Binding Material Research Articles

Concrete containing recycled concrete coarse aggregate and crushed glass sand: Mitigating the effect of alkali–silica reaction

AbstractThe utilization of recycled concrete and glass aggregates in concrete production has emerged as a highly promising method to significantly increase the recycling rate of waste materials. However, the interaction between alkaline environment and silica present in concrete detrimentally impacts mechanical properties and durability of the concrete due to the significant silica content of the aggregates. This study aims to develop a high‐performance and sustainable concrete to resist alkali–silica reaction (ASR). The study focuses on the use of a blend of ground granulated blast furnace slag (GGBS) and fly ash (FA) as binder materials to mitigate negative effects of the ASR on the mechanical properties and and durability of concrete made with crushed glass sand and coarse recycled concrete aggregate (RCA). Various tests, including ASR expansion, flow, slump, density, compression, three‐point bending, water absorption, and chloride attack, were conducted. Furthermore, microanalysis using scanning electron microscopy and energy‐dispersive x‐ray spectroscopy was performed. Based on the results, it is found that the GGBS is less effective than the FA in reducing the ASR expansion of the concrete, with only 3%, 9%, and 12% decreased expansion as a result of the addition of 20%, 40%, and 70% GGBS to the concrete containing 30% FA, respectively. It is also shown that combining 20% GGBS with 30% FA in the RCA concrete containing glass sand develops similar compressive and flexural strengths and water absorption compared to that containing natural sand. This can be related to the pozzolanic reaction of the FA and GGBS, which helps to retain the alkalis for reducing the crack development and propagation in the concrete. However, further GGBS content leads to a decrease in the strengths and an increase in the water absorption of the concrete. The results of this study point to the significant potential of combining FA and GGBS at an optimum ratio to mitigate the ASR effect on RCA concretes containing crushed glass sand. This approach helps in minimizing the emission of greenhouse gases and other pollutants generated during cement production, thereby mitigating environmental pollution. Additionally, it helps the preservation of natural resources by reducing the depletion of natural sand and coarse aggregate.

Low binder content bricks: a regolith-based solution for sustainable surface construction on the Moon

This work proposes a composite construction material made by a blend of lunar regolith and thermoplastic binders in dry powder form. This solution offers advantages over regolith sintering or melting by requiring lower power consumption and simplifying the manufacturing process. However, its sustainability depends on minimizing the content of the binder material. Drawing from validated concepts used on Earth, such as polymeric concrete and compressed Earth bricks, this paper suggests that binder optimization can be achieved by simplifying and streamlining the manufacturing process, targeting parts with predefined shapes. Standardized elements like bricks or tiles ease production and assembly automation, especially when incorporating interlocking features, simplifying the payload concept transition. After drafting the process with a minimum number of basic steps, this work studies the effects of some process parameters to minimize the weight percentage of the matrix while maintaining reasonable mechanical properties. The compressive and the flexural strength are the targets of an orthogonal array Design of Experiment. Through comparison with reference values for civil engineering, the process demonstrates promising results within an organic phase as low as 10 wt%.

Self-sensing properties of cementless ultra-high performance concrete (UHPC) with slag aggregates

This research addresses the environmental impact of traditional cement-based construction materials and explores sustainable alternatives. The study aims to explore the mechanical properties, flowability, setting time, and self-sensing performance of cementless ultra-high performance concrete (UHPC) by utilizing the electrical properties of electric arc furnace slag (EAF slag) as a replacement for natural aggregates, along with alkali-activated slag as the binding material. Comparative analyses are conducted between cementless UHPC with EAF slag and silica sands, as well as the impact of incorporating carbon fiber. The study reveals that cementless UHPC with EAF slag exhibits improved fluidity and slightly increased setting time compared to UHPC with silica sands, attributed to the spherical shape and ball bearing effect of EAF slag. While the compressive and tensile strength of cementless UHPC with EAF slag is slightly lower than that of UHPC with silica sands, it still meets UHPC standards with strengths of 150 MPa and 8 MPa, respectively. Nonlinear curve fitting accurately quantifies the self-sensing performance, yielding precise simulation results. Importantly, EAF slag-based UHPC exhibits superior self-sensing capabilities, outperforming carbon fiber incorporation. Unlike UHPC with silica sands, which generates substantial noise even with carbon fiber, EAF slag-based UHPC demonstrates effective self-sensing with minimal noise, even in the absence of carbon fiber. This study expands the understanding of self-sensing performance in cementless UHPC by effectively utilizing EAF slag as a replacement for natural aggregates. The results suggest that the valorization of EAF slag has the potential to enhance sustainability and the self-sensing capabilities of cementless UHPC.

