Types Of Aggregates Research Articles

Effect of treatment types of recycled concrete aggregates on the properties of concrete

Reusing waste materials such as construction and demolition waste is an environmentally significant task. This article aims to improve the quality of recycled aggregates after the demolition of concrete structures. Two methods, mechanical cleaning and impregnation, were explored to enhance the quality of coarse aggregates. The findings indicate that mechanical cleaning is more effective than soaking in a sodium silicate solution. The compressive strength of concrete made with mechanically cleaned recycled aggregates was 2.3 times greater than that of concrete made with untreated rubble. Concrete with impregnated rubble had a compressive strength 1.1 times greater than that of concrete with untreated aggregates. Infrared spectroscopy was used to study the microstructure, revealing that the type of treatment does not influence the quantity of portlandite and ettringite in hydrated cement. However, the treatment of recycled aggregates alters the interaction in the gel portion of cement hydration products. Concrete with aggregates treated by sodium silicate has more aluminate components. Additionally, there is a shift of the bands assigned to Si-O stretching to higher wave numbers (from 995 cm–1 to 1088 cm–1), which can be attributed to the formation of calcium-silicate-hydrate gel with a lower calcium/silicon ratio.

The effects of herding and dispersal behaviour on the evolution of cooperation on complete networks

Evolutionary graph theory has considerably advanced the process of modelling the evolution of structured populations, which models the interactions between individuals as pairwise contests. In recent years, these classical evolution models have been extended to incorporate more realistic features, e.g. multiplayer games. A recent series of papers have developed a new evolutionary framework including structure, multiplayer interactions, evolutionary dynamics, and movement. However, so far, the developed models have mainly considered independent movement without coordinated behaviour. Although the theory underlying the framework has been developed and explored in various directions, several movement mechanisms have been produced which characterise coordinated movement, for example, herding. By embedding these newly constructed movement distributions, within the evolutionary setting of the framework, we demonstrate that certain levels of aggregation and dispersal benefit specific types of individuals. Moreover, by extending existing parameters within the framework, we are not only able to develop a general process of embedding any of the considered movement distributions into the evolutionary setting on complete graphs but also analytically produce the probability of fixation of a mutant on a complete N-sized network, for the multiplayer Public Goods and Hawk–Dove games. Also, by applying weak selection methods, we extended existing previous analyses on the pairwise Hawk–Dove Game to encompass the multiplayer version considered in this paper. By producing neutrality and equilibrium conditions, we show that hawks generally do worse in our models due to the multiplayer nature of the interactions.

The middle domain of Hsp104 can ensure substrates are functional after processing.

Molecular chaperones play a central role in protein disaggregation. However, the molecular determinants that regulate this process are poorly understood. Hsp104 is an AAA+ ATPase that disassembles stress granules and amyloids in yeast through collaboration with Hsp70 and Hsp40. In vitro studies show that Hsp104 processes different types of protein aggregates by partially translocating or threading polypeptides through the central pore of the hexamer. However, it is unclear how Hsp104 processing influences client protein function in vivo. The middle domain (MD) of Hsp104 regulates ATPase activity and interactions with Hsp70. Here, we tested how MD variants, Hsp104A503S and Hsp104A503V, process different protein aggregates. We establish that engineered MD variants fail to resolve stress granules but retain prion fragmentation activity required for prion propagation. Using the Sup35 prion protein, our in vitro and in vivo data indicate that the MD variants can disassemble Sup35 aggregates, but the disaggregated protein has reduced GTPase and translation termination activity. These results suggest that the middle domain can play a role in sensing certain substrates and plays an essential role in ensuring the processed protein is functional.

Axial compression behaviour of square steel tubes encased by and filled with high-strength recycled aggregate concrete

The axial compression behaviour of square steel tube (SST) columns encased with recycled aggregate concrete (RAC) and filled with RAC (RAC-encased RACFSST) columns was investigated. Using high-strength concrete, five specimens were tested under axial compression until failure. The experimental parameters included the coarse aggregate type, stirrup spacing, wall thickness of the SST and the existence of cross-tie bars in the SST. The failure mode, load–displacement curves, load–strain curves and ductility of the composite columns were obtained. The impacts of the various parameters on the mechanical performance of the RAC-encased RACFSST columns were evaluated. The failure modes of the composite columns were comparable. The inclusion of RAC enhanced the load-bearing capacity (LBC) of the column, but negatively affects its ductility and deformation capacity. Increasing the wall thickness of the SST and reducing the stirrup spacing significantly improved the axial compressive performance of the columns, as mainly reflected in the axial compressive capacity and ductility, respectively. Cross-tie bars inside the SST improved the LBC and deformation capacity. The axial bearing capacities of the columns and those in other studies were determined using existing codes. The computed results were very consistent with the experimental data.

