geopolymers for their versatility can be used for large and small conservation works on individual artefacts and archaeological sites and / or architectural complexes, such as:

  • Filling gaps and cracks;
  • Adhesive for detached elements;
  • Reproductions of missing parts.

They are made from natural inorganic raw materials (clays and rocks), processed at low temperatures (low environmental impact), they react with alkaline solutions and harden cold. They are easy to handle.

Mortars based on natural hydraulic lime or lime and meta kaolin are ideal for:

  • Securing of archaeological structures;
  • Re placement of mosaic fragments on movable support;
  • Recovery of historic buildings; 
  • Interventions on historic buildings and green building, for the recovery of historical centres. 

They have set times fast. They are excellent and natural alternative to cement mortar, not fully compatible and soluble salts that develop over time.

The product-based on nano-lime and meta-kaolin with nano-size can be injected deep into the cracks, allowing the formation of hydrated silicates, and then to a full hydraulic set that does not need air.



M. Macchiarola, S. Belacchi, D. Pinna, G. Ercolani, A. Ruffini, C. Fiori, Study on the deterioration and conservation of the monument dedicated to the Fallen in the “Risorgimento” battles, Ravenna (Italy). Structural Studies, Repairs and Maintenance of Historical Buildings, VIII, pp. 163-172 (2003).

B. Fabbri, S. Gualtieri. Alterazione post-deposizionale di ceramiche neolitiche con formazione di macropori e arricchimento di fosforo. Rendiconti ondine Soc. Geol. It., Vol. 2, 361-362 (2008).

M. Macchiarola, G. Fiorella. The study of hydraulic lime mortars for the conservation of mosaics, Proceedings of the 9th Conference of the International Committee for the Conservation of Mosaics (ICCM), “Lesson Learned: Reflecting on the Theory and Practice of Mosaic Conservation”, Hammamet (Tunisia), December 2005, pp. 273-280 (2008).

M. Clementini, M.G. Maioli, E. Carbonara, M. Macchiarola. Piazza Ferrari a Rimini: Il mosaico del triclinio nella “Domus del Chirurgo”. Un Intervento tra restauro e manutenzione, Atti XV Colloquio AISCOM, Aquileia 4-7 Febbraio 2009, pp. 183-191 (2010).

B. Fabbri, S. Gualtieri. Impiego di materiali geopolimerici come adesivi nella conservazione di manufatti in pietra naturale o artificiale. Atti IV Convegno –Monitoraggio e Conservazione preventiva dei beni Culturali, G. Mascolo (ed), 27-29 maggio 2010 Cassino, Poligrafica Ruggiero srl- Avellino, 15-22 (2010).


The research and development of these products follow a logical sequence in order to define novel products suitable for specific interventions:

  Design material:

  • geopolymers (meta-kaolin/alkaline solution ratio, type of alkaline solution);
  • hydraulic mortar (aggregate/binder ratio);
  • hydraulic nano-lime (aggregate/addition ratio);
  • preparation materials:

i) evaluation and characterization of commercial kaolins by XRD, ICP and particle size analysis;
ii) grinding and firing of kaolin (T = 650° and 750°C for 2 h at Tmax);
iii) characterization of meta-kaolin by XRD and testing of reactivity with Ca(OH)2,SEM-EDS;

 Characterization of the obtained products:

i) geopolymers (release of soluble salts, mechanical strength, resistance to acids, measures of color, durability evaluation);
ii) natural hydraulic mortar (characterization of the binder, minero-petrographic characterization of the aggregates, evaluation of hydraulic level, mechanical strength, porosity (MIP), release of soluble salts, adhesive strength, durability assessment);
iii) nano- lime + meta- kaolin (evaluation of hydraulic level, mechanical strength, adhesive strength, porosity (MIP), determination of the setting and hardening time, durability evaluation).


  • Institute for the Protection of Cultural Heritage of Slovenia
  • Central Institute for Conservation in Belgrade (Serbia)
  • Soprintendenza per i Beni Architettonici e Paesaggistici (Ravenna)
  • Università di Bologna, Facoltà Chimica Industriale
  • Fondazione RavennAntica