Particle Packing Model Research Articles

A Review of Particle Packing Models and Their Applications to Characterize Properties of Sand-Silt Mixtures

This paper reviews particle packing models and explores their application in geotechnical engineering, specifically for sand-silt mixtures. The review covers key models, including limiting case, linear, and non-linear packing models, focusing on their mathematical structures, physical principles, assumptions, and limitations through the concept of excess free volume. The application of particle packing models in geotechnical engineering is explored in characterizing the properties of sand-silt mixtures, offering insights into maximum, minimum, and critical void ratios and inter-granular void ratio, and the prediction of mechanical properties.

Approaches for predicting the soil-water characteristic curves of compacted quartz sand based on particle packing theory

The soil-water characteristic curve (SWCC) is an important basis for describing hydraulic properties, which is closely related to environmental problems such as the migration of toxic substances from groundwater and soil. The SWCC models vary considerably with respect to the void ratio or bulk density. However, the void ratio and bulk density of the same soil change at different depths or positions within a flat space. Accurate simulation or calculation requires a precise SWCC, but measuring every SWCC under each density or void ratio condition is difficult. In this study, two particle packing models, the Kwan model and the modified linear packing density model (MLPDM), were introduced into the van Genuchten (VG) model to predict the SWCC for soil at the minimum void ratio (the maximum dry density). Then, the prediction method of the SWCCs for the same soil with different densities or void ratios was given. A series of laboratory tests using quartz sand mixtures were conducted to verify the accuracy of two extended models (the K-VG model and the M-VG model). For the K-VG model, the average RMSE was 0.020. For the M-VG model, the average RMSE was 0.017. In general, the SWCCs predicted by the two extended models were consistent with the measured values.

Development and Characterization of Basalt Fiber-Reinforced Green Concrete Utilizing Coconut Shell Aggregates

Lightweight aggregate concrete (LWAC) is gaining interest due to its reduced weight, high strength, and durability while being cost-effective. This research proposes a method to design an LWAC by integrating coconut shell (CS) as coarse lightweight aggregate and a high volume of wet-grinded ultrafine ground granulated blast furnace slag (UGGBS). To optimize the mix design of LWAC, a particle packing model was employed. A comparative analysis was conducted between normal-weight concrete (M40) and the optimized LWAC reinforced with basalt fibers (BF). The parameters analyzed include CO2 emissions, density, surface crack conditions, water absorption and porosity, sorptivity, and compressive and flexural strength. The optimal design was determined using the packing density method. Also, the impact of BF was investigated at varying levels (0%, 0.15%, and 1%). The results revealed that the incorporation of UGGBS had a substantial enhancement to the mechanical properties of LWAC when BF and CS were incorporated. As a significant finding of this research, a grade 30 LWAC with demolded density of 1864 kg/m3 containing only 284 kg/m3 cement was developed. The LWAC with high-volume UGGBS and BF had the minimum CO2 emissions at 390.9 kg/t, marking a reduction of about 31.6% compared to conventional M40-grade concrete. This research presents an introductory approach to sustainable, environmentally friendly, high-strength, and low-density concrete production by using packing density optimization, thereby contributing to both environmental conservation and structural outcomes.

Optimal formulation and performance evaluation of functional ultra-high performance concrete with barium ferrite

