Fly Ash Cenospheres Research Articles

Matrix design and performance development of eco-friendly high-strength, lightweight engineered cementitious composites

This study develops a novel eco-friendly high-strength, lightweight engineered cementitious composite (EHLECC) using lightweight sand fines (LSF) and fly ash cenospheres (FAC) based on the theory of micromechanics, dense packing theory and method of performance driven design. The mechanical properties, microstructures, and micromechanism of EHLECC are examined. The results indicate that the accumulation compactness between different particles in EHLECCs is optimized due to the appropriate particle size range brought by LSF and FAC. LSF and FAC slightly reduced the mechanical strength of EHLECC matrix but had a significant weight reduction effect for EHLECC. All EHLECCs exhibited remarkable mechanical properties with the tensile strain exceeding 6%, tensile stress more than 10 MPa, and compressive strength surpassing 80 MPa. Moreover, the incorporation of LSF enhanced the degree of saturated cracking behavior in EHLECC, resulting in better ductility. Furthermore, LSF substitution rate of 75% led to the optimum matrix design. This study provides a new approach for designing and producing an EHLECC, which would be a promising building material for load-bearing structures and construction reinforcement.

Performance evaluation on bond, durability, micro-structure, cost effectiveness and environmental impacts of fly ash cenosphere based structural lightweight concrete

The production of huge fly ash waste from thermal power plants and gradual depletion of natural aggregates due to their high consumption in concrete making are two major threats to the sustainability of the environment. The strategic utilization of this waste as a replacement of natural aggregate in production of concrete can solve both the problems simultaneously. Hence, this study aims to evaluate the performance of structural lightweight concrete (LWC) containing fly ash cenosphere (FAC), a by-product of fly ash, in order to check its suitability for construction. In this study, one control concrete mix, i.e., without FAC, and other ten concrete mixes utilizing FAC as the replacement of natural fine aggregate (NFA) at the increment of 20% and with/without superplasticizer (SP) are prepared. The Mechanical properties (compressive and bond strength), durability aspects (sulphuric acid, magnesium sulphate and sodium chloride resistance) and the microstructural characteristics from X-ray diffraction and scanning electron microscope analyses of these mixes are evaluated. Moreover, the environmental impact assessment and cost-effective analysis are also conducted. From this investigation, it is found that the structural LWC can be produced by utilizing high volume FAC with/without SP with the acceptable mechanical and durability performances. Further, the concrete with 80% FAC and SP is found to be optimum having compressive strength of 32.59 MPa, which satisfies M25 grade concrete as per IS 456 (2000), meets ACI 213 (2014) requirements of structural LWC and has also acceptable durability properties. The microstructure studies have also supported the strength and durability results of these mixes. Moreover, these mixes are found to be cost effective and environmentally friendly. Hence, structural LWC prepared with a high volume of FAC and SP can be recommended for construction, which reduces the cost and environmental impacts significantly and preserves natural resources for the future generations.

Development of functional polyurethane-cenosphere hybrid composite coatings from ricinus communis seed oil

The usage of castor seed oil (CSO) as a sustainable and non-toxic biodegradable substitute for non-eco-friendly petroleum-based chemicals must be considered. This renewable feedstock (seed oil) is vital for developing polymeric organic coatings. This report investigates the one-spot synthesis of castor seed oil, 1,1,1-Tris(hydroxymethyl) propane (cross-linker), Isophorone diisocyanate, and cenosphere nanoparticles incorporated within the polymer matrix. The hybrid coatings were characterised using FT-IR, NMR, FESEM, and XRD. The FT-IR spectrum showing the presence of absorption peaks at 1350 cm-1, 1102 cm-1, and 1000 cm-1, which represent the (Al=O), (SiO-Si), and (AlO4) functional groups, respectively confirms the modifications carried out on the cenosphere fly ash nanoparticles. The thermal stability of the synthesised composites was evaluated on a thermogravimetric analyser (TGA). The TGA thermograms showed improved thermal stability as the percentage composition of CFA material increased in the coating system. The antimicrobial activity indicates that the PU-CFA composite bettered resistance toward Staphylococcus aureus and Escherichia coli.

