Reaction Products Research Articles

Mid-Infrared Dispersion Spectroscopy as a Tool for Monitoring Time-Resolved Chemical Reactions on the Examples of Enzyme Kinetics and Mutarotation of Sugars.

Ongoing technological advancements in the field of mid-infrared (MIR) spectroscopy continuously yield novel sensing modalities, offering capabilities beyond traditional techniques like Fourier transform infrared spectroscopy (FT-IR). One such advancement is MIR dispersion spectroscopy, utilizing a tunable quantum cascade laser and Mach-Zehnder interferometer for liquid-phase analysis. Our study assesses the performance of a custom MIR dispersion spectrometer at its current development stage, benchmarks its performance against FT-IR, and validates its potential for time-resolved chemical reaction monitoring. Unlike conventional methods of IR spectroscopy measuring molecular absorptions using intensity attenuation, our method detects refractive index changes (phase shifts) down to a level of 6.1 × 10-7 refractive index units (RIU). This results in 1.5 times better sensitivity with a sevenfold increase in analytical path length, yielding heightened robustness for the analysis of liquids compared to FT-IR. As a case study, we monitor the catalytic activity of invertase with sucrose, observing the formation of resultant monosaccharides and their progression toward thermodynamic equilibrium. Anomalous refractive index spectra of reaction mixtures, with substrate concentrations ranging from 2.5 to 25 g/L, are recorded, and analyzed at various temperatures, yielding Michaelis-Menten kinetics findings comparable to the literature. Additionally, the first-time application of two-dimensional correlation spectroscopy on the recorded dynamic dispersion spectra correctly identifies the mutarotation of reaction products (glucose and fructose). The results demonstrate high precision and sensitivity in investigating complex time-dependent chemical reactions via broadband refractive index changes.

Chloride transport in alkali-activated materials influenced by different reaction products: a review

Alkali-activated materials (AAMs) are regarded as a substitute for Portland cement. They have high chloride resistance and a low carbon dioxide footprint. The aim of this review is to provide a multi-scale perspective to understand material–product–microstructure–property relationships in terms of the chloride binding behaviour of AAMs. The physical and chemical chloride stability of different reaction products is summarised from nanostructure, to microstructure to macro properties. An analysis of studies in the literature gives an overview of recent progress in chloride transport in AAMs influenced by different reaction products. Results show that a higher calcium/silicon, aluminium/silicon molar ratios and alkali content increase the formation of amorphous phases, leading to a denser microstructure and lower chloride penetration in AAMs. Higher magnesium oxide and aluminium oxide contents result in increased formation of hydrotalcite. The enhanced physical and chemical absorption of chloride by hydrotalcite leads to higher resistance of chloride penetration in AAMs. Investigation of increasing chloride resistance could potentially focus on increasing gel and hydrotalcite formation.

Construction of Porous Aromatic Frameworks with Specifically Designed Motifs for Charge Storage and Transport.

