Compressive strength and microstructure of alkali-activated mortars with high ceramic waste content

The present work investigated alkali-activated mortars with high ceramic waste contents. Tile ceramic waste (TCW) was used as both a recycled aggregate (TCWA) and a precursor (TCWP) to obtain a binding matrix by the alkali-activation process. Mortars with natural siliceous (quartz) and calcareous (limestone) aggregates, and with other ceramic waste materials (red clay brick RCB and ceramic sanitaryware CSW waste), were also prepared for comparison purposes. Given the lower density and higher water absorption values of the ceramic aggregates, compared to the natural ones, it was necessary to adapt the preparation process of the recycled mortars by presaturating the aggregate with water before mixing with the TCWP alkali-activated paste. Aggregate type considerably determined the mechanical behaviour of the samples cured at 65 °C for 3 days. The mortars prepared with the siliceous aggregate presented poor mechanical properties, even when cured at 65 °C. The behaviour of the limestone aggregate mortars depended heavily on the applied curing temperature and, although they presented the best mechanical properties of all those cured at room temperature, their compressive strength reached a maximum when cured at 65 °C, and then decreased. The mechanical properties of the mortars prepared with TCWA progressively increased with curing time (53 MPa at 65 °C for 28 days). An optimum 50 wt% proportion was observed for the limestone/TCWA mortars (≈43 MPa, 3 days at 65 °C), whereas the mechanical properties of that prepared with siliceous particles (10 MPa) progressively increased with the TCWA content, up to 100 wt% substitution (23 MPa). Limestone particles interacted with the binding matrix, and played an interesting beneficial role at the 20 °C curing temperature, with a slight reduction when cured long term (28 days) at 65 °C. The results demonstrated a potential added value for these ceramic waste materials.     

Eco-friendly concretes with reduced water and cement contents — Mix design principles and laboratory tests

The major environmental impact of concrete is caused by CO₂-emissions during cement production. Great potential for reducing the impact is seen especially for concretes with normal strength. The use of superplasticizers and highly reactive cements as well as optimization of particle-size distribution and reduction in water content allows a significant reduction in Portland cement clinker in the concrete. Essential is the addition of mineral fillers (e.g. limestone powder) to provide an optimal paste volume. In addition, the already practicable substitution of secondary raw materials like fly-ash or furnace-slag for cement clinker is an appropriate option which is however limited by the availability of these resources.In several test series the fresh and hardened concrete properties of concretes with reduced water and cement contents were investigated, especially their workability, strength development, design-relevant mechanical properties as well as durability aspects such as carbonation. It was shown that concretes with cement clinker and slag contents as low as 150 kg/m³ were able to meet the usual requirements of workability, compressive strength (approx. 40 N/mm²) and mechanical properties. The carbonation depth of concretes with 150-175 kg/m³ clinker and slag was equal or lower than the depth of conventional reference concretes for exterior structures. The ecological advantages were identified, using environmental performance evaluation. A reduction of up to 35% in environmental impact was calculated compared with conventional concrete and of more than 60% with granulated blast-furnace slag. Practical application was verified by means of full-scale tests in a precast and ready-mix concrete plant.     

Preparation and characterization of sintered ceramics made with spent foundry olivine sand and clay

Two different types of clay (a yellow and a red clay) were used to prepare two sets of materials containing spent foundry olivine sand. They were blended by attrition milling in varying proportions to obtain powders of different composition.All mixtures were dried, sieved, uniaxially pressed into specimens and air sintered for 1 h at temperatures ranging from 900 to 1140 °C. The resulting materials were characterized by density, water absorption, shrinkage, crystallographic composition, microstructure and physico-mechanical properties. Mechanical and crystallographic properties were determined on samples fired at 1040 °C in order to compare materials with similar characteristics. It was observed that, after sintering, all compositions show the presence of the glassy phase which surrounds the crystalline grains and the set of materials prepared using the red clay displayed best overall behavior. XRD analysis performed on the free surface of the fired samples did not show the presence of compounds containing heavy metals present in the starting materials.     