Seismic performance of ternary composite geopolymer recycled concrete columns: Experimental study and modeling

In order to achieve seismic-resistant structures cast from green building materials, a new kind of column, ternary composite geopolymer concrete with recycled aggregates containing recycled fireclay brick aggregates (GRA-RFBAC) column, was proposed in this paper. The ternary binder material in GRA-RFBAC was produced by the combination of industrial by-products (ground granulated blast furnace slag (GGBS), recycled fireclay brick powder (RFBP), and fly ash (FA)) and alkali-activated solution. Cyclic loading tests of five reinforced GRA-RFBAC columns, each with a shear-to-span ratio of 3.07, were conducted to investigate the seismic performance. The influence of the recycled aggregate containing recycled fireclay brick aggregate (RA-RFBA) replacement ratio, stirrup spacing, and axial compression ratio on the seismic performance of GRA-RFBAC columns was discussed. The results indicated that all specimens showed similar flexural failure modes under cyclic loading. The first cracking of concrete occurred within the drift ratio range of 0.18%–0.41%, the failure drift ratio varied from 3.27% to 4.11%, and the peak load of the specimens ranged from 237.50 kN to 288.87 kN. Although increasing the RA-RFBA replacement ratio led to a decrease in both the bearing capacity and lateral stiffness of the columns, the GRA-RFBAC columns showed comparable or even better seismic performance than Portland cement concrete columns. Moreover, a prediction model for the skeleton curve of GRA-RFBAC columns was proposed and verified by comparing the prediction results with the test results.

Investigation of mechanical behavior of sustainable construction materials: Recycled glass sand stabilized with natural binder material — Biopolymers

Presented in this paper is a study on the biopolymer treated recycled glass sand (BRGS). The effect of curing period, temperature, initial mixing moisture content and biopolymer concentration on mechanical behaviors of BRGS were examined through unconfined compaction strength (UCS), consolidated and drained triaxial test and scanning electron microscopy (SEM) analysis. The results revealed that biopolymer had a significant improvement on the soil stability. The mixing moisture content, biopolymer concentration and curing condition had a strong influence on soil strength. The strength of BRGS increased with dehydration, while further addition of biopolymer concentration may result in a decrease in strength. It was found that different types of biopolymers had their own preferences for curing conditions. The strength of agar treated RGS (thermal induced biopolymer) cured at 105 ℃ for 30 days was six times stronger than that cured at room temperature, while the optimal curing temperature of alginate treated RGS (ionic gelation biopolymer) was 50 ℃. The BRGS presented a slight decrease in friction angle but a significant increase in cohesion. The SEM image showing biopolymer uniformly wrapped RGS particles.

Assessment of Phytotoxicity of Potable Water Treatment Plant Sludge-bound Compost Pellets on Seed Germination of Radish (Raphanus sativus L.)