The employment of a core catcher is instrumental in enhancing the safety of nuclear power facilities in the event of severe accidents, with sacrificial materials serving as fundamental constituents. Currently, cement-based sacrificial materials are prevalently utilized due to their straightforward construction methodologies and economical production costs. These materials are designed to withstand significant impact loads arising from the descent of core melt during severe accidents. To augment the impact resilience of sacrificial materials, a novel functional ultra-high performance concrete (FUHPC) incorporating barium ferrite has been developed. Using the Modified Andreasen and Andersen particle packing model to determine the initial mixture of FUHPC, and the impact of barium ferrite on the mechanical and thermal properties of FUHPC was systematically evaluated. Furthermore, the influence of barium ferrite on the FUHPC's microstructure was examined with mercury intrusion porosity and scanning electron microscopy techniques. The findings indicate: (1) Optimal barium ferrite incorporation led to a decrease in the porosity and the threshold pore diameter of FUHPC; (2) The flexural and compressive strengths, as well as the elastic modulus of FUHPC, were found to increase within the ranges of 4.41%–17.50 %, 2.88%–22.91 %, and 5.80%–15.06 %, respectively, as a result of suitable barium ferrite additions; (3) At a barium ferrite concentration of 2 vol%, the chloride migration coefficient of FUHPC was reduced by 21.43 %; (4) The presence of barium ferrite enhanced the impact performance of FUHPC, with a 21.38 % increase in impact resistance noted at a barium ferrite content of 2 vol%; (5) In high-temperature scenarios, the formation of channels from melted polypropylene fibers served to mitigate the spalling of FUHPC; (6) Upon considering the effects of barium ferrite on both room temperature and elevated temperature performance, as well as on microstructural characteristics, the optimal barium ferrite content was determined to be 2 vol%.

Prediction of Aggregate Packing with Tubular Macrocapsules in the Inert Structure of Self-Healing Concrete Based on Dewar's Particle Packing Model.

This paper brings a new insight into understanding the influence of macrocapsules in packing systems, which can be useful in designing the inert structure of self-healing concrete. A variety of tubular macrocapsules, in terms of types and sizes, was used to assess the capsules' effect in the packing, together with various aggregate types and fractions. The voids ratios (U) of aggregate mixtures were evaluated experimentally and compared with the prediction via the particle packing model of Dewar. The packing of coarse particles was found to be considerably affected by the presence of macrocapsules, while no capsules' effect on the packing of fine particles was attained. A higher capsule dosage and capsule aspect ratio led to a higher voids ratio. In the formulation of the inert structure, the packing disturbance due to capsules can be minimised by increasing the content of fine aggregates over coarse aggregates. Dewar's model showed a good compatibility with experimental results in the absence of capsules. However, the model needed to be upgraded for the introduction of tubular macrocapsules. Accordingly, the effect of macrocapsules was extensively analysed and a 'U model' for capsules (with some limitations) was finally proposed, offering a high predicting accuracy.

Quaternary blended eco high performance concrete utilizing high volumes of siliceous additives

This research examines the optimal feasibility of incorporating siliceous additives as an adjunct material for cement in the formulation of environmentally sustainable high-performance concrete (Eco-HPC). Siliceous materials, including Nano silica (NS), Rice Husk Ash (RHA), and Fly Ash (FA), were fine-tuned within the cementitious system in order to achieve the amplified performance of Eco-HPC by reducing the required cement content from 370 kg/m3 to 273 kg/m3. This is achieved by employing the Modified Andreasen and Andreasen (MA&A) particle packing model, with ‘q’ (distribution factor) as ‘0.3’. The Levenberg Marquardt algorithm (curve fitting) was utilized to validate the packing density of each concrete blends. Initially, the dry NS agglomerates are synthesized into stabilized aqueous dispersion through High shear mixing (10 min/1750 rpm) followed by probe sonication (15 min/(1/3) s/s) with anionic surfactant dosage of 0.1 g/10 g. Incorporating secondary siliceous binders into the cement matrix led to an enhancement in the packing density, increasing from 0.94 (nullary) to 0.96 (quaternary) which in turn alters the reactivity and cohesiveness of the matrix. Compressive strength values for Binary (NS2), Ternary (RN15, FN20), and quaternary mix (FRN25) were observed as 57.42 MPa, 56.83 MPa, 55.34 MPa, and 52.58 MPa, respectively, for primary binder contents of 362 kg/m3, 314 kg/m3, 296 kg/m3, and 273 kg/m3 without compromising durability parameters. An assessment on reduced carbon dioxide emissions indicated that increasing the cement replacement percentages in Eco-HPC by up to 30% for binder contents of 358 kg/m3, 296 kg/m3, 259 kg/m3, and 273 kg/m3 resulted in a reduction of CO2 emissions by 2.98%, 18%, 27%, and 23.33%, respectively. Among the twelve formulated mixes, FRN25, FRN20, FRN15 and FN30 are identified as Eco-HPC mix through a computational framework which integrates the packing density, carbon emission, strength and diffusion coefficient.

