Blended Cementitious Materials Research Articles

Exploring the hydration feature and microstructure evolution of MK-Q-LS blended cementitious materials with electrochemical techniques

The hydration process of blended cementitious materials is primarily affected by the effect mechanism of supplementary cementitious materials. This study utilizes electrochemical impedance spectroscopy (EIS) method to investigate the hydration kinetics of cementitious materials incorporating metakaolin (MK), quartz (Q) and limestone powder (LS). The experimental results reveal the influence of MK+Q+LS on the hydration kinetics, phase assemblage, and microstructure of the blended systems. Besides, the electrochemical impedance response of blended cement materials exhibits variation based on the MK contents and the curing age. Furthermore, the resistance of the continuously connected micro-pores (Rccp) in the blended cementitious material progressively increases throughout the hydration process. The inclusion of MK reduces the Rccp values at early ages, while contributes to an increase in Rccp values from 7 days onward. Additionally, positive correlations are established between the Rccp value and compressive strength/heat release across different MK contents and curing ages. The combination of Rccp values and other characterization method can effectively reveal the microstructure evolution process. Therefore, as a nondestructive method, EIS can be effectively applied to predict the hydration of cementitious materials and the mechanical properties.

Comparison of eggshell powder blended cementitious materials with ASTM Type IL cement-based materials

The present study explores the potential of producing an alternative ASTM Type IL portland-limestone cement (PLC) using up to 20 % eggshell powder (ESP) by mass as crushed ESP is similar in chemical composition to limestone. To this aim, the hydration, durability, and mechanical properties of the ESP blended cementitious system (using ASTM Type I/II portland cement) are compared to a commercially available ASTM Type IL cement system containing approximately 10 % limestone. ESP was prepared by milling for 3 h upon drying. Characterization of the ESP was done by x-ray diffraction for phase analysis, scanning electron microscopy for microstructural observation, and laser diffraction analysis for particle size distribution. A range of experimental tests were undertaken on both the ASTM Type I/II cement replaced with ESP and the ASTM Type IL systems. Results revealed that the utilization of up to 20 % ESP enhanced the heat of hydration secondary peak (C3A) by increasing the aluminate phase kinetics in the blended system at a favorable pH pore solution. Also, an accelerating effect on the setting time (increased by 20–100 mins) was observed for ESP samples. Chemical shrinkage, compressive strength, and degree of hydration were similar between the ESP and PLC samples. Results also revealed that ESP particles were relatively more effective in minimizing drying shrinkage by 20–35 %, which is attributed to possible internal curing effects. Overall, 10 % ESP blended with ASTM Type I/II cementitious system was similar to the 10 % limestone containing PLC system and could be used as waste material in producing an alternative ASTM Type IL cement.

Effect of steel slag powder and stone powder by-product from manufactured sand on the mechanical properties and microstructure of cementitious materials

Incorporating steel slag (SS) and stone powder (SP) as supplementary cementitious materials (SCMs) in cement and concrete products is an effective approach to promoting environmental protection. Recently, the effect of using steel slag alone is not satisfactory and the performance of blended cementitious materials is expected to improve after compounding with other admixtures. In this study, steel slag powder (SSP) and SP by-products from manufactured sand were employed with a total dose of less than 30% as a replacement for cement. The results revealed that the blended cementitious materials exhibited excellent mechanical strength and pore structure with the synergistic effect of SSP and SP. Compared to SSP or SP doping alone, the activity index of the composite 25% SSP and 5% SP was higher. SSP offers a considerable retardation effect on cement, while SP has little effect. Conversely, the effect of steel slag on mortar fluidity is neglected and SP decreases the fluidity. When 5% SSP is combined with 5% SP, the initial and final setting times of cement are increased by 39% and 25%, respectively. The reduction in mortar fluidity amounted to an insignificant reduction of only 0.7%, and the strength of the mortar at 28 d and 180 d was only lost by 7% and 5%, respectively. The coaction of 15% SSP and 15% SP was observed to promote the wollastonite generation, enhance the crystallization degree of xonotlite phases, decrease the microcrack widths, and optimize the pore structure of the blended cementitious materials.

