Aggregation Properties Research Articles

Old residual mortar as a quality indicator of recycled brick aggregate

Old residual mortar (RM) on recycled aggregate surfaces is a major factor contributing to its lower quality. The present study aims to quantify the effect of old mortar on the properties of recycled brick aggregates (RBA) and recycled concrete (ReC) made with them. The process involves collecting and crushing discarded concrete blocks from seven sources to create recycled brick aggregates. A chemical-thermal combined process removes old mortar, and with varying RM contents, the aggregate properties are determined. C-25-grade concrete specimens are prepared using RBA with different RM content and tested for workability, compressive strength, splitting tensile strength, flexural strength, water absorption, bulk density, and voids in hardened concrete. Regression models expressing the change in properties with RM content are presented. The study reveals that the quality of RBA and concrete worsens with increasing RM, with a 20% RM value being considered a limiting value to maintain minimal variation in properties. The regression models suggest that every 10% increase in RM may result in an 11% increase in water absorption of RBA, an 8% increase in aggregate crushing value (ACV), a 3.6% increase in Los Angeles (LA) value, a 10% loss in compressive strength of ReC, a 7% loss in tensile strength, and a 9% loss in flexural strength, approximately. The developed models may be used to predict the expected quality of RBA and ReC based on their attached old RM, which would be helpful in deciding their usage for different applications.

Influence investigation of morphological and distributional properties of surficial aggregates on skid resistance of asphalt pavement

Skid resistance of the asphalt pavement is greatly influenced by the morphology and spatial distribution of surficial aggregates on the pavement. To clarify the correlation between them, this study accurately detects and segments the mesh of aggregates in the pavement model reconstructed by the laser scanner. Subsequently, three morphological indices (the peak height, cross-section form, and root-mean-square gradient of an aggregate) and two distributional indices (the aggregate spacing, and aggregate distribution dispersity) were calculated. Simultaneously, British pendulum number was also measured to represent the skid resistance of the pavement. At last, the correlation between the British pendulum number and five indices of surficial aggregates of the pavement was obtained using the grey relation method. Especially, the mesh segmentation algorithm developed was enhanced in splitting adhesive mesh of adjacent aggregates and restoring incorrectly splitted mesh of aggregates to improve the accuracy and robustness of the algorithm. Six regions on the surface of two rut specimens under SMA-16 and GAC-16 gradations were selected to analyze the correlation between British pendulum number and the five indices. Results indicate that the cross-section form influences the skid resistance of the pavement most, followed by the aggregate spacing, aggregate distribution dispersity, aggregate peak height, and aggregate RMS gradient. This facilitates the potential directions to improve the skid resistance by optimizing the highly relevant indices in future.

Development of cold-bond artificial aggregate with excavated soil and alkali-activated slag

This study investigates the feasibility of utilising high-volume ES along with alkali-activated slag to manufacture cold-bond artificial aggregates. The effects of slag content, alkali dosage, and silicate modulus of the alkaline activator on the properties of the alkali-activated aggregate (AAA) were evaluated, including aggregate size distribution, apparent density, water absorption, and crushing strength. Subsequently, microstructural and statistical analyses were conducted to elucidate the underlying mechanisms. The results indicate that higher GGBS content and alkali dosage significantly enhance the engineering properties of AAA. Specifically, increasing the GGBS content from 10% to 40% raises the 28-day crushing strength from 1.71MPa to 8.98MPa and reduces the 24-hour water absorption from 15.9% to 9.5%. Similarly, increasing the alkali dosage from 4% to 8% boosts the 28-day crushing strength of AAA by 26.0% and reduces the 24-hour water absorption by 25.2%. The variation in silicate modulus has a marginal impact on the properties of AAA, with an optimal value of 1.0. The improvement in the AAA properties relies heavily on the reaction products and pore structure, showing high correlation coefficients ranging from 81.039% to 94.306%. Particularly, pores between 100 and 1000nm could predominantly affect these properties. Overall, this study presents a novel method for producing eco-friendly AAA by stabilising ES with alkali-activated slag, promoting the high-value utilisation of ES.