The Synergic Effects of Nano Additives on the Mechanical Properties of Green Lightweight Concrete

Concrete materials have been commonly used in building and construction industries. However, the process of cement manufacture has long been connected with high consumption of energy and adverse environmental impacts. In this study, in order to produce innovative green concrete material that consumes lower energy, resources and is more eco-friendly, industrial waste by-product fly ash cenosphere has been utilized as lightweight aggregate to replace cement by 73.3 %. In most conducted researches regarding lightweight concrete (LWC) with cenospheres, attempts have been made to improve its physicomechanical properties by the inclusion of fibre materials, while limited studies have been performed to investigate the effects of nano additives, especially the synergic influence of them. Therefore, carbon nanotubes (CNTs) with the dosage of 0.05 %, 0.15 %, 0.45 % and nano silica (NS) with the content of 0.2 %, 0.6 %, 1.0 % by cement weight were used in this study as reinforcing fillers on the LWC. Experiments including flexural strength test, compressive strength test, water absorption and thermogravimetric analysis were carried out to evaluate the mechanical behaviors and the hydration characteristics of the produced LWC. Based on the experimental outcomes, the incorporation of CNTs and NS can effectively enhance both the flexural and compressive strength and reduce the absorbed water weight. The results from the thermogravimetric analysis reveal that the binary presence of CNTs and NS exerts positive impacts on the cement hydration reaction.

Synergic Effects of Nano Additives on Mechanical Performance and Microstructure of Lightweight Cement Mortar

Owing to their convenient manufacture, transportation, low energy consumption, and environmental impacts, lightweight cement composites have been applied as building and construction materials. However, its decreased density is associated with a reduction in mechanical strength. In most existing investigations, attempts have been made to improve mechanical behaviours via supplementary cementitious or fibre materials, whereas limited studies have been implemented on the effects of nano additives, especially their synergic influence. In this study, industrial waste fly ash cenosphere (FAC) has been utilized as lightweight aggregate by 73.3% cement weight to fabricate sustainable lightweight cement mortar (LWCM). Carbon nanotubes (CNTs) at a dosage of 0.05%, 0.15%, and 0.45% and nano silica (NS) with the content of 0.2%, 0.6%, and 1.0% by cement weight have been applied as modifying additives. Experiments were carried out to test flexural strength, compressive strength, and water absorption. SEM, TG, and XRD analyses were conducted to evaluate microstructure and hydration characteristics. Based on the outcomes, the inclusion of CNTs and NS can effectively increase flexural and compressive strength and reduce absorbed water weight. The analysis of SEM, TG, and XRD reveals that the binary usage of CNTs and NS can improve pore structure and facilitate hydration reaction.

Development and characteristics of multifunctional ultra-lightweight engineered cementitious composites incorporating cenospheres and PE fibre

Ultra-lightweight, high ductility, high strength, and multi-functionality are recent development trends in concrete. This study proposed a design concept of multifunctional ultra-lightweight engineered cementitious composites (ULW-ECCs) without functional fillers using fly ash cenosphere (FAC) and polyethylene (PE) fibre, which has heat insulation, self-sensing, and self-healing functions. The mechanical (tension, compression, flexure) and corresponding self-sensing properties under monotonic and cyclic loading, self-healing, thermal conductivity, and thermal effusivity properties were examined. The ULW-ECCs were developed based on the maximum packing density of the matrix, which showed high pseudo-strain-hardening indices and had an apparent density of 1055–1333 (Oven-dry density: 946–1261) kg/m3, compressive strength of 36–58 MPa, and a tensile strain capacity of 4%–8% under standard curing condition. With the use of FAC with a highly stiff shell, the ULW-ECCs show high strength and high thermal insulation properties. ULW-ECCs incorporating FAC show excellent self-sensing properties without any conductive fillers under compression, bending and tension. The electromechanical behaviour was consistent and repeatable during cyclic and monotonic loading processes, and a microstructure model was used to explain the self-sensing mechanism. The cement paste in the matrix can form a 3D-like honeycomb structure because a large number of FACs evenly divide the cement paste, which shows sensitive self-sensing ability. Additionally, the multiple micro-cracks of ULW-ECCs show excellent self-healing properties. Optical microscope and SEM analyses of ULW-ECC were used to explain the results. The developed multifunctional ULW-ECCs without functional fillers would be a promising material for sustainable development.

