Solid State Phenomena Vol. 244

Abstract: Waste valorisation in production of building materials can be improved by their modification using some treatment technologies. Subsequently, products prepared using these optimized raw materials can show better or even new properties. Utilisation of construction and demolition waste (C&DW) for production of building materials is discussed for a longer time world-wide, whether in the form of coarse aggregates or in the fine-grain form as a micro-filler or as a binder. Both of these forms show specific problems have to be solved for increasing the quantities consumed. Fine-grain form can be obtained by techniques like crushing, grinding and sorting as well as by their combinations.This article is aimed on the utilization of specific portion of fine-grain C&DW (ceramics, glass and concrete) for production of concrete mixes of higher fluidity. C&DW were modified by specific process (defined method of crushing followed by sorting of particles under 250 μm). This material was expected as a micro-filler - substitution of natural aggregate (NA) in 0/4 fraction to the extent possible, that the rules allow. Using relevant calculations, 40% dosage was found as complying with standard limit for the maximum content (600 kg.m^-3) of particles of less than 250 μm in whole mixture including the relative share of cement and NA. In accordance with these limiting factors, standard recipes were designed. Amount of water, as well as dosage of plasticizer was adjusted during mixing in order to keep the water/cement ratio (max. 0.6) and flow class F5 – F6.Resulting water consumption and dosage of plasticizer are discussed in the terms of influence of tested C&DW on the consistency and bleeding of concrete. Generally positive effect of fine-grain form of brick, glass and concrete was found compared to the reference concrete not containing those additive fine particles.

Abstract: This article presents the results of an experimental research dealing with the use of steel slag as a partial substitute for natural aggregates in the production of concrete composite. Comparative mixture based on natural aggregates was prepared from the fractions of 0/4, 4/8 and 8/16 mm, which were represented in the volume ratio of 40:30:30. During the experimental research, natural aggregates with the fractions of 4/8 mm, 8/16 mm were replaced with steel slag of the same faction. We have tested the input properties of natural aggregates and steel slag for the designed experimental mixtures (grain size, density, specific weight, powder density, absorption capacity, resistance to crushing, shape index). In case of concrete mixture prepared according to the experimental recipes, we have monitored the following characteristics: density of fresh concrete mixture, consistency of concrete mixture, strength characteristics - cube strength after 3, 7, 14, 21, 28 and 90 days, prism strength after 28 days. The research has discovered that substitution of natural aggregates with steel slag of the same fraction in concrete mixture is possible, without significantly affecting the strength properties of the concrete based on steel slag in comparison with the concrete based on natural aggregates.

Abstract: The use of separately ground blast-furnace slag, added at the mixer as a replacement for a portion of the Portland cement, has gained increasing acceptance in recent years. The effects of partial replacement of Portland cement with ground slag on the properties of hardened concrete have been extensively investigated and reported. Both laboratory testing and field experience have shown that properly proportioned slag-Portland cement concretes have the improved resistance to sulfates and seawater compared to regular Portland mixes. The paper is focused on the effects of sulfur-oxidizing bacteria Acidithiobacillus thiooxidans on concrete mixtures with addition of ground granulated blast furnace slag compared to mixture without any additives. The concrete specimens with 65 and 75 % wt. addition of antimicrobial activated granulated blast furnace slag as durability increasing factor as well as without any addition were investigated in laboratory during the nine 7-day cycles. A laboratory study was conducted to comparison the performance of concrete samples in terms of a concrete deterioration influenced by the leaching of calcium and silicon compounds from the cement matrix. The changes in the elemental concentrations of calcium and silicon ions in leachates were measured by using X – ray fluorescence method. The pH values were measured and evaluated after each cycle. The concrete specimen with 65 % wt. addition of antimicrobial activated granulated blast furnace slag was found to have the best leaching performance of calcium ions than other samples. The final concentration of Si ions in leachate of concrete specimen with 75 % wt. addition of antimicrobial activated granulated blast furnace slag affected with bacteria Acidithiobacillus thiooxidans (4.614 mg/g of concrete sample) was observed to be 1.263 times lower than reference sample without any additives. The higher resistance of concrete samples with the addition of antimicrobial activated granulated blast furnace slag to the aggressive environment was confirmed.

Abstract: Alkali-activated systems, formed by the alkaline activation are inorganic materials characterized by the potential of ecological use. The objective of experiment was to investigate the influence of different activators on selected properties of alkali-activated systems based on granulated blast furnace slag. At the beginning of the experiment, 21 different samples prepared of 12 types of activators were tested to the basic properties. Then, selected samples with the best potencial to use were tested to compressive and flexural strength, frost resistance and surface resistance to chemical de-icing substances. The initial setting time achieved 25 - 95 minutes and final setting time achieved 30 - 105 minutes, compressive strengths were in the range 40 - 100MPa, frost resistance and resistance of surface to water and defrosting chemicals were confirmed.