Properties of waste brick powder-based artificial fine aggregate and its application in concrete

Shortage of natural fine aggregates (NFAs) and large amounts of construction solid waste have become prominent issues in the construction industry. To deal with these problems, this study aims to utilize waste brick power (WBP) to develop WBP-based artificial fine aggregates (AFAs) by high-speed stirring method. In this study, the effects of different proportions of WBP, waste concrete powder (WCP), fly ash (FA), slag powder (SP), calcium hydroxide (Ca(OH)2) and ordinary Portland cement (OPC) on the mechanism, physical and microscopic properties of AFAs were analyzed. Besides, the mechanical properties of concrete using COM AFAs (i.e. the AFAs containing all aforementioned powders) were measured. The results showed the single particle compressive strengths (SPCSs) of WBP-based AFAs increased with the increasing OPC, SP, FA or Ca(OH)2 contents. The WCP contents had a slight effect on the SPCSs. Compared with the NFAs and recycled fine aggregates (RFAs), the apparent density, the loose and close bulk density of COM AFAs reduced, and the loose and close bulk voidages increased. However, the water absorptions of COM AFAs were larger than NFAs, but less than RFAs. It was due to the generation of hydration products during the preparation of AFAs that filled the pores of AFAs. In addition, it was found that the cubic compressive strength and splitting tensile strength of COM AFA concrete using COM AFAs with 20% OPC content were larger than those of concrete using NFAs and RFAs and COM AFAs with 10% OPC content.

Myosin supramolecular self-assembly: The crucial precursor that manipulates the covalent aggregation, emulsification and rheological properties of myosin

The transformation of molecular conformation and self-assembly properties of myosin during the heating process at different ionic strengths (0.2 M, 0.4 M and 0.6 M NaCl) and its effect on rheological behavior and emulsification properties were investigated. Under incubation temperatures between 40 °C and 50 °C, myosin underwent a supramolecular self-assembly stage dominated by noncovalent forces (hydrogen bonding, ionic bonding and hydrophobic interactions). Higher ionic strength facilitated molecular rearrangement through enhanced swelling of myosin heads and head-to-head assemblies, which contributed to enhanced ordering and homogeneity of myosin covalent aggregates (above 60 °C) and manifested itself macroscopically as enhanced gel viscoelasticity and emulsion stability. In contrast, at lower ionic strength, the tail-to-tail assemblies of myosin led to the preferential formation of covalent cross-links in the tails, which resulted in the inability of molecular rearrangement and the formation of disordered aggregates and finally led to the deterioration of the gel and the destabilization of the emulsion. In conclusion, the supramolecular self-assembly behavior of myosin, as an intermediate process in myosin’s sol–gel transition, is crucial for the orderliness of myosin assemblies, gel network strengthening, and emulsion stability. The obtained insight provides a reference for the precise implementation of quality improvement strategies for meat products.

Prediction of cement-stabilized recycled concrete aggregate properties by CNN-LSTM incorporating attention mechanism

Cement-stabilized recycled concrete aggregate (CSRCA), as an eco-friendly and cost-effective building material, has its mechanical properties and fatigue resistance influenced by multiple factors. Machine learning-based prediction methods offer a new solution for the rapid assessment of CSRCA performance. To efficiently and accurately predict the mechanical properties and fatigue resistance of CSRCA, this study proposes a machine learning-based CSRCA performance prediction model. By collecting data on various influencing factors such as mix ratios, aggregate characteristics, and compaction, and combining convolutional neural networks (CNN) with long short-term memory networks (LSTM), the study introduces an attention mechanism (ATT) to optimize feature weighting, thus constructing a CNN-LSTM-ATT prediction model. Additionally, Pearson correlation analysis and random forest algorithms are used to investigate the key influencing factors and feature importance of CSRCA's mechanical and fatigue performance. The Shapley Additive Explanation (SHAP) is employed to enhance the model's interpretability. The results indicated that each input parameter exhibited a significant nonlinear relationship with both compressive strength and fatigue life. Specifically, increasing cement dosage, degree of compaction, and 19mm sieve passing rate contributed positively to the mechanical properties and fatigue life of CSRCA. Conversely, the recycled aggregate crushing value had a significant negative impact on compressive strength but minimal effect on fatigue life. Notably, recycled aggregate dosage demonstrated opposing effects on compressive strength and fatigue life. The prediction accuracy of the CNN-LSTM-ATT model, incorporating the attention mechanism, surpassed that of the conventional CNN-LSTM model, enhancing the accuracy, robustness, and generalization ability of the prediction framework. The prediction metrics for compressive strength were R² = 0.993, MAE = 0.101, and RMSE = 0.144, while those for fatigue life were R² = 0.994, MAE = 55.05, and RMSE = 73.43, the prediction ability is significantly higher than other prediction models of the same type. Consequently, the CNN-LSTM-ATT model provides a scientific foundation for the performance prediction and proportioning design of CSRCA, holding significant implications for engineering practice.