Preparation of activated electrolytic manganese residue-slag-cement ternary blended cementitious material: Hydration characteristics and carbon reduction potential

The study aimed to develop a ternary blended cementitious material using activated electrolytic manganese residue (AEMR), slag, and cement as the primary raw materials. The research focused on investigating the hydration characteristics, micromechanical properties, and carbon emissions of this material. The findings indicate that the ternary blended cementitious material demonstrates favorable fluidity, compressive strengths, and microstructure when the AEMR dosage is below 15%. The compressive strength of the ternary blended cementitious material at 28 d exceeded 44 MPa with an AEMR dosage of 15%. The hydration characteristics suggest that the alkali-sulfate synergistic excitation system formed by the ternary blended cementitious material effectively enhanced the activity of slag and AEMR, leading to the production of more hydration products such as ettringite, C-(A)-S-H gel, and hydrotalcite. The smaller particle size of AEMR compared with cement and slag results in the unhydrated AEMR particles effectively filling the pores in the mixed mortar. This improvement in the pore structure ultimately leads to the increase of compressive strength. Moreover, the ternary system demonstrates effectiveness in reducing carbon emissions. Overall, this study presents a viable method for preparing AEMR-slag-cement ternary blended cementitious material.

Investigation on chloride migration behavior of metakaolin-quartz-limestone blended cementitious materials with electrochemical impedance spectroscopy method

Calcined clay and limestone powder composites offer a viable solution for reducing carbon emissions in building materials by allowing significant cement replacement. However, there is a need for further investigation into their impact on durability, especially for low-grade clays. In this study, different ratios of metakaolin and quartz powder are utilized to simulate various grades of calcined clay, while limestone powder is incorporated as a partial cement substitute. Initially, the influence of metakaolin content on rapid chloride migration was analyzed. Subsequently, various analytical techniques such as free water content, Mercury Intrusion Porosimetry (MIP), X-ray diffraction (XRD)/Rietveld method, and electrochemical impedance spectroscopy (EIS) test were employed to investigate the effects of metakaolin contents on the pore structure, phase assemblage, and electrochemical parameters of the blended cementitious system. The relationship between chloride migration coefficient and free water content, critical pore size, and impedance parameters was established to determine the key indicators for chloride migration. The study revealed that systems with partial metakaolin content demonstrate improved chloride resistance in the blended system, which could be predicted using Rct1 from the EIS test. Furthermore, the inclusion of metakaolin and limestone powder facilitated the formation of Monocarboaluminate (Mc) and Hemicarboaluminate (Hc), leading to the refinement of the pore structure and inhibition of chloride transport within the blended material. This study indicates the potential of low-grade calcined clay to enhance the overall durability of the blended cementitious system while contributing to carbon emissions reduction.

Hydrochloric acid resistance of mortars incorporating waste glass powder as cementitious materials

AbstractDespite numerous studies conducted on the potential of waste materials as cement substitutes, the resistance of mortars comprising such blended cementitious materials against acidic environments has seldom been investigated. This paper presents an investigation into the potential of waste glass powder (WGP) as a replacement for cement in enhancing the mechanical, and durability of cementitious materials subjected to acidic environments. The study examines the impact of WGP on the resistance of mortar to hydrochloric acid solution attack, with specimens containing 0%, 5%, 10%, 15%, 20%, 25%, and 30% WGP produced as cement substitutes. The tests were conducted on the cement mortar and paste after water curing for 7, 14, 28, 42, and 56 days. Initially, the pozzolanic activity index assessment, fresh density, water absorption, and compressive strengths during water curing times were evaluated. Subsequently, the performance of mortars, when subjected to hydrochloric acid solutions, was assessed, including mass loss, residual compressive strength, visual inspection, and microstructure features during 8 weeks of immersion in hydrochloric acid. The results of the study indicated that the incorporation of WGP led to improved hydrochloric acid resistance in the mortar. Furthermore, an increase in WGP content resulted in a reduced reduction in compressive strength against hydrochloric acid attacks as the ages progressed. The study revealed that the mortar containing 5% WGP as a cement substitute had the highest compressive strength compared to other specimens, and using 10% WGP as a supplementary cementitious material was comparable to the control mixture. Finally, the x‐ray diffraction pattern indicated that the specimen containing 5% WGP had a lower intensity of portlandite peaks than the reference specimen.

Functional and microstructural alterations in hydrated and freeze–thawed cement-oil shale ash composites

The oil shale industry generates a large amount of solid waste, the finer fraction of which can be utilized in civil engineering projects. However, for environmental, economic or technological reasons, oil shale is blended with other fuels, resulting in significant changes in the chemical composition of the residual ash. In this laboratory work, the fly ash from the combustion of oil shale with and without biomass in an industrial power plant was used as a binder substitute in cement-based materials to assess the potential of reuse of this ash. The hydration and pore structure of blended cementitious material subjected to long-term hydration and freeze–thawing has been characterized with a range of techniques, such as XRD, TGA and N2 physisorption. The results revealed that the ash type influences the phase assemblage related to the content of ettringite and monocarboaluminate, significantly affecting the volume of gel (1–6 nm) pores and small (10–30 nm) capillary pores. These microstructural changes impact the mechanical strength and water sorptivity properties in an opposite way after both long-term hydration and freeze–thawing. The results showed that the incorporation of ash obtained after combustion with biomass possesses higher mesoporosity and delays the hydration of cement, increases the total volume of gel (<6 nm) and small capillary pores (20–30 nm) of the composition, and deteriorates the functional properties after freeze–thawing.