Binding loose compost into pellets needs different binding materials. Maintenance of pellet stability highly depends on the binding materials used. Potable water treatment plant sludge (WTPS) has the potential to be used as a binding material due to the high content of clay, organic matter, and nutrients. However, compost and WTPS may contain heavy metals, toxic compounds, salts, and growth inhibitors. Therefore, the determination of the phytotoxicity of WTPS bound compost pellets is essential before amending them to the soil. The present study aimed to assess the phytotoxicity of different pelleted compost using seed germination bioassay of Raphanus sativus L. Four compost pellets were considered (T1: commercial compost pellet (100% compost), T2: commercial integrated pellet (90% compost+10% inorganic fertilizer), T3: WTPS-bound compost pellet (90% compost+10% WTPS), T4: WTPS-bound integrated pellet (80% compost+10% WTPS+10% inorganic fertilizer)) and pellet aqueous extracts (PAE) were prepared, respectively. Distilled water was used as the control. The dilution sequence of PAE as 50% and 100% were tested for seed germination in Petri dishes in a randomized design with three replicates. pH, EC, and selected heavy metals (Al, Zn, Cu and Cr) were determined in PAE. RSG% (Relative Seed Germination %), RRG% (Relative radicle Growth %), and GI% (Germination Index) were calculated for all the PAE after 72 hours. The PAE had a pH range from 6.8-7.2. The Cr was not detected in all 100% PEA. The highest levels of Al and Zn were detected in 100% PAE of T1. All the treatments in both 50% and 100% PAE showed GI% higher than 80% except the 100% PAE of commercial integrated pellet (T2) and WTPS-bound integrated pellet (T4). The PAE from the T2 and T4 showed low RSG% and RRG% and thereby the GI% is low due to high EC in PAE. The GI% of 100% PAE in T2 and T4 was 32.33% and 67.25%, respectively. The lowest values for RSG% and RRG% were recorded for T2 as 44.44% and 72.75%, respectively. Spearman‘s Rank Correlation coefficients were calculated for EC with RSG%, RRG%, and GI% and all variables showed negative correlations as (-0.44), (-0.97), and (-0.69), respectively. This indicates that high EC reduces radical growth and seed germination. PAE at 100% concentration levels of commercial integrated pellet showed high phytotoxicity, and WTPS-bound integrated pellet showed less phytotoxicity while other treatments did not show any sign of phytotoxicity. All the PAE at 50% concentration level were free from phytotoxicity. Hence, 10% WTPS in w/w basis can be used as a binding agent in pelletizing loose compost. Different WTPS concentrations should be tested in binding process for its optimum utilization. 
 Keywords: Bioassay, Compost, Phytotoxicity, Radish, Water treatment plant sludge

Technology for Producing Heat From Composite Coal Fuels in Advanced Oven for Municipal and Household Use

The problem of rational use of coal remains relevant; currently, various technologies have been developed for producing composite solid fuels, briquettes with various binding materials from brown coal deposits in Kyrgyzstan. The widespread use of composite solid fuels (CSF) and coal briquettes in industry, everyday life and public utilities, in our opinion, is limited by two reasons: excessively inflated requirements of existing standards for the physical and mechanical characteristics of briquettes as a product; poor knowledge of optimal conditions for burning briquettes. Our research shows that compressive strength in the range of 15-20 kgf/cm2 provides the necessary strength for the degree of abrasion during transportation and storage of large-sized rectangular CSFs. Reducing the strength requirement to the value indicated above makes it possible to form briquettes from unsorted culm. Among the numerous known binders for briquetting, inorganic types of clays and loams, which are ubiquitous, deserve special attention. It has been established that clays and loams provide the strength of the CSF over 20 kgf/cm2. For the purpose of beneficial use of low-grade fine coal, we carried out briquetting and combustion testing of the resulting briquettes. It has been established that when briquetting coals from the Zhatan and Kumbel deposits with a clay binder, with an increase in the content of fine coals in the composition, the burning time of the briquette increases, as well as the combustion of the combustible mass increases, and the temperature in the combustion space increases. It has been shown that with the help of appropriate minor modifications of standard household stoves it is possible to significantly increase the combustion efficiency of all types of low-grade fuel, including lignite high-ash CSF.

Technology for Producing Composite Solid Fuel From Coals of Kyzyl-Bulak and Kozho-Kelen Deposits and Heated Bitumen