Evaluating 3-parameter packing model with discrete element modeling

Accurate prediction of particle packing density remains challenging. Herein, the particle packing is simulated by discrete element modeling and the packing density results are used to evaluate the 3-parameter particle packing model. When the 3-parameter model is applied to binary and ternary blended mixes, the mean absolute errors in packing density prediction are 0.96% and 1.37%, respectively. Overall, the accuracy of the 3-parameter model is very good when applied to binary blends but not as good when applied to ternary blends, especially when the intermediate size particles are dominant. The discrete element modeling reveals that even when the intermediate size particles are dominant, there are significant particle interactions between the smaller size and larger size particles, which have not been properly accounted for in the existing packing models. Hence, there is still room for improving the existing packing models, requiring further discrete element modeling to study particle interactions.

Effect of Iron Ore and Copper Ore Tailings on Engineering Properties and Hydration Products of Sustainable Cement Mortar

Abstract The prohibition of river sand mining has drawn the attention of researchers in finding practicable alternatives. In the approach of finding these alternatives, it is essential to ensure minimal or zero impairment to the ecological balance, which can be mainly attained by making use of industrial waste/byproducts. The wastes from the mining industry are the major contributors in causing impairment to the environment, and their influence on the stability of mortars on using as fine aggregates needs to be systematically investigated with the view of long-term performance concerns. Thus, the present study explores the applicability of mine tailings and finding the optimum dosage in cement mortars by investigating the engineering properties and microstructure development with the aid of qualitative and quantitative analysis associated with hydration products. The studies confirm that the increased consumption of portlandite for secondary hydration reactions followed by the additional formation of calcium silicate hydrate (CSH) and calcium aluminum silicate hydrate (CASH) phases in mine tailing-based mortars helped in achieving a quality microstructure. These additional formations of CSH and CASH phases are also confirmed through Fourier transform infrared spectroscopy by identifying the shift of Si-O-Si stretching vibration bands toward a lower wavenumber. The lowering of calcium/silicate atomic ratio and increased formation of mineralogical compounds related to CSH and CASH in x-ray diffraction patterns also confirms the same. Gismondine, chabazite, and hillebrandite are the additional phases formed and found to take part in refining the pore structure. This enhanced performance of mine tailing mortars was also verified with the aid of a modified Andreasen and Andersen particle packing model. The formation of high-quality microstructure is reflected in the hardened properties of optimized cement mortar in the proportion of 20 % for iron ore tailing and 30 % for copper ore tailing.

Modeling of the heterogeneous hypergolic ignition with particle packing model

The ignition process of a hypergolic hybrid rocket fuel presents a significant challenge due to its complex and interconnected nature. However, understanding its underlying physics is crucial for accurately estimating the delay time and ignition performance. In this study, we employed an approximate analytical method to directly address the transient conduction problem with nonlinear surface heat generation. By using the Arrhenius equation and considering dual heat flux directions in both the liquid and solid domains, we propose a model for determining the delay time of heterogeneous hypergolic ignition. Our solution is straightforward and computationally efficient. Notably, when subjected to identical initial conditions and property settings, our results exhibit similarity with the solutions derived from other models. Moreover, we advance our approach by developing a particle packing model through the utilization of a well-established algorithm. By simulating the particle arrangement within the pellet, the surface layer properties and the thermal time constant of certain fuel designs can be modeled. This simulation serves the purpose of incorporating the particle size effect of the fuel pellet into our ignition model. The results generated by our heterogeneous hypergolic ignition model, in conjunction with the particle packing model, demonstrated impressive agreement with the experimental data derived from droplet tests. Novelty and significance statementThis study utilized a novel solving method to address a transient conduction problem with non-linear heat generation on the surface during a heterogeneous hypergolic ignition process. The study successfully derived an analytical solution, providing a simpler method for calculating ignition delay times. A scenario involving different initial temperatures was also examined. Additionally, the research integrated particle packing model data and thermal time constants to assess the effect of particle size. The model results were in agreement with the experimental data, confirming its accuracy and offering a reliable method for estimating the heterogeneous hypergolic ignition delay time.

