Heparin is the most common anticoagulant used in clinical practice but shows some downsides such as short half-life (for the high molecular weight heparin) and secondary effects. On the other hand, ...its low molecular weight analogue cannot be neutralized with protamine, and therefore cannot be used in some treatments. To address these issues, we conjugated polyethylene glycol (PEG) to heparin reducing end (end-on) via oxime ligation and studied the interactions of the conjugate (Hep-b-PEG) with antithrombin III (AT) and protamine. Isothermal titration calorimetry showed that Hep-b-PEG maintains the affinity to AT. Dynamic light scattering demonstrated that the Hep-b-PEG formed colloidal stable nanocomplexes with protamine instead of large multi-molecular aggregates, associated with heparin side effects. The in vitro (human plasma) and in vivo experiments (Sprague Dawley rats) evidenced an extended half-life and higher anticoagulant activity of the conjugate when compared to unmodified heparin.
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•Surface chemistry controls rheology in alkali-activated slag cements.•Particle–particle interactions and gelation influenced by activator nature.•Yield stress depends on square of ...zeta potential.•Silicate and hydroxide activators differ notably in behavior.•Influence of pH on fresh paste chemistry is indirect.
Ground granulated blast furnace slag can react with an alkaline activating solution to form a cement-like binder based on a calcium–sodium aluminosilicate gel, which is a potential alternative to Portland cement in many applications. This study provides new information regarding the effect of activator type and dosage on rheology by monitoring changes in pH, particle surface charge (zeta potential), and heat evolution in the early stages of the reaction process. Sodium and potassium hydroxide silicate solutions, at two different M2O (M: Na, K) dosages, are used here as activators. Alkali hydroxide activators cause a significant increase in the yield stress of an activated slag paste, especially at higher dosages as reactions take place rapidly, while within the same timeframe, the yield stress of the silicate activated slag remains unchanged. The results imply a direct relationship between a higher reaction rate with the formation of solid products (causing both spatial blockage effects and consumption of free water), and a rapid yield stress increase. However, the dependence of reaction rate on pH for different alkali-activated pastes is, at most, indirect. All activators induce a highly alkaline pH and a concentrated electrolyte solution environment in the fluid paste. As a result of complexation of poorly-hydrated ions on the surfaces of the particles, the magnitude of the zeta potential increases. A direct relationship is observed between the dosage of the activators and zeta potential. A zeta potential further from neutrality generally reduces yield stress by increasing the magnitude of double layer repulsive forces, with the exception of a higher dosage of silicate activator, which shows an indication of some attractive double layer forces.
•The concentration of activator influences the kinetic of reaction of slag.•The addition of MK to AAS increases the total setting time.•At high activator concentrations addition of MK increased ...strength.•At high activator concentrations addition of MK reduced accelerated carbonation.
The effects of activator dose on the properties of alkali-activated slag/metakaolin blends, were studied in fresh and hardened states: heat evolution, strength and accelerated carbonation. High activator concentrations affect the slag dissolution rate, reducing compressive strength when this is the sole precursor. An increased activator concentration favours metakaolin reaction, promoting high strengths and reduced permeability. Metakaolin addition, and increased activator concentrations reduce the susceptibility to carbonation, associated with the refinement of the pore network under extended CO2 exposure. The effect of adding an aluminosilicate precursor to an alkali-activated slag system is strongly dependent on the activator concentration.
Understanding the role of retarder on the chemical nature and molecular architecture of hydrating cement paste is essential for engineering oil well cements with additives. Here, synchrotron X-ray ...and total neutron scattering with pair distribution function (PDF) analysis were performed in combination with calorimetry and nuclear magnetic resonance (NMR) to examine the retarder effect in hydrating tri-calcium silicate (C3S) and Class G oil well cement paste. Primarily, the retarder, Diethylenetriamine pentamethylene phosphonic acid (DTPMP) influenced the hydration by affecting the Ca-O and Ca-Si pair correlation providing evidence of calcium playing a predominant role in the retardation process. Secondary effects related to Calcium-Silicate-Hydrate (C-S-H) nuclei poisoning influencing the suppression of calcium hydroxide precipitation were observed. Here, these findings provide insights into the retardation mechanism of hydrating cement paste influenced by calcium depletion when subjected to phosphonate retarders.
