Dita Frankeová

Characteristics of Mortars from Ancient Bridges

Mortars from two medieval bridges (Charles Bridge in Prague and a bridge in Roudnice) and two Roman bridges (Ponte di Augusto in Narni and a bridge in Sardinia) were analysed using various techniques to obtain their chemical and physical characteristics. The analysis of binder quality was based on thermogravimetric analysis, using a methodology which enables the hydraulicity of the mortar to be expressed by the CO2/H2O ratio. The mechanical tests were performed on non-standard mortar specimens. The ratio binder/aggregate was determined dissolving the binder by an acid, and a sieving analysis was applied to the separated aggregate. The material characteristics of mortars from historic bridges were compared with each other, taking into account the requirements for mortar strength according to construction function and degree of exposure.

High-Performance Repair Mortars for Application in Severe Weathering Environments: Frost Resistance Assessment

Frost is one of the main degradation processes affecting historic buildings in cold environments. Lime mortar is particularly sensitive to degradation by freeze-thaw cycles due to its high porosity and low mechanical resistance. The aim of the present research is to assess the frost resistance of seven lime-based mortars to be used in repairs. Mortars with different binder composition and a traditional hydrophobic additive were tested. Specimens with three months of age were subjected to freeze-thaw cycles and the ageing action was evaluated by means of mechanical and physical measurements. Improved durability of lime-based mortars with hydraulic binders and linseed oil additive has been confirmed and the different mortar formulas may be promising for repairs according to specific environmental conditions.

Comparative Tests of Strengthening Effects on Weak Mortars Consolidated with Various Agents

The capacity of various consolidating liquids to strengthen weak mortars is reported in this paper. Commercial products (CaLoSiL IP 15, KSE 100) and liquids prepared in laboratory by dissolving chemicals in water (barium hydroxide, ammonium oxalate, ammonium phosphate) or by dilution more concentrated products (Syton X 30) were used for the experiment. In order to study the influence of the mineralogical composition of the mortar, various sorts of sand were alternatively used in the experiment for the mortar preparation. The efficiency of the treatment was evaluated as mechanical strength change measured on different shape specimens - on tubes for compression strength, on thin plates for tension test and on beams for flexural strength. All the tested consolidation agents showed positive strengthening effect when they were used for consolidation of the poor lime mortar, with the exception of the influence of lime water on the flexural strength. Very different results were achieved on soil-based mortar.

Soils and Earthen Building Materials Used for the Buddhist Temple Complex

ABSTRACT This article presents a comprehensive study of the local soils and historic earthen building materials used in Nako temple complex in Western Himalayas. On-site and laboratory investigations followed a holistic approach to characterize materials and identify historic manufacturing formulas. The interdisciplinary and novel methodology used for analysis of the earthen building materials combine geological, chemical, mineralogical, geotechnical, and mechanical approach. The results presented in this article enable a better understanding of material culture and advance the study of damage and decay processes found in the temple buildings. In addition, a suitable conservation and preservation strategy is presented.