The paper presents the results of a study of the production of composite solid fuels (CSF) from compositions of coal from the Kyzyl-Bulak and Kozho-Kelen deposits and a bitumen binder. The possibilities of producing CSF from a mixture of bitumen and preheated coals have been studied. To determine the dependence of the quality of the resulting CSF on the grinding size, the above coal was crushed into three fractions: a fraction with a particle size of 0-1mm, a fraction with particles of 0-3 mm and a fraction of 0-5 mm. These 3 fractions of coal were subjected to sieve analysis and the granulometric composition was determined, then each fraction individually was subjected to briquetting on a hydraulic press, in a mold with a diameter of 40 mm. Based on the task, pressing took place at 3 parameters, namely: at a pressure of 10 MPa, 15 MPa and 20 MPa. The use of different pressures made it possible to trace the dependence of the quality of the resulting CSF on the pressing pressure and determine the optimal pressure parameter. Briquetting was also carried out at different concentrations of the charge and the mechanical properties of the CSF were determined at a binder concentration of 6, 8, 10%. It has been established that the use of a bitumen-like product (bitumen) as a binding material, obtained as a result of thermal dissolution of coal with oil waste at a temperature of 320-380°C, produces mechanically strong briquettes that have compression resistance up to 106 kg/cm2 and bending resistance up to 7.5 kg/cm2. It has been shown that the mechanical strength of briquettes increases with increasing degree of coal grinding, and also an increase in pressing pressure increases the mechanical strength of briquettes. As the moisture level of coal increases, the mechanical strength of the briquette decreases. The optimal parameters for producing CHP have been established: coal size 0-3 mm: humidity 6.5%, pressing pressure 200 kg/cm2.

Residual water and interfacial bonding effects on the mechanical performance of CNT/fly ash geopolymer binder

AbstractNowadays, geopolymers are advanced alternatives to cementitious materials, where their excellent chemical and fire resistance are some of its most appealing properties. Fly ash geopolymers enable the use of industrial waste materials while converting them into a novel binding material. Their production is accompanied by a much lower CO2 emission when compared to Portland cement. Reinforcing fly ash geopolymers with carbon nanotubes would significantly strengthen its microstructure and with this enhancing the long‐term mechanical and durability performance. The aim of this work is to use reactive molecular dynamics simulation method to optimize the mechanical properties of fly ash geopolymers with nano‐reinforced carbon nanotubes (CNTs). During this study, the impact of humidity and interfacial bonding strength between carbon nanotube and geopolymer is investigated. Our findings show that structural transformations under hydration process comes from the weakening of AlO bond, leading to the elongation of AlO and NaOH bonds, forming aluminum and sodium hydroxyls. Conversely, silicate is not sensitive to water and exhibits hydrophobic behavior. In addition, our results show that there is an optimal value of water content (7.17 wt.%) that makes the geopolymer nanostructure strengthen. The related elastic modulus rises by 21.56%, 20.60%, and 18.41% for Si/Al ratio of 1, 2, and 3, respectively. Inserting carbon nanofillers to fly ash nanostructure has remarkably shown an interesting strength enhancement. More precisely, when interfacial bonding concentration is around 19.36%, it is observed a positively increasing of the compressive strength, shear, indentation and elastic modulus with 39%, 65.2%, 72.3%, and 144.85%, respectively. Reduced density gradient supports that the interaction between carbon nanotube and fly ash geopolymer is dominated by a van der Waals one.

Effect of the incorporation of spent diatomaceous earths on the properties of alkaline activation cements based on sewage sludge ash

The aim of this research is to evaluate the synergistic effect of the incorporation of spent diatomaceous earth (SDE) from beer filtration on the technological properties of alkaline-activated cements (AACs) based on sewage sludge ash (SSA). Pastes have been manufactured by mixing different amounts of precursor, SSA (30–70% by weight) and SDE (30–70% by weight). The cements were activated using a solution of sodium silicate (50% by weight) and sodium hydroxide (50% by weight NaOH with 8 M) as activator. A liquid/binder (l/b) ratio of 1.2 were used for cements with 30–40% by weight of SSA and 1.0 for binders with 50–70% by weight of SSA. The specimens were cured at room temperature for 7, 28 and 56 days. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used for the microstructural characterization of the AACs. The mix proportion of the precursors or the CaO/SiO ratio exerts a substantial impact on the physical, mechanical, and thermal characteristics of the examined AACs. Binders containing 40% by weight SSA and 60% by weight SDE show optimal technological properties, reaching compressive strengths of 32.8 and 36.8 MPa at 28 and 56 days of curing, respectively. This may be due to the formation of different gel types according to SEM analysis: a compact gel phase characterized by a fibrous structure corresponding to the N-(A)-S-H gel surrounding flatter and more uniform zones corresponding to the calcium aluminosilicate gel, C-A-S-H, and a mixed amorphous N,C-A-S-H gel. The results indicated that is possible to produce more sustainable alternative binding materials from the recovery of two types of waste: one from the wastewater treatment, and the other originating from the filtration process in the brewing industry.

