Progress Of Hydration Research Articles

Study on the Pore Structure Characteristics of Ferronickel-Slag-Mixed Ternary-Blended Cement.

Pore structure development in Portland cement, fly ash, or/and ferronickel slag (FNS) was investigated using mercury intrusion porosimetry and X-ray CT tomography. The progress of hydration was observed using X-ray diffraction (XRD) analysis and compressive strength while durability of concrete was monitored by chloride penetration resistance and chloride profiles. Mercury intrusion porosimetry (MIP) results suggested that the blended cement had a higher porosity while lower critical pore size. The major reason to this increased porosity was the formation of meso and micro pores compared to ordinary Portland cement (OPC). In terms of chloride transport, replaced cement, especially ternary-blended cement had higher resistance to chloride transport and exhibited slightly lower development of compressive strength. X-ray CT tomography shows that the influence of pore structure of ternary-blended cement on the ionic transport was strongly related to the pore connectivity of cement matrix.

Study on the fatigue properties of bitumen emulsion-cement mastics using frequency sweep and linear amplitude sweep tests

ABSTRACT Cold recycled mixtures with bitumen emulsion have an initial resistance problem. To reduce the rutting potential, cement is usually added which prompts significant changes in material properties. This study investigates the rheological properties of emulsion-cement mastics under short and long-term curing with emphasis on fatigue performance. The interaction of cationic and anionic bitumen emulsions with cement was separately investigated. Different ratios of cement to residual bitumen (c/b) between 0 and 0.7 were considered. In short-term curing, specimens were stored at 20°C for 3 days and in long-term curing, specimens were stored at 50°C for 7 days. Frequency sweep and linear amplitude sweep DSR tests were performed at two temperatures and the results were analyzed using the viscoelastic continuum damage theory. Also, frequency sweep test was performed at two high performance temperatures to evaluate the rutting potential of mastics. Furthermore, isothermal calorimetry test was accomplished to investigate the effect of emulsion-cement interaction on hydration progression. Based on the results anionic mastics had better fatigue performance than cationic ones. In contrast, cationic mastics showed a better rutting resistance. The fatigue life decreased at higher strains than 1% with increasing the c/b ratio, while at strains less than 1% the reverse was true.

Hydration and Microstructure of Steel Slag as Cementitious Material and Fine Aggregate in Mortar.

Due to the low hydration activity and poor volume stability, extensive steel slag utilization is restricted. In this paper, the hydration process and microstructure of alkali-activated materials with steel slag as a cementitious material and fine aggregate were studied. The phase composition and micro-morphology of hydration products were measured using XRD, NMR and SEM. The response relationship between microstructure and mechanical properties during hydration was revealed. The results show that the main hydration products of the alkali-activated steel slag powder-granulated blast furnace slag powder cementitious system are Ca(OH)2 and calcium aluminosilicate hydrate (C-A-S-H) gel. With the progress of hydration, the amount of calcium silicate hydrate (C-S-H) gel and the average molecular chain length increase, Al[4]/Si decreases, while C/S increases first and then decreases, and the structure of cement paste becomes much more compact. The interface between steel slag sand and cement paste is denser than that of river sand, since the hydration occurs on the surface of steel slag sand, which leads to the formation of C-A-S-H gel and Ca(OH)2. As a result, the compressive strength of concrete prepared by steel slag sand is higher than that of river sand with the same mix proportion.

Electromagnetic wave absorption performance of magnesium phosphate cement functionalized by nano-Fe3O4 magnetic fluid and hollow glass microspheres

