Hydration Of C3A Research Articles

Functionality of silica nanoparticles on hydration mechanism and microstructure of tricalcium aluminate

In this paper, a detailed reaction mechanism of tricalcium aluminate (C3A) in presence and absence of silica nanoparticles (SNPs) within 24 hr of hydration was studied. The effect of SNPs on an early stage of hydration was assessed through XRD (mineralogical analysis), TGA (quantification of hydrated products), FTIR (analysing chemical bonding) and FESEM (morphological study). The results indicate that SNPs promote C3A hydration at the very early stage of hydration (10 min of hydration), after that retardation in C3A hydration was observed and the pattern of reaction is consistent up to 24 hr of hydration. The retardation might be due to the surface coverage of C3A grain by calcium silicate hydrate (C-S-H) and calcium alumina silicate hydrate (C-A-S-H), thus, the reactivity of C3A decreases. This study presents a detailed inside reaction mechanism of C3A hydration with SNPs, which will help in understanding the influence of other admixtures (such as superplasticizers, accelerators and retarders) in SNPs modified cementitious system.

Influence of Uranium on the Hydration Properties of the Cement Clinker Minerals

The influence of uranium simulated waste water on the hydration properties of the cement was studied by modern test methods such as TAM air, XRD, FTIR, and SEM-EDS. The results show that uranium can promote the hydration of mineral C3S, and inhibit the hydration of mineral C3A. By comparing scanning of hydration products, it was found that the existence of uranium significantly changed the morphology of clinker hydration products , but uranium had little effect on the type of clinker hydration product.

Influence of triethanolamine on mechanical strength and hydration performance of blended cement containing fly ash, limestone and slag

Triethanolamine (TEA) is known as a widely-used cement additive for regulating setting time, hydration process and mechanical strength. However, the working mechanism of TEA on blended cement with various kinds of minerals, has not yet thoroughly explored. This invesitigation focused on effects of TEA on the strength enhancement and hydration properties of the blended cementitious materials, containing fly ash, slag, limestone. Hydration heat evolution of the composite binder was studied by isothermal calorimetry. Pore size distribution was analyzed through mercury injection porosimetry (MIP), and the evolution of hydration products in the function of TEA was investigated by X-ray diffractometry (XRD), differential thermal analysis (DTA) and thermogravimetric analysis (TG). Microstructure and composition characteristics of hydration products were studied through scanning electron microscopy (SEM) equiped with energy dispersive X-ray spectroscopy (EDX). Results showed that strength enhancement effect of TEA varied when the component and proportion of cementitious materials altered. Containing 30% fly ash and 10% limestone, the composite binder got the optimal strength-enhancing effect to nearly 15%. When containing 30% slag and 10% fly ash, the composite binder obtained the worst strength-enhancing effect with about 5%. The addition of TEA prolonged the induction period, and enhanced the formation of AFt. With high aluminate glass phases, fly ash was vulnerable to be influenced by the complexation of TEA, and hence the pozzolanic reaction of fly ash was accelerated significantly, resulting in reduced content of Ca(OH)2 (CH) as well as increased production of hydrates. Limestone participated to accelerate the hydration of C3A, and provided microcrystals for the growth of hydrates. Slag was mainly composed of high calcium glass phases and was rarely impacted by the complexation of TEA. The findings would gain a comprehensive insight of TEA in affecting the hydration process of blended materials, and would provide expedient information on the technique to control the hydration progress of composite binder.

Combined effect of slag and clay brick powder on the hydration of blended cement

The slag from industrial byproduct and clay brick powder (CBP) from construction waste were used to replace 30% Portland cement for preparing blended cement. This research investigated the hydration heat, hydration products, microstructure and macro-mechanical properties of blended cement to reveal the combined effect of slag and CBP on hydration. The test results indicate that 30% slag and CBP can increase 11.4 ~ 13.7% peak value of C3S hydration, but the C3A hydration is more affected by slag than CBP. Meanwhile, the 144-h cumulative heat of blended cement hydration is reduced by 4.1 ~ 21.3% compared to Portland cement. The slag and CBP have an improvement effect on the mechanical strength of mortars before and after 90 d, respectively. The mechanical strength of mortars containing both slag and CBP can develop continuously for a long time and reaches the highest value of 53.5 MPa. The slag can consume more portlandite than CBP before 90 d, the portlandite contents in C7B0 and C7B100 at 90 d are 11.6% and 13.3%, respectively. But after 90 d, the CBP will react with more portlandite for its pozzolanic activity. Some different morphologies of CASH can be observed in blended cement paste due to the variation of Al/Si and Ca + Mg/Al + Si in CASH. It could be concluded the combined effect of slag and CBP will led to a high hydration degree at an early stage and continuous hydration for a long time in blended cement.

