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Heavy metals escaping from industrial processes and industrial waste are a significant environmental hazard all around the globe. Since they cannot be destroyed, the only way to manage the pollution is to capture and contain the hazardous components. This study focuses on stabilization-solidification of a highly toxic industrial filter slag that contains a range of different heavy metals in extremely high quantities. The stabilization-solidification treatment was executed with a mayenite and gypsum based solid cementitious binder. The major components that were monitored during the study were selenium, lead and sulphate. Different ratios of gypsum addition were tested in order to observe the effect of total sulphate content in the system to the immobilization efficiency of anionic selenium and sulphate. During the experiments, all cationic heavy metals were immobilized efficiently, most of them achieving the immobilization efficiencies of more than 99.9%. By adjusting the sulphate content of the system, the immobilization efficiency of selenium was improved from 95.669% to 99.925% and the immobilization efficiency of sulphate raised from 96.069% to above 99.964%. Controversially, the immobilization of lead was at its highest (99.999%) with high sulphate content and dropped to 98.162% as the sulphate rate decreased. The results show clearly that mayenite has good potential for stabilization-solidification applications.

The present dissertation is dedicated to the development of a lyophilisation-based hydration stop technique, which works as instantaneously, completely, and non-invasively as possible in order to enable a complete characterisation of the early hydration stage with a particular focus on changes to chemical composition and morphology of the sample and in particular of the early hydration product ettringite that is of technical importance due to its influence on rheological properties. Furthermore, based on the developed lyophilisation technique, the impact of ettringite on the rheological properties of a model system containing quartz sand is quantified. Lastly, changes to hardened cement paste induced by the addition of hard magnetic iron oxide nanoparticles are investigated. It is essential to stop the hydration process instantaneously and entirely at any given time since the properties of hardened concrete can already be derived from the rheological properties of the cement paste suspension. However, it was not feasible with the state-of-the-art isopropanol-water exchange. Thus, a freeze-drying-based hydration stop technique had to be developed. In a first study, cementitious suspensions that were stopped at four different hydration times by lyophilisation, the state-of-the-art, as well as the combination of both techniques mentioned above, were compared. The ambiguous results of the samples’ comparison led, in the next step, to the examination of the influence of the levels and duration of treatment with low-pressure on pure synthetic ettringite. It was shown that a low-pressure of 400 Pa does not change the chemical composition nor the morphology of ettringite for at least 72 h. These results were published in a second article. Based on these, the freeze-drying technique was optimised to the extent that the ettringite content is highest after this hydration stop. The samples show the highest reproducibility compared to the state-of-the-art and the combined techni

Hazardous wastes are commonly immobilized using cementitious materials. Ettringite (Ca6Al2(OH)12(SO4)3∙26H2O) is one of the main components of hydrated cement and is known to stabilize anionic species. Thus, it is a promising material for the stabilization of arsenate (As(V)) in cementitious waste streams. However, the effects of As(V) incorporation into the ettringite structure on the structural properties of As and ettringite remain unclear. Herein, As(V) doping into the structure of ettringite was investigated based on the first-principles calculations using density functional theory (DFT), and the results suggested that the mechanism involving the substitution of AsO4 3− by SO4 2− was energetically favorable and that As doping increased the total bond order of ettringite, leading to a more stable structure. The elastic properties and anisotropy of ettringite and As-doped ettringite were also investigated using DFT calculations. The results showed that the mechanical properties of the As-doped ettringite structure were stable according to Born's criterion. Moreover, As doping increased the elastic constants and elastic modulus of ettringite but reduced its elastic anisotropy. These results provide valuable insights into the long-term stabilization of As species and their migration in cementitious wastes., Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public., Rivers, Ports, Waterways and Dredging Engineering

Shotcrete (sprayed concrete) differs from ordinary cast concrete through the application technique and the addition of set accelerators that promote immediate stiffening. The bond strength development between shotcrete and rock is an important property that depends on the texture of the rock, the type of accelerator, and application technique. This investigation focuses on the development of the microstructure in the interfacial transition zone (ITZ) and the strength of the bond at the shotcrete-hard rock boundary. The results show that the bond strength is related to the hydration process—that is, the strength gain of the shotcrete—and remains low before the acceleration period of the cement hydration. With a scanning electron microscope (SEM), it is possible to observe changes over time for the early development of the interfacial zone, both before and after proper cement hydration. Results from tests with wet-sprayed concrete on granite rock are presented. The test method—using both bond strength and the SEM to investigate the development of the microstructure at the ITZ—is interesting, but has to be more broadly examined. Different mixtures, accelerators, and rock types have to be used., QC 20230426

The present paper focuses on the study of mortar samples where expansions with thaumasite formation occur as a consequence of sulphate attack. The samples correspond to a masonry mortar used in a rural construction located in the Spanish province of Toledo made of cement with limestone filler addition CEM II/AL. Composition and microstructure of the mortars have been analysed by means of scanning electron microscopy (SEM) using secondary and backscattered electrons (BSE) and X-ray diffraction (XRD). The results show that aggregates are contaminated with gypsum, which is the source of the sulphates for the internal attack. It seems that thaumasite is formed through an ettringite transformation where aluminium atoms are replaced with silicon atoms by means of a solid solution. The study highlights that thaumasite can be formed in warm weather through an internal sulphate attack due to gypsum contamination of aggregates.

Tato diplomová práce je zaměřena na problematiku poruch zpevněných ploch působením objemových změn jílovitých zemin s obsahem sádrovců v lokalitě Mladá Boleslav. Úvodní část práce popisuje základní vlastnosti zemin pro stavby pozemních komunikací a poskytuje úvod do provádění úprav zemin hydraulickými pojivy. Následná část je zaměřená na problematiku poruch zpevněných ploch a návrh jejich sanace v lokalitě Mladá Boleslav., This thesis is focused on the problem of failures of paved surfaces due to volume changes of clay soils with gypsum content in the locality of Mladá Boleslav. The introductory part of the thesis describes the basic properties of soils for road construction and provides an introduction to the implementation of soil treatment with hydraulic binders. The subsequent part is focused on the problem of failures of paved surfaces and the proposal of their rehabilitation in the locality of Mladá Boleslav., Dopravní fakulta Jana Pernera, Uchazeč prezentoval komisi hlavní výsledky a závěry své diplomové práce. Po prezentaci diplomové práce zodpověděl dotazy vedoucího a připomínky oponenta diplomové práce (uvedeny v posudcích práce). V diskusi o diplomové práci podrobně zodpověděl všechny dotazy členů komise., Dokončená práce s úspěšnou obhajobou

The impact of low-pressure treatment on the crystal structure, morphology, and chemical composition of ettringite, due to their major importance with respect to processability (i.a., dry-ing conditions) and to the analysis of ettringite-containing samples, is examined utilizing X-ray diffraction, thermogravimetric analysis, Raman spectroscopy, and environmental scanning electron microscopy. Synthetic ettringite was treated for various durations (5 min up to 72 h) and at two different levels of low-pressure (4.0 mbar and 60 µbar). Evaluation showed a correlation between the procedural parameters (time and pressure), the chemical composition, and the morphology of ettringite. The experiments reveal that, when exposed to 4 mbar pressure, nearly no changes occur in the ettringite’s morphology, whereas the crystals undergo swelling and slight deformations at very low pressures (60 µbar and 35.3 nbar), which is attributed to the loss of bound water and the partial transformation from ettringite to quicklime, anhydrite, and calcium aluminate. Furthermore, the strongly dehydrated ettringite shows the same morphology.