This study aimed to investigate the application of isothermal calorimetry as technique for monitoring microparticles oxidation produced by particles from gas saturation solution (PGSS) technique. ...Microparticles were obtained by mixing linseed oil (9.1 g/100 g) with glycerol stearate (90.9 g/100 g). The process was carried out at 10 MPa, 55 °C for 30 min. To enhance microparticles oxidative stability, β-carotene was also added to the formulation (0.4 up to 1.6 mg/g of oil). The results showed that the fatty acid profile of the oil did not change after the encapsulation process. From the isothermal calorimetry traces, it was possible to determine the induction time (τIC) and the rates of oxidation during the inhibited (Rinh) and uninhibited (Runi) period. The microencapsulation by PGSS significantly (p < 0.05) increased τIC values of microparticles compared to the bulk oil, which resulted equal to 32 ± 1 × 104 s and 10.2 ± 2 × 104 s, respectively. On the other side, Rinh significantly decreased confirming the higher microparticles oxidative stability. β-carotene addition enhanced the oxidative stability proportionally to the concentration of the added antioxidant. At the end of the oxidation, the 3-OH-beta-apo-11-carotenal and the 3-OH-beta-apo-carotenone compounds derived from β-carotene degradation were detected.
•Isothermal calorimetry monitored microcapsules rich in unsaturated fatty acids.•The kinetics parameters were evaluated from the calorimetric traces.•β-carotene addition improved microcapsules oxidative stability.
•Isothermal calorimetry measurements are used to evaluate fly ash hydration.•The approach presented decouples the physical and chemical effects of fly ash.•Inert fillers are used to replace the fly ...ash fraction.
Fly ash is frequently used as a replacement for cement in concrete. However, questions remain regarding the influence that fly ash has on the hydration of cement. This paper examines physical aspects (e.g., surface nucleation, cement particle spacing) and chemical aspects (e.g., pozzolanic and hydraulic reactions) of the fly ash and cement in mixtures containing high volumes of fly ash. In addition to using fly ash, a chemically inert filler was used consisting of a blend of fine silica sands with approximately the same particle size distribution as that of the fly ash. The paper compares reactivity results from 1) cement, 2) cement-fly ash and 3) cement-inert filler systems. Isothermal calorimetry measurements are used to quantitatively evaluate the role played by the fly ash in hydration of high volume fly ash mixtures. The results provide a decoupling of the physical and chemical effects of high volume fly ash on cement hydration.
Past research has shown that the specific heat capacity and thermal conductivity may be influenced by the battery's temperature and/or its state-of-charge (SOC). However, there has not been any clear ...relationship uncovered between these test parameters and the thermophysical properties of the battery. Therefore the objective of this research is to measure the thermophysical properties of a Lithium Iron Phosphate (LFP) pouch cell at different surface temperatures and SOC levels. An isothermal calorimeter is used to measure the specific heat capacity at various temperature points and SOC levels. This same instrument is then reconfigured to perform as a heat flow meter apparatus and yield cross-plane thermal conductivity measurements. A commercially available 14 A h pouch cell was used as the test specimen. On average, the specific heat capacity of the cell increases slightly with temperature but remains independent of SOC. The behavior of the cross-plane thermal conductivity is opposite in nature. Its value increases with decreasing SOC but is largely unaffected by temperature. A lithium-ion battery with electrolyte has nearly twice the thermal conductivity of the dry cell version without electrolyte.
•The specific heat capacity of the LFP battery increases slightly with temperature.•The specific heat capacity of the LFP battery is independent of SOC.•The cross-plane thermal conductivity of the battery is independent of temperature.•Increasing SOC decreases the cross-plane thermal conductivity of the LFP battery.•The LFP battery has nearly twice the thermal conductivity of the dry cell.