Chloride Binding Capacity of Portland Cement System with Different Content of Tricalcium Aluminate

The binding of chloride ion has been reported as an effective way to reduce the risk of steel corrosion induced by the utilization of marine sources. In this study, effect of tricalcium aluminate (C3A) on chloride binding capacity of Portland cement paste was investigated; the setting time, compressive strength, and fluidity of cement-C3A system were also examined. The reaction mechanism of C3A and chloride ions was studied by X-ray diffraction (XRD) and thermo gravimetric analysis (TGA). The results showed that addition of C3A in cement paste could increase the compressive strength not only at the early age but also at the late age. The setting time was shortened obviously and the fluidity was reduced. The main reason was that fast hydration of C3A could hasten the formation of ettringite to consume free water, and also promote the hydration of the system. Furthermore, addition of C3A in cement paste could greatly promote the chloride binding capacity, and the main reason was due to the promoted formation of FS in hydrates. The investigation was expected to provide experience in promoting the chloride binding capacity of cement system.

Effect of Aluminum Sulfate on the Hydration of Tricalcium Aluminate

Aluminum sulfate (AS), as the main composition of alkali-free accelerator, was widely used to accelerate the setting and promote the early strength in the sprayed concrete. In this study, effect of AS on the hydration reaction of C3A was investigated, which is one of the most important cement clinker minerals in the early age of cement hydration. The hydration reaction and products of C3A-AS system were characterized with hydration heat test, X-ray diffraction, thermogravimetric analysis, scanning electron microscope, and thermodynamic modeling. Results indicate that AS could hinder the hydration reaction in the very early age but then accelerate C3A hydration by producing SO4-AFm, OH-AFm, and gibbsite. The findings are expected to provide theoretical guidance for the product research and engineering application of alkali-free accelerator.

Influence and mechanisms of active silica in solid waste on hydration of tricalcium aluminate in the resulting composite cement

Many industrial solid wastes are rich in silica (SiO2) which can be used as supplementary cementitious material (SCM) to replace part of Portland cement. Existing studies mainly focus on the impact of solid waste on tricalcium silicate (C3S) hydration. Since tricalcium aluminate (C3A) is the most reactive component of the Portland cement, it is of great interest t to investigate the effect of solid waste containing SiO2 on the hydration process of C3A. In this study, different amounts of nano-silica (nano-SiO2) were mixed with C3A and the hydration products after 72 h of hydration were analyzed by means of X-ray diffraction (XRD), Fourier Transform Infrared analyzer (FT-IR), Environment Scanning Electronic Microscope - Energy Dispersive Spectrometer (ESEM-EDS), X-ray Photoelectron Spectroscopy (XPS) and Solid-state Nuclear Magnetic Resonance (NMR). The results showed that nano-SiO2 can promote the hydration of C3A and stabilize the hydration products of C3A in the form of crystalline hydrogarnet (C3AH6). The formation of Si-O-Al bonds was also found in the hydration products. ESEM results revealed that the surface of the crystalline hydration products (C3AH6 particles) was covered by gel-like products. The results from the XPS and NMR analyses further confirmed that the negatively charged nano-SiO2 and the silicate anions can literally interact with C3A to produce calcium silicoaluminate hydrate (C-A-S-H) gel, whereas the formation of C-A-S-H is attributed to the substitution reaction of Al in the Si-O-Si network occurring on the surface of C3A. In addition to the reactive silica-aluminum component reacting with Ca(OH)2 to form additional calcium silicate hydrate (C-S-H) and C-A-S-H gels, the reactive silicon in solid waste can also undergo pozzolanic reaction with C3A to form C-A-S-H gel.

