Hydration Of Pastes Research Articles

Investigating the Hydration, Mechanical Properties, and Pozzolanic Activity of Cement Paste Containing Co-Combustion Fly Ash

The heat of hydration, mechanical properties, pozzolanic activity, and microscopic characteristics of cement pastes incorporating co-combusted fly ash (CCFA) were investigated, and the disparities between the CCFA/cement system and the coal fly ash (CFA) binding system were also compared. The results indicate a decrease in the heat of hydration for both CFA and CCFA samples, with a more pronounced trend observed as the fly ash content increased from 10% to 30%. The distinction in the early hydration between CFA and CCFA samples primarily manifested in the rate of heat release, potentially correlated with variations in the active Al2O3 content in the fly ash. Neither CFA nor CCFA samples exhibited significant cementitious activity at 3 days, functioning solely as inert fillers in the cement paste. By 3 and 28 days, the mechanical properties of both CFA and CCFA samples were inferior to those of pure cement paste. However, by 180 days of hydration, the compressive strength of CCFA-blended mortar notably increased, with the highest strength observed in the 10% CCFA-blended sample. Both CFA and CCFA samples produced the secondary hydration product C-A-S-H and demonstrated comparable consumption of calcium hydroxide (CH). These findings underscore the potential of CCFA as a supplementary cementitious material (SCM) and lay a foundation for its widespread adoption.

Evaluating sugarcane bagasse fly ash as a sustainable cement replacement for enhanced performance

This study evaluated the potential of sugarcane bagasse fly ash, collected from boiler exhaust stacks via a bypass pipe, as a renewable supplementary cementitious material. The bagasse fly ash was ground into three different particle sizes (D50 of 10, 20, and 30 μm) and characterized in terms of morphology, porosity, specific surface area, and pozzolanic activity. The influence of the ashes on paste hydration was investigated using isothermal calorimetry. Mortars were then tested with 20% cement replacement by fly ash, analyzing packing density, compressive strength evolution, and durability against sulfuric acid. Results indicated the suitability of the fly ash as a supplementary cementitious material, with low contamination and greater pozzolanic activity at smaller particle sizes. This enhanced initial hydration and long-term strength, with finer ashes showing superior mechanical properties when compared to the reference mortar (an 8% increase). Mortars with fly ash exhibited higher packing density and reduced mass loss under sulfuric acid attack, but increased water absorption and capillarity, alongside decreased compressive strength compared to the reference. Briefly, the findings highlighted that the potential of bagasse fly ash as a promising low cost and eco-beneficial material for sustainable construction practices.

IMPACT OF ALUMINOSILICATE WASTES ON THE HYDRATION, PHYSICAL AND MECHANICAL PROPERTIES OF CEMENT PASTE

The impact of aluminosilicate wastes (spent fluid catalytic cracking catalyst from oil companies and metakaolin containing waste from the production of expanded glass granules) on the hydration and compressive strength of the cement paste was analysed when a proportion of cement was replaced by one waste material or two waste materials. The article presents results of X-ray diffraction and thermal analysis of hardened cement pastes. It was determined that the spent catalytic cracking catalyst accelerates cement hydration because of its high surface area and pozzolanic activity; and metakaolin containing waste has a retarding effect. X-ray diffraction and thermal analysis showed that the specimens with metakaolin containing waste had the lowest amount of portlandite, and the compressive strength of these specimens was similar to that of the control specimens when a superplasticizer was used. It was found that a mix of aluminosilicate wastes has a different effect on cement hydration and makes it possible to adjust the hydration time of the binder within a certain interval.

IMPACT OF ALUMINOSILICATE WASTES ON THE HYDRATION, PHYSICAL AND MECHANICAL PROPERTIES OF CEMENT PASTE

The impact of aluminosilicate wastes (spent fluid catalytic cracking catalyst from oil companies and metakaolin containing waste from the production of expanded glass granules) on the hydration and compressive strength of the cement paste was analysed when a proportion of cement was replaced by one waste material or two waste materials. The article presents results of X-ray diffraction and thermal analysis of hardened cement pastes. It was determined that the spent catalytic cracking catalyst accelerates cement hydration because of its high surface area and pozzolanic activity; and metakaolin containing waste has a retarding effect. X-ray diffraction and thermal analysis showed that the specimens with metakaolin containing waste had the lowest amount of portlandite, and the compressive strength of these specimens was similar to that of the control specimens when a superplasticizer was used. It was found that a mix of aluminosilicate wastes has a different effect on cement hydration and makes it possible to adjust the hydration time of the binder within a certain interval.

