Nikol Žižková

Effect of Humidity on the Properties of Cement Mortars with a Crystalline Additive

The paper focuses on examining the properties of mortars in which secondary crystallization (crystalline additive) was used. Laboratory tests have found that the effect of secondary crystallization is influenced by conditions in which specimens have been stored during the first 28 days. The investigation focused on the physical-mechanical properties and microstructure of mortar specimens containing a crystalline additive and polypropylene fibres stored at different levels of humidity for 28 days. The influence of crystalline additive on strength was studied as well and the results show that crystalline additives improves the 28-day strength of the mortars.

Influence of a Crystalline Additive on the Porosity of Cement Mortars

The pore structure of a material radically infuences its properties, such as strength, freeze-thaw resistance, capillarity or resistance to elevated temperatures. The character of the pore structure is also limiting for the intrusion of aggressive oxides into the material, which affects its service life. The paper describes how a crystalline additive influences the pore structure of cement mortars. It describes the effect of secondary crystallisation and the influence of the additon of PP fibers on the apparent porosity and the internal structure of the mortar. It also discusses the influence of aggressive conditions on the mortar’s pore structure.

Durability of Cement Based Mortars Containing Crystalline Additives

The paper focuses on the study of the durability of cement mortars made with secondary crystallization additives. It investigates the influence of the crystalline additives on the degradation process of cement mortars exposed to gaseous CO2 and freezing cycles. The specimens with were tested for compressive and flexural strength at the following ages and after being treated by the following curing techniques: 28 days, 180 days and 25 freezing cycles, 28 days and 180 days in gaseous CO2. In order to explain the obtained results and to gain new information about the microstructure of the cement mortars being studied, the SEM sampling and RDA analysis were performed. The research results confirm an improvement in the resistance of cement based mortars using crystalline additives against cyclic freezing as well as gaseous CO2. An important parameter that influences the effectiveness of the crystalline additive is the curing conditions during the first 28 days of ageing.

Polymer-Modified Mortars with Increased Amount of C-S-H Phase

The article focuses on the observation of the quality of polymer-modified mortars, where through the use of appropriate types of by-products the amount of C-S-H phase registered an increase. Specifically, it was waste shale and waste diatomaceous earth because these two by-products displayed pozzolana reaction. Tests were performed which showed that the increased content of C-S-H phase contributes to the improvement in monitored properties, particularly increase in the values of adhesiveness.

Possibilities of Hydrophobization of Thermo-Insulating Materials Based on Natural Resources

Current times emphasize utilization of new and promising building materials with no negative environmental impact, for reasonable price and with excellent end-use properties. Insulation materials based on natural fibers represent a good alternative for current standardly used insulation materials like foamed plastic materials and mineral wool. Input materials for such industrial insulation materials are particularly crude oil and non-renewable natural resources (moreover, manufacture of these insulation materials consumes high amount of energy). From this point of view, natural insulation materials are more advantageous, because their manufacture uses easily renewable materials resources, like fibers from agriculture (flax, technical hemp). However, these materials have two disadvantages higher sensitivity to humidity (higher water absorbing capacity and hygroscopic nature) and worse reaction to fire. The paper deals with selection of appropriate hydrophobic agent preventing high sensitivity to humidity of developed natural materials and monitoring of moisture content after application of hydrophobized materials within the frame of the ETICS system.

Development of Materials Based on Flax for Thermal Insulation and Thermal Rehabilitation of Structures

Thermal restoration of building constructions presents a complex of measures during renovation and life prolongation of buildings. It is a solution including restoration of bearing parts of the construction, solutions of moisture questions and the thermal insulation and new surface treatments of the construction. After application of the thermal insulation total energy intensity for heating and cooling is reduced and the thermal comfort inside insulated object is improved. Nowadays at application of thermal insulating systems a huge amount of insulants produced from non-renewable materials (EPS, PUR) is needed or the production of these is energy demanding (rock wool). Some of them, namely foam-plastic insulating materials are not compatible with original walling materials and after its application the diffusion flow is frequently limited in direction to exterior. The paper describes possibilities of production of insulants from flax waste and use of such insulating materials in the field of exterior heat insulating materials for existing objects.

Possibilities of Using Waste Diatomaceous Earth for Polymer-Modified Mortar

The paper focuses on results obtained in solving the research and development project of lightweight Polymer-Modified Mortars (PMM). With regard to the currently on-going repairs and reconstructions of panel houses in the Czech Republic approaching the end of their expected lifetime, attention is paid to PMM (Polymer-Modified Mortars) intended for surface treatment such as screed or adhesive materials. For the design of adhesive and screeding substances (recommended for ETICS – External Thermal Insulation Composite Systems) use the alternative raw material sources, waste diatomaceous earth is used from the production at the firm LB MINERALS, s.r.o. (Czech Republic). This raw material is delivered in moist, therefore, it is necessary to dry it before the use and consequently mill it so to be able to replace milled limestone by the modified diatomaceous earth in the original formula.

Polymer-Modified Mortars for Surface Treatment with the Utilization of Waste Polystyrene

The article is focused on the observation of usable possibilities of waste polystyrene that is created during foundry production and that could be used for production of cellular construction material. Thanks to its granulometry this kind of waste polystyrene is very suitable for use in the fine-soft Polymer-Modified Mortars (PMM), for example in the paste and gluing materials determined for ETICS (External Thermal Insulation Composite Systems). The mixtures for waste polystyrene application feature the required cellular light property, they conform to the requirements on the solidity and adhesiveness and conform also to the tension tests for the reinforcing layer.