In this study, we targeted a calcium hydroxide and ettringite composite-type expansive additive (EA) and obtained the basic characteristics of the EA mixed cement paste in order to create a method for calculating volume expansion based on the hydration reaction of the PCEA system. Expansion strain, setting time, and compressive strength were measured. In addition, we observed the state of EA after hydration using a micro-CT scanner and scanning electron microscope, and elucidated the expansion mechanism. Our results show that strain rapidly increased and the compressive strength decreased when the replacement ratio of the EA (Crep) exceeds 6.4%. At the same time, radial cracks were generated from the hydrated EA particles, suggesting that the EA itself grew to expand the cement paste. Although no ettringite was confirmed inside the EA when the Crep was 5.1%, when the Crep was 10.3%, ettringite was formed vertically from the surface of C3A with a large amount of pores. These results show that simultaneous formation of ettringite and pores causes rapid expansion., Materials and Environment

In this study, we targeted a calcium hydroxide and ettringite composite-type expansive additive (EA) and obtained the basic characteristics of the EA mixed cement paste in order to create a method for calculating volume expansion based on the hydration reaction of the PCEA system. Expansion strain, setting time, and compressive strength were measured. In addition, we observed the state of EA after hydration using a micro-CT scanner and scanning electron microscope, and elucidated the expansion mechanism. Our results show that strain rapidly increased and the compressive strength decreased when the replacement ratio of the EA (Crep) exceeds 6.4%. At the same time, radial cracks were generated from the hydrated EA particles, suggesting that the EA itself grew to expand the cement paste. Although no ettringite was confirmed inside the EA when the Crep was 5.1%, when the Crep was 10.3%, ettringite was formed vertically from the surface of C3A with a large amount of pores. These results show that simultaneous formation of ettringite and pores causes rapid expansion.

This study investigates the relationship between the strength development and hydration progress of cement-based solidifying agents (CBSAs) in cement-treated soil with volcanic mineral components. A CBSA is a cement-based material used as a soil stabilizer. It is known that the strength development of cement-based materials is inhibited by volcanic mineral components, e.g., allophane, and CBSAs are specially controlled against hydration inhibitions. Previous studies showed that allophane might be the governing factor for the inhibition of cement hydration, and its response to the hydration properties should be investigated. In this study, cement-paste and cement-treated–soil specimens are made with three types of binder (ordinary Portland cement, blast-furnace slag cement, and a CBSA) to investigate the hydration progress and strength development. Uniaxial compression tests were conducted, and the strength development was measured with the different binder types. It was found that the strengths of the cement-paste specimens at day 28 were almost the same with the three binders, while they differed in the mortar specimens that contained allophane. X-ray diffraction/Rietveld analyses were conducted to measure the hydration properties. From the results, it was supposed that, owing to the lack of Ca(OH)2, the pozzolanic reaction was stagnant. Considering the ion concentration of the pore water in the solidified materials, quantitative estimations of the strength development affected by allophane should be possible in the future.

Heat cured cement mortars may result in linear expansion due to later age ettringite precipitation, popularly termed as delayed ettringite formation (DEF). However, later age ettringite precipitation may not result in expansion always. To differentiate the expansive and non-expansive nature of heat-cured cementitious systems, in this research pore solution chemistry of various cementitious systems cured at 90°C for 12 hours were studied. Linear expansion of mortar bars was measured periodically. Besides, ettringite precipitation was studied using X-ray diffraction (XRD) and thermal gravimetric analysis (TGA). The XRD, TGA results show the absence of early age ettringite and its delayed precipitation in all the heat-cured cementitious systems irrespective of expansive or non-expansive mortars. However, the pore solution ionic concentration reveals that sulphate ion concentration at the end of heat curing is vital to predicting whether the mortar will expand or not in the future. The curing temperature increased the solubility of sulphates and total alkalis present in the pore solution. The expanded mortars had a relatively higher amount of sulphates in the pore solution at the age of 30 hours, compared to the non-expansive mortars. Further, at the age of 7 and 30 days, a drop in sulphate, sodium, potassium ions concentration in pore solution was noticed, suggesting the leaching of alkalis and consumption of Sulphate for the precipitation of ettringite.

The effect of including 5 % chloride salts (NaCl and CaCl2) on calcium sulfoaluminate cement hydration was studied. The rate of heat release, setting times and mechanical strength were determined in 2 d, 28 d and 90 d cement pastes. The hydration products formed at those ages were identified with XRD and SEM. Hydration reactions were hastened and early age strength heightened with 5 % NaCl. In contrast, 5 % CaCl2 retarded setting times, although it also increased later age compressive strength. The predominant reaction products found in both cases were ettringite and AH3. Chloraluminates such as Friedel’s salt were not observed to form at any of the ages studied. Gypsum precipitation, absent in the reference sample (CSA cement+water), was detected in the presence of chloride salts, however.

Ion exchange (IEX) resins can remove natural organic matter (NOM) from drinking water sources. However, the IEX system produces a waste brine rich of sodium, chloride, NOM and sulfate. The treatment of the waste brine aims to recover a clean solution rich of sodium chloride, that can be reused to regenerate IEX resin. Previous research showed that ceramic nanofiltration partially removes NOM from the waste brine, but sulfate removal requires additional treatment. Sulfate removal by chemical precipitation was previously studied either on brines with low NOM concentrations or water with low concentrations of NOM and salts. The current work focussed on sulfate removal from NOM-rich brines by chemical dosing of (1) BaCl2, resulting in precipitation of barite (BaSO4), and (2) CaCl2, Ca(OH)2 and NaAlO2, resulting in precipitation of calcium sulfate and, subsequently, ettringite (Ca6Al2(SO4)3(OH)12). Additionally, the effect of NOM on SO42− removal was studied. Modelling and batch experiments were conducted with IEX and synthetic brines within the typical ion strength range of 0.1 to 1 M. With doses of 2.2 g of BaCl2 per g of initial sulfate, BaSO4 precipitation removed more than 83 percent of sulfate, resulting in final concentrations below 0.4 g/L even in the presence of NOM. However, NOM inhibited the precipitation of calcium sulfate and, subsequently, ettringite. With doses of 1.3 g of CaCl2, 0.5–0.7 g of Ca(OH)2 and 0.4–0.6 g of NaAlO2 per g of initial sulfate, calcium sulfate and ettringite precipitation removed between 8 and 95 percent of sulfate from NOM-rich brines, resulting in final concentrations between 0.8 and 2 g/L. As a reference, NOM-free brines required doses of 1.3 g of CaCl2, 0.2–0.7 g of Ca(OH)2 and 0.1–0.6 g of NaAlO2 per g of initi, Sanitary Engineering

Recently, there has been increased use of calcium-nitrite and calcium-nitrate as the main components of chloride- and alkali-free anti-freezing agents to promote concrete hydration in cold weather concreting. As the amount of nitrite/nitrate-based accelerators increases, the hydration of tricalcium aluminate (C(3)A phase) and tricalcium silicate (C3S phase) in cement is accelerated, thereby improving the early strength of cement and effectively preventing initial frost damage. Nitrite/nitrate-based accelerators are used in larger amounts than usual in low temperature areas below -10 degrees C. However, the correlation between the hydration process and strength development in concrete containing considerable nitrite/nitrate-based accelerators remains to be clearly identified. In this study, the hydrate composition (via X-ray diffraction and nuclear magnetic resonance), pore structures (via mercury intrusion porosimetry), and crystal form (via scanning electron microscopy) were determined, and investigations were performed to elucidate the effect of nitrite/nitrate-based accelerators on the initial strength development and hydrate formation of cement. Nitrite/nitrate-AFm (aluminate-ferret-monosulfate; AFm) was produced in addition to ettringite at the initial stage of hydration of cement by adding a nitrite/nitrate-based accelerator. The amount of the hydrates was attributed to an increase in the absolute amounts of NO2- and NO3- ions reacting with Al2O3 in the tricalcium aluminate (C(3)A phase). Further, by effectively filling the pores, it greatly contributed to the enhancement of the strength of the hardened cement product, and the degree of the contribution tended to increase with the amount of addition. On the other hand, in addition to the occurrence of cracks due to the release of a large amount of heat of hydration, the amount of expansion and contraction may increase, and it is considered necessary to adjust the amount used for each concrete work.