Abstract: This article is aimed on the study of glass bottle cullet influence on the compressive and flexural strength development of products prepared as the partial natural aggregate replacement by crushed glass waste. For this study, eight different mixtures containing coloured glass cullet as a full replacement of natural aggregate fractions 0/4, 4/8 and 8/16 mm and two comparative mixtures were prepared. In four of these mixtures, 25% of Portland cement were replaced by coal fly ash. After 7, 28 and 90 days of hardening, samples were tested on flexural strength and compression strength. Results showed, that specimens containing full replacement of fraction 8/16 mm of glass cullet reached the highest compressive strength 43.32 MPa corresponding to concrete strength class C 30/37. Partial cement replacement by coal fly ash leads to low compressive strength after 7, 28 and 90 days of curing. Use of coloured glass bottle cullet in concrete should not have negative impact on the strength characteristics of hardened concrete and should have positive effects for preparing quality fair-faced concrete surfaces.

Abstract: Fly ash, representing the fine particulate matter, can be widely used in concrete production in order to improve the concrete properties and its environmental performance. The paper is aimed at applying a statistical approach to evaluate the results of the chemical sulphate corrosion of cement composites with and without fly ash addition. Two aggressive media simulating a sulphate corrosion: 0.5 wt.% solution of H₂SO₄ and 0.5 wt.% solution of Al₂(SO₄)₃ were used. The deterioration process was evaluated by dissolution of the basic components of cement composites due to the aggressive media ́ exposure. The concentrations of dissolved Ca, Si, Al, Fe, Mn and Cu ions in leachates were measured and used as input data in a correlation analysis.Significant and up to very high correlation coefficients have been calculated for all analysed ions leachability excepting cuprum. The findings revealed the similar leaching mechanisms of analysed ions from the concrete samples with 5 and 10 wt. % of fly ash addition. The addition of coal fly ash was not definitely confirmed to increase the environmental resistance of concrete samples in terms of calcium and silicon leaching.

Abstract: This paper investigates the possibility of application of copper slag as a waste byproduct from metallurgical factory Krompachy (Slovakia Republic) as a fine aggregate in concrete up to 40-50% replacement of natural filler. Results of these studies confirmed that it is possible to produce concrete with a mean compressive strength of greater 50 MPa at 28 days hardening without any special additivies. Testing of mechanical properties of concrete samples was provided on the durability point of view up to 360 days. It can be concluded from the results, that use of copper slag as fine aggregate in concrete is technically viable for road construction engineering and have some economical benefits as soon as.

Abstract: This article deals with the presentation of modern applications for processing powdered, primarily hazardous, waste to an agglomeration form appropriate for subsequent processing by classical methods, for example in the construction, automotive and consumer goods industries. The aim of the research work was to set appropriate operating conditions in order to appreciate currently non-processable wastes resulting from the intensive production of often extremely expensive materials. Technologies which enable returning powder waste back into the primary production cycle were developed and experimentally tested, thus saving raw material resources. When necessary for the fixing of fine airborne particles with a problematic compacting curve (hard to compress, repulsive due to the surface charge) extrusion processes using a patented technology enabling controlled modification of shear forces in the extrusion zone were successfully applied. A new type of axial extruder allows the elimination of the liquid phase and as a result prevents the clogging of the extrusion chamber. In the case of need for granulation of sensitive materials (for example pharmaceuticals not allowing the addition of any kind of agglomerating fluid or reacting strongly in the contact of the two phases), a process of compaction between rolls with different profiled surface was successfully applied. The developed high technologies and the resulting products thus represent a major contribution to environmental protection in the context of not only the work but also the communal environment.

Abstract: The active mining of the Mátraszentimre (Hungary) underground base-metal mine was halted in 1985. So far enormous research and efforts have been taken for the final closure of the mine. The technology of fly-ash based hydraulic backfilling was selected. About 95 000 tons of fly-ash backfilling is necessary to close the mine. A suitable technology have been developed, installed and put into operation. So far about 14 400 tons fly ash have been backfilled.This paper summarizes the main results and elements of the process engineering part of this work. The pozzolanic activity of fly-ash from the Mátra Power Station was examined in order to develop a new hydraulic binder with the addition of lime. As results of the different examinations it had been decided that the backfilling material should be lignite fly-ash from the tailings pond of the nearby Mátra Power Plant. The fly-ash hydraulic transport system of the Mátra Power Station was designed by our institute back in 1998. This system is still operating and now serving the material for backfilling. The knowledge of designing the power station pipeline system was utilized at designing the hydraulic backfilling system. The main technical parameters of the solid – liquid pipe flow were designed based on the Tarján – Faitli: coarse mixture flow in fine suspension flow model then and now as well. The design covered many other aspects of the task such as material characterization and mixing, settling behavior of the backfill, dewatering and mechanical properties of the backfill, water permeability and so on...

Abstract: Fly ash is a well utilizable secondary raw material for the production of alkali activated construction materials. It is a significant alumina-silicates source suitable for the chemical reaction resulting in hardened composites. Physical and chemical properties of fly ashes as a co-product of coal burning mainly depend on characteristics of coal, burning temperature and combustion conditions. High variability of the properties of fly ash causes an uncertainty in the properties of alkali activated mortars. Time behaviour of the composition of the fly ash produced in a heating plant located in Košice, Slovakia as well as leaching behaviour of both alumina and silica from particular batches during one-year period was documented. Leaching tests were carried out using the distilled water and alkali solutions with three different concentrations. Both compressive and tensile strengths of alkali activated mortars were measured, and the correlation between the mechanical properties of hardened mortars and the chemical composition of fly ashes as well as their leaching characteristics was investigated.