Microstructural characterization of ITZ in blended cement concretes and its relation to transport properties

The improvements in the overall performances of concrete with blended materials were often ascribed to the modification of its hardened paste in general. In this paper, the effects of limestone filler (LF) and slag (GGBS) on chloride migration and water absorption of concretes with systematically varied aggregate properties were evaluated from the view point of ITZ by using BSE image, EDS, and MIP analysis. It was found that the incorporation of moderate amount of LF and GGBS would compact the microstructure of both ITZ and bulk cement matrix. The reduction in the pore volume (> 100 nm) contributes to the largest decrease in total porosity. Additionally, incorporating GGBS avoids the build-up of Ca(OH)₂ within ITZ and provides a more uniform microstructure. The mechanism for the improvement in limiting water and ions penetration was found to be mainly related to the densification of bulk cement matrix rather than the modification of ITZ.     

Hydrophilic modification of polyacrylonitrile membranes by oxyfluorination

The surface of polyacrylonitrile (PAN) membranes was modified by oxyfluorination with various conditions to improve its wettability. The membranes were characterized in terms of morphology, structure, hydrophilicity, and membrane performance. The properties and functional groups on the surface of PAN membranes were investigated by contact angle, SEM, ATR-IR and XPS. And permeability of PAN membranes was compared by permeating pure water flux through membrane surface under 100, 150 and 200 kPa pressure. Oxyfluorination introduced oxygen contained functional groups such as the carboxylic acid groups that help increment of wettability on the surface of PAN membrane. Water flux of oxyfluorinated PAN UF membrane increased 20% at pure water permeation pressure 200 kPa compared to that of untreated PAN UF membrane.     

Carbonaceous–siliceous composite materials as immobilization support for lipase from Alcaligenes sp.: Application to the synthesis of antioxidants

Two carbonaceous–siliceous composite materials, produced by hydrothermal and carbonization processes, were evaluated as immobilization support for lipase from Alcaligenes sp. These materials exhibited similar chemical characteristics but their carbon content and porous characteristics were different, which explain the catalytic behavior and stability of the biocatalysts immobilized on them. Higher activity and immobilization selectivity was achieved with the microporous material that had higher carbon content. The lipase immobilized on the mesoporous material had a higher thermal stability at 55 °C, pH 7.0 or at 40 °C in tert-butanol, simulating the reaction conditions required for organic synthesis. Both biocatalysts were tested in the synthesis of palmitoyl ascorbate and they were compared with the commercial biocatalyst QLC. The synthesis conversions with the lipase immobilized in mesoporous materials and with the biocatalyst QLC were similar (50%), but only the former could be reused. These are promising biocatalysts for industrial applications.     

Synthesis of polylactide/clay composites using structurally different kaolinites and kaolinite nanotubes