Recently, there has been increased use of calcium-nitrite and calcium-nitrate as the main components of chloride- and alkali-free anti-freezing agents to promote concrete hydration in cold weather concreting. As the amount of nitrite/nitrate-based accelerators increases, the hydration of tricalcium aluminate (C(3)A phase) and tricalcium silicate (C3S phase) in cement is accelerated, thereby improving the early strength of cement and effectively preventing initial frost damage. Nitrite/nitrate-based accelerators are used in larger amounts than usual in low temperature areas below -10 degrees C. However, the correlation between the hydration process and strength development in concrete containing considerable nitrite/nitrate-based accelerators remains to be clearly identified. In this study, the hydrate composition (via X-ray diffraction and nuclear magnetic resonance), pore structures (via mercury intrusion porosimetry), and crystal form (via scanning electron microscopy) were determined, and investigations were performed to elucidate the effect of nitrite/nitrate-based accelerators on the initial strength development and hydrate formation of cement. Nitrite/nitrate-AFm (aluminate-ferret-monosulfate; AFm) was produced in addition to ettringite at the initial stage of hydration of cement by adding a nitrite/nitrate-based accelerator. The amount of the hydrates was attributed to an increase in the absolute amounts of NO2- and NO3- ions reacting with Al2O3 in the tricalcium aluminate (C(3)A phase). Further, by effectively filling the pores, it greatly contributed to the enhancement of the strength of the hardened cement product, and the degree of the contribution tended to increase with the amount of addition. On the other hand, in addition to the occurrence of cracks due to the release of a large amount of heat of hydration, the amount of expansion and contraction may increase, and it is considered necessary to adjust the amount used for each concrete work.

This work analyzes the effect of the presence of 5 wt.% of solid sodium salts (NaSO, NaCO, and NaSiO) on calcium sulfoaluminate cement (CSA) hydration, addresses hydration kinetics; 2-, 28-, and 90-d mechanical strength, and reaction product microstructure (with X-ray diffraction (XRD), and Fourier transform infrared spectroscopy, (FTIR). The findings show that the anions affect primarily the reactions involved. Ettringite and AH, are the majority hydration products, while monosulfates are absent in all of the samples. All three salts hasten CSA hydration and raise the amount of ettringite formed. NaSO induces cracking in the ≥28-d pastes due to posthardening gypsum and ettringite formation from the excess SO present. Anhydrite dissolves more rapidly in the presence of NaCO, prompting carbonation. NaSiO raises compressive strength and exhibits strätlingite as one of its reaction products.

Thaumasite has been synthetized with and without ettringite in the reaction medium. The compositions of solids have been analyzed over time by means of X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM-EDX) in order to check the relation between ettringite and thaumasite. The results indicate that in the synthesis in absence of ettringite, the thaumasite appears at 6 months. By contrast, in the synthesis with presence of ettringite, at 7 days much of the ettringite has become thaumasite and at 2 months ettringite has disappeared and only thaumasite is detected. The results obtained at the end of two years experience, using the Rietveld method, show that thaumasite forms from ettringite by substitution of aluminum with silicon.

With rapid industrialisation, the infrastructure sector has seen exponential growth in prefabricated concrete elements due to their speedy construction and efficient usage of material. Precast concrete elements have thus observed some deterioration due to increased internal temperature as a result of rapid curing, and also through deliberate heat curing techniques. This has led to researchers in the past to study the effect of such curing conditions on the durability aspect of the binders, especially their impact on Delayed Ettringite Formation. Precast elements such as railway sleepers, exposed to in the humid environment were thus prone to internal sulphate attack and needs to be investigated. Use of Ground Granulated Blast Furnace Slag (GGBFS) as a substitution for binder content in conventional portland cement in the Netherlands has been prevalent since the early 1900s primarily because of its abundant resource from iron industry. The benefits of slag have been then exploited as it was one of the supplementary cementitious systems which along with being a sustainable solution, provides good resistance to environmental degradation such as chloride penetration resistance. However, their advantages surrounding extreme curing conditions have to be studied, unless used at optimised quantities. The research focused on the potential of blast furnace slag systems to undergo internal sulphate attack due to high internal temperatures. The simulation of high internal temperature was done through heat curing inside an oven following which continuous storage under lime solution was carried out in order to saturate the system. Slag systems at low and high substitution levels (20% & 50%) were used along with a combination of coarser and finer surface areas, to investigate their subsequent influence was chosen for the study. Also, since infrastructure industry adopts CEM II & CEM III-A cement type, where the former was low slag concentration with moderate fineness and t, Civil Engineering | Structural Engineering

In this investigation, ettringite-based mortars were synthesized from ladle slag (LS) and phosphogypsum (PG), promoting the concept of a circular economy. However, the reuse of naturally occurring radioactive materials (NORM), such as PG, requires radiological investigation. Also, the immobilization degree for contaminants contained in PG should be evaluated. The former was investigated using gamma spectroscopy and radon exhalation/emanation tests, while the latter was assessed using an up-flow percolation column test according to the CEN/TS 16637‐3. The produced mortars comply with current legislation on naturally occurring radionuclides (NOR) in building materials, proving that they can be safely used for building purposes. The radon emanation decreased upon increasing the Polish PG content, which was mainly determined by the microporosity. The specific surface areas were 20‐30 times lower than conventional cement, and the immobilization degree for contaminants was generally high (>90%). This investigation demonstrates high potential for PG reuse in ettringite-based mortars.

Ladle slag (LS) is a by-product of refining molten steel. Given that the production of one ton of crude steel produces 12–15 kg of LS, Europe produces approximately 2.6 million tons of this slag annually. In Finland, LS currently has limited use in low-value applications. It has shown high potential in producing cementitious binders due to its high calcium and aluminum content. The goal of this thesis is to offer the best solution to utilize LS in the construction industry for both its environmental and economic benefits. To achieve this goal, the present research focuses on two pathways: (1) Developing a cementitious binder with minimal pre-treatment for raw materials and chemicals that meets the requirements to be used as a construction material (papers I–II) (2) Producing a high-performance fiber-reinforced cementitious composite from the LS-based binder with a good balance of high mechanical performance, small carbon footprint, embodied energy, and high durability (papers II–IV). This thesis is based on studies that have found that LS can hydrate with gypsum to form an ettringite-based binder for which the only treatment needed is milling the precursors. Citric acid works effectively in the binder as a set retarder to control setting time and workability. The binder can thus be used in various construction applications. Polypropylene fiber can be used to produce the most balanced ettringite-based composite considering mechanical performance, CO2 emission, and embodied energy with great resistance under chemical and physical stress. The results of this thesis will enable better utilization of LS for high-value construction applications., Tiivistelmä Mikserikuona (LS) on teräksenvalmistuksen sivutuote. Jokainen tonni raakaterästä voi tuottaa noin 12–15 kg kyseistä kuonaa, joten Euroopassa tuotetaan yhteensä noin 2,6 miljoonaa tonnia tätä kuonaa vuodessa. Suomessa LS:n käyttö on tällä hetkellä rajoittunut matalan lisäarvon sovelluksiin. Kyseinen kuona omaa kuitenkin suuren potentiaalin sementtisideaineiden valmistuksessa korkean kalsium- ja alumiinipitoisuutensa vuoksi. Tämän väitöskirjan tavoitteena on löytää korkeamman lisäarvon ratkaisu LS:n hyödyntämiseen rakennusteollisuudessa sekä ympäristön että taloudellisten hyötyjen näkökulmasta. Tämän tavoitteen saavuttamiseksi tässä tutkimuksessa tarkastellaan kahta hyödyntämisreittiä: (1) Rakennusmateriaalien mekaaniset vaatimukset täyttävän sementtisidosaineen kehittäminen minimaalisella raaka-aineiden esikäsittelyllä ja kemikaalien lisäyksellä (julkaisut I–II) (2) Korkean suorituskyvyn kuituvahvisteisen komposiitin kehittäminen LS-pohjaisesta sideaineesta, joka omaa korkean mekaanisen suorituskyvyn, pienen hiilijalanjäljen, korkean kestävyyden, ja jonka valmistus on energiatehokasta (julkaisut II–IV). Tämä väitöskirja pohjautuu tutkimuksiin, joissa on todettu, että LS lujittuu yhteisreaktiossa kipsin kanssa muodostaen ettringiittipohjaisen sideaineen, jota varten ainoa tarvittava käsittely on raaka-aineiden jauhaminen. Sitruunahappo toimii sideaineessa tehokkaasti hidastimena säätäen asettamisaikaa ja parantaen työstettävyyttä. Sideainetta voidaan siten käyttää erilaisissa rakennussovelluksissa. Polypropeenikuituja voidaan käyttää tuottamaan optimaalinen ettringiittipohjainen komposiitti ottaen huomioon mekaaniset ominaisuudet, hiilidioksidipäästöt ja valmistusenergia, ja jolla on lisäksi riittävä kestävyys kemiallisessa ja fysikaalisessa rasituksessa. Tämän opinnäytetyön tulokset mahdollistavat LS:n paremman hyödyntämisen korkean lisäarvon sovelluksissa rakennusteollisuudessa.

