Blended Cement Pastes Research Articles

Experimental and theoretical study on the physico-mechanical characteristics and radiation shielding capability of hardened alumina sludge waste-cement pastes containing MnFe2O4-nanoparticles

This research investigates the impact of incorporating low-cost MnFe2O4 spinel nanoparticles (MF-NPs) at varying concentrations (0.5, 1, and 2 mass%) on the mechanical and physical properties of blended cement pastes. These pastes were produced by replacing different proportions (5, 10, and 15 mass%) of ordinary Portland cement (OPC) with activated alumina sludge waste (AAS), to promote sustainability. Also, the research examined the gamma radiation shielding effectiveness of certain hardened composites against a 137Cs gamma radiation source with an energy of 661.64 keV using a NaI (Tl) detector (Oxford Model) with 3″ × 3″, amplifier and 16 k multi-channel analyzer. The linear attenuation coefficient (LAC) of all the studded samples were calculated theoretically using a Monte Carlo code MCNP-5 code. The gamma radiation shielding properties were analyzed in depth using a Monte Carlo code MCNP-5 simulation model. The theoretical and experimental results for LAC were found to be in complete agreement. Phy-X/PSD software was applied to estimate the mass attenuation coefficient (MAC) for gamma radiation at various energies, as well as the effective atomic number (Zeff), mean free path (MFP), half-value layer (HVL), and tenth-value layer (TVL). The findings demonstrated that the addition of 0.5% MnFe2O4 nanoparticles (MF-NPs) to blended cement pastes exhibited the best physical and mechanical characteristics, as well as the most effective gamma radiation shielding.

Effect of Activated Siliceous Wastes Incorporated as Mineral Admixtures on the Rheological Properties of Cement Paste: Insights into Their Physicochemical Interactions in Suspension.

Mechanical grinding is a common method used to enhance the pozzolanic activity of tailings, and these activated tailings can be used as supplementary cementitious materials in cement production. However, the addition of activated tailings usually reduces the workability of cement paste, and the mechanism of influence of different minerals in tailings on workability varies. In this study, three kinds of principal silicate minerals in tailings-quartz, feldspar, and mica-were mechanically activated. The influence of these activated minerals on the rheological properties of cement paste were studied in the absence or presence of PCE (polycarboxylate ether) superplasticizers, and the influence mechanism was investigated using rheology, TOC, contact angles, zeta potential, XPS, ICP-OES, and XRD. The results showed that quartz has the highest fluidity, and mica has the lowest. An increase in hydrophilicity decreased the flowability of the blended cement paste. The increase in the metal cation dissolution rate was the main reason for the decrease in the fluidity of PCE-blended cement pastes. The knowledge gained provides a valuable reference for the utilization of activated tailings in cement production.

Mechanical properties, microstructure and life-cycle assessment of eco-friendly cementitious materials containing circulating fluidized bed fly ash and ground granulated blast furnace slag

To reduce CO2 emission from the cement industry and solve environmental issues caused by the accumulation of circulating fluidized bed fly ash (CFA), this study aimed to prepare eco-friendly cementitious materials using CFA and ground granulated blast furnace slag (GGBS) as supplemental cementitious materials. The hydration properties, reaction kinetics, microstructure and life-cycle assessment of blended cements were investigated. The results showed that the compressive strengths of the blended cement samples containing 10 % CFA and 20 % GGBS increased by 7.3 % and 5 % at 7d and 28d, respectively, compared to the pure cement paste. The hydration process was characterized using isothermal calorimetry and analyzed by the Krstulovic-Dabic (K-D) model. The blended cement paste with the best compressive strength exhibited the highest total hydration heat release throughout the hydration process, with extended reaction times. The synergistic effect of CFA and GGBS promoted the formation of C-(A)-S-H gel, consuming more portlandite and leading to a decrease in the most probable pore size and an increase in gel pore volume in the pore structure. From the perspective of cost, economy, and environment, the normalized strength cost, energy consumption efficiency index, and CO2 intensity index can be reduced by 16.1 %, 27.1 %, and 33.3 % respectively. This work contributes to a better understanding of the synergistic mechanism in the CFA-GGBS blended cement system, and serves as a significant reference for the development of economical and eco-friendly cementitious materials.

