Improving the Behavior of Stone Walls in Heritage Structures Using Enhanced Lime Mortar
The restoration of heritage and historical structures after being exposed to earthquakes and other damages is considered one of the most complex engineering challenges. This complexity arises from the heterogeneous composition of stone structures, which include various elements, making it necessary to conduct precise structural analyses of the main load-bearing components of heritage buildings. The goal is to determine the forces and stresses generated in these elements and ensure their ability to withstand the applied loads.
The restoration of archaeological structures is an essential part of the reconstruction process that Syria will witness in the near future. Since old stone buildings constitute the majority of these structures, their restoration primarily depends on the quality of the mortar used. However, the limited studies on the properties of natural stone and lime mortar, along with the tendency to use cement mortar in many cases, have led to neglecting the negative impact of cement mortar on stone, as well as overlooking the role of bond improvement in enhancing the behavior of stone walls.
In this context, a scientific study was conducted at the Faculty of Architecture at the International University for Science and Technology, aiming to improve the structural properties of lime mortar and study its effect in enhancing the behavior of stone walls, especially multi-leaf walls, under cyclic loads.
Laboratory experiments were carried out on natural limestone to determine its mechanical properties. Fifty mixtures of local lime mortar were prepared using additional materials such as pozzolana, brick, and glass fibers in varying proportions to study the effect of these additives on the mechanical properties of the mortar.
In the second stage, tests were conducted on wall specimens composed of stone and mortar under compression and bending. The experiments included both single-leaf and multi-leaf wall samples to study the role of adding glass fibers in improving wall behavior.
The study was further expanded using a numerical model based on the Finite Element Method (FEM), with nonlinear analysis that considers material nonlinearity. The Abaqus software was used with a micro-model approach, and the computational model was calibrated using experimental results obtained by Abdo, S. (2003).
The study demonstrated a significant improvement in the structural behavior of stone walls, in terms of both stress reduction and increased ductility and energy dissipation capacity under seismic loads when using enhanced lime mortar. The most notable results were as follows:
• An increase in mortar compressive strength to 3.9 MPa with the addition of glass fibers, compared to 1.2 MPa for traditional mortar.
• Improved ability of stone walls with reinforced mortar to resist horizontal forces, as the enhanced mortar strengthened shear resistance by improving adhesion between stones and mortar.
• A major effect of glass fibers in reducing cracking, as they helped minimize shrinkage and the development of microcracks, contributing to better stress distribution and preventing wall degradation.
• Improved behavior of stone walls under cyclic loading, including reduced risk of collapse during earthquakes.
The study highlights the importance of using enhanced lime mortar as an effective solution to improve the behavior of stone walls in heritage buildings, especially in earthquake-prone areas.
It indicates the necessity of adopting enhanced lime mortar in future restoration projects of heritage buildings in Syria, as it provides better resistance to cyclic loads and contributes to preserving architectural heritage.
The study emphasizes the importance of scientifically based structural reinforcement of historical buildings and providing sustainable solutions for restoring old structures.
The findings proved that enhanced lime mortar represents an effective option for restoring heritage structures and improving the behavior of stone walls under various loads, especially under seismic conditions. The results achieved reflect significant progress in the field of structural engineering and architectural restoration, paving the way for developing new restoration techniques that enhance the sustainability of heritage buildings and preserve them for future generations.