ConspectusPorous frameworks possess high porosity and adjustable functions. The two features conjointly create sufficient interfaces for matter exchange and energy transfer within the skeletons. For crystalline porous frameworks, including metal organic frameworks (MOFs) and covalent organic frameworks (COFs), their long-range ordered structures indeed play an important role in managing versatile physicochemical behaviors such as electron transfer or band gap engineering. It is now feasible to predict their functions based on the unveiled structures and structure-performance relationships. In contrast, porous organic frameworks (POFs) represent a member of the porous solid family with no long-range regularity. For the case of POFs, the randomly packed building units and their disordered connections hinder the electronic structural consistency throughout the entire networks. However, many investigations have demonstrated that the functions of POFs could also be designed and originated from their local motifs.In this Account, we will first provide an overview of the design and synthesis principles for porous aromatic frameworks (PAFs), which are a typical family of POFs with high porosity and exceptional stability. Specifically, the functions achieved by the specific design and synthesis of in-framework motifs will be demonstrated. This strategy is particularly intuitive to introduce desired functions to PAFs, owing to the exceptional tolerance of PAFs to harsh chemical treatments and synthetic conditions. The local structures can be either obtained by selecting suitable building units, sometimes with the aid of computational screening, or emerge as the product of coupling reactions during the synthetic process. Radical PAFs can be obtained by incorporating a persistent radical molecule as a building unit, and the rigid and porous framework may facilitate the formation of radical species by trapping spins in the organic network, which could avoid the delocalizing and recombining processes. Alternatively, radical motifs can also be formed during the formation of the framework linkages. The coupling reaction plays an important role in the construction of functional motifs like diacetylene. The highly porous, radical PAFs showed significant performance as anodes of lithium-ion batteries. To improve the charge transport within the framework, the building units and their connecting manner were cohesively considered, and the framework with a fully conjugated backbone was built up. In another case, the explicit product of the cross-coupling reaction ensured the precise assembly of two building units with electron donating and accepting abilities; therefore, the moving direction of photogenerated electrons was rationally controlled. Constructing a fully conjugated backbone or rationally designing a D-A system for charge transfer in porous frameworks introduced exciting properties for photovoltaic and photocatalysis, and their highly porous, stable frameworks improved their functional applications for perovskite solar cells and chemical productions. These investigations shed light on the designable combination of intrinsic functional motifs with highly porous organic frameworks for effective energy storage and conversion.

Development of crosslinked gelatin films through Maillard reaction and reinforced with poly(vinyl alcohol) for active food packaging

In order to improve the functionality of natural gelatin films for active food packaging applications, a combined strategy of crosslinking via Maillard reaction and blending enhancement incorporated with poly(vinyl alcohol) (PVA) was explored. In this study, when the mass ratio of gelatin to glucose was 10:1, Maillard reaction of crosslinked gelatin film was the highest, UV absorption and browning index reached the maximum. Infrared analysis showed that PVA could form strong interfacial interactions with gelatin matrix. The presence of PVA could significantly improve the toughness, water absorption, transparency, and oxygen barrier properties of crosslinked gelatin films. When the amount of PVA reached 5 %, elongation at break and oxygen barrier properties of crosslinked gelatin film were improved by 76.7 % and 47.9 % compared with pure crosslinked gelatin film. Even when the amount of PVA reached 10 %, UV absorption (at 315 nm) of crosslinked gelatin film still exceeded 98.7 %. The addition of PVA could accelerate the dissolution and swelling of crosslinked gelatin films, promoting the migration and release of active substances (Maillard reaction products (MRPs)). The two antioxidant activities tests (DPPH and ABTS method) achieved the highest free radical scavenging rates of 71.6 % and 91.2 %, respectively, with corresponding PVA addition of 5 % and 7.5 %. After continuing to add PVA, antioxidant activities began to significantly decrease, which was directly related to the decrease in the generation of MRPs. Therefore, crosslinked gelatin films reinforced with PVA can be considerable potential as active films for renewable food packaging applications.

Non-enzymatic degradation of flavan-3-ols by ascorbic acid- and sugar-derived aldehydes during storage of apple juices and concentrates produced with the innovative spiral filter press

Potentially health-promoting concentrations of flavan-3-ols were previously shown to be retained in apple juices produced with the emerging spiral filter press. Due to the novelty of this technology, the factors governing the stability of flavan-3-ol-rich apple juices have only scarcely been studied. Therefore, we produced flavan-3-ol-rich apple juices and concentrates (16, 40, 70 °Brix) supplemented with ascorbic acid (0.0, 0.2, 1.0 g/L) according to common practice. Flavan-3-ols (DP1-7) and twelve flavan-3-ol reaction products were comprehensively characterized and monitored during storage for 16 weeks at 20 and 37 °C, employing RP-UHPLC- and HILIC-DAD-ESI(−)-QTOF-HR-MS/MS. Flavan-3-ol degradation followed a second-order reaction kinetic, being up to 3.5-times faster in concentrates (70 °Brix) than in single strength juices (16 °Brix). Furthermore, they diminished substantially faster compared to other phenolic compounds. For instance, after 16-weeks at 20 °C, the maximum loss of flavan-3-ols (−70 %) was greater than those of hydroxycinnamic acids (−18 %) and dihydrochalcones (−12 %). We observed that flavan-3-ols formed adducts with sugars and other carbonyls, such as 5-(hydroxymethyl)furfural and the ascorbic acid-derived L-xylosone. Increased degradation rates correlated particularly with increased furan aldehyde levels as found in concentrates stored at elevated temperatures. These insights could be used for optimizing production, distribution, and storage of flavan-3-ol-rich apple juices and other foods and beverages.