In light of high bonding and early strengths, magnesium phosphate cement (MPC) functionalized with nano-Fe3O4 magnetic fluid and hollow glass microspheres (HGM) that exhibited excellent electromagnetic wave absorption performance (EWAP) was fabricated in this study. Coating a construction surface with multifunctional MPC could effectively withstand electromagnetic radiation hazards. Effects of the Fe3O4-like ferrite content and type (i.e., nano-Fe3O4 magnetic fluid, nano-Fe3O4 particles and magnetite), and the surface roughness of specimens on the EWAP of the MPC were investigated by lab tests. Test results showed that the Fe3O4-like ferrite greatly improved the EWAP of the MPC and the enhancement effectiveness was in descending order of nano-Fe3O4 magnetic fluid > nano-Fe3O4 particles > magnetite. Among the samples tested in this study, MPC blended with 5 wt% nano-Fe3O4 magnetic fluid showed an optimal EWAP as indicated by a peak reflection loss of −11.2 dB and bandwidth of 9.67 GHz below −10 dB. Additionally, the reflection loss of the MPC in the high frequency range could be further improved by carving notches on the surface to increase the number of microwave reflections. The electromagnetic energy absorbing mechanism and the hydration progress of the MPC were further analyzed with SEM/EDS and XRD results. The hydration degree of the MPC got improved due to the lubricating effect of HGM and filling effect of nano-Fe3O4 magnetic fluid, which also optimized its micro structure and compressive and flexural strengths. From this study, the nano-Fe3O4 magnetic fluid and HGM modified MPC had potential application in the construction of buildings for enhanced resistance to electromagnetic radiation.

Pore and phase identification through nanoindentation mapping and micro-computed tomography in nanoenhanced cement

In this work, a methodology is presented in order to assess the microstructure of Portland Cement through advanced characterisation. Nanoindentation is used to determine reduced elastic modulus and hardness, which are involved in the design of construction materials. Elemental mapping and X-ray scanning microtomography were also used to establish structure-property relations through porosity distribution and morphology as well as phase identification by nanoindentation and image analysis. The variation of carbon nanotubes (CNTs) concentration between 0.02 and 1.0 wt% demonstrated alterations in phase composition, and thus the effect of CNTs reinforcement in hydration progress was clarified. Characterisation by all techniques identified 0.5 wt% concentration as promising due to the formation of higher density hydrated phases, even though total porosity was not minimized. This fact was explained by nanoindentation as enhanced Calcium-Silicate-Hydrates connectivity in the porous network was detected. The voids of cement were filled with low stiffness hydrated gel phases as a result of enhanced hydration in the presence of CNTs.

Influence of ZnO nanoparticle ratio and size on mechanical properties and whiteness of White Portland Cement

The impact of nanotechnology on the cement industry has been extensively studied. Much work remains needed to improve product quality, decrease cost, and minimize the negative environmental impact. The present study explores the influence of ZnO nanoparticles on physical, chemical, and mechanical properties of White Portland Cement (WPC). Zinc oxide nanoparticles were prepared by simple ball-milling to reach average particle sizes of 70, 37, 27, and 24 nm. For each of the four size groups, ZnO nanoparticles were added to WPC at each of four concentrations (0.1, 0.4, 0.7, and 1.0 wt%). Whiteness, setting time, expansion, and compressive strength of resulting mortars were investigated. The crystal structure and morphology of mortars were respectively characterized using X-ray diffraction and scanning electron microscopy. Hydration progress was inspected using Fourier-transform infrared spectrometry. The results show that addition of ZnO to WPC pastes increases the amount of water required for normal consistency and setting time. The addition of 37 nm ZnO nanoparticles to WPC mortars at a specific weight percentage of 0.4% ZnO enhanced compressive strength at 28 days by up to 28% via filler effects. The characterizations and physicomechanical parameters for high-ZnO (1.0 wt%) mortar indicate less hydration products before 28 days but improved at 28 days.

Role of shear stress at rest on the viscoelastic response of fresh cement pastes

Fresh concrete is composed of aggregates and cement paste, which itself is a dense suspension that exhibits a yield stress and serves as a binder that solidifies through cement hydration. Although there is relatively little reaction during the fresh state (i.e., before setting), there is still the formation of early hydration products that will influence the paste rheology. Nonzero stress at rest widely exists in concrete practice, e.g., interruption during pumping, static formwork casting, and 3D concrete printing, but its impact on eventual viscoelastic properties is not well understood. In this study, we investigated the influence of different levels of applied shear stress at rest on fresh cement pastes and show that it dramatically alters the eventual solid performance (i.e., static yield stress and stiffness). With increasing applied shear stress at rest, the cement paste exhibited increasing static yield stress and increasingly elastic behavior, where the origin was tied to the progression of hydration. Cement pastes were compared against magnesium oxide suspensions, which served as an inert model system, and an accelerated rate of static yield stress increase over time was observed in the former but not in the latter. This highlights the role of early cement hydration on the solidification behavior of fresh cement pastes in the presence of nonzero shear stress at rest. We further support this by showing that the structural evolution of cement paste under applied stress can primarily be attributed to an enhanced elastic limit, which is associated with early hydration. The influence of two common viscosity modifying admixtures, nanoclay and diutan gum, on these properties was also examined. This work demonstrates the importance of taking the shear stress at rest into consideration for laboratory rheological experiments and industrial concrete applications, as it can substantially impact the eventual solidification behavior.