Hydration of cubic tricalcium aluminate in the presence of calcined clays

AbstractCalcined clay blended cements play a major role in cement industry's strategy to reduce CO2 emissions. During their hydration, an accelerated aluminate reaction is often observed to affect the sulfate balance. The objective of this study was to provide insights into the influence of different calcined clays on the hydration of cubic tricalcium aluminate (C3A). A cementitious model system consisting of cubic C3A, quartz powder, calcium sulfate and a model pore solution was investigated. The influence of three different calcined clays and one nanolimestone was examined by a successive replacement of the quartz powder and variation of the calcium sulfate. Heat flow and hydrate phase development were followed by isothermal calorimetry and quantitative in‐situ X‐ray diffraction. Accelerated ettringite formation and sulfate depletion were observed for all calcined clays, while the nanolimestone exhibited the opposite effect. It was found that adsorption of SO4 ions and/or Ca‐SO4‐complexes at the surface of calcined clay particles is the main factor inhibiting retardation of the C3A hydration in absence of a silicate reaction. In the Al‐rich systems a retardation through sulfate adjustment seems to be impeded by additional Al ions, which react with Ca adsorbed onto and leached from the C3A surface.

Effect of carboxylated styrene–butadiene copolymer on the hydration of tricalcium aluminate in the presence of gypsum and calcium hydroxide

The clinker mineral tricalcium aluminate (C3A) determines largely the early hydration characteristics of Portland cement. Therefore, understanding the influence of the polymer on the hydration of C3A is contributed to clarify the mechanism of polymer on the early hydration of cement-based material. The hydration environment of C3A in Portland cement was simulated by using C3A mineral, gypsum ( $${\rm C}\bar{S} \cdot {\text{H}}_{2}$$ ) and calcium hydroxide (CH). The specimens, whose water cement ratio (mw/mc) was 0.4 and carboxylated styrene–butadiene (SB) copolymer cement ratio (mp/mc) was 0, 5, 10, 15 and 20%, were cured at 20 ℃/RH90% for 6 h, 12 h, 1 day, 3 days, 7 days and 28 days, respectively. The effect of SB copolymer on the system of C3A– $${\rm C}\bar{S}\cdot{\text{H}}_{2}$$ –CH was investigated by the combination of isothermal calorimetry, X-ray diffraction (XRD) and environmental scanning electron microscopy (ESEM). It was found that the SB copolymer retards C3A hydration and reduces the heat of hydration. The XRD results revealed that addition of SB copolymer inhibits the consumption of C3A, delays the conversion of ettringite (AFt) to calcium monosulfate aluminate hydrate (AFm), promotes the formation of hydrated calcium aluminate (C4AH13), and reduces the crystallinity of AFm.

Long-term hydration and microstructure evolution of blended cement containing ground granulated blast furnace slag and waste clay brick

This study focuses on the blended cement containing ground granulated blast furnace slag (GGBFS) and waste clay brick (CBP), with 30% and 50% Portland cement contents. The compressive strength, hydration kinetics, hydration products and microstructure of blended cement up to 365 d were investigated to explore GGBFS and CBP interaction in the blended cement. The results show that both GGBFS and CBP reduce the hydration heat of blended cement, but the GGBFS will accelerate the C3A hydration more significantly due to consuming more sulfate than CBP. The improvement effect of GGBFS on compressive strength mainly occurs before 90 d, while the reaction of CBP continues to improve the compressive strength after its drastic reduction at early age. The X-ray diffraction and thermogravimetry results prove that the blended cement containing both GGBFS and CBP shows a high hydration degree at early age and will continue to hydrate. Furthermore, the chemically bound water content and porosity in blended cement containing both GGBFS and CBP at 365 d are almost the same as those in Portland cement.

Effects of sulfates on the hydration of Portland cement – A review

Presented within is a critical overview of the effect of sulfates on cement hydration, properties, and optimum sulfate content in Portland cement. Calcium sulfate is used in Portland cement to control the C3A reaction to induce the optimum hydration of C3S to occur. The amount of calcium sulfate in the Portland cement influences the hydration, rheology, setting, phase assemblage, porosity distribution, and strength in cementitious materials. If added in excess, it can also lead to durability problems, thus a better understanding is needed about the mechanisms of sulfate on C3A and C3S hydration. The optimum sulfate content is well known as a key pathway to produce workable, good strength, and durable concretes. Despite many years of research, questions regarding sulfate optimization remain. Further investigation on the influence of clinker and calcium sulfate characteristics, the use of different supplementary cementitious materials and chemical admixtures, and the curing conditions on the sulfate demand of Portland cement are needed. The main methods used to determine the optimum SO3 content are reported, and the advantages and disadvantages are examined. Finally, recommendation for future research is also discussed.

Hydration Characteristics of Tricalcium Aluminate in the Presence of Nano-Silica.

