Proton Spin–Spin Relaxation Study of the Effect of Temperature on White Cement Hydration

The chemical and microstructural changes within a white cement paste were characterized in situ using proton nuclear magnetic resonance spin–spin relaxation at 30 MHz, and X-ray diffraction. Paste samples with a water-to-cement ratio of 0.42 were cured at constant temperatures of 2°, 20°, 60°, and 100°C. Proton nuclear magnetic resonance spin–spin relaxation allows tracking the evolution of the mixing water into the solid fractions of calcium silicate hydrate, calcium hydroxide, and monosulfate, and the liquid phases: the calcium silicate hydrate interlayer water, gel pore water, and capillary pore water. It is shown that the hydration process is markedly accelerated with increasing hydration temperature, and that proton nuclear magnetic resonance relaxation measurements can quantitatively determine the proportions of water phases, their magnetic resonance characteristics, as well as the setting times of the cement during the hydration process.     

Nuclear magnetic relaxation dispersion investigations of water retention mechanism by cellulose ethers in mortars

We show how nuclear magnetic spin–lattice relaxation dispersion of proton-water (NMRD) can be used to elucidate the effect of cellulose ethers on water retention and hydration delay of freshly-mixed white cement pastes. NMRD is useful to determine the surface diffusion coefficient of water, the specific area and the hydration kinetics of the cement-based material. In spite of modifications of the solution's viscosity, we show that the cellulosic derivatives do not modify the surface diffusion coefficient of water. Thus, the mobility of water present inside the medium is not affected by the presence of polymer. However, these admixtures modify significantly the surface fraction of mobile water molecules transiently present at solid surfaces. This quantity measured, for the first time, for all admixed cement pastes is thus relevant to explain the water retention mechanism.     

Evaluation of Composites Miscibility by Low Field NMR

Solid state nuclear magnetic resonance (NMR) is a powerful technique to analyze polymer composites. The use of proton relaxation data to evaluate the dispersity of the dispersion phase in the composite and its homogeneity are very wide. In this work PVC/silica composites were prepared using different ratios to obtain a new material to be used in chromatograph column for separation of plant extracts. Thus, this study used proton spin–lattice and spin-spin nuclear magnetic resonance relaxation data, determined in a low field NMR spectrometer as a method to characterize those composites in relation to silica dispersion as well as PVC/silica compatibility. From the relaxation data analyses, the best ratio of PVC/silica, according to the components dispersion and consequently composite compatibility, was 80/20, according to the determined T₁ values.     

Effect of MHEC on evaporation and hydration characteristics of glue mortar

The influence of methylhydroxyethylcellulose (MHEC) on both moisture distribution and hydration characteristics of glue mortar using nuclear magnetic resonance imaging (NMR) is investigated. MHEC is added to glue mortar in order to control the drying rate by increasing the open time. Besides drying, MHEC might influence hydration characteristics of mortar. In this study, we therefore examined the effect of MHEC on the hydration characteristics of unsealed mortar. Without MHEC, the evaporation time is faster than hydration time and the water distribution is homogeneous in the mortar, resulting in poor hydration. Addition of MHEC > 1.3 wt.% exhibits an evaporation time comparable to the hydration time of mortar. However, in that case, inhomogeneous distribution of water causes differences in the degree of hydration throughout the mortar sample, i.e. the top surface shows poor hydration and the bottom surface shows good hydration, as confirmed by MIP and T₂ relaxation analysis.     

NMR studies of hydrating cement: A spin-spin relaxation study of the early hydration stage

The early stages of cement hydration were investigated by proton spin-spin relaxation time (T_c) measurements because these experiments can be performed much faster (in several seconds) than the characteristic time for a change in hydration evolution. In addition, comparing the free induction decays of nuclear magnetization and its spin echoes allows the separation of solid-like and liquid-like proton groups. The values of T₂ and the associated magnetization fractions were monitored for cement pastes with different water/cement ratios in the first 20 hours of hydration.