Prediction Model Based on DoE and FTIR Data to Control Fast Setting and Early Shrinkage of Alkaline-Activated Slag/Silica Fume Blended Cementitious Material.

This study aims to develop a material-saving performance prediction model for fast-hardening alkali-activated slag/silica fume blended pastes. The hydration process in the early stage and the microstructural properties after 24 h were analyzed using design of experiments (DoE). The experimental results show that the curing time and the FTIR wavenumber of the Si-O-T (T = Al, Si) bond in the band range of 900-1000 cm-1 after 24 h can be predicted accurately. In detailed investigations, low wavenumbers from FTIR analysis were found to correlate with reduced shrinkage. The activator exerts a quadratic and not a silica modulus-related conditioned linear influence on the performance properties. Consequently, the prediction model based on FTIR measurements proved to be suitable in evaluation tests for predicting the material properties of those binders in the building chemistry sector.

Effects of Coal Metakaolin on the Mechanical Properties and Microstructure of High-belite Sulphoaluminate Cement.

The effects of coal metakaolin on the mechanical properties of high-belite sulphoaluminate cement under compressive loading were investigated. The composition and microstructure of hydration products at different hydration times were analyzed by X-ray diffraction and scanning electronic microscopy. The hydration process of blended cement was studied via electrochemical impedance spectroscopy. In particular, replacing a part of cement with CMK (10%, 20%, and 30%) was found to promote the hydration process, to refine the pore size, and to improve the compressive strength of the composite. The best compressive strength of the cement was achieved at a CMK content of 30% after 28 days hydration, being improved by 20.13 MPa, or 1.44 times relative to that of undoped specimens. Furthermore, the compressive strength is shown to correlate with the impedance parameter RCCP, which allows the latter to be used for nondestructive assessment of the compressive strength of blended cement materials.

Valorification of Egyptian volcanic tuff as eco-sustainable blended cementitious materials

Rhyolite rocks extend from southern Egypt to northern Egypt in the Eastern Desert, and no effective economic exploitation of them has been discovered so far. The pozzolanic activities of different volcanic tuffs (VT) supplied from the Eastern Desert located in Egypt have been investigated as natural volcanic pozzolan materials to develop new green cementitious materials for achieving sustainability goals in the construction field. Experimentally in this paper, the pozzolanic activities of seven diverse specimens of Egyptian tuffs taken with standardized proportions of 75:25% (Cement: volcanic tuffs) were investigated. Pozzolanic features of such tuffs are examined comparatively via strength activity index (SAI), TGA, DTA, and the Frattini’s test. Chemical composition, petrographic, and XRD analysis were also performed for tuffs samples. The pozzolanic reaction degrees were determined according to the compressive strengths at 7, 28, 60 and 90 days with different replacement ratios (20, 25, 30 and 40%) of tuffs samples. Additionally, the micro-filler effects in mortar and concrete were determined by measuring the heat of hydration in mortar samples and the compressive strength of concrete with different additive ratios for tuffs samples besides, the concrete slump test. The results show that TF6 gives a lower cement heat of hydration value which is less than 270 J/g at 7 days. Also, its performance in concrete is better than silica fume at late strength (28 days) since the concrete index value is 106.2% by compared to the concrete index of silica fume 103.9 and therefore it can be used as an alternative to high price and quality variable silica fume (SF) for producing high-performance green concrete. Due to the good pozzolanic behavior proved by nearly most volcanic tuffs, along with their low cost, this study will be profitable for very auspicious the use of Egyptian volcanic tuffs for developing sustainable and eco‑friendly blended cement.

