Determination of Characteristics and Structural Behavior of Hydraulic Mortars Produced with Slaked Lime or Quicklime to be used in the Restoration of Historical Buildings

Project No: 221M105

Supported by: Scientific and Technical Research Council of Turkey (TÜBİTAK)

Director: Assist.Prof.Dr. Elif Uğurlu Sağın

Researchers: Assist.Prof.Dr. Korhan Deniz Dalgıç, Inst.Dr. Kerem Şerifaki

Adviser: Prof.Dr. Hasan Böke

Scholars: Res.Assist. Tuğçe Işık, Güngör Muhammed Serin

Project Budget: 412.522 TL

Project Term: 15.11.2021-15.11.2023


Historical hydraulic lime mortars had been prepared by mixing air lime with natural pozzolanic aggregates or artificial pozzolanic aggregates. Two methods based on the use of slaked lime or quicklime had been used during their production. In the first method, lime was slaked before the mortar production, then mixed with aggregates and water. In the second method, quicklime and aggregates were mixed and water was added afterwards. This method was also known as “hot lime mix” due to the strong heat given off during slaking. Although there are various recommendations about lime mortars in historical sources, there is no definite information about the method used during their manufacturing process. In addition, the effects of production methods on physical, microstructural and hydraulic properties of mortars as well as their structural behavior have not been clearly revealed.

The aim of this study is to produce hydraulic lime mortars compatible with historical lime mortars which could be used safely for the restoration of historical structures. New mortars will be produced in laboratory conditions using two different production techniques stated in the historical sources. Characteristics of mortars, their behavior in the structural units and the required qualities of compatible repair mortars will be determined. The study will also shed light on the retrospective determination of original production methods of historical lime mortars.

The method will be consisted of preparation of mortars, determination of their physical, microstructural, hydraulic and mechanical properties, chemical and mineralogical compositions; determination of effects of mortar properties on the structural behavior of brick wall parts, and evaluation of the obtained data. The mortar samples will be prepared by two different methods based on the use of slaked lime or quicklime, with lime/aggregate ratios of 1/3, 1/2 and 2/3 by weight which are most frequently determined ratios in historical mortars. It is aimed to produce hydraulic mortars as a result of both methods and lime/aggregate ratios. Raw materials of mortars were selected as: 1. Hydraulic lime and sand aggregates, 2. Air lime and pumice as pozzolanic aggregates.

9 types of mortars will be produced according to these variations. In each interval, physical, microstructural, mechanical properties, chemical and mineralogical compositions and carbonation degrees of mortars will be determined via standard test methods, SEM-EDS, XRD, XRF, MTC and MIP. At the end of 12 months, hydraulic properties will be determined via TGA. Structural behavior of mortars will be examined by pressure and shear tests performed on prism and triplet samples (brick wall pieces).

Production of mortar samples and standard test methods will be carried out in IZTECH Materials Conservation Laboratory; whereas production of prism and triplet samples will be carried out in IZTECH Structural Laboratory. Sensitivity analysis will be performed using Spearman Method to reveal the effective parameters in the production of prism and triplet samples. SEM-EDS, XRD, XRF, TGA and MTM analyses will be performed at IZTECH Center for Materials Research. MIP analysis will be performed at METU Mer-Lab.

Consequently, properties and structural behaviors of hydraulic mortars produced with same raw materials and compositions in two different techniques will be determined and their similar and different sides will be revealed. By associating the mortar production parameters with the compressive strength, graphic charts that can potentially be used in mortar mix design will be created. Strength design models will be proposed for prism and triplet specimens, taking into account the unique aspects of the study, such as the difference in production method. These mortars which will be produced by using the natural resources of our country, will contribute the conservation of historical buildings and the transfer of their original materials to future generations.