Effect of Gypsum, Cover Crop, and Crop Rotation on Bulk Density and Aggregate Properties of Soils

ABSTRACT Soybean production, worldwide, typically involves full tillage resulting in much less biomass than other crops, leading to decreased soil organic matter and increased soil degradation. The goal of this study was to evaluate the potential benefits of an innovative management system that includes the combinations of no-till, crop rotation, cover crop, and gypsum application on continuous soybean production. The response of soil physical properties, i.e. bulk density and water-stable aggregates, was evaluated across a range of soil types and climatic conditions. Treatments consisted of comparing (1) continuous soybean to a soybean-corn and corn-soybean rotation, (2) cereal rye [Secale cereale (L.)] cover crop to no cover crop, and (3) gypsum surface‐applied at 0, 1.1, and 2.2 Mg ha−1. The study was replicated at four different sites in the United States, including Shorter (AL), Farmland (IN), Hoytville (OH), and Piketon (OH). At the end of the 5-year study, soil bulk density and aggregate stability were determined. Soil bulk density and water-stable aggregates were unaffected by gypsum addition regardless of the location. Including cereal rye as a winter cover increased soil aggregation and bulk density at the Hoytville location only. Rotating the soybeans with corn (compared to continuous soybeans) resulted in soil aggregation and bulk density improvements at all research locations. Results indicated that soybean production that included crop rotation into management system improved soil aggregate stability, whereas cover crop benefits were less effective and amending the soil with gypsum did not significantly affect these soil properties.

Porous aggregate developed with the use of coal-containing clays of the Angren field

Relevance. One of the ways to solve the issues of resource and energy conservation is the production and use of porous aggregates. Porous aggregates allow obtaining effective lightweight concrete for thermal insulation, wall panels, monolithic walls and other load-bearing structures, contribute to the increase of energy efficiency, improvement of thermal insulation, reliability, increase of fire resistance, frost resistance and seismic resistance of buildings, reduction of their weight. Therefore, in the production of porous aggregates, the primary task is the use of industrial waste and products of their processing. Solving these problems leads not only to saving valuable natural resources, but also to solution of environmental problems. Aim. Development of compositions and study of properties of porous aggregate based on bentonite clay of Navbakhar deposit and coal-containing clay of Angren brown coal deposit. Object. Coal-containing clay of Angren brown coal deposit, bentonite clay of Navbakhar deposit and artificial porous aggregate based on them. Methods. Chemical, energy-dispersive X-ray, X-ray phase and infrared spectroscopic analysis, scanning electron microscopy, mathematical modeling, etc. Results. The authors have determined chemical and mineralogical compositions of the clays used. Using the mathematical modeling method they developed the regression equations describing the effects of the amount of bentonite clay in the batch, firing temperature and isothermal holding time on the bulk density and water absorption of the porous aggregates. The resulting porous aggregates with a bulk density of 395 to 690 kg/m3 have a compressive strength in a cylinder of 2.74 to 6.46 MPa, respectively. It was found that the aggregates obtained meet the requirements of regulatory documents.