Waste glass powder as a high temperature stabilizer in blended oil well cement pastes: Hydration, microstructure and mechanical properties

Recycling waste glass for diversified utilization has received increasing attention in recent years. This work aimed to reuse waste glass powder (GP) as a high temperature stabilizer to replace silica flour (SF) in blended G class oil well cement (GOWC) pastes. Blended pastes containing 40 % and 66.7 % GP were prepared and compared to pure GOWC paste and blended paste containing 40 % SF commonly used in the oil industry. Under simulated field conditions in a steam injection well, these pastes were cured at 50 °C for seven days, followed by three rounds of thermal cycling curing at high temperature and high pressure (HTHP, 300 °C/13 MPa) conditions. The effects of GP on the hydration kinetics, hydration products, microstructure, and mechanical properties of hardened pastes were evaluated. The results demonstrated that the addition of GP or SF reduced the compressive strength of the pastes at 50 °C due to dilution effect. Compared with SF, GP exhibited higher pozzolanic activity, prolonged the induction period, and promoted the formation of more C-(N)-S-H gels with lower Ca/Si ratios, which led to an increase in the gel pores content of the matrix and partially compensated for the loss of compressive strength due to the dilution effect. Additionally, due to the pozzolanic reaction of GP, the content of CH in the matrix decreased and its crystal size became smaller. After three rounds of thermal cycling curing, the incorporation of GP significantly increased the compressive strength of the hardened pastes. The compressive strengths of the hardened pastes with 40 % and 66.7 % GP were 20.33 MPa and 22.25 MPa, respectively, which were 7.62 % and 17.79 % higher than those of the hardened paste containing 40 % SF. In addition, the compressive strengths of hardened pastes containing 40 % and 66.7 % GP after three rounds of thermal cycling curing decreased by 22.49 % and 5.52 %, respectively, compared to the pastes at the low-temperature stage, while that of the pure GOWC pastes decreased by 83.8 %. Characterization analyses indicated that GP could further reduce the Ca/Si ratio of the system, modulate the crystallization of the gels at high temperatures, and generate foshagite or xonotlite phases with high polymerization structure and thermal stability, instead of reinhardbraunsite. These products effectively refined pore structure and enhanced microstructure densification. Furthermore, the precipitation of Na+ ions during hydration did not affect the microstructure of the matrix. This study offers some guidelines for recycling waste glass, conserving raw materials, and producing sustainable blended cement pastes.

Hydration mechanism and microstructure evolution of recycled brick powder blended cement toward low-carbon and cleaner production

Recycled brick powder (RBP) as an aluminosilicate-rich material has shown great potential as a new type of supplementary cementitious material (SCM). However, the interaction mechanism between cement and RBP has not been clarified yet. In this study, the pore solution chemistry, phase assemblage and nano-structures of RBP blended cement paste were revealed. The pore solution chemistry indicated that RBP facilitates the dissolution of C3S and the precipitation of C-S-H, but inhibits the precipitation of CH. Hydration kinetics modelling results showed that RBP accelerates the nuclei formation but retards the growth of hydration products during boundary nucleation and growth process. FIB-TEM and thermodynamic modeling results demonstrated that the additional [Si] and [Al] ions dissolved from RBP contribute to the reactions: (1) the [Si] and [Al] react with the CH to form C-A-S-H gel with Al/Ca and Si/Ca molar ratios of 0.32 and 0.62, respectively; (2) the [Si] and [Al] reorganize to form nano clusters, such as hydrotalcite-like phase, AFt nano-crystals, AFm phase and C-(A)-S-H gel. Therefore, blended mortar with 30–45 % RBP replacing cement has slight or no late-age mechanical properties loss and presents 25.2–30.3 % decrease in chloride ion diffusion coefficients. Additionally, compared to blended cement utilizing traditional SCMs, like FA and GGBFS, RBP blended cement presents a 6.4–26.1 % reduction in cost and 21.4–41.6 % decrease in natural resource consumption, which contributes to great economic and environmental benefits.