Tricalcium aluminate (C3A) is the most reactive component of the Portland cement and its hydration has an important impact on the workability and early strength of concrete. Recently, nanomaterials such as nano-silica (nano-SiO2) have attracted much attention in cement-based materials because of its pozzolanic reactivity and the pore-filling effect. However, its influence on the hydration of C3A needs to be well understood. In this study, the hydration kinetics of C3A mixed with different percentages of nano-SiO2 were studied and compared with pure C3A. The hydration products were examined by different characterization techniques including XRD, XPS, and NMR spectroscopy and isothermal calorimetry analyses. The XRD results showed that the addition of nano-SiO2 promoted the conversion of the intermediate product C4AH13. The isothermal calorimetry results showed that the addition of nano-SiO2 significantly reduced the hydration exotherm rate of C3A from 0.34 to less than 0.1 mW/g. With the presence of nano-SiO2, the peaks for Q1 were observed in 29Si MAS-NMR measurements, and the content of Q1 increased from 6.74% to 30.6% when the nano-SiO2 content increased from 2 wt.% to 8 wt.%, whereas the proportion of Q4 gradually decreased from 89.1% to 63.6%. These results indicated a pozzolanic reaction provoked by the nano-SiO2 combined with aluminate structures generating C-A-S-H gel.

Reuse of UK alum water treatment sludge in cement-based materials

Alum salts are commonly used as coagulants in the purification of surface water for potable supplies. The resultant waste alumina-rich sludge is currently landfilled in the UK. This study aimed to valorise sludge by using heat-treated alum sludge as an additive in cement. Alum sludge was calcined at 475–1100 °C and then characterized to correlate physical and mineralogical changes with cementitious activity and engineering performance. Alum sludge calcined at 825 °C transforms to poorly crystalline η-alumina (eta) and has cementitious activity. The calcined sludge rapidly reacts with gypsum to form ettringite which leads to a shortening of the induction period and onset of alite hydration. Gypsum depletion leads to undersulfated C3A hydration which consumes ettringite to form monosulfoaluminate thereby inhibiting further alite hydration. The poorly crystalline η-alumina is metastable, transforming to highly crystalline α-alumina at 1100 °C. In pastes containing more crystalline sludges, alite hydration is enhanced because the undersulfated C3A reactions are avoided, leading to improved performance.

Regulations on the Hydration, Morphology, and Sulfate-Attack Resistivity of C3a with Micro/Nano-Silica Particles

Regulations on the Hydration, Morphology, and Sulfate-Attack Resistivity of C3a with Micro/Nano-Silica Particles

The effect of a polycarboxylate ether on C3A / CaSO4·2H2O passivation monitored by optical spectroscopy

Polycarboxylate ethers (PCEs) are widely used in construction, but the exact nature of their interaction with cement is still debated. Aiming at a better understanding of the role of tricalcium aluminate (C3A) in cement hydration, we assessed the potential of optical spectroscopy in combination with a water-soluble fluorescent organic reporter dye (S0586) to monitor the early hydration of C3A in the presence of 26 wt% CaSO4·2H2O (C3A26G-S) with and without PCE. As optical methods, steady-state fluorescence and diffuse reflectance (UV–VisDR) spectroscopy were employed. Phase characterization and particle size distribution were performed with in-situ X-ray diffraction (in-situ XRD) and dynamic light scattering (DLS). Our results show that fluorescence and UV–VisDR spectroscopy can be used to monitor the formation of metastable phases by the disaggregation of the dye S0586 in a cement paste as well as changes in ettringite formation. Addition of PCE slowed down the disaggregation of the dye as reflected by the corresponding changes of the dyes absorption and fluorescence. This prolonged induction period is a well-known side effect of PCEs and agrees with previous reported calorimetric studies and the inhibition of gypsum dissolution observed by in-situ XRD. This demonstrates that fluorescence and UV–VisDR spectroscopy together with a suitable optical probe can provide deeper insights into the influence of PCE on C3A-gypsum hydration which could be e.g., utilized as screening method for comparing the influences of different types of PCEs.