Development of low carbon engineered cementitious composite (ECC) using nano lime calcined clay cement (nLC3) based matrix

The construction industry is responsible for around 5% of total CO2 emissions globally. As a result, recent research is focused on the sustainability aspects of construction materials. Engineered cementitious Composites (ECC) are high-performance fiber reinforced composites with improved ductility and tensile strength but utilize higher cement content, raising concerns about their sustainability. In this study, nano-lime and calcined clay are combined with cement to develop a high strength sustainable nano lime calcined clay cement (nLC3) based Engineered Cementitious Composite (ECC). Initially, the packing density model was employed to develop a high strength nLC3-based matrix by combining the particle packing models and chemical compatibility while keeping costs to a minimum. Micromechanical modeling was then applied to determine the critical volume of fibers for the novel matrix using single fiber pullout tests and matrix toughness tests. According to the micromechanical model, the critical volume fraction is found to be 1.93% for the nLC3 mix. This was further confirmed by casting dog bone samples containing 2% fibers by volume which confirmed strain hardening response. The uniaxial test results indicated a strength of around 5.85 MPa in tension and 51 MPa in compression with about 3% tensile strain. These results are comparable to conventional ECC and better than previously developed LC3 based ECC. This study reveals that nLC3-based ECC is a more sustainable composite as compared to conventional ECC mix without any compromise on strength and cost.

Modified particle packing approach for optimizing waste marble powder as a cement substitute in high-performance concrete

This study explores the potential of utilizing waste marble powder (WMP) instead of cement to develop environmentally friendly high-performance concrete (Eco-HPC). It assesses Eco-HPC's particle packing density, workability, mechanical characteristics, and durability at various stages. High-performance concrete (HPC) mixtures were optimized using a Modified Andreasen and Andersen (MAA) particle packing model to minimize cement content from 550 to 385 kg/m3. The MAA particle packing model demonstrated its ability to enhance and refine mixture microstructures. Response Surface Methodology (RSM) and Artificial Neural Networks (ANN) were employed to optimize and predict the mechanical properties and water absorption of modified Eco-HPC blends at 7, 28, and 56 days. As the coefficient of determination indicates, ANN outperformed RSM in predicting Eco-HPC properties across various ages. Substituting cement with WMP, Silica Fume (SF), and Fly Ash (FA) results in a dense microstructure. The mortar containing 20 % WMP and 10 % SF achieves the highest wet packing density at 0.9749 and the lowest void ratio at 0.025, respectively. The formation of CSH in the 70C/20 M−10SF mixture led to a substantial reduction in calcium hydroxide content, indicating enhanced mechanical properties. SEM analysis at 56 days demonstrated significant pozzolanic reactions in the 70C/20 M−10SF mixture, resulting in substantial CSH formation. Furthermore, the embodied CO2 index for 70C/20 M−10SF was reduced to 5.07 kg/MPa/m3, compared to the 100C/0M with value of 8.17 kg/MPa/m3. Economic and environmental assessments reveal enhanced mechanical properties and microstructure when using WMP. This evaluation confirms the effectiveness of 70C/20 M−10SF utilization, paving the way for further advancements in Eco-HPC development.