Exploring the curing condition and age effect on thermal conductivity of concrete

Energy piles are used around the world to partially heat/cool buildings or de-ice pavements. Thermal conductivity of concrete is one of the key parameters which highly affects the thermal performance of energy geostructures. Application of higher thermally conductive concrete in energy piles helps to harvest more shallow geothermal energy. Besides, higher thermally conductive concrete results in more uniform temperature distribution and will significantly increase the efficiency of the geothermal bridge deck de-icing. It is expected that the thermal conductivity of the concrete depends on its age and the applied curing conditions. The thermal conductivity of concrete can progress with the progression of hydration. While the hydration process is highly dependent on the curing condition that is applied. In this study, several concrete samples are prepared and cured under different conditions (inside the humidity room, indoor, and outdoor). Then the thermal conductivity of concrete samples at different ages are measured according to ASTM D5470-17. Results show an increase in thermal conductivity of concrete cured in humidity room for the first 30 to 40 days that thermal conductivity were measured In addition comparison of thermal conductivity of the outdoor and indoor samples show the importance of the ambient temperature and relative humidity on the thermal conductivity value.

Early hydration of tricalcium silicate with potassium hydroxide and sulfate from pore solution and solid view

This work aims to clarify the influence of potassium hydroxide and sulfate on the hydration progress of tricalcium silicate (C3S) from pore solution and solid phase aspect. The early hydration of plain system and C3S with alkalis was tested by several prevalent techniques. Results show that KOH renders the absence of induction period and enhances hydration at acceleration period. K2SO4 has higher enhancement of hydration at acceleration period. KOH could increase the supersaturation of portlandite in pore solution expediting the nucleation and growth of portlandite but SO42− in solution hampers the nucleates of portlandite. Portlandite rarely precipitates at induction period. Instead a few C–S–H precipitates at the induction period. Potassium hydroxide and sulfate decrease the critical supersaturation needing for nucleation of C–S–H. In addition, alkalis make impact on the morphology of hydration products which will influence its precipitation and growth.

Development and evaluation of an external reusable piezo-based concrete hydration-monitoring sensor

Hydration of concrete is a very complicated and multiphase process, where the cement gel transforms into a hardened state from plastic/semiplastic phase. Proper progression of the hydration process ensures the development of targeted mechanical properties such as the elastic modulus, the coefficient of thermal expansion, the Poisson’s ratio, and finally, the characteristic strength of concrete. Concrete experiences large thermal variations during the early phase of hydration due to the heat generated during the formation of cement hydration compounds, which contributes to shrinkage and cracking, somewhat making ground for the ultimate failure in the long run. Therefore, it is utmost important to monitor the progression of hydration for enhancing performance during the curing and the early service life. This article presents a new reusable external configuration of piezo-impedance transducers to monitor the hydration process in concrete structures using the electro-mechanical impedance technique. The proposed configuration consists of a thin metal foil instrumented with piezoelectric ceramic patch at the free end with the other end of the foil embedded inside the concrete. This configuration is compared against a piezoelectric ceramic patch directly bonded on the rebar used for reinforcement and another one embedded in the concrete surrounding the rebar. The sensing capability of the proposed metal foil configuration is clearly evident from the coupled admittance signature quantitatively vis-à-vis the other configurations. As a preliminary analysis, root mean square deviation values are employed to monitor the hydration process quantitatively. A piezo-equivalent mechanical model is also developed wherein the piezo-identified mass, stiffness and damping parameters are investigated for the cement hydration process so as to chalk out rigorous quantifiers of hydration progression. The employability of the proposed configuration is further proven by explanation of the physio-chemical products developed during various stage of hydration with step-by-step explanation along with corelation of the piezo-identified mass, stiffness and damping parameters. Overall, the proposed reusable configuration carries a high potential for field deployment in concrete industry for early detection of physio-chemical changes.