Marine oil spill remediation by Candelilla wax modified coal fly ash cenospheres

Biodegradable candelilla wax (CW) was creatively used for hydrophobic modification of coal fly ash cenospheres (FACs), a waste product from thermal power plants, and a new spherical hollow particulate adsorbent with fast oil adsorption rate and easy agglomeration was prepared. CW was confirmed to physically coat FACs and the optimum mass of wax added to 3 g of FACs was 0.05 g. From a series of batch scale experiments, CW-FACs were found to adsorb oil, reaching adsorption efficiency of 80.6% within 10 s, and aggregate into floating clumps which were easily removed from the water's surface. The oil adsorption efficiency was highly dependent on hydrophobicity of the used adsorbent, the adsorption of Venezuela oil onto CW-FACs was found to be a homogenous monolayer, and the capacity and intensity of the adsorption decreased as temperature increased from 10 to 40 °C. The Langmuir isotherm model was the best fit, with the maximum adsorption capacity achieved at 649.38 mg/g. CW-FACs were also found to be highly stable in concentrated acid, alkaline and salt solutions, as well as for spills of different oil products. Furthermore, the retention rate of the oil adsorption capacity of the CW-FACs after 6 cycles of adsorption-extraction was as high as 93.2%. Therefore, CW-FACs can be widely used, easily recycled, and reused for marine oil spill remediation, which is also a good alternative disposal solution for FACs.

Strength of light weight concrete containing fly ash cenosphere

The study's main focus is on finding a modern substitute for grit in light-weight concrete (LWC). The researcher is concentrating on partly replacing sand with readily available solid wastes like cenospheres, which are likely to support waste management and also provide a potential replacement for the most exploited. Three different series of mortar cubes with three identical specimens each were used in the experimental research. The observed outcomes have demonstrated the better compatibility of using fly ash up to 25% and cenospheres at 30% as a sand replacement in LWC with improved strength characteristics. In the construction of concrete structures, Light Weight Concrete (LWC) is quickly gaining acceptance for a variety of uses. When building concrete structures, Light Weight Concrete (LWC) is quickly becoming satisfactory for a variety of uses. Fly ash and cenospheres are added to concrete to improve its workability, strength, and longevity. They serve as pozzolanic components. In order to determine the best replacement for mineral admixtures like fly ash and bagasse ash in concrete, various ages of the materials were used to examine the strength characteristics such as cube compressive strength, cylinder compressive strength, and split tensile strength. The ideal replacement amount of fly ash and cenosphere was determined after comparing the strengths. According to the effects of the various fly ash and cenosphere fractions used to substitute the sand, the mechanical properties change to utilise cenosphere and fly ash.

Synthesis and Sorption Properties of Microsphere Zeolite Materials Based on Coal Fly Ash Cenospheres with Respect to Cs+ and Sr2+

Synthesis and Sorption Properties of Microsphere Zeolite Materials Based on Coal Fly Ash Cenospheres with Respect to Cs+ and Sr2+

Effect of Filler Materials on Abrasive Wear Performance of Glass/Epoxy Composites

When creating polymer-based composites, plain weave fabrics and micron-sized fillers offer bidirectional strength and reduced voids/inhomogeneity. In the present work, It was investigated how glass fabric reinforced epoxy composite (G-E) performed during three-body abrasive wear with and without ceramic fillers (SiO2, Al2O3, graphite, and fly ash cenospheres). In experiments, loads of 20 N and 40 N were applied at various abrading distances of 500 m, 1000 m, 1500 m, and 2000 m. According to the results of sand abrasive wear test, the specific wear rates of G-E based composites are sensitive to fibre and filler/matrix adhesion. Under all tribo-test settings, the SWR for all particulate G-E composites decreases in the following order: G-E > Gr/G-E > SiO2/G-E > Al2O3/G-E > fly ash cenosphere/G-E. Furthermore, the specific wear rate of the fly ash cenosphere filled G-E composites were found to be lower than the G-E and other filler materials filled G-E composites. There was 38.7% reduction in the specific wear rate at 40 N, 2000 m in fly ash cenosphere filled G-E composite. As per the evidence of scanning electron microscope images of worn-out surfaces, mechanisms such as ploughing, fibre breakage, fibre pull-out, fibre thinning, and a network of microcracks caused the wear in composites.