Results show that already at the time of the first measurement, i.e. six minutes after mixing dry white cement powder with water, a quasi steady state is reached with protons distributed in three groups: loosely bound water (in the gel coatings and interstital spaces between coated clinker grains with T₂ of several ms), tightly bound water (T₂ 100μs) and water/hydroxyl protons in crystalline structure (T₂ 10 μs). The values of T₂ and their associated magnetizations are fairly constant during the first several hours with the solid-like components only slowly growing at the expense of the liquid one. The fraction of the loosely bound water as well as the absolute value of its T₂ increases with increasing w/c ratio. These data indicate that although nothing vigorous is happening in the dormant period of cement hydration there is a continuous growth of the solid matrix.     

The Determination of Surface Development in Cement Pastes by Nuclear Magnetic Resonance

Pulsed proton NMR was used to determine the specific surface of hydrating cement pastes. The method is based on the fact that the measured proton spin-lattice relaxation rate (l/ T₁ ) of water in cement pastes is (in view of the fast exchange between water molecules in the adsorbed and bulk phase) proportional to the fraction of water molecules covering the solid surface and thus proportional to the NMR surface of the newly grown hydration products. In general, the method can be used for powders, fibrous and porous materials in contact with liquid water, or other fluids containing protons.     

Percolation Model of Nuclear Magnetic Relaxation in Porous Media: Slow Diffusion

Nuclear magnetic relaxation in a porous medium is simulated by a random walk on the open sites of a percolation lattice. This model is used to study relaxation in the case that diffusion to the pore surface is slow compared to relaxation at the surface. The computed decay curves can be fit by sums of exponentials. For slow diffusion the principal relaxation time is independent of the surface relaxation rate. It is inversely proportional to the diffusion coefficient and directly proportional to the mean square displacement of the walkers. It appears that a measurement of nuclear magnetic relaxation in the slow diffusion range will yield only an average pore size. This pore size is given by the root mean square displacement to the surface for a random walker starting with equal probability from any point in the pore space.     

Nuclear spin-lattice relaxation in nanocarbon compounds caused by adsorbed oxygen

Nuclear spin-lattice relaxation measurement is an effective tool for studying electronic structure and magnetic properties of nanosized compounds. The present work deals with the effect of oxygen molecules, adsorbed onto the surface of carbon nanoparticles - in which the number of surface atoms is comparable with that in the sample's volume - on nuclear spin-lattice relaxation rate of the carbon nuclei. We measured ¹³C spin-lattice relaxation in as-prepared (air rich) and out-gassed samples of detonation nanodiamond (DND), activated carbon fibers (ACF) and glassy carbon (GC) samples having multishell onion-like structure.Our measurements showed that the paramagnetic oxygen molecules (the only magnetic agent in ambient air), being physisorbed onto the surface and in structural voids of ACF and GC, create an additional relaxation channel and definitely affect the ¹³C spin-lattice relaxation as do the unpaired electrons of the internal dangling bonds. Air removal results in 1.5-2 times elongation in T₁. In contrast, the relaxation time is nearly the same for as-prepared and out-gassed DND samples. The reason is that in DND oxygen molecules have access only to the surface carbon nuclei whereas the rest of carbons remain unaffected by oxygen. Thus the main relaxation agents in DND particles are dangling bonds with unpaired electron spins, which mask the relaxation effect of paramagnetic oxygen. These findings are in a good agreement with our EPR data, which show that oxygen affects the inherent paramagnetic defects in the aforementioned nanocarbons.     

NMR Relaxation Study of Adsorbed Water in Cement and C3S Pastes

The deuteron and proton spin-lattice and spin-spin relaxation times T ₁ and T ₂ of adsorbed water in commercial portland cement and tricalcium silicate pastes were studied as functions of the hardening time at room temperature. The time dependence of the water self-diffusion coefficient of tricalcium silicate pastes was also followed. The proton and the deuteron T ₁ and T ₂ decrease markedly as hydration increases and the pastes harden due to the increase in the active surface and the number of adsorptive sites, thus providing convenient tools for studying the nature of the hydration process.     

