Addition Of Metakaolin Research Articles

Microstructural and mechanical properties of high-strength geopolymer based on Martian soil simulant

Geopolymers made from simulated Martian regolith would suffer from exhibit poor engineering properties, rendering them unsuitable as base materials. To improve the mechanical properties of geopolymers, this study prepared a new Martian soil simulant named DH-1. DH-1- based geopolymers were synthesized using Al2O3 (Al group) and metakaolin (MK group) as modifying agents. The durability of geopolymers with ultraviolet (UV) radiation was assessed under simulated Martian atmospheric conditions. The results indicated that the UCS and FS of both the Al and MK groups increased with curing time, with maximum UCS and FS of 55.27 MPa and 15.16 MPa, respectively. The UCS and FS of the Al and MK groups exhibited a two-phase change. The inflection points for rapid to slow in the UCS and FS occurred on day 28 for the Al group and day 14 for the MK group. The addition of Al2O3 and metakaolin promoted the replacement of silicon atoms by aluminum atoms in the silica-oxygen group, producing more gels product. After UV irradiation, the UCS and FS of the geopolymer decreased by 13 % and 44 %, respectively. Furthermore, the geopolymers underwent carbonation, with new cracks forming due to the combined effects of UV exposure, causing strength reduction.

Assessing the impact of recycled concrete aggregates and metakaolin on the mechanical properties of pervious concrete

Population growth and urban expansion have increased impervious surfaces, leading to environmental issues such as stormwater runoff and groundwater depletion. Traditional concrete, while durable, contributes to these problems. There is a need for sustainable construction materials that can address environmental challenges and reduce the consumption of natural resources. Pervious concrete, enhanced with recycled aggregates (RCA) and supplementary cementitious materials (SCMs) like metakaolin (MK) present a potential solution. This study aims to improve the mechanical and durability properties of pervious concrete by incorporating RCA and MK, assessing their effects on workability, density, porosity, permeability, compressive strength and flexural strength. The incorporation of RCA resulted in increased aggregate porosity compared to natural aggregates. Workability was assessed using the slump test, density was measured, and porosity and permeability were evaluated. The results showed that incorporation of RCA generally decreased workability, density and strength, while the addition of MK improved these properties by refining the microstructure. Specifically, mixes with 10% MK demonstrated better performance in terms of increased compressive and flexural strengths, improved density and reduced porosity. The ANN model showed high accuracy in predicting compressive and flexural strengths. The study concludes that RCA and MK can enhance the mechanical and durability properties of pervious concrete.

Hybrid Effect of Metakaolin and Nano-Silica on Mechanical and Durability Parameters of Mortar

The incorporation of pozzolanic materials such as nano silica and metakaolin in cementitious materials has gained significant attention in recent years due to their potential to improve the mechanical and durability properties of cement-based composites. This thesis investigates the hybrid effect of nano silica and metakaolin on the mechanical and durability properties of cement mortar. The research work involved the preparation of cement mortar specimens with varying proportions of nano silica and metakaolin, which were then subjected to a series of mechanical and durability tests. The mechanical tests included compressive strength, while the durability tests included water absorption and elevated temperature test. The study showed that the addition of both nano silica and metakaolin to cement mortar resulted in a significant improvement in the mechanical properties of the mortar. Additionally, the hybrid effect of nano silica and metakaolin resulted in enhanced durability of the cement mortar, with a significant reduction in water absorption and improved temperature resistance. The findings of this study will have significant implications for the development of sustainable and durable cementitious materials. The use of pozzolanic materials such as nano silica and metakaolin can reduce the consumption of cement and the associated carbon footprint while also improving the durability and long-term performance of cement-based composites. Overall, this study suggests that the incorporation of nano silica and metakaolin can lead to significant improvements in the mechanical and durability properties of cement mortar, making it a promising material for use in various construction applications.

The Effects of Metakaolin on the Properties of Magnesium Sulphoaluminate Cement.

