Ester Helanová

Lightweight Artificial Aggregate Based on Fly Ash for New Rehabilitation Materials

During rehabilitation work are often strict requirements on the use of high quality lightweight materials, including aggregate. Due the constantly increasing social pressure on the optimal use of secondary raw materials is therefore most appropriate to exploit the potential of fly ash as mineral residue from the combustion of ground coal in power plants. Especially filter fly ash has proven to be an adequate substitute for traditional materials in the past. This article deals with the evaluation of physical and mechanical properties of cold-consolidated pellets based on conventional and fluidized fly ash with various cement addition.

Hydrothermal Synthesis of Tobermorite at 170 and 190 °C from Fly Ash and Quartz Sand

Tobermorite is the main mineral which provides to aerated concrete mechanical properties. It is produces during hydrothermal conditions by reacting silicon and calcium oxides. Within this research was evaluated tobermorite formation using high temperature combustion fly ash and quartz sand, as the siliceous raw materials. As a binder was used lime. Emphasis was also placed on the molar ratio of C/S, which is crucial for the formation of tobermorite and was given 0.73 and 1.00. Hydrothermal synthesis was carried out in a laboratory autoclave at temperatures of 170 and 190 °C.

Influence of Gypsum Additive on the Formation of Tobermorite in Autoclaved Aerated Concrete

The quality of the aerated concrete strongly depends on the chemical composition of the raw materials, as well as the process of the hydrothermal reaction during autoclaving. Due to the variable chemical composition of fly ashes, it is necessary to identify the effect of each ion on the formation of the microstructure of aerated concrete. This paper examines the process of formation of tobermorite with the addition of sulphates in various percentage representation. The microstructure of aerated concrete is assessed using SEM images and the mineralogical by means of X-ray analysis.

Effect of Used Binders in Lightweight Plaster Mixtures on their Thermal Insulation Properties

Good thermal insulation properties of the surface structures lead to reduction of heat losses in buildings. This reduces the energy required for heating which is positive fact from the view protection of the environment. The aim of the research intent, which is going at Faculty of Civil Engineering in Brno, is the development of high-quality, thermal insulating plasters using both conventional binders, and alternative binders, whose acquisition-production is in comparison with the technology production of cement less energy intensive. Due to the fact that increasing moisture leads to deterioration of the thermal insulating properties, further research works were devoted to the study of the influence of relative humidity and moisture content on the thermal insulation properties of lightweight plasters, including of the determination of capillary absorption coefficient. This paper describes evaluation of the development of insulating plasters based on lightweight aggregates, using different ratio of cement and lime hydrate and other chemical additives. There are presented results of the study of basic physical and thermal insulating properties, including the study of sorption properties developed lightweight plaster mixtures.

Analyzing of Alternative Raw Materials for Production of Cement-Bonded Particle Boards

The paper presents the results of research aimed at modifying the composition of the cement-bonded particleboards. These materials can be used as a suitable finish surface treatment among others for renovations of not only older buildings. Specifically, a problem of analyzing of selected and actually produced alternative raw materials in connection with previous results and findings. The effect of pretreatment with suitable grinding equipment was tested. Furthermore, it was the use of thermal methods for the quantification of the constituents of the analyzed material. In terms of subsequent modification of the composition of cement-bonded particleboards outputs can be found the outputs stated in the article as essential and beneficial for continuing research. The presented results also provide details of earlier findings made in this area.

Autoclaving Time Influence on Fly Ash Aerated Concrete Compressive Strength and Microstructure

The fly ash aerated concrete is a modern material combining high use value with environmental aspects of its production. It is mainly an utilisation of secondary raw materials with related minimum consumption of natural resources. The resulting properties the aerated concrete product obtains by autoclaving during which a complete line of calcium hydro silicates are formed due to occurring hydrothermal reaction and tobermorite mineral is the most important one. This mineral has a significant influence principally on aerated concrete strength. This article thus verifies the autoclaving time influence on tobermoritic phase developments and to this related compressive strength of the fly ash aerated concrete.

Durability Evaluation of Wood Based Board Materials against Brown-Rot Fungi Effect

The aim of the experiment was to determine the durability of wood based board materials against wood-rot fungi (Serpula lacrymans) effect. The particle boards, oriented strands boards and plywood as the testing materials were chosen. The spruce solid wood as the reference testing material was selected due to the fact that is most common timber species in the Central European region. The testing samples were exposed to wood-rot fungi and in the individual time periods the weight loss (declaring the deterioration process) and mechanical properties (static bending strength and tensile strength perpendicular to the plane of the board) was investigated. It was found that the deterioration of board materials in a very small weight decreases (up to 1.0%) leads to a significant decrease of their strength properties.

Influence of Granulating Equipment on the Quality of Artificial Aggregate

One of the technologies which enables the increase of the use of fly-ash for construction purposes is the production of light cold-hardened artificial aggregate. Balling of fly-ash is possible in two ways – on the granulating plate and by means of cylindrical granulator. This article leads with the evaluation of the quality of grains produced on the granulating plate and on cylinders and, at the same time, it evaluates the suitability of the use of fly-ash from conventional and fluid burning.

Laboratory Determination of Consistency of Grouting Mixes

Designing of grouting mixes for reinforcement of non-cohesive soils has to satisfy demanding needs. Grouting mix has to have good workability, volumetric stability, good penetration capability, sufficient strength and, last but not least, it should not be too expensive. For above-mentioned reasons, clay-cement suspensions seem to be an appropriate candidate, also because they can be topped up with high-temperature fly ash for even higher cost saving. The paper presents results of preliminary tests of consistency of grouting mixes with various proportions of added fly ash and cement. The tests determined particularly liquid limit and viscosity limit with Marsh funnel.