1H驰豫时间谱在水泥基材料研究中的应用

水泥水化、硬化体结构的形成及演化、水泥基材料内部不同水分之间的转化、吸水、干燥、水分在水泥基材料内部的扩散过程引起水分化学状态或所处环境物理状态的变化.这种变化可用1H核磁共振驰豫时间进行表征.已有的研究表明,1H驰豫时间谱可用于水泥水化过程、硬化体结构形成、孔结构、水分在水泥基材料内的传输过程等的表征,所得结果与其它方法所得结果有较好的一致性.且磁共振成像可直接观察水分在水泥基材料中的分布及传输,这是其它现代测试方法难以达到的.     

On the use of pulse NMR techniques for the study of cement hydration

The application of pulse NMR to the study of hydration of cement and its constituents is discussed. The quantity of adsorbed water in hydrated samples can be most easily determined by measuring the proton free induction decay signal, whereas the rates of hardening and hydration can be best followed by measuring the proton spin-lattice and spin-spin relaxation times. The use of multiple pulse high resolution NMR in solids techniques is helpful in separating the H₂O and OH-group signals whereas ²⁷Al quadrupole coupling and spin-lattice relaxation may as well contribute to our understanding of the structure and hydration of cement.     

Miscibility and interactions in poly(n-propyl methacrylate)/poly(vinyl alcohol) blends

Poly(n-propyl methacrylate) (PPMA) is miscible with poly(vinyl alcohol) (PVA) over the whole composition range as shown by the existence of a single glass transition temperature in each blend. The interaction between PPMA and PVA was examined by Fourier transform infrared spectroscopy and solid-state nuclear magnetic resonance spectroscopy. The interactions mainly involve the hydroxyl groups of PVA and the carbonyl groups of PPMA. The measurements of proton spin-lattice relaxation time reveal that PPMA and PVA do not mix intimately on a scale of 1-3 nm, but are miscible on a scale of 20-30 nm. A small negative interaction parameter value has been obtained by melting point depression measurement.     

Synthesis and characterization of novel citric acid-based polyester elastomers

In this paper we report successful simple synthesis of unique elastic polyesters by carrying out catalyst-free polyesterification of multifunctional non-toxic monomers: 1,8-octanediol (OD), citric acid (CA) and sebacic acid (SA). The chemical, physical, and surface chemical properties of the resulting copolyester polyoctanediol citrate/sebacate [p(OCS)] have been investigated. This new material was characterized by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-ToF-MS), nuclear magnetic resonance spectroscopy (NMR), thermal analysis (TA), mechanical tests, photo-acoustic Fourier-transform infrared spectroscopy (PA-FTIR), X-ray photoelectron spectroscopy (XPS) and swelling experiments. We demonstrate that the chemical structure, morphology, physical integrity and surface chemistry of the synthesized co-polymer can be controlled by simply varying the initial acid concentration (CA/SA) in the pre-polymer. This novel p(OCS) polymer exhibits versatility in mechanical properties, hydration and hydrolytic degradation as determined by the chemical structure of the polyester elastomer.     

Investigation of PMMA/Polyoxide blends containing graft-copolymer compatibilizers by using NMR,SEM, and thermal analysis

The effects of blend compatibility caused by compatibilizing agents were studied by microscopy, thermal analysis, and nuclear magnetic resonance (NMR) spectroscopy (carbon-13 NMR spectra and proton spin-lattice relaxation time) of homopolymers and polymer blends. In this study the results obtained by all measurements are discussed in terms of molecular mobility and compatibility, as a consequence of changes in the microdomains. © 1996 John Wiley & Sons, Inc.     

Composition and surface energy characteristics of new petroleum resins

We investigated the composition and surface energy properties—the surface free energy, acid–base and dispersive components, acid and base parameters (according to the van Oss–Chaudhury–Good method) and acidity parameter (according to the Berger method) for several types of aromatic petroleum resins (PR). We could see that the Berger, nonlinear systems, and spatial methods provide slightly different information about the acid–base properties of PRs. For acid–base properties, relevant proton content was determined for each sample by nuclear magnetic resonance spectroscopy. Correlations between the composition and surface characteristics of the studied aromatic PR have been revealed. According to the data obtained from the acid–base approach and nuclear magnetic resonance spectroscopy, we can predict the possible combinations of PR–polymer with the best interface interaction, which can lead to high mechanical properties. POLYM. ENG. SCI., 57:1028–1032, 2017. © 2016 Society of Plastics Engineers     

