Non-structural injection grouting aims to stabilise delaminated plaster by introducing in the void, typically between delaminated plaster layers, a compatible adhesive material with bulking properties (the injection grout). Injection grout formulations are firstly tested in the laboratory to determine their performance characteristics including their physical-mechanical compatibility with the original materials (plaster or other building materials). However, laboratory tests on grouts are often not sufficiently representative of actual cases in which the grout sets between two plaster layers. This problem is particularly significant when water vapour permeability, capillary water absorption and adhesion need to be assessed. A study was conducted on the development of a ‘sandwich’ system (plaster-grout-plaster) to better simulate the real situation. This paper describes a new methodology for such specimen preparation and the adapted procedures for laboratory testing. The results are discussed comparing them with those obtained from standard specimen preparation and testing procedure.

Conventional grouting – used to stabilise delaminated plaster – typically involves the use of water as suspension medium. Water can be dangerous when water-sensitive original materials are present and can cause the solubilisation of salts, leading to their re-crystallisation on drying. Ethyl alcohol is a less effective solvent for soluble salts and generally does not affect the original materials. This is the reason why it was used as a partial substitute for water in grout preparations in the present research. Three water–ethyl alcohol-based grouts were compared with the correspondent water-based grout. The working properties and performance characteristics of the injection grouts with reduced water content were measured to assess their suitability for use on historic plasters.

The design and evaluation of site-specific injection grouts for the stabilisation of delaminated wall paintings is often challenging to perform in situ, due to constraints such as time, availability of materials and reliable testing procedures. In this research, a rigorous design and testing methodology, including the development of a new adhesion test, was adopted on-site for the development of injection grouts to be used in water-sensitive situations. Water-reduced mixtures were obtained by partly substituting water with ethanol. Previous research by the authors had demonstrated in the laboratory the potential suitability of water–ethanol grouts. In the present paper, water-reduced grouts were designed, tested and applied on-site for the first time.

The development of a treatment for a seventeenth-century CE wall painting scheme in Valletta, Malta, highlights the particular challenges of cleaning oil-based wall paintings. Materials selection a...

During field development of a microgrout for the stabilization of painted lime plasters detached from a limestone substrate, diethyl oxalate-based formulations out-performed microgrouts based on nanolime, colloidal silica and ammonium oxalate, creating more cohesive and homogenous set materials, with better working properties. However, unlike ammonium oxalate, diethyl oxalate is relatively new to the field of conservation, and therefore requires extensive testing to understand its properties and the products of its reaction in calcium carbonate systems before it can be used in conservation treatments. The current study builds on previous testing, to compare the effect of variations in the formulation of diethyl oxalate-based microgrouts bulked with limestone powder, including the effect of application to dry and damp limestone substrates to understand its reaction mechanism, products and performance.