Rheology of binary cement paste system blended with silica fume and alccofine

<p>The flow properties of the binary cement paste system added with supplementary cementitious materials, effect of polycarboxylate based superplasticizer dosage and their influence on the yield stress and the plastic viscosity were studied. The cementitious materials under the study are silica fume and alccofine. Both the plain cement and the binary cement paste system were considered and tested. A comparative study between the plain cement paste without any additions, silica fume blended cement paste and alccofine blended cement paste was performed. The addition of cementitious materials varies in the range 10%, 20% and 30% and the superplasticizer dosage varies in the range 0.5%, 1.0%, 1.5%, 2%, 2.5% and 3% in the mini-slump flow test and the saturation point was determined to be 2% in both the cases of silica fume and alccofine. The setting time and compressive strength testing on the cement paste considered the superplasticizer dosage up to saturation point. The flow characteristics are broadly the same among the binary paste systems. The setting time results indicated the increase in setting time with increase in cementitious additions and with increase in superplasticizer dosage. The higher percentage substitution of cement with silica fume and alccofine resulted in decrease in compressive strength due to the simultaneous acceleratory and retarding effects of cementitious additions and the superplasticizer. The results of the rheological measurements revealed that silica fume possess greater elasticity than that of the alccofine which possess greater yield stress and plastic viscosity.</p>

Rheological behavior and early-age hydration performance of blended cement pastes incorporating recycled brick powder and slag

This study focuses on blended cement pastes incorporating recycled brick powder (RBP) and slag. The effects of RBP and slag on the rheological behavior and early-age hydration performance of blended cement pastes with different substitution levels ranging from 0 % to 40 % have been studied by testing mini-slump flow, rheological properties, hydration products, pore structure, and phase distribution. The results show that the incorporation of RBP reduces the fluidity by 3.8 %-24.6 % and increases the yield stress of pastes by 4.1 %-53.4 %, while the combined use of RBP and slag proves effective in controlling the rheological properties. Furthermore, the addition of RBP and slag significantly reduces the hydration products and increases the total porosity of blended cement pastes by 4.3 %-16.9 % at 24 h. Notably, RBP and slag accelerate Portland cement hydration in early-age stage, attributed to nucleation and dilution effects. These findings offer valuable insights for the application of RBP in low-carbon cementitious materials.

Analysis of the synergistic effects of micro silica on the mechanical and durability properties of geopolymer concrete incorporating phosphogypsum

Geopolymers are developed by activating aluminosilicates with alkali solutions, stand as inorganic cementitious materials. Their distinct advantages over Portland cement render them highly attractive in the pursuit of carbon neutrality. Moreover, the manufacturing of geopolymers results in notably lower CO2 emissions when contrasted with conventional cement production methods. The industrial byproducts fly ash (FA), phosphogypsum (PG) and micro silica (MS) contained the alumna and silica which can be used for the development of the geopolymer concrete (GPC). This study presents the various proportions of PG content, ranging from 8 % to 40 %, were utilized as a partial substitute for FA, along with MS proportions ranging from 2 % to 10 %, in the preparation of GPC. The alkaline solution was standardized at 12 M of NaOH, and the alkali-to-binder ratio was set at 0.45. The compressive strength, RCPT, sorptivity, water absorption and porosity tests have been conducted for the GPC. The maximum compressive strength of the GPC was 61.53 MPa obtained for FPM8. The compressive strength of the GPC rose with the increasing percentage of MS, peaking at 8 %. The porosity, sorptivity and water absorption were also resulted minimum for the mix FPM8. The scanning electron microscope (SEM) images show the presence of calcium alumino silicate hydrate (C-A-S-H) gel in the specimens, resulting in enhanced mechanical properties and heightened strength of the blended cement paste. The environment impact assessment analysis of the GPC also show that the developed specimens emit less carbon in comparison to the conventional concrete. Hence, the developed GPC from the FA, PG and MS can be used in the application of the sustainable construction work.

Advances in the understanding of alkaline waste materials as potential eco-pozzolans: Characterisation, reactivity and behaviour