Prediction of high strength ternary blended concrete containing different silica proportions using machine learning approaches

The most often utilized material in construction is concrete. High plasticity, good economy, safety, and exceptional durability are a few of its characteristics. Concrete is a type of structural material that needs to be strong enough to withstand different loads. The compressive strength of the concrete members is the most crucial mechanical characteristic of concrete because of its brittleness. Furthermore, concrete with ternary blended cementitious materials is a sophisticated composite material. The present study explores the binary and ternary blended concrete mixes with silica fume, ceramic powder, bagasse ash, and alccofine, to determine the compressive and flexural strength. Results of compression strength tests show that mixes, including ultra-fine alccofine, have higher strength. Furthermore, the impact of additional cementitious materials on the surface morphology was examined using scanning electron microscopy on the various mixes. This study investigates using linear regression, KNearest Neighbors (KNN), and Bayesian-optimized extreme gradient boosting to estimate the compressive strength of ternary blended concrete (BO-XGBoost). Using the coefficient of determination (R2), mean absolute error (MAE), and mean square error (MSE), the prediction results are further validated. In comparison, the linear regression and BO-XGBoost models show high accuracy towards the prediction of the outcome as indicated by its high R2 value equal to 0.883 and 0.880, respectively, while the R2 value for KNN is 0.736. Additionally, normalized feature importance was included in determining the input variables that significantly influenced compressive strength. The sensitivity of the model indicates CaO and SiO2 shows significant importance to predict ternary blended concrete compressive strength.

Utilizing nano-SiO2 for modifying the microstructure, strength and transport properties of sustainable cementitious materials with waste concrete powder

Using waste concrete powder as an alternative binder in green cementitious materials contributes to reduce the number of construction and demolition waste, and developing an effective method to modify the performance of waste concrete powder blended cementitious materials is necessary. The influences of nano-SiO2 at 0–3% dosage on cementitious materials containing waste concrete powder as partial cement replacement (0–50%), under a ratio of 1:2 for both water-to-binder and binder-to-sand, were investigated in this study with the aspects of micro-structure and macro-performance. The results illustrated that mixing waste concrete powder negatively impacted the hydration reaction and micro-structure of cement paste; however, the mix of nano-SiO2 promoted the secondary hydration reaction and refined pore diameter of waste concrete powder mixed paste. Mixing nano-SiO2 raised the drying shrinkage but reduced the water loss of paste including waste concrete powder. The replacement of cement by waste concrete powder caused the reduction in compressive strength of paste. But at a fixed substitution level of waste concrete powder in paste, the compressive strength rose with the increment of nano-SiO2 content up to 3%. The transport properties rose as waste concrete powder was incorporated in mortar, but the mix of nano-SiO2 significantly reduced the transport properties of waste concrete powder incorporated mortar. Particularly, the effects of nano-SiO2 addition on the decrease in water absorption became more distinct as high content of waste concrete powder was blended. Optimizing the content of waste concrete powder and nano-SiO2 can obtain green cementitious materials owning good strength and low transport properties.

Influence of calcined clay morphology on flow in blended cementitious systems

Retaining workability in blended cementitious systems containing calcined clays remains challenging. Here, the influence of calcined clay morphology on both fresh and hardened properties of blended cementitious materials is evaluated through flow and strength testing, comparing the performance of halloysite nanotubes, agglomerated halloysite spherical particles (obtained through spray drying), and conventional metakaolin sheets. In addition, calorimetry and quantification of portlandite content assess the influence of clay morphology on pozzolanic reactivity. All tests were performed at 10 % cement replacement by mass and benchmarked against ordinary portland cement (OPC) and OPC diluted with 10 % quartz. Calcined halloysite spheres were found to increase mortar flow by 30–75 %, produce a similar heat evolution profile, and moderately increase strength (up to 8 %) by 56 days, compared to 100 % OPC. This is achieved without a notable change in pozzolanic reactivity compared to halloysite nanotubes, beyond 7 days. Each of these performance metrics is equivalent to or an improvement over metakaolin sheets, demonstrating that the spherical morphology obtained through spray drying produces a calcined clay with advantages, particularly in workability.

Combined Effect of Ternary Blended Cementitious Materials in Self-compacting Concrete

Self Compacting Concrete (SCC) is a type of special concrete which possess self packing and flowability to fill the formwork space completely by its own weight without any external vibration or compaction. Research studies on finding efficient, economical and eco-friendly materials to replace the conventional concrete materials are increasing day-by-day. An important constituent material of concrete is cement which contributes to the environmental hazardous problem of CO2 emission. In this view, the present study investigated the fresh and hardened properties of SCC in which cement is partially replaced by multi-cementitious materials namely fly ash, alccofine and Recycled Concrete Powder (RCP). Fly ash and alccofine are evident materials to replace cement in concrete. In addition to the substitution of cement by 20% replacement by fly ash and 10% replacement by alccofine, recycled concrete powder collected from construction wastes are also incorporated (5%, 10%, 15%, 20%) and investigated. Water/binder ratio is kept constant as 0.45. Polycarboxylate based super plasticizer (Conplast SP430) was used. The experimental program comprises testing the fresh stability by determination of flowability, passing ability and viscosity, mechanical strength testing including compressive strength, split-tensile strength and flexural strength and durability properties such as water absorption, sorptivity and acid-attack of SCC specimens. The test results showed that 10% recycled concrete powder exhibited better performance in fresh stability and satisfied performance mechanical strength. Increase in RCP content beyond a limited proportion possesses detrimental effects on the durability characteristics.