Valorization of phosphate mine waste rock as alternative aggregates for high-performance concrete

Natural aggregate quarrying significantly impacts the environment while phosphate mine waste rock (PMWR) offers alternative aggregates for use in high-added value construction materials. This study was the first to investigate the application of three aggregate types from PMWR as a complete substitute to natural aggregate to produce high-performance concrete (HPC). For this aim, three coarse aggregate (CA) types: Flint (F), Phosflint (PF), and Dolomite (D) from PMWR in Morocco were selected and compared with a natural Reference CA (R). Two mixtures were tested: HPC-0.40 and HPC-0.36 with a w/c ratio equal to 0.40 and 0.36. D-HPC and PF-HPC achieved a slump exceeding 20 cm and a 28-d compressive strength (CS) equal to 55 MPa ± 5 MPa on average, similar to the R-HPC, while F-HPC did not meet the requirement for HPC (i.e. a 28-d CS superior to 55 MPa). Scanning electron microscope observations showed that D-HPC exhibited a very dense and indistinguishable interfacial transition zone (ITZ), while F-HPC showed a debonding of F-CA and a larger ITZ size which explain its lower CS. Life ycle assessment revealed a major positive environmental impact on ecosystem quality that reduced land occupation and land transformation by up to 32 %. A secondary evaluation of the valorization of PMWR as alternative fine aggregate (FA) in high-strength mortar (HSM) was investigated and showed that the 28-d CS is equal to 93 MPa for PF-HSM and equal to 81 MPa for D-HSM, superior to RS-HSM which is equal to 61 MPa. Dolomite and Phosflint FA offered a better alternative to natural River sand to overcome the ceiling effect. These findings encourage the construction sector to adopt a sustainable consumption of aggregates by using PMWR as alternative CAs and FAs to produce high-strength construction materials.

Evaluation of the interface shear strength of concrete containing treated and untreated reclaimed asphalt pavement aggregates

Concrete production significantly contributes to carbon emissions and depletes natural resources, promoting increased interest in substituting traditional materials with recycled alternatives. This shift necessitates a thorough examination of recycled materials’ performance in concrete applications. This study aims to provide a better understanding of the shear transfer behavior of concrete containing reclaimed asphalt pavement (RAP) aggregates. To mitigate the potential negative impact of RAP aggregates, mechanical treatment was applied. The effects of RAP inclusion and mechanical treatment on the shear transfer strength of reinforced concrete were investigated. A total of twenty-four push-off specimens were tested to investigate the effects of aggregate replacement and the clamping reinforcement ratio on specimen behavior. Digital image correlation (DIC) was employed to monitor the strains and displacements, allowing for detailed tracking of the interface slip, crack width development, and reinforcement strain. The findings revealed that replacing natural aggregates with RAP aggregates resulted in lower compressive strengths and lower ultimate push-off strengths of the resulting concrete at equivalent effective water-to-cement (w/c) ratios. Specimens with higher reinforcement ratios retained residual strengths up to 77 % of the ultimate strength, even at relatively large slip and crack widths. The clamping reinforcement ratio was identified as the key factor influencing the ultimate and residual strengths for both types of concrete. The experimental results were compared to the strengths calculated by the ACI, PCI, AASHTO, and CSA design equations to evaluate their applicability when different aggregate types are used.

The role of nanomaterials in enhancing adhesion properties between bitumen and aggregate particles