Magnesium sulphoaluminate (MSA) cement has good bonding properties and is suitable as an inorganic adhesive for repairing materials in civil engineering. However, there are still some problems with its use, such as its insufficient 1 day (d) strength and poor volumetric stability. This paper aims to investigate the influences of metakaolin (MK) on the physical and mechanical properties of magnesium sulphoaluminate (MSA) cement. The hydration products and microstructures of typical MSA cement samples were also analysed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). The results showed that the addition of metakaolin reduces the fluidity and shortens the setting time of the MSA cement. The initial setting time and final setting time shortened maximally by 15-27 min and 25-48 min, respectively, with the addition of 10-30% metakaolin. Moreover, the compressive strength and flexural strength of the MSA cement improved significantly with the addition of 10-30% metakaolin at a curing age of 1 d. Compared with the compressive and flexural strengths of the control sample at 1 d, the compressive strengths of the modified samples showed obvious increases of 98%, 101%, and 109%, and the flexural strengths increased by 39%, 31%, and 26%, respectively, although they decreased slightly when the curing ages were 7 d, 14 d, and 28 d. The addition of 10% metakaolin improved the water resistance of the MSA cement immersed in water for 7 d and resulted in even higher water resistance at 28 d. The addition of 10-30% metakaolin improved the volumetric stability of the MSA cement with increasing dosages before 28 d of ageing. XRD and SEM-EDS analyses showed that the metakaolin accelerated the early hydration reaction and optimised the phase composition of the MSA cement. The results indicate that the addition of 10-20% metakaolin improved the strength after 1 d of ageing, water resistance, and volumetric stability of the MSA cement, providing theoretical support for the application of MAS cement as an inorganic bonding agent for repairing materials.

Long-Term Performance of Mortars with Combined Incorporation of Ladle Furnace Slag and Metakaolin

Ladle furnace slag (LFS) is used as a supplementary cementitious material (SCM) due to its high calcium oxide (CaO) content. Its binding properties are enhanced in the presence of siliceous materials, such as metakaolin (MK), forming a ternary mixture that can directly replace ordinary Portland cement (OPC). However, despite this blend having already been evaluated in alkali-activated mixtures, knowledge about this mixture in situations of direct replacement of OPC by slag is still lacking. This study evaluates the synergistic effects of combining LFS and MK in cementitious mortars. Due to an insufficient hydration reaction observed in the short term, this study focuses on assessing the long-term performance of these mortars. Both the fresh and hardened states at 28 and 180 days are evaluated, and the resulting microstructural characteristics and constituent phases are also examined. After 180 days of curing, the mortar with MK exhibits superior binding activity compared to the results at 28 days. Although the nominal resistance does not show a clear advantage with the application of MK, a significant reduction in the porosity of the mortar is observed. Microstructural analysis indicates that the addition of MK increases the hydration compounds when mixed with LFS. Importantly, the sample containing MK and LFS showed a 42% reduction in cement consumption, highlighting the potential for resource efficiency. Thus, this study contributes to promoting a circular economy between the steelmaking and civil construction sectors.

A study on the mechanical performance, shrinkage and morphology of high-performance fiber reinforced concrete with varying SCMs and geometry of steel fibers

This paper investigates the effects of silica fume (SF) and metakaolin (MK) as cement substitutes on the mechanical properties, shrinkage, and toughness performances of steel fiber reinforced concrete (SFRC). Initially, a reference concrete mix with a water-to-binder ratio of 0.4 is blended with different volume fractions of steel fibers with varying geometries (crimped steel and straight steel), both individually and in combination, to examine their mechanical properties. Also, the possible influence of pozzolans on the variation of drying shrinkage and flexural toughness of hybrid steel fiber reinforced concrete (Hy-SFRC) was evaluated. An increase in workability was observed as a result of hybridization of steel fibers. Pozzolanic steel fiber reinforced concrete (SFRC) exhibited a more significant enhancement in compressive strength and flexural strength compared to non-pozzolanic SFRC. The hybrid combination of CS 1.5 % and SS 0.5 % was found to be the best in terms of mechanical properties. The addition of SF and MK reduced the shrinkage strain by up to 50 % compared to the reference mix. The flexural toughness values for both binary and ternary pozzolanic Hy-SFRC were notably higher than those for non-pozzolanic Hy-SFRC, indicating a stronger bond between the fibers and the matrix. Hy-SFRC containing a ternary pozzolanic mix of SF 10 % and MK 10 % gave the best results in flexural toughness. The results were consistent with morphology analysis, which revealed an increase in hydration products at the interface between the aggregate and concrete matrix, as well as between the steel fiber and concrete matrix, due to the ternary blending of SF and MK.