Polymer/clay nanocomposites receive much attention due to their interesting mechanical and thermal properties. Currently, the vast majority of plastics are made from petroleum-based synthetic polymers that do not degrade in a natural environment and their disposal poses a serious problem. An environmentally-conscious alternative is to design polymer nanocomposites that are biodegradable.In the present work the synthesis and properties of novel polymer/clay nanocomposites based on biodegradable polymer-polylactide (PLA) were investigated. Kaolinite nanotubes obtained by an intercalation/deintercalation method as well as platey kaolinites of different structural orders were used as fillers. Mechanical properties of composites (tensile strength (S_U) and Young's modulus (E)) were measured. The surface of the formed polymer derivatives was examined by AFM (Atomic Force Microscopy). The structural characterization was carried out using infrared spectroscopy (IR). Composites surface wettability was studied by measuring the water contact angle.The mechanical tests revealed that both S_U and E values increased significantly after addition of the nano-filler in comparison to the pure PLA. Regardless of the filler content the increase of S_U and E values was higher in the case of the nanotubular kaolinite. In particular, a threefold increase of the E value was noticed. For the most homogeneous kaolinite nanotubes/PLA nanocomposite S_U increased from ~ 29 MPa (pure PLA) to ~ 43 MPa, while E increased from ~ 0.7 GPa (pure PLA) to ~ 2.3 GPa. These mechanical parameters were comparable with the ones measured for polypropylene (S_U = 40 MPa; E = 1.5–2.0 GPa) and polystyrene (S_U = 40 MPa; E = 3.0–3.5 GPa). Differential IR spectra of the nanocomposites indicated an interaction of kaolinites inner surface hydroxyls with PLA which was confirmed by an intensity decrease of a band at ~ 3690 cm^? 1. The presence of highly dispersed nanotubular kaolinite particles in the polymer matrix which contributed to the improvement of PLA mechanical properties was observed using AFM. The contact angle measurements showed that the addition of kaolinites led to changes of wettability, yet the synthesized materials still possessed hydrophilic surfaces.     

Wettability of colloid-imprinted carbons by contact angle kinetics and water vapor sorption measurements

As an example of nanoporous carbon materials, colloid-imprinted carbons (CICs) have been reported to have promising properties for use in a variety of applications. However, the wettability of these carbons has not been investigated as yet. In this work, CICs with different pore sizes (20–50 nm) were synthesized and heat treated at 1500 °C under a N₂ atmosphere. Heat treatment was found to not alter the nanoporous structure of these carbons, but did significantly decrease their oxygen content. Contact angle kinetics (CAK) and water vapor sorption (WVS) experiments were carried out to determine the wettability of the CICs, before and after heat treatment, showing that the as-synthesized CICs surfaces are much more hydrophilic when compared to commercial carbon black (Vulcan carbon, VC). The high hydrophilicity of the CICs is likely due to their high surface-specific oxygen atomic density (∼10 μmol m⁻²). Further heat treatment significantly decreases the hydrophilicity of CICs because of the removal of oxygen atoms from their surfaces, as also reflected by their cyclic voltammetric response in acidic solutions.     

Vitrification of a waste water flocculate from a petroleum catalyst manufacturer

Chemical and mineral compositions of a waste water flocculate generated in a manufacturer producing fluidized-bed catalytic cracking catalysts were analyzed. The flocculate was then calcined at 1200–1350 °C. X-ray diffraction analysis results indicate that the flocculate can be directly vitrified at 1350 °C without the addition of any other ingredients. The density and chemical durability of the directly vitrified product are comparable with commercial soda-lime-silicate glasses. However, the viscosity of directly vitrified glass melt was very high. Thus, the refining and shaping of the glass melt were difficult. With the addition of minerals such as limestone, dolomite and fluorite, workable glasses could be formed. The influence of MgO on the structure and properties of the obtained glasses is discussed. Results show that the density and hardness of the glass increase with the increase of MgO, whereas the chemical durability, transition and crystallization temperatures decrease. The present study provides a general way to utilize waste water flocculates in glass production.     

Novel high-resistance clinkers with 1.10 < CaO/SiO2 < 1.25: production route and preliminary hydration characterization

New amorphous calcium silicate binders, hydraulically active, were produced by a process consisting in fully melting and rapid cooling of a mixture of typical raw materials (limestone, sand, fly-ash and electric furnace slag) with overall CaO/SiO₂ molar ratios (C/S) comprised between 1.1 and 1.25. Pastes were produced from these materials by mixing them with water in a water/binder ratio of 0.375. Compressive strength was determined at the ages of 7, 28 and 90 days and the hydration of these pastes was followed during this period by XRD, FTIR and ²⁹Si MAS-NMR. Tobermorite-like structures with low C/S and semi-crystalline character were observed to develop upon hydration of these new amorphous calcium silicate hydraulic binders. Moreover, no Portlandite was formed during hydration of these materials. The maximum compressive strength after 90 days is above 40 MPa. TGA was performed in order to determine the amount of structural water present in the pastes and their content related to the amount of hydrated products obtained. The relation between compressive strength and the amount of hydration products was investigated and some considerations about the mechanical properties of the hydration products and paste microstructure were inferred.     