This paper explores the potential of three industrial alkaline waste materials – concrete construction and demolition waste (CDW-C), white ladle furnace slag (LFS) and biomass ash (BA) – for use as secondary raw materials in the manufacture of future eco-cements with a reduced carbon footprint. Circularity is one of the key strategies behind the circular economy, the cement industry roadmap and the climate neutrality targets set for 2050. The three materials were characterised using various instrumental techniques (XRF, laser, BET, XRD–Rietveld, SEM/EDX, FTIR, TG/DTA and NMR) and their chemical reactivity, the changes in their mineralogical phases and the thermodynamic stability within the pozzolan/lime system were determined. Finally, their physical and mechanical behaviour in binary cement pastes at replacement proportions of 7 % and 20 % over 90 days of curing were analysed. The results obtained show that these alkaline waste materials are different in nature and composition to standard pozzolans, with the LFS containing fluorine and the BA containing sulphates, potash and chlorides. The standard combined water test showed different levels of chemical reactivity (BA > LFS > CDW-C). Analysis of the materials’ composition, mineralogical phases and thermodynamic stability over 90 days of reaction in the pozzolan/Ca(OH)2 system revealed that hydrogarnet was the stable phase in the LFS cement paste, while in the BA and CDW-C pastes ettringite and CSH and C-(A)-SH gels, among others, were the stable phases. All the blended cement pastes with 7 % and 20 % replacement content met the physical requirements and maintained the strength category of the starting cement.

An efficient method for determining the pozzolanic reaction degrees of low-calcium supplementary cementitious materials in blended cement pastes

The pozzolanic reaction degree of supplementary cementitious materials (SCMs) is a crucial parameter influencing the performance of SCM-blended concrete. Although several methods, such as partial-or-no-known-crystal-structure (PONKCS) analysis with X-ray diffraction (XRD) testing and image analysis, have been developed to estimate the pozzolanic reaction degree of SCMs, they have their own challenges in achieving reliable estimation. Ethylenediaminetetraacetic acid (EDTA) with NaOH is an efficient and reliable agent for selectively dissolving calcium-rich phases (e.g., cement clinkers and hydration products) without dissolving low-calcium SCMs. In this study, the ionic selective dissolution method (ISDM) that combines the use of an EDTA–NaOH dissolving agent and inductively coupled plasma–optical emission spectroscopy is developed to efficiently and reliably determine the pozzolanic reaction degree of low-calcium SCMs. Furthermore, the chemical compositions of aluminium-incorporated calcium–silicate–hydrate gel are determined via the ISDM coupled with the Rietveld analysis of XRD data, according to mass conservation principles.

Abrams’ Law Formulation for Blended Cement Paste Incorporated with Ground Ferronickel Slag

Ground ferronickel slag (GFS) is a form of an industrial waste by-product generated during the smelting process of nickel ore that has been crushed and ground into fine powder. GFS is a pozzolanic substance that may be employed as an environmentally beneficial binding agent when blended with Portland cement. This research aims to apply the Abrams Law formulation to blended cement combined with GFS. GFS was utilized as a Portland cement composite (PCC) replacement at varying percentages of 0, 10, 20, 30, 40, and 50 wt.%. The blended cement paste incorporated with GFS was tested at three water to cementitious material ratio (w/cm) levels of 0.4, 0.5, and 0.6. After samples have been made, a compressive strength test is carried out. The research results showed that at 28 days, the optimum amount of GFS was found in the percentage of 20 wt.% induced the compressive strength by 40.41 MPa with a w/cm of 0.4. The equations based on Abrams’ Law have been proposed for estimating the correlation of 28-day compressive strength with w/cm in the range from 0.4 to 0.6. In addition, the hardened densities of binary blended cement paste were investigated. It was found that the density decreased with an increase of w/cm. The proposed equations provide the beneficial interpretation for estimating the compressive strength of blended cement paste based on the w/cm..

Understanding the dynamic rheological property of cement paste blended with steel slag powder: From interparticle force and physico-chemical parameters of view

The blending of steel slag powder with cement can mitigate the carbon footprint of cementitious composites. The rheological properties of cement pastes are well known to be related to interparticle forces. However, the magnitude of the interparticle force depends on many physico-chemical factors. The influence of various factors on interparticle forces is not yet clear, making it difficult to control the rheological properties. In this paper, the interparticle force of steel slag powder blended cement paste was quantified and its relationships with dynamic rheological properties and basic physico-chemical parameters were explored. By means of this, the interparticle force was confirmed to could explain the effect of steel slag powder on the dynamic rheological properties of cement paste within 1 h. Moreover, how physico-chemical parameters affect the interparticle forces was clarified. A cement paste with large particle size and apolar surface energy, as well as small potential square, Debye length and small polar surface energy, can exhibit large interparticle force and high dynamic yield stress and plastic viscosity. A simple formula calculating interparticle force from basic parameters was proposed, which is believed to effectively and practically regulate the interparticle force. The relationships between interparticle forces, physico-chemical parameters, and rheological properties provide an effective reference for regulating the dynamic rheological properties of cement paste through fundamental parameters.