Predicting concrete strength through packing density using machine learning models

This study presents an innovative approach to predict concrete compressive strength using particle packing theories through machine learning techniques. The existing challenge in concrete engineering lies in the accurate estimation of concrete strength, a critical factor in construction. The adoption of particle packing theories, which hold great promise for enhancing concrete performance, has been limited due to the complexity and time-consuming nature of the required calculations. An approach encompassing particle packing models (JD Dewar Model, Compressible Packing Model, and Modified Toufar Model) with machine learning is the novelty of the work. These models optimize the packing density of aggregate proportions while minimizing the void ratio, essential for achieving desired compressive strength criteria. To train the model, a comprehensive dataset comprising 479 concrete mixtures, each associated with known compressive strength values relative to packing density, is utilized. A significant advancement in predicting concrete compressive strength is demonstrated by the results. The approach outperforms traditional empirical models, offering precise and reliable predictions based on packing density. Importantly, this innovation eliminates the need for time-consuming and costly trial-and-error procedures in concrete mix design. The strong performance of various models in predicting concrete strength using particle packing theories is underscored by the study, with R^2 values ranging from 0.664 to 0.999. By combining concepts of particle packing theories and machine learning, a more efficient and reliable method for predicting concrete compressive strength is achieved. This innovation has the potential to revolutionize concrete mix design, leading to more durable and cost-effective construction practices.

Study on the mechanical properties and prediction model of ultra-high performance concrete containing aeolian sand and recycled mixed powder

This paper addresses the feasibility of the synergistic preparation of ultra-high performance concrete (UHPC) with recycled mixed powder (RMP) and aeolian sand (AS). In this paper, UHPC was prepared by replacing cement (0, 10%, 20%) and river sand (RS) (0, 15%, 30%, 45%) with RMP and AS (by mass). The optimized mix design of UHPC was based on the Modified Andreasen & Andersen particle packing model. The compressive, flexural, and splitting tensile strengths of different formulations of UHPC were tested. The results show that RMP and AS have a synergistic effect on the strength improvement of UHPC. When the content of RMP is 10% and the content of AS is 30%, the compressive, flexural, and splitting tensile strengths of UHPC are 131.85 MPa, 18.46 MPa, and 11.81 MPa, respectively, which increase with the largest improvement by 9.56%, 8.91%, and 8.25%, compared with the control group. The ultra-fine particles (VFP) (<175 μm) in AS adequately fill the pores generated by larger RS particles, and the void fraction of fine aggregate (FA) is minimized when the AS content is 30%. Moreover, a compressive strength model based on the pozzolanic activity effect was established. Finally, by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses, it is found that RMP and AS can not only promote hydration nucleation and improve the hydration rate of cement, but also enhance the adhesion and occlusal force between the matrix and aggregate and improve the microstructure of the matrix and interfacial transition zone (ITZ). The results of this paper have reference value for the eco-friendly development of UHPC.

Graphical user interface (GUI) for gradation of aggregate in pervious concrete pavements based on particle packing approach

ABSTRACT Pervious concrete, a unique type of concrete utilised in pavement construction, plays a crucial role in addressing environmental concerns like groundwater recharge and stormwater runoff. This concrete variant eliminates most or all fines in the mix, creating interconnected void spaces that facilitate the percolation of water at higher rates. The goal is to strike a balance between porosity, strength and permeability, ensuring the pavement to withstand loads while effectively managing water flow. In this study, it is attempted to develop aggregate gradation for the desired percolation rates of concrete matrix using two Particle Packing Models (PPM), viz. Compressible Packing Model (CPM) and Modified Taufer Model (MTM). The results of PPM are compared with IRC 15:2017 aggregate grading specifications. This study is also extended to determine compressive and flexural strengths for different porosities of aggregate system and w/c ratios using the relations established from the literature. For a pervious concretes with a constant water-to-cement (w/c) ratio of 0.50 and an aggregate packing density of 0.7 for Pavement Quality Concrete (PQC), it was observed that with increase in porosity from 15% to 25%, the compressive strength decreased by 40.66% and the flexural strength decreased by 22.96%. A Graphical User interface (GUI) is developed for the gradation of aggregates to simply the process of proportioning through experimentation.

