30.2 Work in progress -PLM: always under check.


We are reporting a couple of case studies about evaluation of grouts, we think those publications had not enough visibility in spite of the interesting findings.
And for sure, we are pleased that in both cases PLM grouts had been chosen for the trials.

In the first case study [1], conducted by a team of scientists of the Getty Conservation Institute and then published by the International Institute of Conservation, Reviews in Conservation; is related to a wide range of comparative tests.
Here are the main purposes:

-to evaluate the performances of the most popular grouts for restoration.
-to set up and tune up the analysis procedures by choosing techniques that provided useful data.

They left some grouts out of the list, i.e. the cement based grouts, used for reinforcing structural elements and they focused just on the grades suitable for the consolidation and adhesion of wall paintings, plasters and mosaics 
in situ.
The preliminary investigation on bibliographies and scientific papers offered a deep insight about the techniques adopted around the world up to now. 
Among the required properties being examined we should mention:
-the high level of injectability connected to fluidity/viscosity
-absence of any sedimentation or separation processes of inert agents
-reasonable time for setting-ability to set in humid environment with no air
-low toxicity
-high workability.
The research encountered some difficulties when implementing the standards for testing, such as that one for determining the fluidity (formerly calibrated only on viscous mortars). 
Later they focused on the mechanical properties, especially on compression resistance and adhesiveness. Some criticism arose because restorers had worked in different places and adopted the procedures and standards of their home Countries (for instance when preparing mixtures, or seasoning their samples and so on), so that it was difficult to compare numerical data.
We are glad to know that one of the authors, during her presentation at the Conference “Filling the void” (held by ICON in London, 2009) underlined PLMs good performances.

The second case study [2] is related not only to the grouts but also to those polymeric agents used as consolidants for the same purposes. Actually that study was the sequel of an experimental investigation conducted in 2004 [3]. In order to re-created a situation similar to that one of uncohesed wall or rubble masonry they put a mixture of stone fragments and thinner inerts inside a plexiglass cylinder. Then they poured a water solution of resin in that, finally they cast the grouts.
Here are the polymeric resins chosen for the tests: Akeogard AT35 (polyurethane based resin); Acril 33 and Acroterio and Acrisil 201 (acrylic resins); Akeogard PU (fluoride based resin); Stoprim Micro (siloxane based resin); Aquazol 500 (calcium caseinate). In addition, they carried out trials with Keim Spezial-Fixative, a barium hydroxide and potassium silicate based product.

Among the grouts 
PLM-M, PLM-AL and Microlime Novecento had been chosen and studied.

After comparing different percentages of resins and different techniques, it turned out that Acril 33 and Akeogard were the most effective(unfortunately, too expensive for these applications). Nowadays they are not on production anymore.

PLM-M has been chosen as the best grout because its ability to deeply penetrate the substrate.

Therefore Acril 33 and PLM-M represented the best selection for the definition of performing operational conditions.

The scientists said they will go further and compare the selected products with other resins and grouts available in the market.


1. Biçer-Simsir, B., Griffin I., Rainer L., Palazzo-Bertholon B., "
Lime-based injection grouts for the conservation of architectural surfaces, Reviews in Conservation, vol. 10, pp. 3-17, 2009. 
2. Doglioni, F., Mirabella Roberti, G.,Guadagnin, A.; "
Sperimentazione di tecniche e prodotti per il consolidamento di murature decoese a piu’ paramenti”. Project Report. RELUIS - Rete dei Laboratori Universitari di Ingegneria Sismica, Venezia. (2006) (not published)
3. Doglioni, F.,Mirabella Roberti, G.,Guadagnin, A.; "Sperimentazione di materiali consolidanti applicati a nuclei decorsi di murature a più paramenti”, in: Dalla conoscenza e dalla caratterizzazione dei materiali e degli elementi dell’edilizia storica in muratura ai provvedimenti compatibili di consolidamento. Edizioni del Politecnico di Milano - DIS, Milano, (2004)pp. 85-96