The paper describes the heave experienced by two embankments providing access to a bridge located in a high-speed railway line. The compacted soil, a mixture of a low plasticity clay, sand and gravel, had a significant sulphate content (2 – 2.5%). The embankments received a reinforcing treatment by mixing the soil with cement in the proximity of the bridge abutments. In addition, a grid of grouting columns provided more stiffness to the embankments. The embankments experienced a fast heaving rate (around 4 mm/month) in the areas improved by cement mixing. Precision extensometers indicated that heave concentrated in the upper 6 – 8 m of the embankments. The sulphate content reduced sharply to 0.25% at increasing depth. No heave was detected in these deeper zones. The swelling was found to be associated with the development of thaumasite and ettringite minerals. The presence of clay, cement and sulphates in the compacted soils and the infiltration of water from rainfall events are ideal conditions for the growth of the mentioned minerals. Long-term tests performed on compacted samples provided a good evidence of the phenomena developing in situ. A chemical modelling of the mineral changes at the soil-cement interface provided an additional insight into the development of swelling, which could last for a long time (several years). Accordingly, it was decided to underpin the railway track and to excavate the upper active volume of the embankments. This solution went in parallel with train service, which was never interrupted., Postprint (published version)

The behavior of sulfoaluminate (CSA) cements hydrated in neutral or alkaline solutions (0 M, 0.1 M, 1 M, 4 M and 8 M NaOH) was studied. 2-d, 28-d and 90-d mechanical strengths were determined, as well as the reaction rate by isothermal conduction calorimetry. The reaction products were characterised with XRD, DTA and SEM. The findings revealed differences in performance depending on whether hydration transpired at pH ≤ 14 (0.1 and 1 M) or pH > 14 (4 M and 8 M). To 0.1 M and 1 M, there is an improvement of mechanical strength than in water-hydrated pastes. The majority reaction products in these conditions were ettringite and microcrystalline aluminium hydroxide. Mechanical strength was lower in the high alkalinity (4 M and 8 M) than in the reference pastes, mainly due to the formation of different reaction products. Ettringite was unstable at 4 M and failed to form at 8 M, whilst thenardite and U-phase were detected in the 28d and later materials hydrated at both concentrations.

Recent studies on the harmful effects of sulfates on OPC have shown that these salts can be immobilised by conversion to insoluble BaSO4. The response of blended OPC-BaCO3 cement to thaumasite sulfate attack is still poorly understood, however. This study explored the effect of BaCO3 on sulfate resistance in fairly high C3A (>10%) OPC mortars and pastes in the presence and absence of CaCO3. Further to the findings, due to low BaCO3 solubility at 8 °C, the temperature that favours thaumasite precipitation, neat OPC sulfate resistance was only slightly improved. Specimens, particularly mortars with 12.5% BaCO3 and no added CaCO3 (12.5B), deteriorated due to gypsum, ettringite and thaumasite precipitation, although less intensely than the samples bearing other blends. None of the BaCO3 or BaCO3 + CaCO3 blends performed better than the commercial sulfate-resistant cement used as the reference.

Expansive concretes based on the formation of ettringite from calcium sulfoaluminate agents are presented as an effective alternative to minimize the problems derived from shrinkage and low tensile strength at the early ages of the concrete. However, determining the mechanism responsible for the expansion is still a controversial issue today. In this study, the influence of three doses of expansive agent on fresh state and on compressive strength and magnitude of free expansion under two curing environments was evaluated on a reference mixture of self-compacting concrete (SCC). The microstructural evolution of the hydrates and anhydrous related with the expansive phenomena was also studied. From our observations it seems that an eminently amorphous ettringite is formed and that this ettringite would be strongly related to expansion. As a result, the influence of the ratio w/cementitious material and curing environment on the magnitude of the expansion as well as the influence of this on the mechanical properties of the SCCs was identified.

In drinking water production, natural organic matter (NOM) is sometimes removed using ion exchange (IEX) resin. This treatment method has a limitation based on the exchanging capacity on the resin. Therefore, the resin needs to be regenerated when it is saturated with adsorbed NOM which leads to the production of brine. In general, NaCl is used to regenerate the resin, hence, the brine will contain NOM, high sodium and chloride concentrations. Moreover, some other anions are also found in the IEX brine, such as sulphate that is usually present in surface water and ground water. Because of its salinity, the disposal of IEX brine is not possible to be done conventionally due to its impact on the environment and high cost. Therefore, separating chloride from the brine is an interesting alternative that can be reused for the regeneration of the IEX in the later process. Ceramic nanofiltration (NF) emerges to be an interesting alternative for water treatment. Compared to polymeric membranes, this type of membrane offers great mechanical robustness and can be operated under extreme conditions, and tolerates high-pressure backwash, chemical cleaning, and high-temperature sterilization, which leads to longer periods of reliable performance. Moreover, ceramic NF membranes are potentially capable to separate multivalent ions from monovalent ions. Hence, this method could be applicable to treat IEX brine. Alternatively, chemical precipitation using barium and calcium is widely used to remove sulphate from water which is more straight forward than membrane filtration. The precipitates can be mechanically separated from the supernatant for further treatment or use. Combination of chemical precipitation and ceramic NF membrane (later called as integrated sulphate removal) was investigated to remove sulphate from IEX brine. Along with that, investigation using synthetic brines consisting of Na2SO4 and NaCl for a binary salt solution and only Na2SO4 for a single, Civil Engineering

There has recently been an increased use of anti-freezing agents that are primarily composed of salt- and alkali-free calcium nitrite (Ca(NO2)2) and calcium nitrate (Ca(NO3)2) to promote the hydration reaction of concrete in cold weather concreting. Nitrite–nitrate based accelerators accelerate the hydration of C3A and C3S in cement more quickly when their quantities are increased, thereby boosting the concrete’s early strength and e ectively preventing early frost damage. However, the connection between the hydrate formation behavior and the strength development characteristic over time has yet to be clearly identified. Therefore, in this study, a wide range of physicochemical reviews were carried out to clarify the relationship between the hydrate formation behavior and the strength development characteristics, both at an early age and at later ages, which results from the addition of nitrite–nitrate based accelerators to concrete in varying amounts. These accelerators also act as anti-freezing agents. The results show that an increased quantity of nitrite–nitrate based accelerators caused an increase in the early strength of the concrete. This was due to the formation of nitrite and nitrate hydrates in large amounts, in addition to ettringite containing SO4 2, which is generated during the hydration reaction of normal Portland cement at an early age. On the other hand, at later ages, there was a rise in nitrite and nitrate hydrates with needle crystal structures exhibiting brittle fracture behavior. A decrease in C–S–H gel and Ca(OH)2 hydrates, deemed to have caused a decline in strength on Day 3 and thereafter, was also observed.