Strength and deformation characteristics of waste mud–solidified soil

The treatment, disposal, and resource utilization of waste mud are challenges for engineering construction. This study investigates the road performance of waste mud–solidified soil and explains how solidifying materials influence the strength and deformation characteristics of waste mud. Unconfined compressive strength tests, consolidated undrained triaxial shear tests, resonant column tests, and consolidation compression tests were conducted to evaluate the solidification effect. The test results show that with an increase in cement content from 5 to 9%, the unconfined compressive strength of the waste mud–solidified soil increased by over 100%, the curing time was extended from 3 to 28 days, and the unconfined compressive strength increased by approximately 70%. However, an increase in initial water content from 40 to 60% reduced the unconfined compressive strength by 50%. With the increase of cement content from 5 to 9%, the cohesion and friction angles increased by approximately 78% and 24%, respectively. The initial shear modulus under dynamic shear increased by approximately 38% and the shear strain corresponding to a damping ratio decay to 70% of the initial shear modulus decreased by nearly 11%. The compression coefficient decreased by approximately 55%. Scanning electron microscopy and X-ray diffraction tests showed that a higher cement content led to the formation of more hydration reaction products, especially an increase in the content of AlPO4, which can effectively fill the pores between soil particles, enhance the bonding between soil particles, and form a skeleton with soil particles to improve compactness. Consequently, the strength of the waste mud–solidified soil increased significantly while its compressibility decreased. This study can provide data support for dynamic characteristics of waste mud solidified soil subgrade.

Pd-catalyzed 5-exo-dig cyclization/etherification cascade of N-propargyl arylamines for the synthesis of polysubstituted furans.

A method for the synthesis of furans bearing indoline skeletons was developed via an intramolecular palladium-catalyzed 5-exo-dig cyclization/etherification cascade of N-propargyl arylamines containing a 1,3-dicarbonyl side chain. This method realized the first capture of vinyl carbopalladiums by ketones as O-nucleophiles and showed a wide range of substrate tolerability affording trisubstituted furans in various yields. The enantioselective version for this domino process and diverse derivatizations of the reaction products were also studied.

Development of high-strength geopolymer mortar based on fly ash-slag: Correlational analysis of microstructural and mechanical properties and environmental assessment

Given the insufficient mechanical performance of existing fly ash-based geopolymer mortars under ambient curing conditions, this study is dedicated to developing a high-strength geopolymer mortar that meets the requirements of modern structural engineering. Based on the rheological performance tests of the fresh geopolymer mortar, the evolution of its rheological characteristics was revealed. Through macroscopic mechanical performance tests, the influence of slag content on the compressive and flexural strength of geopolymer mortar was clarified. Employing microstructural performance testing methods such as Thermogravimetric and Mercury Intrusion Porosimetry, the micro-mechanisms behind the improvement of mechanical properties were revealed. Utilizing the grey relational analysis method, a framework was established to analyze the correlation between the microstructural and macroscopic mechanical properties of geopolymer mortar. Additionally, an assessment system for evaluating environmental and economic benefits was developed using statistical analysis methods. The results show that increasing slag content enhances the yield stress and plastic viscosity of geopolymer mortar. Optimizing slag content boosts the compressive strength of fly ash-based geopolymer mortar, reaching up to 88.13 MPa under ambient curing conditions. An optimal amount of slag also promotes gel formation during polymerization, improving the internal pore structure. Furthermore, the content of reaction products correlates more strongly with macroscopic mechanical properties than pore structure characteristics. Geopolymer mortar also presents significant environmental and economic advantages over traditional cement-based materials, with its carbon and economic intensity indices at only 5.50 % and 10.80 %, respectively, of those in cement-based materials.