Influence of the Composition of Asphalt Granular Concrete Mixture on the Deformation of the Coating Layer During the Construction of the Road Pavement

Statement of the problem. The introduction of cement into the composition of the bitumen emulsion at the stage of preparation affects not only the strength of the layer, but also the properties of the asphalt granular concrete mixture, which must be taken into account when developing technological processes for compaction. Under the action of the compacting load, taking into account the content of cement in the binder material, the deformability and rigidity of the compacted layer change. The change in the rigidity of the layer affects the choice of parameters of compacting machines. Therefore, whiledeveloping a pavement technology using asphalt-granular concrete mixes using combined binders, it is necessary to establish the effect of cement content on the deformability and rigidity of the compacted layer. Results. The results on the influence of the cement content in the combined binder in the asphalt-granular concrete mix on the deformability of the layer under the action of the compacting load are presented. Dependences were obtained to determine the residual deformation and rigidity of the mix layer under the action of a load, taking into account the layer thickness and cement content. Conclusions. The use of a combined binder (bitumen emulsion and cement), depending on the cement content, leads to a decrease in the deformability of the layer of asphalt granular concrete mixture up to 40 %, regardless of the size of the granulate fractions and the thickness of the layer during laying, as well as an increase in the rigidity of the layer from 1.8 to 2.1 times, which must be taken into account when choosing the parameters of the rollers in the compaction process.

BEHAVIOR OF PHYSICAL AND DENSITY PROPERTIES OF SOFT SOIL STABILIZED WITH NICKEL SLAG

Soft soils have become a significant challenge in geotechnical engineering, due to their low bearing capacity and susceptibility to deformation. Chemical stabilization using nickel slag is an alternative solution and is considered more environmentally friendly. This article focuses on the utilization of nickel slag as a binder material aimed at behavior of physical and mechanical properties of soft soil stabilized with nickel slag soft soil. The nickel slag was carried out with variations of 3%, 6%, 9% and 12% by weight of soil. All the test using ASTM procedure in order to gain physical and mechanical value. The results of this study showed that plasticity index decrease with the increasing of slag nickel concentration, where it is an indication of a change in soil consistency, shifting from initially soft to now medium. Futher, the optimum dry density (d-opt) value of the original soil used was 1.09 gr/cm3, while the optimum dry density (d) values at 3%, 6%, 9% and 12% nickel slag addition were 1.12 gr/cm3; 1.15 gr/cm3; 1.19 gr/cm3 and 1.22 gr/cm3, respectively. These results show that the presence of nickel slag can increase influence the physical and density properties of soft soil, which indicates that nickel slag has the potential to be used as a stabilization material in soft soil.

Eco-friendly Noise-absorbing Panels from Waste Materials: A Sustainable Solution to Control Noise Pollution

This research article deals with one of the major forms of pollution that is invisible but is a threat to living beings. Controlling noise pollution is important so to deal with this, a test was performed using a method known as the impedance tube method. To tackle this noise pollution a sustainable material would be good to use, so waste coming from food industries such as orange peel, sugarcane husk, and eggshells are used with newspaper sludge as a binding material. Disks were prepared of 90mm with different constituents of waste material and paper sludge. The test result showed that these panels were able to reduce sound coming from the source to the receiver side. Sound absorption capacity is different for every material depending upon their structural features. The test was done with 120 decibels of sound and at 120 decibels the SAC (sound absorption coefficient) was 0.35 which is better than other commercially available chemical-infused materials such as glass wool, mineral wool etc. As they are not better for the environment as well as living around. They cause lung disease if inhaled and skin problems come in contact with them. Materials in use for soundproofing have polyurethane which releases a high amount of smoke if brunt hence we cannot rely on this in case of fire. Hence environmentally friendly as well as materials that do not catch fire or realise high amounts of smoke and are also cost-effective should be used to reduce noise pollution in the environment we are living in.

Salt Effects on the Mechanical Properties of Ionic Conductive Polymer: A Molecular Dynamics Study.

