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In this paper, the ²⁹Si and ²⁷Al MAS NMR techniques were utilized to investigate the structure of C-S-H gels of slag cement-hardened paste. The results show that in the hardened paste of Portland cement, the silicate tetrahedron [SiO4]⁴⁻ exists in the Q⁰, Q¹ and Q² states, and the C-S-H gel mainly exists as the dimer (Q¹). After hydration for 3 day...
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![Figure 2.2: Pore size distribution in hydrated cement paste [8].](profile/Emanuele-Rossi/publication/366192258/figure/fig2/AS:11431281106732544@1670840074600/Pore-size-distribution-in-hydrated-cement-paste-8_Q320.jpg)
Self-healing concrete has attracted increasing attention of researchers and industry over the last decades. Given the brittle nature and the relatively low tensile strength of concrete, the occurrence of cracks is an almost unavoidable phenomenon affecting (reinforced) concrete structures. Cracks allow harmful agents present in the environment to p...
The utilization of slag as cement replacement has been widely developed for the concrete mixture. It is shown by the increment of the concrete performance even though unique characteristics during the cement-slag reaction were present. Slag is the waste of the steel industry which has various qualities. Unfortunately, this type of waste is not well...
The main objective of this research was to study the effect of activators and cure temperature on the chemical composition of pore water of blastfurnace slag cement paste. The activators studied were sodium silicate, hydrated lime plus dehydrated calcium sulphate and Brazilian class V Portland cement. The curing was carried out in natural (ambient...
In this study, the micromechanical response of two cementitious composites was characterized by nanoindentation. Pure Portland cement paste and Portland cement with 50 vol. % replaced with granulated blast furnace slag (GBFS) paste were investigated at the age of 28 days. Grid nanoindentation, statistical deconvolution and scanning electron microsc...
1. ABSTRACT Four concrete mixtures with water/cement ratios 0.5 and 0.6 have been investigated. The permeability of chloride ions was measured using the potentiometric titration. Total and soluble chloride ions contents and diffusion coefficient were measured through the concrete samples. It is concluded that the use of blast-furnace slag cement re...
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... Deconvolution of the 29 Si NMR spectra quantifies the proportions of the silicate species Q 0 , Q 1 , Q 2 , and Q 2 (1Al) in various 28-day cement mixes, as presented in Table 4. Table 4 also presents the degree of hydration (α), mean silicate chain length (Ψ), and Al/Si substitution ratio calculated using Equations (1), (2), and (3), respectively, as fundamental parameters for comprehensively elucidating the hydration mechanism and C-A-S-H microstructural evolution [50]. N0 (cement specimen with unmilled calcined soil) showed decreased Q 0 resonance and dramatically augmented Q 2 (1Al) resonance compared to the Control specimen (Table 4). ...
Rapid urbanization in many cities has produced massive amounts of problematic excavation soil. The direct disposal of untreated excavation soil often leads to significant land use and severe environmental concerns. A sustainable solution is to transform the soil waste into high-quality nano-calcined excavation soil (NCES) for application as a substitute for cement in construction. However, research in this area is very limited. This study presents a systematic investigation of the nano-sized calcined soil materials from preparation to application in cementitious material. The influence of milling parameters, including the rotational speed, milling duration, ball diameter, and milling strategy, was investigated to produce NCES with various specific surface areas. The effect of NCES substitution (15 wt% of Portland cement) in cementitious materials was then examined for mechanical performance, hydration dynamics, hydration products, and microstructure. A cement mix with very fine NCES (specific surface area of 108.76 m²/g) showed a 29.7% enhancement in mechanical strength and refined pore structure while a cement mix with un-grounded calcined soil showed a mechanical loss in comparison to the Control specimen. Delayed and reduced heat release at an early age was observed in a cement paste mixed with NCES. The underlying mechanism was investigated. The results of this work will contribute to the high-quality application of excavation soil waste.