Mechanical grinding kinetics and particle packing novel characterization of iron ore tailings as inert filler for cement mortar

This study utilized image processing techniques to extract the morphological parameters of IOTs and established a grinding kinetic equation for particle morphology. The Divas-Aliavden equation and RRB model were applied to analyze the grinding kinetics of particle physical parameters. The Fuller and MAA particle packing models were employed to discuss the packing structure and density of particles in mortar. The relationship between particle physical parameters and compressive strength in the IOTs-cement system was explored through path analysis and grey correlation analysis. The results indicated that as the grinding process of IOTs progressed, the particle fineness decreased, the uniformity of particle size distribution and roundness increased, and using IOTs as inert fillers in mortar improved the particle packing structure and increased system density. Path analysis revealed the key influence of particle roundness on compressive strength, while the grey correlation analysis revealed that particles in the 2–60 μm range exerted a positive impact on the compressive strength of the composite binder system, with the most pronounced effect observed within the 8–16 μm range. Based on economic and technical considerations, the optimal mechanical grinding time for IOTs used as inert filler in cement mortar was determined to be 2.5 h.

Influence of the fine aggregate particle packing effects on the paste rheological thresholds of self-compacting concrete

The paste rheological threshold theory could guide the prediction of the self-compacting concrete (SCC) performance from the paste mini-slump flow test. The prediction process was simplified, but the prediction did not consider the influence that the fine aggregate caused enough, possibly leading to a wrong mix design when the fine aggregate changed. To solve this issue, this study focused on the effect of the fine aggregate particle packing effects on the paste threshold. Based on the 3-parameter particle packing model, a fine aggregate packing parameter that can describe the fine aggregate particle packing effects more accurately was proposed to replace the original one, which considered only the particle size. Thus, the threshold calculation formulas were modified. To verify the modification, a total of five series of paste and SCC tests with different material compositions were conducted. Based on the bilinear interpolation method, the self-compacting paste zones (SCP zone) were obtained by original and modified thresholds. Through the comparison of SCP and SCC zones, the prediction accuracy of the proposed modification was evaluated by a certain evaluation method. The overlap area and relative position of the self-compacting zones were evaluated by the relative accuracy index Δε and the modification accuracy index Δ|ε’-1|, respectively. Through the modification of the paste thresholds, the overlap area of the modified SCP and SCC zones changed little. But the relative position of the modified SCP zone was closer to the SCC zone than the original SCP zone. The modified SCP zone showed more accuracy in prediction summarily. The proposed modification embodied the influence that the fine aggregate packing properties caused, expanding the description of fine aggregate particle packing effects in the paste threshold theory.

A nonlinear particle packing model for micro-aggregate

The nonlinear packing model for micro-aggregate was constructed to predict the actual packing density of micro-aggregate based on the nonlinear packing model for granular soil. The characteristics, differences and applications of five common calculation models of packing density were discussed. The correlation coefficients of the particle packing model based on granular soil were modified to derive packing density relationship for the micro-aggregates. The average relative error of the measured results is less than 0.4% and the root mean square error is within 3.2 × 10−3, which means the validity of the derived relationship is verified.

Recycling of steel slag powder in green ultra-high strength concrete (UHSC) mortar at various curing conditions

The large quantity of steel slag deposit has caused great environmental pressure. This study aims to recycle steel slag as binder in the production of green ultra-high strength concrete (UHSC) subjected to different curing regimes (i.e. standard and steam curing). The fresh behaviors, mechanical properties, microstructure and ecological value of the UHSC are explicitly assessed with the help of the Funk and Dinger particle packing model. The results show that the inclusion of steel slag powder (SSP) increases the workability (up to about 13%) and wet packing density of UHSC. The use of SSP results in a decrease of early compressive strength, because the SSP inhibits cement hydration at early stage. The steam curing can minimize this negative impact of SSP on the early compressive strength (>120 MPa). Besides, the increase of SSP dosage results in a reduction in the flexural strength for both early and later ages, but steam curing reduces the decline ratio. The high temperature curing not only promotes the hydration process of both cement and SSP, but also accelerates the pozzolanic reaction of silica fume, resulting in a lower porosity (4.78%) of UHSC with SSP. Finally, the ecological assessment shows that the recycling SSP as a replacement of cement in the UHSC system can reduce energy consumption and carbon emissions. Therefore, the results in this study indicate the feasibility of utilizing SSP in the fabrication of sustainable UHSC products with excellent performance.