During production and construction stages of asphalt mixtures, rheology of bitumen must be set at certain level. In addition, the adhesion strength between bitumen and the aggregate particles should be high enough so that during the service life of the pavement, asphalt mixture can resist various distresses. There are different methods of controlling rheological properties of bitumen binders and increasing adhesion properties of asphalt mixtures. One of the most effective methods of modifying bitumen binders of asphalt mixtures is using nanomaterials. In this research, two bitumen types of 60/70 and 85/100 penetration grades, three aggregate types (limestone, siliceous, and granite) and four nanomaterials types (nanohydrated lime NHL, nanosilica NSiO2, nanolime NCaCO3, and nanoclay bentonite NClay) were used at 2, 4, and 6% of the weight of bitumen. X-ray diffraction and X-ray fluorescence tests were performed and, microscopic images of thin-sections of aggregates and asphalt mixtures were taken with the aim of evaluating petrographic properties of aggregates and bonding characteristics of the bitumen binders with aggregate particles. Physical and rheological properties of the nano-modified bitumen binders were evaluated, performing dynamic shear rheometer and rotational viscometer tests. Boiling water and pull-off tests were also carried out in order to investigate the coating ability and the adhesion strength that is performed at the aggregate surface in the interface with the bitumen binders. Digital images were analyzed using Digimizer Software. The results indicated that the addition of nanomaterials at certain optimal percentage affected viscosity and improved rheological behavior of the bitumen binders at different temperatures, and increased adhesion properties of the bitumen coating the aggregate particles. Comparing the effects of different aggregates, it resulted that the binder coating the limestone aggregates performed better than the siliceous and the granite aggregates. The adhesion and the rheological properties of the 60/70 pen bitumen that was modified with nanomaterials were better than those of the 85/100 pen bitumen. Nano-modified binders at 4% NHL, or 2% NSiO2, or 4% NCaCO3, or 4% NClay exhibited the best behavior. Among these, the nano-modified binders containing 4% NHL resulted in better performance. Finally, the correlation between the adhesion and rheological behavior was suitable for nano-modified binders in order to improve the asphalt mixes' performance in operation and construction stages.

Influence of Aggregate Types on the Long-Term Skid Resistance of Porous Asphalt Mixture Based on the Laboratory MMLS

Influence of Aggregate Types on the Long-Term Skid Resistance of Porous Asphalt Mixture Based on the Laboratory MMLS

High-modulus engineered cementitious composites: Design mechanism and performance characterization

Engineered cementitious composites features with high tensile performance while relatively weak compressive stiffness. This study endeavors to address the inherent trade-off between tensile properties and elastic modulus in conventional Engineered Cementitious Composites (ECC). Utilizing the distinctive characteristics of iron ore aggregates, known for their relatively stiff nature, smooth surface and rounded shape, an Iron Sand-based ECC (IS-ECC) emphasizing both high elastic modulus and ductility is formulated. Guided by micromechanical design theory and multiscale homogenization model, this study systematically explores the impacts of aggregate types, water-to-binder (w/b) ratios, sand-to-binder (s/b) ratios, and sand particle sizes on ECC properties. Compared with Quartz Sand-based ECC (QS-ECC), IS-ECC exhibits notably enhanced matrix fluidity and elastic modulus, reduced matrix toughness, and more robust strain-hardening behavior. The proposed three-level multiscale homogenization model accurately predicts the elastic modulus of ECC and provides insights into the underlying mechanism contributing to the enhanced elastic modulus of IS-ECC. With a resulting high elastic modulus of 33.3–48.6 GPa and superior tensile properties, IS-ECC holds promise for widespread applications in structural engineering.

Evaluation and Analysis of the Influence of Aggregate Type on Selected Concrete Properties

Evaluation and Analysis of the Influence of Aggregate Type on Selected Concrete Properties

Microstructural Evaluation of the Effects of Aggregate Type, Aging, and Additives on the Moisture Susceptibility of Binder–Aggregate Systems Using Chemical and Thermodynamic Approaches

Microstructural Evaluation of the Effects of Aggregate Type, Aging, and Additives on the Moisture Susceptibility of Binder–Aggregate Systems Using Chemical and Thermodynamic Approaches

Abrasion resistance of cement concretes on heavy aggregates

The paper presents the results of research on the influence of three different types of heavy aggregate (basalt, barite and magnetite) and natural gravel on the abrasion resistance of concrete. Concrete mixtures are designed to obtain maximum resistance to concrete abrasion. Concrete abrasion test was performed using a Böhme disc. The influence of compressive strength and physical and mechanical properties of the used aggregates on the abrasion resistance of the tested concretes was analyzed

Tension stiffening and cracking behaviors in glass fiber reinforced polymer bar enhanced precast recycled aggregate concrete specimen

Glass fiber reinforced polymer (GFRP) bar-enhanced precast recycled aggregate concrete (PRAC) elements combine PRAC’s environmental benefits with GFRP’s corrosion resistance, making them ideal for coastal urban infrastructure. However, in-depth research on the tensile stiffness and cracking behaviors of this composite is lacking. The significant mechanical differences between GFRP bars (low modulus, high strength) and PRAC, as compared to traditional materials, raise safety concerns for widespread use. This study investigates the short-term load capacity, deformation and cracking characteristics of GFRP bar-reinforced PRAC tensile specimens through tests and analyses. The tests examine how variables like water-to-binder ratio, coarse aggregate type, recycled aggregate (RA) content and mixing methods affect the specimens' mechanical responses. Theoretical analyses, using existing equations and a partial interaction model, clarify stress-strain relationships and crack propagation under applied loads, revealing: (a) As RA content increases, PRAC shows a moderate decrease in workability and mechanical performance. The strength variability in PRAC generally falls between that of natural aggregate concrete (NAC) and conventional recycled aggregate concrete (CRAC) using RAs from construction and demolition waste, being closer to NAC. Additionally, the strength conversion relation seen in NAC applies similarly to PRAC. (b) During tension at both ends of the specimen, PRAC's resistance decreases by 24.3 % compared to NAC but is still 20.3 % higher than CRAC. (c) The number of cracks in the PRAC specimen decreases with higher RA content and basalt fibers, while the ratio of stabilized load to cracking load increases. (d) The CEB-FIP standard offers more accurate predictions of the specimen’s composite stress-strain relation, while the Chinese code excels in predicting crack width. The partial interaction model effectively predicts the specimen’s load, deformation and crack characteristics by accounting for the behaviors and bonding of both PRAC and GFRP bars.