... Deconvolution of the NMR spectra quantified the proportions of Q 0 , Q 1 , Q 2 , and Q 2 (1Al), as detailed in Table 4. Table 4 also presents the analytical results of 29 Si NMR, highlighting the significance of the variables Ψ (mean chain length of the C-A-S-H gel, Formula (1)), Al/Si (aluminum-to-silicon ratio in the C-A-S-H gel where Al 3+ replaces Si 4+ , Formula (2)), and α (extent of reaction of C 3 S and C 2 S in the cement paste, Formula (3)) in characterizing the hydration process [77]. After 3-day hydration, the concentration of Q 0 species in the control cement paste remained high, comprising 47.85% of the composition. ...
In response to the environmental implications of the massive quantities of excavation soil generated by global urbanization and infrastructure development, recent research efforts have explored the repurposing of calcined excavation soils as sustainable supplementary cementitious materials (SCMs). As it is still at an early stage, current research lacks systematic analysis across diverse soil deposits regarding their reactivity and mechanical properties within cementitious binders, despite recognized geographical variability in kaolinite content. Through comprehensive experimentation with soils sourced from four major southern Chinese cities, this study presents a pioneering assessment of the compressive strength, pozzolanic reactivity (X-ray diffraction, Fourier-transform infrared spectroscopy, solid-state nuclear magnetic resonance), and microstructural development (mercury intrusion porosimetry, scanning electron microscopy) of mortars modified by various calcined excavation soils (up to 28 days curing). The experimental data suggest that soils with a kaolinite content above 53.39% produce mortars of equal or superior quality to plain cement mixes, primarily due to their refined pore structures, microstructural densification, and enhanced hydration reactions. The findings highlight kaolinite—specifically, aluminum content—as the principal indicator of excavation soil viability for SCM application, suggesting a promising avenue for sustainable construction practices.
... This causes the silica tetrahedron and the more active aluminum tetrahedron in the TRS to undergo depolymerization reaction and fracture [30]. Under the alkaline solution environment, the depolymerized tetrahedra rebond with Ca 2+ , Si 2+ , and Al 3+ in the solution to produce C-S-H gels and a small amount of C-A-H gels [31], which enhances the gelling properties. At the same time, the Al 3+ released by depolymerization gradually increases the concentration of [AlO] 2− in the solution and reacts with Ca 2+ and SO 4 2− to form ettringite nuclei. ...
Using metallurgical solid waste Titanium-extracted Residual Slag (TRS) as mine-filling cementitious material is crucial to reduce the filling cost and promote the utilization of solid waste resources. In this paper, taking the strength of the backfill at different curing ages as the response target, the Design-expert mixing design was used to optimize the proportioning experiment of titanium-extracted residual slag, titanium gypsum, silicate cement, and total tailings, to analyze the interactions and influences of the materials on the strength of the backfill, and to analyze the hydration mechanism of the titanium-extracted residual slag-based filling cementitious materials under the optimal proportioning. The results show that: (1) the order of the sensitivity of each component to the strength of backfill is: composite activator > cement > titanium gypsum > titanium-extracted residual slag, and there are different degrees of interaction between them; (2) the optimal ratio of titanium-extracted residual slag-based filling cementitious materials is TRS:titanium gypsum:cement:composite activator = 55:25:17:3; (3) early strength formation of backfill is mainly related to its hydration products ettringite and C-S-H, the rapid nucleation and cross-growth of ettringite in the early stage forms an effective physical filling effect, which is the main reason for the formation of high early strength, and the later strength of backfill benefited from the continuous accumulation of C-S-H encapsulation and bonding, which further densified its internal structure; (4) the use of titanium-extracted residual slag-based filling cementitious materials contributes to safe, green, and economic mining.
... In this paper, we report about some 29 Si and 27 Al magic angle spinning nuclear magnetic resonance ( 29 Si and 27 Al MAS NMR) investigations (quantifications) of the C-(A-)S-H (C-S-H containing Al) nanomolecular structure of the Pox-containing Ultra-High-Performance Concrete (UHPC). ...
... In this paper, we report about some 29 Si and 27 Al magic angle spinning nuclear magnetic resonance ( 29 Si and 27 Al MAS NMR) investigations (quantifications) of the C-(A-)S-H (C-S-H containing Al) nanomolecular structure of the Pox-containing Ultra-High-Performance Concrete (UHPC). ...