Feasibility of producing ultra-high performance concrete with high elastic modulus by steel chips: An experimental study

Elastic modulus is one of the key parameters to weigh the stiffness of concrete members and structural design in civil engineering. Despite its excellent performance in durability and mechanical properties, ultra-high performance concrete (UHPC) is featured with relatively low elastic modulus, which prevents UHPC from being applied in a much larger scope. This study was conducted to explore the feasibility of preparing UHPC with high elastic modulus (HMUHPC) by using steel chips. The modified Andreasen and Andersen (MAA) particle packing model was used to design the initial mixture of HMUHPC. Based on this, some steps were followed to investigate the impacts of varying contents of steel chips on HMUHPC with regard to its mechanical properties, workability, and apparent density. In addition, attention was also paid to how steel chips affected the microstructure of HMUHPC and the ultrasonic pulse velocity (UPV) propagated in HMUHPC. It was found that: 1) Due to the addition of steel chips, there was an increase from 9.65% to 21.73%, 6.38% to 15.85%, 1.28% to 10.49%, and 3.11% to 16.44%, respectively, in the elastic modulus, compressive strength, flexural strength, and apparent density of HMUHPC; 2) The addition of steel chips could reduce the porosity of HMUHPC and optimize its pore size distribution; 3) Considering the effects of steel chips on HMUHPC regarding its microstructure, mechanical properties, and workability, the optimal content of steel chips in HMUHPC was 50 wt%.

Design Procedures for Sustainable Structural Concretes Using Wastes and Industrial By-Products

The protection of the environment must be a priority in our society, and the construction sector can contribute significantly to this goal. Construction, being one of the industrial sectors that is more demanding in terms of raw materials, must reinforce its effort to implement, in a more profound and systematic way, the paradigm of the circular economy. In this sense, in recent years several studies have been trying to contribute solutions aimed at reintroducing industrial by-products or residues in new products for the construction industry. It should be noted that nowadays it is increasingly important to introduce a higher percentage of recycled materials in concrete. In this context, the present work addresses the appropriateness of a design procedure proposed to maximize the content of electric arc furnace slag (EAFS) and include recycled tire steel fibers (RTSF) in the production of more sustainable structural concretes. For this, the properties of various concrete mixtures at the fresh and hardened state, obtained by the substantial substitution of coarse and fine natural aggregates by EAFS and fly ash (FA), were investigated. The design of EAFS mixtures was based on two conventional reference mixtures (REF1 and REF2), and by using the modified Andreasen and Andersen particle packing model, these were optimized to achieve maximum packing density. Compressive strength, modulus of elasticity behavior, and fresh and physical properties were assessed in order to define the best mix proportions with respect to the predefined requirements of ordinary mixtures. Untreated recycled tire steel fibers (RTSF) were included in the developed sustainable concrete to perform a comparison of the physical properties with unreinforced concretes developed with natural aggregates (REF2) and with EAFS aggregates (EAFS8D1). This incorporation was intended to improve the physical behavior of unreinforced concretes with EAFS aggregates. Mixtures with high percentages of waste aggregates up to 70% (in weight), and 10% (in weight) of FA were obtained, showing competitive mechanical behavior compared to REF1 and REF2. These concrete compositions showed minimum and maximum compressive strengths between 9 MPa and 37 MPa, respectively. This study coverd the two major classes of concrete used as structural material, namely structural concrete and fiber reinforced concrete.