Influence of Nano-Activated CaCO3-Metakaolin on Early Strength and Microstructure of Cement

The early strength, microstructure, and structure of cement mortar under low-temperature curing conditions were investigated through compressive strength tests, scanning electron microscopy, x-ray diffraction, synchronous thermal analysis (thermogravimetric analysis coupled with differential scanning calorimetry), and nuclear magnetic resonance tests. The study focused on the impact of the single addition of nano-activated CaCO3 (NAC) and the simultaneous addition of metakaolin (MK) on cement mortar. The results indicate that the addition of NAC accelerated the early hydration of cement. At a 1% dosage, the compressive strength increased by 6.84%, 14.77%, and 18.58% at 1 day, 3 days, and 7 days, respectively. When 5% MK was co-added, the compressive strength increased by 15.16%, 27.85%, and 21.66% at 1 day, 3 days, and 7 days, respectively. The combination of NAC and MK accelerated the hydration of cement, refined the products, reduced the porosity, improved the microstructure, and enhanced the early compressive strength of cement-based materials.

Synergizing metakaolin and waste-glass for sustainable and functional UHPCC– a central composite design and ecological footprint assessment

Optimizing ultra-high-performance cementitious composites (UHPCC) with sustainable materials often compromises certain properties due to the chemical nature of alternative binders used to replace standard UHPCC components like Portland cement (OPC) and microsilica (MS). In the context of Waste-Glass-UHPCC, the reduction in early strength, attributed to the varied pozzolanic reactivity of MS and recycled glass powder as cementitious materials, may reduce its application that requires high early strength. This study addresses the early strength deficiency of Waste-Glass-UHPCC by incorporating metakaolin (MK) and also aims to assess the impact of MK on 28-day compressive strength, durability, and carbon footprint. Research investigating the effects of MK on UHPCC with reduced OPC and MS content is currently limited. Specifically, this investigation explores the influence of MK on UHPCC characterized by a cement content of 620 kg/m3. By utilizing advanced statistical methods [i.e., the Central Composite Design (CCD) and Response Surface Methodology (RSM)], this study investigates the substitution of MK for OPC in formulations of Waste-Glass-UHPCC. The experimental design comprises 18 encoded mixtures, allowing for the development of second-order regression models for critical responses [slump flow and compressive strength at different ages]. Besides, visualization through RSM-3D graphs facilitates a comprehensive examination of the effects of various factors. For a deeper analysis, two of the CCD's points, i.e., SP-12 (Waste-Glass-UHPCC without metakaolin), and SP-10 (Waste-Glass-UHPCC with 65.77 kg of metakaolin per cubic meter) were further investigated along with a control dosage that represents a typical UHPCC formulation. The responses studied encompassed 1, 7, and 28 d compressive strength, chloride ion penetration, and carbon footprint measured by a systematic life cycle analysis (following ISO 15804), assessing the environmental impact of the UHPCC's making materials from raw extraction to disposal. Despite encountering challenges in meeting self-compacting concrete criteria due to MK's tendency to accelerate hydration, the enhanced early strength properties (61 % higher than those of the Waste-Glass-UHPCC) make the MK-based mixture appropriate for various applications such as bridge engineering or pavement rehabilitation. Additionally, the addition of MK in UHPCC formulation demonstrated superior resistance to chloride ion permeability even compared to the control mixture, attributed to MK's ability to enhance the concrete's microstructure and capture chloride ions, attributed to Friedel's salt formation. Noteworthy findings include a significant (27 %) reduction in carbon footprint with the incorporation of MK in Waste-Glass-UHPCC compared to the control counterparts. The current study highlights the durability and environmental advantages of MK-based UHPCC blends while emphasizing the critical requirements of workability and strength development of sustainable UHPCC.