Influence of contouring on the microstructure and micromechanical properties of Laser Powder Bed Fusion (LPBF) processed Al6061 enhanced with reactive particles

Age-hardenable aluminum alloys are of interest for powder bed fusion (PBF) additive manufacturing to produce lightweight, high-performance custom components. The successful processing of these alloys depends on specific alloying and print techniques to overcome defects that significantly degrade mechanical properties of PBF aluminum. The Reactive Additive Manufacturing (RAM) process modifieds alloy feedstock with reactive precursors which inoculate equiaxed microstructures during solidification, resulting in a reduction of columnar grain growth and shrinkage cracks. Additionally, surface quality is addressed by contouring, which retraces the perimeters of printed layers to produce smooth, fully fused surfaces. However, the combination of RAM and contouring methods has not been previously described in the literature, raising questions about the extent of refinement which is achieved when RAM particles are remelted by contouring laser sweeps. In this research, X-ray microcomputed tomography (XCT) was used to provide a complete characterization of RAM particles and defects in an AA6061-RAM alloy in 3D. The non-destructive XCT technique was used to quantify pore and particle distributions in the contoured alloy volumes and compared directly to hatched regions. The resulting three-dimensional analysis was correlated to traditional 2D microstructure quantification and nanoindentation experiments, providing a multimodal quantitative description of sub-micron grains, reaction products, and micromechanical properties. The study reveals that RAM particles inhibit cracking while simultaneously reducing the variance in mechanical properties between hatched and contoured regions of the build volume.

Exploring the Complex Chemistry and Degradation of Ascorbic Acid in Aqueous Nanoparticle Synthesis.

Ascorbic acid (AA) is the most widely used reductant for noble metal nanoparticle (NP) synthesis. Despite the synthetic relevance, its aqueous chemistry remains misunderstood, due in part to various assumptions about its reduction pathway which are insufficiently supported by experimental evidence. This study aims to provide an understanding of the complex chemistry associated with AA under aqueous conditions. We demonstrate that (i) AA undergoes appreciable degradation in alkaline solution on a timescale relevant to NP synthesis, (ii) contrary to popular belief, AA does not degrade into dehydroascorbic acid (DHA), nor is DHA the oxidized product of AA under noble metal NP synthetic conditions, (iii) DHA, which readily degrades under alkaline conditions, can also effectively reduce metal salt precursors to metal NPs, (iv) neither ascorbate nor dehydroascorbate act as surface capping agents post-synthetically on the NPs (v) AA degradation time greatly affects the morphology and polydispersity of the resultant NP. Results from our mechanistic investigation enabled us to utilize purposefully-aged reductants to achieve control over shape yield and monodispersity in the seed-mediated synthesis of Au nanorods. Our findings have important implications for achieving monodispersed products in the many metal NP synthesis reactions that make use of AA as a reducing agent.

Exploring the Complex Chemistry and Degradation of Ascorbic Acid in Aqueous Nanoparticle Synthesis

Ascorbic acid (AA) is the most widely used reductant for noble metal nanoparticle (NP) synthesis. Despite the synthetic relevance, its aqueous chemistry remains misunderstood, due in part to various assumptions about its reduction pathway which are insufficiently supported by experimental evidence. This study aims to provide an understanding of the complex chemistry associated with AA under aqueous conditions. We demonstrate that (i) AA undergoes appreciable degradation in alkaline solution on a timescale relevant to NP synthesis, (ii) contrary to popular belief, AA does not degrade into dehydroascorbic acid (DHA), nor is DHA the oxidized product of AA under noble metal NP synthetic conditions, (iii) DHA, which readily degrades under alkaline conditions, can also effectively reduce metal salt precursors to metal NPs, (iv) neither ascorbate nor dehydroascorbate act as surface capping agents post‐synthetically on the NPs (v) AA degradation time greatly affects the morphology and polydispersity of the resultant NP. Results from our mechanistic investigation enabled us to utilize purposefully‐aged reductants to achieve control over shape yield and monodispersity in the seed‐mediated synthesis of Au nanorods. Our findings have important implications for achieving monodispersed products in the many metal NP synthesis reactions that make use of AA as a reducing agent.