Durability of concrete containing carbonated recycled aggregates: A comprehensive review

The utilisation of carbonated recycled aggregates in concrete has been increasingly considered as an effective strategy for CO2 sequestration in the built environment and enhancement of concrete sustainability. Following up a pervious review on the role of carbonated recycled concrete aggregates in the mechanical properties of concrete, this paper presents a comprehensive review on the effects of carbonation treatment on the chemical compositions and physical properties of recycled concrete aggregates, as well as the role of carbonated recycled concrete aggregates in microstructure and durability-related properties including volume deformation, transport properties, chemical resistance, freeze-thaw resistance and fire resistance of concrete. A special focus is placed on the relationship between microstructure and durability-related properties of carbonated recycled aggregate concrete considering the effects of pre-treatment method, replacement level, curing age, water-to-binder ratio and quality of the original aggregates. The insights into the deterioration mechanism and strategies for improving the durability of carbonated recycled aggregate concrete are provided. This review summarises the recent advances in the field, followed by a discussion on the remaining challenges and opportunities for future research.

Synthesis of Highly Stable Coumarin-Based Fluorescent Dye, Its Photophysical Properties and Stability in PLA Film and Application Towards Sensing Toxic Ions.

New materials were designed and synthesized by introducing electron donor and acceptor groups using coumarin as the basic unit. In addition, two more materials with similar structures were synthesized for the comparison of their optical properties and stability. The solvent effect and the photo physical aggregation properties of aggregation caused quenching (ACQ) in the ratio of water and DMF were also investigated. In addition, we checked the detection ability for anions, and the optical properties of the materials at different pH were also investigated. The photo stability of these synthesized materials was studied, and interesting results were obtained. Based on these synthesized materials, we produced films by introducing color materials into PLA films. PLA film is characterized by the absence of plastic waste due to carbon reduction and biodegradation effects from using biomass instead of fossil fuels as raw materials, but it has the disadvantage of low light stability. By introducing high-photo stability pigment materials, the photo stability of the film can be corrected, and UV protection can be provided. The UV absorbance and fluorescence intensity of the film with the dye materials were checked, and the mechanical properties and thermal stability of the film changed when the coloring material was introduced compared to the conventional PLA film.

Assessment of cationic amphiphile-biopolymer interactions: Effects of organic compounds and temperature on association phenomena

The present study reveals the micellization nature of cetyltrimethylammonium bromide (CTAB) in aqueous solutions of sodium alginate (SA) with short-chain alcohols (containing 1–3 carbon number) and glycerol using the conductometric method at temperatures from 305.55 to 325.55 K with 5 K interval. The aggregation property has been characterized by assessing critical micelle concentration (CMC) from conductivity (κ) versus surfactant concentration plots. The micellar variables such as CMC and the extent of counterion binding (β) demonstrate the dependency on the variation in solvent categories, composition of the solvent mixture, and working temperatures. For the CTAB + SA (0.01 %, w/w) mixed system at 310.55 K, the increased CMC values were acquired with increasing quantity of alcohols and glycerol introduced. The CMC values showed a rising trend with the escalation of working temperature. The negative Gibbs free energy (ΔGm0) values were attained for the CTAB + SA system in all investigating solvents, which stated the spontaneous occurrence of aggregation of the employed system. In aqueous alcohols media, the enthalpy changes (∆Hmo) were attained as positive and negative at lower and elevated investigated temperatures respectively; while in aqueous glycerol environment, the ∆Hmo values were acquired to be all negative at inspected temperatures. The entropy changes (∆Smo) were realized to be positive for the investigated cases. The compensation temperature (Tc) values have been achieved to be in the series of 241.91 K to 318.75 K which showed a good analogy to the literature stated data for the micellization of amphiphiles. The attained knowledge from the present investigation might help in improving the formulations in industries including pharmaceuticals, foods, and cosmetics.

Numerical FE Three-phasic Simulation to Predict the Effect of Air Voids on the Dynamic Modulus of Bituminous Composites

In this study, the mechanical performance of bituminous composites was predicted using an upscaling methodology that integrated both finite element analysis and analytical modeling. The FE approach was employed to incorporate intricate geometries and material characteristics. The dynamic modulus of the matrix and the elastic properties of aggregates served as inputs for the numerical models at various scales. This approach considers the distinctive attributes of the granular framework at each level. Furthermore, the investigation involved the influence of air void proportions on the composite's modulus. The numerical models encompassed the random incorporation of air voids within the matrix at varying levels. Notably, it was observed that at low frequencies air voids reduced the dynamic modulus of asphalt more than at high frequencies due to its effect on viscoelastic nature of the bituminous composite. Moreover, heightened temperatures intensified the impact of air void on the dynamic modulus of the asphalt mixture.