Enhancing Hydraulic Lime Mortar with Metakaolin: A Study on Improving Restoration Materials for Historic Buildings.

This study investigates the enhancement of hydraulic lime mortar (HLM) using varying contents of metakaolin (MK) to improve its application in the restoration of historic buildings. Samples from historic structures were analyzed, and the effects of different MK contents on the physical and mechanical properties of HLM were examined. The reaction mechanism and microstructural changes were evaluated using XRD and SEM analysis. The results indicated that increasing MK levels in HLM led to a decrease in fluidity, with fluidity reducing by 4.8% at 12% MK. The addition of MK increased water consumption for standard consistency by 5.4% and shortened the final setting time by 10.2%. MK consumption promoted secondary hydration, enhancing compressive strength by up to 98.1% and flexural strength by up to 55.1%, and increasing bonding strength by 26.9%. The density of HLM improved with MK addition, slightly reducing moisture content by 4.5% and water absorption by 4.6%, while the water vapor transmission properties decreased by 50.9%, indicating reduced porosity. The elastic modulus of the mortar increased significantly from 2.19 GPa to 7.88 GPa with the addition of MK, enhancing rigidity and crack resistance. The optimal blend for restoration materials was found to be 9.0% MK and 25.0% heavy calcium carbonate and was characterized by moderate mechanical strength, enhanced early strength, commendable permeability, minimal risk of cracking, and ease of application. This blend is highly suitable for the rehabilitation of historic structures.

Enhancing the Properties of Steel Fiber Self-Compacting NaOH-Based Geopolymer Concrete with the Addition of Metakaolin

There is a demand for innovative construction materials that offer enhanced mechanical characteristics while also being cost-effective and environmentally friendly. This paper examines the fresh properties and mechanical properties of geopolymerized self-compacting concrete (SCC) reinforced with steel fibers, containing 0–100% metakaolin (MK) by mass, as an eco-friendly substitute for Portland cement. SCC combinations included one or more waste cementitious materials (WCMs), such as metakaolin (MK), NaOH as an alkaline activity, and double-hook end steel fibers. For every NaOH geopolymer SCC blend, the mechanical characteristics (compressive strength, splitting tensile strength, flexural strength), as well as the new properties (lump flow, V-Funnel, L-box test), were read up. The findings indicate that combining metakaolin and steel fibers reduces the flowability of NaOH-based geopolymer SCC. On the other hand, incorporating MK and steel fibers enhances the compressive and flexural strength of NaOH-based geopolymer SCC with 25% metakaolin and 0.3% steel fiber. In contrast to the fiber-reinforced NaOH-based geopolymer SCC samples, which could transfer a sizable load even when the crack mouth opening deflection rose at flexural strength, the fiber-free SCC samples showed a brittle and abrupt fracture. The findings showed that the addition of NaOH as an alkaline activator, MK, and steel fiber had a negative impact on the fresh state properties; however, their combined use greatly enhanced the bond strength and flexural performance of the NaOH geopolymer SCC specimens. Doi: 10.28991/CEJ-2024-010-07-011 Full Text: PDF

Effect of styrene acrylic latex on the performance of metakaolin blended cement: From hydration to mechanical properties