Tribological properties of polymer composites with diamond-like carbon flakes

Composites of epoxy resin with diamond-like carbon (DLC) flakes were fabricated. The DLC flakes were prepared from a DLC film deposited by chemical vapor deposition on an aluminum substrate. The tribological properties of composites were evaluated in air and water environments using a reciprocating friction tester and an AISI 440C mating ball. The friction coefficient of the epoxy composite decreased from 0.90 to 0.69 in air and from 0.71 to 0.29 in water with the addition of DLC flakes. The specific wear rate of the composite also decreased from 5 × 10^? 5 to 7 × 10^? 6 mm³/N m in air and from 4 × 10^? 5 to 4 × 10^? 6 mm³/N m in water. In contrast, the wear of the mating ball increased. Furthermore, the tribological properties of DLC flakes as an additive in water were evaluated. The suspension of powdered DLC in water reduced the friction coefficient of epoxy resin against the AISI 440C mating ball. Furthermore, the wear of the resin was negligibly small, although severe abrasive wear on the mating ball was observed.     

Effect of oxygen plasma treatment on non-thrombogenicity of diamond-like carbon films

The non-thrombogenicity of oxygen-plasma-treated DLC films was investigated as surface coatings for medical devices. DLC films were deposited on polycarbonate substrates by a radio frequency plasma enhanced chemical vapor deposition method using acetylene gas. The deposited DLC films were then treated with plasma of oxygen gas at powers of 15 W, 50 W, and 200 W. Wettability was evaluated by water contact angle measurements and the changes in surface chemistry and roughness were examined by X-ray photoelectron spectroscopy and atomic force microscope analysis, respectively. Each oxygen-plasma-treated DLC film exhibited a hydrophilic nature with water contact angles of 11.1°, 17.7° and 36.8°. The non-thrombogenicity of the samples was evaluated through the incubation with platelet-rich plasma isolated from human whole blood. Non-thrombogenic properties dramatically improved for both 15 W- and 50 W-oxygen-plasma-treated DLC films. These results demonstrate that the oxygen plasma treatment at lower powers promotes the non-thrombogenicity of DLC films with highly hydrophilic surfaces.     

The effects of the molecular weight and structure of polycarbonatediols on the properties of waterborne polyurethanes

A series of waterborne polyurethanes (WPUs) were synthesized by a pre-polymer process from isophorone diisocyanate, 1,6-hexamethylene diisocyanate and polycarbonatediol with varying molecular weight (1000–2000 Da) and molecular structure (copolycarbonate and homopolycarbonate). The effect of polycarbonatediols on the performance of the emulsion was studied by means of apparent viscosity, particle size distribution and Zeta potential analysis. Fourier transform infrared spectroscopy, thermal gravimetric analysis, differential scanning calorimetry, X-ray diffraction, dynamic mechanical analysis, physical and mechanical measurements and water droplet contact angle tests were employed to characterize the thermal stability, crystallinity, low temperature flexibility, physical and mechanical properties and wettability of the films derived from the emulsions. The results indicated that WPU dispersions with mean particle size in the range of 50–70 nm and Zeta potential value about −50 mV displayed excellent storage stability. It was found that the mean particle size, thermal stability, crystallinity, low temperature flexibility, mechanical properties and hydrophobicity increased and the particle distribution decreased with the increase of molecular weight of the polycarbonatediols. Moreover, copolycarbonate-based WPUs showed higher crystallinity of hard segments, thermal stability and wettability than the homopolycarbonate-based ones.     