A Discrete Four‐Stranded β‐Sheet through Catenation of M2L2 Metal–Peptide Rings

AbstractMethods for precisely constructing a β‐sheet assembly with number‐defined strands in solution remains quite limited due to its intense aggregation property. Here, we report the precise construction of a four‐stranded anti‐parallel β‐sheet by utilizing a non‐covalent approach. This was achieved by folding and assembly of Ag+ and a pentapeptide (1) with the Ala‐D3pa‐Gly‐3pa‐Val (3pa: β‐(3‐pyridyl)‐alanine) sequence, which was designed to form an interlocking Ag2(1)2 ring through metal cross‐linking of the side chains. NMR analyses and X‐ray crystallographic studies characterized the structure of the discrete β‐sheet assembly as well as the remarkable structural selectivity in terms of strands’ number, orientation and the sheet type.

Tuning molecular aggregation to enhance photovoltaic performance of polymers by isomerizing benzodithiophene moiety

Benzo[1,2-b:4,5-b']dithiophene derivatives (BDT) have been extensively utilized as electron-donating (D) units for the synthesis of polymer donor materials. However, its isomers, benzo[2,1-b:3,4-b']dithiophene derivatives (iBDT), are rarely employed for this application. In this research, three polymer donors, namely PTz-BDT, PTz-iBDT-L, and PTz-iBDT-H, were designed and synthesized using BDT and iBDT as the D moieties, respectively. Notably, compared to PTz-BDT, the iBDT-based polymers exhibit superior solubility and more favorable aggregation properties. When combined with the non-fullerene acceptor Y6, the iBDT-based polymers exhibit a more advantageous phase morphology, tighter packing, higher charge mobilities, more balanced charge transport, and less charge recombination in the devices. Consequently, the power conversion efficiency (PCE) of the PTz-iBDT-H:Y6 PSC reaches 11.04 %, significantly surpassing those of the PSCs based on PTz-BDT (7.15 %) and the iBDT-based polymers reported in literature. This study introduces an effective approach to enhance the performance of polymeric donors by isomerizing its backbone and synchronously increasing its molecular weight.

A Review of Rheological Properties of Steel Fiber Reinforced Concrete

The rheological properties of steel fiber reinforced concrete have a significant impact on engineering quality, and experimental characterization of the rheological properties of steel fiber reinforced concrete has significant engineering significance and scientific research value. By reviewing relevant literature both domestically and internationally, the article compares and analyzes the construction characteristics and applicable scope of commonly used concrete rheometers, and analyzes the influence of factors such as water cement ratio, mineral admixtures, aggregate properties, steel fiber properties, and additives on the rheological performance test results. The results show that there are significant differences in the test results using different rheometers, and the degree of influence of different factors on the rheological properties of steel fiber reinforced concrete is also different. This can provide reference for the selection of rheological performance testing methods and parameter control of steel fiber reinforced concrete.

Completely Fused Non‐Fullerene Acceptor Enables Efficient Postprocessing‐Free Organic Photovoltaics Cells

AbstractThe photovoltaic performance of organic photovoltaic (OPV) cells can be significantly improved by regulating the aggregation structure and film formation kinetics of the constituent materials. However, many regulation strategies, including the use of additives and annealing, require complex fabrication processes and additional investments, which poses challenges for the industrialization of OPV cells. In this work, a completely fused non‐fullerene acceptor, GS‐20 is designed and synthesized, with strong aggregation properties. The incorporation of GS‐20 as a third component into the PBQx‐TF:eC9‐2Cl‐based cell accelerates aggregation of eC9‐2Cl and improves molecular stacking by promoting film deposition. The as‐cast ternary OPV cells fabricated without any post‐treatments exhibited a high VOC of 0.890 V and a maximum PCE of 19.0%. Moreover, a postprocessing‐free OPV module is fabricated using the blade coating method and obtains a satisfactory PCE of 13.5%, indicating excellent feasibility for large‐scale preparation. This work realizes an efficient postprocessing‐free OPV cell through molecular design and ternary strategy, facilitating the industrialization of OPV technology.