Effects of styrene acrylic (SA) latex on the hydration and mechanical properties of metakaolin blended cement (MKC) were systematically evaluated through the combined techniques of calorimetry, flow table test, Vicat test, mechanical measurement, QXRD, TGA and SEM. The results show that the presence of metakaolin (MK) greatly changes the interaction of SA polymer with cement grains and then modifies the properties of cement paste and mortar. Specifically, the retardation effect of SA latex on cement hydration can be alleviated through the addition of MK due to its strong adsorption ability to polymer particles, which is beneficial to shorten the setting time of cement paste. The addition of SA latex not only retards the hydration process of cement but also the pozzolanic reaction of MK with portlandite. Contrary to the adverse effect of SA latex on compressive strength, improved strength of hardened MKC mortar was observed with the increased polymer dosage from 4 % to 8 %, which is believed to be caused by the modified microstructure of the matrix through the film formation of SA polymer.

Mechanical properties of polymer fibre reinforced concrete in the light of various standards

The article presents the results of a detailed experimental campaign including a compressive strength test, three- and four-point bending test (3PBT and 4PBT, respectively) of polymer fiber reinforced concrete with the addition of metakaolin. The comprehensive analysis included three Types of concrete mixture differing in amount and used polymer fibers. It was concluded that polymer fibers did not influence the maximum compressive and flexural tensile strength of concrete. On the other hand, they had a beneficial effect on the ductility, residual and equivalent flexural tensile strengths, and fracture energy of samples. The mixtures of Type 1 and 2 were characterized by softening behaviour but the mixture of Type 3 by soft-hardening behaviour. In the 3PBT, the residual flexural tensile strengths obtained according to EN 14651 did not correspond clearly with equivalent flexural tensile strengths calculated in compliance with RILEM TC 162-TDF. It is noteworthy that the effectiveness and correctness of equations presented in other work of the authors referring to dependencies between deflection, crack and tip mouth opening displacements for the 3PBT were confirmed on samples with different composition and fibers. Based on the 4PBT, the equivalent flexural tensile strengths according to JCI-SF4 standard were calculated and the correlations with the results from 3PBT were defined.

The Effects of Hydroxypropyl Methyl Cellulose and Metakaolin on the Properties of Self-Compacting Solidified Soil Based on Abandoned Slurry.

As a new type of backfill material, Self-compacting solidified soil (SCSS) takes the abandoned slurry of cast-in-place piles after dewatering and reduction as the main raw material, which brings a problem of coordinating the working performance with the mechanical property under the condition of high mobility. In this paper, hydroxypropyl methyl cellulose (HPMC) and metakaolin were introduced as additives to solve this problem. First, the workability and mechanical properties of SCSS were regulated and optimized by means of the water seepage rate test, the flowability test, and the unconfined compressive strength test. Second, this study also used X-ray diffraction (XRD) and scanning electron microscopy (SEM) to investigate the effects of HPMC and metakaolin on the physical phase and microstructure of SCSS. In this way, the results showed that there was a significant impact on the flowability of SCSS, that is, when the dosage reached 0.3%, the water seepage rate of SCSS was reduced to less than 1%, and the compressive strength at 7 days reached its peak. At the same time, HPMC weakened the strength growth of SCSS in the age period of 7 days to 14 days. However, the addition of metakaolin promoted its compressive strength. XRD analysis showed that the additives had no significant effects on the physical phases. And, from the SEM results, it can be seen that although the water-retaining effect of HPMC makes hydration of cement more exhaustive, more ettringite (AFt) can be observed in the microstructure. In addition, it can be observed that the addition of metakaolin can generate more hydrated calcium silicate (C-S-H) due to the strong surface energy possessed by metakaolin. As a result of the above factors, SCSS filled the voids between particles and improved the interface structure between particles, thus enhanced the compressive strength.