How Competitive Hydration between C 3 A and C 3 S in the Fast Dissolution Stage Affects the Hydration of Low-Heat Portland Cement Blended Pastes

How Competitive Hydration between C ₃ A and C ₃ S in the Fast Dissolution Stage Affects the Hydration of Low-Heat Portland Cement Blended Pastes

Fundamental effects of using power ultrasound to accelerate C3S hydration

Activation of cement hydration accelerates hardening of concrete, enables faster production rates or production at similar frequency but significantly reduced CO2 emissions. The present study sheds light at the reason for accelerated cement hydration when power ultrasound (PUS) is applied during mixing.The investigations analysed the effect of PUS on dissolution of tricalcium silicate (C3S), homogeneous precipitation of C-S-H as well its effect on C3S-hydration. A combination of analytical techniques such as electric conductivity, optical emission spectroscopy, thermogravimetry, conduction reaction calorimetry, scanning electron microscopy and specific surface analysis were applied. It was revealed that PUS has a significant effect on paste hydration, which is induced by heterogenous nucleation of C-S-H and CH immediately after sonication. These hydrates were formed and dispersed by sonication thus acting as in-situ formed crystal seeds which shorten the induction period of C3S hydration.

Influence of steam curing on hydration and microstructure of cement paste containing high-volume lithium slag

The application of supplementary cementitious materials (SCMs) of concrete reduces the carbon emissions due to the reduced cement. But the early properties of mortar or concrete with high-volume SCMs are degraded, which hinders the expanded applications of concrete. However, early properties of mortar or concrete containing high-volume SCMs concrete can be effectively improved by steam curing. The influence of different steam curing systems on the microstructure and strengths of cement paste with high-volume of lithium slag (LS) are studied. The results manifest the early-compressive strengths, the content of chemically bound water and the hydration degree of the specimens are improved due to the different curing systems. The early-compressive strengths of specimens under steam curing-II is better than that under steam curing-I, but the compressive strengths at later ages is not as good as the steam curing-I, which is because of the maximum steam curing temperature. The scanning electron microscope (SEM) images show that cement paste with LS have a denser microstructure under the action of steam curing. This is not only due to the filling effect of LS, but also because LS is further activated under high temperature conditions, which promotes generation of hydration products and fills the internal pores. The data of mercury intrusion porosimetry also proves the above phenomenon.

Quantitative determination of quaternary solid waste-based binders and its hydrates by XRD

Solid waste-based binders offer intrinsic low-carbon advantages and non-primary resource consumption, making them one of the most promising low-carbon binders. However, the compositions of multiple components and the complex nature of their raw materials—mainly industrial solid wastes—make the stability and control of their quality very difficult, thereby limiting their practical applications in industry. The core of controlling product stability lies in quantifying the blended mixes. The progress in X-ray diffraction and its analysis methods has provided an opportunity to directly and non-destructively measure the phase compositions of solid waste-based binders. Rietveld refinement has been widely used to quantify the blend of crystals. However, due to the X-ray amorphous diffraction characteristics of aluminosilicates in most solid wastes, distinguishing and quantifying them is challenging. The PONCKS method has provided a strategy for indexing the amorphous phases and facilitating the distinction of different amorphous phases in various raw materials. In this study, by combining the Rietveld and PONCKS methods, a strategy has been presented that applies the XRD method to quantify the mixing proportions and their hydration products, and its validity has been verified. Factors such as crystal preferred orientation, background selection, and the structure for establishing the CASH model have been identified as more significant for accurate analysis and the optimal fitting strategy has been suggested. Lastly, in-situ XRD measurements, a very promising technology for studying the fresh paste hydration processes, have also been conducted. The real-time continuous determination has provided a more insightful understanding of the hydration and setting behaviors of the solid waste-based binder.

Insight into the early hydration characteristics of Portland cement with hydroxyethyl methyl cellulose highlighted by 1H low-field NMR

1H low-field nuclear magnetic resonance (1H NMR) as a non-destructive test method can effectively capture the water state changes in cement pastes. The water changes can in turn reflect the early hydration characteristics of cement pastes. Hydroxyethyl methyl cellulose (HEMC) with different viscosities affects the hydration characteristics of cement by acting on the water in different states. The following experimental results are obtained by testing hydration of cement pastes with HEMC by using 1H NMR test. Incorporating 0.1–3% HEMC with different viscosities all can effectively control the bleeding water phenomenon. HEMC can absorb a part of the water in the cement pastes. Incorporating 2–3% HEMC significantly delays the enrichment of the gel pores water and interlayer water. When the content of HEMC increases from 0% to 3%, the hydration degree of cement pastes tends to decrease. Besides, HEMC with higher viscosity of 15000–40000 mPa·s obviously delays the hydration process of cement pastes compared to HEMC with lower viscosity of 400 mPa·s.