Recycling hazardous textile effluent sludge in cement-based construction materials: Physicochemical interactions between sludge and cement

The textile industry produces a large amount of textile effluent sludge (TES). Many studies have explored the potential use of TES in cement-based materials. However, the physicochemical interactions between the TES and ordinary Portland cement (OPC) have rarely been studied. In this study, the effects of increasing dosage (0–20% by OPC) of TES on the performance of OPC-TES blends were investigated in terms of hydration progress, mechanical strength, microstructure evolution and metal leachability. The results showed that TES markedly delayed the OPC hydration at the early age, and increasing dosages of TES decreased the portlandite content at 7 and 28 days’ age. Compared to the reference, the OPC-TES mortar exhibited seriously degraded mechanical strength; when using 20% TES, the decrease in compressive and flexural strength reached up to 71% and 42% respectively at the age of 28 days. Scanning electron microcopy and mercury intrusion porosimetry found the inclusion of TES introduced more weak interfaces in the cement mortar, thus increased the total porosity especially the macropores. But leachability tests revealed all the toxic metals in the TES were stabilized after the incorporation of OPC and exhibited very low metal mobility in the OPC-TES mortar, which posed no environmental risk.

Investigating the early-age diffusion of chloride ions in hardening slag-blended mortars on the light of their hydration progress

The present work seeks to investigate the ingress of chlorides during the hardening of slag-blended mortars that may have been exposed to chlorides since an early age. In order to correlate chloride ingress with the microstructure development, both the hydration reaction and chemical shrinkage of the investigated mixtures are monitored, and their microstructure is characterized through SEM observations. Results indicate a slow hydration reaction in the presence of slag, which decelerates the formation of hydrates and the filling of capillary pores. Despite the decrease in chemical shrinkage, chloride ingress still increases, thus amplifying the risk of corrosion in slag-blended matrices. The hydrates gradually develop within the hardening microstructure and obstruct the chloride diffusion paths, resulting in a lower chloride diffusion coefficient. The apparent chloride-diffusion coefficient measured after 28 days of exposure is 12 × 10−12 m2/s, 14.2 × 10−12 m2/s and 14 × 10−12 m2/s for hardening mortars, with respectively 0%, 30% and 60% of slag. These coefficients are respectively 2 times, 2.8 times and 4.7 times higher than those of hardened mortars.

A new implementation of electrochemical impedance spectroscopy (EIS) and other methods to monitor the progress of hydration of strontium monoaluminate (SrAl2O4) cement

Electrochemical impedance spectroscopy has been employed to monitor hydration of strontium monoaluminate (SrAl2O4) cement. Other supported techniques such as X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy with energy-dispersive X-ray spectroscopy, thermal analysis (DSC–TG–EGA) and microcalorimetry were also used. In the impedance spectrum at 102 day on a 0.5 water/cement ratio paste, a large double depressed low-frequency arc, a single depressed arc at middle-frequency region and a small part of a large depressed arc at high-frequency region were discriminated. It was due to the specific phase composition and crystal phase content in the fully hardened cement paste. Hence, the new electrochemical equivalent model R1(C1(R2W1))(C2(R3W2))(C3(R4W3))(C4(R5W4)) was implemented and fitted to the experimental results of the fully hydrated and hardened SrAH cement paste. Various hydration products including crystalline Sr3AH6, and amorphous phases SrAH7 and AH3-gel were formed at an early age of hydration. At final hydration process, the main reaction products detected are the ones most thermodynamically stable, i.e. crystalline Sr3AH6 and Al(OH)3. The heat evolution of SrAl2O4 cement under different temperatures (20 °C and 40 °C) was examined by isothermal calorimetry. The curing temperature was found to have a visible effect on cement hydration kinetics.