The preparation, property and hydration mechanism of ultra high performance concrete with metakaolin substitution for silica fume

In recent years, there has been a growing body of research on the use of metakaolin (MK) in Ultra-High Performance Concrete (UHPC) to address the issue of unstable production yields and quality of industrial by-product Silica fume (SF). However, the current scientific literature tends to focus primarily on performance enhancements, often neglecting to elucidate the underlying mechanisms responsible for these improvements. In this study, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), nuclear magnetic resonance (NMR), nanoindentation technology, and Mercury Intrusion Porosimeter (MIP) were employed to establish the correlation between mechanical properties and hydration products, microstructure, and micromechanical properties. The results indicate that the judicious addition of MK can enhance the Al/Si ratio, prolong the C-A-S-H chain length, thereby increasing the percentage of high-density C-A-S-H, reducing the volume of C-A-S-H gel pores, optimizing UHPC pore structure, and ultimately leading to improved mechanical properties.

Enhancing sustainability in self-compacting concrete by optimizing blended supplementary cementitious materials

Within concrete engineering, the uptake of self-compacting concrete (SCC) represents a notable trend, delivering improved workability and placement efficiency. However, challenges persist, notably in achieving optimal performance while mitigating environmental impacts, particularly in cement consumption. However, simply reducing the cement content in the mix design can directly compromise the structural-concrete requirements. Towards these challenges, global trends emphasize the utilization of appropriate waste materials in blended concrete. This study explored a promising strategy by integrating supplementary cementitious materials (SCMs) to contribute to the United Nations' Sustainable Development Goals (SDGs) in addition to the engineering contributions. It suggests an optimal combination of Metakaolin (MK) and Limestone Powder (LP) to partially substitute cement. The research methodology employs the response surface method (RSM) to systematically explore the ideal ingredient ratios. Through a comprehensive analysis of orthogonal array of 16 mixes, encompassing both mixture and process variables, this study aims to explain the effects of MK and LP addition on the rheological and mechanical properties of SCC with varying cement replacement levels. In terms of mixture constituents, the total composition of cement, MK, and LP was fixed at 100%, while coarse aggregate (CA), fine aggregate (FA), and the water-to-binder ratio were held as process variables. In order to assess the rheological properties of the mix-design, various tests including slump flow, L-box, and sieve segregation were conducted. Additionally, to evaluate mechanical strength, samples were tested for compressive strength at both 7 and 28 days. Findings from the experiments reveal higher concentrations of MK result in reduced workability and hardened properties. Through RSM-based designed experimentation covering both rheological and mechanical aspects, it is observed that the optimal cement replacement level lies between 40 and 55%. The findings of this study contribute to the advancement of sustainable and structurally robust concrete practices, offering insights into the optimal utilization of SCMs to meet both engineering requirements and environmental sustainability goals.

Improvement of the mechanical properties of concrete by the addition of Metakaolin and rice husk hydrolyzed using a new method

Improvement of the mechanical properties of concrete by the addition of Metakaolin and rice husk hydrolyzed using a new method

Development of sustainable interlocking concrete paving blocks using bamboo leaf ash and metakaolin

Eco-friendly interlocking concrete pavement block was developed using the admixture of bamboo leaf ash and metakaolin. This was done to develop an eco-friendly interlocking paving block for sustainable pavement construction. Bamboo leaf ash and metakaolin were added as a supplementary cementitious material. The supplementary cementitious material (bamboo leaf ash and metakaolin) were admixed and added at 0, 5, 10, 15, 20, 25 and 30 % replacement of cement. The workability of the fresh concrete (slump) at the varied percentage additions, and the mechanical properties of the concrete at 7, 14, 28, and 56 days of curing were assessed, including their microstructural characteristics. The outcome of the research showed that increasing the percentage of (bamboo leaf ash + metakaolin) reduces the workability of the concrete. With a 20 % addition of this cementitious material, the developed fresh concrete became unworkable. In addition, replacing up to 10 % of the concrete in the pavement with bamboo leaf ash and metakaolin increased the mechanical strength of the concrete by 28.7 %. At 30 % a percentage increase of 3.6 % was recorded. However, the strength at 5 % was still adequate for pavement construction with a 13.62 % increase in mechanical strength. The compressive strength at 5 % and 10 % addition of the supplementary cementitious material at maturity met the criteria for constructing a semi-rigid pavement, using IRC standards. The microstructural assessment showed that the number of pores in the mature concrete samples decreased at 10 % addition of bamboo leaf ash and metakaolin. The research data provides construction workers, researchers, and highway engineers with vital information regarding the viability of these sustainable materials for pavement improvement.

