Evaluation of lime mortars for the repair of historic buildings

Abstract

The repair and rehabilitation of old historic structures involve a complex interaction of existing and new elements. Several difficulties are encountered by researchers and design engineers in this effort. Engineering judgment, perception, and experience have been used in many cases due to the lack of technical guidelines in a worldwide context. Consequently, a research studying different restoration mortars became a necessity. To fulfil this need, this research attempts to evaluate the performance of some of the currently used mortars and develop new ones. Several tests were conducted on lime based mortars using white cement, gypsum, lignin sulfonate, and silica fume that are used to enhance the mortars' performance. These mortars were tested for compressive, tensile, and shear strengths at 7, 28, and 56 days from mixing. As a durability test, weight loss of mortar cubes subjected to wetting and drying cycles was measured. In addition, models of wall prisms were built using these mortars and tested under in-plan compressive loads to study the composite structural behaviour and bonding of stones and mortars. Based on the results of these tests, it was found that lime based mortars prepared using silica fume yielded the highest compressive, tensile, and shear strength. On the other hand, lime based mortars prepared using lignin sulfonate have attained the best results concerning wetting and drying cycles and the highest load capacity for the model wall, which resembled structural behaviour and bonding.

Experimental evaluation of stone masonry walls with lime based mortar under vertical loads

“…The average of indirect splitting tension test of three specimens is used to determine the tensile strength of the used limestone blocks as 1.3 N/mm 2 . In a previous comprehensive study by the first author, different types of lime based mortar for restoration of historical building were studied in detailed where the advantages and limitations were identified [9]. In this paper, three types of lime based mortar are developed and tested.…”

Response of Organic Lime Mortars to Thermal and Electrical Shocks Due to Lightning Strikes

“…Till the 19th century, lime-based mortars became predominant in construction work; with the advent of Portland cement, the use of lime mortar slowly disappeared from the construction, due to its inferior properties relative to cement. However, cement is incompatible with ancient materials, thus necessitating the design and the optimization of appropriate repair materials for the conservation and restoration of heritage buildings [17][18][19][20]. In India it has been a common practice to add organics to lime; this feature has been utilized to improve the hardening properties of lime mortars [16,21].…”

The Influence of Water/Binder Ratio on the Mechanical Properties of Lime-Based Mortars with White Portland Cement

“…Lime and alumina silicates in cement develop crystalline substances during hydration which improves the strength of mortar and its adhesion to the brick and stone. [11]. Nevertheless, as conservation of historic structures is quite complex and its accomplishment lies in the adequate interaction between the inherited structure and a new one, the rapid diffusion of PC was stopped because of its incompatibility with the original structure.…”

“…Literature review regarding the issue of adding PC to lime mortars shows that there are no clear recommendations. Some studies promote the use of PC to a significant extent of a minimum of 20% of lime weight, justifying it by high initial strengths [11,19]. Other studies promote the use of PC in smaller amounts, referencing unchanged water absorption with regard to lime mortars with no additives [31], significant reduction of porosity due to the increase of cement content [29], or loss of elastoplastic behaviour or mortar mixtures, which makes them able to adapt to movements and deformation under critical stress in the masonry [32].…”