Seeding effects of submicron CaAl-NO3 LDH particles on the hydration and properties of Portland cement and sulfoaluminate cement pastes

Layered double hydroxide (LDH) is reported to improve the durability of concretes, primarily due to its ability to exchange anionic species, including chloride, which is implicated in corrosion-driven durability issues. However, there is no comprehensive study investigating the effect of LDH on the properties of different cement systems at both early and mature ages. In this study, the early age and mature age properties of Portland cement (OPC) and calcium sulfoaluminate (CSA) cement pastes seeded with submicron-sized calcium aluminum-NO3 LDH (CaAl-NO3 LDH) were investigated. The effects of the 1–5%mass dosage of LDH on the hydration of both cement systems were characterized by rheology, isothermal calorimetry, porosimetry, compressive strength tests, thermogravimetric analysis, and x-ray diffraction. Time-dependent rheology results indicate that CaAl-NO3 LDH seeding enhanced the buildability of cement pastes, as evidenced by increased plasticity loss, hardening, and yield stress. While LDH seeding accelerated hydration kinetics for both CSA and OPC pastes, interestingly, the OPC exhibited reduced heat release, suggesting potential applications of LDH as heat sink in various areas, including building in hot climates, reducing heat and crack-propensity in mass concrete placements, and 3D-printed OPC-based concretes. Although LDH slightly decreased compressive strengths at both 1d and 28d, its primary role was to expedite the hydration process without enhancing the microstructure or strength of the final product.

Gypsum slurries to apply in oil well: An insight into thickening time

Gypsum is widely used in the construction industry, especially as a hydraulic binder. Studies have indicated the use of α-HH gypsum as an alternative material to Portland Cement in oilwell cementing operations, highlighting the reduction in environmental impacts from the reduction of Portland Cement. Calcium Sulphate α-Hemihydrate (CaSO4 . ½ H2O) has been shown to be a promising material to replace Portland Cement in some applications. The hydration of gypsum pastes goes through the process of saturation of the medium with Ca+2 and SO4-2 ions, then the physical phenomenon of crystallization, and finally the phenomenon of hardening, where the crystals formed precipitate producing Dihydrate (CaSO4 . 2H2O). Gypsum pastes harden very quickly, and their pumpability is impaired with thickening times of less than 20 minutes. For applications requiring longer pumpability times, the use of retarding additives is necessary. This research studied the effects of retarding additives in α-HH gypsum paste systems by varying the water-gypsum factor (FAG 0.4; 0.5 and 0.6) using a pressurized consistometer, under conditions of 54 °C and 9500 psi, with the aim of obtaining formulations with admissible thickening times for oil well cementing applications. The results showed that it was possible to develop paste systems with varying thickening times, with intervals of more than 120 minutes. The 0.5 FAG system proved to be more stable at the same retarder concentrations when compared to the 0.4 and 0.6 FAG systems.

Enhancing the mechanical properties and hydration of cement paste by incorporating GO/nano In(OH)3 composite with high specific surface area

Graphene oxide (GO) is an ideal two-dimensional material for enhancing the flexural strength and toughness of cement-based materials due to its exceptionally large theoretical specific surface area and Young's modulus. However, the smooth surface of GO results in weak bonding with the cement matrix. Additionally, GO has a tendency to agglomerate in cement paste, resulting in significant decreases in its specific surface area and its beneficial effect in cement-based materials. In this paper, GO modified by nano In(OH)3 (IGOs) was successfully prepared for improving its specific surface area, dispersion and bonding with the cement matrix. These improvements were achieved by utilizing urea and sodium citrate as nanoparticle stabilizers to adjust the pH of solution. Furthermore, the optimal compositions of IGO material as described above and its effects were identified through investigating the impact of IGOs on the cement paste.

