Blended alkali-activated aluminosilicate binders

První část práce představuje souhrn dosavadních poznatků o směsných dvousložkových alkalicky aktivovaných pojivech na bázi vysokopecní strusky, popílku, metakaolinu a cihelného prachu s důrazem na jejich zpracovatelnost, mikrostrukturu, mechanické vlastnosti a trvanlivost. V experimentální části byla vyrobena alkalicky aktivovaná pojiva s různým poměrem popílku a metakaolinu a byla porovnána jejich zpracovatelnost a mechanické vlastnosti. Struktura pojiva byla hodnocena rastrovacím elektronovým mikroskopem (SEM) a vysokotlakou rtuťovou porozimetrií. Z prostudované literatury i vlastních dosažených výsledků vyplývá, že kombinace jednotlivých prekurzorů má pozitivní vliv na většinu posuzovaných vlastností materiálu.The first part of the work presents a summary of the current knowledge of two-component blended alkali-activated binders based on blast furnace slag, fly ash, metakaolin and ground brick with emphasis on their workability, microstructure, mechanical properties and durability. In the experimental part the alkali-activated binders with different ratio of fly ash and metakaolin were made to compare their workability and mechanical properties. The binder structure was evaluated by means of scanning electron microscopy (SEM) and mercury intrusion porosimetry. From the literature review and my own achievements it can be concluded that the combination of single precursors has a positive effect on the majority of the assessed properties of the material.

Impedance spectroscopy measurement of metakaolin-based alkali-activated building materials

Cement-containing as well as cement-free building materials are regarded as dielectrics. Therefore, electrically conducting admixtures are to be added to them in order to increase their electrical conductivity. Steel or carbon fibres, metal powder, graphite, carbon soot or carbon nanotubes are commonly used for this purpose. The conductivity increase offers new application options, such as sensor property materials, self-heated materials, or electromagnetic smog shielding materials. The specimens of the mixes to be studied were subjected to an electrical analysis carried out within the frequency range from 100 MHz to 3 GHz by means of an ZNC vector analyser and an SPEAG-made DAK-12 coaxial probe and, furthermore, a dedicated automatically measuring device operating within the frequency range from 40 Hz to 1 MHz. The frequency spectra of interest were measured on various copolymer specimens differing from each other by the content of graphite and carbon nanotubes. Higher content of these admixtures increases the electrical conductivity and the building materials thus become easier to measure by means of electromagnetic measuring methods

Binary alkali-activated composite materials with brick powder

Diplomová práce je zaměřena na použití cihelného prachu při výrobě směsných dvousložkových alkalicky aktivovaných pojiv se struskou, metakaolinem a popílkem. Teoretická část shrnuje současné oblasti použití keramického odpadu ve stavebnictví a technologii pojiv a předpoklady cihelného prachu pro alkalickou aktivaci. Geopolymery na bázi cihelného prachu vyrobené v experimentální části byly podrobeny zkouškám mechanických vlastností, porozity a mikrostruktury, tokové chování čerstvých geopolymerů bylo hodnoceno reometrickým měřením. V souladu s výsledky je možné říci, že cihelný prach může být vhodným prekurzorem pro směsná pojiva s metakaolinem a struskou, tyto vzorky vykázaly dobré mechanické vlastnosti i mikrostrukturu. Kombinace s popílkem byla méně vhodná kvůli rychlému tuhnutí, regulátor tuhnutí použitý v těchto pojivech způsobil značné zhoršení mechanických vlastností materiálu.The thesis is focused on the application of brick powder in production of binary alkali-activated binders with metakaolin, slag and fly ash. The theoretical part summarizes recent fields of use of the ceramic waste in construction and binder industry and prerequisite properties of the brick powder for alkaline activation. Brick powder based geopolymers made in the experimental work were tested for their mechanical properties, porosity and microstructure, flow properties of the fresh geopolymers were evaluated by rheometric measurements. In accordance with the results it can be concluded that brick powder could be a suitable precursor for blended binders with metakaolin and slag, these samples exhibited good mechanical properties and microstructure characteristics. The combination with fly ash was less applicable due to a rapid setting, hardening retarder used in these binders caused significant deterioration of the mechanical properties of the material.

Self-Sensing Properties of Metakaolin Geopolymer with Carbon Nanotubes under Compressive Loading

Increased capability of alkaline activated binders to transfer the electric charge became an attractive issue in research related to multifunctional materials with self-sensing, self-heating and other progressive properties. This study is focused on self-sensing properties of metakaolin geopolymer mortars with 0.05 and 0.10% carbon nanotubes under repeated compressive loading. Specimens incorporated with copper electrodes were subjected to two different regimes of compressive loading with continuous monitoring of strain and electrical resistance. Both reference and modified geopolymer mortars have shown good response to applied loading, yet the differences in sensitivity and structural deformations were observed

Self-Sensing Properties of Fly Ash Geopolymer Doped with Carbon Black under Compression

The development of smart materials is a basic prerequisite for the development of new tech-nologies enabling the continuous non-destructive diagnostic analysis of building structures. Within this framework, the piezoresistive behavior of fly ash geopolymer with added carbon black under compression was studied. Prepared cubic specimens were doped with 0.5, 1, and 2% carbon black and embedded with four copper electrodes. In order to obtain a complex character-ization during compressive loading, the electrical resistivity, longitudinal strain and acoustic emission were recorded. The samples were tested in two modes: repeated loading under low compressive forces and continuous loading until failure. The results revealed piezoresistivity for all tested mixtures, but the best self-sensing properties were achieved with 0.5% of carbon black admixture. The complex analysis also showed that fly ash geopolymer undergoes permanent deformations and the addition of carbon black changes its character from quasi-brittle to rather ductile. The combination of electrical and acoustic methods enables the monitoring of materials far beyond the working range of a strain gauge

Fracture parameters of fly ash geopolymer mortars with carbon black and graphite filler

In this study, the effect of carbon black and graphite filler on the crack initiation and fracture parameters of fly ash geopolymer mortar is investigated. The carbon black was added in the amount of 0.5 and 1.0% and graphite powder in the amount of 5 and 10% relative to the fly ash mass. The reference mixture without any filler was also prepared. The fracture characteristics were determined based on the results of the three-point bending test of prismatic specimens provided with an initial central edge notch. The fracture experiments were conducted at the age of 48 days. The vertical force (F), the displacement measured in the middle of the span length (d), and the crack mouth opening displacement (CMOD) were continuously recorded during the test. The records of fracture tests were subsequently evaluated using the effective crack model, work-of-fracture method, and double-K fracture model. The addition of both fine fillers led to a decrease in monitored mechanical fracture parameters in comparison with reference mortar