Calcined schist as promising ordinary Portland cement substitution: C3

AbstractAn effective method to make cement and concrete more sustainable is to blend them with the proper supplementary cementitious materials (SCMs). This study evaluates a pair of schist‐type materials with slightly different phase compositions, as a partial replacement for ordinary Portland cement (OPC). Materials received from several mines in ground powder form were studied by X‐ray diffraction, thermogravimetric analysis (TGA), and scanning electron microscopy. According to the TGA results, the activation procedures for the candidate SCMs were determined. The as‐received powders were heat treated in three different decomposition regimes (30%, 50%, and 80% of the total weight losses during thermal decomposition). These regimes corresponded to the activation level of the potential SCMs due to the de‐hydroxylation of the clay‐type minerals within them. Pozzolanic reactivity (pozzolanicity) of untreated as well as treated powders were estimated via electrical conductivity measurements in saturated calcium hydroxide solution. Blended cement pastes with 30 wt.% of OPC substituted with calcined clay‐type materials have developed mechanical properties equal to those of pure cement (100 wt.% OPC) paste after 28 days of hydration time. Two blended cement pastes prepared with candidate SCMs were compared to 100% OPC and OPC composite paste with metakaolin, which is regarded in the literature as a standard.

Pozzolanic performance and characteristic analysis of binary blended cement incorporating ceramic polishing sludge

The waste generated during ceramic polishing is typically disposed of in landfills rather than being recycled within the production facility, potentially causing environmental harm. This study aims to enhance industrial waste utilization and reduce CO2 emissions in the cement industry by investigating the feasibility of incorporating ceramic sludge from polishing processes into an innovative binary blended cement. Different binders were prepared with varying amounts of ceramic polishing sludge (CPS), ranging from 10% to 50%, and tested against the ASTM C595 standards. The results were compared with those of ordinary Portland cement (OPC). This approach involves evaluating the pozzolanic activity and conducting an advanced characterization assessment of CPS and binary blended ceramic polishing sludge cement (CPSC) paste. This study employed a combination of physical, mechanical, and chemical tests, including setting time, particle size distribution (PSD), Brunauer-Emmett-Teller (BET) specific surface area, compressive strength, X-ray diffraction (XRD), scanning electron microscopy (SEM), heat of hydration, and differential scanning calorimetry/thermogravimetric analysis (DSC/TGA). The results indicated that CPS can be used as a pozzolanic material to create innovative binders with properties comparable to those of OPC. The Strength Activity Index (SAI) values affirmed the pozzolanic properties of CPS, exceeding 75% for up to 40% CPS replacement. Incorporating CPS in the blended cement resulted in a slower rate of cement hydration, leading to prolonged setting times and reduced early strength development. Although the compressive strength decreased with increasing CPS content, it remained within the acceptable ASTM C595 limits with up to 50% replacement. Nevertheless, the optimal replacement level of OPC with CPS was determined to be 50%. Furthermore, CPS substitution reduced the dry density and improved the water absorption and apparent porosity, reflecting microstructural changes. The SEM images revealed that the blended CPSC had a lower apparent porosity than the pure OPC. The DSC/TGA analysis demonstrated that the blended cement had a lower calcium hydroxide content and higher silica than pure OPC.

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.

Evaluation of mechanical performance, corrosion behavior, texture characterization and aggressive attack of OPC-FMK blended cement pastes modified with micro Titania