Understanding the influence of ultrasonic power on the hydration of cement paste

This paper studied the dispersion and hydration of cement paste prepared by power ultrasound (PUS)-assisted mixing technology. The ultrasonic power used were 0 W, 480 W and 912 W. The hydration process and microstructure were tested by using isothermal calorimetry, X-ray diffraction (XRD), thermogravimetric-differential scanning calorimetry (TG-DSC), solid-state nuclear magnetic resonance silicon (29Si-NMR) spectroscopy, mercury intrusion porosimetry (MIP), attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, scanning electron microscopy (SEM) and energy dispersive spectroscopy (SEM‒EDS). The results indicated that the dynamic hydration kinetics of cement paste under ultrasonic irradiation can be categorized into crystallization nucleation and growth (NG), phase boundary (I) and diffusion (D) processes. The apparent rate constant KNG in the NG process and KI in the I process both increased as the ultrasonic power increased, suggesting that PUS-assisted mixing accelerated the early hydration process. PUS shortened the dormant period and enhanced the total hydration heat release. The capillary pores and gel pores were both reduced at 28 days. Similarly, compared with those of C0 and C480, the gel porosities of C912 decreased by 35.17% and 31.87%, respectively. In addition, the mean chain length of the C–S–H gel increased with increasing ultrasonic power, which effectively filled the nanoscale defects. PUS improved the early strength and increased the strength at late hydration ages. Compared with that in the reference group, the compressive strength in the C912 group was enhanced by 26.1% at 1 day and 18.3% at 28 days. These findings demonstrate that power ultrasound-assisted mixing is advantageous for enhancing the sustainability of building materials, thereby contributing to the development of future circular buildings.

Comparison of the effects of carbon-based and inorganic nanomaterials on early cement hydration

This study delves into the impact of nanomaterials on early cement hydration, aiming to elucidate their mechanism of action. Four nanomaterials were selected, including carbon-based nanomaterials (multi-walled carbon nanotubes (CNT) and graphene oxide (GO)) and inorganic nanomaterials (nano-SiO2 and nano-CaCO3). Initially, the zeta potential was employed to examine nanomaterial adsorption on relevant ions in simulated solutions. Subsequently, SEM NMR, XRD, and TGA were utilized to assess the influence of different nanomaterials on hydration product morphology, content, and structure. Utilizing the Krstulovic-Dabic model, the hydration kinetics based on the heat of hydration in cement paste containing nanomaterials was simulated. Results revealed nanomaterials exhibited stronger Ca2+ ion adsorption than cement particles, with CNT and GO particles displaying weaker adsorption relative to SO42- ions. Conversely, nano-SiO2 and nano-CaCO3 particles exhibited a stronger adsorption capacity for Ca2+ ions than SO42- ions. This robust adsorption facilitated hydration product generation, yielding fine and regular C-S-H particles in carbon-based nanomaterial-containing cement pastes, contrasting with coarse and irregular particles in inorganic nanomaterial-containing pastes. Nanomaterial introduction increased polymerization and the average chain length of hydration products. Furthermore, it heightened exothermic peak intensity and total exothermic amount, while reducing the induction period and exothermic peak length. Hydration kinetics, simulated through the Krstulovic-Dabic model, aligned with the nucleation and growth (NG)-phase boundary reaction (I)-diffusion (D) process. In the NG stage, nanomaterials accelerated hydration by reducing reaction stages (n) and increasing the rate constant (K1'). In the I stage, hindered Ca2+ ion migration led to decreased K2', slowing hydration. Stage D witnessed a rapid decline in K3'.

Effect of recycled brick powder with various particle features on early-age hydration, water state, and rheological properties of blended cement paste in the context of 3D Printing

Partially replacing cement with recycled brick powder (RBP) in 3D printing concrete (3DPC) is an effective way to reduce carbon footprint and resolve the construction and demolition waste disposal problems. Understanding the impact of RBP on the rheological parameters of 3DPC is of utmost importance, given its critical role in ensuring the requisite printability. Here, three types of RBPs with various particle features were prepared by mechanical grinding, and their effects on several rheological parameters of cement-RBP pastes were characterized by hydration kinetic and water state distribution. Results show that incorporating RBP increases the growth rate of static yield stress due to the nucleation effect in the first 2 h. The initial static yield stress and thixotropy of cement-RBP pastes are governed by morphology effect and Debye length, while the mean interparticle distance and water lubrication effect under shear process play the dominant role in dynamic yield stress. RBP can promote the evolution of structural build-up and thixotropy of cement paste, all of which have a significant positive impact on filament shape retention and structural stability of 3DPC.