Synthesis of NiO coated chitosan-cenosphere buoyant composite for enhanced adsorptive removal of methylene blue

The objective of the present study is to utilize fly ash cenosphere to remove methylene blue (MB) from the water streams. Nickel oxide is a typical semiconductor used as proficient adsorbent material for degradation of dye with environment friendly applications due to its excellent chemical stability and high catalytic activity. The chitosan cenosphere buoyant composite coated with NiO was synthesized with hydrothermal grafting reaction using silane coupling agent and epichlorohydrin as a cross-linking reagent. The batch adsorption experiments were carried out with a cationic dye, methylene blue as a representative organic pollutant to investigate the adsorptive capabilities of the composite as adsorbent. The influence of pH (2-12), initial concentration of dye (50–200 mg/L), temperature (37–47 °C) and contact time (0–24 h) were taken as parameters in the study. On the relative elimination of MB, the effect of time and temperature were investigated. The adsorption kinetics for MB was correlated and found to observe the pseudo-second order kinetic model, whereas the equilibrium adsorption isotherm follows the Langmuir model (R2 > 0.99). The results indicate that the floating fly ash cenosphere coated with NiO proved to be more responsive for enhanced degradation of methylene blue.

Performance and application study of silane coupling agent (KH550) modified wood fiber‐fly ash cenosphere/epoxy resin composites

AbstractIn this paper, the epoxy resin composite filled with wood fiber and fly ash cenosphere was prepared. In order to improve the bonding properties between wooden fiber/fly ash cenosphere and epoxy resin, the grafting treatment of wooden fiber and fly ash cenosphere surfaces was carried out here using KH550 type silane coupling agent. The effects of different process parameters on the surface modification effect of wooden fiber and fly ash cenosphere were investigated, the mechanical properties and energy absorption characteristics of the materials before and after the filler modification were tested, and the microscopic interfacial structures of the matrix with wooden fiber and fly ash cenosphere were investigated by scanning electron microscopy. Meanwhile, based on LS‐DYNA simulation software, the energy‐absorbing performance of energy‐absorbing boxes prepared from AA6061 aluminum alloy and modified wooden fiber‐fly ash cenosphere/epoxy resin composites were compared in low‐velocity collisions.

Synthesis and Sorption Properties of Microsphere Zeolite Materials Based on Coal Fly Ash Cenospheres with Respect to Cs+ and Sr2+

The effect of the hydrothermal synthesis conditions (temperature, duration, mixing), composition, and presynthetic processing of narrow fractions of cenospheres of fly ash, which act as a template and source of Si and Al, on the production of microspherical zeolite materials of the given structural type in the Na2O–H2O–(SiO2–Al2O3)glass of two molar compositions is studied. The synthesis products are characterized by XRD, SEM-EDS, and low-temperature nitrogen adsorption, and their sorption properties in relation to Cs+ and Sr2+ are studied. The factors contributing to the predominant formation of NaX zeolite of the faujasite structural type are revealed. It is established that zeolite products based on cenospheres with a glass phase content of about 95 wt % demonstrate the highest sorption parameters, including the maximum capacity for Cs+ and Sr2+ of up to 250 and 180 mg/g, distribution coefficient of about 104 and 106 mL/g, and degree of extraction of 99.1 and 99.9%, respectively.

Physical, Thermal, and Chemical Properties of Fly Ash Cenospheres Obtained from Different Sources.

Cenospheres are hollow particles in fly ash, a by-product of coal burning, and are widely used as a reinforcement when developing low-density composites called syntactic foams. This study has investigated the physical, chemical, and thermal properties of cenospheres obtained from three different sources, designated as CS1, CS2, and CS3, for the development of syntactic foams. Cenospheres with particle sizes ranging from 40 to 500 μm were studied. Different particle distribution by size was observed, and the most uniform distribution of CS particles was in the case of CS2: above 74% with dimensions from 100 to 150 μm. The CS bulk had a similar density for all samples and amounted to around 0.4 g·cm-3, with a particle shell material density of 2.1 g·cm-3. Post-heat-treatment samples showed the development of a SiO2 phase in the cenospheres, which was not present in the as-received product. CS3 had the highest quantity of Si compared to the other two, showing the difference in source quality. Energy-dispersive X-ray spectrometry and a chemical analysis of the CS revealed that the main components of the studied CS were SiO2 and Al2O3. In the case of CS1 and CS2, the sum of these components was on average from 93 to 95%. In the case of CS3, the sum of SiO2 and Al2O3 did not exceed 86%, and Fe2O3 and K2O were present in appreciable quantities in CS3. Cenospheres CS1 and CS2 did not sinter during heat treatment up to 1200 °C, while sample CS3 was already subjected to sintering at 1100 °C because of the presence of a quartz phase, Fe2O3 and K2O. For the application of a metallic layer and subsequent consolidation via spark plasma sintering, CS2 can be deemed the most physically, thermally, and chemically suitable.