HF etching effect on sandblasted soda-lime glass properties

Our objective in this work is to study the HF etching chemical treatment effect on the mechanical and optical properties of soda-lime glass eroded with 200 g fixed sand mass. We followed the evolution of these properties in relation to the chemical attack duration.The results show a clear improvement of the measured properties. The strength of the eroded samples is 44.23 ± 0.91 MPa. It increases up to 57.73 ± 1.76 MPa after 15 min of treatment and reaches 181.43 ± 23.69 MPa after 1 h. This last value is much higher than the as received glass strength (117.5 ± 10.48 MPa). The optical transmission of the eroded samples is about 18.5%. During the first 2 min of the chemical treatment, an important drop of the optical transmission (12%) was observed. However, improvement of the transmission was achieved for longer chemical treatment durations. After 8 h of treatment, the optical transmission increases up to 57%. Microscopic observations show that the HF attack causes the opening and the blunting of the surface cracks. In general, the surface state is improved during the chemical treatment.     

Optimization of the technological properties of porcelain tile bodies containing rice straw ash using the design of experiments methodology

This study examines the effects of replacing fluxing and filler materials with rice straw ash (RSA) in manufacturing porcelain stoneware tile, using the design of experiments (DOE) methodology. The results of the characterization were used to obtain statistically significant, valid regression equations, relating the technological properties of the dried and fired test pieces to the raw materials content in the unfired mixtures. The regression models were analysed in relation to the X-ray diffraction and scanning electron microscopy results and used to determine the most appropriate combinations of traditional raw materials and RSA to produce porcelain stoneware tiles with specific technological properties. The studied range of tile body compositions: clay (40 wt%), feldspar (20–50 wt%), feldspathic sand (5–20 wt%), and RSA (0–25 wt%) was shown to be appropriate for porcelain stoneware tile manufacture.     

Experimental investigation of the degradation rate of adipic acid in wet flue gas desulphurisation plants

The aim of this work is to study the degradation rate of adipic acid in wet FGD plants using forced oxidation. The investigation is experimentally demanding because the degradation rate must be studied under realistic conditions present in pilot plants or industrial plants only. This is the first systematic investigation including both chemical and biological degradation. The influence on the degradation rate of adipic acid was studied: The concentration of adipic acid (0–2100 mg/l), trace-metals, Cl⁻ (0–50 g/l), pH (4.7 and 5.4), and temperature (32, 42 and 50 °C). Furthermore, the degradation rate of adipic acid was examined in two types of limestone/gypsum slurry: one based on limestone, distilled water and flue gas from natural gas combustion, the other on slurry liquid taken from the wet FGD plant of a full-scale power plant (coal combustion) with limestone subsequently added. The first order rate constant, using slurry based on natural gas combustion, was estimated to 0.60±0.10 day⁻¹ which is more than twice the value of the rate constant estimated from experiments based on slurry from the full-scale wet FGD plant (0.25±0.10 day⁻¹). Both types of slurry were examined for biological activity. In the slurry based on natural gas combustion no biological activity was found. Independent laboratory tests showed that biological activity contributed to the degradation rate of adipic acid in the slurry liquid from the full-scale wet FGD plant, though the effect could not be quantified. Analysis of the slurries for selected trace metals showed significantly higher concentrations in the slurry from the full-scale plant. It was found that increasing concentrations of trace metals and chloride inhibits the chemical degradation of adipic acid.     

Hydration of a low-alkali CEM III/B–SiO2 cement (LAC)

The hydration of a low-alkali cement based on CEM III/B blended with 10 wt.% of nanosilica has been studied. The nanosilica reacted within the first days and 90% of the slag reacted within 3.5 years. C-S-H (Ca/Si ~ 1.2, Al/Si ~ 0.12), calcite, hydrotalcite, ettringite and possibly strätlingite were the main hydrates. The pore water composition revealed ten times lower alkali concentrations than in Portland cements. Reducing conditions (HS^?) and a pH value of 12.2 were observed. Between 1 month and 3.5 years of hydration more hydrates were formed due to the ongoing slag reaction but no significant differences in the composition of the pore solution or solid phase assemblage were observed.On the basis of thermodynamic calculations it is predicted that siliceous hydrogarnet could form in the long-term and, in the presence of siliceous hydrogarnet, also thaumasite. Nevertheless, even after 3.5 year hydration, neither siliceous hydrogarnet nor thaumasite have been observed.     