A Generalized Coordination Engineering Strategy for Single-Atom Catalysts toward Efficient Hydrogen Peroxide Electrosynthesis.

Designing non-noble metal single-atom catalysts (M-SACs) for two-electron oxygen reduction reaction (2e-ORR) is attractive for the hydrogen peroxide (H2O2) electrosynthesis, in which the coordination configuration of the M-SACs essentially affects the reaction activity and product selectivity. Though extensively investigated, a generalized coordination engineering strategy has not yet been proposed, which fundamentally hinders the rational design of M-SACs with optimized catalytic capabilities. Herein, a generalized coordination engineering strategy is proposed for M-SACs toward H2O2 electrosynthesis via introducing heteroatoms (e.g., oxygen or sulfur atoms) with higher or lower electronegativity than nitrogen atoms into the first sphere of metal-N4 system to tailor their electronic structure and adjust the adsorption strength for *OOH intermediates, respectively, thus optimizing their electrocatalytic capability for 2e-ORR. Specifically, the (O, N)-coordinated Co SAC (Co-N3O) and (S, N)-coordinated Ni SAC (Ni-N3S) are precisely synthesized, and both present superior 2e-ORR activity (Eonset: ≈0.80V versus RHE) and selectivity (≈90%) in alkaline conditions compared with conventional Co-N4 and Ni-N4 sites. The high H2O2 yield rates of 14.2 and 17.5moLg-1h-1 and long-term stability over 12h are respectively achieved for Co-N3O and Ni-N3S. Such favorable 2e-ORR pathway of the catalysts is also theoretically confirmed by the kinetics simulations.

In situ imaging of intracellular miRNAs in tumour cells by branched hybridisation chain reaction.

The ability to visualise microRNA in situ is crucial for studying microRNAs, their microRNA-associated biological functions and disease diagnosis. Traditional fluorescence in situ hybridisation methods based on paraformaldehyde fixation of microRNAs suffer from release of microRNAs from cells, which limits the sensitivity of in situ hybridisation, making them unsuitable for the detection of small, low-abundance microRNAs. To reduce the loss, microRNAs were covalently cross-linked to proteins within cells by combining EDC and paraformaldehyde, and the target microRNA was used as the initiator chain for a branched hybridisation chain reaction to detect microRNA expression levels in situ. A simplified branched hybridisation chain reaction can be realised by coupling two hybridisation chain reaction circuits with a hairpin linker. Upon forming the primary hybridisation chain reaction product with extended sequence, this sequence reacts with the linker hairpin H3 to release the initiator sequence, resulting in the formation of numerous dendritic branched hybridisation chain reaction products. Imaging results show that this technique can detect microRNAs with high sensitivity and selectivity at both the single-cell and single-molecule levels. Compared with the traditional fluorescence in situ hybridisation technique, this method greatly improves the sensitivity and image resolution of in situ imaging detection. Therefore, we believe that the target-initiated branched hybridisation chain reaction based in situ detection method provides a reliable assay platform for analysing disease-related microRNA expression.