Delayed ettringite formation (DEF) is a significant deterioration process in concrete which involves the growth of ettringite [Ca6Al2(SO4)3(OH)12 ·26H2O] crystals leading to cracking and reduction of compressive strength. Conditions leading to DEF are well known and include among others cement chemistry, presence of humidity, heat curing of concrete structures, and the presence of cracks. The mechanisms and kinetics by which deterioration occur is still not well understood despite numerous investigations. Understanding the mechanism and kinetics of concrete deterioration due to DEF is important in order to prevent such costly deterioration and to improve concrete durability. In this research, concrete specimens were prepared with type III Portland cement and under different conditions that were designed to either promote or inhibit DEF. These consisted of a control set, a set subjected to a heat cycle and a third set made with elevated potassium content of 1.72% and also thermally cycled. They were tested periodically up to 380 days by conventional methods such as expansion and weight change measurements and compressive strength testing. Scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDAX) confirmed the presence and the morphology of ettringite in voids at different ages. Simultaneous neutron and X-ray tomography, a new nondestructive microscopic method was used to scan the specimens at regular intervals in order to assess the feasibility of the method in monitoring the progress and characterizing DEF induced damages. The linear regression analysis of the correlation of expansion with weight change data revealed that expansion and deterioration process occurred in three distinct successive stages. In the first stage, the ettringite fills the pores with little or no expansion; in the second, the expansion appears to be creep due to expansive stresses in the filled pores and in the third stage, crack propagation leads to significant expansion

Aiming to utilize phosphogypsum (PG) as a construction material, this study investigated the potential use of PG as a calcium sulfate source for the production of an ettringite-based binder (LSG). Six compositions with different percentages and PG’s of different origin were hydrated with ladle slag (LS) to form LSG. The hydration, mineralogy and compressive strength of all mixtures were investigated and compared with a reference LSG made of pure synthetic gypsum. The minor impurities in PG, the different particle size distribution as well as the mineralogy induced distinguishable effects on the heat of hydration, phase assemblage and morphology. The results showed that the use of side-stream PG instead of pure gypsum results in superior properties with a 60% increase in compressive strength. This investigation shows high potential to produce a completely by-product-based LSG by combining different sources of industrial side-streams with minimal chemical and energy use.

High-performance fiber reinforced cementitious composites from ettringite-based binders require much understanding of durability before its real-life applications in construction industry. A strain-hardening fiber reinforced ettringite-based composite from the hydration between ladle slag and gypsum with polypropylene (PP) fibers was the object in this study. To investigate the durability of the developed composite under aggressive conditions in cold regions (e.g., the Northern Europe), the material was subjected to a combined sodium sulfate-chloride solution along with freeze-thaw cycling process, which represented the marine environment of cold regions. The experimental study reports the vital role of PP fibers in control crack propagation and, hence, greatly enhanced the durability of the composite. In addition, the developed composite attained good mechanical performance with deflection-hardening behavior and multiple crack even after aging processes. Materials, aged in water, was mainly destructed by volume expansion from water uptake in structural pores, while those, cured in Na2SO4NaCl solution, was mainly spoiled by volume increase from both physical and chemical attacks.

The use of industrial by-products brings both economic and environmental benefits. Ladle slag (LS) from steel processes is a promising raw material and has been used as a precursor in a few studies. To better understand the benefits of LS mainly on mechanical behavior, in this investigation, an ettringite-based binder was produced from the hydration between LS and gypsum. The material was reinforced with 2% v/v high tenacity polypropylene (HTPP) fiber to attain a high performance fiber reinforced cementitious composite with pseudo strain hardening (PSH) behavior. In addition, results of FEM numerical analysis show the accurateness of an available constitutive model in predicting the mechanical response of the HTPP fiber reinforced hydrated LS composite. Additionally, the experimental results reveal that using HTPP fiber greatly enhanced the mechanical properties of the hydrated LS. Moreover, PSH behavior and eventually multiple fine cracks were recorded by the digital image correlation (DIC) technique under uniaxial tensile tests. The numerical simulations show the capability of the concrete damage plasticity (CDP) model to predict the nonlinear behavior of the material with a good agreement between experimental and numerical predictions.

The urge to use more environmentally friendly construction materials has motivated the boost of initiatives which intend to reduce the high levels of pollution that construction materials generate in their manufacturing. A good example of this is the Paper Chain European initiative, which aims to find different innovative ways to use the waste streams generated by the Pulp and Paper Industry. More in particular, it consists on focusing on the valorization of ash produced in the energy recovery from paper waste, produced by recycling pulp mills as alternative binder for soil stabilization works in road projects. This new material, a sall waste used in civil engineering, needs to be assessed and understood so it can be properly used under different conditions. For this reason, new alternative procedures are proposed in this project thesis to study its behavior. The result of all the tests will give a comprehensive idea of the pros and cons that the use of this material may cause in comparison to the most historically used material in soil stabilization, cement. The most important issue to analyze is the possible formation of ettringite or thaumasite minerals in the pavement structure, which is the main cause of heave that takes place inroads mainly due tosulfate attack circumstances. Different tests have been carried out to assess this issue, under different temperature and sulfateattack conditions.

The renovation and replacement of historical plasters is still a very current topic. Today’s trend is for the production of dry mortar mixtures that can be used for the renovation of historic buildings. The article therefore focuses on the preparation of gypsum-modified lime-metakaolin mortar. An experiment consisted of two stages. In the first stage of the experiment, the basic technological properties of fresh and hardened mortars were examined (bulk density of fresh and hardener mortar, compressive and flexural strength). The second stage aimed at monitoring the hydration process in different environments. Environments should simulate real factors affecting the plaster (humidity, low and higher temperatures). To determinate of the phase composition, the X-ray diffraction analysis was used. The results showed that gypsum in the lime-metakaolin plaster caused an increase in compressive and flexural strength. The presence of gypsum also conduced to the formation of ettringite and this has caused volumetric changes., Renovace a obnova historických omítek je stále velmi aktuální téma. Dnešní trendem je výroba suchých maltových směsí, které lze použít k renovaci historických budov. Článek se proto zabývá přípravou vápenno-metakaolinové malty modifikované sádrou. Experiment se skládal ze dvou fází. V první fázi experimentu byly zkoumány základní technologické vlastnosti čerstvých a zatvrdlých malt (objemová hmotnost čerstvé a zatvrdlé malty, pevnost v tlaku a ohybu). Druhá fáze je zaměřena na zkoumání hydratačního procesu v různých prostředích. Prostředí by měly simulovat skutečné faktory ovlivňující omítku (vlhkost, nízké a vyšší teploty). Na stanovení fázového složení, byla použita rentgenová difrakční analýza. Výsledky ukázaly, že přídavek sádry v omítce způsobila nárůst pevnosti v tlaku a v ohybu. Přítomnost sádry také vedla k tvorbě ettringitu, který může vést k objemovým změnám.

Synopsis: Concrete with w/c ratio of 0.2 and lower is indeed material of a new generation. Its properties significantly surpass such of regular concrete grades in large due to the absence of mixing water not actively involved in the physical-chemical processes of cement hydration. In a sense, w/c ratio of 0.2 signifies a threshold in the material science of concrete that no research did reach before 1990s. To move this realm even further, we have been aiming at producing UHPC that crosses this threshold we felt a necessity to define a basic phenomenology of such concrete hardening, especially on the early stages. Our analysis of the kinetics of the strength gain provides that this concrete gains its main physical-mechanical properties after 7 days, and its compressive strength exceeds 100 MPa (14 500 psi) already after 24 hours in normal conditions. At last, this type of UHPC is economically viable due to a relatively low content of cement (500kg/m3 (31.2 pcf)), the use of ordinary fine aggregate, and a possibility of using standard batching equipment in the production., QC20190408