Functional polymers can be used as electrolyte and binder materials in solid-state batteries. This often requires performance targets in terms of both the transport and mechanical properties. In this work, a model ionic conductive polymer system, i.e., poly(ethylene oxide)-LiTFSI, was used to study the impact of salt concentrations on mechanical properties, including different types of elastic moduli and the viscoelasticity with both nonequilibrium and equilibrium molecular dynamics simulations. We found an encouragingly good agreement between experiments and simulations regarding Young's modulus, bulk modulus, and viscosity. In addition, we identified an intermediate salt concentration at which the system shows high ionic conductivity, high Young's modulus, and short elastic restoration time. Therefore, this study laid the groundwork for investigating ionic conductive polymer binders with self-healing functionality from molecular dynamics simulations.

The influence of NaOH concentration on the strength and microstructure of ceramic binders prepared from coal gangue through geopolymerization

The efficient utilization of coal gangue plays an indispensable role in reducing environmental pressure, improving resource utilization efficiency and promoting green development. As a kind of solid waste rich in silicon and aluminium, coal gangue can be used to prepare ceramic materials. Therefore, a new ceramic preparation process was proposed in this study to prepare ceramic binders for grinding wheels by geopolymerization. The SiO2-B2O3-Al2O3-RO-R2O ceramic binder, a green and low-cost material, was successfully prepared using this method. The effect of the concentration of NaOH on the mechanical properties and microstructure of the ceramic binder was also studied. The strength and microstructure of different ceramic binders were characterized by XRD, TG-DTG, SEM-EDS and FT-IR. The results show that the bending strength of the geopolymer ceramic binder increases proportionately with the increase of NaOH concentration. When the concentration of sodium hydroxide is 15 M, the bending strength reaches 19 MPa. N-A-S-H gel and zeolite formed in the geopolymerization reaction and the pores formed in the sintering process have a significant effect on the bending strength of the ceramic binder. This technology can significantly stimulate the chemical activity of coal gangue and provide innovative ideas for efficient utilization of coal gangue.

Limitations of Polyacrylic Acid Binders When Employed in Thick LNMO Li-ion Battery Electrodes

Polyacrylic acid (PAA) is here studied as a binder material for LiNi0.5Mn1.5O4 (LNMO) cathodes for lithium-ion batteries. When the LNMO electrodes are fabricated with an active mass loading of ∼10 mg cm−2 (∼1.5 mA h cm−2), poor discharge capacity and short cycle life is obtained in full-cells with graphite electrodes. The electrochemical results with PAA are compared with a commonly used water-based binder, sodium carboxymethyl cellulose (CMC), which shows better electrochemical performance. The main cause for these problems in PAA based cells is identified to be the high internal resistance in the initial cycles, caused by factors such as contact resistance, inhomogeneous binder distribution and poor electrolyte wetting of the active material.

Fully time-dependent cloud formation from a non-equilibrium gas-phase in exoplanetary atmospheres

Context. Recent observations suggest the presence of clouds in exoplanet atmospheres, but they have also shown that certain chemical species in the upper atmosphere might not be in chemical equilibrium. Present and future interpretation of data from, for example, CHEOPS, JWST, PLATO, and Ariel require a combined understanding of the gas-phase and the cloud chemistry. Aims. The goal of this work is to calculate the two main cloud formation processes, nucleation, and bulk growth consistently from a non-equilibrium gas phase. The aim is also to explore the interaction between a kinetic gas-phase and cloud microphysics. Methods. The cloud formation is modelled using the moment method and kinetic nucleation, which are coupled to a gas-phase kinetic rate network. Specifically, the formation of cloud condensation nuclei is derived from cluster rates that include the thermochemical data of (TiO2)N from N = 1 to 15. The surface growth of nine bulk Al, Fe, Mg, O, Si, S, and Ti binding materials considers the respective gas-phase species through condensation and surface reactions as derived from kinetic disequilibrium. The effect of the completeness of rate networks and the time evolution of the cloud particle formation is studied for an example exoplanet, HD 209458 b. Results. A consistent, fully time-dependent cloud formation model in chemical disequilibrium with respect to nucleation, bulk growth, and the gas-phase is presented and first test cases are studied. This model shows that cloud formation in exoplanet atmospheres is a fast process. This confirms previous findings that the formation of cloud particles is a local process. Tests on selected locations within the atmosphere of the gas-giant HD 209458 b show that the cloud particle number density and volume reach constant values within 1 s. The complex kinetic polymer nucleation of TiO2 confirms results from classical nucleation models. The surface reactions of SiO[s] and SiO2[s] can create a catalytic cycle that dissociates H2 to 2 H, resulting in a reduction of the CH4 number densities.