Effect of Poly(ethylene glycol)–Poly(propylene glycol) Triblock Copolymers on Autogenous Shrinkage and Properties of Cement Pastes

This study investigates the hydration, microstructure, autogenous shrinkage, electrical resistivity, and mechanical properties of Portland cement pastes modified with PEG-PPG triblock copolymers with varied molecular weights. The early age properties including setting time and hydration heat were examined using the Vicat test and isothermal calorimetry. The hydration products and pore size distribution were analyzed using thermogravimetric analysis (TGA) and nitrogen adsorption, respectively. Mechanical properties and electrical resistivity were evaluated using the compressive strength test and electrochemical impedance spectroscopy (EIS). It was shown that the addition of the copolymers reduced the surface tension of the cement paste pore solution due to the presence of a hydrophobic block (PPG) in the molecular structure of the copolymers. The setting time and hydration heat were relatively similar in the control paste as well as the pastes modified with the copolymers. The results showed that copolymers were able to reduce the autogenous shrinkage in the paste due primarily to a reduction in pore solution surface tension. TGA showed a slight increase in the hydration degree of the paste modified with the copolymers. The compressive strength was reduced in the pastes modified with the copolymers that showed an increased volume of air voids. The addition of copolymers did not affect the electrical resistivity of the pastes except in the case where there was a large volume of air voids, which acted as electrical insulators.

Heat of hydration, water sorption and microstructural characteristics of paste and mortar mixtures produced with powder waste glass

Heat of hydration, water sorption and microstructural characteristics of paste and mortar mixtures produced with powder waste glass

Improvement on engineering properties and volumetric stability of alkali-activated slag-based composite cementitious material with rice husk ash and magnesium oxide

This study used rice husk ash (RHA) and magnesium oxide (MgO) to improve the engineering properties and volumetric stability of alkali-activated slag-based cementitious material. Experimental results found that when the amount of slag substituted by RHA increased from 0% to 20%, the initial setting time was extended from 15 to 20 min, and the final setting time was shortened from 35 to 30 min for the paste without MgO. The optimal substitution amount of RHA was 10%, which had the maximum compressive strengths at ages of 28 and 56 days to achieve 104.44 and 102.43 MPa for the paste without MgO, respectively. The drying shrinkage of paste without MgO increased with both the increase of RHA from 0% to 20% and ages from 3 to 56 days. With RHA, the drying shrinkage substantially decreased with the substitutions of MgO from 0% to 2.0% and almost remained steady after ages of 7 or 14 days. The optimal amount of RHA to replace slag was less than 10% and the optimal content of MgO was less than 1%, which can effectively improve the volumetric stability and reduce the heat of hydration of paste.

Impact of synthetic C-S-H seeds on early hydration and pore structure evolution of cement pastes: A study by 1H low-field NMR and path analysis

C-S-H seeds are highly-efficient in promoting hydration but not compromising the long-term performances of cement. Unfortunately, mechanisms of the C-S-H seeds properties affecting the early-age performances of cement are not very well understood. In this study, the influence of hydrothermal synthetic conditions on the C-S-H seeds properties is firstly investigated, followed by revealing the correlations of C-S-H seeds properties, hydration kinetics, and pastes performances by using in situ 1H LF-NMR and path analysis. It is found that low reactant concentrations and calcium-to-silicon ratios facilitate the production of C-S-H seeds with small size and high purity. Using C-S-H seeds with high effective surface area, i.e. nano-sized and high purity, the acceleration period of cement starts within 2 h and ends after 6 h, which in turn results in a refined pore structure and an enhanced strength, particularly at 12 h. An increased CH content leads to a decreased C-S-H growth rate.

Roles of diatomite in hydration, microstructure and strength development of cement paste

The production of cement has a significant environmental impact, and the use of mineral admixtures can mitigate this impact by reducing the clinker rate. Diatomite powder (DP) possesses unique properties, such as micronized and sub-micronized porous structures, and a large specific surface area, making it an ideal cement replacement. To gain a better understanding of the mechanisms underlying its performance as a cement replacement, the reference used was quartz powder (QP) in this study, and zeta potential tests were conducted to characterize the surface chemical properties of DP. Subsequently, how it affects the cement paste hydration, microstructure and strength development was investigated. Results revealed that DP, owing to its sub-micronized porous structure and chemical composition, exhibited a higher affinity for Ca2+ ions compared to QP, which significantly affects the formation of C-S-H. This heightened affinity facilitated the nucleation and growth of C-S-H, leading to a shortened hydration induction period. Furthermore, the incorporation of DP into cement paste resulted in a refinement of the pore structure. This enhancement is due to the relatively small particle size of DP, its chemical reactivity, and its surface affinity for uniform distribution of hydration product. Notably, the DP-hydration interface exhibited significantly higher strength compared to the interface between QP and hydration products. As a result of improving pore structure and strengthening the DP-hydrate interface, the cement paste blended with DP demonstrated compressive strength comparable to that of pure cement paste and considerably higher than the cement paste incorporating QP.