Effects of metakaolin and zeolite on the dispersion properties and shear strength of dispersive clay soil

ABSTRACT The current study used metakaolin and zeolite either separately or in combination at 0%, 2%, 4%, 6% and 8% of the soil weight to improve dispersive clay soil at optimal humidity levels. The samples were tested to determine the extent of change in the dispersion potential, as well as improvements in the shear strength of dispersive clay soil. The dispersive soil was obtained near the city of Ardakan in Iran and the extent of change in its soil dispersion potential was evaluated after 7 days of curing. The results of the pinhole test indicated that the addition of 2% zeolite plus 8% metakaolin to the soil considerably decreased the dispersion potential. Uniaxial testing after 7, 14 and 28 days of curing revealed that the UCS of the samples increased. The greatest increase was observed in samples containing 2% zeolite and 8% metakaolin after 28 days of curing. The direct shear test was carried out after 7, 14 and 28 days of curing on the unmodified soil and soil modified with optimal percentages of metakaolin and zeolite. The combined addition of zeolite and metakaolin was found to increase the shear strength parameters of the samples.

Physical, mechanical properties and microstructure of waste GBFS-based geopolymer incorporated with metakaolin and SiC whiskers(SiCw)

Geopolymer, known as alternative materials to ordinary Portland cement, possess superior properties. This study employed varying dosages of metakaolin from 0 to 30 % and silicon carbide whiskers (SiCw) from 0 to 0.05 % to enhance GBFS-based geopolymer matrix. The process began with the dispersion of SiCw in an alkaline activator through magnetic and ultrasonic stirring, followed by the preparation of the geopolymer. Physical and mechanical characteristics were evaluated to reveal the improvement effects of metakaolin and silicon carbide whiskers on the geopolymer. Techniques such as FTIR, XRD, and SEM-EDS were utilized to analyze the morphology, chemical components, and mineral phases. Pore size distribution and microstructural rearrangement were assessed using MIP and 29Si NMR. Additionally, TG-DTG analysis was conducted to analyze thermal stability. The results indicated that optimal additions of metakaolin and SiCw increased interactions among gel products and induced more chemical reactions, thus exhibiting better mechanical strength and thermal properties. The water absorption and permeable porosity were also improved. The inclusion of SiCw notably provided more nucleation sites and increased the dissolved aluminum content, enriching the phase in the system.

Effect of calcium stearate on cellulose acetate-based mortars

The purpose of this study is to investigate the properties of cellulose acetate-based mortars with the addition of calcium stearate (CS), superplasticizer (SP) and metakaolin (MK). Previous research has shown that cellulose acetate (CA) fibers from industrial cigarette butts (CB) treatment can be incorporated into standard mortars at a rate of 1.3 wt%. CS was added in various proportions by weight (0.5, 1, 1.5 wt%), and their influence on cement hydration and microstructure was studied using various investigative techniques. The addition of CS was found to be beneficial in reducing the amount of water absorbed by CA, despite the significant absorption of these fibers. Furthermore, a CS rate of 1 wt% decreased CA-based mortar shrinkage. Additionally, 1 wt% CS improved by 18% the compressive strength of CA-based mortars manufactured with SP compared to the reference CA-mortar. CA fibers and CS seem to modify mortar microstructure by creating a plurimodal pore size distribution and reducing capillary pores. The CS addition, however, resulted in more cracks and reduced workability due to the weakening of the bond between the cement paste components. MK-mortars showed a slight 15% reduction in compressive strength and 13% reduction in bending strength; along with a 20% increase in shrinkage. By incorporating CA fibers as an additive along with CS or MK, CA-based mortars can improve some properties, including shrinkage and mechanical strength. Further, this approach offers a potential solution to CB pollution by reducing the environmental impact of this waste.