The renovation and replacement of historical plasters is still a very current topic. Today’s trend is for the production of dry mortar mixtures that can be used for the renovation of historic buildings. The article therefore focuses on the preparation of gypsum-modified lime-metakaolin mortar. An experiment consisted of two stages. In the first stage of the experiment, the basic technological properties of fresh and hardened mortars were examined (bulk density of fresh and hardener mortar, compressive and flexural strength). The second stage aimed at monitoring the hydration process in different environments. Environments should simulate real factors affecting the plaster (humidity, low and higher temperatures). To determinate of the phase composition, the X-ray diffraction analysis was used. The results showed that gypsum in the lime-metakaolin plaster caused an increase in compressive and flexural strength. The presence of gypsum also conduced to the formation of ettringite and this has caused volumetric changes., Renovace a obnova historických omítek je stále velmi aktuální téma. Dnešní trendem je výroba suchých maltových směsí, které lze použít k renovaci historických budov. Článek se proto zabývá přípravou vápenno-metakaolinové malty modifikované sádrou. Experiment se skládal ze dvou fází. V první fázi experimentu byly zkoumány základní technologické vlastnosti čerstvých a zatvrdlých malt (objemová hmotnost čerstvé a zatvrdlé malty, pevnost v tlaku a ohybu). Druhá fáze je zaměřena na zkoumání hydratačního procesu v různých prostředích. Prostředí by měly simulovat skutečné faktory ovlivňující omítku (vlhkost, nízké a vyšší teploty). Na stanovení fázového složení, byla použita rentgenová difrakční analýza. Výsledky ukázaly, že přídavek sádry v omítce způsobila nárůst pevnosti v tlaku a v ohybu. Přítomnost sádry také vedla k tvorbě ettringitu, který může vést k objemovým změnám.

The renovation and replacement of historical plasters is still a very current topic. Today’s trend is for the production of dry mortar mixtures that can be used for the renovation of historic buildings. The article therefore focuses on the preparation of gypsum-modified lime-metakaolin mortar. An experiment consisted of two stages. In the first stage of the experiment, the basic technological properties of fresh and hardened mortars were examined (bulk density of fresh and hardener mortar, compressive and flexural strength). The second stage aimed at monitoring the hydration process in different environments. Environments should simulate real factors affecting the plaster (humidity, low and higher temperatures). To determinate of the phase composition, the X-ray diffraction analysis was used. The results showed that gypsum in the lime-metakaolin plaster caused an increase in compressive and flexural strength. The presence of gypsum also conduced to the formation of ettringite and this has caused volumetric changes., Renovace a obnova historických omítek je stále velmi aktuální téma. Dnešní trendem je výroba suchých maltových směsí, které lze použít k renovaci historických budov. Článek se proto zabývá přípravou vápenno-metakaolinové malty modifikované sádrou. Experiment se skládal ze dvou fází. V první fázi experimentu byly zkoumány základní technologické vlastnosti čerstvých a zatvrdlých malt (objemová hmotnost čerstvé a zatvrdlé malty, pevnost v tlaku a ohybu). Druhá fáze je zaměřena na zkoumání hydratačního procesu v různých prostředích. Prostředí by měly simulovat skutečné faktory ovlivňující omítku (vlhkost, nízké a vyšší teploty). Na stanovení fázového složení, byla použita rentgenová difrakční analýza. Výsledky ukázaly, že přídavek sádry v omítce způsobila nárůst pevnosti v tlaku a v ohybu. Přítomnost sádry také vedla k tvorbě ettringitu, který může vést k objemovým změnám.

Lime precipitation has been used for the treatment of mine water for decades; however, the impact of precipitation conditions is not adequately known. In this thesis, four aspects related to the removal of sulphate from mine water by lime precipitation are considered: the effect of magnesium on lime precipitation, the utilisation of by-products in lime precipitation, enhancement of lime precipitation, and utilisation of the precipitate. Sulphate removal in the presence of magnesium at the commonly used lime precipitation treatment pH of 9.6 was found unefficient as magnesium was keeping the sulphate soluble in the form of magnesium sulphate. At higher treatment pH of 11.5, magnesium that was naturally present in the mine water was shown to precipitate as magnesium hydroxide, which could serve as seed crystals for gypsum or co-precipitate sulphate thus enhancing sulphate removal. Quicklime manufacturing generates by-products that, currently, have few applications. The by-products examined in this study were successfully applied for mine water neutralization replacing commercial lime products. These by-products were found to remove sulphate equally well from the mine water. However, differences between by-products were observed in the consumption, and produced sludge quantities and qualities. An enhanced lime precipitation method is the precipitation as ettringite, which was used to reduce the sulphate content in mine water to less than the value set as the drinking water guideline in Finland. Furthermore, the formed precipitate was found to remove arsenate from the model solution., Tiivistelmä Vaikka kalkkisaostusta on käytetty kaivosten vesienkäsittelyyn useiden vuosikymmenten ajan, tieto olosuhteiden vaikutuksesta käsittelyn tehokkuuteen sulfaatin poiston osalta on puutteellista. Tämä väitöskirja käsittelee sulfaatinpoistoa kaivosvesistä kalkkisaostuksen avulla neljällä eri osa-alueella: magnesiumin vaikutus kalkkisaostukseen, kalkinpolton sivutuotteiden hyödyntäminen kalkkisaostuksessa, kalkkisaostuksen tehostaminen ja muodostuvan saostuman hyödyntäminen. Magnesiumin todettiin kokeellisesti ja laskennallisesti haittaavan sulfaatin poistoa kaivosvedestä kalkkisaostuksessa yleisesti käytetyssä pH:ssa 9.6 pitämällä sulfaattia liukoisessa muodossa magnesiumsulfaattina. Korkeammassa pH:ssa 11.5 puolestaan kaivosveden luontaisesti sisältämän magnesiumin havaittiin kokeellisesti ja laskennallisesti saostuvan magnesiumhydroksidina, joka voi toimia siemenkiteinä kipsille tai kerasaostaa sulfaattia ja siten tehostaa sulfaatin poistoa. Kalkinpolton sivutuotteina muodostuu jakeita, joille ei tällä hetkellä ole juurikaan käyttökohteita. Tässä työssä käytettiin kalkinpolton sivutuotteita korvaamaan kaupallista kalkkia kaivosveden neutraloinnissa. Sivutuotteet poistivat sulfaattia yhtä tehokkaasti kuin kaupalliset kalkkituotteet. Sivutuotteiden välillä havaittiin eroja niiden kulutuksessa sekä muodostuvan lietteen määrässä ja laadussa. Saostuksella ettringiittinä, joka on tehostettu versio perinteisestä kalkkisaostuksesta, saavutettiin sulfaattipitoisuuden lasku alle Suomessa juomavedelle käytetyn suositusarvon. Lisäksi havaittiin muodostuneen ettringiittisaostuman olevan potentiaalinen materiaali arsenaatin poistoon vedestä.

Concrete pavements are an important part of our national infrastructure. In recent years the relatively small number of reported joints deteriorating prematurely in concrete pavements around Indiana has increased. Changes over the past 45 years in INDOT specification, pavement materials, designs and construction practices, and current de-icing materials were examined and related to the durability of concrete at the joints of existing pavements. A survey of concrete pavements across the state revealed that no pavements from the two southern districts less than 40 years old showed this distress except in more recently placed patches. Cores were retrieved from the joints and mid-panel of 11 pavement sections that represented different materials, ages, construction, deicer exposure, and different levels of deterioration, from non-deteriorated concrete to concrete with severe deterioration at the joints. The pavement base drained well at the mid-panel of most pavements but was reduced at the joints for over half the pavements with the most severe joint deterioration associated with the slowest drainage. None of the concrete had an air void system that met all the criteria recommended for FT durable concrete but was better at the mid-panel than at the joints. Infilling and lining of the entrained air voids with ettringite and some Friedel’s salt was more common near the joints and could account for the reduced air void system. The FT testing did not correlate directly with the air void parameters but generally mid-panel samples did test as more durable than joints. Evidence from the presence of unhydrated cement grains suggested that the concrete at the joint face was not fully cured. One pavement section that did not have fly ash had worse deterioration than the panels nearby that had fly ash and calcium hydrate was more noticeable in the concrete from joints with severe deterioration. Several variables were identified that influence the durability of the concrete at the