A method of developing ensemble classifiers for recognizing audio data of various nature

The work developed a method of building ensemble classifiers for recognizing audio data of various nature. The method is a tentative date and requires the following steps. In the first step, the input datasets are selected, which are transformed and divided into training and test samples, respectively. RAVDESS datasets are chosen for the task of audio emotion recognition, music genre recognition is performed on the GTZAN dataset. In the second step, the following seven classifiers were created and investigated as elements of ensemble classifiers: K Nearest Neighbors, Support Vector Machine, Random Forest, XGBoost, Multilayer Perceptron, Convolutional Neural Network and Long Short-term Memory. In the process of training elementary classifiers, the corresponding hyperparameters were adjusted using the Grid Search approach. In the third step, elementary classifiers were combined using the stacking ensemble method with such types of aggregation as soft voting, hard voting, soft voting using the GOMPERTZ function. All possible ensemble combinations starting with three elementary classifiers for recognizing audio emotions and music genres were tested. Therefore, the total number of ensembles studied in the work was 297. The research results for the problem of audio emotion classification showed that the accuracy of recognition according to the Accuracy metric of the best ensemble classifier is 8.1% higher than that of the best elementary classifier in its composition, which is based on on MLP, and according to the F1 metric, this indicator is 8% higher. For the task of recognizing music genres, the corresponding indicators are higher by 5.6 % and 5.2 %, respectively.

Spatial–Temporal Development Trends and Influencing Factors of Government Environmental Information Disclosure: Empirical Evidence Based on China’s Provincial Panel Data

Government environmental information disclosure (GEID) plays an important role in promoting the digital transformation of environmental governance, leading the concept of sustainable development, enhancing public oversight capacity, and promoting democratic decision-making governance. Using provincial panel data from China spanning from 2009 to 2021, we conducted spatial data exploratory analysis and used the dynamic spatial panel model to investigate the spatial–temporal development trends and influencing factors of GEID. The results show that (1) GEID in China exhibits significant spatial agglomeration characteristics, with an “H-H” (High-High aggregation type) agglomeration characteristic observed in three national strategic development regions: Yangtze River Delta, southeast coastal areas, and Beijing–Tianjin–Hebei region. (2) The spillover effect from the southeast coastal provinces gradually radiates to the northwest, resulting in an overall westward movement of GEID. (3) GEID exhibits a significant path-dependency feature in the temporal dimension and a “peer effect” in the spatial dimension. (4) Population size has the greatest impact on GEID. Population size, public participation, and the industrial and transportation sectors positively influence GEID improvement at the local level. However, they generate negative spillover effects to neighbouring provinces. Environmental status and the size of the Real Estate sector have no significant effect. Therefore, China should strengthen regional cooperation, narrow regional disparities, cultivate new quality productive forces, establish a government-led proactive disclosure mechanism under public supervision, and improve the level of GEID at the national level.

Effects of recycled sand and shell sand as sand replacement on the dynamic properties of seawater sea-sand recycled aggregate concrete

This study utilizes recycled sand and shell sand to replace sea-sand in seawater sea-sand recycled aggregate concrete (SSRAC) and explores their dynamic compressive properties. A total of 28 sets of specimens were designed, and their stress-strain curves under different strain rates were analyzed. The findings indicated that the dynamic increasing factor (DIF) of peak stress in SSRAC reached its peak at a 50% replacement ratio of recycled sand, exhibiting a 3.9% to 7.7% increase compared to a 0% replacement ratio. Conversely, there was an overall decreasing trend in the DIF when the replacement ratio of shell sand increased. Using recycled sand resulted in an average reduction of approximately 45% in the elastic modulus of the interfacial transition zone (ITZ), while the introduction of shell sand slightly increased that of it. Finally, considering strain rate effects, a dynamic compressive prediction model for SSRAC with different types of fine aggregates was established.