Thermodynamic equilibria-based modelling of reactive chloride transport in blended cementitious materials

A physico-chemical modelling of multispecies transport through cementitious materials is proposed considering thermodynamic equilibria, diffusion and migration. The model considers seven species profiles (Cl−, Na+, K+, Ca2+, SO42−, Al(OH)4− and OH−) and the dissolution/precipitation rates during multispecies transport under an electrical field. The fluxes are calculated by the Nernst-Planck equation. Case studies were performed simulating the chloride migration test in the steady state and NT Build 492 test on cement pastes based on slag and/or Portland cement. In order to simulate real exposure to seawater, the migration tests were based on synthetic seawater in the upstream compartment and a synthetic pore solution in the downstream. Pore solution extractions and scanning electron microscopy were performed in order to provide input data and to monitor dissolution/precipitation reactions. The proposed modelling highlights a reduction of up to 10% of free chlorides in the material tested compared to the classic Nernst-Planck modelling.

A new mix design method for low-environmental-impact blended cementitious materials: Optimization of the physical characteristics of powders for better rheological and mechanical properties

The use of blended cements has attracted much interest in the quest to overcome the environmental challenges facing the concrete industry. However, partially replacing cement with supplementary cementitious materials (SCMs) can result in complex rheological behavior that is influenced by the type of SCM and the replacement percentage, as well as the physical characteristics of the particles. Adequate physical control of the blended cements is essential for improving the rheology of the suspensions. A new mix design methodology based on the physical optimization of SCMs is proposed and validated to ensure adequate rheology of the suspensions. The physical characteristics that influence the viscosity of the cement-based suspensions investigated in this study include particle-size distribution, surface roughness, maximum packing density of the powder, and interparticle distance. Based on the experimental results presented in this paper, ternary binders with optimized physical characteristics enhanced the 28-day compressive strength of mortar by 20% while decreasing the clinker content by 15% and maintaining constant fluidity.

Lattice Boltzmann modelling of ionic diffusivity in non-saturated limestone blended cement paste

The accurate prediction of ionic diffusivity in non-saturated limestone blended cement paste is essential for the durability design of blended cementitious materials. This paper presents an integrated framework for simulating the ionic diffusivity in limestone blended cement paste considering its 3D microstructure, water saturation level, and distribution of water and gas phases in the pore network. The 3D microstructure of hydrating blended cement paste with various limestone powder (LP) contents and water-to-binder (w/b) ratios was simulated using the voxel-based CEMHYD3D model, based on which a lattice Boltzmann model with in-house codes was employed to simulate the solid–fluid interaction and ionic diffusivity in cement paste. Results indicate that the relative ionic diffusivity in blended cement paste is strongly dependent on the water saturation level, the evolution of which consists of the sharp drop, slow decrease, slight decrease and depercolation periods. For blended cement paste with 10% LP and w/b ratio of 0.5 at 28 d, the change in decrease rate occurs at the critical water saturation levels of 69%, 34% and 7%, respectively. With the increase of w/b ratio and LP content, the relative ionic diffusivity decreases due to the increasing volume fraction and connectivity of capillary pores. However, the relative ionic diffusivity at degrees of saturation above 70% only undergoes a slight decrease from 0.24 to 0.17 with the increasing LP content from 0% to 20%, which can be ascribed to the low reactivity of LP that cannot much modify the pore structure.

Synergistic effect and mechanism of waste glass on the mechanical properties and autoclave stability of cementitious materials containing steel slag

Incorporating solid waste into cement and concrete products can save natural resources and reduce environmental problems caused by the disposal of industrial solid waste. In this study, steel slag powder and waste glass powder were synergistically used to replace cement. The blended cementitious materials showed good mechanical strength and autoclave stability with the synergistic aid of steel slag and waste glass. This study used an autoclave experiment to accelerate the hydration reaction. Results suggested that waste glass as an amorphous siliceous material enriched hydration products and completely consumed f-CaO in steel slag under autoclave for 3 h. The expansion rate of the blended paste was the lowest, and the stability was the best when the mass ratio of ordinary Portland cement: steel slag powder: waste glass powder was 7:2:1. A complete reaction of f-CaO occurred in the steel slag in the presence of an excess of waste glass powder in the blended cementitious materials. An excessive waste of glass powder can cause alkali–silicon reaction with Na+ and K+ ions and lead to expansion.

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.

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