Markéta Šmidtová

THE EFFECT OF DEGRADATION PROCESSES ON THE SERVICEABILITY OF BUILDING MATERIALS OF HISTORIC BUILDINGS

The article presents an analysis of degradation processes and partial results of an experimental research into materials and structures exposed to the effects of external environments with an emphasis on the effects of moisture and chemical degradation processes on major mechanical properties of sandstone.

Stabilization, Conversation and Strenghthening of Historic Plaster Using Nanofibres

The paper deals with the stabilization, conservation and strengthening of historic plaster fabrics based on nanofibers. As a result of degradation processes, especially of a chemical nature, accompanied by increased humidity of historic masonry, there is a loss of cohesion and a disturbance of the surface finish and plaster. Traditional remediation techniques and methods normally lead to a reduction of diffuse permeability in the multiphase structure and create different expansion properties under the plaster. The undesirable feature of this method is its irreversible character. Currently there are a number of primarily preferred procedures that stabilize the structure of the external finish, yet at the same time preserve the original features of the historical plasters. This paper will list the partial results of the ongoing in-situ and laboratory research applications of fabric based on nanofibers formed by the supporting layer and spinning polymer.

Comparison of the Degree of Consolidation of Historic Plaster Layers by Means of Lime Hydrate Nanosuspensions

Historic masonry is usually coated with multiple plaster layers, exposed to long-term extreme loading (climatic effects, elevated moisture levels, salt crystallization and recrystallization, biological effects, etc.). As a consequence of the above negative cyclic effects, degradation processes are triggered off leading to a loss in plaster cohesion with the substrate masonry and successive falling-off of surface layers. The strengthening and rehabilitation of plasters with degraded binder components, impaired structure, insufficient adhesion of individual layers of plaster to the masonry surface, with elevated salt contents in the pore system and surface crusts represent a demanding task in terms of the stabilization of such degraded plasters and coatings. Consolidation (i.e. enhancement of mechanical characteristics) belongs to the basic objectives of the restoration of historic plasters, its principle is to return binder into the material structure, fill in existing hollow spaces, heal cracks, etc. Degraded lime plasters are strengthened with consolidating agents applied in the form of solutions, e.g. lime water, organosilicates or lime nanosuspensions, etc. The lime nanosuspension is composed of lime hydrate nanoparticles, dispersed in an alcoholic medium. Due to the deposition of calcium carbonate in the degraded material, the bonds are re-strengthened and the material consolidated. The article presents partial results of theoretical and experimental research addressing potential consolidation of historic plaster layers with lime nanosuspensions prepared by the synthesis of Ca(OH)2, which were successively modified and enriched with other components.

NANOTECHNOLOGY IN THE CULTURAL HERITAGE - INFLUENCE OF NANOSPENSIONS ADOPTED BY NANOPARTICLES OF TiO2 FOR CLEANING THE SURFACE OF HISTORICAL PLASTERS

The continuous development of nanostructure and the study of physico chemical processes in the nanometer range lead to new methods that can slow down the degradation processes of a work of art, or even restore damage caused, for example, by an inappropriate restoration process. The use of nanosuspensions based on calcium hydroxide is probably the most widespread application of nanomaterials in heritage care, especially in the field of hardening of lime building materials (plaster, limestone, etc.). In combination with titanium dioxide, it should be a successful suspension in the fight against biological agents, surface contamination or in the protection of UVresistant building materials.

GROUTING METHODS FOR THE REHABILITATION AND REINFORCEMENT OF MASONRY STRUCTURES DAMAGED BY CRACKS

The article sums up the requirements for historic masonry structures whose reinforcement is based on the grouting technology application, the grouting implementation procedure in relation to the extent, type and size of masonry damage. Special focus is put on grouting agents and requirements for their characteristics.

Discoloration of Historic Wood after the Application of Nanotextiles

The article addresses the discoloration of historic wood after application of nanotextiles. The nanofiber fabrics used for experimental testing were made of the PVB polymer and the Paraloid B72 acrylic resin. For the verification of the possibility to increase the biocidal efficiency of historic wood have also been made nanotextile with dopants Ag ant TiO2. Discoloration of historic wood after the application of selected nanotextiles were tested on the wood samples, which were removed from historic building Hájčí Dvůr, Praha 5. The article was written with support from the research project NAKI DF12P01OVV37: Progressive Non-Invasive Methods for the Stabilization, Conservation and Strengthening of Historic Structures and their Parts with Fiber – and Nanofiber – based Composite Materials.

CONTRIBUTION TO THE POTENTIAL OF USING FRP MATERIALS IN THE REHABILITATION AND STABILIZATION OF TIMBERED BUILDINGS

Wooden log, timbered perimeter and interior walls ranked among the most common building constructions used from the Early Middle Ages. In most cases, the local natural resources, i.e. wood, clay, straw and stone, were used for building houses with wooden framing. This article outlines typical defects and failures of timbered houses, “classic” techniques for the rehabilitation of these defects and failures indicating the potential of using composite materials based on highstrength fibres and epoxy resin in the rehabilitation and strengthening of timbered buildings.

DEFECTS AND FAILURES OF JOINTS OF HISTORIC ROOF TRUSSES AND POSSIBILITIES OF USING FRP MATERIALS IN THEIR REHABILITATION AND STABILIZATION

The survey of selected historic roof trusses performed within the NAKI DF12P01OVV037project revealed numerous failures and defects of joints of roof truss elements of historic and listed buildings. Based on the results of the survey, the article outlines potential rehabilitation and reinforcement techniques of joints of roof truss elements in which the most frequent defects and failures were found using composite fabrics based on high-strength carbon fibres and epoxy resin (CFRP).

REHABILITATION OF HISTORIC HALF-TIMBERED WALLS WITH COMPPOSITE MATERIALS BASED ON HIGH-STRENGTH

The major requirements for present day cultural heritage conservation include the minimization of interventions in historic structures, non-invasiveness and, last but not least, reversibility of rehabilitation and strengthening interventions. Due to these requirements, composites based on high-strength fibres and epoxy resin are increasingly applied during the rehabilitation, renovation and strengthening of building structures. The article points out potential applications of these materials in the renovation, rehabilitation and strengthening of half-timbered constructions.

POTENTIAL APPLICATIONS OF TRANSPARENT FABRIC BASED ON NANOFIBRES FOR THE STRENGTHENING OF PLASTERS DECORATED WITH PAINTINGS AND FRESCOES

Nanomaterials have been increasingly used in the construction industry in the last decades. Nanomaterials have been tested in specific applications focusing on the restoration and conservation of heritage buildings, mainly their surfaces. Nanofibre materials represent a separate area within this field of research and their applications in the construction and conservation practice are still very limited. The article summarizes the possibilities of strengthening plasters decorated with wall paintings with nanomaterials.