Regiospecific Incorporation of Fluorine Atoms in Polythiophene Derivatives for Efficient Organic Solar Cells.

Derivatives of polythiophene (PT) have garnered considerable attention in organic solar cells (OSCs) because of their relatively uncomplicated molecular structures and cost-effective synthesis. Herein, we have developed two regioisomeric fluorinated PT donors, PEI3T-FITVT and PEI3T-FOTVT, to realize efficient OSCs. PEI3T-FITVT and PEI3T-FOTVT are strategically designed with different fluorine atom arrangements on thiophene-vinyl-thiophene (TVT) units. Notably, PEI3T-FOTVT possesses enhanced backbone planarity induced by F···S noncovalent interactions between two constituent building blocks. Consequently, PEI3T-FOTVT with the higher aggregation and crystalline properties leads to a 2.5-fold increase in hole mobility over PEI3T-FITVT (from 1.4 × 10-4 to 3.6 × 10-4 cm2 V-1 s-1). Furthermore, PEI3T-FOTVT exhibits higher domain purity than PEI3T-FITVT, leading to faster charge transport and reduced charge recombination in OSC devices. These characteristics lead to a higher power conversion efficiency of 14.4% for PEI3T-FOTVT-based OSCs, compared to 12.9% for PEI3T-FITVT-based OSCs.

Mean-Field-Type Transformers

In this article, we present the mathematical foundations of generative machine intelligence and link them with mean-field-type game theory. The key interaction mechanism is self-attention, which exhibits aggregative properties similar to those found in mean-field-type game theory. It is not necessary to have an infinite number of neural units to handle mean-field-type terms. For instance, the variance reduction in error within generative machine intelligence is a mean-field-type problem and does not involve an infinite number of decision-makers. Based on this insight, we construct mean-field-type transformers that operate on data that are not necessarily identically distributed and evolve over several layers using mean-field-type transition kernels. We demonstrate that the outcomes of these mean-field-type transformers correspond exactly to the mean-field-type equilibria of a hierarchical mean-field-type game. Due to the non-convexity of the operators’ composition, gradient-based methods alone are insufficient. To distinguish a global minimum from other extrema—such as local minima, local maxima, global maxima, and saddle points—alternative methods that exploit hidden convexities of anti-derivatives of activation functions are required. We also discuss the integration of blockchain technologies into machine intelligence, facilitating an incentive design loop for all contributors and enabling blockchain token economics for each system participant. This feature is especially relevant to ensuring the integrity of factual data, legislative information, medical records, and scientifically published references that should remain immutable after the application of generative machine intelligence.

Study of coarse and fine natural aggregates at high temperature in Algeria

Under high temperature, concrete undergoes changes which occurred in the hardened cement past and aggregates. These changes modified the mechanical and physical properties of concrete. The main objective of this study is to observe and identify the influence of high temperature on the physical properties of different nature of aggregates used to cast concrete. Four types of aggregates were studied in this research, siliceous sand (SS), calcareous sand (CS), white calcareous aggregates (WCA) and gray calcareous aggregates (GCA). These aggregates were subjected to different temperatures, from 100°C to 900°C. The mass loss, absorption coefficient, water porosity and density were determined before and after the exposure to the high temperatures. The results show that gray calcareous aggregates (GCA) suffered more deterioration than the other types of aggregates after the high temperature exposures. The results presented in this paper allow improving the knowledge of aggregate’s deterioration phenomena and the evolutions of physical properties of these different aggregates can be used to explain the evolution of physical and mechanical properties of concretes.

Effect of CTAB on the aggregation properties of Congo Red organized in layer-by-layer electrostatic self-assembled film: a spectroscopic and Atomic force microscopy study

Effect of CTAB on the aggregation properties of Congo Red organized in layer-by-layer electrostatic self-assembled film: a spectroscopic and Atomic force microscopy study