Construction of PANI‐ZnFe2O4/FAC materials with fly ash cenospheres beads as a carrier to enhance the degradation of Methylene Blue

AbstractIn this study, zinc ferrate (ZnFe2O4) and polyaniline (PANI) were coated on the surface of FAC by hydrothermal and in situ polymerisation using the floating property of fly ash cenospheres (FAC) to form PANI‐ZnFe2O4/FAC composites. Compared with other reference materials, the PANI‐ZnFe2O4/FAC material not only solves the problem of less easy recycling, but also has significantly enhanced photocatalytic activity for methylene blue (MB). The significant increase in catalytic efficiency is attributed to the synergistic effect of PANI and ZnFe2O4 on the FAC surface resulting in efficient separation and low photogenerated charge complexation rates. In addition, cycling tests have shown the material to be stable and reusable. Active species capture experiments show that ⋅O2− and h+ play a dominant role in the reaction system.

The Workability and Mechanical Performance of Fly Ash Cenosphere-Desert Sand Ceramsite Concrete: An Experimental Study and Analysis.

In order to alleviate the shortage of sand resources for construction, make full use of industrial waste and promote the development of green lightweight aggregate concrete in the desert and surrounding areas, this paper proposes a new lightweight ceramsite concrete, fly ash cenospheres and desert sand ceramsite concrete (FDCC). An orthogonal test was conducted to analyze the effects of the desert sand (DS) replacing ratio, fly ash cenosphere (FAC) replacing ratio and polymer emulsion (PLE) addition on the damage patterns, slump, apparent density and compressive strength of the FDCC. The results showed that the most influential factors for the slump, apparent density and compressive strength of the FDCC were the FAC replacing ratio, FAC replacing ratio and DS replacing ratio, respectively. Meanwhile, the PLE addition had little effect on the workability or mechanical performance of the FDCC. With the increase in the DS replacing ratio, the slump decreased rapidly and the compressive strength reached its peak value, increasing by 20.6% when the DS replacing ratio was 20%. With the increase in the FAC replacing ratio, the slump increased by 106%, the apparent density decreased gradually and the compressive decreased and then increased, reaching its lowest value when the FAC replacing ratio was 20%. According to the synthetic evaluation analysis, the optimum DS replacing ratio, FAC replacing ratio and PLE addition of the FDCC were 20%, 30% and 1%, respectively.

Size-Dependent Oscillation in Optical Spectra from Fly Ash Cenospheres: Particle Sizing Using Darkfield Hyperspectral Interferometry

Abstract Fly ash by-products are emerging biocompatible fillers for a number of construction materials. The value of fly ash as a filler is higher if the content of hollow cenospheres is increased. Here we describe a new method for detection and sizing of fly ash spheres based on darkfield microscopy with hyperspectral image capture to perform white light interferometry. Our method is cost-effective and can provide rapid means for evaluating cenosphere content during the enrichment process. We show that fly ash cenospheres produce a strong oscillation over wavelength in optical recordings. The phenomenon is easiest to observe using microscope imaging techniques that preserve both spatial and spectral information. Frequency is observed to increase in direct proportion to the sphere diameter. The oscillation appears in light recorded from any focal plane on the sphere which indicates that the entire sphere is involved in sustaining the signal, making the detection of cenospheres of different size and displacement within a recording volume productive. There is no oscillation from nonspherical particles of fly ash or other material, so this detection method is highly selective for the cenospheres.

