The effect of linseed oil on the properties of lime-based restoration mortars

The traditional lime mortar is composed of hydrated lime, sand and water. Besides these constituents it may also contain additives aiming to modify fresh mortar´s properties and/or to improve hardened mortar´s strength and durability. Already in the first civilizations various additives were used to enhance mortar´s quality, among the organic additives, linseed oil was one of the most common. From literature we know that it was used already in Roman period to reduce water permeability of a mortar, but the mechanism and the technology, e.g. effects of different dosages, are not clearly explained. There are only few works studying the effect of oil experimentally. Knowing the function of oil in historical mortars is important for designing a new compatible repair mortar. Moreover, linseed oil addition could increase the sometimes insufficient durability of lime-based mortars used for reparation and it could be a natural alternative to synthetic additives. In the present study, the effect of linseed oil on the properties of six various lime-based mortars has been studied. Mortars´ compositions have been selected with respect to composition of historical mortars, but also mortars used in a modern restoration practise have been tested. Oil was added in two different concentrations – 1% and 3% by the weight of binder. The addition of 1% of linseed oil has proved to have positive effect on mortars´ properties. It improves mechanical characteristics and limits water absorption into mortar without affecting significantly the total open porosity or decreasing the degree of carbonation. On the other hand, the 3% addition of linseed oil is making mortar to be almost hydrophobic, but it markedly decreases mortars´ strength. However, all types of tested lime-based mortars with the oil addition showed significantly decreased water and salt solution absorption by capillary rise. Addition of oil into mortars is also decreasing the proportion of pores which are easily accessible to water. Furthermore, mortars with linseed oil showed significantly improved resistance to salt crystallization and freeze-thaw cycles. On the base of the obtained results, the addition of 1% of linseed oil can be taken into consideration in the design of mortars meant to repair or replace historic mortars.

Sustainable inorganic Binders and Their Applications in Building Engineering: A Green Alternative to Ordinary Portland Cement

In the last decades, the building materials and construction industry has been contributing to a great extent to generate a high impact on our environment. As it has been considered one of the key areas in which to operate to significantly reduce our footprint on environment, there has been widespread belief that particular attention now has to be paid and specific measures have to be taken to limit the use of non-renewable resources.The aim of this thesis is therefore to study and evaluate sustainable alternatives to commonly used building materials, mainly based on ordinary Portland Cement, and find a supportable path to reduce CO2 emissions and promote the re-use of waste materials. More specifically, this research explores different solutions for replacing cementitious binders in distinct application fields, particularly where special and more restricting requirements are needed, such as restoration and conservation of architectural heritage. Emphasis was thus placed on aspects and implications more closely related to the concept of non-invasivity and environmental sustainability. A first part of the research was addressed to the study and development of sustainable inorganic matrices, based on lime putty, for the pre-impregnation and on-site binding of continuous carbon fiber fabrics for structural rehabilitation and heritage restoration. Moreover, with the aim to further limit the exploitation of non-renewable resources, the synthesis of chemically activated silico-aluminate materials, as metakaolin, ladle slag or fly ash, was thus successfully achieved. New sustainable binders were hence proposed as novel building materials, suitable to be used as primary component for construction and repair mortars, as bulk materials in high-temperature applications or as matrices for high-toughness fiber reinforced composites.