Tomáš Melichar

Study of the Parameters of Lightweight Polymer-Cement Repair Mortars Exposed to High Temperatures

The article examines the research aimed at studying the basic physico-mechanical parameters of polymer-cement repair mortars with a modified composition. The objective of a composition modification was to achieve the parameters characteristic of fire-resistant repair mortars. For research purposes, a lightweight sintered aggregate-based ash body was used along with polymer fibres based on polyolefin. It was suggested to use a few recipes that have been subjected to high temperature stress up to 1200 °C. Subsequently the suitability of the formula composition was verified by determining the essential characteristics visual assessment of the structure, density, compressive strength and flexural strength. The results point to the suitability of the proposed formulas, although this will be verified by setting other essential material characteristics.

Evaluation of the Effect of Crystallization Additives on the Durability of Cement Composites

The paper deals with a comprehensive analysis of the influence of applied crystallization additives on the service life of self-compacting concrete (SCC), specifically when exposed to the effects of chemically aggressive environments. Attention is focused not only on the influence of a crystallization additive on the characteristics of the capillary porous structure of SCC, but mainly on its effects in terms of the long-term service life of self-compacting concrete. The effects of individual types of aggressive environments are evaluated on the basis of a set of physico-mechanical and physico-chemical analyses.

Study of Alternative Raw Materials Parameters for Modification of Cement-Bonded Particleboards Composition

The cement-bonded particle boards can be used among other also with reconstructions of various types of buildings as a part of final surface treatment. The paper deals with partial results of the research focused on optimisation of cement-bonded particle board composition with alternative raw materials. Specifically it is analyzing of basic parameters of the waste originating during processing (modification of surface format and quality) of the boards. Upon results and findings a design of new formulas of cement-bonded particle boards is mentioned further, i.e. the composition modified with above stated waste. The outputs presented in the article form an important initial information source in the solved questions. In view of subsequent phases of the research it is a relatively essential and also it can be said a key phase.

The Evaluation of the Effect of Crystallization Additives on Long Term Durability of Cement Composites

The article deals with the influence of crystallization additives on the life of self-compacting concrete (so-called SCC concrete), which are exposed to chemically aggressive environments. The focus is not only on the effect of the crystallization additive on the characteristics of the capillary-pore structure of SCC concrete, but especially long life durability of self-compacting concrete (two years expozition). The effect of individual types of aggressive environment is assessed on the basis of a set of physico-mechanical and physico-chemical analyzes.

Lightweight Mortar Containing High Amounts of Alternative Raw Materials with Increased Thermal Resistance

The paper researches lightweight mortars based on a high content of alternative materials. 25 – 30% heating plant slag was used in order to modify the matrix. Fly ash agloporite (a lightweight aggregate produced by self-combustion from fly ash) was used as an aggregate. Mortars were exposed to the temperatures up to 1,250° C. Two types of cooling were carried out at 1,000° C; controlled slow (in the furnace) and by shock (in water baths of approximate 18° C). Developed materials were further analyzed by various methods: monitoring changes in an observation furnace, physical–mechanical (to determine strength properties), physical-chemical (phase composition - XRD) and microstructural (SEM).

Polymercement Composites in Environment with Increased Concentration of Sulfate Ions and Extreme Temperatures

Polymer cement matrix based materials were designed within the frame of the research presented in this paper. Resistance of these materials to combination of several adverse factors was observed. Considerable proportion of input materials used were components from alternative material resources. Primary binder was replaced with fly ash and blast furnace slag. Dominant proportion of filling mass was taken up by agloporite – porous aggregate produced by self-baking from fly ash. The focus of the research was assessment of degradation of materials after long-term exposition (up to 90 days) to increased concentration of sulphate ions and high temperatures. Degree of degradation was evaluated on the basis of physico-mechanical and physico-chemical tests combined with microstructural analyses.

The Development of Coating Systems Based on Alkali Activated Slag for Protecting Reinforced Concrete Structures

Theme of the article is the development of coating systems based on alkali activated stag intended for protection of reinforced concrete constructions exposed to chemically aggressive environments. At present mainly polymer based secondary protections are used for this purpose. The coating systems based on alkali activated slag have potential to surpass these generally applied types of secondary protections in many aspects. For instance for constructions exposed to synergic actuation of chemically aggressive environment and increased temperatures. Findings obtained from alkali activated slag coating exposed to selected aggressive environment types for six months are presented in this article.

The Development of Materials Based on Alkali-Activated Fly Ash Designed for Special Applications

The article is involved in the possibility to use activated fly ashes as composite material matrices intended for extreme conditions. In particular, the attention is paid to the development of high temperature resistant composite materials resistant up to high 1200°C. The effects of temperatures on developed materials are monitored not only by the tests of physical and mechanical parameters, but also using physical and chemical analyses. The attention is focussed not only to the matrix composition optimisation but also to the selection of suitable type of aggregates. This complex approach allows developing materials with maximum resistance in particular exploitation conditions.

Volume Stability of Polymer-Silicate Based Materials Exposed to High Temperatures

This paper presents research into analysing the volume stability of composite materials based on a polymer-cement matrix. The attention was paid to the influence of extreme temperatures shocks. Materials of modified composition were gradually exposed to extreme temperatures and then cooled in furnaces. Cooling was carried out by two different ways, i.e. slow and rapid. Emphasis was placed on the aggregate type used – fine lightweight and dense. Also available materials from alternative resources which have positive effect on thermal stability of composites based on silicate matrix were considered.

Effect of Artificial Lightweight Aggregate on Resistance of Polymer Cement Mortars to Extreme Temperatures

This paper presents the results of research focused on the modification of composition of the polymer-cement mortars. The use of these materials is quite wide. The greatest use can be found in the production of reinforced concrete repair materials. Specifically, the article analyzes problems of lightweight aggregate effect on the resistance of polymer-cement mortars to extremely high temperatures. The link is particularly evident with the risk of fire. Attention was given to the two different types of aggregates - from primary raw materials (Liapor) and alternative sources of raw materials (fly ash aggloporite). The study was carried out by the laboratory analyzing the basic material characteristics of prepared samples which were exposed to temperatures up to 1200 ° C.