Synthesis of n‐octyl acetate over fly ash cenosphere supported 10‐tungsto‐2‐vanadophosphoric acid (H5PW10V2O40) as a heterogeneous catalyst: Kinetic study

AbstractA 10‐tungsto‐2‐vanadophosphoric acid (H5PW10V2O40) catalyst was prepared, supported on pre‐treated fly ash cenosphere (FAC) by the wet impregnation method, and characterized by analytical methods like Brunauer–Emmett–Teller (BET), x‐ray powder diffraction (XRD), Fourier transform infrared (FTIR), and scanning electron microscope (SEM). The prepared catalyst H5PW10V2O40/FAC was used to synthesize n‐octyl acetate in the batch reactor. The influence of various reaction parameters on conversion was investigated and optimized. The maximum conversion of 81.43% was obtained at optimal conditions, that is, temperature 383 K, catalyst loading 5% (w), molar ratio 1:2 (acetic acid to n‐octyl alcohol), speed of agitation 400 rpm, and molecular sieves 6% (w). The H5PW10V2O40/FAC catalyst recyclability shows that it can be used up to four reaction cycles. The reaction progress was represented by the pseudo second‐order homogeneous (PH) model, and the energy of activation of the reaction was computed as 28.89 kJ/mol. The heterogeneous kinetic models, such as Langmuir Hinshelwood Hougen Watson (LHHW) and Eley–Rideal (ER), were also used to test kinetic data. It was seen that the LHHW model with reactant and product gave the best fit for the experimental data.

Preparation of metakaolin-fly ash cenosphere based geopolymer matrices for passive fire protection

In this paper, fly ash cenosphere (FAC) with spherical and hollow structure has been adopted as a pore-forming agent to prepare low density and high strength geopolymer foams. Serial analyses of physical properties, mineral characterization, and thermostability have been employed to investigate the feasibility of metakaolin (MK)-FAC based geopolymer for passive fire protection. FAC addition not only significantly decreases the dry bulk density and thermal conductivity of geopolymer blocks, but also helps to achieve acceptable compressive strength. Meanwhile, FAC addition into geopolymer matrices has brought obviously negative effects on heat transfer and led to the reaction enthalpy rise under high temperature. Owing to the conversion of the amorphous geopolymer gel at the surface to ceramics and excellent thermal insulation performance, the reverse-side temperatures of the geopolymer specimens with FAC addition from 30 to 90 wt% always maintain at about 260 °C until the end of the fire resistance tests. Although weak reactions between alkali activator and FAC have happened and enhanced the bonding between FAC and geopolymer gels, the improvement in physical properties of the MK-FAC based geopolymers would mainly be attributed to the physical characteristics of the FAC. This study could open opportunities to employ MK-FAC geopolymers as alternatives in the application of thermal insulation and fire protection.

Rheological behaviour, setting time, compressive strength and microstructure of mortar incorporating supplementary cementitious materials and nano-silica.

The setting time of the paste and the rheological properties and microstructure of the mortar after replacing OPC cement with silica fume (SF), fly ash cenosphere (FAC) and nano-silica are studied as a reference for shotcrete applications. The suggested contents of SF, FAC and nano-silica are around 5-7.5%, higher than 20% and 1-3%, respectively, to meet the initial setting time specification. Viscosity and yield stress of mortar are highly dependent on water/cement ratio and paste/sand ratio. At the higher water/cement ratio, viscosity is more based on the paste itself. For SF of 2.5-10%, viscosity and yield stress increase, and the flowability of the mixture decreases. For FAC of 5-25%, viscosity and yield stress increase with a lower rate than SF, and flowability increases at 5% and then decreases as FAC content increases, which, however, is at the same level as the control. When SF and FAC are both added, a tortuous behavior of viscosity is shown. As nano-silica is further added, significant increases in viscosity and yield stress are shown. The compressive strengths of mortar with different supplementary cementitious materials (SCMs) at early ages are close. The difference in compressive strength after 28 days of standard curing is significant. The SF5-FAC15 group exhibits the largest increase in strength for 32.82%. At the age of 2.5 h, the macropore areas distribution of SF5-FAC25-NS1.5 test groups were 31.96%, indicating the lowest macropore area distribution. The secondary hydration reaction of supplementary cementitious materials (SCMs) continuously generates products that fill the pores, and the ultrafine filling effect of nanomaterials improves the compactness of the mortar microstructure and reduces the macropore area distribution. The mercury intrusion test results of the SF5-FAC25-NS1.5 group show that the pores are concentrated within the range of 0.01 to 0.05 μm, and the most probable pore size is significantly smaller than that of the CTR group. As the overall replacement level of SCMs increases, the diffraction peak of calcium hydroxide gradually weakens.