Accelerated carbonation of regenerated binding material prepared with waste cement paste powder

An approach for the efficient re-utilisation of waste cement paste powders is proposed, wherein the powders are heated to a certain temperature to prepare regenerated binding materials (RBMs), and then rapidly carbonated by high-concentration carbon dioxide to prepare high-strength products. The structural evolution during the heating process of waste cement paste powder and the carbonation process of RBMs were investigated by X-ray diffraction analysis, scanning electron microscopy and 29Si nuclear magnetic resonance spectrum, and the compressive strength of the carbonated RBM samples was measured. The results show that the differences in carbonation reactivity, carbonation products of the RBMs and properties of carbonated RBMs can mainly be attributed to the differences in the degree of structural order of newly formed β-dicalcium silicate (C2S), the content of β-C2S, free calcium oxide (f-CaO) and incompletely decomposed calcium silicate hydrate (C–S–H) in RBMs. The strength of the carbonated sample of RBM prepared at 1050°C was the highest, followed by that prepared at 950°C, which was significantly higher than those prepared at 650, 750 and 850°C. The content of highly ordered β-C2S in RBMs with high carbonation reactivity and the dense stacking of the carbonation products are beneficial for the mechanical properties.

Changes in Functional Groups and Crystal Structure of Coal Tar Pitch with Respect to Carbonization Temperature

In this study, changes in the microstructure of coal-tar pitch (CTP) during successive processes, including pyrolysis, polycondensation, and crystallization, were examined in connection with the resulting variations in structure factors, as measured by X-ray diffraction (XRD) analysis, and functional groups, as confirmed by Fourier transform infrared (FTIR) spectroscopy. To this end, four zones were defined based on variations in crystallinity, which were indicated by d002 and Lc. Each zone was further characterized by interpreting crystallinity development in relation to changes in functional groups and specimen height. At around 400 °C, polycondensation occurred as the C-Har and C-Hal peaks decreased in intensity. These peak reductions coincided with the formation of mesophase spheres, resulting in enhanced crystallinity. Subsequently, at around 500 °C, the peak intensity of C-H and COOH decreased, which was attributed to the release of large amounts of gases. This led to sharp volume changes and a temporary reduction in crystallinity. All these results suggest that changes in the functional groups of CTP at lower temperatures (600 °C or less) during the carbonization process are closely associated with variations in its crystallinity. The major findings of the present study provide valuable insights for designing highly effective processes in the manufacturing of synthetic graphite blocks using CTP as a binder material, including by selecting appropriate temperature ranges to minimize volume expansion and crystallinity degradation and determining the lowest possible carbonization temperature to ensure adequate binder strength.

Effect of zinc industrial waste on the mechanical and microstructural properties of the ternary blended concrete

<p>The rapid growth of infrastructure leads to industrial waste accumulation and natural resource depletion, raising the need for sustainable solutions. When zinc is refined, a significant amount of non-biodegradable material called jarosite (JS) is generated, requiring proper environmentally friendly disposal techniques. The present study investigates ternary blended of Portland cement with partial replacement of 20% ground granulated blast furnace slag and jarosite at (5 – 25%) as a binder material to develop a sustainable concrete mix. To comprehend the effectiveness of jarosite-GGBS blends in concrete experimental research is performed to investigate the mechanical properties of ternary blended concrete. Additionally, SEM and XRD analysis were used to observe the microstructure and chemical phases of the developed concrete. From the experimental investigations, it is perceived that the incorporation of jarosite-GGBS blended concrete provided an increase in strength properties for all the mix proportions. The microstructure study shows a decrease in voids and the formation of sufficient CSH gel, justifying improved mechanical properties. The maximum increase in compressive strength of 50.93% is observed for the 10% replacement of the level of jarosite in the concrete mix. The overall research findings provide insight into the functionality of GGBS and jarosite blended concrete and the potential of jarosite as a sustainable, reusable industrial waste material.</p>