Modelling chemical processes in explicit solvents with machine learning potentials

Solvent effects influence all stages of the chemical processes, modulating the stability of intermediates and transition states, as well as altering reaction rates and product ratios. However, accurately modelling these effects remains challenging. Here, we present a general strategy for generating reactive machine learning potentials to model chemical processes in solution. Our approach combines active learning with descriptor-based selectors and automation, enabling the construction of data-efficient training sets that span the relevant chemical and conformational space. We apply this strategy to investigate a Diels-Alder reaction in water and methanol. The generated machine learning potentials enable us to obtain reaction rates that are in agreement with experimental data and analyse the influence of these solvents on the reaction mechanism. Our strategy offers an efficient approach to the routine modelling of chemical reactions in solution, opening up avenues for studying complex chemical processes in an efficient manner.

Bulk graphene-based composites with artificial nacre-like laminated structure: Microstructure and mechanical properties

In this study, the bulk Cu/reduced graphene oxide (Cu/rGO) composites featuring an artificial nacre-like laminated structure were successfully fabricated using spark plasma sintering (SPS), and the microstructure and mechanical properties of the resulting composites were investigated. The Cu/rGO composites demonstrated a distinct laminated structure, and their relative densities increase with Cu addition. Moreover, the presence of trace amounts of in-situ interfacial reaction products (CuO and CuO2,) were observed to enhance the adhesive strength at the Cu-rGO interface. Mechanical testing of the composites showed notable improvements in both compressive strength and ductility compared to a bulk monolithic rGO sample. Specifically, the bulk rGO composites with a 35.05 wt% addition of Cu displayed an enhancement of ∼67 % in compressive strength and ∼19 % in ductility relative to the pure rGO sample. These improvements are attributed to synergetic strengthening and toughening mechanisms within the rGO composites. The enhanced strength and ductility of the Cu/rGO composites significantly boost their wear resistance. This research not only demonstrates the effectiveness of incorporating Cu into rGO matrices but also suggests a promising avenue for the development of novel bulk rGO composites with engineered laminated structures.

Synergistic catalytic effect of titanium and iron incorporated to spherical MCM-41 in selective catalytic oxidation of diphenyl sulphide with H2O2

Spherical mesoporous silicas of MCM-41 type modified with titanium, iron or both these metals were prepared by co-condensation method and tested in the role of catalysts for selective oxidation of diphenyl sulphide with H2O2 to diphenyl sulphoxide and diphenyl sulphone. The monometallic catalysts containing titanium or iron were found to be active catalysts of diphenyl sulphide mainly to diphenyl sulphoxide. A very significant increase in catalytic activity was observed for the bimetallic samples, containing both titanium and iron. Moreover, in the case of bimetallic catalysts with higher titanium loading, diphenyl sulphone is a dominating reaction product. The increased activity of the bimetallic catalysts has been related to the synergistic operation of titanium and iron in conversion of hydrogen peroxide into reactive species, which in the next step oxidise diphenyl sulphoxide.

The potential of catalyst based on palm leaves in biodiesel production as part of palm oil life cycle assesment

The advantages offered by biomass-based heterogeneous catalysts, such as being easily separated from reaction products, being used many times, having low production costs, and being widely available in nature. One of the heterogeneous catalysts that can be used is a sodium silicate catalyst, especially one obtained by impregnating Na metal on a SiO2 matrix derived from biomass ash. In this study, palm leaves have the potential to be used as raw material for the SiO2 matrix because their utilization has yet to be optimal. This research aims to synthesize, characterize, and apply a sodium silicate catalyst based on palm leaves ash in the production of biodiesel from Refined, Bleached, Deodorized, Palm Oil (RBDPO). SiO2 was obtained by calcining palm leaves at a temperature of 700 °C for 3 hours, followed by washing using 1 N HCl solution. In this research, variations in the mole ratio of NaOH: SiO2 were carried out in the synthesis of sodium silicate, namely 1:1, 1.5:1, 2:1, and 2.5:1. This research also evaluates the reusability of the sodium silicate catalyst and the effect of washing using methanol on the biodiesel yield produced. The best sodium silicate catalyst was obtained at a NaOH: SiO2 molar ratio of 1.5:1, with a biodiesel yield of 74.485 % and an ester content of 97.293 %. SEM analysis shows the presence of a porous structure on the catalyst. The existence of the Si-O-Na group has been confirmed using FTIR. BET-BJH analysis has confirmed the presence of a mesoporous structure in the catalyst, with a surface area of 6.4343 m2/g and a pore size of 5.3127 nm. The resulting sodium silicate catalyst can be used up to three times, with a yield of 62.388 %. Catalyst regeneration using methanol is capable of producing biodiesel with a yield of 45.198 %