Une augmentation de la température à jeune âge du béton peut être causée par la chaleur d’hydratation dans le cas d’éléments massifs ou par l’application d’un traitement thermique dans l’industrie de la préfabrication. Lorsque le couple critique température maximale/durée de maintien est dépassé, il y a formation différée de l’ettringite (DEF) expansive pouvant fissurer les pièces. Les travaux présentés dans ce mémoire ont pour but principal d’établir une limite sécuritaire pour des mélanges V-S pour béton de masse et V-P pour béton préfabriqué régulièrement utilisés par le Ministère des Transports du Québec. Ces bétons utilisent des liants binaires composés de fumée de silice de type GUb-SF et des liants ternaires composés de fumée de silice et de cendres volantes ou de laitier de haut-fourneau. La norme canadienne actuelle (CSA A23.1-14 et CSA A23.4-16) impose une limite fixe de température qui ne dépend ni de la durée de traitement ni du type de liant utilisé. Le lien, souvent énoncé dans la littérature, entre la réponse d’un liant à un traitement thermique et sa composition chimique et minéralogique, déterminé respectivement par fluorescence X et diffraction des rayons X couplée par la méthode de calcul Rietveld, a pu être confirmé. Le rapport SO3 solubles/Al2O3 est notamment ce qui permet la meilleure estimation de la sensibilité d’un liant. Le processus de formation différée de l’ettringite est lent et peut prendre plusieurs années. Donc, pour étudier le phénomène, des méthodes d’essais accélérés ont été testées. Des méthodes ont ainsi pu être proposées pour de futurs tests. Une méthode d’essai rapide d’expansion de barres de mortier permet d’identifier les liants les plus sensibles à la DEF. La formation de la DEF dans les liants les moins sensibles peut être appréciée par le gain de masse de prismes de béton et leur observation microstructurale au microscope électronique à balayage (MEB). Une méthode sur bétons de masse et bétons préfabriqués permet de class, A heat cure for concrete can be caused by hydration in massive structures or by thermal treatment in prefabrication industry. When the limit couple maximum temperature/duration of treatment is exceeded, the delayed formation of ettringite occurs and leads to cracking in concrete. The main goal of the work presented in this essay is to establish a safe batch limit for some mixtures, VS (mass concrete) and V-P (precast concrete) which are often used by MTQ. These concretes use some cements blended with silica fume and ternary blended cements with silica fume and fly ash or blast furnace slag. Indeed, the current Canadian standard (CSA A23.1) set a limit which doesn’t depend on duration of the treatment nor the type of bender. However, the link between composition of the used bender, with can be determined by X-ray fluorescence and X-ray diffraction, and the response to a thermal treatment has been confirmed. The soluble SO3/Al2O3 ratio allows to estimate if a bender is sensitive to heat cure. The delayed formation of ettringite is a long process which can last a decade. In order to study this phenomenon, several accelerated test methods have been used. Some of them are available for some future tests. An accelerated expansion method using mortar bar allows to spot the DEF-sensitive benders. Delayed ettringite formation in the less sensitive bender can be estimated by weight gain in concrete prisms and by observation with scanning electron microscope (SEM). The sensitivity level of a bender can by estimated using a method based on weight gain. Ternary blended cements show a greater ability to withstand DEF. The sensibility of binary blended cements depends on soluble SO3/Al2O3 ratio.

This work is focused on the possibilities of utilization of ashes from fluidized bed combustion, i.e. FBC ashes, for the manufacturing of hydraulic lime. Alternative hydraulic binders are becoming very popular in the present due to requirements on reducing CO2 emissions. FBC ash is an easily available, though not easily usable raw material. Because it has several hydraulic characteristics, it can create a hydraulic binder together with lime. Mixtures of hydrated lime and FBC ash from filters and from a bed were prepared in this work. The main criterion was the hydraulic modulus. The physico-mechanical properties were observed and were compared with the reference sample, which was hydraulic lime from industrial production. The prepared hydraulic limes achieved similar parameters as commercially manufactured hydraulic limes or lower strength class cements., Tato práce je zaměřena na možnosti využití popela ze spalování ve fluidním loži, tj FBC popel, pro výrobu Hydraulické vápno. Alternativní hydraulická pojiva se stávají velmi populární v současnosti kvůli požadavkům na snížení emisí CO2. FBC ash je snadno dostupné, i když ne snadno využitelných surovin. Protože má několik hydraulické vlastnosti, může vytvořit hydraulické pojivo s vápnem. V této práci byly připraveny směsi hořčíku a FBC popela z filtrů a z lůžka. Hlavním kritériem byl hydraulický modul. Fyzikálně mechanické vlastnosti byly pozorovány a byly porovnány s referenční vzorek, což byl Hydraulické vápno z průmyslové výroby. Připravené hydraulická vápna dosáhnout podobné parametry jako komerčně vyráběných hydraulická vápna nebo nižší cementy pevnostní třídy.

The objective of this paper is to evaluate the influence of sulfate exposure on the pore network development of several Portland cement matrices. MIP, XRD and SEM analysis were performed at different ages in samples exposed to sulfates after 2 days of casting. Results suggest that patterns of precipitation of the expansive products are linked to the degree of refinement of the pore network. During early stages of exposure, large pores concentrate a higher proportion of the expansive product formed. At later stages, precipitation evolves towards finer pore sizes., Peer Reviewed, Postprint (author's final draft)

This work is focused on the possibilities of utilization of ashes from fluidized bed combustion, i.e. FBC ashes, for the manufacturing of hydraulic lime. Alternative hydraulic binders are becoming very popular in the present due to requirements on reducing CO2 emissions. FBC ash is an easily available, though not easily usable raw material. Because it has several hydraulic characteristics, it can create a hydraulic binder together with lime. Mixtures of hydrated lime and FBC ash from filters and from a bed were prepared in this work. The main criterion was the hydraulic modulus. The physico-mechanical properties were observed and were compared with the reference sample, which was hydraulic lime from industrial production. The prepared hydraulic limes achieved similar parameters as commercially manufactured hydraulic limes or lower strength class cements., Tato práce je zaměřena na možnosti využití popela ze spalování ve fluidním loži, tj FBC popel, pro výrobu Hydraulické vápno. Alternativní hydraulická pojiva se stávají velmi populární v současnosti kvůli požadavkům na snížení emisí CO2. FBC ash je snadno dostupné, i když ne snadno využitelných surovin. Protože má několik hydraulické vlastnosti, může vytvořit hydraulické pojivo s vápnem. V této práci byly připraveny směsi hořčíku a FBC popela z filtrů a z lůžka. Hlavním kritériem byl hydraulický modul. Fyzikálně mechanické vlastnosti byly pozorovány a byly porovnány s referenční vzorek, což byl Hydraulické vápno z průmyslové výroby. Připravené hydraulická vápna dosáhnout podobné parametry jako komerčně vyráběných hydraulická vápna nebo nižší cementy pevnostní třídy.

This work is focused on the possibilities of utilization of ashes from fluidized bed combustion, i.e. FBC ashes, for the manufacturing of hydraulic lime. Alternative hydraulic binders are becoming very popular in the present due to requirements on reducing CO2 emissions. FBC ash is an easily available, though not easily usable raw material. Because it has several hydraulic characteristics, it can create a hydraulic binder together with lime. Mixtures of hydrated lime and FBC ash from filters and from a bed were prepared in this work. The main criterion was the hydraulic modulus. The physico-mechanical properties were observed and were compared with the reference sample, which was hydraulic lime from industrial production. The prepared hydraulic limes achieved similar parameters as commercially manufactured hydraulic limes or lower strength class cements., Tato práce je zaměřena na možnosti využití popela ze spalování ve fluidním loži, tj FBC popel, pro výrobu Hydraulické vápno. Alternativní hydraulická pojiva se stávají velmi populární v současnosti kvůli požadavkům na snížení emisí CO2. FBC ash je snadno dostupné, i když ne snadno využitelných surovin. Protože má několik hydraulické vlastnosti, může vytvořit hydraulické pojivo s vápnem. V této práci byly připraveny směsi hořčíku a FBC popela z filtrů a z lůžka. Hlavním kritériem byl hydraulický modul. Fyzikálně mechanické vlastnosti byly pozorovány a byly porovnány s referenční vzorek, což byl Hydraulické vápno z průmyslové výroby. Připravené hydraulická vápna dosáhnout podobné parametry jako komerčně vyráběných hydraulická vápna nebo nižší cementy pevnostní třídy.