Design of self-desiccating binders using CSA cement: influence of the cement composition and sulfate source

Calcium sulfoaluminate (CSA) cements with high ye'elimite content are of interest for the production of self-desiccating binders. In this work, the influence of cement composition and calcium sulfate source on the content of water bound by hydration was investigated, with the future goal of designing non-expansive materials with a dry internal environment. A thermodynamic approach was used first. Ten cement compositions were prepared by blending a CSA clinker comprising 54·3% ye'elimite and 29·1% belite with anhydrite and calcium oxide, respectively, within the ranges 80–95%, 5–20% and 0–15%. Cement suspensions (water/cement ratio (w/c) = 6) were maintained under stirring at 20°C for 1 month. The cement comprising 80% clinker and 20% anhydrite led to the highest contents of ettringite and bound water, which was simulated well by thermodynamic calculations. A kinetic study was then performed on cement pastes (w/c = 0·5 or 0·6), with the cement comprising 80% clinker and 20% calcium sulfate (introduced as anhydrite or gypsum). The addition of gypsum, which dissolves faster than anhydrite, led to the rapid formation of a dense microstructure, which tended to limit the progress of hydration at later age. With anhydrite, higher hydration degrees were reached and specimens cured in a wet or dry environment exhibited smaller volume changes.

Influence of free and sorbed zinc on cement hydration

Zinc, similarly to many other metals, is known for its negative influence on the rate of hydration in cementitious systems. The present paper deals with a specific form of zinc—Zn2+ ions sorbed on a solid sorbent. The sorbent under study is a waste ceramic powder, exhibiting very good sorption capacity for (not only) zinc. Such ceramic sorbent is intended to be used for removal of Zn2+ from industrial wastewaters. The spent sorbent has to be stabilized in order to prevent leaching of Zn to the environment; the most common stabilization method is incorporation to cement matrix, where the sorbed Zn may harm the hydration course and thus retarded the setting and hardening of stabilizate. Zn is sorbed on the ceramic sorbent in form of insoluble basic zinc sulfate ZnSO4·3Zn(OH)2·4H2O. As a reference system, relatively well-described ordinary Portland cement (OPC) + ZnO (also insoluble Zn form) system was tested. The used Zn contents were 0.08, 0.16 and 0.64% by mass of OPC. Isothermal calorimetry demonstrated large delay in systems with 0.64% Zn, while 0.08% did not have any significant influence on heat evolution, regardless the Zn form. At the medium 0.16% Zn content, the sorbed Zn was less retarding than free ZnO. The influence of Zn on strength, portlandite and C–S–H formation was monitored as well in time. To conclude, the differences between ZnO and sorbed Zn were just moderate; both forms retarded the hydration progress and strength in similar way. Presence of Zn caused formation of C–S–H hydrates with higher Ca/Si ratio than it was detected in OPC control.

Development of mathematical models for predicting the compressive strength and hydration process using the EIS impedance of cementitious materials

Abstract In this study, the early-age hydration process of cement paste is characterized using the rate of change in the impedance measured by electrochemical impedance spectroscopy (EIS). To effectively describe the microstructure variation during the hydration process, specific hydration models corresponding to four related primary hydration stages with variation in the impedance are explained. An impedance evaluation function for the degree of hydration and heat evolution has been proposed and the correlation has been deduced as α t = W n t W total = Q t Q total = D ln k 1 ρ z t ln k 2 ρ total . The hydration degree and heat evolution of cementitious materials with different amounts of w/c ratio and fly-ash (FA) contents are both characterized using the rate of change in the impedance. Early-age impedance can be considered as an equivalent index for the total heat release and offers a promising method of evaluating the cement-hydration degree. Moreover, the impedance can be applied to predict the compressive strength of the FA-blended cement paste. In most cases, the hydration properties of cementitious materials are measured using damaged samples for further analysis. EIS provides additional technical foundations for theoretical and non-destructive testing to investigate the hydration progress and strength estimation, which further aids in achieving improved understanding of the change rate in the electrical impedance of cement-based materials at early ages.