Building constructions are vulnerable to a major financial loss due to the dangerous degrading process of steel corrosion in reinforced concrete, which requires frequent repairs. This study examined the durability of steel cement-based covers and steel corrosion in two severe media, NaCl and MgSO4. The degree of penetration of these harmful ions was determined by monitoring the mechanical properties and porosity profile (using the N2-adsorption/desorption technique) of cement-based steel covers made from OPC and fine metakaolin (FMK) reinforced by micro-titania (MT). Additionally, after the immersed steels were exposed to solutions containing 7% NaCl and 7% MgSO4 for four months, the steel corrosion rates (CR, mpy) were assessed. The results demonstrated that blending OPC by FMK up to 30% could develop mechanical properties similar to plain OPC at later hydration periods of 28 and 90 days. XRD and TGA/DSC analyses connected this behavior to the emergence of novel phases, namely strätlingite and hydrogarnet, in OPC/FMK combinations. Better mechanical performance was demonstrated by blended mixes containing between 1% and 3% MT in all curing media. The replacement of OPC with 30% FMK in the presence of 3% MT resulted in significant changes in the porous system from macro to meso-nature, as confirmed by the BET and BJH models. Under normal, sulphate, and chloride curing, respectively, the maximum pore diameters (dpmax) decreased by 66.19%, 78.40%, and 79.14%. When CSH clusters were observed under a scanning electron microscope (SEM), they seemed to be symmetrical and organized, similar to floral crystals. This development is partially attributed to micro TiO2. Based on CR values, it was found that steel corrosion was higher in MgSO4 solutions than in NaCl solutions. Steel coverings made of OPC/FMK composites with 3% MT were able to reduce CR by 65.8% in MgSO4 solutions and by 56% in NaCl solutions.

Image enhancement and microstructure characterization of energy dispersive X-ray spectroscopy images of blended cement pastes

Energy dispersive X-ray spectroscopy (EDS) image analysis has been widely used to study the microstructure of cementitious materials, whereas in some cases the efficiency of the characterization suffered from the extremely long time for image acquisition. In this study, we proposed an EDS image analysis methodology including image enhancement, phase extraction, and characterization of reaction products. The guided filter and Logarithm correction were combined and employed to improve the resolvability of low-quality EDS images. Gaussian Mixture Model (GMM) algorithm was applied to segment the unreacted phases and two different groups of reaction products from the enhanced EDS images. Moreover, the spatial distribution and chemical composition of reaction products were characterized using the lineal-path function and simple lineal iterative clustering (SLIC) algorithm. Results showed that low-quality EDS images after enhancing could achieve the comparable performance with high-quality EDS images in terms of the phase proportions. This study offers a practical and effective methodology for enhancing and analyzing the low-quality EDS images, giving insights into the phase assemblage and microstructure evolution of cementitious materials.

Retardation effect of the pozzolanic reaction of low-calcium supplementary cementitious materials on clinker hydration at later age: Effects of pore solution, foreign ions, and pH

Clinker hydration at later age in blended cement pastes was found to be retarded by the pozzolanic reaction of low-calcium supplementary cementitious materials (SCMs). Various mechanisms were explored, including the consumption of pore solution, the presence of foreign ions, and pH-related effects. Experimental results indicated that the dissolution of the foreign ions from SCMs was a secondary effect. The primary cause of the retardation effect was the reduction in pH caused by the pozzolanic reaction. Aqueous precipitation tests yielded the following findings related to pH: (1) At lower pH levels, the precipitation of aluminium-incorporated calcium silicate hydrate(C–A–S–H) gel was reduced due to the decreased nano-adhesion force. (2) The morphology of C–A–S–H gel consisted of small spherical particles at lower pH levels, resulting in a denser capillary pore structure. The latter led to increased water retention within the fine gel pores but a reduced amount of pore solution available in the capillary pores for cement hydration.

The Characterization of Carbide Slag by Carbonation Curing and Its Enhancement Performance in Blended Cement Paste

The Characterization of Carbide Slag by Carbonation Curing and Its Enhancement Performance in Blended Cement Paste

Effects of dicalcium ferrite on hydration and microstructure of cementitious material

Dicalcium ferrite (C2F) is a key component in metallurgical slag, particularly steel slag. Nevertheless, its influence on cement hydration is unclear. This study investigated the composition and surface properties of synthesized C2F and its effects on the compressive strength, hydration heat, hydration degree, and microstructure of blended cement. The results indicated that C2F comprises small lamellar particles. Its incorporation into Portland cement reduces the hydration rate and cumulative hydration heat of blended cement. Despite its low hydration capacity, C2F actively engages in cement hydration, reacting with C-S-H, C4Ac0.5H12, and C4AcH11 to form C3(AF)S0.84H. Furthermore, the loose, lamellar structure of C2F reduces the compactness of the microstructure in blended cement paste. Consequently, C2F imposes a more substantial retarding effect on cement hydration than inert SiO2. This investigation contributes novel theories and insights into the retarding effect of steel slag on cement hydration.