Effect of a novel starch-based temperature rise inhibitor on cement hydration and microstructure development: The second peak study

Temperature rise inhibitor (TRI) modifies the exothermic process of cement hydration at early age and mitigates the buildup of cumulative heat, which sheds new light on solving the thermal cracking issue. After the main hydration peak, a broader “second peak” appears and brings the cumulative heat back to normal level within 7 days (for additions less than 0.15%). This study shows that the “second peak” can be attributed, almost exclusively, to C3S hydration while triggered by C3A hydration. In a pure C3S system, the heat flow is depressed by TRI during the main hydration peak but never recovers after. In a monophase system composed of C3S, C3A and gypsum or a real cement paste, the ongoing precipitation of ettringite helps to pump out TRI polymer from the pore solution and eliminate the restriction on C-S-H nucleation. Afterwards, the precipitation of C-S-H accelerates again to form the “second peak”.

Effect of polycarboxylate ether on the expansion of ye'elimite hydration in the presence of anhydrite

Polycarboxylate ether (PCE), a commonly used superplasticizer, is known to influence the morphology of ettringite during the early hydration of C3A- and ye'elimite-containing cements. According to existing theories, such morphological changes may be crucial to the expansive behavior of these cements. This paper studied the expansion of ye'elimite-anhydrite pastes and found the use of PCE to reduce expansion after 4 days of curing. Hydration studies were conducted by calorimetry, X-ray diffractometry, scanning electron microscopy, mercury intrusion porosimetry, inductively coupled plasma–optical emission spectrometry, and X-ray microtomography. The results show that the influences of PCE on the morphology of ettringite and the hydration of ye'elimite were quite small after 2 days. Based on the crystal growth theory, the range of pores in which ettringite can grow was calculated to explain the observed expansive behaviors. The presence of ettringite nano-crystals in aluminum hydroxide was also revealed and considered as a possible expansion mechanism.

The accelerating mechanism of alkali free liquid accelerator based on fluoroaluminate for shotcrete

In this paper, the alkali free liquid accelerator based on fluoroaluminate (AAF) was prepared, and its effect on the setting time of cement paste and compressive strength of mortar was studied. The influences of the AAF on hydration process of cement paste, the composition and morphology of the C3A and C3S early hydration products were investigated by isothermal calorimetry, XRD and SEM analysis. The results show that the increase of the AAF dosage could greatly shorten the setting time of cement paste, but it also caused the 1d compressive strength of mortar to decrease. In addition, the early hydration conceptual models of the C3A and C3S in presence of AAF were established based on the experimental results.

Nano-CSH modified high volume fly ash concrete: Early-age properties and environmental impact analysis

To reduce the carbon footprint in concrete industry, fly ash (FA) as the solid waste has been widely used to replace cement in concrete material. Nano-CSH crystals is used in this research to improve the early age properties of concrete with high volume fly ash (HVFA). The characteristic analysis of the HVFA concrete incorporating nano-CSH crystals was first conducted including early age strength development and setting time. The changes in hydration and microstructure due to the adding of nano-CSH crystals were explored by the isothermal calorimetry, X-ray diffraction (XRD) and scanning electron microscopy (SEM) testings. The environmental impact of concrete mixes was assessed using CMLCA software. The FA dosage in cement was up to 70% and the investigated nano-CSH crystals were 0.5%, 1% and 1.5%. The results showed that addition of 1% nano-CSH crystals in HVFA60% mixes and incorporation of 1.5% nano-CSH crystals in HVFA70% mixes achieved the highest strength and the shortest setting time. The adding of nano-CSH crystals accelerated the hydration of C3A and C3S to form more C–S–H and ettringite responsible for concrete strength and densified the overall microstructure. Ca(OH)2 content is reduced at the age of 28 days due to its reaction with FA. Adding 1.5% nano-CSH crystals in HVFA70% mix and incorporating 1% nano-CSH crystals in HVFA60% mix decreased the total environmental impact by 6.39% and 4.36% compared to pure HVFA70 and pure HVFA60 mixes respectively.

Assessing the effect of alkanolamine grinding aids in limestone calcined clay cements hydration

Grinding aids are commonly used in cement manufacture to reduce electrostatic forces between powder particles and reduce agglomeration. Alkanolamines are known to also influence the hydration of the aluminate phases in cement. This study assessed the effect of TEA, TIPA and DEIPA addition on the hydration of LC3 systems. It was observed that these molecules have an enhancing effect on the aluminate reaction in LC3. They promote the hydration of ferrite and C3A, and lead to higher amounts of hemicarboaluminate and monocarboaluminate precipitated, which contributes to porosity refinement and mechanical properties. The rate of reaction of metakaolin is not affected by the addition of TEA, independent of the iron content of the clay.