Rostislav Drochytka

PMM for Surface Treatment of Concrete with the Utilization of By-Products

The disadvantage of PMMs (polymer-modified mortars) that are currently on the market is the utilization of expensive polymer additives and also the cost of the other components. One of the possibilities how to decrease this price is the effective utilization of waste materials which are very inexpensive in spite of their good properties. The combinations of different degree in polymer adhesiveness and waste secondary raw materials - fly ash - are experimentally verified in the paper. The use of fly ash in adhesive materials for ceramic tiles is limited by unsatisfactory initial adhesiveness to sintered ceramic sherd as a result of a running pozzolanic reaction that lowers the efficiency of polymer additives. On the other hand, the use of adhesive and backfill coating materials for gluing ETICS board insulation materials has brought very good results.

Use of emanation thermal analysis to characterize microstructure development during Portland cement hydration

Portland cement hydration has been investigated by emanation thermal analysis (ETA), based on the application of radon atoms as radioactive indicators. This method enabled us to characterize continuously changes in the microstructure of the cement paste at selected temperatures. The numerical simulation of time dependences of the emanating rate during cement hydration was carried out. An agreement between the mathematical model and experimental results of the ETA was obtained.

Evaluation of Degradation of Concrete Exposed to High Temperature by Means of Ultrasonic Pulse Method

Ultrasonic pulse method is a non-destructive testing method used for testing materials. For concrete, it is used mostly for determination of dynamic elasticity modulus, compressive strength, homogeneity, to determine depth of cracks or as a supportive method for testing frost resistance. Applicability of using ultrasonic pulse method for evaluation of degradation of concrete exposed to high temperature was proved. This method is unambiguously utilizable for rationalization of experimental work focused on optimization of composition of concrete resistant to high temperatures. Ultrasonic pulse method can be also used for mapping the degree of degradation of concrete elements and structures, which can be measured by means of direct sounding. Appropriateness of the use of ultrasonic pulse method for evaluation of degradation of concrete exposed to high temperature was proved. This method is unambiguously applicable for rationalization of experimental work focused on optimization of composition of concrete resistant to high temperatures. Ultrasonic pulse method can be also used for mapping degree of degradation of concrete elements and structures, which can be measured by means of direct sounding.

Cement Based Material with Crystal-Growth Ability under Long Term Aggressive Medium Impact

This article describes test and results of long term effect by sulphate environment on new designed crystalline technology based material with fly-ash as partly cement substituent. At this article are presented results of new developed modification, which was the most effective and suitable for further commercial production during long term physical and mechanical tastings. Main aim of the experiment was to analyze ability of this new material to develop crystalline structure in capillary system and proof effectiveness of new developed crystalline structure in concrete pore system affected by long term sulfur medium attack.

Evaluation of FRP/wood adhesively bonded epoxy joints on environmental exposures

This article describes the evaluation of the durability of joints composed of wood adherends with a bonded layer of fibre-reinforced polymer (FRP) fabric. Carbon and glass fibres in an epoxy matrix were studied. The main purpose of FRP usage with timber in the construction industry is generally to improve the stiffness/strength of reinforced members without any influence on their service-life or any environmental impact. From the perspective of the timber reinforcement process, optimal dimensional stability during moisture changes in wood should be one of the most important criteria for such joints. Therefore, FRP/wood joints were evaluated with regard to the influence of real external environmental conditions on the bondline over a period of 40 months. During exposure to these conditions, specimen failures and defects were continuously visually evaluated. The decisive factor in this evaluation was bond integrity, verified by the tensile shear strength of the FRP/wood joint. After the experimental study, it was noted that the first 20 months have a significant effect on bondline failure occurrences, which involve decreases in tensile shear strength. In the next 20 months, the FRP/wood bondlines resist other severe hygrothermal stresses without significant strength decreases. An additional observed parameter was the percentage of wood failure in the bonded area of single lap joints, which characterises the mode of failure of the bonded joint. To determine the influence of ageing on adhesive due to ultraviolet radiation and varying temperature, infrared absorption spectroscopy analysis was performed to reveal changes in the macromolecular structure of the epoxy adhesive. Findings showed that UV radiation had a significant influence on the degradation of the adhesive structure.

Experimental Testing of Hydroinsulating Injection Screens

One of the most widespread method of redevelopment of wet masonry is additional creating of hydroinsulating screen in the material. This method has many advantages. The biggest advantage is fact, that building can be repaired from inside without damaging its statics and saving it from being demolished, thus sparing the environment. In comparison to other procedures its application is quick, easy and has excellent final efficiency. Main object of this article is testing of application and total functionality of individual screens in masonry.

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.

Development of a new reclamation material by hazardous waste solidification/stabilization

This paper deals with the possibility of hazardous waste solidification/stabilization (S/S) using a secondary raw material – fly ash from fluidized bed combustion – in order to find and verify a suitable S/S formula and an appropriate way to ensure that the properties of the S/S product will allow its further use in civil engineering as a reclamation material. The aim of this paper is to examine the properties of the S/S product and to assess its impact on the environment. Laboratory testing was focused on screening those properties that may adversely affect the environment during the use of the product on the ground surface. During laboratory testing the S/S product’s properties were verified using leaching tests, unconfined strength testing, ecotoxicological tests and the determination of pollutant content in dry matter. This paper also considers the two-year durability of the S/S product’s properties in order to verify the short-term durability of the S/S matrix.

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.

Utilization of Fly Ash in High Performance Floor Screed Based on Cement and its Influence on Physical Mechanical Properties

This paper deals with the evaluation of a partial replacement of cement by Czech fly ash in high strength floor screed in dosage of 10, 20, 30 and 40% and the assessment of the physical-mechanical properties such as compressive strength, water absorption and bulk density. Used fly ashes are from power plants Počerady, Opatovice and Tušimice. The experimental study showed that the use of Czech fly ash improves the compressive strength. The bulk density decreases and therefore water absorption increases. Reference samples become clearly the lowest compressive strength at age of 28 days (fc28). A significant increase in compressive strength (fc28) was observed in case of mix design with addition of 10% and 20% of fly ash Tušimice (10%ETU, 20%ETU) and 20% and 30% of fly ash Počerady (20%EPC, 30%EPC). The addition of 20% of fly ash Počerady (20%EPC) has noticeable influence on short-term compressive strength (measured at the age of 24 hours).