The aim of this study is to evaluate the effect of recycled concrete powder (RCP) and metakaolin (MK) on the microstructure, hydration, and compressive strength of ternary mixtures containing ...Portland. The methodology involved producing cementitious pastes with different combinations of RCP + MK, where Portland cement was substituted by 30 %, and three sources of RCP were considered: construction, demolition, and laboratory. The materials were characterized physically, chemically, and mineralogically. The characterization of the fresh state properties was done using a rotational viscometer. The hydration of the pastes was evaluated by isothermal calorimetry, X-ray diffraction, and thermogravimetry. The compressive strength and elastic modulus were determined for 1, 7, 28, and 120 days. Finally, an analysis of the microstructure of the prepared pastes was conducted by scanning electron microscopy. The results show that RCP and MK have negative influence on the fresh state properties, increasing both the yield stress and plastic viscosity. The additions also promote early hydration of Portland cement (first hours), which decreases due to the dilution effect. The quantity of hydrated products tends to be comparable to the reference, except for calcium hydroxide, which is reduced due to the pozzolanic activity of MK. The compressive strength and elastic modulus of the RCP + MK mixtures can be equal and/or superior the reference, demonstrating a synergistic effect between both materials. The use of RCP + MK mixtures is presented as a technically viable alternative to replace Portland cement without compromising performance.
•Three different sources of RCP were compared.•The use of RCP and MK increases both yield stress and plastic viscosity.•The hydration of the pastes was studied using isothermal calorimetry, XRD, and TG.•The mechanical performance of RCP + MK pastes is equal or superior to the reference.
End-of-life tire (ELT) rubber has been widely researched to replace fine or coarse aggregates in cementitious composites. While most studies paid attention to its effect on the engineering ...properties, very few considered chemical reactions with pore solution and the potential for environmental leachate. Recently the authors developed a methodology to remove zinc from the ELT rubber, since zinc can be toxic if it is leached into the environment. In this study, the authors utilized ELT rubber before and after the zinc extraction process to partially replace fine aggregate in a mortar. Flowability, compressive strength, flexural strength, and ultrasonic pulse velocity were measured for the engineering properties of rubberized mortars. Simultaneously, isothermal calorimetry was also employed to investigate the effects of ELT rubber on the hydration process of the rubberized mortars. In addition, the pore solution and leaching solutions were taken at different curing ages and then analyzed for elemental and total organic carbon (TOC) contents. The results showed a remarkable loss in engineering properties of rubberized mortar when ELT rubber was utilized, and the decrease in performance was more pronounced in the samples with zinc-extracted ELT rubber. The pore solution was found to contain significant quantities of zinc and TOC. However, the authors also found that using silica fume to partially replace cement could effectively recover the loss in strength and could reduce the leachability of zinc and TOC.
•A metallurgical processing technique is implemented to leach zinc from end-of-life tire rubber.•The fate of zinc and organic carbon leached from end-of-life tire rubber is studied.•Cement-based materials are proven effective to immobilize zinc and organic carbon leached from tire rubber.
In the quest for environmentally sustainable binders within the construction industry, metakaolin (MK) has emerged as a highly promising material. Its reactivity and hardening performance encompass a ...wide range of applications, spanning from lime to cement-based materials. This performance is primarily underpinned by the pozzolanic reaction with calcium hydroxide (CH), leading to the formation of various calcium aluminate silicate hydrates. The intricacies of the hydration kinetics and resultant reaction products hinge on several factors woven into the specifics of the binder type. This study investigates the influence of CH availability, explored through initially mixed MK/CH weight ratios of 0.33 and 1.0. Furthermore, the study examines the impact of introducing alkali hydroxides (KOH and NaOH) and/or sulfates (K2SO4 and Na2SO4) on the pozzolanic reactions. Short-term analysis employed inductively coupled plasma optical emission spectrometry (ICP-OES), and pH measurements for pore solution as well as isothermal calorimetry, and in-situ X-ray diffraction (XRD) on paste samples. Long-term investigations extended to 245 days at 40 °C, incorporating XRD, thermogravimetric (TGA) and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM/EDX). Results provide insights into the kinetics of phase assemblage and compositions of C-A-S-H gels, highlighting the transformation of metastable C2ASH8 and C4AH13 to stable Si-rich hydrogarnet phases, incorporating sulfate, under excess CH conditions. Higher MK/CH enriches Si/Ca, Al/Ca, enhancing C-A-S-H gels, while KOH addition further boosts Al/Ca ratios.
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•High OH-/CH weight ratio (0.0307) promotes formation of alkaline aluminosilicates.•For higher MK/CH (1.0), sulfate addition slows pozzolanic reactions.•Excess CH transforms C4AH13 and C2ASH8 into hydrogarnet phases.•Sulfate localizes in aluminum-rich phases: AFt, AFm and hydrogarnet.•Higher MK/CH boosts Si/Ca, Al/Ca, enhancing CASH phases, while KOH increases Al/Ca.
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