Mechanisms of alkali-activation of limestone: Reaction kinetics and influence of drying parameters

This paper focuses on the study of the reaction between limestone and sodium hydroxide solution. This reaction is used to produce alkali-activated mortars after curing and in the presence of unreactive siliceous sand. The kinetics of this reaction is investigated by semi-adiabatic calorimetry experiments. The formulation parameters are fixed but the curing parameters are tested: temperature (38 and 45°C) and time of drying (14, 25, 27 and 28 days). Their impact on reaction products (identified by FTIR and thermal analysis), on microstructure (SEM observations and porosity measurements) and on mechanical strength (flexural and compressive tests) are determined. The reaction was fast and a temperature drying was required to obtain stabilized hydration products in mortars. The products of the alkali-activation of limestone are double sodium/calcium carbonate (mainly pirssonite and with specific conditions of curing gaylussite) and calcium hydroxide. The microstructure and the proportions of reaction products, impacted by drying conditions, influence the mechanical strength of mortars. With an appropriate time (25 days) and temperature of drying (45°C), the compressive strength reached, after 28 days, almost 25 MPa.

Strength and durability characteristics of geopolymer treated pond ash as pavement material

This study evaluated the strength and durability characteristics of pond ash (PA) treated with geopolymer (3%, 6%, 9%, 12%, and 15%, by dry weight of PA) and compared them with Portland cement and hydrated lime stabilizations at same additive contents. Unconfined compressive strength of specimens was evaluated at curing durations of 1, 3, 7, 28, and 90 days. The durability of 28-day cured stabilised specimens against wet-dry cycles, freeze-thaw cycles, water slaking cycles, water immersion, capillary action, and dispersion was assessed. Geopolymer-stabilized PA achieved higher strength and durability than cement and lime-stabilised PA. It is due to the formation of a dense microstructure with significant reaction products. PA stabilised with 3% geopolymer and 15% cement satisfies the strength properties of the cementitious subbase in flexible pavements. Whereas, 6% geopolymer content fulfils the requirements of the cementitious base in flexible pavements and the cementitious subbase in rigid pavements as per IRC: 37-2018 and IRC: 59-2015, respectively.

Characterization of washing aggregate sludge waste as a novel supplementary cementitious material: Experimental study and life cycle assessment

Washing aggregate sludge (WAS), a waste collected from aggregate quarries, is examined for its application as a partial substitute of ordinary portland cement (OPC). The raw WAS initially dried, ground, and then subjected to 700 °C and 900 °C. In this study, various paste and mortar mixtures were produced to investigate the pozzolanic property and environmental impacts of raw WAS and treated WAS at a selected temperature of 700 °C. The pozzolanic activity of both raw and treated WAS at 700 °C was verified using several tests, including X-ray diffraction (XRD), Frattini test, strength-based evaluation, and thermal analysis. The calcium-silicate-hydrate (C–S–H), portlandite (Ca(OH)2), calcium silicates (C2S and C3S), and calcite (CaCO3) were identified as major reaction products indicating the participation of raw or treated WAS. While the reduced [CaO] concentration and location below the solubility curve confirmed the pozzolanic activity of both powders, the compressive strengths of blended mortars were also found greater than 75% compared to the reference mortar at all testing ages. Treated WAS demonstrated higher pozzolanic activity than raw WAS due to the reduced formation of Ca(OH)2 revealed by thermal and kinetic analysis at different time periods. Life cycle assessment resulted in the reduced CO2 emissions by the blended mortars containing either raw or treated WAS, which suggest their promising mechanical and environmental benefits.