... While there is a good number of papers about the NMR investigations of cement (Portland and other types), its constituent phases, and hydration products with and without additives and additions at normal or elevated curing conditions, only a few are dealing with the Normal Concrete and Ultra-High-Performance Concrete that contain microscale pozzolans (Reactive Powder Concrete "RPC" and other types) [10][11][12][13][14][15][16][17][18][19][20][23][24][25][26][27][28][29]. ...
Ultra-High Performance Concrete (UHPC) that contains pyrogenic oxides (Pox) and has been heat-cured with microwave energy reaches as high as 420 MPa after 1 day. The influence of microwave curing on the strength gain is much more pronounced in UHPC than in normal concrete. ²⁹Si and ²⁷Al MAS NMR nanomolecular structure investigation of Ultra-High-Performance Concrete (UHPC) modified with nanoscale pozzolans (pyrogenic oxides) reveals significant differences from other concrete types that may explain such high early strength. There is an increase in polymerization degree of C-(A) S–H (C–S–H containing Al) phase of the UHPC modified with pyrogenic oxides, followed by a trend of substitution of silicon atoms on the Q₃ sites of C–S–H (calcium-silicate-hydrates) through aluminum atoms. The mean chain length (MCL) and degree of connectivity (Dc) are the highest for pyrogenic oxides containing UHPC that have been cured with microwave energy. The increase of polymerization degree is more pronounced for alumina-based pyrogenic oxide containing UHPC.
... It is important to understand the mechanisms of the interaction of humic acids with ions from the dissolution of binders. (Zhao et al., 2019) in his study of the fouling behavior of humic acids investigates the interaction of calcium ions and HA. Figure III.49 summarizes mechanisms discussed in this paper: when calcium ions interact with humic acid molecules, there is an aggregation that can be produced due to charge neutralization. ...
... The major phase in the case of the GGBS-based binder is C-A-S-H, which is the calcium silicate hydrate (C-S-H) gel phase containing aluminum. (Dong et al., 2019) in his study of the gel structure of C-S-H in a pure Portland cement system and a GGBS-OPC system observed an increase in C-A-S-H gel with an increase of the hydration rate. The substitution of Al for Si in tetrahedral sites occurs often with increasing GGBS content (Richardson & Groves, 1997). ...
The accumulation of sediment particles in coastal areas arises from physical, chemical, and biological processes. Anthropogenic activities dramatically increase the sedimentation rate. Sediments may contain chemical contaminants including heavy metals (HM) and are consequently a risk to the aquatic environment and human health. Regular dredging of important shipping lanes in large industrial ports is required and this produces around 100-200 million m3 of contaminated dredged material per year. Therefore, proper treatment of the contaminated sediments is necessary, with Solidification/Stabilization (S/S) remediation technology at the forefront.The current study is specifically interested in the treatment of sediment originating in the Dublin Port for its potential reuse as a fill material for the Alexandra Basin Redevelopment Project. The sediment is contaminated with heavy metals and must be stabilized by S/S technology using a hydraulic binder. This research proposes the use of ground granulated blast furnace slag (GGBS) as an alternative binding agent to the widely used Portland cement. The objective of this study is therefore to develop an appropriate GGBS-based binder to provide the required engineering properties for further reuse of the newly formed solidified material by focusing on understanding the mechanisms having a role in the solidification of the treated sediment, but also in the stabilization of heavy metals.The compressive strength of the range of GGBS-based formulations was assessed with the UCS test and compared to the OPC-based treatment. GGBS activated by a small amount of Portland cement demonstrated a considerable increase in strength over time while that of only OPC showed a degradation of mechanical properties. To explain the obtained results, XRD, shrinkage, and microstructure investigations were conducted. In addition, the interaction of the binders with the clay fraction, organic matter, and trace metals, which were found in the studied Dublin sediments, was assessed separately through simplified models. The study of the clay fraction highlights that the phenomenon of dispersion/flocculation is one of the main mechanisms responsible for the evolution of the mechanical properties of the treated sediment. The findings from the organic matter study show a decrease of the content of some organic compounds over time, with the greatest impact observed via treatment with Portland cement. Moreover, certain heavy metals have an impact by delaying or significantly accelerating the hydration of the considered binders.The mobility of heavy metals in the treated Dublin sediment was examined using a standard leaching test. It was found that with an increase in the proportion of GGBS, the amount of leached HM decreased. Moreover, sequential extraction analysis was shown to be effective in studying the distribution of trace metals among the main sediment fractions before and after treatment. The use of GGBS as a stabilizing agent allows a decrease of the migration of heavy metals into the less stable fraction after S/S treatment. X-ray Adsorption Spectroscopy (XAS) was demonstrated to be a useful technique to explore the stabilization mechanisms, in particular changes in the chemical environment of HM (oxidation state, coordination number, etc.). It was observed that the chemical environment of Cu and Zn was not modified in the case of binders with high GGBS content.
