Ústav technologie stavebních hmot a dílců
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- ItemParameters of back filling material prepared from mine tailing, fly ash, and mine water(Czech Technical University in Prague, 2024-05-16) Dvořák, Karel; Jančíková, AndreaThe article investigates the influence of mine tailing, fly ash, and mine water on strengthparameters as mine paste filling material performing the strength tests on different recipes of mortarmixes with individual types of fillers and wastewater from extraction of mine tailings. Recipe is preparedin proportions corresponding to the standard mortar and compared with a reference recipe accordingto the fresh mortar consistency test using a shaking table according to ČSN EN 1015-3. Resultingmeasured values on40×40×160mm solids samples for which the evaluation of the volume weight wascarried out in the range of 2, 7, 14, 28, 56 and 90 days according to EN 1015-10 (722400). The resultsshowed that that it is possible to prepare relatively fluid mixtures with extremely low binder dosage.And not only the water coefficient but also the granulometry of the raw material plays an importantrole in the long-term strengths of samples.
- ItemEffect of preparation process on purity of tricalcium aluminate(Czech Technical University in Prague, 2024-05-18) Ravaszová, Simona; Dvořák, Karel; Jančíková, AndreaIn the realm of cement production, traditional fuels are steadily giving way to alternative sources. While this shift yields economic and ecological advantages, it introduces notable technological challenges. Specifically, there is an escalation in certain chemical elements, leading to variability in the mineralogical composition. This variability is subsequently manifested in the characteristics of Portland clinker. It becomes imperative, therefore, to synthesize pure clinker minerals. This synthesis is essential for both understanding their behavior in industrially manufactured cement and creating analytical standards for mineral identification through XRD. The primary focus of the research is on the production of pure tricalcium aluminate, a key clinker mineral, within laboratory conditions. A direct laboratory methodology involving solid-phase synthesis is used. The investigation meticulously tracks the impact of homogenizing the raw material mixture on the resultant mineral’s purity. To achieve this, a high-speed Pulverisette 6 planetary mill is utilized along with two types of grinding bodies. A corundum grinding capsule with corundum grinding bodies is employed to prevent contamination by foreign ions. Simultaneously, a highly efficient steel grinding capsule with steel grinding bodies is utilized. The raw material mixture is then subjected to sintering at six different temperatures ranging from 1 200 to 1 450 °C, and the purity of the produced mineral is quantified using Rietveld analysis.
- ItemProduction of concrete pavements using mixed cements(České vysoké učení technické, 2024-05-18) Šperling, Petr; Hela, RudolfThis paper discusses the possibility of assessing the k-value of power plant fly ash using durability. Compressive strengths, activity indices, pressure water seepage depth and carbonation depth were determined for cement mortars with 10, 20 and 30 % cement replacement by fly ash for ages of 7, 28 and 60 days. The k-values for each cement substitute were determined for each age using the relationship between water/cement ratio and compressive strength. Using the results of the depth of pressurized water seepage and depth of carbonation, the determined k-values were assessed and k-values that are safe for use of power plant fly ash in aggressive XC and XD environments were determined.
- ItemDevelopment of Hydration Temperatures on Cement Pastes(Czech Technical University in Prague, 2024-05-13) Meruňka, Milan; Šperling, Petr; Hela, RudolfThis article deals with the possible combination of high temperature fly ash with fluidisedbed fly ash. The main objective of the experiment is to verify the effect of the combination of thesetwo energy by-products on simpler systems – cement pastes. In the experimental part, the evolution ofhydration temperatures and the time course of volume changes were monitored. The results obtainedindicate that the addition of fluid fly ash to the mixture intensifies the hydration reaction, despitethe increase in the value of the water to cement ratio of the mixture. At the same time, there is aslight increase in volume changes, which can be considered as a very valuable contribution to technicalpractice, taking into account possible ecological or economic aspects.
- ItemProcessing and recycling of aggregate residues after ore extraction for stabilization of mined areas(Czech Technical University in Prague, 2024-05-13) Jančíková, Andrea; Dvořák, Karel; Ravaszová, SimonaThe article focuses on the treatment and recycling of aggregate. It also addresses the issue of treatments effects on mine tailings, fly ash and acid mine water on the measured parameters of concrete with load-bearing and backfilling paste with non-load-bearing function. Four different mixes were developed, and standard tests were performed on them. These mixtures were made with different types of mine tailing’s fillers with varying degrees of treatment. Mineralogical and chemical tests were carried out on the treated aggregates, with sieve analysis and their subsequent adjustment for suitable aggregate gradation curve in concrete. Strength and volumetric weight tests were carried out on hardened samples at 28, 56 and 90 days. The results of the determined functional specimens showed that it is possible to develop an almost completely waste-free technology using recycled aggregate and fly ash from the ore mining and energy industries and its subsequent processing and use for backfilling of mine deposits with load bearing and non-load bearing function concrete