Evaluation

The primary objectives of the project are to evaluate the working properties and performance characteristics of injection grouts for the conservation of architectural surfaces, including plasters, wall paintings and mosaics, and to provide reliable tools for conservators and conservation scientists to assess and compare different grouts in the laboratory and field.

Components of the project include:


Specifically the project seeks: to inform practitioners in the field on the properties and performance of different grouts and grouting materials, to correlate scientific research with conservation practice in the field, and to disseminate the project results through laboratory and field workshops, publications, and a seminar.

lab testing - injection grouts
 

Background
Seminal research on injection grouts for the conservation of architectural surfaces was conducted by ICCROM in the early 1980s, coinciding with the movement toward preserving these architectural features in their original context, rather than detaching them, as was previously practiced. Following development of hydraulic lime-based grout formulations at ICCROM in the early 1980s, numerous variations of these injection grouts have been produced and widely used over the past twenty-five years, including a number of commercially produced grout mixtures. In 2004, the GCI initiated an interdisciplinary study between its Field Projects and Science departments to evaluate injection grouts used in the conservation of architectural surfaces. The project aims to assess the properties of commercially produced and custom-mixed injection grouts widely used in the past twenty-five years to preserve architectural surfaces in situ—a current practice in most of the world. The project aims to combine laboratory testing and field study of these grouts to inform conservators and conservation scientists of the range of injection grouts used in the field, and to improve conservation practice.

conservators working with grouts
 

While manufacturers provide technical data for their products, and testing on custom mixes has been carried out, no single testing method is in use. This makes it difficult to compare and evaluate different injection grouts. Additionally, no limiting-values or criteria to evaluate and compare different grouts have been specifically defined for working properties and they have been defined only in a few studies for performance characteristics. A variety of test methods for the preparation, characterization, and evaluation of grouts has been used—in most cases standardized tests developed for other materials (e.g., mortars, epoxy resins, cement-based binders, etc.) with modifications.

Furthermore, limited systematic research has been done to assess the acceptability and usefulness of these modified laboratory test methods to evaluate injection grouts. At this time there are no standardized tests specifically designed for injection grouts used in the conservation of architectural surfaces, and scant information has been published on field testing.

Project Overview
In 2004, the GCI initiated an interdisciplinary study between its Field Projects and Science departments to evaluate injection grouts used in the conservation of architectural surfaces, including plasters, wall paintings and mosaics. The project aims to assess the properties of commercially produced and custom-mixed injection grouts widely used to preserve architectural surfaces in situ, a current practice in most of the world. The project aims to combine laboratory testing and field study of these grouts to inform conservators and conservation scientists of the range of injection grouts used in the field, and to improve conservation practice In 2005, the GCI convened a meeting of conservators and conservation scientists to discuss the current state of grouts and grouting practice and to exchange ideas on avenues of further research. The project team compiled a bibliography (link) and drafted a literature review on the topic. As a result of the specialists meeting and literature review, the project has focused on the identification, refinement, and development of a suite of tests specific to injection grouts, which can be disseminated to scientists and conservation professionals in the field.

wall painting at Herculaneum
 

As a field component of the project, the GCI project team has been working with conservators at the archaeological site of Herculaneum to advise them on test methods and selection of materials for the reattachment of plasters at the site based on laboratory testing and evaluation, and developed a suite of field tests to be used by conservators to further evaluate injection grouts on site.

Since 2009, the GCI has organized workshops and lectures on the evaluation and testing of injection grouts for the conservation of architectural surfaces. Workshops aimed to provide an overview of the characteristics, properties, and uses of injection grouts for the conservation of plasters, wall paintings, and mosaics, with a focus on the desirable properties and parameters for their use in conservation.

In 2013, a manual of laboratory and field test methods, the Evaluation of Lime-Based Hydraulic Injection Grouts for the Conservation of Architectural Surfaces was published and is available as a free downloadable PDF and a print-on-demand publication.

The project team is currently involved in the RILEM Technical Committee 243-SGM "Specifications for non-structural grouting of historic masonries and architectural surfaces" contributing to the development of recommendations for the selection and use of injection grouts for non-structural purposes.

Last updated: September 2013