... Sensitive and quantitative detection of residual graphitic domains in fluorinated carbon by NMR is not currently feasible without CPMG. The improvement in contrast provided by CPMG enhancement of uncoupled spins should also benefit, for example, 29 Si NMR investigations into the hydration of cement containing disordered slags [42] and tracking the quantity of carbon fiber produced from the pyrolysis of biopolymers such as lignin by 13 C NMR [43]. ...
Materials often contain minor heterogeneous phases that are difficult to characterize yet nonetheless significantly influence important properties. Here we describe a solid-state NMR strategy for quantifying minor heterogenous sample regions containing dilute, essentially uncoupled nuclei in materials where the remaining nuclei experience heteronuclear dipolar couplings. NMR signals from the coupled nuclei are dephased while NMR signals from the uncoupled nuclei can be amplified by one or two orders of magnitude using Carr-Meiboom-Purcell-Gill (CPMG) acquisition. The signal amplification by CPMG can be estimated allowing the concentration of the uncoupled spin regions to be determined even when direct observation of the uncoupled spin NMR signal in a single pulse experiment would require an impractically long duration of signal averaging. We use this method to quantify residual graphitic carbon using 13C CPMG NMR in poly(carbon monofluoride) samples synthesized by direct fluorination of carbon from various sources. Our detection limit for graphitic carbon in these materials is better than 0.05 mol%. The accuracy of the method is discussed and comparisons to other methods are drawn.
This study presents that ultra-high-performance fiber-reinforced composite can be manufactured based on alternative hydrations of slag hydration and pozzolanic reaction. Without portland cement, combinations of hydrated lime, silica fume, and ground granulated blast furnace slag or quartz powder were shown to be effective in exhibiting superior workability as well as strength. The slag hydration and the pozzolanic reaction contributed significantly to strength development, especially at the early (<7 days) and long-term ages (>28 days), respectively. When favorable conditions for the pozzolanic reaction were provided (elevated temeprature curing or the absence of hydraulic materials which perferentially consume water), the chemical reaction from the hydrated lime and silica fume, and resulting strength evolution were experimentally verified. Along with the efficiency of the pozzolanic reaction, it was found that the quartz powder acted as a supplementary silica source at 60 °C when the primary source of silica fume was depleted.
This solid-state NMR report summarises the subject and results of 247 articles and original papers published in 2019. In addition to the published reviews, the two major sections in this report consider various methodological developments and a broad range of applications. The presented classification of papers into different sections and subsections is intended to ease the overview of the results obtained in 2019, as well as to evaluate the directions in which solid-state NMR is likely to develop in the near future.
In this work, CdAl mixed metal oxides (CdAl-MMOs), CdO/CdAl2O4 composites, were prepared by calcination of sodium dodecyl sulfonate (SDS) intercalated CdAl layered double hydroxide (CdAl-LDH) at different temperature, which was synthesized by traditional hydrothermal synthesis. The CdAl-MMOs were investigated at room temperature, which shows good humidity-sensing performance. Especially, the one calcined at 500oC (CdAl-MMO-500) shows good linearity, small hysteresis, high humidity sensitivity as well as satisfactory response and recovery time. In addition, the composites CdO/CdAl2O4 have improved the humidity-sensing performances as compared to the one obtained by calcination of the blending inorganic salts. The experimental results further demonstrate that the approach of calcination LDH precursor can be generalized as an effective way of making mixed metal oxides (MMOs) with homogeneous dispersion between metal elements and thus specific properties.