Influence of gadolinium oxide and ulexite on cement hydration and technical properties of mortars for neutron radiation shielding purposes

Gadolinium oxide (Gd2O3) is a potentially effective mineral additive that improves neutron shielding properties of cement based composites. The paper presents the influence of Gd2O3 and ulexite (a boron compound) on Portland cement hydration evaluated by isothermal calorimetry measurements and strength. The progress of hydration was investigated on mortar specimens at water to cement ratio w/c = 0.5 and sand/cement ratio 0.75. The addition of Gd2O3 generates a slight retardation of cement hydration, however it accelerates aluminate activity at the same time. The hydration of cement was completely hindered for mortars containing a substantial content of ulexite. The strength test results show that addition of Gd2O3 to Portland cement mortar mix caused a decrease of early age (3 days) flexural and compressive strength. The optimum content of Gd2O3 in respect to the long term compressive strength and the hydration kinetics was 5% in relation to the mass of cement. Good long term strength was also obtained for specimens with 3% of ulexite.

Development of magnesium-silicate-hydrate (M-S-H) cement with rice husk ash

Rice husk ash (RHA) is a waste material obtained from the combustion of rice hulls. The properties of RHA, such as its crystallinity and reactivity, depend on the combustion conditions. This study investigated the use of RHA as a silica source in MgOSiO2 samples. Two different RHA sources (crystalline and amorphous) were used in comparison to microsilica (MS), which is commonly used in MgOSiO2 formulations to form magnesium silica hydrate (M-S-H). Isothermal calorimetry and pH measurements were used to analyze the progress of hydration. In addition to compressive strength measurements, microstructural analysis was performed via XRD, TG/DTG, FTIR and FESEM. Samples containing amorphous RHA as the silica source achieved the highest compressive strengths at early ages (34 MPa at 7 days), whereas those containing MS revealed the highest strengths in the long term (47 MPa at 56 days). This was in line with the faster dissolution rate of amorphous RHA in comparison to MS, as observed in pH measurements. The formation of M-S-H was clearly observed in all samples containing amorphous RHA and/or MS. The use of crystalline RHA led to low strengths, which was provided by brucite in the absence of M-S-H. Combination of amorphous RHA with MgO resulted in M-S-H formation, which was accompanied with a notable mechanical performance. Utilization of amorphous RHA in MgO systems could not only lead to strength gain, but also bring environmental and economic benefits.

Influence of different W/C on the performances and hydration progress of dual liquid high water backfilling material

Sulfoaluminate cement-based high-water materials are widely used in coal and metal mining. There are few reports on the water cement ratio (W/C) affecting the properties and progress of hydration on dual liquid cement-based materials. Here, the effects of different W/C on dual liquid cement-based material on setting time, viscosity, compressive strength, water loss rate, diffusion radius, hydration heat, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction and SEM tests were studied. The results showed that as the W/C increased, the setting time increased, and the viscosity of single slurry decreased. Furthermore, as the slurry X and Y were mixed, the viscosity had an inflection point, and the compressive strength decreased while the later strength slowly increased; the relative water loss rate within 60 min reached 2.3–2.6, and was essentially stable after 40 h when the water cement ratio increased from 5:1, 6:1, 7:1, 8:1 to 9:1. When W/C = 8:1, it can be considered a turning point; the formula of diffusion radius obtained by experiments showed that the accumulative heat release and heat flow rate obviously decreased when the W/C was greater than 8:1. Also, the analysis results of XRD and SEM indicated that ettringite was the main hydration product, and as the W/C decreased, its density and shape also changed.

A contribution to the characterization of the silicate-water interface – Part I: Implication of a new polished sample hydration technique

The analysis of the atomic composition of the interface between tricalcium silicate (C3S), the main compound of Ordinary Portland Cement, and surrounding solution is still a challenging task. At the same time, that knowledge is of profound importance for describing the basic processes during hydration. By means of Scanning Electron Microscopy (SEM) and Atom Probe Tomography (APT) we combine modern techniques in order to shed light on this topic in the present study. The results of these methods are compared with conduction calorimetry as a standard technique to study the hydration kinetics of cement. The tests were carried out on powders as well as on polished C3S samples.Results indicate that the progress of hydration is strongly increased when the C3S is used in the form of polished specimen. First C-S-H phases are detected in the powder 2.2 h after contact with water, on the polished section after 5 min. Besides SEM, the formation of C-S-H phases can be detected by APT, leading to an advantageous atomic resolution compared to EDX analysis. We propose that the use of APT will lead to deeper insights on the hydration progress and on the composition of the sensitive C-S-H phases based on these first results.