Presented work is a part of an experiment where limestone is partially replaced by fluidized fly ash during cement manufacturing. Hydration of this type of cement is connected to formation of AFt phases – thaumasite and ettringite that cause serious damage to cement stone. Thaumasite (CaSiO3·CaCO3·CaSO4·15H2O) is less known and less common. It forms especially at lower temperatures. During its growth C-S-H phases are built into thaumasite unite cell, therefore, cement stone decomposes. To preclude thaumasite formation, further research of this mineral is necessary; therefore, its synthetic preparation in sufficient quality is important. The aim of this work was to verify several routes for thaumasite synthetic preparation. In the beginning, burning of mixtures prepared on stoichiometric proportions of compounds in thaumasite was done then two methods used in literature were tried and in the end a new method based on main calcium silicate phases was realized., Předkládaná práce je součástí experimentu kde se vápenec částečně nahrazuje fluidním popílkem při výrobě cementu. Hydratace tohoto druhu cementu vede k vzniku AFt fází – thaumasit a ettringit, které způsobují vážné škody na cementovém kameni. Thaumasite (CaSiO3· CaCO3· CaSO4·15H2O) je méně známý a méně častý.

Due to ecological overloading decrease, industrial by-products are utilized. Fly ash also belongs among these by-products. In Portland-composite cements, the high-temperature fly ash is applied nowadays, but fluidized bed combustion fly ash (FBC fly ash) is not used. The reason is that the FBC fly ash hydrates to form an undesirable ettringite, C3A.3CaSO4.32H2O. Decomposition temperature of ettringite in ambient conditions is most often mentioned in a range of 50 °C to 110 °C. In order to assess the ettringite long-term stability, ettringite was synthesized by hydration of mineral yeelimite, 3CaO.3Al2O3.CaSO4. The aim of this paper is long-term observation of the hydration of yeelimite in environment of saturated water vapour and examination of how stable the products of hydration are under given conditions. Raw materials for preparation of yeelimite were gypsum, limestone and corundum, weighed according to stoichiometric ratio of yeelimite. The mixture was heated at temperature of 1200 °C, soak 3 hours. After quenching and grinding, yeelimite was hydrated with a water-yeelimite ratio of 0.3. The system was cured as pastes and stored in conditions at laboratory temperature and in settings of saturated water vapour (100% R.H.). In order to follow the progress of synthesis regularly, namely up to age of 180 days of hydration, X-ray diffraction (XRD) was chosen using diffractometer Empyrean PANalytical (CuK-alpha). Based on the XRD patterns, only minor part of ettringite was formed, whilst a majority of yeelimite was preserved. It has been found that ettringite was not the only one product of yeelimite hydration. From an age of 20 days of hydration, a small amount of monosulfate was identified, whose quantity rose gradually. Especially at later ages of hydration, transformation of ettringite into monosulfate was observed.

Although the stability of ettringite has been the subject of much research, the solution is not yet fully clear. Ettringite is generally considered to be stable up to a temperature of 110°C; however, some investigators claimed that ettringite may already decompose at even ambient temperatures. To prove these statements, ettringite was prepared by the hydration of ye’elimite, 3CaO·3Al2O3·CaSO4, and the system stored at laboratory temperature in two environments: in laboratory settings and in an environment of saturated water vapour., Stabilita ettringitu není zcela popsána, přestože byla předmětem mnoha výzkumů. Ettringite je obecně považován za stabilní do teploty 110 ° C; Někteří autoři však tvrdí, že se ettringite může již rozkládat již při běžných teplotách. K prokázání těchto tvrzení, byl připraven ettringit hydratací ye'elimitu, 3CaO·3Al2O3· CaSO4. Vzorky byly uloženy při laboratorní teplotě ve dvou prostředích: v laboratorním prostředí a v prostředí nasycené vodní páry.

Presented work is a part of an experiment where limestone is partially replaced by fluidized fly ash during cement manufacturing. Hydration of this type of cement is connected to formation of AFt phases – thaumasite and ettringite that cause serious damage to cement stone. Thaumasite (CaSiO3·CaCO3·CaSO4·15H2O) is less known and less common. It forms especially at lower temperatures. During its growth C-S-H phases are built into thaumasite unite cell, therefore, cement stone decomposes. To preclude thaumasite formation, further research of this mineral is necessary; therefore, its synthetic preparation in sufficient quality is important. The aim of this work was to verify several routes for thaumasite synthetic preparation. In the beginning, burning of mixtures prepared on stoichiometric proportions of compounds in thaumasite was done then two methods used in literature were tried and in the end a new method based on main calcium silicate phases was realized., Předkládaná práce je součástí experimentu kde se vápenec částečně nahrazuje fluidním popílkem při výrobě cementu. Hydratace tohoto druhu cementu vede k vzniku AFt fází – thaumasit a ettringit, které způsobují vážné škody na cementovém kameni. Thaumasite (CaSiO3· CaCO3· CaSO4·15H2O) je méně známý a méně častý.

Due to ecological overloading decrease, industrial by-products are utilized. Fly ash also belongs among these by-products. In Portland-composite cements, the high-temperature fly ash is applied nowadays, but fluidized bed combustion fly ash (FBC fly ash) is not used. The reason is that the FBC fly ash hydrates to form an undesirable ettringite, C3A.3CaSO4.32H2O. Decomposition temperature of ettringite in ambient conditions is most often mentioned in a range of 50 °C to 110 °C. In order to assess the ettringite long-term stability, ettringite was synthesized by hydration of mineral yeelimite, 3CaO.3Al2O3.CaSO4. The aim of this paper is long-term observation of the hydration of yeelimite in environment of saturated water vapour and examination of how stable the products of hydration are under given conditions. Raw materials for preparation of yeelimite were gypsum, limestone and corundum, weighed according to stoichiometric ratio of yeelimite. The mixture was heated at temperature of 1200 °C, soak 3 hours. After quenching and grinding, yeelimite was hydrated with a water-yeelimite ratio of 0.3. The system was cured as pastes and stored in conditions at laboratory temperature and in settings of saturated water vapour (100% R.H.). In order to follow the progress of synthesis regularly, namely up to age of 180 days of hydration, X-ray diffraction (XRD) was chosen using diffractometer Empyrean PANalytical (CuK-alpha). Based on the XRD patterns, only minor part of ettringite was formed, whilst a majority of yeelimite was preserved. It has been found that ettringite was not the only one product of yeelimite hydration. From an age of 20 days of hydration, a small amount of monosulfate was identified, whose quantity rose gradually. Especially at later ages of hydration, transformation of ettringite into monosulfate was observed.

Presented work is a part of an experiment where limestone is partially replaced by fluidized fly ash during cement manufacturing. Hydration of this type of cement is connected to formation of AFt phases – thaumasite and ettringite that cause serious damage to cement stone. Thaumasite (CaSiO3·CaCO3·CaSO4·15H2O) is less known and less common. It forms especially at lower temperatures. During its growth C-S-H phases are built into thaumasite unite cell, therefore, cement stone decomposes. To preclude thaumasite formation, further research of this mineral is necessary; therefore, its synthetic preparation in sufficient quality is important. The aim of this work was to verify several routes for thaumasite synthetic preparation. In the beginning, burning of mixtures prepared on stoichiometric proportions of compounds in thaumasite was done then two methods used in literature were tried and in the end a new method based on main calcium silicate phases was realized., Předkládaná práce je součástí experimentu kde se vápenec částečně nahrazuje fluidním popílkem při výrobě cementu. Hydratace tohoto druhu cementu vede k vzniku AFt fází – thaumasit a ettringit, které způsobují vážné škody na cementovém kameni. Thaumasite (CaSiO3· CaCO3· CaSO4·15H2O) je méně známý a méně častý.