Influence of oxygen plasma treatment parameters on poly(vinylidene fluoride) electrospun fiber mats wettability

Electrospun poly(vinylidene fluoride) (PVDF) fiber mats find applications in an increasing number of areas, such as battery separators, filtration and detection membranes, due to their excellent properties. However, there are limitations due to the hydrophobic nature and low surface energy of PVDF. In this work, oxygen plasma treatment has been applied in order to modify the surface wettability of PVDF fiber mats and superhydrophilic PVDF electrospun membranes have been obtained. Further, plasma treatment does not significantly influences fiber average size (∼400 ± 200 nm), morphology, electroactive β-phase content (∼80–85%) or the degree of crystallinity (X_c of 42 ± 2%), allowing to maintain the excellent physical–chemical characteristics of PVDF. Plasma treatment mainly induces surface chemistry modifications, such as the introduction of oxygen and release of fluorine atoms that significantly changes polymer membrane wettability by a reduction of the contact angle of the polymer fibers and an overall decrease of the surface tension of the membranes.     

Development of a new rapid,relevant and reliable (R3) test method to evaluate the pozzolanic reactivity of calcined kaolinitic clays

The present paper introduces a new rapid, relevant and reliable (R³) test to predict the pozzolanic activity of calcined clays with kaolinite contents ranging from 0 to 95%. The test is based on the correlation between the chemical reactivity of calcined clays in a simplified system and the compressive strength of blends in standard mortar. The simplified system consists of calcined clay portlandite and limestone pastes with sulfate and alkali levels adjusted to reproduce the reaction environment of hydrating blended cements. The pastes were hydrated for 6 days at 20 °C or for 1 day at 40 °C. The chemical reactivity of the calcined clay can be obtained first by measurement of the heat release during reaction using isothermal calorimetry and second by bound water determination in a heating step between 110 °C and 400 °C.Very good correlations were found between the mortar compressive strength and both measures of chemical reactivity.     

13C chemical shift anisotropies for carbonate ions in cement minerals and the use of 13C, 27Al and 29Si MAS NMR in studies of Portland cement including limestone additions

¹³C isotropic chemical shifts and chemical shift anisotropy parameters have been determined for a number of inorganic carbonates relevant in cement chemistry from slow-speed ¹³C MAS or ¹³C{¹H} CP/MAS NMR spectra (9.4 T or 14.1 T) for ¹³C in natural abundance. The variation in the ¹³C chemical shift parameters is relatively small, raising some doubts that different carbonate species in Portland cement-based materials may not be sufficiently resolved in ¹³C MAS NMR spectra. However, it is shown that by combining ¹³C MAS and ¹³C{¹H} CP/MAS NMR carbonate anions in anhydrous and hydrated phases can be distinguished, thereby providing valuable information about the reactivity of limestone in cement blends. This is illustrated for three cement pastes prepared from an ordinary Portland cement, including 0, 16, and 25 wt.% limestone, and following the hydration for up to one year. For these blends ²⁹Si MAS NMR reveals that the limestone filler accelerates the hydration for alite and also results in a smaller fraction of tetrahedrally coordinated Al incorporated in the C-S-H phase. The latter result is more clearly observed in ²⁷Al MAS NMR spectra of the cement–limestone blends and suggests that dissolved aluminate species in the cement–limestone blends readily react with carbonate ions from the limestone filler, forming calcium monocarboaluminate hydrate.