Properties of mortar according to substitution rate of ferro-nickel slag powder

This study analyzes the properties of cement mortar according to the substitution of fine ferro-nickel slag powder in various types of fine aggregate, with the aim of recycling industrial waste. When using a ferro-nickel slag powder as the admixture of cement mortar, it is determined that substitution rates of 30% and higher are unsuitable for use as mortar. In order to solve this problem, it is believed that it is necessary to explore means to improve the initial strength degradation that results when fine ferro-nickel slag powder is mixed. Furthermore, the differences in carbon dioxide reduction according to fine ferro-nickel slag powder substitution rates were found to be minimal, and it is thought that additional performance analysis is necessary.

Quantifying the operational flexibility and invocation costs of urban regional integrated energy systems for participation in demand response programs

As a typical aggregation platform, the regional integrated energy system (RIES) is required to pre-submit its flexibility for each time period when participating in demand response. However, existing studies fail to quantify the flexibility parameters necessary for RIES pre-reporting. Therefore, this paper introduces a flexibility quantification framework tailored for RIES engagement in demand response. The core principle of the framework is grounded in the RIES day-ahead dispatch model considering virtual energy storage, which transforms the flexibility quantification problem into dispatch optimization problems under baseline scenarios and flexibility invocation scenarios. In the flexibility invocation scenario, a control term is incorporated into the objective function to steer the system towards fulfilling flexibility requirements in the most economical strategy. The deviation of power and operating costs in both scenarios defines the system's flexibility and flexibility invocation cost, respectively. This framework holds broad applicability across various aggregation platforms and can measure flexibility across different time scales by adjusting the control interval of the day-ahead dispatch optimization model. Finally, the framework is validated through case studies, revealing the impact characteristics of system type and capacity on flexibility, and analyzing the sensitivity of flexibility to various uncertainty parameters.

Investigating the influence of coarse aggregate characteristics and fiber dispersion on the flexural performance of ultra-high performance concrete (UHPC)

The flexural properties of ultra-high performance concrete containing coarse aggregate (UHPC-CA) strongly depend on the characteristics of coarse aggregates and the dispersion of fibers. However, the impact of the interaction between coarse aggregate and steel fibers on the bending performance of UHPC-CA is not well-understood. This study investigated the four-point bending properties of UHPC-CA to clarify the influence of coarse aggregates. Mechanical tests, laser scanning confocal microscopy (LSCM), scanning electron microscopy (SEM), and image analysis were performed to investigate the impact of coarse aggregate on flexural properties, considering coarse aggregate properties, and steel fiber dispersion. The results indicate that coarse aggregates affect both bending strength and toughness. The type of coarse aggregate primarily influences bending strength, while the quantity of coarse aggregate determines toughness. The peak strength is closely related to the strength of the parent rock, whereas toughness is significantly affected by fiber dispersion. Coarse aggregate can adversely impact toughness by their inherent brittleness and worsening the fiber dispersion within the matrix. Additionally, this paper provides parameters for selecting suitable coarse aggregate for UHPC. It is recommended that coarse aggregate added to UHPC possess a strength approximately 1.5 times that of the matrix, with a particle size not exceeding 10 mm and a content below 30 %.

Bond-Slip Constitutive Relationship between Steel Rebar and Concrete Synthesized from Solid Waste Coal Gasification Slag

Bond performance served as a crucial foundation for the collaboration between concrete and steel rebar. This study investigated the bond performance between coal gasification slag (CGS) concrete, an environmentally friendly construction material, and steel rebar. The effects of fine aggregate type, steel rebar diameter, and anchorage length on bond performance were examined through bond-slip tests conducted on 16 groups of reinforced concrete specimens with different parameters. By utilizing experimental data, a formula for the bond strength between steel rebar and CGS concrete was derived. Additionally, the BPE bond-slip constitutive model was modified by introducing a correction factor (k) to account for relative protective layer thickness. Findings indicated that substituting 25% of manufactured sand with coal gasification slag did not cause significant adverse effects on concrete strength or bond stress between concrete and steel rebar. The effect of steel rebar diameter on the ultimate bond stress was not obvious, whereas when the steel rebar diameter was fixed; the increase in anchorage length led to uneven distribution of bond stress and eventually reduced the ultimate bond stress. The modified bond-slip constitutive model agreed well with the experimental values and was able to more accurately reflect the bond-slip performance between CGS concrete and steel rebar. This study provided a theoretical basis for the conversion of CGS into a resource and for the application of CGS concrete.