Analytical13C NMR spectroscopy of fatty quaternary amines

Natural abundance¹³C nuclear magnetic resonance spectroscopy (CMR) has been used for the rapid, nondestructive analysis of fatty quaternary ammonium compounds. Quantitative analysis of mixtures of mono-, di-and tri-fatty ammonium chlorides can be accommpublished under conditions that do not involve heat or extremes of pH and that are independent of solvent present. In order to determine optimal conditions for quantitative studies, carbon spin lattice relaxation times (T₁) and nuclear Overhauser effects (NOE) were determined for each of the components. The method of internal standard addition was used to determine reproducibility and accuracy of the method for the measurement of mono-and tri-fatty quaternary components in material consisting predominantly (i.e., greater than 90%) of di-fatty-dimethyl ammonium chloride.     

Diffusion properties of lipids—Pure and in seeds

Diffusion constants of some fatty acids and triglycerides in pure form and also in seeds have been measured at different temperatures in order to elucidate the motion and organization of triglyceride molecules in oils. The size of the oil storage cavity (droplet) in seeds has been estimated to be 0.8 μ. Temperature dependences of the proton T₁ relaxation time in some samples have been measured by pulsed nuclear magnetic resonance (NMR). From these measurements it is concluded that since activation energies for the relaxation mechanism, diffusion, is the same in seeds as in pure oils, 0.22 eV, the nature of the motion is similar.     

NMR study of starch based polymer gel electrolytes: Humidity effects

In this work, nuclear magnetic resonance spectroscopy (NMR) was used to study the effect of water absorption in polymer gel electrolytes formed by amylopectin rich starch, plasticized with glycerol and containing lithium perchlorate. The position of the ⁷Li spin-lattice relaxation rate maximum is shifted progressively towards lower temperatures with increasing hydration, reflecting an increase of the lithium mobility. The mechanism responsible for the spin-lattice relaxation of the ⁷Li nuclei in the gel electrolytes are the fluctuations of the quadrupolar interaction due to the lithium motions. The ⁷Li relaxation results of the gel electrolyte hydrated with 2.2 water per complex unit suggest that the lithium ions are almost decoupled from the polymer chain and coordinate, hence preferring the water molecules.     

The compatibility study of polycarbonate-polyvinyl pyrrolidone blend using high-resolution solid-state nuclear magnetic resonance

The combining nuclear magnetic resonance techniques in the solid state permit the evaluation of the polymeric systems homogeneity. In the polycarbonate-poly(vinyl pyrrolidone) (PVP) blends, the response of proton spin-lattice relaxation time in the rotating frame was the determinant to obtain information on the transition when the quantity of PVP is close to 40% by weight and a better organization of amorphous phase was detected. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 449–453, 1998     

Rubber-filler interaction effects on the solid state dynamic mechanical properties of polyethylene/EPDM/calcium carbonate composites

Composites of polyethylene, ethylene propylene diene rubber (EPDM), and calcium carbonate are milled and analyzed by solid state dynamic mechanical spectroscopy. The torsion pendulum measurements show that the multicomponent composites exhibit complex viscoelastic behavior. In composites of polyethylene and calcium carbonate, the experimentally observed modulus enhancement is greater than that expected from the properties of the constituent materials, assuming well-dispersed inclusions. In composites of polyethylene, rubber, and calcium carbonate, interactions of the rubber with the filler surface are significant. Specifically, maleic anhydride modification of the EPDM results in rubber-filler interactions that drastically influence the properties of the composite. The maleic anhydride modification results in a morphology with more rubber around the filler particles and thus an enhanced rubber glass transition peak. The rubber-filler interaction has been attributed to salt formation at the filler surface. The interaction was also detected by solid state proton nuclear magnetic resonance (NMR) relaxation experiments. Treatment of the filler surface with gamma-aminopropyltriethoxysilane (γ-APS) or gamma-methacryloxypropyltrimethoxysilane (γ-MPS) has significant influence on the dynamic mechanical properties.